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NCEA LEVEL 3 BIOLOGY EXTERNALS Meet the writing team

Tracey

Senior Author

Kent

Tracey Greenwood I have been writing resources for students since 1993. I have a Ph.D in biology, specialising in lake ecology and I have taught both graduate and undergraduate biology. Kent Pryor I have a BSc from Massey University majoring in zoology and ecology and taught secondary school biology and chemistry for 9 years before joining BIOZONE as an author in 2009.

Author

Lissa Bainbridge-Smith I worked in industry in a research and development capacity for 8 years before joining BIOZONE in 2006. I have a M.Sc from Waikato University. Lissa Author

Cover photograph Australopithecus afarensis A. afarensis, the famously named "Lucy", is one of the longest-lived and bestknown hominins, with fossils from more than 300 individuals. Dated at 3.85-2.95 million years, this east African species survived for more than 900,000 years, more than four times as long as our own species has been around. PHOTO: kenniskennis.com

Richard Allan I have had 11 years experience teaching senior secondary school biology. I have a Masters degree in biology and founded BIOZONE in the 1980s after developing resources for my own students. Richard

Founder & CEO

Thanks to: The staff at BIOZONE, including Nell Travaglia and Holly Coon for design and graphics support, Paolo Curray and Malaki Toleafoa for IT support, Debbie Antoniadis and Arahi Hippolite for office handling and logistics, and the BIOZONE sales team. Previous annual editions 1988-2014 Second edition 2016

ISBN: 978-1-927309-56-8 Copyright Š 2016 Richard Allan Published by BIOZONE International Ltd Printed by Wickcliffe Solutions www.wickliffe.co.nz

Purchases of this book may be made direct from the publisher:

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All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electrical, mechanical, photocopying, recording or otherwise, without the permission of BIOZONE International Ltd. This book may not be re-sold. The conditions of sale specifically prohibit the photocopying of exercises, worksheets, and diagrams from this book for any reason.


Contents Using This Resource ............................................... v Using the Tab System ............................................ vii How To Scaffold an NCEA Style Answer .............. viii

AS 3.3 Plant and animal responses to their external environment 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

CODES:

Achievement criteria and explanatory notes ...... 1 Why Organisms Need to Respond...................... 3 Types of Stimuli.................................................... 4 Kineses................................................................ 5 Taxes.................................................................... 7 Pheromones......................................................... 9 Migration............................................................ 10 Migration Patterns ............................................. 11 Examples of Migration ...................................... 12 Bird Migrations in New Zealand ........................ 14 Migratory Navigation in Birds............................. 15 Cuckoo Migrations ............................................ 17 Sun Compass Navigation.................................. 18 Homing Behaviour in Insects ............................ 20 Homing in Salmon ............................................. 21 Plant Responses ............................................... 22 Tropisms ............................................................ 23 Investigating Phototropism ................................ 24 Investigating Gravitropism ................................. 25 Investigating Gravitropism in Seeds .................. 26 Nastic Responses ............................................. 27 What You Know So Far...................................... 29 NCEA Style Question: Migration ....................... 30 NCEA Style Question: Plant Responses ........... 31 KEY TERMS AND IDEAS .................................. 32 Astronomical Cycles.......................................... 33 Biological Clocks ............................................... 34 Biological Clocks and the Environment ............. 35 Biological Rhythms ........................................... 36 Circadian Rhythms in NZ Birds ......................... 38 Human Biological Rhythms ............................... 39 Interpreting Actograms ..................................... 41 Activity Patterns in Animals ............................... 42 Plant Rhythms ................................................... 44 Photoperiodism in Plants .................................. 46 What You Know So Far...................................... 48 NCEA Style Question: Biological Clocks in Animals ......................................................... 49 NCEA Style Question: Biological Clocks in Plants ............................................................ 50 KEY TERMS AND IDEAS................................  .. 51 Species Interactions .......................................... 52 Mutualism involving Animals ............................. 54 Mutualism involving Plants ................................ 56 Interpreting Predator-Prey Relationships .......... 58 The Effects of Interspecific Competition ........... 59

Activity is marked:

to be done

44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74

Identifying Species Interactions in Ecosystems .. 61 What You Know So Far....................................... 62 NCEA Style Question: Interspecific Relationships ................................ 63 KEY TERMS AND IDEAS ................................. 64 Intraspecific Communication ............................. 65 Pukeko Communication .................................... 67 Recording Animal Behaviour ............................ 68 Social Groupings ............................................... 69 Social Organisation ........................................... 70 Cooperative Behaviour ...................................... 71 How Cooperative Behaviour Improves Survival . 73 Cooperative Defence ........................................ 75 Cooperative Attack ............................................ 76 Cooperative Foraging ........................................ 77 Conflict in Social Groups ................................... 78 Intraspecific Competition and its Effects ........... 80 Social Hierarchy in Pukekos ............................. 82 Monkey Hierarchy ............................................. 84 Hierarchies in Baboons ..................................... 85 Territories and Home Ranges ........................... 86 Home Ranges and Resources in Baboons ....... 87 Home Ranges in Karearea ............................... 88 Yellowhead Territories ....................................... 89 Breeding Behaviour .......................................... 90 Reproductive Strategies..................................... 92 Mating Systems and Parental Care .................. 94 Territories and Breeding Behaviour ................... 95 What You Know So Far...................................... 96 NCEA Style Question: Cooperative Behaviour.. 97 NCEA Style Question: Territories ...................... 99 KEY TERMS AND IDEAS ............................... 100

AS 3.5 Evolutionary processes leading to speciation

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90

Achievement criteria and explanatory notes .... 101 The Role of Variation in Populations ............... 103 Mutations ........................................................ 104 Beneficial Mutations ........................................ 105 Sickle Cell Mutation ........................................ 106 Heterozygous Advantage ................................ 107 Gene Duplication and Evolution ...................... 109 An Introduction to Evolutionary Processes...... 111 Genetic Drift Affects Gene Pools .................... 113 Adaptations and Fitness ................................. 114 Natural Selection Affects Gene Pools ............. 115 Stabilising Selection for Human Birth Weight .. . 116 Directional Selection in Moths ......................... 117 Directional Selection in Darwin's Finches ....... 118 Disruptive Selection in Darwin's Finches ........ 119 Selection for Skin Colour in Humans .............. 120 What You Know So Far ................................... 122

when completed


Contents

91 NCEA Style Question: Mutation and Evolution... 123 92 KEY TERMS AND IDEAS................................ 124 93 The Biological Species Concept...................... 125 94 What Are Ring Species?.................................. 126 95 Ring Species: The Greenish Warbler............... 127 96 Prezygotic Reproductive Isolating Mechanisms. 128 97 Postzygotic Reproductive Isolating Mechanisms. 131 98 Allopatric Speciation......................................... 132 99 Small Flies and Giant Buttercups..................... 134 100 Divergence in Allopatric Populations................ 135 101 Polyploidy as a Source of Variation.................. 136 102 Sympatric Speciation....................................... 138 103 Polyploidy and Speciation in Melicytus............. 139 104 Polyploidy and the Domestication of Wheat..... 140 105 What You Know So Far.................................... 142 106 NCEA Style Question: Speciation.................... 143 107 KEY TERMS AND IDEAS................................ 144 108 Divergent Evolution......................................... 145 109 Convergent Evolution....................................... 146 110 Coevolution...................................................... 148 111 Adaptive Radiation in Mammals...................... 150 112 Adaptive Radiation in Ratites........................... 152 113 The Rate of Evolutionary Change.................... 154 114 The Geological History of New Zealand.......... 155 115 Changes in Landscape and Speciation........... 156 116 Speciation in Giant Land Snails....................... 158 117 Origin of New Zealand Parrots......................... 160 118 Adaptive Radiation in Wrens............................ 162 119 Evolution in Hebe............................................. 164 120 What You Know So Far.................................... 165 121 NCEA Style Question: Patterns of Evolution.... 166 122 KEY TERMS AND IDEAS................................ 167 123 The Evidence for Evolution.............................. 168 124 The Common Ancestry of Life......................... 169 125 Fossils.............................................................. 171 126 Interpreting the Fossil Record.......................... 173 127 Transitional Fossils........................................... 175 128 The Evolution of Horses................................... 176 129 The Evolution of Whales.................................. 177 130 Biogeographical Evidence............................... 178 131 Ocean Island Colonisers.................................. 179 132 Continental Drift and Evolution......................... 181 133 Homologous Structures................................... 185 134 Vestigial Structures.......................................... 186 135 Homologous Proteins....................................... 187 136 Molecular Clock Hypothesis............................. 189 137 Homologous DNA Sequences......................... 190 138 Developmental Evidence for Evolution............. 191 139 The Evolution of Novel Forms.......................... 192 140 What You Know So Far...................................... 193 141 NCEA Style Question: Evidence for Evolution .. 194 142 KEY TERMS AND IDEAS................................ 195

CODES:

Activity is marked:

to be done

AS 3.6 Trends in human evolution

Achievement criteria and explanatory notes .... 196 143 General Primate Characteristics ...................... 198 144 Hominins and Hominoids ................................. 200 145 The Primate Hand ............................................ 201 146 Primate Skull Features ..................................... 202 147 Human Skull Anatomy ..................................... 203 148 Trends in Human Evolution: Overview ............. 204 149 Human Evolution: Probable Phylogenies ......... 206 150 Trends in Skull Anatomy .................................. 208 151 Trends in Brain Volume .................................... 210 152 Trends in Dentition ........................................... 212 153 The Importance of Ardi .................................... 213 154 Bipedalism and Nakedness ............................. 215 155 Adaptations for Bipedalism .............................. 216 156 Analysis of Lucy's Skeleton .............................. 218 157 Hominin Data Sheets ....................................... 219 158 What You Know So Far .................................... 227 159 NCEA Style Question: Biological Evolution ...... 228 160 KEY TERMS AND IDEAS................................. 229 161 Cultural Evolution.............................................. 230 162 Trends in Palaeolithic Tool Cultures.................. 232 163 Palaeolithic Tool Use......................................... 234 164 Fire ................................................................... 235 165 Shelter and Clothing ........................................ 236 166 Art and Spirituality............................................. 237 167 Communication and Changes in the Brain....... 239 168 Mesolithic Culture............................................. 240 169 Neolithic Culture................................................ 241 170 What You Know So Far..................................... 243 171 NCEA Style Question: Cultural Evolution.......... 244 172 KEY TERMS AND IDEAS................................. 245 173 The Origin of Modern Humans......................... 246 174 The Dispersal of Modern Humans.................... 248 175 New Findings: Denisovans ............................... 250 176 New Interpretations: The Neanderthals ........... 251 177 Problems with Interpretation: H. floresiensis..... 252 178 Dating a Prehistoric Site................................... 253 179 Problems With Dating: H. naledi........................ 255 180 What You Know So Far..................................... 256 181 NCEA Style Question: Patterns of Dispersal.... 257 182 A Summary of Trends in Human Evolution....... 258 183 Scholarship Questions ..................................... 262 184 Scholarship Questions...................................... 266

APPENDIX Questioning terms and Birth Weight Data................ 269 PHOTO CREDITS.................................................... 270 INDEX .................................................................... 271

when completed


v

Using This Resource BIOZONE's NCEA Level 3 Biology Externals contains material to meet the needs of New Zealand students studying NCEA Biology Level 3 External Achievement Standards. The NCEA Level 3 Biology Externals is compliant with Level 8 of the NZ Curriculum (Nature of Science – The Living World) and the NCEA Biology Level 3 External Achievement Standards. A wide range of activities will help you to build on what you already know, explore new topics, work collaboratively, and practise your skills in data handling and interpretation. We hope that you find this resource useful and that you make full use of its features.

The outline of the chapter structure below will help you to navigate through the material in each chapter. Sections within a chapter share the same structure. They correspond to natural topic breaks within the Achievement Standard.

Introduction

Activities

Review

Test

• A check list of achievement criteria and explanatory notes • A check list of what you need to know • A list of key terms

• The KEY IDEA provides your focus for the activity • Annotated diagrams help you understand the content • Questions review the content of the page

• Create your own summary for review • Hints help you to focus on what is important • Your summary will help you with the NCEA style question

• NCEA style questions conclude clusters of related activities • These enable you to practise your NCEA exam skills

• Includes a question based on key terms • Other questions test your understanding of the section content

13 Homing Behaviour in Insects Key Idea: Homing is the ability of an animal to return to its home site after being displaced and it involves navigation. In many insects, homing is important in increasing foraging efficiency because it reduces energy expenditure. Homing (returning to a home site) is distinct from migration,

although navigation is involved in both behaviours. Homing behaviour often relies on the recognition of familiar landmarks, especially where the distances involved are relatively short. Navigation, often assisted by the use of trail pheromones, is also involved in the foraging behaviour of many insects.

Homing and navigation in wasps The beewolf (Philanthus) digs a nest in sand. It is a predator of bees and captures and paralyses bees as food for its larvae during development. The paralysed bee is taken back to the wasp's underground nest, where the wasp lays its eggs in the still living body. In a well-known experiment to test the homing behaviour of this wasp, a scientist named Tinbergen, carried out a 2-step experiment. (After Tinbergen, 1951. The Study of Instinct. Oxford University Press, London)

Wasp

21 What You Know So Far: Orientation in Space Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you: Alvesgaspar cc 3.0

20

Key terms and ideas

Beewolf Prey (bee)

Wasp

Philanthus Taxestriangulum and kineses

HINT: Include a definition as well as reference to navigation and the benefits and costs of migration. 30

HINT: Be sure to include definitions, adaptive value, and examples of both types of responses

22 NCEA Style Question: Migration Sooty shearwater The sooty shearwater (Puffinus griseus, muttonbird or titi) migrates up to 65,000 km. It is one of the longest migrations of any animal. From October to March, sooty shearwaters raise their chicks (which takes about 100 days) on oceanic islands around the sub-Antarctic region of New Zealand. During the breeding season, tens of thousands of chicks are taken by commercial hunters. From April to May, they begin migrating to specific areas of the sub-Arctic, arriving from June to July for 32 the Northern Hemisphere summer. The sooty shearwater is often seen behind fishing trawlers picking up scraps.

Pine cones Nest Pine cones

29

Homing and migration

Flight of two sooty shearwaters

Nest

Position of birds vs ocean productivity

Latitude

Step 2: Return flight During her absence, the pine cones were moved away from the burrow leading to the nest. Returning to the nest with prey, the wasp orientated to the circle of pine cones, not the nest entrance.

20 0

North Pacific

-20 -40

South Pacific

-60

Homing in ants

Breed

Migration

Breed

0.7 0.6 0.5 0.4 0.3 0.2 0.1

24 KEY TERMS AND IDEAS: Orientation in Space

Trade winds of Pacific Ocean

1. (a) What is the name given to a plant growth response to directional light? Productivity of oceans (g C m-2 d-1)

While a female wasp was in the burrow, Tinbergen placed a circle of pine cones around the nest entrance. When she emerged, the wasp reacted by carrying out a wavering orientation flight before flying off.

Cataglyphis desert ants use polarised light to navigate while foraging, often pausing and turning 360° to apparently note the position of the Sun and plane of light. When they discover a food source, they return directly to the nest as shown right. This ability to determine the direction to the nest reduces travel time when returning to the nest, making foraging more efficient.

0.9 0.8

60 Position 40 of birds

Step 1: Orientation flight

(b) What is the name given to a plant growth response to gravity? (c) What is the name given to a plant response that is independent of stimulus direction? (d) What plant hormone is principally responsible for the phototropic effect? 2. (a) The honeybee waggle dance communicates the location of a food source based on:

J FM A M J J A S O N D J Month

Food source

star compass navigation / local geography and landmarks / sun compass navigation (delete two)

waters (you round dance communicates that a food source is close by. Does it also communicate direction? Y / N 1. Discuss the migratory behaviour of the sooty shearwater as it travels from sub-Antarctic waters to sub-Arctic (b) The honeybee may use extra paper if needed). 3. (a) What responses are being shown by the orchid in • Explain why it would undertake such a long migration the photo (left): • Explain some of the methods it may be using to navigate • Suggest reasons why its numbers have been dropping

Foraging trip

Return journey Nest Cataglyphis ants collect a beetle

HINT: How do nastic responses differ from tropisms? What is their purpose?

(c) How are these responses adaptive?

Tangopaso CC 3.0

HINT: Include definitions and explain the mechanisms of phototropism and gravitropism. 2. (a) After a foraging trip, a Cataglyphis ant was displaced to another point some distance away. On the diagram shown right, draw in a line indicating the direction the ant travelled when released:

(b) What is the stimulus involved? Nastic responses

Tropisms 1. Why did moving the pine cones around the wasp nest result to the wasp being unable to find the nest?

Ant released at this point

Foraging trip

(b) Explain why the ant moved in the direction you drew:

4. Match the following words with their definitions:

Ant captured at food source

dispersal

A

Animal orientation and movement in response to a directional stimulus.

kinesis

B

The process of using environmental cures to determine position in reference to a goal.

migration

C

A one-way movement away from an area in response to environmental change.

navigation

D

A plant growth response to a directional external stimulus.

taxis

E

The long distance movement of animals from one region to another, usually seasonally.

tropism

F

A non-directional animal orientation response in which the speed or movement or rate of turning is proportional to stimulus intensity.

Nest

WEB

KNOW

13

LINK

12

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2. Suggest why the sooty shearwater begins its return journey in October when North Pacific Ocean productivity is greater than South Pacific Ocean productivity. 5.

The photo (left) shows swarming behaviour in locusts: (a) What event is likely to be occurring here?

© 1988-2016 BIOZONE International ISBN: 978-1-927309-56-8 Photocopying Prohibited

REVISE

TEST

(b) What distinguishes this behaviour from a migration?

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(c) What is the likely cue for this behaviour?

(d) How is this response adaptive?

TEST

PHOTOCOPYING PROHIBITED

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vi

Understanding the activity coding system and making use of the online material identified will enable you to get the most out of this resource. The chapter content is structured to build knowledge and skills but this structure does not necessarily represent a strict order of treatment. Be guided by your teacher, who will assign activities as part of a wider programme of independent and group-based work. Look out for these features and know how to use them:

252

Trends in human evolution

Achievement Standard

3.6 Key terms ape

Achievement criteria and explanatory notes

Au. afarensis

Achievement criteria for achieved, merit, and excellence

Ardipithecus ramidus Australopithecus spp.

A

carrying angle

Demonstrate understanding of trends in human evolution: Use biological ideas to describe trends in human evolution.

c

M

Demonstrate in-depth understanding of trends in human evolution: Use biological ideas to explain how or why trends in human evolution occur.

c

E

Demonstrate comprehensive understanding of trends in human evolution: Link biological ideas about trends in human evolution. This may involve justifying, relating, evaluating, comparing and contrasting, and analysing using scientific evidence.

Denisovans Dmanisi fossils

Homo floresiensis was very small and fully bipedal. Although the brain was very small, its organisation was advanced and stone tools associated with the skeleton indicated well established hunting technology. In contrast to these features, aspects of the skeleton showed primitive features found only in apes and early hominins. H. floresiensis probably lived 190,000 to 50,000 years ago. Its discovery caused widespread controversy and several opposing hypotheses were put forward to explain its place in human evolution. Since its discovery, earlier fossils dating to 700,000 years old have been found. The fossils were discovered in Liang Bua, a limestone cave on Flores Island, Indonesia. The cave contains 12 m of stratified deposits. The remains of modern humans, as well as Homo floresiensis, have been found in the cave.

Different interpretations of the fossils

H. ergaster

The discovery of Homo floresiensis caused a storm of controversy, not helped by the fact that the specimens were removed from their repository by one palaeontologist, kept from other scientists for three months, and returned damaged. The Indonesian government also denied scientists access to the cave where the fossils were found for two years. Several hypotheses were eventually put forward to explain how such a small statured hominin evolved or survived. These included:

H. floresiensis

f H. floresiensis evolved a result of island dwarfism. Island

gracile hominid hominoid Homo H. erectus

H. heidelbergensis H. neanderthalensis

Explanatory notes: Trends in human evolution

H. sapiens

Trends in human evolution refer to changes over time in relation to‌

primate

Changes in skull and endocranial features that reveal changes in brain structure.

sexual dimorphism

c

Changes in the manipulative ability of the hand.

2

f Detailed examination of the bones showed no overlap with

Human cultural evolution including:

25 - 34

a

The use of tools (stone, wood, and bone) and changes in tool technology.

39 - 44

Cultural evolution

b

The use of fire

Acheulian (tool)

c

Clothing

Broca's area

d

Abstract thought, including communication, language, and art.

e

Food gathering, including hunter gatherer to domestication of plants and animals.

f

Shelter including caves, temporary settlements and permanent settlements.

3

Patterns of dispersal of hominins. Hominins refers to living and fossil species belonging to the human lineage.

c

Mesolithic Mousterian (tool) c

with a disease or disorder. Some scientists put forward the idea that the small skull was a result of microcephaly, a neurodevelopment disorder. Others thought that perhaps H. floresiensis suffered from congenital hypothyroidism. any features expected from individuals with the diseases or disorders listed above. A study of the bones and joints of the arm, shoulder, and lower limbs concluded that H. floresiensis was more similar to early humans and apes than modern humans. Small brain size coupled with more advanced brain organisation indicate possible parallel evolution of sapiens-like features.

4.0

b

1 - 20

No chin present.

f H. floresiensis is not a new species but instead an individual

CC

robust

Activity number

na

Skeletal changes linked to bipedalism.

Oldowan (tool)

Facial features: Relatively modern dentition, but teeth are large relative to the rest of the skull.

aily

Human biological evolution begins with early bipedal hominins and may require comparison with living hominids. These trends involve:

a

prognathic

Neolithic

3D scans showed expansion of the prefrontal cortex and temporal lobes, brain regions associated with complex thought.

Sc

1

c

prehensile

valgus angle

Brain size: Very small, only 380 cc.

dwarfism is a relatively common occurrence where large animals become smaller over time when isolated, e.g. the extinct pygmy elephants on Flores showed this adaptation.

H. habilis

Paranthropus spp.

floresiensis, thought to have lived on the island as recently as 18,000 years ago. However, revised dates in 2016 indicate that H. floresiensis lived ~190,000-50,000 years ago. The new date is close to the time that modern humans reached the area, suggesting that encounter with H. sapiens may have contributed to the demise of the Flores population.

Rosino

c

bipedal (bipedalism)

177 Problems With Interpretation: H. floresiensis Key Idea: The discovery of Homo floresiensis has proved highly controversial with several hypotheses proposed to explain its position in hominin evolution. In 2003, hominin fossils, including an almost complete skeleton, were discovered on the island of Flores, Indonesia. The fossils were assigned to a new species, Homo

Recognisable trends characterise the evolution of humans: bipedalism, increase in brain size, reduction in teeth, reduction in facial projection, and increasing importance of art, spirituality, tool technology, and sociality.

Biological evolution

Free response questions allow you to use the information provided to answer questions about the content of the activity, either directly or by applying the same principles to a new situation. In some cases, an activity will assume understanding of prior content.

The activities form most of this book. They are numbered sequentially and each has a task code identifying the skill emphasised. Each activity has a short introduction with a key idea identifying the main message of the page. Most of the information is associated with pictures and diagrams, and your understanding of the content is reviewed through the questions. Some of the activities involve modelling and group work.

The chapter introduction provides you with a summary of the achievement criteria and explanatory notes as identified in the Achievement Standard. A check list of what you need to know to meet the knowledge requirements of the standard is provided on the second page of the introduction. Use the check boxes to identify and mark off the points as you complete them. A list of key terms for the chapter is included.

Homo floresiensis

Homo sapiens

1. Explain the effect that the Flores finds had on the hypothesis that hominins continually evolved larger brains and bodies: 48 - 69

2. Describe the different interpretations of the H. floresiensis bones:

Palaeolithic Wernicke's area Dispersal multiregional hypothesis Out of Africa hypothesis WEB

KNOW

A TASK CODE on the page tab identifies the type of activity. For example, is it primarily information-based (KNOW), or does it involve modelling (PRAC)? A full list of codes is given on the following page but the codes themselves are relatively self explanatory.

LINK

177 149

WEB tabs at the bottom of the activity page alert the reader to the Weblinks resource, which provides external, online support material for the activity, usually in the form of an animation, video clip, photo library, or quiz. Bookmark the Weblinks page (see next page) and visit it frequently as you progress through the book.

PHOTOCOPYING PROHIBITED

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LINK tabs at the bottom of the activity page identify activities that are related in that they build on content or apply the same principles to a new situation.


1. Explain the effect that the Flores finds had on the hypothesis vii

Using the Tab System

The tab system is a useful system for quickly identifying related content and online Links generally refer 2. Describe thesupport. different interpretations of to theactivities H. floresiensis bon that build on the information in the activity in depth or extent. A link may also reflect on material that has been covered earlier as a reminder for important terms that have already been defined. In the example below for the activity "Problems with Interpretation: H.floresiensis", the weblink 177 provides information about the fossil finds in Indonesia. Activity 149 directs back to probable human phylogenies to see where H. floresiensis may have fitted in on the evolutionary timeline. The weblinks code is always the same as the activity number on which it is cited. On visiting the weblinks page (below), find the number and it will correspond to one or more external websites providing a video or animation of some aspect of the activity's content. Occasionally, the weblink may provide a bank of photographs where images are provided in colour.

WEB

Activities are coded KNOW = content you need to know

KNOW

LINK

177 149

DATA = data handling and interpretation PRAC = a paper practical or a practical focus REVISE = review the material in the section TEST = test your understanding

Weblinks

Bookmark the weblinks page: www.biozone.co.nz/weblink/ NZL3E-9568 Access the external URL for the activity by clicking the link

Link

Connections are made between activities in different sections of the syllabus that are related through content or because they build on prior knowledge.

www.biozone.co.nz/weblink/NZL3E-9568 This WEBLINKS page provides links to external websites with supporting information for the activities. These sites are distinct from those provided in the BIOLINKS area of BIOZONE's web site. For the most part, they are narrowly focussed animations and video clips directly relevant to some aspect of the activity on which they are cited. They provide great support to help your understanding of basic concepts.

Chapter in the book Hyperlink to the external website page.

Activity in the book

Bookmark weblinks by typing in the address: it is not accessible directly from BIOZONE's website Corrections and clarifications to current editions are always posted on the weblinks page

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viii

How to Scaffold an NCEA Style Answer The external NCEA exams require you to demonstrate your understanding of a particular concept by providing a written paragraph or essay. Generally the question is designed as an open answer (meaning there is no definitive answer) in which you can demonstrate your level of understanding. The question may give you some guidance as to what you should include in your answer, such as definitions of certain terms or to provide specific examples. In order to gain the highest possible mark in these questions, you need to lay out your answer in a clear and logical way so that the examiner can easily see how you have demonstrated your understanding of the topic. The difference between you obtaining an achievement, merit, or excellence grade depends on how well you demonstrate your understanding of a concept.

• Defining, drawing, annotating, or giving a description of a process is achievement level only.

• Explaining how a process works, why it works, and how changes to it may affect an outcome is merit level.

• Linking biological ideas, comparing and contrasting, analysing, or justifying ideas is excellence level. The following example question shows how an answer can be built up from a simple definition, through explanation, to comparisons and linking of ideas.

Mutation is a fundamental process in evolution. Discuss the role of mutation in the evolution of populations. In your answer you should define mutation and explain how mutation can change in the genetic makeup of a population and lead to speciation. You may use examples to illustrate your argument:

The term mutation is defined Different types of mutations are briefly described. Fitness is defined. The significance of mutation to the genetic makeup of a population is described. The possible consequences of a beneficial mutation to allele frequencies and speciation are explained.

Examples illustrate to role of gene and genomic duplications in evolution.

A mutation is a change to the DNA sequence. Gene mutations can involve small changes, e.g. to a single nucleotide or a triplet, and may result in a non-functional protein or a new useful protein variant. Other mutations may involved larger scale parts of chromosomes (e.g. gene duplications) or even genomes (e.g. polyploidy). Mutations that occur in the gametes (germline mutations) may be inherited and so can affect later populations. Mutations are the source of all new alleles. Changes to proteins are most commonly harmful and are quickly removed from the population's gene pool because they do not contribute to fitness (successful survival and reproduction). However, sometimes new alleles can be created that are beneficial to the organism in some way, e.g. a germ line mutation in the gene for an enzyme in a plant may enable it to break down a natural toxin in the soil more quickly. If the environment of the time provides a selective advantage to the plants with the mutation, the mutation will become relatively more common in the population (by the process of natural selection). Over time, the plants with the mutant allele will be favoured and the mutation will become more common (the frequency of that allele will increase relative to other alleles). This process is evolution. The plants with the mutation may also be able to escape competition and colonise new areas, so they can potentially become isolated from plants without the mutation. Once they are separated ecologically, gene flow between the populations will slow and genetic differences between the populations will increase. Genetic drift and natural selection will affect each population differently and reproductive isolating mechanisms will develop within each population, isolating them further. When speciation is complete, the two populations (one with the mutation and one without) will be unable to interbreed naturally and gene flow between them will stop (a new species forms). Gene duplications can be very important in evolution because they provide (a) more useful copies of the same proteins (giving a selective advantage through a dosage effect) or (b) redundancy of gene function so that extra copies may be adapted for other functions. The duplication and then change to alleles leads to a change in allele frequencies (evolution) and has been important in the genetic divergence of many taxa, including primates. In some cases in plants, entire genomic duplications (polyploidy) can result in immediate genetic isolation of an organism. Sometimes, in plants, a hybridisation event between two species may produce an infertile hybrid, which can reproduce asexually (vegetatively). Hybrids often show greater fitness than either parent. This is an example of instant speciation. A subsequent polyploidy event in the infertile hybrid can make it fertile (producing even sets of chromosomes for pairing at meiosis). This type of speciation (hybridisation followed by polyploidy) has been important in the evolution of wheat and many other plants, including New Zealand species of Melicytus. PHOTOCOPYING PROHIBITED

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Responses to the external environment

Achievement Standard

3.3 Key terms

The short and long term responses of plants and animals to their external environment are adaptive, enabling organisms to maximise fitness in their ecological niche. Responses include orientation in space and time as well as responses to other organisms in their environment.

Common terms adaptive advantage environmental cue innate behaviour learned behaviour Orientation in space dispersal homing kinesis (pl. kineses) migration nastic response navigation phytohormone taxis (pl. taxes) tropism Orientation in time actogram annual rhythm biological clock biological rhythm circadian (daily) rhythm endogenous entrainment exogenous free running period lunar rhythm period (of rhythm) phase shift photoperiodism tidal rhythm zeitgeber Species interactions aggression agonistic behaviour altruism communication competition cooperative behaviour exploitation hierarchy kin selection mutualism reproductive behaviour social behaviour territory

Achievement criteria and explanatory notes Achievement criteria for achieved, merit, and excellence c

A

Demonstrate understanding of the responses of plants and animals to their external environment: Describe plant and animal responses to their external environment, including the process(es) within each response and/or the adaptive advantage provided for the organism in relation to its ecological niche.

c

M

Demonstrate in-depth understanding of the responses of plants and animals to their external environment: Use biological ideas to explain how responses occur and why the responses provide an adaptive advantage for the organism in relation to its ecological niche.

c

E

Demonstrate comprehensive understanding of the responses of plants and animals to their external environment: Link biological ideas to explain why the responses provide an adaptive advantage for the organism in relation to its ecological niche. This may involve justifying, relating, evaluating, comparing, contrasting, and analysing the responses of plants and animals to their external environment.

Explanatory notes: Plant and animal responses Responses are selected from those relating to…

Activity number 1 - 20

c

1

Orientation in space to include tropisms and nastic responses in plants, and taxes, kineses, homing, and migration in animals.

c

2

Orientation in time to include annual, daily, lunar and tidal rhythms.

25 - 34

c

3

Interspecific relationships to include competition for resources, mutualism, and exploitation (herbivory, predation, and parasitism).

39 - 44

c

4

Intraspecific relationships to include competition for resources, territoriality, hierarchical behaviour, cooperative interactions, and reproductive behaviour.

48 - 70

The external environment includes both biotic and abiotic factors… 5

Biotic factors are those arising from living things or their activities, e.g. competition.

6

Abiotic factors are factors in the physical environment, e.g. light-dark cycles.


What you need to know for this Achievement Standard Orientation in space Activities 1 - 24 By the end of this section you should be able to: c

Distinguish between taxes and kineses and identify them as innate responses.

c

Describe examples of taxes, the environmental cue involved in each case, and the adaptive advantage of the behaviour in relation to the organism's niche.

c

Describe examples of kineses, the environmental cue involved in each case, and the adaptive advantage of the behaviour in relation to the organism's niche.

c

Describe migratory behaviour, including at least one example from New Zealand. Explain the adaptive advantage of migration, despite its costs. Distinguish migration from dispersal.

c

Describe examples of homing behaviour and distinguish it from migration. Explain the adaptive advantage of the behaviour and its dependence on environmental cues.

c

Using examples, explain how navigation is involved in migratory and homing behaviour.

c

Explain how social insects communicate directional information to enable others to locate resources. Identify the mechanisms involved and the adaptive advantage of the behaviour.

AKA

Orientation in time Activities 25 - 38 By the end of this section you should be able to: c

Describe and explain how plant and animal behaviours are linked to natural environmental rhythms that occur with a predictable frequency. Define the term biological rhythm.

c

Describe and explain the characteristics of daily, tidal, lunar, and annual rhythms. Explain how an organism's biological rhythms provide an adaptive advantage in its ecological niche.

c

Describe and explain the two mechanisms underlying biological rhythms: the endogenous biological clock and the external zeitgeber (environmental cue).

c

Describe and explain diurnal, nocturnal, and crepuscular activity patterns in animals with circadian rhythms. Explain the adaptive value of these activity patterns in each case.

c

Interpret actograms recording the circadian rhythms of animals. Demonstrate an understanding of the free running period, phase shift, and entrainment.

c

Explain photoperiodism in plants, including the role of phytochrome in measuring daylength by resetting the biological clock (entrainment). Distinguish between long-day and short-day plants.

Interspecific relationships Activities 39 - 47 By the end of this section you should be able to: c

Describe and explain species interactions, including mutualism, exploitation (herbivory, predation, parasitism), and competition for resources. Identify the adaptive advantages of the relationship to one or both of the parties involved.

c

Explain the evolutionary consequences of interspecific competition (niche differentiation).

Intraspecific relationships Activities 48 - 73 By the end of this section you should be able to:

Jenny Ladley Uni. of Canterbury

c

Distinguish different types of animal organisation, solitary, or groups with or without a social structure. Describe the adaptive advantage of group and social behaviours.

c

Describe how animals communicate. Interpret ethograms and record animal behaviour using an appropriate system to identify the type of behaviour and its intensity.

c

Describe examples of cooperative behaviour and explain its adaptive advantage.

c

Describe intraspecific competition for resources, the behaviours associated with it (e.g. agonistic behaviour), and its consequences (hierarchies, territories, home ranges).

c

Explain the role of territories and hierarchies in allocating resources and reducing aggression.

c

Describe reproductive behaviours in animals and explain their adaptive advantage, including reference to courtship behaviours, mating systems, and parental care.


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Why Organisms Need To Respond and reproductive success (fitness) is called an adaptive behaviour. Behaviours (usually called responses in plants) are subject to natural selection. Those that increase fitness are retained in a population, whereas those that decrease fitness are eventually lost. Some behaviours are so important they are innate, i.e. genetically programmed. They do not require learning. For example a maggot exposed to light will immediately seek lower light levels because this behaviour reduces the risk of being eaten or drying out. The behaviour is not learned and every maggot responds the same way.

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Key Idea: An organism's response to the environment is called its behaviour. Adaptive behaviours increase an organism's fitness (genetic contribution to the next generation). The environment in which any organism lives is always changing, for example, light to dark or warm to cool. Organisms need to respond to these changes in order to survive. The response of the organism is called its behaviour, which may be simple, e.g. moving away from light, or more complex, e.g. calling and displaying for a mate. A behaviour that contributes to an organism's survival

Orientation behaviours Positioning in response to an environmental stimulus

The position of the Sun is important in honey bee navigation.

Navigation ffSun compass

ffMagnetic compass

Animals

ffChemical cues

ffKineses: Non-directional ffTaxes: Directional

ffLandmarks

Plants

ffTropisms: Directional ffNastic responses: Non-directional

The position of flowers (food sources) is communicated through body movements.

Honeybees orientate towards the light to escape confinement.

Species interactions ffCommunicating

Timing behaviours

Predictable responses to environmental rhythms ffAnnual, daily, lunar, tidal

ffInvolves a biological clock

ffCompetition

Honeybees are active during the day (diurnal).

ffMutualism

ffExploitation

ffBreeding behaviour

(b) In what way is behaviour adaptive?

2. Contrast an orientation behaviour with a timing behaviour

3. Suggest how a behaviour might become innate:

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1. (a) What is a behaviour?

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Types of Stimuli eyes detect light. Most animals, being mobile, monitor the environment as they move through it, so sensory receptors are concentrated in the head region. Stimuli are described using prefixes, e.g. photo-. Orientation responses towards or away from the stimulus are identified as positive or negative.

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Key Idea: Orientation responses can be categorised according to the type of stimulus eliciting the response. A stimulus is a change in the internal or external environment capable of eliciting a response in an organism. To do this, a stimulus must be detected by sensory receptors, e.g. Stimulus

Prefix

Touch

Thigmo-

Light

Photo-

Gravity

Gravi-

Chemicals

Chemo-

Water

Hydro-

Temperature

Thermo-

B

D

Light can convey information about orientation (up or down) and about the presence of others. Sudden changes in light can indicate movement, which may need to be avoided.

A

E

Chemicals indicate the presence of substances that may be useful (food) or harmful (poisons) or may indicate the proximity of other individuals.

C

Detecting changes in temperature helps organisms survive by adjusting physiology or behaviour to their surroundings. An increase in temperature beyond a certain limit indicates the need to find shade.

F

USDA

Touch is an important stimulus. It may indicate the presence of a threat or something that will give support.

At its simplest, a reaction to a stimulus can be towards (positive) or away (negative) from the stimulus.

Lamp

Positive: towards the stimulus

Plants are immobile so the ability of roots to grow towards available water sources aids survival. Invertebrates with poor resistance to drying out are found in moist environments.

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Gravity allows organisms to orientate themselves vertically. Most animals tend to orientate dorsal ("back") side up and ventral ("belly") side down. In plants, gravity is an important stimulus for the correct orientation of shoots and roots.

Negative: away from the stimulus

1. Identify the prefix for each of the examples A to F above: A:

D:

B:

E:

C:

F:

2. Identify the orientation response of the snail to the light: LINK

KNOW

1

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Kineses involve orientation directly to the stimulus and are typical of many invertebrates and protozoa. Two main types of kineses can be identified. In an orthokinesis, the rate of movement is dependent on the stimulus intensity. In a klinokinesis, the rate of turning isInvestigation related to the stimulus intensity. of kinesis in woodlice

PR E V ON IEW LY Kinesis in woodlice

70

60

300

35

Number of turnings

30

50

40

30

Millimetres per minute

250

Number of turnings per hour

Woodlice are commonly found living in damp conditions under logs or bark. Many of the behavioural responses of woodlice are concerned with retaining moisture. Unlike most other terrestrial arthropods, they lack a waterproof cuticle, so water can diffuse through the exoskeleton, making them vulnerable to drying out. When exposed to low humidity, high temperatures, or high light levels, woodlice show a kinesis response to return them to their preferred, high humidity environment.

40

350

25

Speed

200

20

150

15

100 50

10 5

% of time at rest

20

From Allott 2001

% of time at rest

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Key Idea: Kineses are innate locomotory behaviours involving non-directional movements in response to external stimuli. A kinesis (pl. kineses) is a non-directional response to a stimulus in which the speed of movement or the rate of turning is proportional to the stimulus intensity. Kineses do not

10 20 30 40 50 60 70 80 90 100 Relative humidity

0

Investigating kinesis in woodlice

Experiment 2

To investigate the effect of a light-dark regime on the orthokinetic behaviour of woodlice.

To investigate the effect of a light-dark regime on the kilinokinetic behaviour of woodlice.

Method

Method

A petri dish was laid out with 1 cm x 1 cm squares. The investigation was carried out at room temperature (about 21°C). A woodlouse was placed in the petri dish under constant light. The number of squares the woodlouse passed over in five minutes was recorded. This was repeated four times. The woodlouse was then placed in constant dark and the number of squares it passed over in five minutes recorded. Again, this was repeated four times. The results are shown below.

The woodlouse was again placed in the petri dish under constant light. The experiment was carried out at room temperature as in experiment 1. The number of turns the woodlouse performed in five minutes was recorded. This was repeated four times. The woodlouse was then placed in constant dark. Again the number of turns performed in five minutes was recorded. This was also carried out four times. The results are shown below.

Results

Results

Number of squares crossed

Number of turns

Trial

Light

Dark

Trial

1

122

15

1

2

206

68

2

3

103

57

3

4

70

59

4

Mean

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Experiment 1

Mean

Light

Dark

80

10

165

20

110

122

90

55

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35°C

30°C

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Kinesis in body lice

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In a circular chamber, lice make relatively few turns at their preferred temperature of 30°C, but many random turns at 35°C. This response enables the lice to increase their chances of finding favourable conditions and remaining in them once found.

1. Use the graph on woodlice at the top of the previous page to answer the following questions: (a) At which relative humidities do the following occur: i. Largest number of turnings per hour:

ii. Highest speed of movement:

iii. Largest percentage of time at rest:

(b) Explain the significance of these movements:

(c) What is the preferred range of relative humidity for the woodlice?

2. (a) Complete the results tables on the previous page by calculating the mean for each of the experiments. (b) Which regime (light or dark) does the woodlice appear to prefer?

(c) Explain your reasoning:

(d) Explain how increasing the number of turns or the speed of movement increases a woodlice's likelihood of survival when in a unfavourable environment.

3. (a) Identify the preferred temperature of a body louse:

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(b) The response of the body louse is a klinokinesis / orthokinesis (delete one)

(c) Contrast the movements of the body louse when within and when outside its preferred temperature environment:

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Taxes stimulus, e.g. fish orientate dorsal (back) side up in response to both light and gravity. Orientation responses are always classed according to whether they are towards the stimulus (positive) or away from it (negative). Simple orientation responses are innate (genetically programmed). More complex orientation responses may involve learning (the behaviour may be modified based on experience).

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Key Idea: A taxis is an innate locomotory behaviour involving directional movements in response to external stimuli. Taxes (sing. taxis) involve orientation and movement in response to a directional stimulus or a gradient in stimulus intensity. Taxes often involve moving the head until the sensory input from both sides is equal (klinotaxis). Many taxes involve a simultaneous response to more than one

When confronted with a vertical surface, snails will reorientate themselves so that they climb vertically upwards. The adaptive advantage of this may be to help the snail find food or shelter, or to avoid overly wet surfaces.

A flying male moth, encountering an odour (pheromone) trail left by a female, will turn and fly upwind until it reaches the female. This behaviour increases the chances of the male moth mating and passing on its genes to the next generation.

A

B

Male moths detect pheromones with their large antennae.

Female moth

Male moth

Spiny lobsters (crayfish) will back into tight crevices so that their body is touching the crevice sides. The antennae may be extended out. This behaviour gives the lobsters greater protection from predators.

C

Crayfish in hole

Blowfly maggots will turn and move rapidly away from a directional light source. Light usually indicates hot, dry areas and the maggots avoid predators and desiccation (drying out) by avoiding the light.

D

E

Directional sunlight

No Cla t fo ssr r o Us om e

At close range, mosquitoes use the temperature gradient generated by the body heat of a host to locate exposed flesh. This allows the female to find the blood needed for the development of eggs.

White fly larvae burrowing into soil.

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LINK

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1. Distinguish between a kinesis and a taxis:

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2. Describe the adaptive value of simple orientation behaviours such as taxes:

3. For each example (A-E) on the previous page, describe the orientation response and whether it is positive or negative: (a) A:

(d) D:

B: (b)

(e) E:

C: (c)

4. The diagrams on the right show the movement of nematodes on plates where a salt (NH4Cl) was added (A) and on a plate where no NH4Cl was added (B).

(a) Describe the movements of the nematodes in plates A and B:

A

(b) Name the orientation behaviour shown in plate A:

Drop of NH4Cl added

(c) Describe an advantage of this kind of behaviour to nematodes:

KEY: • Nematodes added

B

Distance of maggot 1 from start point (cm)

Distance of maggot 2 from start point (cm)

10

-1.7

-3.7

20

-0.5

-0.0

30

+0.7

-0.8

40

+0.2

-1.4

Distance of maggot 3 from start point (cm)

Distance of maggot 4 from start point (cm)

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Time (s)

-5.8

-3.0

+1.8

-1.5

-6.1

-0.2

+1.0

-1.0

Describe the movements of the maggots during the experiment. Include whether the maggots are positively or negatively phototactic and the rate of the movements.

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S. Ward, Medical Research Council 1973

5. Some students carried out an investigation of the phototactic movements of maggots. They set up a lamp in a darkened room and placed a maggot on grid paper 10 cm from the lamp. They then recorded the distance the maggot had moved every 10 s. Movements towards the lamp were recorded as positive (+) while movements away from the lamp were recorded as negative (-). The investigation was repeated four times. The results are shown below:


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Pheromones mark territories and advertise their readiness to mate. Other mammals, including rabbits, release a mammary pheromone that triggers nursing behaviour in the young. Pheromones are also used as signalling molecules in social insects such as bees, wasps, and ants. They may be used to mark a scent trail to a food source or to signal alarm. Pheromones are widely used as baits to attract and trap insect pests.

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Key Idea: A pheromone is a chemical produced by an animal and released into the external environment where it affects the physiology or behaviour of members of the same species. Pheromones, which are often sex attractants, are common amongst insects and mammals, and commonly relate to reproductive behaviour. Many mammals, including canids and all members of the cat family, use scent marking to

Pheromones in animal communication and orientation

In mammals, pheromones are used to signal sexual receptivity and territory, or to synchronise group behaviour. Pheromone detection relies on the vomeronasal organ (VNO), an area of receptor tissue in the nasal cavity. Mammals use a flehmen response, in which the upper lip is curled up, to better expose the VNO to the chemicals of interest.

Communication in ants and other social insects occurs through pheromones. Foraging ants leave a trail along the ground that other ants will follow and reinforce until the food source is depleted. Ants also release alarm substances, which will send other ants in the vicinity into an attack frenzy. These signals dissipate rapidly if not reinforced.

Reptiles also use the VNO to detect chemicals. The flicking of a snake's tongue samples chemicals in the environment and delivers them to the VNO. This behaviour is used to detect prey. Photo courtesy of Cereal Research Centre, AAFC

Pheromones produced by a honey bee queen and her daughters, the workers, maintain the social order of the colony. The pheromone is a blend of unsaturated fatty acids.

The feathery antennae of male moths are specialised to detect the pheromone released by females. Males can detect concentrations as low as 2 ppm. They use wind direction to orientate, flying upwind to find the female. The sex attractant property of pheromones is used in traps, which are widely used to trap insect pests in orchards.

1. (a) What is a pheromone?

(b) What is the significance of pheromones being species specific?

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2. Explain how the response of a male moth to female pheromone is adaptive:

3. Explain the role of pheromones in orientation and communication in social insects:

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LINK

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Migration different times of the year or at certain stages in their life cycle. Migratory behaviour is innate but there may be a learned component for repeat migrants. The behaviour is triggered by an environmental cue, e.g. a change of season. Migration carries risk and has a high energetic cost. These disadvantages are offset by the benefits offered by the new environment, e.g. food supplies to support breeding.

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Key Idea: Migration is the long distance movement of individuals from one place to another. The risks and energetic costs of migration are offset by gains made at the destination. Migration is the long distance movement of individuals from one place to another. It usually occurs on a seasonal basis and for a specific purpose, e.g. feeding, breeding, or over-wintering. Many animals move great distances at In order for migratory behaviour to evolve and be maintained, the advantages of migration must outweigh the disadvantages. Migration is a risky and energy expensive behaviour, and animals must spend a lot of time building energy stores that will fuel the effort. The destination provides enough food or shelter to enhance survival of individuals and their offspring. Although some animals migrate individually, many migrate in large groups (right and bottom). The energy cost of migration is different for birds, mammals, or other animals. Studies show that for a 100 g animal to travel 1 km a running mammal uses 2400 J, a flying bird uses 640 J and a swimming fish uses just 240 J. One gram of fat gained while feeding before a migration gives the animal about 37 kJ of energy, taking a mammal 15 km, a bird 54 km, and a fish 154 km. The migrations of walking or running animals therefore tend to be much shorter than those of flying or swimming animals.

Group migration helps navigation by what is called the "many wrongs principle" in which the combining of many inaccurate navigational compasses produces a more accurate single compass. Thus, if an animal navigates by itself with a slightly inaccurate internal compass, or inaccurately interprets environmental cues, it may arrive in the wrong location. In a group, each member can adjust its heading according to the movement of the others, thus an average direction is produced and each member is more likely to arrive at the correct place (right). Increasing group size decreases the time taken to reach a navigational target when the group is moving as a social unit. Non-social groups take longer with increasing size because of the need to avoid others in the group (right).

Average time taken to reach target (arbitrary time units)

Benefits of group migration

Flocking birds increase aerodynamic efficiency to each other, saving energy. In schooling fish, individuals in the centre of the school use less effort. Flocking and schooling also provide feeding benefits and reduce the risk of predation along the migration route.

Non-social movement No collision avoidance Group movement

Codling et al, Ecology, 2007

Group size

1. What is migration?

No Cla t fo ssr r o Us om e

2. (a) What are the costs of migration to the migrant?

(b) How is the length of the migration related to energetic cost to the animal?

(c) Why do animals migrate despite these risks/costs?

3. (a) How does grouping together increase navigational efficiency?

(b) How does this enhance individual survival?

KNOW

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Migration Patterns as overwintering, breeding, or seeking food. Some mass movements of animals are not true migrations in that they do not involve a return journey and they are not governed by an internal biological clock. Such movements are best described as dispersals and are typical of species such as the ‘migratory’ locusts of north Africa and Australia.

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Key Idea: Migrations often involve very large distances and usually involve a return journey. They are initiated by the activity of internal clocks or timekeepers in response to environmental cues such as change in daylength. True migrations are those where animals travel from one well-defined region to another, for a specific purpose such

Dispersal: one-way migration

Some migrations of animals involve a one-way movement. In such cases, the animal does not return to its original home range. This is typical of population dispersal. This often occurs to escape deteriorating habitats and to colonise new ones.

Breeding site

Original home range

Breeding site

Return migration: caribou

Breeding site

Dry season or winter site

Nomadic migration

Similar to one-way migration but individuals may breed at several locations during their lifetimes. These migrations are apparently directionless, with no set pattern. Each stopover point is a potential breeding site. There may also be temporary non-breeding stopovers for the winter or dry season.

Breeding site

Breeding site

Breeding site

Breeding site

Non-breeding stopover

Breeding site

Nomadic Inuit

Remigration circuits

In some populations, the return leg of a migration may have stopovers and may be completed by one or more subsequent generations. In addition to winter or dry season areas, there may be stops at feeding areas by juveniles or adults. Also included are closed circuits where animals die after breeding.

Dispersal: muskrat

Breeding site

Breeding site

Return migration

Animals that move to a winter feeding ground are making one leg of a return migration. The same animals return to their home range in the spring which is where they have their breeding sites. Sometimes they follow different routes on the return journey.

Breeding site

Nomadic Bedouin

Feeding stopover

Second generation

Dry season or winter site

First generation

Remigration circuit: Pacific salmon

No Cla t fo ssr r o Us om e

1. Giving an example, describe the conditions under which nomadic migration behaviour might be necessary:

2. Which of the above forms of migration would lead to further dispersal of a population? Explain your answer:

3. Describe an environmental cue important in the regular migratory behaviour of a named species:

4. Explain the adaptive value of migratory behaviour:

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KNOW


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Examples of Migration do not have to be long distances or seasonal. Many marine animals migrate from the deep ocean to the surface daily to feed, this may only be a distance of a few hundred (vertical) metres or less.

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Key Idea: Migrations are usually for the purpose of feeding or breeding. True migrations involve a return journey. Migrations come in many forms. Some of the longer, more commonly noted ones are shown below. However, migrations

PACIFIC OCEAN

Sargasso Sea

ATLANTIC OCEAN

PACIFIC

INDIAN

Ascension Island

Migratory locusts are found in desert regions of northern and eastern Africa, the Middle East and Australia. Their migration is more strictly a dispersal in response to an expanding population with limited food. The lack of food triggers development of the voracious, migratory form.

3000 km

A number of shearwater species (including mutton birds) breed in Australia and islands around New Zealand, then migrate northwards with the onset of the southern winter to the north and northeast Pacific. The return journey across the eastern Pacific is assisted directly by the NE trade winds. Green turtles migrate between coastal foraging areas and nesting grounds. They return from the coasts of South America to the beach of their own spawning on Ascension Island to lay eggs.

Caribou spend the winter feeding in the coniferous forests in central Canada. In the spring, they move north to the tundra of the Barren Lands, within the Arctic circle, a distance of some 1000 km. There they give birth to their calves in the relative safety of the open tundra.

3000 km

European eels migrate across the northern Atlantic ocean to spawn in the Sargasso Sea off the coast of Florida. The larvae that hatch from the eggs gradually drift back across to Europe, a migration that takes several years. Eventually they enter estuaries and move upriver where they feed, grow and mature.

OCEAN

11,000 to 13,500 km

750 to 1000 km

The European swift is one of 140 bird species that follow one of Europe's migratory routes from northern Spain to Africa. Swifts breed throughout Europe, and migrate to south of the Sahara after breeding. Swifts feed on the wing and the onset of the migration is thought to be triggered by the lack of nutritious airborne insects.

A number of whale species, including humpback and grey whales, follow an annual migration. In summer, they feed in the krill-rich waters of polar regions. In winter, they move closer to the equator to give birth to young conceived the previous year and to mate again. They seldom feed in transit.

3000 to 12,000 km

7000 km

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OCEAN

Polar bears can cover distances of up to 1600 km walking across ice from Alaska, USA to set up winter dens across the Bering Strait in Siberia.

3000 km

1600 km

Monarch butterflies have one of the longest of all insect migrations. Five or more generations are needed to complete one migration cycle. In North America, the insects overwinter in mass roosts in southern California or near Mexico City. In spring they migrate north, with some even reaching Canada by late summer, then return south for winter.

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2000 to 4000 km

In New Zealand and elsewhere, spiny lobsters periodically make migrations of many hundreds of kilometres. The movement is predominantly against the prevailing current. It is thought to compensate for the long-term downstream movement of the population as planktonic larvae are swept in one 800 km direction by the ocean currents.

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13 The origins of migration

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Migration is often an adaptive response to seasonal environments, allowing animals to exploit favourable conditions at different times of the year. Migrations probably evolved as a result of seasonal changes in distribution that offered benefits to fitness. However, very little evidence has been uncovered to shed light on how animals such as the Arctic tern came to migrate 70,000 km from one pole to the other and back every year. Some computer models based on the current distribution and migration of North American birds suggest the ancestral populations lived in North America all year round before evolving migrations that took them to the tropics during the Northern Hemisphere winter. The origins of oceanic crossings is still contested. It is possible that some species were migrating before the continents split and drifted apart, but this assumes that the same route has been used for millions of years.

Migrations are no doubt based in part on the search for food and shelter. As food becomes scarce in winter animals move to new areas in search of food, returning when conditions become more favourable.

1. Match up the ten numbered migration routes on the map on the previous page with each of the animals below:

(a) Migratory locust:

(f) Monarch butterfly:

(b) Caribou:

(g) European swift:

(c) Shearwater:

(h) Humpback whale:

(d) Polar bear:

(i) European eels:

(e) Green turtle:

(j) Spiny lobster:

2. Describe an adaptive advantage of migration for each of the organisms listed below:

(a) Monarch butterflies:

(c) Spiny lobster:

3. There is now ample evidence that the distributions and migratory patterns of animals are being affected by rising global temperatures. Northern Hemisphere data show that birds are migrating north to summer feeding grounds up to two weeks earlier and are not migrating as far south in winter. The mean January temperature over the period plotted (right) has increased by ~3.5°C. (a) Describe how increases in global temperatures have affected some migratory birds:

72

Change in centre of abundance in 305 widespread North American birds

64 56 48 40 32 24 16 8 0

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(b) Humpback whale:

Distance moved north (km)

4

3/7

7 19

8

7/7

7 19

/82

81

19

/86

85

19

/90

89

19

/94

93

19

/98

97

19

/02

01

20

(b) Explain how these changes in migratory patterns might affect food availability and survival for these populations:

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Bird Migrations in New Zealand The movements of four species of migrant waders overwintering at Miranda in the Firth of Thames are shown below. The tidal flats at Miranda offer a rich feeding ground.

Parengarenga Harbour

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Key Idea: New Zealand has a number of migrant bird species. Some move great distances, according to their needs in the different seasons.

Wrybill

Kaipara Harbour

Manukau Harbour Firth of Thames

Pied stilt

Pied stilt

Himantopus h. leucocephalus

Anarhynchus frontalis

The wrybill breeds on riverbeds in Canterbury and Otago where nests are made in pebble-lined scrapes in the shingle. In winter, most of the population heads north to feeding grounds at the Firth of Thames, the Manukau and Kaipara Harbours and elsewhere on the coast.

Pied stilt

During the breeding season, pied stilts can be found in swamps, lagoons, flooded pastureland and open wetlands in both North and South Islands. To overwinter after breeding, they move to the coast with some movement northwards.

Pied stilt

Banded dotterel

Banded dotterel

Wrybill

South Island pied oystercatcher

Banded dotterel

Pied stilt Canterbury

Charadrius bicinctus

Banded dotterels breed mostly on lake shores and inland riverbeds (both islands). They also sometimes nest on the slopes of some ranges and inland tussock. In autumn, they migrate in large flocks to wintering places, moving to the coast and north, to the top of the South Island and the north of the North Island, and even to Australia.

South Island pied oystercatcher

Otago

Haematopus ostralegus finschi

Arrows show movements of birds to breeding areas. Note: The arrows are not the only movements of these species in New Zealand.

The South Island pied oystercatcher breeds only in the South Island, east of the Southern Alps. With the onset of winter, they migrate to all other parts of the country where they can be found in estuaries and harbours from Stewart Island to Northland. In spring they return to their breeding sites on lake shores, inland rivers and farmland.

1. For each bird species listed below, identify the sites for breeding and overwintering: (a) Wrybill breeding: Wrybill overwintering:

(b) Pied stilt breeding:

Pied stilt overwintering: (c) SI pied oystercatcher breeding:

SI pied oystercatcher overwintering:

(d) Banded dotterel breeding:

Banded dotterel overwintering:

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2. Describe the adaptive advantage of the migrations from breeding areas to overwintering areas:

3. Describe a possible cost to the birds of annual migration:

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10 Migratory Navigation in Birds birds must know their flight direction and when they have reached their destination (goal). Cues include star and solar cues, landscape features, wind direction, polarised light, magnetic and gravitational field information, and smell.

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Key Idea: Migratory birds use a wide range of environmental cues to navigate accurately and determine their destination. Navigation is the process by which an animal uses various cues to determine its position in reference to a goal. Migrating Sun compass

A

Experiments have been carried out to investigate the existence of a sun compass and its importance for daytime migrations. Caged birds were placed in circular enclosures with four windows. Mirrors were used to alter the angle at which light entered the enclosures. At migration time, in natural conditions, these birds clearly showed a preferred flight direction (A). When mirrors bent the Sun's rays through 90°, the birds turned their preferred direction (B and C).

B

Sunlight

C

Sunlight

Sunlight

Blind

Sunlight

Sunlight

Blind

Sunlight

Blind

Sunlight

Blind

Sunlight

Sunlight

Blind

Blind

Mirror

Original orientation

After two nights

Mirror

Mirror

After three nights Mirror

mN

Magnetic compass

An experiment to investigate the existence of a magnetic compass in migratory birds used magnetic coils to mimic the Earth’s magnetic field. The birds detect magnetic north, the direction of their spring migration. When the magnetic field was twisted so that north was in the east-southeast position, the birds kept their original path for the first two nights. By the third night, they had detected the change and altered their path accordingly.

mW

mS

Original orientation

Mirror

After two nights

mW

mS

After three nights

Mirror

mN

mW

Original orientation

mE

mW

mS

After two nights

mW

mS

After three nights

mN

mW

mE

mW mN

mS mE

mW mN

mS mE

mS

mW

mE

Real sky

mS North

An experiment to investigate the use of star positions in the night sky used an ink pad at the base of a cone of blotting paper. Nocturnal migrants flutter in their preferred direction of travel as the amount of ink shows. In a planetarium that projected the real sky, indigo buntings located the Pole Star and used it to find north, the direction of their spring migration. When the sky in the planetarium was rotated 90° counter-clockwise the birds altered their direction accordingly. Simulating a cloudy night, the obscured sky confused the birds.

mN

Sky rotated 90°

mE

mN

Sky obscured

North

mE

Real sky

Star compass

mE

mS North

North

mN

mE

mN

Sky rotated 90°

Sky obscured

North

North

Real sky

Sky rotated 90°

Sky obscured

North

North

North

(a) Sun compass:

(b) Star compass:

(c) Magnetic compass:

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1. The experiments above investigated three possible compass mechanisms used by migratory birds to navigation. Summarise the results of each experiment, and state whether or not the experiment provided evidence that the birds were using the compass mechanism:

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Navigation and migration in starlings and blackcaps

West European birds

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Normal wintering area

a

rm

No

no

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re l di

ion

rat

ig fm

Starling

Adu

lts

East European birds

Birds moved by plane

Direction of travel of hybrids

Switzerland

s

ile

en

v Ju

The Netherlands

Blackcap

European starling migration

An experiment with starlings investigated the roles of genetics and experience in navigating during migration. Birds caught in the autumn leg of their migration were captured in the Netherlands and taken to Switzerland and released. The juveniles, which had not migrated before, flew to Spain. The more experienced birds reached their winter homes in France, Britain, and Ireland.

Blackcap migration

Blackcaps are divided in their migration paths. Birds breeding in eastern Europe fly via Turkey to eastern Africa. Those from western Europe fly across the Strait of Gibralta to north Africa. In an experiment to test the genetic component of their migratory navigation, birds from both populations were bred together. The hybrids flew south on a course taking them over the Alps and the widest part of the Mediterranean.

2. Birds that use a sun compass to navigate rely on the position of the Sun in the sky as a reference point to determine north. Because the earth rotates on its axis once a day, the position of the Sun in the sky is constantly changing. Describe an essential mechanism that the birds must have in order to make use of this type of compass:

3. Study the information on the European starling migrations above and the answer the following: (a) What direction did the juvenile starlings fly once they were relocated?

(b) How is this different to the experienced birds?

(c) How might innate and learned behaviour account for these differences?

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4. Study the information on the blackcap migrations above and the answer the following: (a) What do you notice about the migration pattern of the hybrid blackcaps?

(b) What does this tell you about the origin of the migration pattern?

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11 Cuckoo Migrations They both have their breeding season in New Zealand or Australia during the southern summer, parasitising the nests of smaller songbirds such as warblers and yellowheads, which breed at the same time. They migrate north in autumn to wintering grounds in the tropical Pacific.

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Key Idea: The shining cuckoo and long-tailed cuckoo are land birds that make annual migrations between temperate breeding grounds and more tropical overwintering grounds. The long-tailed cuckoo and the shining cuckoo are New Zealand’s only forest birds that migrate out of the country.

Caroline Islands

Papua New Guinea

Marshall Islands

Bismark Archipelago

Marquesas

Solomon Islands

Sunda Islands

Fiji

Tubai Is.

Australia

New Zealand

Breeding grounds

Chatham Islands

1000 km

Shining cuckoo Chrysococcyx lucidus

Long-tailed cuckoo Eudynamys taitensis)

Called the bronze shining cuckoo in Australia. The eastern portion of the Australian population migrates to New Guinea while those from south-western Australia migrate to the Sunda Islands in Indonesia.

Breeds in New Zealand parasitising the nests of whiteheads and yellowheads. Migrates to islands of the tropical Pacific including the Caroline Is., Marshall Is., Marquesas Is., and Tubai Is. The main wintering area is between Fiji and Tahiti to the east.

Called the shining cuckoo or Pipiwharauroa in New Zealand. Breed in New Zealand (including the Chatham Islands) where the birds parasitise the second laid clutches of warblers The birds migrate to the Solomon Islands and the Bismark archipelago.

Shining cuckoo

1. On the map above, draw labelled arrows from New Zealand and Australia to the islands mentioned for each cuckoo. 2. Use the scale on the diagram to determine the maximum distance covered by each cuckoo species in their migration from New Zealand to the islands in the South Pacific. Check your measurement on nz.mapometer.com if you wish. (a) Long-tailed cuckoo:

km

(b) Shining cuckoo (New Zealand population):

km

(c) Shining cuckoo (Australian population:

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km

3. What method(s) of navigation would the birds be likely to use during this migration. Explain your answer:

4. Describe the adaptive advantages to these birds of making such a risky and demanding long distance migration:

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12 Sun Compass Navigation

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Key Idea: The position of the Sun is an important navigational cue for many animals including insects such as bees and ants. Honeybees navigate using a sun compass, so honeybees communicate the direction and distance to food relative to the

current position of the Sun. In the waggle dance, they adjust their dance to account for the changing direction of the Sun. Animals that see polarised light can detect the plane of light in the sky even if the Sun itself is obscured from view.

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The honeybee waggle dance

Position of the Sun

The vertical axis of the honey comb equals the current position of the Sun.

Food source

40°

Movements of the bee to the left and right of the vertical axis give the angle of the food relative to the Sun. In this case the food source is 40° to the right of the Sun.

In bee hives, the combs hang vertically.

Other bees will be in close attendance to monitor the dance and learn the location of the new food source.

If the bee moves directly up the comb, it means the food source is directly in line with the Sun.

The duration and speed of the waggle indicates how close the food source is.

Bees communicate the direction and distance of the food source through the waggle dance (above). If food is located directly in line with the Sun, the communicator (bee in the blue circle) demonstrates it by running directly up the comb. To direct bees to food located either side of the Sun, the bee introduces the corresponding angle to the right or left of the upward direction into the dance. Bees adjust the angles of their dance to account the changing direction of the Sun throughout the day. This means directions to the food source are still correct even though the Sun has changed positions.

Polarised light navigation in ants

Direction of travel by ants

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Saharan silver ant (Cataglyphis bombycina)

90

Polariser in place

Angle turned by ant (°)

Training under clear blue sky

30

Polariser 50° left

Polariser 50° right

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An experiment investigated the effect of polarised light on navigation in Cataglyphis ants by placing a food source at a regular location near a nest. The ants learned its location and moved directly to the food source each foraging trip. A polarising screen was then placed over the ant trail. Rotating the screen caused the ants to follow a path at an angle equal to that which the polarised screen was rotated (right).

120

Direction of polarised light

60

90 30 Polariser angle (°)

60

120

The direction of travel by the ants is equal to the angle of rotation of the polarised screen.

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19 1. Name the environmental reference used by honey bees to orientate for navigation:

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2. (a) Explain how a honey bee communicates the location of a food source to other honey bees in the nest:

(b) Explain the adaptive value of this behaviour:

3. Explain how the bee compensates for the time it takes between finding the food and delivering its message to the hive:

4. What environmental cue do ants use to navigate?

5. What was the effect of rotating the plane of polarised light on the ants' ability to navigate to the food source?

6. Diagram A below shows the foraging and return trips of a Cataglyphis ant under blue sky. On diagrams B and C draw in the line of the return trip of the ant when a polarised screen is placed over the ant: Food source

Food source

Food source

Foraging trip

Foraging trip

Return trip

Nest

Foraging under clear blue sky

B

Foraging trip

C

Nest

Polarised screen placed over ant and rotated 25° to the right.

Nest

Polarised screen placed over ant and rotated 45° to the left.

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A

7. Explain why animals that can detect polarised light (e.g. ants and bees) can continue to navigate accurately when the Sun is obscured from view (e.g. a partially cloudy day).

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13 Homing Behaviour in Insects although navigation is involved in both behaviours. Homing behaviour often relies on the recognition of familiar landmarks, especially where the distances involved are relatively short. Navigation, often assisted by the use of trail pheromones, is also involved in the foraging behaviour of many insects.

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Key Idea: Homing is the ability of an animal to return to its home site after being displaced and it involves navigation. In many insects, homing is important in increasing foraging efficiency because it reduces energy expenditure. Homing (returning to a home site) is distinct from migration,

The beewolf (Philanthus) digs a nest in sand. It is a predator of bees and captures and paralyses bees as food for its larvae during development. The paralysed bee is taken back to the wasp's underground nest, where the wasp lays its eggs in the still living body. In a well-known experiment to test the homing behaviour of this wasp, a scientist named Tinbergen, carried out a 2-step experiment. (After Tinbergen, 1951. The Study of Instinct. Oxford University Press, London)

Wasp

Beewolf

Prey (bee)

Wasp

Philanthus triangulum

Pine cones

Nest

Pine cones

Nest

Step 1: Orientation flight

While a female wasp was in the burrow, Tinbergen placed a circle of pine cones around the nest entrance. When she emerged, the wasp reacted by carrying out a wavering orientation flight before flying off.

Step 2: Return flight

During her absence, the pine cones were moved away from the burrow leading to the nest. Returning to the nest with prey, the wasp orientated to the circle of pine cones, not the nest entrance.

Homing in ants

Cataglyphis desert ants use polarised light to navigate while foraging, often pausing and turning 360° to apparently note the position of the Sun and plane of light. When they discover a food source, they return directly to the nest as shown right. This ability to determine the direction to the nest reduces travel time when returning to the nest, making foraging more efficient.

Foraging trip

Food source

Return journey

Nest

Cataglyphis ants collect a beetle

2. (a) After a foraging trip, a Cataglyphis ant was displaced to another point some distance away. On the diagram shown right, draw in a line indicating the direction the ant travelled when released:

(b) Explain why the ant moved in the direction you drew:

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1. Why did moving the pine cones around the wasp nest result to the wasp being unable to find the nest?

Ant released at this point

Foraging trip

Ant captured at food source

Nest

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Homing and navigation in wasps


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14 Homing in Salmon sea where they grow to maturity. When ready to spawn, they return to the river they left as juveniles. Travelling hundreds of kilometres in the open ocean, they locate their home river and swim upstream to spawn in the same tributary in which they were hatched. Their navigation from the open ocean may involve using the Earth’s magnetic field or polarised light. Once close to their homeland coast, they rely on smell to detect the unique odour of their home river.

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Key Idea: King (chinook) salmon migrate as adults from the ocean to headwaters to spawn, possibly using magnetic fields, polarised light, and scent to help navigate to the river in which they were spawned. King salmon (Oncorhynchus tshawytscha) are anadromous, meaning they migrate from the sea to fresh water to spawn. Salmon possess one of the most remarkable homing instincts of any animal. Young fish travel from the river of their birth to

Tasman Sea

Some incidence of straying by salmon into the Ohinemaka drainage.

iver

aka R

Hall River

Immature salmon spend varying periods (up to 3+ years) in Lake Paringa before completing the marine phase of their life cycle. Eventually the young fish migrate to the Tasman Sea as smolts.

Pa rin

ga

6 y wa k a iti k Ho To

gh Hi

Ri ve r

Lake Paringa

Ri

ba g

way 6 To Ha as t

ve r

Hig h

W ind

Salmon moving upstream to spawn congregate in the lake off the Windbag River mouth while developing to sexual maturity.

Salmon enter the mouth of the Paringa River and move into Lake Paringa via the Hall River.

em Ohin

King salmon (Oncorhynchus tshawytscha) occupy the Paringa River drainage on the west coast of the South Island. The Lake Paringa salmon stock includes both landlocked (nonmigrating) and anadromous individuals.

Out-migrant salmon live and grow to maturity in coastal water to the north and south of Paringa drainage.

Area enlarged on map to the right

Principal salmon spawning areas.

Some spawning occurs in the upper reaches of the Paringa River during years of high abundance.

(Information kindly supplied by Dick Hutchinson, Dept. of Conservation)

1. (a) Describe the mechanism salmon use to return to the stream where they hatched:

(b) Using the map above, describe the evidence indicating that this method of navigation is not foolproof:

(c) Describe the adaptive advantage of returning to the natal stream to spawn:

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2. Salmon may be removed (as eggs or fry) from their stream of origin and farm reared before being released to grow at sea. These fish generally fail to return to their natural headwaters to breed. Suggest why these fish do not return:

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15 Plant Responses mainly through changes in patterns of growth. These responses may involve relatively sudden physiological changes, as in flowering, or a steady growth response, such as a tropism. Many of these responses involve annual, seasonal, or circadian (daily) rhythms.

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Key Idea: Plants generally respond to their environment by growing to or away from a stimulus or by responding in a way that affects some physiological process. Even though most plants are firmly rooted in the ground, they can still respond to changes in their external environment, Life cycle responses

Tropisms

Plants use seasonal changes (such as falling temperatures or decreasing daylength) as cues for starting or ending particular life cycle stages. Such changes are mediated by plant growth factors, such as phytochrome and gibberellin, and enable the plant to avoid conditions unfavourable to growth or survival. Examples include flowering, dormancy and germination, and leaf fall.

Tropisms are growth responses made by plants to directional external stimuli, where the direction of the stimulus determines the direction of the growth response. A tropism may be positive (towards the stimulus), or negative (away from the stimulus). Common stimuli for plants include light, gravity, touch, and chemicals.

Rapid responses to external stimuli

Plants are capable of quite rapid responses. Examples include the closing of stomata in response to water loss (below), opening and closing of flowers in response to temperature, and nastic responses. These responses may follow a circadian rhythm and are protective in that they reduce the plant’s exposure to abiotic stress or grazing pressure.

Plant competition and allelopathy Although plants are rooted in the ground, they can still compete with other plants to gain access to resources. Some plants produce chemicals that inhibit the growth of neighbouring plants. Such chemical inhibition is called allelopathy. Plants also compete for light and may grow aggressively to shade out slower growing competitors.

Plant responses to herbivory

h Stan S

ebs

0 3. cc

Many plant species have responded to grazing or browsing pressure with evolutionary adaptations enabling them to survive cropping or deter browsers. Examples include rapid growth to counteract the constant loss of biomass (grasses), sharp spines or thorns to deter browsers (acacias, cacti), or toxins in the leaf tissues (eucalyptus).

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1. Identify the stimuli plants typically respond to:

2. Describe the adaptive advantage of a plant responding appropriately to the environment:

3. Describe one adaptive response of plants to each of the following stressors in the environment:

(a) Low soil water:

(b) Falling autumn air temperatures:

(c) Browsing animals:

(d) Low air temperatures at night:

KNOW

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16 Tropisms growth response. Tropisms are identified according to the stimulus involved, e.g. photo- (light), gravi- (gravity), hydro(water), and are identified as positive (towards the stimulus) or negative (away from the stimulus). Tropisms act to position the plant in the most favourable growth environment.

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Key Idea: Tropisms are directional growth responses to external stimuli. They may be positive (towards a stimulus) or negative (away from a stimulus). Tropisms are plant growth responses to external stimuli, in which the stimulus direction determines the direction of the

(a)........................................................

A positive growth response to a chemical stimulus. Example: Pollen tubes grow towards a chemical, possibly calcium ions, released by the ovule of the flower.

Plant growth responses are adaptive in that they position the plant in a suitable growing environment, within the limits of the position in which it germinated. The responses to stimuli reinforce the appropriate growth behaviour, e.g. roots grow towards gravity and away from the light.

(b)......................................................... Stems, grow away from the direction of the Earth's gravitational pull. Coleoptiles (the sheath surrounding the young grass shoot) show the same response.

(c).......................................................... Growth response to water. Roots are influenced primarily by gravity but will also grow towards water.

(d).......................................................... Growth responses to light, particularly directional light. Coleoptiles, young stems, and some leaves show a positive response.

Root mass in a hydroponically grown plant

Tendril wrapping around twig

(e)..........................................................

(f)........................................................... Growth responses to touch or pressure. Tendrils (modified leaves) have a positive coiling response stimulated by touch.

Germinating pollen

Kristian Peters

Roots respond positively to the Earth's gravitational pull, and curve downward after emerging through the seed coat.

Thale cress bending to the light

2. Describe the adaptive value of the following tropisms:

(a) Positive gravitropism in roots:

(b) Positive phototropism in coleoptiles:

(c) Positive thigmomorphogenesis in weak stemmed plants:

(d) Positive chemotropism in pollen grains:

3. Explain the adaptive value of a tropism:

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1. Identify each of the plant tropisms described in (a)-(f) above. State whether the response is positive or negative.

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17 Investigating Phototropism because coleoptiles are different to stems. However their conclusions have been shown to be valid. Auxins (a group of plant hormones) promote cell elongation and are inactivated by light. Thus, when a stem is exposed to directional light, auxin becomes unequally distributed either side of the stem. The stem responds to the unequal auxin concentration by differential growth, i.e. it bends. The mechanisms behind this response are now well understood.

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Key Idea: Experimental evidence supports the hypothesis that auxin is responsible for tropic responses in stems. Phototropism in plants was linked to a growth promoting substance as early as the 1920s. Early experiments investigating phototropism in severed coleoptiles provided evidence for the hypothesis that the plant hormone auxin was responsible for tropic responses in stems. These experiments (outlined below) have been criticised as being too simplistic

1. Directional light: A pot plant is exposed to direct sunlight near a window and as it grows, the shoot tip turns in the direction of the Sun. When the plant was rotated, it adjusted by growing towards the Sun in the new direction.

Directional sunlight

Less light

(a) What hormone regulates this growth response?

More light

Shoot grows in the direction of sunlight

A

B

(b) What is the name of this growth response?

Growing shoot of plant

(c) How do the cells behave to bring about this change in shoot direction at:

Point A?

Draw your cells here:

Point B?

(d) Which side (A or B) would have the highest hormone concentration and why?

(e) In the rectangle on the right, draw a diagram of the cells as they appear across the stem from point A to B.

2. Light excluded from shoot tip: When a tin-foil cap is placed over the top of the shoot tip, light is prevented from reaching the shoot tip. When growing under these conditions, the direction of growth does not change towards the light source, but grows straight up. State what conclusion you can come to about the source and activity of the hormone that controls the growth response:

Directional sunlight

Foil cap

A

B

3. Cutting into the transport system: Two identical plants were placed side-by-side and subjected to the same directional light source. Razor blades were cut half-way into the stem, thereby interfering with the transport system of the stem. Plant A had the cut on the same side as the light source, while Plant B was cut on the shaded side. Predict the growth responses of:

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Growing shoot of plant

Directional sunlight

A

Plant A:

B

Growing shoot of plant

Razor blade left in cut

Plant B:

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18 Investigating Gravitropism Key Idea: Auxin appears to have a role in the gravitropic responses of roots, but its effect may depend on the presence of other plant growth regulators. The importance of auxin as a plant growth regulator, as well as its widespread occurrence in plants, led to it being proposed as the primary regulator in the gravitropic response.

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The basis of auxin’s proposed role in gravitropism is outlined below. The mechanism is appealing in its simplicity but has been widely criticised because of the use of coleoptiles. The coleoptile (the sheath surrounding the young grass shoot) is a specialised, short-lived structure and is probably not representative of plant tissues generally.

The role of auxins in gravitropic responses

Gravity

Gravity ity

Auxin moves to the lower side. The cells on the lower side elongate in response to auxin and the stem turns upward.

A horizontally placed root (radicle) tip grows downwards. This is positive gravitropism.

Experiments on isolated shoot tips provide evidence that gravitropism (like phototropism) is due to different growth rates of upper and lower sides of the stem or root in response to the redistribution of auxin. In a horizontally placed shoot tip (right), more auxin accumulates on the lower side than on the upper side. In stems, this causes elongation of the cells on the lower surface and the stem tip turns up. The root grows down because root elongation is inhibited by high levels of auxin on the lower surface (graph below).

Agar block 33% auxin

Barrier

Agar block 67% auxin

Horizontal shoot tip

150

Auxin concentration and root growth

100

In a horizontally placed seedling, auxin moves to the lower side in stems and roots. The stem tip grows upwards and the root tip grows down. Root elongation is inhibited by the same level of auxin that stimulates stem growth (graph left). The higher auxin levels on the lower surface cause growth inhibition there. The longest cells are then on the upper surface and the root turns down.

Promotion

The auxin concentrations that enhance stem growth inhibit the growth of roots

Inhibition

Elongation of or gain in response to auxin (percent)

A horizontally placed stem tip grows upwards. This is negative gravitropism.

0

Stems

Roots

10-5

10-3

10-1

-1

101

Increasing concentration of auxin (mg lL , log10 scale)

103

This simple explanation for gravitropism has been criticised because the concentrations of auxins measured in the upper and lower surfaces of horizontal stems and roots are too small to account for the growth movements observed. Other studies indicate that growth inhibitors may interact with auxin in gravitropic responses.

(a) Shoots (stems):

(b) Roots:

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1. Explain the mechanism proposed for the role of auxin in the gravitropic response in:

2. (a) From the graph above, state the auxin concentration at which root growth becomes inhibited: (b) State the response of stem at this concentration: 3. Explain why the gravitropic response in stems or roots is important to the survival of a seedling:

(a) Stems:

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19

Investigating Gravitropism in Seeds way in which to investigate gravitropism in seedlings. Using the information below, analyse results and draw conclusions about the effect of gravity on the directional growth of seedling roots.

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Key Idea: The effect of gravity on the direction of root growth can be easily studied using sprout seeds. The direction of root growth will change if the seedling's orientation is altered. The experiment described below is a simple but effective

The aim

To investigate the effect of gravity on the direction of root growth in seedlings.

Results

The students took photographs to record changes in growth during the course of the experiment. One seedling at day 5 and 11 is shown below.

1

Hypothesis

2

Shoot beginning

Roots will always grow towards the Earth’s gravitational pull, even when the seedling's orientation is changed.

Method

Day 5, rotated 90° clockwise

A damp kitchen paper towel was folded and placed inside a clear plastic sandwich bag. Two sprout seeds were soaked in water for five minutes and then placed in the centre of the paper towel. The bag was sealed. The plastic bag was then placed on a piece of cardboard which was slightly larger than the plastic bag. The plastic bag was stretched tightly so the plastic held the seeds in place, and secured with staples to the cardboard.

The cardboard was placed upright against a wall. Once the first root from each seed reached 2 cm long, the cardboard was turned 90° degrees. Daily observations and photographs were made of the root length and direction throughout the duration of the experiment. Photos of one seedling from days 5 and 11 are shown right.

3

Shoot

Root beginning to bend down

Root

Day 5

Day 11

Photo 1: This photo was 5 five days after the seed began to germinate. Photo 2: After photo 1 was taken, the cardboard was rotated 90°.

Photo 3: This photo was taken 6 days after the seed was rotated 90°.

1. (a) What direction did the root first begin to grow in?

(b) Describe what happened to the root when the students rotated the cardboard 90°:

(c) Explain why this occurred:

(d) Predict the result after six more days growth if the students rotated the seedling in photo 3 90° clockwise. Draw your answer in the space right:

2. During the course of the experiment a shoot developed.

(a) In what direction did the shoot grow at first?

(b) In what direction did the shoot grow after rotation 90° (photo 3)?

(c) Why did this occur?

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20 Nastic Responses Nastic responses can occur in response to temperature (thermonasty), light (photonasty), or touch (thigmonasty). Plant 'sleep movements', in which flowers close or leaves droop at night, are specialised diurnal photonasties. The mechanisms involved in Mimosa's thigmonasty (below) are also responsible for the leaf movements of the Venus flytrap.

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Key Idea: Nastic responses are plant responses in which the direction of the plant response is independent of the stimulus direction. They are reversible and often rapid movements. Nastic responses in plants are independent of the stimulus direction and may involve quite rapid, reversible movements, often resulting from localised changes in turgor.

Movements of the sensitive Mimosa plant

ffThe sensitive plant (Mimosa pudica) has long leaves composed of small leaflets. When a leaf is touched, it collapses and its

leaflets fold together. Strong disturbances cause the entire leaf to droop from its base. This response takes only a few seconds and is caused by a rapid loss of turgor pressure from the cells at the bases of the leaves and leaflets.

ffThe message that the plant has been disturbed is passed quickly around the plant by electrical signals (changes in membrane

potential) not by plant hormones (as occurs in tropisms). The response can be likened to the nerve impulses of animals, but it is much slower. After the disturbance is removed, turgor is restored to the cells, and the leaflets slowly return to their normal state.

Leaflet

Leaf

Thin walled parenchyma cells specialised as motor cells.

Leaf

Leaflets

Epidermis

Cells on the upper and lower surfaces are turgid

RCN

Unstimulated leaf

Vascular tissue

Pulvinus

The leaves of Mimosa have joint-like thickenings, the pulvini (sing. pulvinus) at the bases of the petioles and at the bases of each leaflet. The pulvini contain specialised motor cells, which are involved in the rapid leaf movements.

. .

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K+

K+

H2O

RCN

Epidermis

Disturbed leaf

Cells on the lower surface lose turgor and the leaf collapses.

When disturbed, a change in membrane potential of the leaf cells is transmitted to the cells of the pulvinus. These cells respond by actively pumping potassium ions out of the cytoplasm (see inset above). Water follows osmotically and there is a sudden loss of turgor.

Leaflet base

Leaflet Leaf axis

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This mechanism also operates at the leaflet bases, except that the cells on the upper surface of the pulvinus lose turgor, and the individual leaflets fold up, rather than down (left).

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28 Sleep movements in plants

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Lazaregagnidze

Day

Night

Thigmonastic responses in carnivorous plants

Some small, specialised plants obtain most of their nitrogen (but not their energy) from trapping and digesting small animals such as insects. This allows them to grow in nutrient-poor (particular low nitrogen), high light environments, such as acidic bogs and rocky outcrops.

Venus flytrap (Dionaea)

Sundew (Drosera)

When an insect touches the hairs on a leaf of a Venus flytrap (right), the two lobes of the leaf snap shut, trapping the insect. Once the insect has been digested, the empty leaves reopen. The hairs on the leaf must be touched twice in quick succession for the leaf to close. This means false alarms, such as a twig falling onto the leaf, do not set it off.

Sundews also show a thigmonastic response. An insect landing on a leaf quickly becomes trapped in the sticky hairs. The hairs fold around the insect and in some species the leaf may curl over, completely enclosing the insect. Carnivory has evolved independently nine times in five different orders of plants.

1. Identify the type of nasty involved in each of the following examples:

(a) Opening and closing of tulip flowers to changes in air temperature:

(b) Opening of evening-primrose flowers at dusk:

2. How is a nastic response different from a tropism?

3. (a) Describe the basic mechanism behind the sudden leaf movements in Mimosa:

(b) Explain how the movements of the Mimosa pudica help its survival:

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4. How could the sleep movements of plants (lowering the leaves at night) benefit a plant?

5. (a) How does the Venus flytrap ensure the closing of the trap is not falsely triggered?

(b) Describe how carnivory benefits this plant in its habitat:

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Orikrin1998

Many plants show movements in relation to light and dark. Oxalis (right) spreads it leaves out during the day to capture sunlight. During the night the leaves are lowered and bend slightly along the midline. This helps to prevent dew accumulating on the leaf and minimises the risk of damage while the leaf is not being used to capture light.


21 What You Know So Far: Orientation in Space Homing and migration

HINT: Include a definition as well as reference to navigation and the benefits and costs of migration.

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you:

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Taxes and kineses

HINT: Be sure to include definitions, adaptive value, and examples of both types of responses.

Nastic responses

HINT: Include definitions and explain the mechanisms of phototropism and gravitropism.

HINT: How do nastic responses differ from tropisms? What is their purpose?

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Tropisms

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22 NCEA Style Question: Migration Sooty shearwater The sooty shearwater (Puffinus griseus, muttonbird or titi) migrates up to 65,000 km. It is one of the longest migrations of any animal. From October to March, sooty shearwaters raise their chicks (which takes about 100 days) on oceanic islands around the sub-Antarctic region of New Zealand. During the breeding season, tens of thousands of chicks are taken by commercial hunters. From April to May, they begin migrating to specific areas of the sub-Arctic, arriving from June to July for the Northern Hemisphere summer. The sooty shearwater is often seen behind fishing trawlers picking up scraps.

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Position of birds vs ocean productivity 0.9 0.8

60 Position 40 of birds 20 North Pacific 0

-20 -40

South Pacific

-60

Breed

Migration

Breed

0.7 0.6 0.5 0.4 0.3 0.2 0.1

Trade winds of Pacific Ocean

Productivity of oceans (g C m-2 d-1)

Latitude

Flight of two sooty shearwaters

J FM A M J J A S O N D J Month

1. Discuss the migratory behaviour of the sooty shearwater as it travels from sub-Antarctic waters to sub-Arctic waters (you may use extra paper if needed).

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• Explain why it would undertake such a long migration • Explain some of the methods it may be using to navigate • Suggest reasons why its numbers have been dropping

2. Suggest why the sooty shearwater begins its return journey in October when North Pacific Ocean productivity is greater than South Pacific Ocean productivity.

TEST

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23 NCEA Style Question: Plant Responses

Chriwick Chap CC 3.0

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1. Etiolation is a condition in plants caused by growth in the absence of light. The stem becomes long and thin, the leaves are yellow in colour, and the cells are elongated with weak cell walls. The photo below shows an etiolated plant on the left, next to a plant grown in normal sunlight on the right.

(a) Identify the plant hormone responsible for etiolation:

(b) Explain how etiolation occurs and discuss how it acts a survival mechanism for plants (you may use more paper if required):

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24 KEY TERMS AND IDEAS: Orientation in Space 1. (a) What is the name given to a plant growth response to directional light? (b) What is the name given to a plant growth response to gravity?

(c) What is the name given to a plant response that is independent of stimulus direction?

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(d) What plant hormone is principally responsible for the phototropic effect?

2. (a) The honeybee waggle dance communicates the location of a food source based on: star compass navigation / local geography and landmarks / sun compass navigation (delete two)

(b) The honeybee round dance communicates that a food source is close by. Does it also communicate direction? Y / N (a) What responses are being shown by the orchid in the photo (left):

(b) What is the stimulus involved?

(c) How are these responses adaptive?

Tangopaso CC 3.0

3.

4. Match the following words with their definitions: dispersal

A

Animal orientation and movement in response to a directional stimulus.

kinesis

B

The process of using environmental cues to determine position in reference to a goal.

migration

C

A one-way movement away from an area in response to environmental change.

D

A plant growth response to a directional external stimulus.

E

The long distance movement of animals from one region to another, usually seasonally.

F

A non-directional animal orientation response in which the speed or movement or rate of turning is proportional to stimulus intensity.

navigation taxis

tropism

The photo (left) shows swarming behaviour in locusts:

(a) What event is likely to be occurring here?

(b) What distinguishes this behaviour from a migration?

(c) What is the likely cue for this behaviour?

(d) How is this response adaptive?

TEST

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5.

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25 Astronomical Cycles Key Idea: The motions of the Earth, Moon, and Sun result in complex, interdependent cycles, creating environmental changes that range from short term (a few hours) to long term (many hundreds of days). Cosmic forces, such as the movement of the Moon around the Earth and the Earth and planets around the Sun generate

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predictable environmental cycles such as day and night and the seasons. These cycles provide cues that enable many organisms to time important events in their lives, such as foraging activity, breeding, and migration. The tidal cycle is not shown on the diagram below, but involves the gravitational pull of the moon as well as centrifugal forces on the oceans.

Solar year

The journey around the Sun takes 365.25 days. The regularity of this motion acting jointly with the angle of the Earth's axis produces the regular changes in the seasons. Northern hemisphere winter solstice

December 21

Northern hemisphere summer solstice

June 21

SUN

MOON

Southern hemisphere summer solstice

Southern hemisphere winter solstice

EARTH

Lunar month

Earth day

Earth's axis

The Moon's orbit around the Earth produces tides. High tides are slightly more than 12 hours apart (as are low tides). This regularity synchronises tidal rhythms in marine organisms. The time between full moons is 29.5 days and many organisms synchronise rhythms with this lunar cycle.

Every 24 hours, the Earth completes one rotation with respect to the Sun. This rotation produces the daily light-dark cycle experienced on Earth.

The Earth does not spin upright; it has a 23.5° tilt. This tilt always faces the same way, resulting in seasonal changes in sunlight and weather.

1. For each of the following astronomical cycles, identify the environmental cue they produce and the period of the cycle:

(a) Earth orbiting the Sun:

Cue:

(b) Moon orbiting the Earth:

Cue:

Period:

Period:

(c) Earth spinning on its axis: Cue:

Period:

(a) Winter months:

(b) Summer months:

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2. Organisms living well away from the equator (i.e. closer to the North or South pole) experience different lengths of daylight during different seasons. Describe the position of the Earth’s South pole (southern axis) during New Zealand’s:

3. Environmental cues often take the form of predictable cycles. Predict the role of environmental cues in biological rhythms, and how they might influence plant and animal responses:

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26 Biological Clocks (endogenous rhythms) will continue even in the absence of environmental cues, although the period (duration) of the rhythm may be slightly different to the environmental rhythm. Biological clocks have an adaptive function, such as helping anticipate environmental changes and preparing the body for the activities that will predictably follow.

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Key Idea: A biological clock is the endogenous timing system an organism uses to synchronise its activities with the external environment. A biological clock is an endogenous (internal) timing system that helps to control the physiological responses and activities of an organism. Rhythms established by the biological clock

Where is the biological clock located?

The pineal gland secretes the sleep-inducing hormone melatonin in the dark. Melatonin production is suppressed by bright light.

The location of the biological clock varies between organisms. In birds, reptiles, and amphibians it is located in the pineal gland (in the brain). In insects each cell has its own biological clock. In mammals the biological clock is located in the hypothalamus. For most humans, the biological clock runs at about a 25½ hour day. To keep it synchronised with the 24 hour-day cycle it needs to be reset each day, reacting to outside stimuli such as light and dark and meal times. The clock is made up of a collection of cells in the hypothalamus, called the suprachiasmatic nucleus (SCN), just behind the eyes. Light from the eyes stimulates the nerve pathways to the SCN and regulates its activity.

Melatonin

Eye

Once exposed to light, the suprachiasmatic nucleus (SCN) communicates with the hypothalamus and pineal gland to promote wakefulness (e.g. by raising body temperature, releasing stimulating hormones, and suppressing melatonin production.

Functions of the biological clock

The biological clock helps to control internal rhythms such as heart activity, hormone secretion, blood pressure, oxygen consumption, and metabolic rate. When the rhythms controlled by the biological clock become out-of-sync with the environment various short or long term disorders can occur, e.g. jet lag. Some functions of the biological clock are described below:

Honeybee

Gannets

Prediction of and preparation for events in the environment (e.g. storing food reserves as fat for periods of torpor or hibernation).

Synchronisation of migration, reproduction, or social activities. Animals congregate at breeding grounds at the same time of year.

Synchronising circadian and annual rhythms, e.g. basking in tuatara and other reptiles, with changes in the environment.

Time compensation in navigation and sun compass orientation using a continuously consulted clock (e.g. honeybee food collection).

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1. (a) Where is the biological clock located in mammals?

(b) What is the main stimulus that helps synchronised the biological clock with the environment?

2. Describe two functions of the biological clock and their adaptive value: (a)

(b)

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27 Biological Clocks and the Environment the internal clock is known as entrainment. Endogenous rhythms that are synchronised to specific environmental cues are adaptive, contributing to fitness by ensuring the success of critical activities such as mating, birth, germination, foraging, and periods of torpor and dormancy.

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Key Idea: External cues synchronise the biological clock with the environment. Biological clocks stay synchronised with the environment because they are regularly reset by an external environmental cue or zeitgeber. The process of resetting

A simple mechanism for biological clocks

Zeitgeber (e.g sunlight)

Entrainment (environmental cues synchronise the biological clock with the environment).

40° 39° 38° 37°

Biological clock

Output (internal mechanisms produce internal changes that match changes in the environment).

36° 35° 34°

°C

Biological rhythm (e.g. fluctuations in body temperature)

Travelling and biological clocks

Most animals travel slowly enough that their biological clock is never far out of sync with the environment and entrainment by the rising of the Sun each day can reset any variation. Travelling west-east (or east-west) in plane can result in the biological clock being severely out-of-sync with environmental cues. This phenomenon is called jet lag.

Jet lag occurs because the biological clock is responsible for regulating the natural sleep-wake cycle, which involves being awake and active during the day and sleeping at night when it is dark. Rapid, long distance air travel can lead to disruption of the normal sleep-wake cycle. When travelling across multiple time zones, the biological clock will not be synchronised with the destination time and must adjust to the new schedule.

The severity of jet lag is linked to the west–east distance travelled, rather than the length of flight.

1. (a) What is a zeitgeber?

(b) Identify a common zeitgeber in animals:

2. (a) What is entrainment?

(b) Why is entrainment important to an organism?

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3. (a) Person A travels 5000 km east in 9 hours. Person B travels 500 km east in 9 hours. Which of these people is more likely to experience jet lag?

(b) Explain you answer to (a):

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28 Biological Rhythms cues are said to be endogenous (internal). Those that are direct responses to the environment and do not persist when conditions are kept constant are called exogenous. In most cases, the rhythm is the expression of both the internal (endogenous) timing mechanism (the biological clock) and the environmental (exogenous) cue that synchronises it. Biological rhythms are adaptive in that they ensure the appropriate behaviour occurs at the appropriate time.

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Key Idea: Living organisms show regular cycles of activity that approximate cyclic events in the environment. The activity patterns of organisms often occur with frequencies that approximate the predictable cyclic events in the environment, such as the light-dark cycle and the changing of the seasons. The length of time it takes to complete the entire cycle is termed the rhythm's period, e.g. 24 hours. Rhythms that continue in the absence of external Term

Definition

Term

Definition

Endogenous

An internally controlled response

Circatidal

A rhythm that matches the movement of the tides and has a period of ~12.5 hours.

Exogenous

An externally controlled response

Circalunar

A rhythm that cycles over an approximately 29.5 day period.

Circadian

A rhythm that cycles over an approximately 24 hour period.

Circannual

An annual rhythm (one year)

Rhythm: daily

DAILY: weta

Period: ~ 24 h

Midday

Example: Weta are generally active during the night (nocturnal) when they forage in leaf litter or trees. Being active at night makes them less vulnerable to daytime predators.

Midnight

Active

Melodi2

Rhythm: tidal

Midday

TIDAL: mud crab

Period: ~ 12.4 h (coincident with tidal flows)

Midday

Example: In the New Zealand tunnelling mud crab (Helice crassa) locomotion and feeding occur at low tide. They are more active during the day than at night.

Midnight

Active

Active

High tide

Rhythm: lunar / annual

Period: ~ 29.5 days (a month) / one year

LUNAR: inanga (common galaxias)

March

Example: Inanga spawn during the months of March and April during the spring tides (new and full moons). Activity peaks 2-3 days after the new or full moon. During the spring tides they are able to lay eggs higher up river banks, which protects the eggs from aquatic predators.

April

Spring tide

ANNUAL: NZ long tailed bat

Period: ~ a year

Example: NZ long-tailed bats hibernate for 4-5 months during autumn and winter when temperatures are low and insect food is scarce.

High tide

Spring tide

December

Spring tide

May

Spring tide

July

December

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Rhythm: annual

Midday

DoC

Hibernation

Rhythm: annual

ANNUAL: sheep

Period: ~ a year

December

Example: In many domestic livestock species the reproductive cycle is timed so that young are born in spring when the weather is warmer and food is more plentiful.

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July

Mating

December

Birth

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1. (a) Contrast endogenous and exogenous components of a biological rhythm:

(b) Explain why endogenous and exogenous components are important in maintaining a biological rhythm:

(a) Circadian rhythm:

(b) Circatidal rhythm:

(c) Circalunar rhythm:

(d) Circannual rhythm:

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2. For each of the following rhythms provide a definition and example and then describe the adaptive value of the rhythm:

3. For each of the examples below, describe an environmental cue that might be used to induce or maintain the activity:

(a) Hedgehog’s hibernation in winter:

(b) Blackbird’s foraging and social behaviour during daylight:

(c) Kiwi’s activity of hunting for soil organisms at night:

(d) Coordinated flowering of plants in spring:

4. Suggest a way a scientist could discover if an organism's biological rhythm is endogenous or exogenous:

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29 Circadian Rhythms in NZ Birds are entrained to the environment by external cues, notably the 24 hour light-dark cycle. In animals (below) the circadian rhythm can be further described by the pattern of activity exhibited: diurnal (active during daylight hours), nocturnal (active at night), or crepuscular (active at dawn and dusk).

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Key Idea: A circadian (daily) rhythm is an endogenous, entrainable rhythm with a period of approximately 24 hours. Circadian rhythms are endogenous rhythms with a period of about 24 hours. They are common in all types of organisms and, although they are endogenous and self-sustaining, they Midday

Afternoon

Midnight

Midday

Dusk

Dawn

Day

Night

Morning

Day

(a)

Active

Active

(b)

Active

(c)

Active

Usually less active

Active

Kokako Callaeas cinerea

This endangered species inhabits the native forest canopy. Kokako are poor fliers and move around mainly by running and hopping along branches or gliding between trees. It is a daylight forager, using vision to locate insects, ripe berries, and young leaves. Midnight

Dawn

Dusk

Afternoon

Rogan Colbourne

Day

Morning

Night

Quiet: Preening and inspecting feeding areas.

Day

Sleeps during the night

Major feeding activity 3-4 hours

Territory call 30 minutes

Territory call 30 minutes

Brown kiwi Apteryx australis

Brown kiwi inhabit bush and scrub in the North Island and high rainfall forests in the South Island. They are nocturnal feeders, eating worms, insects, and freshwater crayfish. Their eyesight is poor and they are reliant on a keen sense of smell and hearing, exploiting a rich source of food not available to most diurnal birds. Midnight

Afternoon

Dawn

Dusk

Day

F&B

Sleep in burrow during the day

Source: Rick Thorp, Dept. of Conservation, Hamilton

Night

Day

Feeding with occasional calls to locate mate.

Male calling at dusk, female responding (lasts about 3 hours).

Morning

Sleep in burrow during the day

Seek burrow just before dawn

2. What type of rhythm and activity pattern is displayed by the kokako?

3. What type of rhythm and activity pattern is displayed by the brown kiwi?

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1. On the diagram at the top of the page, identify the activity patterns (a-c) as diurnal, nocturnal, or crepuscular.

4. What features of the kokako's biology and environment might have been important in the evolution of its activity pattern?

5. (a) What advantage does the kiwi's activity pattern offer?

(b) An organism's activity pattern is one aspect of an organism's niche and the result of selection pressures on the species over time. Describe an adaptation of the brown kiwi that is associated with its particular activity pattern:

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39

30 Human Biological Rhythms

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Key Idea: Humans exhibit a number of periodic changes in behaviour or physiology that are generated and maintained by a biological clock.

In humans, many physiological activities exhibit a circadian, circalunar, or circannual rhythm (below). These rhythms are endogenous, but are entrained by the environment.

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Selected human daily rhythms

Daily rhythms

General

Blood alcohol level

Body temperature

Blood pressure (diastoic) Cell divisions in skin

Brain waves (total EKG) Memory test (speed)

Adding numbers (speed)

Awake

Fifty metre sprint

Midnight

Asleep

Blood content Red cell count

White cell count Glucose Insulin

Prolactin Calcium Sodium

Potassium

Rhythmic peak and variability

12 noon

6 pm

12 midnight

6 am

Percentage of women beginning labour

Testosterone

6 am

Noon

Midnight

6 4 2

Time of labour onset The graph above shows the percentage of 200,000 women who began labour at each hour of the day. If labour were equally likely to begin at any hour, then 1/24 of the women (~4%) would have begun each hour.

Monthly rhythms in women

Percentage difference from daily mean

Body temperature Heart rate Reaction time Pupil size

Blood content

Red cell count White cell count Progesterone (hormone)

Saliva content Sodium Potassium

15

Births Deaths

0

-15 Midnight

One menstrual cycle (number of days varies with individual)

Noon

Midnight

Daily rhythms of birth and death The timing of births and deaths shows daily fluctuation. The graph shows how they vary in frequency compared to a daily mean.

Annual rhythms in Southern Hemisphere

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General

Midnight

8

Midnight

General

Noon

Changes in susceptibility to alcohol The liver’s ability to metabolise alcohol is best between 4 pm and 11 pm (the ‘cocktail hour’). After midnight, the liver’s activity slows down and alcohol starts to accumulate in the blood.

37.5

Body temperature

Body temperature (°C)

Blood pressure Beard growth

Death from disease Suicide

Blood content White cell count Cholesterol

37.0

36.5 Midnight

Testosterone Prolactin

Jan Feb Mar Apr May Jun Jul Source: Cycles of Nature - An introduction to Biological Rhythms; Ahlgren, A. and Halberg, F.

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Aug Sep Oct Nov Dec

Months of the year

Noon

Midnight

Body temperature Body temperature shows endogenous fluctuation. Data for the graph above was taken from volunteers lying in bed.

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Body temperature (°C)

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Rhythms in a long duration cave occupation A woman spent four months isolated underground in a cave so that her biological rhythms could be studied in the absence of the normal day/night environmental cues. The air temperature inside the cave remained constant over this time. Her body temperature was measured 3 times a day for 4 months. 38.0

37.0

36.0

0

5 10 Weeks in isolation underground

15

1. Study the three charts on the previous page and determine when each of the following are at their peak for women:

(a) White blood cell count

(b) Body temperature

Daily: Daily:

Monthly: Monthly:

Annually: Annually:

2. Study the graphs for ‘daily rhythms of birth and death’ and ‘body temperature’. Is there any correlation (mutual relationship) between the time of day when most deaths occur and body temperature? Explain your answer:

3. Imagine you are about to sit a theory exam.

(a) At what time of the day should you sit the exam to provide your best performance?

(b) Explain your reasoning:

4. (a) When does insulin peak in the daily cycle?

(b) Explain why the production of insulin peaks at this time of day:

5. When, in the daily cycle, is the liver least able to metabolise alcohol?

No Cla t fo ssr r o Us om e

6. Describe how beard growth is correlated with the seasons of the year:

7. Different cycles for the same biological variable can occur simultaneously in an organism. The graph at the top of this page shows the body temperature of a woman who stayed underground for four months.

(a) What is represented by the rapid swings in body temperature?

(b) The same graph also displays a longer undulating rhythm with a period of several weeks. Draw a line of ‘best fit’ through the middle of the ‘rapid swings’ to show this longer rhythm.

(c) Describe the likely cause of this rhythm:

(d) Explain why this experiment was carried out in a cave environment:

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41

31 Interpreting Actograms of activity can be seen. By keeping the environmental cues constant (e.g. constant dark) it is possible to see the length of time of the organism's biological clock runs for in the absence of environmental cues. This length of time is called the free-running period. A phase shift occurs when an organism is entrained to a new regime of environmental cues.

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Key Idea: Actograms are graphical records of an organism's activity and can be used to determine its activity patterns. In a laboratory, the activity of an organism can be recorded continuously. The activity is often recorded as a bar on a line representing 24 hours. By placing the successive blocks of 24 hours under each other, a clearer picture of the pattern

Making an actogram Tape

Imagine ticker tape rolling out of a machine. Every time an organism is active, a mark or bar is made on the tape. The tape is then cut up into lengths representing 24 hours.

Raster

The lengths are then laid out one under the other in order, forming a stack called a raster.

Actogram of human activity

24:00 0

For the first 10 days the individual was exposed to conditions of 12 hours dark and 12 hours light with no other environmental cues.

12:00

24:00

The bars labelled A are the same piece of activity.

A

A

B

B

The lines labelled B are the same piece of activity. The free-running period in humans is about is about 25 hours. When the free running period is longer than 24 hours the timing of the activity moves to the right on an actogram. When it is less than 24 hours the timing of the activity moves to the left.

20

30

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After another 10 days environmental cues were restored but following a new regime. The individual's activity followed the new regime. A shift in the start point of the activity like this is called a phase shift.

Time 24:00

12:00

To maintain continuity between cuts, the raster is copied and pasted to the left but shifted down one line. This is called double plotting and is how most actograms are laid out.

10

Days

After 10 days, no environmental cues were given to the individual. The light level was set to low but constant.

Double plotted raster

Bar showing length of activity

1. Why are actograms produced by double plotting the original raster?

2. (a) What is a free-running period?

(b) How would you tell if the free-running period was shorter or longer than 24 hours?

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42

32 Activity Patterns in Animals variable to which it is usually entrained. The activity patterns of two species were recorded in the absence of environmental cues to determine the free running period of the rhythm. The results are displayed below as actograms. On each actogram the first day of recording is only shown on the left (day two is outlined and shaded in blue).

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Key Idea: A free-running endogenous rhythm usually has a slightly different period from the cyclic environmental variable that entrains it. The rhythm can be recorded as an actogram. In the absence of an external zietgeber (such as light) an endogenous rhythm will adopt a free-running period, which is usually slightly different from the cyclic environmental

24:00

12:00

Mouse A 24:00

24:00

12:00

24:00

2

3

3

4

7

24:00

12:00

24:00

1

Day number

24:00

5

6

12:00

12:00

4

5

2

Day number

Day number

2

24:00

24:00

1

1

Mouse B

12:00

6 7 8 9

10

3

11

4

12

5

13

6

14

7

Data: Dr. Bob Lewis, Department of Zoology, University of Auckland.

Toebiter Cirolana sp.

House mouse Mus musculus

The house mouse is a nocturnal animal. The charts above record the activity patterns of two different mice. Their activity was recorded for 7 days, using a running wheel with sensors connected to a computer. During the course of the experiment, the mice were kept in dim light (0.1 lux).

Toebiters are small marine isopod crustaceans that scavenge for food in the surf region of sandy beaches in New Zealand. The chart above records the activity pattern over 14 days. During the experiment, the freshly collected toebiter was kept in total darkness at a constant temperature of 20°C.

1. Determine the periods for each mouse's activity over the 7 days:

(a) Mouse A:

(b) Mouse B:

2. What type of rhythm is shown?

3. Briefly describe two differences in the activity patterns of these two mice: (a)

(b)

No Cla t fo ssr r o Us om e

4. (a) Determine the period for the toebiter's activity over the 14 days of the trial:

(b) What type of rhythm is shown?

(c) Why was the temperature kept at 20°C?

(e) What cue on the shore would the animal use to synchronise its rhythm?

(d) Describe a biological advantage to the animal of this rhythm:

5. What evidence do you have that the rhythms shown above are endogenous?

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43 Cockroach activity

No Cla t fo ssr r o Us om e

Cockroaches are nocturnal insects. The experiments below investigated the periodicity of their behaviour under controlled conditions. The first experiment determined the free-running period. The results of the second experiment show the entrainment of the rhythm. Note the actograms below are not double plotted.

Free-running period

Days

1 2 3 4 5 6 7 8 9 10

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The charts on the right record the activity rhythm of a cockroach kept for 20 days in a running wheel actogram. There are activity records shown for each of the 20 days, with each day's record presented in succession down the page. The periods of activity are shown as grey rectangular blocks and periods of inactivity shown as no rectangle. The onset of constant darkness on day 11 exposed the free-running period and produced a phase shift.

0

24

24 hours

Light regime

Darkness

Light

Light

Light regime

This is the term used to describe the cycles of light and darkness. It is indicated by bars of 'light' and 'darkness' at the bottom of each table:

Days

Days 1-10:

The cockroach was in a 12 hour light / 12 hour dark cycle (LD 12:12) Days 11-20: The cockroach was in constant darkness for these 10 days (DD)

11 12 13 14 15 16 17 18 19 20

0

Entrainment

Days

Recall that the process by which the endogenous rhythm is synchronised to an environmental cue (or zeitgeber), such as a 12 hour light /12 hour dark cycle, is termed entrainment. The chart on the right shows the activity record of a cockroach. It is being entrained to a new light cycle, which occurs nine hours earlier than the one it had been experiencing previously. Entrainment usually has the following features: • A phase shift for the start of the activity is gradual, without jumps. • As the activity gets nearer the new lights-out signal, the daily phase shift is reduced.

24

24 hours

Light regime

Darkness

1 2 3 4 5 6 7 8 9 10 11 12

0

1

2

3

4

5

6

7

8

9

10

Hours

Light regime Original New

No Cla t fo ssr r o Us om e

6. What type of rhythm is displayed in the first 10 days?

7. In what part of the light/darkness cycle was the cockroach most active? 8. Describe the activity pattern displayed by the cockroach:

9. Determine the free-running period (in hours) displayed between days 11-20:

10. Describe the effect of entrainment on the free-running period, and explain its adaptive value in a natural environment:

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44

33 Plant Rhythms and respond to seasonal changes. Plant hormones are chemicals that act as signal molecules to regulate plant growth and responses. Alone or together, plant hormones target specific parts of a plant and produce a specific effect. Many have roles in coordinating timing responses in plants including promoting and breaking bud dormancy, seed germination, and fruit ripening. In addition these rhythms are linked to temperature.

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No Cla t fo ssr r o Us om e

Key Idea: Plant hormones play crucial roles in the timing of activities including fruit ripening and breaking dormancy. Many of the responses of plants to cues in the environment, such as low temperatures and daylength are mediated by hormones. Low temperature stimulation of flowering (vernalisation) and seed germination (stratification) are common in many species. They are examples of responses mediated by plant hormones, and enable the plant to track

Hormones, plant growth, and fruiting

flo we rd

December

November

January

October

February

September

March

od

August

April

July

Dorm an c y pe ri

Dormancy is a condition of arrested growth. The plant, or its seeds or buds, do not resume growth until increasing daylength and temperatures provide favourable growing conditions in spring. Abscisic acid (ABA) promotes dormancy, preventing development of the leaf and flower bud under unfavourable conditions

Seed germination and hormones

The seeds of many cold-climate plants will not germinate until they have been exposed to a period of wet, cold (5°C) conditions. This is called cold stratification. LINK

KNOW

15

Ethylene is a gaseous plant hormone with an important role in the ripening process of many fruits. Auxin and ethylene are believed to work together to promote fruit fall.

May

June

Deciduous plants shed their leaves every autumn in a process called abscission. A decline in auxin (IAA) and an increase in ethylene work together to bring about leaf drop. Losing leaves conserves resources at a time when there is not enough light for photosynthesis and the cold weather may damage the delicate leaf structures.

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nd

nt

elopment it dev

Leaf a

ev

me op l e

Fru

Bud burst and flowering follow exposure to a cold period in many plants, including bulbs and many perennials. This process is called vernalisation and it ensures that reproduction occurs in spring and summer, not autumn. Gibberellins are important in breaking bud dormancy.

Auxins and gibberellins are important in promoting the growth and development of shoots.

ABA accumulates in seeds during fruit production and is important in seed dormancy. A high level of ABA in the seed embryo promotes dormancy.

Gibberellins are required for seed germination. They stimulate cell division and cell elongation, allowing the root to penetrate the seed coat. Š 1988-2016 BIOZONE International ISBN: 978-1-927309-56-8 Photocopying Prohibited


45

Daily rhythm in tulips

7.00 am

9.30 am

5.00 pm

11.00 am

7.00 pm

1. (a) Describe the adaptive value of dormancy in plants:

(b) What cues are likely to be involved in breaking dormancy?

2. How does vernalisation ensure a plant will not flower in autumn?

3. Describe the adaptive value of leaf abscission:

5. Describe is the advantage of cold stratification in plant seeds:

No Cla t fo ssr r o Us om e

4. Why is it likely that the same hormones are responsible for both leaf fall (abscission) and fruit fall in plants?

6. (a) Describe the sleep movements of tulips in response to temperature:

(b) How might these movements be adaptive?

(c) What is the name of this type of response? Š 1988-2016 BIOZONE International ISBN: 978-1-927309-56-8 Photocopying Prohibited

All photos: RA

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No Cla t fo ssr r o Us om e

Many flowers, including tulips, show sleep movements. In most species, these are triggered by daylength, but in tulips the environmental cue is temperature. This series of photographs shows the sleep movements of a single tulip flower over one 12 hour period during spring. Sleep movements may prevent flower damage, stop the entry of non-pollinating insects, or stop the pollen becoming wet with dew.


46

34 Photoperiodism in Plants of a pigment called phytochrome. Phytochrome acts as a signal for some biological clocks in plants and exists in two forms, Pr and Pfr. It is important in initiating flowering in longday and short-day plants, but is also involved in other light initiated responses, such as germination and shoot growth.

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No Cla t fo ssr r o Us om e

Key Idea: Photoperiodism is the response of a plant to the relative lengths of light and dark. It is controlled by the pigment phytochrome, which occurs in two forms Pr and Pfr. Flowering is a photoperiodic activity that is dependent on the species' response to light. It is controlled through the action

Phytochrome

In daylight or red light (660 nm), Pr converts rapidly, but reversibly, to Pfr.

Phytochrome is a blue-green pigment that acts as a photoreceptor for detection of night and day in plants and is universal in vascular plants. It has two forms: Pr (inactive) and Pfr (active). Pr is readily converted to Pfr under natural light. Pfr converts back to Pr in the dark but more slowly. Pfr predominates in daylight. The plant measures daylength (or rather night length) by the amount of phytochrome in each form.

Sunlight

Slo w ly in

rsion nve co

Pr

da

rk

In the dark or in far red light (730 nm) Pfr reverts slowly, but spontaneously, back to the inactive form of phytochrome Pr.

Rap id

ne

ss

Pfr

Pfr is the physiologically active form of phytochrome. It promotes flowering in long-day plants and inhibits flowering in short-day plants.

Phytochrome interacts with genes collectively called "clock genes" that maintain the plant's biological clock.

Physiologically active “Clock genes”

There is still uncertainty over what the flowering hormone (commonly called florigen) is. Recent studies suggested it may be the protein product of the gene FLOWERING LOCUS T (FT) (in long day plants at least) which appears to influence gene expression that includes the gene LEAFY (LFY) in the apical meristem and causes flowering.

Flowering hormone

The hormone is transported to the apical meristem where it causes a change in gene expression that leads to flowering.

1. (a) Identify the two forms of phytochrome and the wavelengths of light they absorb:

(b) Identify the biologically active form of phytochrome and how it behaves in long day plants and short day plants with respect to flowering:

No Cla t fo ssr r o Us om e

2. (a) Discuss the role of phytochrome in a plant's ability to measure daylength:

(b) Explain how this helps to coordinate flower production in a plant species?

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47 Manipulating flowering in plants

1. Long-day plants (LDP) flower when the photoperiod is greater than a critical day length. Short-day plants (SDP) flower when the photoperiod is less than a critical day length.

Controlling the light-dark rĂŠgime has allowed flower growers and horticulturists to produce flowers out of season or to coincide flowering with specific dates.

No Cla t fo ssr r o Us om e

Long day vs short day plants

Plants kept in greenhouses can be subjected to artificial lighting or covered to control the amount of light they receive. To be totally effective at controlling flowering, temperature must also be controlled, as this is also an important flowering cue.

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2. Interruption of the long dark period inhibits flowering in SDP but promotes flowering in LDP.

3. Dark must be continuous in SDP but not in LDP.

For the example of the Chrysanthemum, a shortday plant, flowering is can be controlled under the following conditions. The temperature is kept between 16 - 25 oC. The light-dark regime is controlled at 13 hours of light and 11 hours of dark for 4-5 weeks from planting to ensure vegetative growth. Then the regime changes to 10 hours light and 14 hours darkness to induce flowering.

4. Interruption of the light period inhibits flowering in LDP but not in SDP. 5. Alternating cycles of short light and short dark inhibit flowering in SDP. 6. Plants that do not use daylength to initiate flowering are called dayneutral (e.g. cucumber, tomato).

Chrysanthemums

Long-day plants

Photoperiodism in plants

When subjected to the light regimes on the right, the 'long-day' plants below flowered as indicated:

An experiment was carried out to determine the environmental cue that triggers flowering in 'longday' and 'short-day' plants. The diagram below shows 3 different light regimes to which a variety of long-day and short-day plants were exposed. 0

Flowering

hours

Long-d Long-day ay

No flowering

Shor Short-da t-day y

Flowering

Short-da Shor t-day y

Examples: lettuce, clover, delphinium, gladiolus, beets, corn, coreopsis

24

Short night

No flowering

Flowering

Long night

Long

Short-day plants When subjected to the light regimes on the left, the 'short-day' plants below flowered as indicated:

night

Long night interrupted by a short period exposed to light

No flowering

Examples: potatoes, asters, dahlias, cosmos, chrysanthemums, pointsettias

3. (a) What is the environmental cue that synchronises flowering in plants?

(b) What is a biological advantage of this synchronisation to the plants?

(a) Short-day plants:

No Cla t fo ssr r o Us om e

4. Study the three light regimes above and the responses of short-day and long-day flowering plants to that light. From this observation, describe the most important factor controlling the onset of flowering in:

(b) Long-day plants: 5. What evidence is there for the idea that short-day plants are best described as "long-night plants":

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48

35 What You Know So Far: Orientation in Time Investigating circadian rhythms

HINT: Explain how activity patterns are recorded and include reference to freerunning period and entrainment.

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you: Biological rhythms in animals

HINT: Include definitions that clarify the length and type of rhythm involved.

Biological rhythms in plants

HINT: Include definitions and reference to the role of phytochrome.

HINT: Include reference to phytohormones and the timing of key events in plant life cycles.

No Cla t fo ssr r o Us om e

Photoperiodism in plants

REVISE

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36 NCEA Style Question: Biological Clocks in Animals

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Fiddler crabs live on tidal mudflats. They feed on detritus in the mud at low tide, and return to their burrow at high tide to rest. The diagram below shows the actogram for a fiddler crab's activity in a laboratory. The crab was kept in constant light. Simplified actogram for fiddler crab

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Days 1 2 3 4 5 6 7 8 9 10 11 12

0

6

12 Time of day (hours)

18

24

High tide at beach of collection Times crab was active

1. (a) Identify the two biological rhythms shown by the crab:

(b) Identify the origin of the biological rhythms:

2. Explain the pattern seen in the actogram. Predict the continued activity of the crab in the lab in relation to the high tide at the beach of collection:

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3. Discuss the role of biological rhythms in animals, using the fiddler crab as an example. Include the origins of biological rhythms, the importance of zeitgebers, and the importance of accurate timing. You may use extra paper if required:

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TEST

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50

37 NCEA Style Question: Biological Clocks in Plants

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1. Carnations require at least two or three weeks with days longer than 14 hours to initiate flowering. Flowering is controlled by the pigment phytochrome in response to the photoperiod. (a) Describe this pattern of flowering:

(b) Explain how phytochrome controls flowering in carnations:

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2. Tulips have large flowers with petals that open during the day and close at night. Discuss how this regular movement of the petals enhances the plant’s reproductive success. You may use more paper if required.

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3. Some plants respond to seasonal changes by alternating periods of growth and dormancy. Describe the environmental cues that are important in these life cycle responses and discuss their adaptive value:

TEST

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51

38 KEY TERMS AND IDEAS: Orientation in Time 1. Match the following words with their definitions: A

biological rhythm

B

A plant that flowers when daylength is less than a critical value (~12 hours).

C

The physiological reaction of plants and animals to the presence and absence of light.

D

A pigment in plants responsible for the photoperiodism effect. Regulates the timing of flowering with different effects in long day and short day plants.

E

A plant that flowers when daylength is more than a critical value (~12 hours).

F

An environmental stimulus that is external to the organism (e.g. day length) is referred to as this.

G

The period of an endogenous rhythm when given no external environmental cue by which to synchronise the rhythm.

H

An exogenous cue that synchronises an organism's endogenous rhythms to the rhythms of the environment, e.g. the Sun or the light-dark cycle.

I

An endogenous timing system an organism uses to synchronise its activities with the environment.

J

An endogenous rhythm of rest and activity that approximates 24 hours and is entrained by the light-dark cycle.

K

Physiological changes or changes in activity in living organisms occurring in a cyclic manner. Most often associated with predictable daily, monthly, or annual environmental changes.

L

A stimulus originating within the organism itself, e.g. hormonal changes, is this.

The synchronisation of an endogenous rhythm with an external cycle such as light and dark.

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No Cla t fo ssr r o Us om e

biological clock

circadian rhythm endogenous entrainment exogenous

free running period long-day plant

photoperiodism phytochrome

short-day plant zeitgeber

2. Name the type of rhythm in the following examples:

(a) A whelk kept in the laboratory becomes active every 13 hours:

(b) The body temperature of a human in an isolated room rises and falls over 24 hours:

(c) A mouse kept in constant light is active for 12 hours and sleeps for 12 hours:

3. Identify the plants A, B, and C as short day, long day, or day neutral plants based on their flowering under the light schemes shown below (flowering F, no flowering NF): A B C DAY

F NF F

Night

NF F F

(a) Plant A:

(b) Plant B:

(c) Plant C:

No Cla t fo ssr r o Us om e

NF F F

4. The activity of a species of fly was recorded under constant conditions in a lab and an actogram made: Time (hrs)

24

12

24

12

24

Active

(a) Was the free-running period of the fly longer or shorter than 24 hours?

(b) How can you tell? Š 1988-2016 BIOZONE International ISBN: 978-1-927309-56-8 Photocopying Prohibited

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39 Species Interactions relationship is an exploitation. If one species benefits and one is unaffected, the relationship is said to be commensal. Some species interactions involve a close association or symbiosis (living together) between the parties involved. Symbioses include parasitism and mutualism. Many species interactions involve coevolution, in which there is a reciprocal evolution of adaptations in both parties.

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Key Idea: All species interact with their own and other species. These interactions carry costs and/or benefits to the parties involved. No organism exists in isolation. Each interacts with other organisms of its own and other species. Species interactions (those between different species) involve benefit to at least one party. If one party benefits at the expense of another, the

Mutualism

A

Exploitation

Predation

B

Benefits

Type of interaction between species

Benefits

Competition

Parasitism

A

B

A

B

A

B

A

B

Benefits

Harmed

Benefits

Harmed

Benefits

Harmed

Harmed

Harmed

Both species benefit from the association.

Predator kills the prey outright and eats it.

Examples: Tick bird on zebra removes parasites and alerts zebra to danger, while tick bird gains access to food.

Examples: Lion preying on wildebeest or praying mantis (below) consuming insect prey.

The adaptations of predators and prey are the result of coevolution: predators have adaptations to capture prey and prey have adaptations to avoid capture.

Flowering plants and their insect pollinators have a mututalistic relationship. Flowers are pollinated and the insect gains food (below).

Herbivory

Herbivore eats parts of a plant and usually does not kill it. Plants often have defences to limit the impact of herbivory. Example: Giraffes browsing acacia trees. Browsing stimulates the acacia to produce toxic alkaloids, which cause the giraffe to move on to another plant. Acacia thorns also deter many browsers.

The parasite lives in or on the host, taking (usually all) its nutrition from it. The host is harmed but usually not killed. Examples: Pork tapeworm (below) in a pig's gut. Some plants (e.g. mistletoes) are semi-parasitic (hemi-parasites). They photosynthesise but rob the host plant of nutrients and water.

Individuals of the same or different species compete for the same resources, with both parties suffering, especially when resources are limited. Examples: Monarch caterpillars compete for access to milkweed. Those hatched later in the season may starve. Plants growing close to each other compete for light and soil nutrients.

Steve Garvie cc 2.0

Luc Viatour www.Lucnix.be

(a) Mutualism:

(b) Exploitation:

(c) Competition:

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1. For the purposes of this exercise, assume that species A in the diagram represents humans. Briefly describe an example of our interaction with another species (B in the diagram above) that matches each of the following interaction types:

2. Plants are not defenceless against herbivores. They have evolved physical and chemical defences to deter herbivores. In some cases (as in grasses) grazing stimulates growth in the plant.

(a) What is the acacia's response to giraffe browsing?

(b) How might this response prevent over-browsing?

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3. Clownfish spend much of the time taking refuge among the tentacles of this large sea anemone. They help protect the anemone from predators and gain significant protection from predators.

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Examples of interactions between different species are illustrated below. For each example, identify the type of interaction, and explain how each species in the relationship is affected.

(a) Identify this type of interaction:

(b) Describe how each species is affected (benefits/harmed/no effect):

4. Oxpecker or tick birds feed on the skin parasites of large herbivores, such as Cape buffalo, zebra and rhinoceros. These birds will act as an early warning system by calling when predators approach.

(a) Identify this type of interaction:

(b) Describe how each species is affected (benefits/harmed/no effect):

(a) Identify this type of interaction:

(b) Describe how each species is affected (benefits/harmed/no effect):

Dactylanthus taylorii (wood rose)

C.R. Veitch, Dept of Conservation

Short-tailed bat

Peter Bray, Airborne Honey Ltd

(c) Dactylanthus taylorii is pollinated by the short-tailed bat, which feeds on the musky smelling nectar produced by the flowers during summer. Identify this type of interaction:

(d) Describe how each species is affected (benefits/harmed/no effect):

6. In many New Zealand beech forests, kaka feed on honeydew, a liquid excreted by a scale insect feeding on the beech tree (left). These scale infestations are common although there is no evidence that they harm the tree. Introduced wasps also feed on the honeydew and often attack kaka trying to do the same.

Anal tubules of beech scale insects with honeydew droplets

(a) Identify the interaction between the scale insect and the beech tree. Describe how each species is affected (benefits/harmed/no effect):

(b) Identify the interaction between the wasp and the kaka. Describe how each species is affected (benefits/harmed/no effect):

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J. Barkle, Dept of Conservation

5. Dactylanthus taylorii is an endangered endemic New Zealand plant. It does not photosynthesise, but grows attached to the root of host tree species (e.g. seven finger or patē) from which it derives all its nutrients.


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40 Mutualism Involving Animals not. Some mutualistic relationships are obligate, meaning that one (or both) species can not survive without its mutualistic partner. Other mutualistic relationships may not have the same level of dependency, and the relationship is not necessary for the survival of either species. These associations are termed facultative mutualism.

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Key Idea: Mutualistic relationships benefit both species involved. Often the benefit (to at least one party) is food. Mutualism is a symbiotic relationship between two different species in which both interacting species benefit from the association. It can be contrasted with exploitation or parasitism in which one animal benefits while the other does

Types of mutualistic relationships

Resource-resource relationships: One resource is traded for another (usually food or a nutrient).

Many reef building corals rely on a mutualism with algae in their tissues. The corals obtain some of their energy from the algae. The algae obtain a habitat and utilise the coral's nitrogenous waste and carbon dioxide.

Termites, which feed on wood, rely on a community of microbes in their gut to break down the cellulose in wood and produce the fatty acids the termites use for energy. The obligatory relationship (opposite) provides food for both microbes and termites.

Service-resource relationships: A service is performed in exchange for a resource, e.g. food for protection.

Some species of ants "farm" aphids by protecting the aphids from predation by ladybirds. In return the ants harvest the honeydew produced by the aphids.

Many large grazing mammals rely on oxpeckers to remove parasite infestations. The grazers provide food to the birds and the birds provide an anti-parasite service.

Service-service relationships: Both organisms provide a service to each other.

Clownfish protect their home sea anemone by chasing away predators, e.g. butterfly fish. In return, the anemone protects the clownfish from its predators. However, the anemone's symbiotic algae also benefit from the nitrogen excreted by the clownfish. WEB

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True service-service mutualisms are very rare and there is usually some sort of resource component present.

Acacia ants nest within the thorns of the bullhorn acacia. In exchange for shelter, the ants protect acacias from attack by herbivores. There is a resource component though because the ants feed on the lipid rich bodies at the tips of the acacia leaflets. Š 1988-2016 BIOZONE International ISBN: 978-1-927309-56-8 Photocopying Prohibited


55 Mutualistic relationships can be obligatory or facultative

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Coolstock cc 2.0

Pollen grains

White-tailed deer

In an obligatory mutualism, neither species can survive without the other. There is a mutualistic relationship between many herbivores and the microbes in their gut, which enables cellulose to be digested. In ruminants, the rumen microflora break down the cellulose in forage and the ruminant obtains energy from the volatile fatty acids released by the microbial activity. The microbes benefit by having a stable growth environment and a food supply.

Honeybee pollinating a purple crocus

In a facultative mutualism, both species benefit from interacting with each other but can survive without the interaction. In many cases, a species may interact mutualistically with many similar species. For example, bees pollinate many different types of flower. The flower can use any type of bee as a pollinator and the bee can visit any type of flower to gather nectar.

1. (a) Define the term mutualism:

(b) Distinguish between facultative and obligatory mutualism:

2. The image shown right shows the Riftia tube worm that lives near hydrothermal vents deep in the ocean. The worms have no digestive tract and rely on symbiotic bacteria for nutrition. In return, the bacteria are provided with the safe stable internal environment of the worm to live. (a) Is the relationship between the worm and the bacteria an obligate or facultative relationship?

(b) Explain your answer:

3. Describe three broad classes of benefits that seem to be most common in mutualism:

(b) (c)

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(a)

4. Service-service mutualisms, such as the clownfish-anemone relationship, appear to be very rare. What might suggest that there is a resource component to these relationships?

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NOAA


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41 Mutualism Involving Plants

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Key Idea: Plants form mutualistic relationships with animals, fungi, bacteria, and other plants. Because plants are unable to move they must have effective strategies for reproduction and acquiring nutrients. Most

plants form mutualistic relationships with fungi that help to provide nutrients to the roots in exchange for carbohydrate from the plant. Plants use many different types of animals to facilitate pollination.

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Nitrogen fixation in root nodules

Nitrogen fixation is a crucial part of the nitrogen cycle. Nitrogen is an abundant element, but biologically available nitrogen compounds are relatively scarce, so plants that are able to form a mutualistic relationship with bacteria to fix nitrogen have a nutritional advantage. Plants in the legume family (e.g. peas, beans, and clover) and nitrogen fixing bacteria (e.g. Rhizobium) form a mutualistic relationship with considerable nutritional benefits to both parties.

WBS

Nitrogen fixing bacteria reduce nitrogen from the atmosphere to ammonium ions, combining them with organic acids to produce amino acids. The amino acids provide a nitrogen supply to the plant and the bacteria gain a supply of carbohydrate and a suitable environment in which to grow.

Jeremy Kemp cc 3.0

Root nodule

Nitrogen fixation in legumes occurs within root nodules, which are extensions of the root tissue formed in response to bacterial entry. The nodules provide the low oxygen environment necessary for nitrogen fixation. The presence of nodules allows plants to grow successfully even when soil nitrate is low.

Mycorrhizal associations

Mycorrhizae are formed by the mutualistic association between a fungus and the roots of a vascular plant. The fungus colonises the plant roots, either intracellularly or extracellularly, forming the mutually beneficial mycorrhizal association.

B

Both photos: Thergothon cc 3.0

A

Around 85% of vascular plant species have mycorrhizal associations and they are vitally important to plant health and forest ecology. The fungal mycelium provides a vast surface area, improving the plant's capacity to absorb minerals and water. In addition, the fungus can access phosphate ions, which are largely unavailable to the plant roots, and transfers them to the plant. In return, the plant provides the fungus with a supply of carbohydrate (produced by photosynthesis). Many conspicuous fungi in the forest, e.g. fly agaric (A), are ecotomycorrhizal. The mycorrhizal roots (B) are short and stubby with a film of fungal threads enveloping them.

(a) The plant:

(b) The bacterium:

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1. Root nodules are a mutualistic relationship between a bacterium and a plant. Describe the benefits of the relationship to:

2. When might legumes have a clear competitive advantage over plants that cannot fix nitrogen? Explain your answer:

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57 Mistletoe pollination ffMistletoes are hemiparasitic (partly parasitic) flowering plants. They are photosynthetic but use specialised roots to gain water and nutrients from their host plant. There are eight species of mistletoe native to New Zealand. Unlike mistletoes in other countries, New Zealand mistletoes do not harm their hosts.

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ffThe two species of New Zealand beech mistletoes (Peraxilla) are pollinated by tui and bellbirds, which are nectar feeders and

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have adaptations to penetrate the mistletoe flower and access the nectar. Even when the flower is ready for pollination (ripe), the petals are closed. When tui and bellbirds give the ripe flower a squeeze with their beak, the petals spring open to reveal the inside of the flower. The birds can then feed, collecting pollen on their heads, which they transfer to different plants as they move between flowers. Native solitary bees are also known to open the flowers by chewing the tips until they spring open.

ffTui and bellbirds feed on a variety of plant species but are primarily responsible for beech mistletoe pollination and are also the

Bellbird on beech mistletoe

Tui on beech mistletoe

3. Describe the mutualism between vascular plants and mycorrhizal fungi, including benefits to plant and fungus:

4. (a) Horticulturists frequently add a mycorrhizal inoculum when transplanting plants. Suggest why they would do this:

(b) Why would they not add phosphorus fertiliser when attempting to establish the mycorrhizae?

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5. (a) Explain how the mutualism between NZ beech mistletoes and its bird pollinators benefits both parties:

(b) How is the dependency of the relationship different for the mistletoe and the bird pollinator?

(c) Describe possible benefits and risks to the mistletoes of such a specialised pollination system:

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PHOTOS: Jenny Ladley, University of Canterbury

main dispersers of the pea-sized fruits. Seed dispersal is critical to mistletoes because the seed must land on a suitable host tree.


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42 Interpreting Predator-Prey Relationships not usually the case. Prey species are more likely to be regulated by other factors such as the availability of food. However, predator population cycles are often regulated by the availability of prey, especially when there is little opportunity for switching to alternative prey species.

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Key Idea: Predator and prey populations frequently show regular population cycles. The predator cycle is usually based on the intrinsic population cycle of the prey species. It was once thought that predators regulated the population numbers of their prey. However, we now know that this is

A case study in predator-prey numbers

In some areas of Northeast India, a number of woolly aphid species colonise and feed off bamboo plants. The aphids can damage the bamboo so much that it is no longer able to be used by the local people for construction and the production of textiles.

Bamboo plants are home to many insect species, including ladybirds and aphids.

Aphids feed off the bamboo sap, and the ladybirds are predators of the aphids (below).

Giant ladybird beetles (Anisolemnia dilatata) feed exclusively on the woolly aphids of bamboo plants. There is some interest in using them as biological control agents to reduce woolly aphid numbers, and limit the damage woolly aphids do to bamboo plants. The graph below shows the relationship between the giant lady bird beetle and the woolly aphid when grown in controlled laboratory conditions.

12

Aphid population

70

Ladybird population

10 8

50

6

40

4

30

20

Number of giant ladybirds

80

60

Number of aphids

Source: Majumder & Agarwala (2013) World Journal of Zoology 8 (1): 55-61

90

2

10

0

0

Sampling week

(b) Do the peak numbers for both species occur at the same time?

(c) Why do you think this is?

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1. (a) On the graph above, mark (using different coloured pens) where the peak numbers of woolly aphids and giant ladybirds occurs:

2. (a) Is the trend between the giant ladybirds woolly aphids positive or negative (circle one).

(b) Explain your answer:

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43 The Effects of Interspecific Competition different species) is commonly less intense because species with similar ecological requirements have evolved slight differences in the resources they exploit or in the way they exploit them. The evolution of these differences is called niche differentiation.

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Key Idea: Interspecific competition is often reduced by different species exploiting slightly different resources. Competition is most intense between members of the same species because their habitat and resource requirements are identical. Interspecific competition (competition between

Flying insects

T

Hawking, flushing, feeding associations

Hawking and gleaning

(Not drawn to scale)

F

Piwakawaka (fantail)

W

Riroriro (grey warbler)

T

Miromiro or ngiru-ngiru (tomtit)

Rf

Tititi pounamu (rifleman)

K

Brown kiwi

Ro Toutouwai

F

W

Foliage and bark gleaning

Flying insects

Bark gleaning

K

Rf

Ground feeding

Ro

South Island beech forests are home to a number of insectivorous birds. The six species above inhabit the same region of bush and all are partially or completely insectivorous. This appears to be a contradiction of Gause’s competitive exclusion principle, which states: “When different species compete for the same resources in the habitat, one eventually prevails and displaces the other”. Niche differentiation enables the species to avoid direct competition by exploiting slightly different food resources or the same foods in a different way or at different times. All six species have slightly different hunting strategies. The robin is a ground feeder, searching through the leaf litter for adult insects and larvae. The grey warbler picks insects from the tree bark

(robin)

(gleaning). Fantails use several strategies to capture insects on the wing. In open vegetation, they use hawking, perching in open vegetation to spot insect swarms and flying out to capture them. In denser bush, they fly around to flush insects out for easy capture. They also use feeding associations, following other birds and even humans to capture insects disturbed by another's activities. The tomtit exploits upper and lower forest strata both gleaning and hawking; whichever is the most rewarding at the time of day. The rifleman feeds methodically, spiralling up a tree trunk from the base and picking insects from the surface or from cracks in the bark. The brown kiwi probes beneath the litter with its long beak and feeds at night.

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Underground probing

1. Why is interspecific competition usually less intense than intraspecific competition?

2. Describe the feeding niche for each of the birds listed above (i.e. where, when, and how do they feed):

(a) Fantail:

(b) Warbler:

(c) Robin:

(d) Tom tit:

(e) Rifleman:

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Studies on bumblebee foraging have shown that when bumblebees forage in the presence of other bumblebee species they tend to spend the majority of their time on particular flower types. In many cases, the length of the corolla (the length of the flower petals) of flowers visited correlates with the length of the bumblebee's proboscis (mouthparts).

Bombus appositus

Long proboscis

Bumblebee species

Number of visits per hour

0

4

8

12

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Adaptations reduce competition in foraging bumblebees

Bombus bifarius

Short proboscis

Bumblebee species in the mountains of Colorado (graph right) compete for nectar from flowers. Species with a long proboscis take nectar from flowers with long petals. Species with a short proboscis take nectar from flowers with short petals. This reduces competition for food between the bumblebee species.

Bombus kirbyellus

8

12

0

4

8

12

0 4 8 12 Flower corolla length (mm)

Heuchera

Visits to flower A

49

Experiment Control Bombus appositus

Proboscis

4

Bombus frigidus

167

Corolla

0

72

84

Experiment Control Bombus flavifrons

The bumblebees Bombus appositus and Bombus flavifrons normally show a preference for particular flower species (call these A and F respectively for reference). However, in the absence of competition, they will forage on either flower species. This was shown in an experiment in which visits of Bombus appositus to its usual forage flower A were restricted. Bombus flavifrons, which usually forages on flower F, responded by increasing its visits to flower A and decreasing its visits to flower F.

3. Describe two ways in which species can avoid directly competing for the same resources in their habitat: (a)

(b)

4. Explain why the coexistence of the six NZ bird species does not violate Gause’s competitive exclusion principle:

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5. (a) How do the Bombus species in Colorado reduce competition for flower resources?

(b) Are the differences between the Colorado species mainly structural, physiological, or behavioural? Explain:

6. What evidence is there that competition restricts bumblebee species to certain flower types?

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44 Identifying Species Interactions in Ecosystems Key Idea: Species interact in ways that are broadly similar regardless of the ecosystem in which they are found.

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1. Complete the tables of relationships below for the examples illustrated, filling in the type of relationship, the effect (+, –, 0) and the species involved. The first one has been done for you. In the beech example, use the same answer format:

Species interactions on the African savannah

Zebras compete with other grazing mammals, such as wildebeest, for grazing space, forage, and water. This may be critical when resources are scarce, e.g. during a drought.

Ectoparasites, such as ticks (left) mites, and fleas, live attached to the skin or hair of the host, where they suck body fluids, cause irritation, and may act as vectors for disease-causing microorganisms.

Interactions between zebras and other species Interaction

Zebra

Competition

Species B

Wildebeest

On the savannah, the zebra's main predators are lions (right) and hyaenas. Herbivory is a similar type of exploitation, except that the plant is usually not killed by the herbivore and may even benefit from regular cropping.

Species interactions in a Nothofagus (southern beech) forest

The southern beech (Nothofagus), pictured left, has a competitive advantage over other New Zealand tree species, such as tawa, in areas of suboptimal soil or harsh climatic conditions. Many Nothofagus species are able to tolerate the low light of the subcanopy, and can grow rapidly.

Interactions between Nothofagus and other species Interaction

Nothofagus

Species B

Red mistletoe (left) is a hemiparasite of beech. It can photosynthesise, but it takes water and nutrients from the beech root system. The mistletoe is an important food source for bellbirds and tui who compete for nectar but also pollinate the mistletoe flowers.

J. Ladley UoC

Brushtail possums (left) are a major pest species in New Zealand, causing significant damage to native trees by eating their leaves, flowers, and fruit. When Nothofagus fruits heavily, more than 40% of a possum's diet can come from its flowers, fruit, and seeds.

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Rudolph89 CC3.0

The association between the roots of Nothofagus and the fungus Amanita nothofagi (right) is a mutualism. These associations, or mycorrhizae, help the trees to absorb water and nutrients from the soil. In return, the fungi are provided with sugars from the tree.

Photo: Michael (inski) CC 3.0

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45 What You Know So Far: Interspecific Relationships Competition between species

HINT: How does competition affect the competing species?

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you: Mutualism

HINT: How do organisms benefit from mutualistic relationships?

Exploitation

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HINT: Predation, herbivory, and parasitism. How are the parties involved affected?

REVISE

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46 NCEA Style Question: Interspecific Relationships

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Research has found that on the North Island mainland, pollination of flowers (and hence seed production) has declined as bellbird and stitchbird populations have declined. On offshore island sanctuaries where bird pollinators are still present in large numbers, pollination of the flowers is still high.

Rhabdothamnus solandri

Discuss the relationship between R. solandri and its pollinators (bellbirds and stitchbirds) and why populations of R. solandri are in decline.

In your answer you should: • Describe the interspecific relationship between the pollinators and R. solandri and the advantage of this relationship to the species involved. • Explain why the decline in R. solandri populations is linked to declines in bird populations. • Justify why efforts to reestablish locally extinct bird populations in the North Island could have larger ecological effects than just the return of the birds to the environment.

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Rudolph89

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1. Rhabdothamnus solandri (taurepo) is the sole member of the plant family Gesneriaceae and is native to New Zealand. The shrub grows to about two metres tall and produces red and yellow trumpet shaped flowers. About 8% New Zealand's plants are bird pollinated. R. solandri's flowers are pollinated by tuis, bellbirds, and stitchbirds, with bellbirds and stitchbirds being the key pollinators.

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47 KEY TERMS AND IDEAS: Interspecific Relationships 1. Match the following words with their definitions: A A mutually beneficial interaction between individuals of different species.

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exploitation

B The relationship where an individual of one species kills and eats the individual of another species.

mutualism

C A type of symbiosis between organisms of different species where one organism benefits at the expense of the host.

parasitism

D Competition occurring between members of different species.

predation

E Any interaction between individuals (of different species) in which one individual benefits and the other is affected detrimentally, e.g. parasitism, predation, herbivory.

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2. Cleaner shrimps are various species of shrimp that have the habit of picking parasites from the mouth and gills of fish that attend "cleaning stations" on tropical reefs. (a) Name this type of species interaction:

(b) Explain how each species benefits or is disadvantaged in the interaction:

Brocken Inaglory CC 3.0

(a) Name this type of interaction:

(b) Explain how each species benefits or is disadvantaged in this interaction:

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3. When a large mammal dies on the African savanna, the carcass is quickly found by scavengers. Many different species may try to get a share of the meat and fighting often occurs:

(a) Describe the general pattern of the population numbers shown:

(b) Describe the likely causes of this pattern of population fluctuation:

0

1

2

Number of species B

Number of species A

4. The graph right shows the population of a predator species (A) and a prey species (B) in an area of forest over 3 years.

3

Years

TEST

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48 Intraspecific Communication behaviours, and attract mates. Messages can be passed between animals using a range of signals that may be visual, chemical, auditory, or tactile. The type of signal used depends on the activity pattern and habitat of the animal, e.g. sound carries well in dense forest.

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Key Idea: Communication is the transmission of (understood) information between individuals, usually of the same species. It is essential to species survival and reproductive success. Effective communication enables animals to avoid predators, coordinate foraging and hunting activity, maintain social

Channel The medium in which the signal is transmitted: visual, chemical/olfactory, tactile or auditory

Code

Sender The individual who transmits the signal

Signal The message conveyed from one individual to another: Aggression, submission, courting, social bonding

Code

Rules by which the sender must transmit the signal

Rules that enable the receiver to decipher the signal

Receiver The individual who detects the signal

Context The setting in which the communication occurs: dominance display, courtship, predator alert, food gathering

The two male baboons on the right are engaged in a dominance display. Both animals are acting as senders and receivers of a message.

Fixed action patterns and communication

The correct transmission of some messages is so critical that the method of transmission has become genetically fixed and the behaviour cannot be altered by learning or external stimuli. This kind of behaviour is called a fixed-action pattern (FAP). FAPs are spontaneous, stereotyped (always the same), and indivisible. Once begun, a FAP runs to completion and is independent of learning. Many FAPs have been identified in animals. The one illustrated below relates to feeding the southern black-backed gull (Larus dominicanus). Similar behaviour occurs in many other gull species.

Releaser or sign stimulus

Innate releasing mechanism

FAP

Brian Gratwicke

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The red dot on the bill of the adult gull acts as a releaser for a fixed action pattern in the chick (the chick pecks at the red dot). The pecking action acts as a releaser for a fixed action pattern in the adult, in which it regurgitates food (above). The behavioural response to the sign stimulus is mediated via a neural processing system called the innate releasing mechanism. The message "I'm hungry, feed me" is therefore communicated in a unchanging way, which is recognised by both parties.

1. Why do animals need effective communication over both long and short distances?

2. (a) Explain the role of releasers in behaviours involving fixed action patterns:

(b) Name a releaser for a fixed action pattern in gulls and describe the behaviour elicited:

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Olfactory messages

Tactile messages

Auditory messages

Some animals produce scents that are carried by the wind. Scents may advertise for a mate or warn neighbouring competitors to keep out of a territory. In some cases, mammals use their urine and faeces to mark territorial boundaries. Sniffing genitals is common among mammals.

Touch may be part of a cooperative or an aggressive interaction. Grooming behaviour between members of a primate group communicates social bonding. Vibrations sent along a web by a male spider signal to a potential mate not to eat him.

Sound may be used to communicate over great distances. Birds keep rivals away and advertise for mates with song. Fin whales send messages over thousands of kilometres of ocean. Calls by mammals may attract mates, keep in touch with group members or warn away competitors.

Visual messages

Many animals convey information to other members of the species through body coverings and adornment, as well as through gestures and body language. Visual displays can signal threat, show submission, attract a mate and even exert control over a social group.

artfarmer CC 2.0

Bioluminescence

Many animals are bioluminescent. The glow they produce can be used as a signal to others of their species, such as fireflies signalling to a mate. Some deep sea fish use bioluminescence to signal other fish in the school.

Attraction

Body position or facial expression

Social species with dominance hierarchies (e.g. wolves) use stereotyped expressions and body postures to avoid direct conflict with others in the group. The messages are well understood and rarely challenged.

Some animals produce a stunning visual display to attract a mate. The plumage of some birds can be extremely colourful and elaborate, such as the peacock (above), the birds of paradise, and the lyrebird.

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3. (a) Describe and explain the communication methods best suited to nocturnal animals in a forest habitat:

(b) Describe and explain the communication methods best suited to solitary animals with large home ranges:

4. Explain the role of dominant and submissive behaviours in animals with social hierarchies:

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49 Pukeko Communication pukeko has an unusual social organisation. Over 90% of the birds are communal, living and breeding together in groups of 3-12 individuals. Social behaviours are often graded from those involving overt aggression to those that are entirely submissive. Some birds almost always show submissive behaviour while others habitually show aggressive behaviour.

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Key Idea: Pukekos use a range of visual displays for communication between indiviudals. Postures provide a very important form of communication between animals. The ethogram (behavioural profile) below illustrates the various postures exhibited by the pukeko (Porphyrio porphyrio), a New Zealand wetland bird. The

Ethogram for pukeko behaviour

1B

1A

2A

Fighting. One bird jumping with feet ready for clawing and beak open for pecking.

5A

5B

9A

3

Fighting. One bird in aggressive upright posture with wings and tail raised and feet raised. The other bird is in the aggressive upright but not attacking.

6A

Facing away. Submissive display to an aggressive upright bird.

2B

4B

Fighting. Both birds in aggressive uprights and using feet to attack.

7

10

Crouch. Submissive display to an aggressive upright bird.

Full bow. Submissive wings and tail fully up.

6B

Fighting. Both birds jumping with feet ready for clawing and beak open for pecking.

9B

4A

Aggressive upright. Wings down. Tail horizontal.

11A

Horizontal forward. Aggressive display but not as aggressive as an upright.

8

11B

Head flagging. Submissive display. Head held low and moved from side to side.

Move away. Submissive display. Wings exaggerated. Tail fully up to uncover white feathers.

12

Head flick. Submissive display. Usually at end of encounter. Wings exaggerated, tail fully up. Beak held too high to peck at other bird.

+ + very aggressive

+ slightly aggressive

0 neutral

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Range of aggressive/submissive behaviours

– slightly submissive

– – very submissive

1. Pukekos have a graded range of display behaviours of increasing aggression or submission. In the spaces provided, use the symbols (+, –, 0) to indicate the degree of aggressiveness, submissiveness, or neutral body language for each of the behaviours shown.

2. Why is a lot of animal communication ritualised?

3. What might be the purpose of graded intensity in ritualised behaviour?

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50 Recording Animal Behaviour animal's behaviour is taken at regular time intervals (e.g. every minute, on the minute). Select a time interval that suits the nature of the behaviour and the time available to you for taking the sample. It is useful for a number of people to study a group at the same time, each observing a different animal, to allow comparisons and provide a total picture of group interactions. Use the codes listed to classify the types of behaviour shown by the animal. You may wish to present the results in table and/or graph format.

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Key Idea: Systematic recording of behaviour can help in understanding group dynamics and hierarchies. Bird species such as sparrows, ducks, hens, or seagulls are ideal subjects to observe and gather data on intraspecific social interactions, especially when resource competition is increased by feeding. Zoo animals, such as primates, also provide excellent subjects. As a means of gathering semiquantitative data about an animal's behaviour it is possible to use a record sheet. Using a watch, a 'sample' of a single

Species:

Age and sex:

Date:

Weather :

Time:

Season:

Behaviour chart

7. Dr (10 s)

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2

22

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3

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4

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5

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6

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7

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8

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Behaviour codes

DATA

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resting

F

feeding

Dr

drinking

Pr

preening/grooming

Fl

flying

Su

sunning

Wl

walking

Fo

floating

Sw

swimming

Dp

display (e.g. singing)

Ag

aggression (e.g. fighting)

Sb

submission

OS

other social interaction

Location codes

TASK: Use your record sheet(s) to produce a report, presenting your results in a table or graph. In your discussion, focus on how the behaviours you observed might relate to the survival of the individual.

WEB

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A

airborne

T

in a tree

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TT

on a tree trunk

TB

on a tree branch

TL

on leaves

G

on ground

GG

on ground - grass

GL

on ground - leaf litter

GS

on ground - soil

GM

on ground - marsh

W

in the water

Wu

under water

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51 Social Groupings

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Key Idea: Animals may be solitary, form loosely associated groups, or form complex groups with clear social structures. Each behaviour has its advantages and disadvantages. No animal lives completely alone. At some stage in their lives,

Unstructured social groups

Structured social groups

Solitary animals spend the majority of their lives alone, often in defended territories. They may only seek out others of their species for breeding. Offspring are often driven away shortly after they become independent.

Many animals form loose associations but do not interact socially. Each animal is acting for its own benefit with little or no direct cooperation between them. Schools of fish, flocks of birds, and some herding mammals exhibit this unstructured social grouping.

Some species form complex social structures, often based around a family group. Some involve dominance hierarchies in which individuals in the group are ranked socially.

Solitary life is often an advantage when resources are scarce or scattered over a large area. Solitary animals include many of the cat family e.g. tiger (above), bears, and various invertebrates.

Unstructured social groups provide protection from predators by reducing the possibility of being preyed upon individually. There may also be benefits during feeding and moving.

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Solitary animal

all animals must interact with others of their species (e.g. to reproduce or through competitive interactions for food or resources). Generally animals are classed as being solitary, in unstructured social groups, or in structured social groups.

Advantages of large social groupings

1. Protection from adverse physical factors and predators. 2. Assembly for mate selection. 3. Locating and obtaining food.

4. Defence of resources against other groups. 5. Division of labour amongst specialists. 6. Richer learning environment.

7. Population regulation (e.g. breeding restricted to a dominant pair).

Dominance hierarchies help distribute resources and maintain social structure. In some species (e.g. ants and bees), group members are divided into castes with specific roles. Some produce offspring or help raise young, others may be workers or help with defending the colony.

Possible disadvantages of large social groupings

1. Increased competition for resources between group members as group size increases. 2. Increased chance of the spread of diseases and parasites.

3. Interference with reproduction, e.g. infanticide by non-parents or cheating in parental care (as in brood parasites) so that non-parents may unknowingly raise another's offspring.

1. Give one advantage and one disadvantage of solitary living:

3. (a) Give two advantages of living in social groups:

(b) Give two disadvantages of living in a social group:

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2. Explain why group behavior, such as schooling, is more about individual advantage than group advantage:

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52 Social Organisation their fitness (survival and successful reproduction) and so are the products of natural selection. Many animals live in cooperative groups for all or part of their lives. Structured social species are those where individuals live together in an organised fashion and can be divided into eusocial and presocial groups. Social groups divide resources and activities between them and are mutually dependent.

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Key Idea: In social groups, members of the group interact regularly. Social species organise themselves in a way that divides resources and roles between group members. All behaviour has its roots in an individual's underlying genetic programme, but these innate behaviours are often modified by learning through experience, particularly social interactions. The behavioural adaptations of organisms contribute to

Eusocial animals

Worker

Termite queen

Soldier

Presocial animals

Presocial animals exhibit more than just sexual interactions with members of the same species, but do not have all of the characteristic of eusocial animals. They may live in large groups based around a single breeding pair and relatives (e.g. aunts/older siblings) may help raise the young. These groups often form hierarchies where the breeding pair are the most dominant. There may also be separate hierarchies for male and female group members. Examples include canine species that live in packs (e.g. wolves), many primates, and some birds. The number of males in a social group varies between species. In equines, a single stallion controls a group of mares. Young males are driven away when they are old enough. In elephants, the group is led by a matriarch, and the herd relies on her to make decisions in a crisis.

Female elephants and their offspring form small groups lead by the oldest female (the matriarch). Adult male elephants only visit the group during the reproductive season.

1. What is the difference between eusocial and presocial groups?

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2. Describe the organisation of a eusocial animal group:

3. In eusocial animals, worker and soldier castes never breed but are normally all genetically related. How might their contribution to the group help pass their own genes to the next generation?

4. Elephant herds are led by a single matriarch and consist of her daughters and their calves. The matriarch leads the herd to feeding and watering grounds. How does living as a group help the survival of the herd once the matriarch dies?

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USDA, PD

Eusocial animals are those in which a single female produces the offspring and non-reproductive individuals care for the young. They have the highest form of social organisation. Individuals are divided into different castes with specific roles. In most cases, a queen produces all the young and members of the group are normally directly related to the queen. Non-reproductive members of the group may be involved in care of the young, foraging, or defence of the nest site. Examples include ants, honey bees, termites, and naked mole rats.


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53 Cooperative Behaviour others (e.g. mobbing in small birds). Cooperation occurs most often between members of the same species. Altruism is an extreme form of cooperative behaviour in which one individual disadvantages itself for the benefit of another. Altruism is often seen in highly social animal groups. Most often the individual who is disadvantaged receives benefit in some non-material form (e.g. increased probability of passing genes onto the next generation).

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Key Idea: Cooperative behaviour is where two or more individuals work together to achieve a common goal. It increases the probability of survival for all individuals involved. Cooperative behaviour involves behaviour in which two or more individuals work together to achieve a common goal such as defence, food acquisition, or rearing young. Examples include hunting as a team (e.g. wolf packs, chimpanzee hunts), responding to the actions of others with the same goal (e.g. migrating mammals), or acting to benefit

Coordinated behavior is used by many social animals for the purpose of both attack (group hunting) and defense. Cooperation improves the likelihood of a successful outcome, e.g. a successful kill.

Animals may move en masse in a coordinated way and with a common goal, as in the mass migrations of large herbivores. Risks to the individual are reduced by the group behavior.

Kin selection is altruistic behavior towards relatives. In meerkats, individuals from earlier litters remain in the colony to care for new pups instead of breeding themselves. They help more often when more closely related.

Evidence of cooperation between species

Many small birds species will cooperate to attack a larger predatory species, such as a hawk, and drive it off. This behaviour is called mobbing. It is accompanied by mobbing calls, which can communicate the presence of a predator to other vulnerable species, which benefit from and will become involved in the mobbing.

One example is the black-capped chickadee, a species that often forms mixed flocks with other species. When its mobbing calls in response to a screech owl were played back, at least ten other species of small bird were attracted to the area and displayed various degrees of mobbing behaviour. The interspecific communication helps to coordinate the community anti-predator mobbing behaviour.

1. (a) What is altruism?

(b) Why would altruism be more common when individuals are related?

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2. How do cooperative interactions enhance the survival of both individuals and the group they are part of?

3. What evidence is there that unrelated species can act cooperatively? Why would they do this?

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72 Honeybees: The ultimate in unselfish behaviour? Kin selection explains the behaviour

Each female worker in the colony:

ffhoneybee males (drones) are haploid

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Are honeybees altruistic?

and females are diploid

ffsacrifices her life to defend the

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colony against danger

male genes and half the queen's genes

ffproduces no eggs

ffworkers are more closely related to

ffraises the young of the queen

Workers: female diploid The queen's daughters will share identical genes from the father and will share half the genes from the queen.

each other than they would be to their own daughters

fftherefore care-giving behaviour

Drone: male haploid

of sisters will increase faster than genes promoting investment in offspring.

Honeypot ants

Greg Hume at en.wikipedia CC 2.5

Honeypot ants of central Australia have a special group of workers called 'repletes'. These never leave the nest, but stay in underground galleries where they serve as vessels for storing a rich food supply. Regular workers that have been foraging for honeydew and nectar return to the nest where they regurgitate food from their crops to feed the replete. The replete will continue to accept these offerings until its abdomen has swollen to the size of a pea (normally it is the size of a grain of rice). The repletes become so swollen that their movements are restricted to clinging to the gallery ceiling where many hundreds of them hang in a row. When the dry season arrives and food supplies become scarce, workers return to the repletes, coaxing them to regurgitate droplets of honey.

4. (a) How does kin selection account for the evolution of apparently altruistic behaviour?

(b) Do you think such behaviour is truly self sacrificing? Explain:

5. How are honey pot ant repletes an extreme form of cooperation?

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54 How Cooperative Behaviour Improves Survival the chances of predation. Animals such as meerkats, ground squirrels, and prairie dogs decrease the chances of predation to others by having sentries that produce alarms calls when a predator approaches. Many animals live as family groups that help with foraging and raising the young.

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Key Idea: By working together (directly or indirectly) members of a group increase each other's chances of survival. However the level of help depends on the level of relatedness. Living in a group can improve the survival of individual group members, e.g. by improving foraging success or decreasing

Gunnison's prairie dogs (right) live in large communities called towns in the grasslands of western North America. The towns are divided into territories which may have up to 20 individuals in them. During foraging, above-ground individuals may produce alarm calls if a predator approaches, at which nearby prairie dogs will move to cover. However, whether or not an alarm call is given depends on the relatedness of the individuals receiving the call to the individual giving it. Gunnison's prairie dogs put themselves at risk when giving an alarm call by attracting the attention of the predator.

Percentage of occurrences when individuals gave alarm calls

60

Gunnison's prairie dogs

40

20

0

Non-descendent Offspring kin (e.g. cousins)

White fronted bee-eaters

1

2

Probability of helping

1.0

3 2 1

2

5 3 4 Adults in the nest

6

0.8 0.6

0.4

Stephen T. Emlen et al, 1995

Number of fledged chicks

4

0

Parent / siblings No known kin

0.2

0

0

0.125 0.25 Relatedness

0.5

White fronted bee-eaters (left) live in family groups which include a breeding pair and nonbreeding pairs. All adults help provide for the chicks. Graph 1 shows the relationship between the number of adults in the nest and the number of chicks fledged. Graph 2 shows how relatedness affects the amount of help the pairs give the chicks.

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1. Describe an example to show that living in a group improves survival:

2. The level of help between group members often depends on relatedness. Using the examples of the white fronted beeeaters and Gunnison's prairie dog, explain how relatedness to the helper affects the level of help given:

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74 The effect of the number of adults in the family on pup survival for black-backed jackals

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Number of pups surviving

5 4 3 2

Black-backed jackal (Canis mesomelas)

1 0

1

2

3

Number of adults

4

5

Black-backed jackals live in the brushland of Africa. Monogamous pairs (single male and female parents) hunt cooperatively, share food and defend territories. Offspring from the previous year’s litter frequently help rear their siblings by regurgitating food for the lactating mother and for the pups themselves. The pup survival results of 15 separate jackal groups are shown in the graph on the left.

SOURCE: Drickamer & Vessey, Animal behavior (3rd Ed) PWS, 1992

3. How might helping the offspring of a sibling to breeding age, instead of breeding yourself, improve chances of passing your own genes on to the next generation?

4. The graph at the top of this page shows how the survival of black-backed jackal pups is influenced by the number of adult helpers in the group. (a) Draw an approximate ‘line of best fit’ on the graph (by eye) and describe the general trend:

(b) Describe two ways in which additional adult helpers may increase the survival prospects of pups:

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5. How can a social behaviour that is beneficial to individuals in a species become more common over time?

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55 Cooperative Defence

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Key Idea: Working together in defence decreases individual risk and increases the chances of a successful defence. Group defence is a key strategy for survival in social or

herding mammals. Forming groups during an attack by a predator decreases the chances of being singled out, while increasing the chances of a successful defence

Red colobus monkey defence

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Group defence in musk oxen

Red colobus monkeys are a common target during chimpanzee hunts. They counter these attacks by fleeing (especially females with young), hiding, or mounting a group defence. The group defence is usually the job of the males and the more defenders there are, the greater the likelihood of the defence being successful.

100

Attack pattern by wolves

% chimp hunts successfully defended against

Young safely protected in centre

ATamari

In the Siberian steppes, which are extensive grasslands, musk oxen must find novel ways to protect themselves from predators. There is often no natural cover, so they must make their own barrier in the form of a defensive circle. When wolves (their most common predator) attack, they shield the young inside the circle. Lone animals have little chance of surviving an attack as wolves hunt in packs.

80 60 40 20

Circular defence with heads facing outwards

0

0

1 2 3 4 5 6 7 Number of male colobus defending

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1. Describe two benefits of cooperative defence:

2. How many colobus males are needed to effectively guarantee a successful defence against chimpanzees?

3. Sheep need to spend most of their day feeding on grass. They form mobs both naturally in the wild as well as on farms.

(a) Explain why sheep form mobs:

(b) Explain how this might enhance an individual sheep’s ability to feed:

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56 Cooperative Attack

Adrian A. Smith

Lionesses hunt as a coordinated group. Several lionesses hide downwind of the prey, while others circle upwind and stampede the prey towards the lionesses in wait. Group cooperation reduces the risk of injury and increases the chance of a kill. Only 15% of hunts by a solitary lioness are successful. Those hunting in a group are successful 40% of the time.

Many ant species, e.g. slavemaker ants (above left), raid other ant nests (called slaveraiding), killing workers and capturing grubs. The grubs are carried back to the home nest where they grow and tend the slavemaker ants' own young. Sometimes, however, the slaves rebel and can destroy the slavemaker nest. In his book Journey of Ants Edward O. Wilson, the world's leading ant expert, noted (not wholly tongue-in-cheek) that with ants "their foreign policy can be summed up as follows: restless aggression, territorial conquest, and genocidal annihilation of neighbouring colonies wherever possible. If ants had nuclear weapons, they would probably end the world in a week."

The Gombe Chimpanzee War

Group attacks between members of the same species and even the same social groups do occur. They usually involve disputes over resources or territory, but may be due simply to rifts in social groups. One of the most well recorded and startling examples of group fighting is the Gombe Chimpanzee War. Observed by Jane Goodall, the violence began in 1974, after a split in a group of chimpanzees in the Gombe Stream National Park, in Tanzania. The group divided into two, the Kasakela in the northern part of the former territory and the Kahama in the south. Over the course of four years, the Kasakela systematically destroyed the Kahama, killing all six males and one female and kidnapping three more females. The Kasakela then took over the Kahama territory. However, ironically, the territorial gains made by the Kasakela were quickly lost as their new territory bordered a larger more powerful group of chimpanzees, the Kalande. After a few violent skirmishes along this border, the Kasakela were pushed back into their former territory.

1. (a) Suggest two reasons for cooperative attacks:

(b) Suggest why cooperative attacks are more likely to be successful that individuals attacks:

2. Chimpanzees often hunt cooperatively. Use the data below to plot the relationship between hunting success and group size. No. hunters

1

2

3

4

5

6

Hunt success (%)

13

29

49

72

75

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Kalyan Varma

used by some species for raiding nests or territories in order to gain access to new resources (e.g. space or workers). Group attacks may be highly organised, with individuals taking specific roles.

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Key Idea: Working together in attack can help increase the chance of success especially if roles are allocated between the attacking members. Group attack is often used for hunting for food, but may be

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57 Cooperative Foraging capturing prey. Cooperative hunting will evolve in a species if there is a sustained benefit to the participants, the benefit for a single hunter is less than that of the benefit of hunting in a group, and cooperation within the group is guaranteed.

Worker castes in army ants

Cooperative foraging in ants often involves division of labour. Leaf-cutter ants harvest parts of leaves and use them to cultivate a fungus, which they eat. Workers that tend the fungus gardens have smaller heads than the foragers, which cut and transport the leaves. Similarly, army ants have several distinct worker castes. The smaller castes collect small prey, and larger porter ants collect larger prey. The largest workers defend the nest.

Honeybees forage for nectar, gathering it from flowers and taking it back to the nest. If a particularly good nectar source is found, the bee will perform one of two dances when it returns to the nest. If the source is distant the bee performs the waggle dance. If the food source is very close (less than 50 m) the honeybee will perform a round dance. The honeybee's round dance stimulates other workers to leave the hive and search within 50 m for a food source.

Army ants foraging

There are two species of army ant that have quite different raiding patterns (right): Eciton hamatum whose columns go in many directions and Eciton burchelli, which is a swarm-raider, forming a broad front. Both species cache food at various points along the way. Through group cooperation, the tiny ants are able to subdue prey much larger than themselves, even managing to kill and devour animals such as lizards and small mammals. This would not be possible if they hunted as individuals.

The mountain caracara in Peru (above) forages in groups of three or four, looking for prey hidden around rocks. Working together, the birds are able to overturn rocks far bigger than any individual could move. If a bird finds a rock that is worth turning over, it produces a high pitched call to attract the others. In most cases, only one bird (usually the initial caller) benefits from overturning the rock. However, the other birds may benefit when other rocks are overturned later (reciprocal altruism). Single, broad advancing front

Multiple advancing fronts

Food caches

Food caches

Swarm raider

Temporary nest

Temporary nest

Column raider

1. What are the advantages of cooperative food gathering?

2. What conditions favour group cooperation in food gathering?

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Alex Wild Public Domain

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Key Idea: Cooperative behaviour in gathering food increases the chances of foraging success and improves efficiencies. Cooperating to gather food can be much more efficient that finding it alone. It increases the chances of finding food or

3. Describe how the division of roles within ants increase the colony's success in obtaining food:

4. (a) Describe the advantages of reciprocal altruism in mountain caracara:

(b) Suggest why this a successful strategy even when birds do benefit all the time:

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58 Conflict in Social Groups which refers specifically to conflict situations between members of the same species. Agonistic behaviour includes all aspects of conflict, such as threats, submissions, chases, and physical combat, but it excludes predatory aggression. Agonistic behaviour is usually highly ritualised so that it is not easily misinterpreted. The ritualisation has an important role in reducing the risk of physical conflict and injury.

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Key Idea: Aggressive behaviour encompasses conflict over resources as well as predatory behaviour. Agonistic behaviour specifically refers to non-predatory competitive behaviour between conspecifics (individuals of the same species). Aggression is a complex phenomenon often associated with competition for resources, but it also includes predatory behaviour. Agonistic behaviour is a more precise term,

Fighting between social groups (e.g chimpanzee troops) can be extremely serious, even fatal. The fighting is usually over the defence or invasion of territories and resources.

Lions live in small prides of related females and one or two males. The dominant male's position may be challenged by nomadic males. Such challenges involve serious fighting with the winner displacing the loser from the pride.

Hooker’s (New Zealand) sea lion forms breeding colonies on several sub-Antarctic islands. A bull will set up a territory on one of the breeding beaches, defend it against challenges from other bulls, and attract females as mates to the site.

Many primates and birds form dominance hierarchies established by agonistic behaviour. Once the hierarchy is in place, little effort is required to maintain order in the group.

DoC

Aggression can occur between different species when they are competing for the same resources. In the photograph above, vultures are competing with hyaenas for a carcass.

Disputes between zebra stallions can get serious. The fighting is less ritualised than in many species and the force of the kick from the hind legs can cause serious injury. Face to face fighting may also result in serious bite injuries.

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1. Distinguish between aggressive behaviour and agonistic behaviour:

2. Describe how the following behaviours reduce the risk of injury to individuals in a population:

(a) Dominance hierarchies:

(b) Ritual aggression:

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3. Aggression is a complex phenomenon with many functions and causes. The table below provides a list of different categories of aggressive behaviour. Most of these behaviours involve conflict among members of the same species. These forms of aggression serve very different functions depending on whether they occur within or between species:

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Briefly describe the adaptive advantage of each of the types of aggression in the table in the column provided. Description

Adaptive advantage

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Type of aggression Territorial

Exclusion of others (usually of the same species) from some physical space.

Dominance

Control of the behaviour of another member of the same species.

Sexual

Threats and physical abuse of rivals, usually by males, to obtain or retain mates.

Parental

Attacks on intruders when the young are present and threatened.

Parent/offspring

Disciplinary action by parent against offspring (mammals).

Predatory

Act of predation, possibly including cannibalism.

Anti-predatory

Defensive attack by prey on predator.

Sibling

Attack by one sibling on another to exclude them from the litter/nest.

Competitive

Attack on a competitor to drive it away from a resource such as food.

4. Explain why, in social species, aggression between conspecific groups (e.g. one group invading another's territory) is often less ritualised and more inclined to lead to injury than aggression between individuals within the same social group.

5. Infanticide occurs in lions and Indian langur monkeys, and involves killing all the infants sired by other males. (a) Describe the conditions under which this behaviour would occur:

(b) Explain the adaptive value of this behaviour in terms of natural selection:

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59 Intraspecific Competition and its Effects become fewer and intraspecific competition increases. When the demand for a resource (e.g. food, water, nest sites) exceeds supply, that resource becomes a limiting factor to further population growth. Populations respond to resource limitation by reducing population growth rate (e.g. through lower birth rates or higher mortality).

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Key Idea: Members of a population compete for the same limited resources. Territories and hierarchies help to ensure that at least some individuals obtain sufficient resources. Intraspecific competition is an interaction in which individuals of the same species compete for a resource. As population numbers increase, the resources available to each individual

Scramble competition in caterpillars

In scramble competition, all individuals in the population have equal access to a limited resource and many individuals may starve. This limits population growth and can tightly constrain the life cycle events of some species.

Contest competition in wolves

Blue duck (whio)

In social groups, access to resources may be determined by the social hierarchy. The most dominant individuals have priority access to food, but low ranked individuals must contest the remainder and may miss out or may be forced to leave the group.

Competes with members of the same species.

Limited resources: Food Shelter Mates

Karora-Public Domain

The outcomes of intraspecific competition

In some vertebrates, defended areas, called territories, enable individuals or groups to command sole access to all the resources within a defined area. Blue duck pairs occupy and defend exclusive territories in the same stretch of river year after year.

Competes with members of the same species.

'Limited aggression' with threat displays at close range, sometimes with physical contact.

Escalation of threat by fighting. May involve pushing or combat using horns and antlers, biting, or kicking. Risk of injury is high. Fights may even be fatal.

Hierarchies

ff Determines an order of precedence for access to food, mates and breeding sites. Dominant animals have priority access to resources. ff May be linear (with pecking order) or may be complex and involve coalitions. ff Hierarchies enable individuals to concentrate on more productive uses for their energy (e.g. raising offspring).

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Territories reduce direct aggression by dividing resources between groups or individuals.

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A hierarchy is a ranked social order within a group. Hierarchies reduce direct aggression by creating orderly access to resources within a group.

Escalation of aggression Increasing risk of injury or death

Threaten from a distance using ritualised signals (such as calls and bellows) and displays.

Territories

Winner gains possession of resources

ff May be held by a single animal, a breeding pair, or a group. ff May be large multi-purpose territories for feeding, mating, and rearing young. ff May be used for a single purpose (e.g. mating grounds called leks). ff Boundaries are patrolled and marked using signals (calls, scent). ff Territories are effective in reducing intra-specific competition, but territory defence is costly (time and energy).

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81 1. (a) What is intraspecific competition?

(b) Why does intraspecific competition occur?

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2. Explain how intraspecific competition acts to limit population size:

3. Describe a type of aggressive behaviour that could serve each of the following purposes:

(a) Territorial defence from a distance:

(b) Maintenance of position in dominance hierarchy:

(c) Competition for the right to mate:

4. Describe two ways in which animals can reduce the intensity of intraspecific competition: (a) (b)

5. (a) Explain how a territory can reduce aggression between groups:

(b) What are some of the costs associated with defending a territory?

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6. (a) How can hierarchies reduce aggression between individuals in a social group?

(b) Discuss the benefits of a hierarchical system for the group (and species) and for individuals:

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60 Social Hierarchy in Pukekos Key Idea: Hierarchies in social birds can be determined by identifying the winners and losers in conflict situations. The pukeko is a relatively common New Zealand bird, typically found in swamps and marshes. In contrast to most other bird species which form mating pairs, pukeko cooperate as a group or 'commune' with coordinated activities. More than two birds will defend territory, court and copulate, lay in, incubate and defend a single nest, and feed and care for chicks. Most social animals establish a strict ranking order or hierarchy (sometimes called a pecking order) to reduce fighting between group members.

During activities such as feeding, some pukeko in close contact situations may avoid contact by taking food a short distance away from the others before eating. Other members of the group (the winners), chase away losers that come too close. In any encounter between two birds there is a winner and a loser. To determine if there is a social hierarchy, it is necessary to identify each bird individually and list them on two axes in the same order (see table below). One axis is then labelled the winner and the other, the loser. Results showed that males dominate females, and older birds dominate younger birds. The social organisation of a stable group is dependent on the fact that these birds act at all times in accordance with their status. Chicks are initiated into the hierarchy at a very early age.

A pukeko showing its white tail feathers used as a 'flag' in signalling alarm, aggression, and submission.

This material has been reproduced with kind permission of Dr. John Craig, University of Auckland. It has been modified from part of the Senior Biology Resource Unit: The Pukeko.

Outcomes of 246 meetings between individual pukeko in a population of seven birds

1. Circle the square on the chart (on the right) in which this context appears: pukeko W6 defeats pukeko B6.

Winner

W6

2. Complete the summary in the table below for the four birds:

2F

L9

W3

L8

2

3

B6

W7

W6

Pukeko

No. won

No. lost

Total

% Won

Loser

W6 L9 L8

W7

2F

13

L9

29

23

W3

19

12

9

L8

15

9

13

7

B6

18

3

5

6

11

W7

12

1

4

3

13

1

6

9

4. What is different about the results for L9, W3, and B6?

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3. How does the organisation of the table (above right) reflect the social rank of each pukeko?

5. Explain what these unexpected results mean in terms of what happens when for example, B6 meets W7:

6. W6, 2F, and L9 are adult males and W3, L8, and B6 are adult females. Explain the relationship between sex and status in this group of pukekos:

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7. W7 is a young male. What factor, besides sex, could influence status in a group? Explain your answer:

A complete stranger, a male pukeko called R1, was adopted by the group for territorial defence. The table below shows the result of encounters between the new bird and others in the group immediately after the adoption. Each encounter is represented by a dot in the appropriate square.

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The outcomes of encounters between a new bird (R1) and the rest of the group Winner

W6

2F

L9

W3

L8

B6

W7

R1

W6 2F

Loser

L9

W3 L8

B6

R1

8. Between which two birds does R1 probably rank?

9. Predict the probable result of an encounter between R1 and W3:

10. What factors might be important in the maintenance of a stable hierarchy within the group?

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11. (a) Describe the effect of social status on the outcome of interactions between members in a hierarchy:

(b) Describe the benefits to social animals of having a hierarchy to control social interaction:

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61 Monkey Hierarchy

Cornflake

Pepper

Salt

Mustard

Marmalade

Vinegar

Coffee

Tea

Peanut

Crisp

Peanut

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bit the other monkeys. The monkeys were named to assist in identification. The result is the table below. An example of how to use it is as follows: Peanut bit the monkey named Coffee 26 times, but Coffee did not bite Peanut at all.

13

5

0

14

0

25

9

0

0

8

0

22

0

0

17

0

0

0

Crisp

Cornflake

0

0

Pepper

14

4

2

0

0

0

0

0

0

0

1

0

6

3

27

0

Salt

0

0

10

0

0

0

18

0

0

Mustard

8

1

2

32

0

Marmalade

0

22

8

0

15

2

20

0

15

0

0

0

0

4

0

Vinegar

0

0

13

0

3

0

0

Coffee

26

8

4

0

10

0

17

7

Tea

7

1

2

24

1

41

2

1

Most dominant

Hierarchy of monkeys biting

0

12

Most subordinate

1. How many times did Salt bite Crisp?

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Most subordinate

5. Determine whether one particular monkey was bitten by all the other monkeys (if so, which one):

Hierarchy of monkeys bitten

4. Determine whether one particular monkey bit all the other monkeys (if so, which one):

Most dominant

2. How many times did Crisp bite Salt?

3. Arrange the monkeys in a hierarchy on the table to the right (with the dominant one at the top and the subordinate one at the bottom). Enter the frequency of the biting for each combination of monkeys. HINT: Do this in pencil to allow corrections or work it out on a piece of refill paper first.

6. State whether there is any monkey that shows signs of challenging a more dominant monkey for a higher position in the hierarchy. If so, name the monkey:

7. Determine if there is a pattern to the frequency of biting other monkeys once the group has been placed in descending order of dominance:

8. What type of hierarchy do these monkeys have? WEB

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Source: Beginning Biology, R. Price, CUP 1983

Key Idea: Hierarchies in primates can be determined by identifying the winners and losers in conflict situations. In an investigation of the behaviour of ten captive monkeys, a researcher recorded the number of times each monkey

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62 Hierarchies in Baboons females. Females also have hierarchies but these are often based on mother-daughter relationships. Once established, hierarchies are usually maintained by gestures, facial expressions (e.g. yawning to show canine teeth), and ritual aggression. Fighting usually occurs when one male wishes to increase his status and rise in the hierarchy.

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Key Idea: Dominance hierarchies help maintain social order and reduce conflict. Baboons have a highly developed social structure with a dominance hierarchy. Dominance hierarchies are most commonly seen in males, who are usually not related and aggressively compete over higher positions and access to

ffOlive baboons (Papio anubis) live in the savannah regions of Africa and have a

highly organised and complex social structure. Within a troop of baboons (see below) an orderly hierarchy promotes division of labour within the group, reduces conflict, and maximises the efficiency with the which the group can search for food and defend itself against predators and other troops.

ffThe adult males are distinguished by their large size and well developed manes.

Females with babies are positioned near the centre for protection. The two females in oestrus move in consort with the most dominant males. All males (with the exception of the dominant males) tend to be positioned on the edges of the group. Should any threat be encountered in their march, the dominant males will move to the front, with the subordinate males in support. The females, adolescents and babies move to the rear, away from the threat.

Females with young

Female in oestrous

Dominant male

Subordinate adult male

Subordinate adult male

Adolescents

Female in oestrous

Dominant male

Source: Hall and De Vore, 1965

1. Explain how an individual baboon (regardless of its social ranking) may be more protected by being within the troop:

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2. Describe one feature of the social structure of the baboon troop that gives additional protection to its members:

3. Baboons have some of the most ferocious canine teeth of all primates, and are capable of inflicting massive injuries. Explain how a dominant baboon male keeps order in his troop without maiming:

4. (a) How might a subordinate male improve his status in the hierarchy?

(b) What resources would he gain by doing this?

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63 Territories and Home Ranges and for a single purpose, e.g. mating grounds called leks. Home ranges are usually much larger that territories. They are not defended and may overlap with the home ranges of other members of the species. This means that even solitary animals can remain in contact with others.

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Key Idea: Territories are defended regions, whereas home ranges are generally larger areas that are not defended. A territory is the area occupied by an animal and defended against intruders. Territories may be large and multi-purpose for feeding, mating, and rearing young, or they may be small

Overlap

Nest

The home range is the area where an animal may roam but does not defend. It may overlap with several other home ranges.

The area where the animal spends most of its time is called the core area and usually contains the best resources.

Territories are actively defended and, once established, provide relatively undisputed access to the resources within. (e.g. food, shelter, water, nest or den site). Territories may be established by fighting and are marked by calling or using scent marks.

Territory size depends on a many factors including resource availability, the social behaviour of the animal, and the energy expended to defend it. Gannet territories consist of the nest and the area immediately around the nest. The home range consists of the ocean covered when searching for food.

A lek is an aggregation of males engaging in competitive displays. Males defend their lek territories, which are usually established seasonally. Females select mates based on their display or position in the lek. Highly ranked males occupy the middle of the group with lower ranked individuals on the periphery.

Ownership of a territory is usually continually proclaimed. Male skylarks (above) may sing for twenty minutes at a time while flying high above their territory. Maintaining a territory benefits an animal by maintaining access to a resource, e.g. a nesting site or food source.

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1. (a) Distinguish between a territory and a home range:

(b) Describe how the core area is similar to the territory:

(c) What aspects might determine the size of the home range in any given area?

2. Establishing and maintaining a territory takes time and energy. Describe its adaptive value to the organism:

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Lekking in greater sage grouse


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64 Home Ranges and Resources in Baboons

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Key Idea: Baboon troops occupy home ranges that overlap but have distinct core areas. Olive baboon troops in Africa each occupy distinct home ranges. The home range is the area regularly utilised by the

troop, and it provides all the resources the troop needs for its survival. Home ranges differ from territories in that they may overlap in places and are not necessarily defended. The size of the home range reflects the quality of its resources.

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Baboon home ranges in Nairobi Park

Scale

0

Key

5 km

Sleeping trees Home ranges

(each range shown by different dash pattern)

Core areas

Nairobi Park boundary

This map shows the boundaries of home ranges of different olive baboon troops living in the Nairobi Park, Kenya. Each has its own resident population of baboons that can range from 20-80 in number. Savannah-dwelling baboons spend more time on the ground than do most other primates and have one of the largest home ranges, averaging 20 km2. Baboons may travel up to 4 km a day in search of food. Most of the troop's activity is concentrated in the core area (which is like a territory). This area contains the best food sources, and more importantly, water holes and trees for sleeping in at night. Although olive baboons spend nearly all of their day on the ground, they always return to the safety of the trees before dusk to sleep.

1. Why would baboons defend the core areas aggressively?

2. (a) How many home ranges are represented on the map above?

(b) Contrast the distribution of home ranges and core areas of neighbouring troops. Suggest a reason for the difference:

Home range size (km2)

Average troop size

Bole Valley, Ethopia

1.1

20

Mixed forest and grassland

2000

Ishasa, Uganda

4.0

60

Forest and shrub-land

1200

Gilgil, Kenya

19.7

49

Open grassland and shrub-land

750

Laikipia Plateau, Kenya

43.8

100

Dry grassland

500

Region

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Yearly rainfall (mm)

Habitat

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http://pin.primate.wisc.edu/factsheets/entry/ olive_baboon

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3. The table below summarises troop size and home range size in various baboon troops in Africa. Use the information in the table to describe how the environmental factors affect the home range of baboons:

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65 Home Ranges in Karearea Key Idea: The size of a home range depends on the resource density. Home ranges are larger when resources are scarce.

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Defended areas reduce competition

The New Zealand falcon or karearea is New Zealand's only endemic bird of prey. It catches its prey (mainly small birds) on the wing and rarely eats carrion (dead animals). It is aggressive and territorial, but is vulnerable to introduced predators because it nests on the ground in a simple scrape in the soil. Research (Seaton, 2007) showed that the reproductive success of NZ falcons is much higher in commercial pine forests with a mix of different aged stands than in native forest. Moreover, territories in pine forests are much smaller than in native forest. This might seem surprising, but the pine forest habitat supports a large number of small bird species as prey.

Summary facts

Pine Stand Age Class Less than 4 years 4 to 9 years

10 to19 years

More than 20 years

0

0.6 1.2 Kilometres

Falcon nests 2005-06

Home ranges of four adult male NZ falcons in the Kaingaroa Forest during the 2005 breeding season (August-March). Forest composition (age of pine stands) is shown in the key. During the breeding season, the entire home range is defended, making it like a large territory.

► The home range size of falcons in the Kaingaroa pine forest (9 km2) is much smaller than the 75 km2 recorded for native forest.

► Prey availability is enhanced in pine plantations by high densities of prey congregating along pine stand edges. ► Falcons made the most successful hunting attempts along pine stand edges between stands less than 4 years old and more than 20 years old. ► Prey availability is also high in open stands where prey is more vulnerable to attack.

► Stands less than four years old made up the largest proportion of the falcon home ranges. Old stands provide necessary cover from which to launch attacks over the more open younger stands.

1. Explain how the defence of home ranges by the karearea could reduce competition for resources:

3. Look at the map of home ranges above.

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2. What evidence is there to suggest that pine forest habitat might be more suitable for karearea than native forest:

(a) What habitat feature do all the home ranges have in common that is important to karearea?

(b) Where do the karearea prefer to nest? Can you suggest why?

4. On a separate page, discuss how you might manage a forest to enhance the conservation of karearea? LINK

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Scott McDougall

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Thanks to Dr Richard Seaton, Wingspan Birds of Prey Trust, for use of material from his PhD thesis "The ecological requirements of the New Zealand falcon (Falco novaeseelandiae) in plantation forestry" (2007), Massey University.


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66 Yellowhead Territories 1984-5 W G (K)

1985-6

Bush

QR XY

QR

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Key Idea: Territories can be occupied by cooperating individuals, which help to support a breeding pair.

Yellowhead Mohoua ochrocephala

Yellowheads are endemic to New Zealand and are highly territorial in their behaviour. They are cooperative breeders, forming breeding groups that occupy a single territory each. Each group contains a primary pair that breed, and secondary birds that act as nesting helpers. Secondaries do not take part in breeding but provide additional food for the clutch. The diagrams on the right show the changes in locations of yellowhead territories and their occupants in a Fiordland beech forest (at Knobs Flat) over a four year period. The yellowheads occupied all available space and had fairly exclusive territories in which they did almost all their feeding. The letters and numbers are the codes for banded birds.

OP

EF

Open ground

AB

(X) X

ST

Z1

ST

AB

Z1

0

100

metres

1986-7

EF (G)

Q (XY)

4

HI (JLM)

K

1987-8

O

Q (XY)

O

23

L

I

FG

C

C (U)

23

J

M

N

N

Obscured bush margin

Member of primary pair

CD

V

Nest site

X

4

EF (G)

CD

Territory boundaries

Codes for banded birds using X as an example:

HI (JKLM)

H (IJ)

Source: Graeme Elliott, Ecological Consultant

Key

W

OP

AB

U

ST

AB

ST

Secondary non-breeding bird Fledgling (juvenile)

1. Give the approximate dimensions of an 'average' territory (see scale on diagram):

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2. Compare the home range of the yellowhead with its territory:

3. Secondary birds do not breed. What is the adaptive advantage to them of remaining in the territory of the primary bird?

4. What is the likely cause of bird N reducing its territory by about a half in 1987-8?

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67 Breeding Behaviour or the chance for successful reproduction may be missed. The short time period that most sexually reproducing animals have in which to breed creates strong selective pressure for behaviour that improves the chances of reproductive success (therefore fitness). Breeding pairs often establish territories to ensure reliable access to resources during breeding, while ritualised courtship behaviours reduce conflict between the sexes so that mating is achieved without injury.

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Key Idea: Behaviours associated with breeding, such as courtship, are adaptations to ensure reproductive success. Many behaviours in animals, including territorial behaviour, are associated with reproduction, reflecting the importance of this event in an individual's life cycle. Most animals breed on an annual basis and show no reproductive behaviour outside the breeding season. When the breeding season occurs, reproductive signals must be given and interpreted correctly,

What is courtship? ffCourtship refers to the behaviour of animals just before, during, and just after mating. Courtship is a way for both male and female to evaluate the health, strength, and potential fitness of a possible mate.

ffA potential mate may initially be attracted by a call (e.g. male frog calling).

The caller (usually male) may then perform a more intricate display once the responder (usually female) arrives. In other cases the male's call and display may be the same performance.

is relatively common in insects, such as empid flies (right and below). Sometimes the male himself is unwittingly the "gift of food", such as in praying mantises in which the male is invariably eaten during mating. This behaviour is also common in spiders.

Prey

Onno Zweers cc 3.0

+

ffSometimes the male may attract a mate by offering a gift of food. This

Do females chose mates? ffMate choice (or intersexual selection) occurs where members of one

biological sex choose mates of the other sex to mate with. Where there is mate choice, one sex competes with same-sex members and the other sex chooses. This competition often involves elaborate rituals, calls, and displays to the choosing sex.

ffFemales usually have more invested in offspring so their mate choice

is important and they are often the choosy sex. Female preference for certain features, e.g. eyes on peacocks tail, is thought to be behind the elaborate structures and displays that have evolved in many species (e.g. peafowl, right).

Courtship is a often crucial part of breeding behaviour

Courtship gift The male gives the female a meal (an insect wrapped up in a cocoon) to keep her occupied while he mates.

FEMALE

MALE

Male hangs on The male empid fly grips on to a twig with its front legs during mating. It uses the other four legs to grip on to the female.

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Female empid flies are aggressive hunters, so males have to be careful about how they approach them. Ritualised courtship behaviour by the male helps him to be accepted by the female as a mate. The male's gift of food for the female pacifies her during mating and is a crucial component of mating success.

Lock and key The empid flies lock the tips of their abdomens together so that the male's sperm can enter the female. If the sperm were exposed to the air, they would dry out and die.

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91

In birds, song is an important mechanism for attracting a mate and proclaiming ownership of a territory. The song also acts as reproductive isolating mechanism, as differences between the songs of two species enables individuals to recognise their own species and mate only with them. Kakapo are a lek species and males attempt to attract a mate to their lek (breeding territory) by producing a low frequency booming sound during the breeding season that can be heard over many kilometres of forest. When a female arrives the male begins a display in which he spreads his wings and rocks side to side.

One of the functions of courtship behaviour is to synchronise the behaviours of the male and female so that mating can occur, and to override attack or escape behaviour. Although courtship rituals may be complex, they are very stereotyped and not easily misinterpreted. Males display, usually through exaggerated physical posturing, and the females then select their mates. Courtship displays are species specific and may include ritualised behaviour such as dancing, feeding, and nest-building. Many birds may form life long bonds (e.g. albatross above) and renew these every year by displaying to each other when they arrive at breeding grounds.

1. (a) Why might courtship behaviour be necessary prior to mating?

(b) Why is courtship behaviour is often ritualised, with stereotyped displays?

2. Describe two aspects of mating behaviour in empid flies that help to ensure successful mating: (a)

(b)

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3. (a) Why is choosing the best mate particularly important for females?

(b) Explain how female choice could lead to elaboration of structures and displays in males:

(c) In some species the female is unable to choose a mate. Elephant seal males fight for the right to mate with a female and defend a harem. Females arriving at the beach often try to avoid the harem, but with males being up to four times heavier this is difficult. How does this system ensure the offspring are likely to have the best genes?

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92

68 Reproductive Strategies extreme, most invertebrates expend their total reproductive effort in producing eggs and sperm and there is no parental care. At the other extreme, mammals invest heavily in a small number of offspring and the parental care cost is substantial. Between this is a continuum, with some animals adopting alternative strategies, such as brood parasitism. No strategy is necessarily 'better' than any other. They are different solutions to the problem of successful reproduction.

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Key Idea: The way in which an animal allocates its reproductive effort is part of its reproductive strategy. Effort can be expended in producing offspring or caring for them or both. Different strategies carry different costs and benefits. The reproductive effort is the amount of energy allocated to reproduction (production and care of young). Of the total reproductive effort, the amount remaining after production of the offspring can be allocated to parental care. At one

Low risk to parents

Low percentage of offspring survive to reproductive age

Few eggs or young produced

Low mortality

Moderate to low risk to parents

High percentage of offspring survive to reproductive age

e al car rent Pa

Low mortality

Moderate number of eggs produced

ts -paren non by re Ca

.

l care enta par No

High mortality

Many eggs or young produced

Higher risk to parents

High percentage of offspring survive to reproductive age

Parental care

ff Moderate number of offspring. ff Reproductive effort per offspring is moderate to low. ff Rely on others to raise offspring. ff Risk of egg loss is mitigated by distributing eggs amongst a number of hosts. ff Examples: some birds, insects, and fish.

ff Few offspring. ff Reproductive effort per offspring is high. ff Moderate to substantial care of offspring. ff Large reproductive effort put into raising offspring to a less vulnerable stage. ff Examples: most birds and mammals, some fish.

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Brood parasites

ff Large number of offspring produced. ff Reproductive effort per offspring is low. ff Little of no parental care of offspring. ff Reproductive effort is put into producing the offspring, not parental care. ff Examples: most fish, amphibians, reptiles, and invertebrates.

flowergarden.noaa.gov

Little or no parental care

Broadcast spawning involves no parental investment after the gametes are released.

A shiny cowbird chick is fed by its host parent, a smaller rufous collared sparrow.

Mammals have a high level of investment in offspring before and after birth.

Many invertebrates allocate all their reproductive effort to producing offspring and there is no parental care. Broadcast spawners such as clams and corals (above), release millions of gametes into the water. Very few of the planktonic larvae will survive. This is the most common reproductive strategy in the oceans and is typical of most marine invertebrates and many fish. Many amphibians are also broadcast spawners although there are many exceptions, including New Zealand's native frogs (Leiopelma) in which the males carry the offspring on their backs.

Brood parasitism is a strategy adopted by some birds, notably cuckoos and cowbirds. The brood parasite removes an egg from the nest of a host species and lays one of its own in its place. To reduce the risk of eggs being discovered and destroyed, the eggs are spread around a large number of hosts. Most avian brood parasites have short incubation times, so the egg hatches before those of the host and the imposter will eliminate all or most of the host's eggs/nestlings. The host then raises the parasite chick as if it were its own, even when the chick is larger and differs in appearance. The strategy is not without risk only about half of the parasite's young survive.

Both mammals and birds are well known for their high levels of parental care and mammals also have a high level of prenatal investment. Other vertebrates, such as some amphibians, fish, and reptiles also provide care until the offspring are capable of fending for themselves. Bird parents are required to incubate their eggs in a nest and then feed the chicks until they are independent. Although most mammals give birth to well developed offspring, they are dependent on their mother for nourishment via suckling milk, as well as learning behaviours essential to their survival.

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93 The significance of reproductive investment ffProducing offspring demands enormous amount of energy and

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risk. In many vertebrate species, reproduction is almost entirely up to the female (males contributing only sperm) but in other species the male also provides support (e.g. by defending a territory or providing food for the female. important that she has the best possible reproductive outcome each time she mates, and mate choice is critical. In general, females have a limited reproductive outcome and can only produce so many eggs or offspring in a lifetime. For example, a human female produces one egg a month for about 40 years, a maximum of ~480 eggs in a lifetime. Given that gestation and breast feeding (which suppresses ovulation) may take two years, only about 20 children can be raised in the average lifetime (the record is reportedly 69).

Small cc 2.0

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ffBecause the female is most heavily invested in the offspring, it is

In kaka, both parents are needed to successfully rear the chicks. Monogamy is a common mating system when biparental care is needed for offspring survival.

ffMales, on the other hand, have less invested in offspring. They

produce sperm continuously and put no direct energy into the offspring until at least birth or egg laying. Potentially males could fertilise unlimited numbers of females and so produce far more young without any additional effort.

ffThese differences in reproductive investment have been important in the evolution of mating systems, e.g. monogamy, with animals adopting strategies that maximise reproductive success in their particular physical and social environment.

A New Zealand sea lion male keeps a harem of up to 25 females and their young, which he protects.

1. Describe the different ways in which animals can allocate their total reproductive effort:

2. Animals with parental care protect the investment they have already made in offspring. Explain how factors in the environment (e.g. food resources and risks to young) might influence how much care is provided by each parent:

3. (a) What might be the benefits of a brood parasitism strategy to the brood parasite?

(b) What adaptations of the brood parasite help to maximise the success of its strategy?

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3. The shining cuckoo (Chrysococcyx lucidus) is the world's smallest cuckoo. It is a summer migrant to New Zealand, where it is a brood parasite of the much smaller grey warbler (Gerygone igata). It usually parasites second broods, arriving in New Zealand after the grey warblers have already begun breeding. The female shining cuckoo removes one host egg per nest, laying one of her own in its place. After hatching, the cuckoo chick ejects all grey warbler eggs and/or nestlings from the nest and is raised alone.

Explain how the cuckoo's strategy of parasitising the second broods of grey warblers contributes to the continuing success of the cuckoo in its niche:

The shining cuckoo

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94

69 Mating Systems and Parental Care systems offer different reproductive advantages to the individuals involved and are determined in part by the social structure of the species. Each particular mating system is usually associated with a certain pattern of parental care and is closely tied to the resources available for breeding.

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Key Idea: The life histories, mating systems, and parental care behaviours of animals have evolved to maximise reproductive success in a particular environment. A mating system describes which males mate with which females, under which circumstances. Different mating

Dotted arrows represent failed attempts at mating between males (M) and females (F). Dashed outlines surround unmated individuals

Mating system and behaviour

Parental care

Advantages

After mating, males frequently show no parental care. Parental care is left to the female.

The best or strongest male is selected for breeding. This provides the offspring with the best genes (at least from the male).

Polygyny

Males control access to more than one female. Males are often territorial and may control access to females directly or by defending valuable resources. In lek polygyny, females select mates from groups of males based on the quality of the male’s display or territory.

Examples: Most mammals

Polygynous: Elephant seal

Monogamy

A breeding pair forms a partnership for the breeding season or for life. Neither sex can monopolise more than one member of the other sex.

Both parents look after the young. Examples: 90% of bird species

Likely when the habitat contains scattered, renewable resources or scarce nesting sites. Shared care spreads risk and improves survival of young.

Monogamous: Emperor penguin

Polygynandry

An organised association of several males and females, and multiple mating takes place between group members. Mating activity is not equal (some males mate more often than others).

All group members contribute to the care of the young.

Increases genetic diversity and decreases male competition for mates and aggression towards the young.

The males may care for their own offspring. The female abandons the male, leaving them to incubate the eggs and care for the young.

In species where the males provide prenuptial gifts, females gain nutritional benefit. Genetic benefits and higher offspring survival rates may also result from this system.

Polyandry

Female mates with more than one male. Polyandry occurs in some mammals (cats) and birds, and in eusocial insects and mammals (mole rats). In birds, the female forms very brief associations with males, and mates with several males in succession.

Polygynandrous: Pukeko

Polyandrous: Emu

(a) Polygyny:

(b) Polyandry:

(c) Polygynandry:

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1. Describe the adaptive value of each of the following mating systems:

(d) Monogamy: 2. What factor might be important in determining which sex cares for the young and why?

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95

70 Territories and Breeding Behaviour territory defence are higher. Establishing a territory uses energy and effort, but the benefit is the exclusive access to resources. During the breeding season males in particular spend time defending a territory with the goal of attracting a female and reproducing. In many cases, where territories are established purely for breeding purposes, the position of the territory is often the most important factor.

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Probability of mating

0.7

0.6

0.5 0.4

Martin Bergman et al 2007

The speckled wood butterfly is found throughout northern Eurasia and Africa. During the breeding season, males have two breeding strategies. Dominant males defend a patch of sunlight in a wood, while others fly through the forest looking for unmated females. Studies have shown the males defending a territory have a greater chance of mating. This is appears not to be because these male are more desirable per se but that they are more able to spot females flying through the sunlight than males with no sunlit patch.

0.3 0.2 0.1 0

Non resident

Resident

Charlesjsharp CC 4.0

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Key Idea: Territories are not always permanent and may be established only during the breeding season. Territories are most often established in the breeding season, usually spring and summer. In autumn and winter, migratory animals leave their territories and return to winter grounds. Other animals that do not migrate may still only defend a territory during the breeding season, when the benefits of

10 m

Lekking is a relatively common breeding behaviour. Lekking areas (arenas) often contain numerous males. In most cases the more dominant males have leks in the centre of the arena. The diagram right shows a schematic of a greater sage grouse lek arena. The most dominant (alpha) male (A) is found in the middle.

D

D

A

B

C

E

A

B

E

D

E

C

C

B

D

B

D

D

C

E

E

Lek mating arena

3 2

0

0

Distance to lek centre (m)

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1

1000

Snake3yes CC 2.0

Jakob bro-jørgensen & Sarah m. Durant 2003

Topis are antelopes found on subSaharan grasslands. They establish leks during the mating season (March to May). Studies have shown that the closer the male is to the centre of the lekking arena the larger the number of females that are mated with per day.

Females mated daily

4

1. Use examples to support the statement that the position of a territory can be important for reproductive success:

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LINK

66

LINK

63

WEB

70

KNOW


96

71 What You Know So Far: Intraspecific Relationships Hierarchies

HINT: Why do hierarchies form and how do they enhance survival?

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you: Cooperative behaviour

HINT: How does cooperative behaviour improve survival?

Breeding behaviour and parental care

HINT: Distinguish between territories and home ranges. Explain the role of territories in resource acquisition and group (or pair) survival.

HINT: Explain the role of ritualisation in breeding behaviour. How is reproductive effort apportioned and what are the costs and benefits of parental care?

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Territories

REVISE

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97

72 NCEA Style Question: Cooperative Behaviour Cooperative hunting in chimpanzees

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Chimpanzees benefit from cooperative hunting. Although they may hunt alone, they also form hunting groups of up to six members or more. Chimpanzee hunts differ from the cooperative hunting of most other animals in that each chimpanzee in the hunt has a specific role in the hunt, such as a blocker or ambusher. Studies of chimpanzee hunting show that different groups employ different hunting strategies. The hunt information in table 1 (below) was gathered from chimpanzees in the Tai National Park in Ivory Coast. Number of hunters 1

Number of hunts 30

Hunting success (%) 13

Meat per hunt (kg) 1.23

Net benefit per hunter (kJ) 4015

2

34

29

0.82

1250

3

39

49

3.12

3804

4

25

72

5.47

5166

5

12

75

4.65

3471

6

12

42

3.17

1851

>6

10

90

9.27

5020

The hunt information in table 2 (below) was gathered from chimpanzees in the Gombe Stream National Park in Tanzania. Number of hunters

Number of hunts

Hunting success (%)

Meat per hunt (kg)

Net benefit per hunter (kJ)

1

30

50

1.23

4245

2

13

61

1.85

3201

3

9

78

1.61

1837

4

7

100

2.86

2494

5

1

100

3.00

2189

6

2

50

2.00

861

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1. Use the information in the tables to discuss the differences between the two groups of chimpanzees in the extent of cooperation and how it relates to hunting success. Your discussion should include an evaluation of the results and a justification of your main points based on the data.

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TEST


98 Sharing and bonding in chimpanzees

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In Tai chimpanzees, hunting is a chance to form social bonds. Study the information below showing the number of chimpanzees taking part in a hunt and eating afterwards and the mean (average) number of bystanders during the hunt and eating afterwards. 2. Explain what the information is showing and discuss the reasons why this might occur: Mean number of hunters eating

Mean number of bystanders

Mean number of bystanders eating

1

0.7

3.5

3.0

2

1.6

3.6

2.6

3

2.5

3.6

3.0

4

2.5

2.7

2.1

5

3.5

2.7

2.3

6

4.7

2.4

2.2

Christophe Boesch 1994

Number of hunters

0.10

0.12

Female

0.10

0.08

0.08

0.06

0.06

0.04

0.04

0.02

0.02

0

Pup in burrow

Pup in group

0

Male

Pup in burrow

Santema and Clutton-Brock (2013)

The graphs (right) show the likelihood of female or male meerkats standing sentinel when pups are either in the burrow or outside in the sentinel's group. The scale represents a statistical measure from a large number of observations. Error bars are Âą SE.

0.12

Pup in group

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Meerkats are highly social carnivores that live in mobs consisting of a dominant (alpha) breeding pair and up to 40 subordinate helpers of both sexes who do not normally breed but are usually related to the alpha pair. They are known for their sentinel behavior, watching for predators and giving alarm calls when they appear.

Likelihood of sentinel behavior

Sentinel behavior in meerkats

3. Discuss the evidence that meerkat sentinel behaviour is altruistic. In your answer, you should evaluate the data and justify your conclusions:

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99

73 NCEA Style Question: Territories North

Tai chimp territories are particularly large and well supplied with food compared to other chimpanzee territories. Males from Tai North spend nearly a third of their time patrolling the territory. Tai middle chimps engage in defensive activity more often than either Tai North or Tai South.

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1. Chimpanzees live in family groups. Males help defend the territory from other family groups. The territories of three family groups of chimpanzees (Tai North, Tai middle, and Tai south) are shown below.

N

South

Centre of activity

1 km

Discuss the territorial behaviour of the Tai chimpanzees. Your discussion should include: • The difference between territories and home ranges • The reasons for patrolling and defending a territory • An explanation of the level of patrolling effort and encounters between the chimpanzee groups.

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Middle

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TEST


100

74 KEY TERMS AND IDEAS: Intraspecific Relationships 1. Match the following words with their definitions: A A social structure in which there is a linear or near linear ranking of individuals in the group; each animal is dominant over those below it and submissive to those above it.

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agonistic behaviour altruism

B The area habitually occupied by an animal but not necessarily defended.

communication

C Interaction in which a resource is contested.

competition

D Social behaviour related to fighting, such as aggressive or submissive behaviours, but excluding predatory aggression.

cooperative behaviour

E A defined area, used by an animal for a specific purpose, delineated in some way (e.g. by scent) and defended against individuals of the same species.

courtship

F Behaviour in which an animal sacrifices its own well-being for the benefit of another animal. Usually evident in kin.

dominance hierarchy

G The transmission of (understood) information between individuals of the same species. Can be by vocal, visual, or olfactory means.

home range

H Behaviour that acts as a prelude to mating and reproduction. It may involve a suite of visual, auditory, chemical, and postural cues.

intraspecific competition

I The working together of individuals in order to reach a common goal, e.g. the gain of resources to enhance survival.

kin selection

J Strategies (e.g. behavioural and reproductive) that favour the reproductive success of an organism's relatives, even at a cost to their own survival and/or reproduction.

territory

K Competition occurring within members of the same species.

2. Draw lines to match up the first half and second half of the sentences below: Cooperative behaviour in a group …

Cooperative behaviour evolves when there is a …

… sacrifice their individual reproductive chances to ensure the collective's genes (and therefore their own genes) are passed to the next generation.

By displaying altruistic behaviour to family members, an individual can indirectly increase …

… the likelihood of their own genes being passed on to the next generation.

Cooperation has been taken to the extreme by eusocial animals in which the majority of members of the group …

… benefits all members of that group.

… sustained benefit to the members of the group.

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3. Explain how altruistic behaviour between closely related individuals benefits the survival of all participants:

4. Orcas (killer whales) hunt seal on icebergs by swimming towards the iceberg in a group at high speed before ducking under the ice causing a large wave to wash over the iceberg, knocking the seal into the sea where it can be captured.

Identify the type of behaviour displayed by the orcas and the adaptive value of this behaviour:

TEST

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Evolutionary processes leading to speciation

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Achievement Standard

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3.5

Key terms

Micro- and macroevolution involve the same processes on different time scales. Microevolution refers to changes in the allele frequencies of populations as a result of mutation, natural selection, genetic drift, and gene flow. Macroevolution involves the formation of new species, new genera and so forth and includes large scale patterns such as adaptive radiation.

absolute (= chronometric) dating) adaptation

Achievement criteria and explanatory notes

adaptive radiation

Achievement criteria for achieved, merit, and excellence

allele frequency allopatric

analogous structures

c

A

Demonstrate understanding of evolutionary processes leading to speciation: Use biological ideas and/or scientific evidence to describe evolutionary processes leading to speciation.

c

M

Demonstrate in-depth understanding of evolutionary processes leading to speciation: Use biological ideas and/or scientific evidence to explain how or why evolutionary processes leading to speciation.

c

E

Demonstrate comprehensive understanding of evolutionary processes leading to speciation: Link biological ideas and/or scientific evidence about evolutionary processes leading to speciation. This may involve justifying, relating, evaluating, comparing, contrasting, or analysing the evolutionary processes leading to speciation.

biogeography

chromosome mutation coevolution

common ancestor

comparative anatomy convergent evolution directional selection disruptive selection divergent evolution fitness

fossil record gene flow

Explanatory notes: Evolutionary processes

gene pool

Evolutionary processes involve the following biological ideas

c

1

The four fundamental processes in evolution are mutation, gene flow, natural selection, and genetic drift.

c

2

Allopatric speciation occurs in geographically separated populations. Sympatric speciation occurs in populations within the same region (sympatric populations).

c

3

Reproductive isolating mechanisms (RIMs) contributing to speciation may be temporal, ecological, behavioural, structural, and/or genetic. Geographical isolation is often a necessary precursor to reproductive isolation.

c

4

The fossil record and molecular evidence provide evidence for macroevolution:

homologous structure molecular clock mutation

natural selection

phyletic gradualism polyploidy

punctuated equilibrium

i

Large scale patterns of evolution include divergence (divergent evolution), adaptive radiation, coevolution, and convergence (convergent evolution).

ii

Models for the rates of evolutionary change include punctuated equilibrium and gradualism. We see evidence for both of these models in the fossil record.

relative dating

reproductive isolating mechanism

Explanatory notes: Evidence for evolution

Scientific evidence for evolution comes from many disciplines

speciation

5

species

stabilising selection

75  -  89

93  -  95 98 - 104

96 - 97 101 103 104

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genetic drift

Activity number

108 - 112 114 - 119 113

Activity number

Scientific evidence for evolution, including examples for New Zealand's flora and fauna, could be selected from:

c

i

Fossil evidence (including transitional fossils) and biogeography.

123- 132

c

ii

Comparative anatomy: homologous structures as evidence for shared ancestry and analogous structures as evidence for convergence.

133 - 134

vestigial structure

c

iii

Molecular biology (DNA and protein sequence analysis including immunology).

135 - 137

vicariance

c

iv

Developmental evidence (master genes and the control of development).

138 -139

sympatric transitional fossil


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Mutation, genetic drift, natural selection, and gene flow

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Activities 75 - 92

By the end of this section you should be able to:

Jeff Podos

c

Describe sources of variation in populations including sexual reproduction and mutation.

c

Use examples to show how mutation is the source of all new alleles.

c

Explain the importance of variation in populations as the raw material for natural selection.

c

Describe how natural selection sorts variation and establishes adaptive genotypes.

c

Using examples, explain how differences in selection pressures can result in stabilising, directional, and disruptive selection.

c

Describe the effect of genetic drift and gene flow on the genetic diversity of both small and large populations.

c

Explain why genetic drift is more significant in small populations or those with an unrepresentative sample of alleles (e.g. as a result of the founder or bottleneck effects).

Jeff Podos

Speciation and patterns of evolution Activities 93-122

By the end of this section you should be able to:

c

Explain what is meant by a biological species and describe the limitations of its definition.

c

Explain ring species and their significance to our understanding of speciation.

c

Explain the role of geographic isolation as a first step in the reproductive isolation of populations. Identify causes of geographic isolation and recognise that these can occur on different scales.

c

Describe mechanisms of reproductive isolation, distinguishing between prezygotic and postzygotic isolating mechanisms and their significance.

c

Use examples to explain allopatric (=different place) speciation in terms of migration, geographical or ecological isolation, and adaptation leading to reproductive isolation of gene pools.

c

Explain sympatric (=same place) speciation and discuss the role of polyploidy in instant speciation events in sympatric populations.

c

Describe stages in species formation, including how gene flow reduces as populations become increasingly isolated.

c

Describe how New Zealand's geological history has influenced speciation events in New Zealand's flora and fauna.

c

Distinguish different patterns of evolution to include divergence, convergence, coevolution, and adaptive radiation.

c

Explain adaptive radiation in which there is rapid diversification of species to fill vacant niches.

c

Explain convergent evolution in which unrelated species with similar niches converge in their structure or behaviour. Explain how analogous structures arise as a result of convergence.

c

Explain how two or more species with close ecological relationships may coevolve.

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c Distinguish between the punctuated equilibrium and phyletic gradualism (gradualism) models for the

pace of evolutionary change (rate of speciation). Describe the evidence for each model.

c Use New Zealand examples to illustrate different patterns of evolution.

Evidence for evolution Activities 123-142

By the end of this section you should be able to:

c

Using examples, explain how the fossil record provides evidence for evolution.

c

Explain how biogeography can help explain the origin and distribution of species.

c

Explain the molecular evidence (DNA and proteins) for the common ancestry of living organisms.

c

Explain how comparative anatomy, including homologous structures, analogous structures, and vestigial structures, help us understand evolutionary patterns and processes.

c

Explain how evolutionary developmental biology (evo-devo) now provides some of the strongest evidence for the diversification of species and the evolution of novel forms.

Jo Naylor cc 2.0


103

75 The Role of Variation in Populations own unique combination of alleles (genotype). An individual's genotype largely determines its phenotype (appearance). Those individuals with phenotypes well suited to the current environment have a greater chance of surviving and reproducing to pass on their genes to the next generation, i.e. they will have higher fitness. Individuals with less favourable phenotypes are less likely to survive and reproduce and their genes will have a lower representation in the next generation.

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Key Idea: Variation refers to the diversity of phenotypes within a population. Variation is important in evolution because it is the raw material for selecting favourable phenotypes. Populations are groups of individuals belonging to the same species that live in the same region at the same time. They are not necessarily isolated but may make contact with other populations of the same species (as in human populations). Each individual in a population is a carrier of its

Mutations

• Gene (point) mutations • Chromosome rearrangements

Sexual reproduction • • • •

Independent assortment Crossing over Recombination Mate selection

Provides the source of all new genetic information (all new alleles).

Rearrangement and shuffling of the genetic material into new combinations.

Selection pressures

Favourable phenotypes

• • • •

Phenotypes well-suited to the prevailing environment have better survival and greater reproductive success (i.e. higher fitness). They produce many offspring with the favourable traits.

Competition Predation Climatic factors Disease and parasitism

Favour some phenotypes more than others

The phenotype is the product of the many complex interactions between the genotype, the environment, and the chemical tags and markers that regulate the expression of the genes (epigenetic factors).

Genotype

Determines the genetic potential of an individual.

Environmental factors influence the expression of the genotype in producing the phenotype.

Environmental factors

Selection pressures on the phenotype will affect an individual's fitness. Selection pressures are those factors in the environment that determine whether an organism will be more or less successful at surviving and reproducing.

Phenotype

Each individual in the population is a 'TEST CASE' for its combination of alleles.

• Diet/nutrients • pH • Temperature • Wind exposure • Sunlight

Unfavourable phenotypes

Phenotypes poorly suited to prevailing environment have lower fitness and produce few offspring with the unfavourable traits.

1. (a) What is variation?

(b) Identify the sources of variation in sexually reproducing organisms:

2. What is the importance of variation to evolutionary change?

3. (a) What is meant by fitness and why is it important?

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(b) Define the term selection pressure and explain how it relates to fitness:

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76 Mutations (provide an advantage) may be passed on and become established within the population. Some mutations are silent, they have no impact under the current environmental conditions so remain in the population under no selection pressure. However a change in the environment can result in a silent mutation having a harmful or beneficial effect. Remember that a harmful mutation in one environment may be beneficial in another, so the effect of a mutation depends upon the selection pressures acting on the population.

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Key Idea: Mutations are changes to an organism's DNA. Beneficial mutations may spread within a population but harmful mutations are not usually retained. A mutation is a permanent change to the DNA sequence of an organism. Mutations allow for new genetic material to arise and be tested within the current environmental conditions. Most mutations are harmful because they reduce fitness. They remain at low levels within a population or they are eliminated altogether. Heritable mutations that are beneficial

Some mutations are retained, others are eliminated

If the mutation is harmful (reduces fitness) in the current environment it is selected against and is usually eliminated from the population.

Original amino acid sequence

Individual with the mutated protein

Mutated amino acid sequence

This mutation results in a different amino acid being added to the peptide chain. It changes the protein made.

A mutation occurs. Mutations may arise through errors in DNA replication or from environmental factors (e.g. UV radiation).

If the mutation is beneficial (increases fitness) and it is heritable (occurs in the gametes) it is selected for and retained in the population. It may become more common over several generations.

A silent mutation codes for the same amino acid even though there is a change in the DNA sequence. Heritable silent mutations may be carried through the population but only subject to selection pressure when environmental conditions change (i.e. they become advantageous or harmful).

1. What is a mutation?

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2. Why are some mutations retained within a population and others eliminated?

3. (a) What is a silent mutation?

(b) What is the potential advantage of a silent mutation being retained within a population?

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77 Beneficial Mutations are heritable, they can spread through the population. Some beneficial mutations are not very common in the human population. This is because the mutations have only been in existence for a relatively short time, so the mutations have not yet had time to become widespread.

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Key Idea: Beneficial mutations increase the fitness of the organisms that possess them, but they are relatively rare. A beneficial mutation is one that provides a selective advantage by increasing an individual's fitness. Beneficial mutations are rare relative to harmful mutations, but if they

it:Utente:Cits

Apolipoprotein A1-Milano mutation

Lactose tolerance mutation

Lactose free milk allows lactose intolerant adults to consume milk without experiencing unpleasant side effects

The village of Limone, Italy

ffMutation: Apolipoprotein A1-Milano (a mutation to the apolipoprotein A1 protein).

ffEffect: Helps remove cholesterol from the blood by transporting it

to the liver. The mutation causes a change to one amino acid and increases the protein's effectiveness at transporting cholesterol by ten times.

ffBenefit: Reduces incidence of heart disease by reducing plaque build up in the arteries (atherosclerosis).

ffOrigin: The mutation can be traced back to Limone, Italy, in 1644.

ffMutation: Lactose tolerance/lactose persistence. ffEffect: Continued production of lactase enzyme in adults allows the milk sugar lactose (found in dairy products) to be digested.

ffBenefit: Adults can digest lactose and gain the nutritional

benefits from consuming dairy products. The ability to digest lactose is lost as the young mammal is weaned and lactase production declines.

ffOrigin: Lactose tolerance first evolved in cattle or camel-raising populations in Northern Europe, East Africa, and the Middle East around 10,000 years ago.

Adapted from Leonardi, M., et.al J. Int. Dairy J. 22, 88–97 (2012).

Until 1932, the only way to reach the town was over steep mountains or across the lake by boat. Limone

Italy

Lake Garda

10%

Verona

90%

The ability to digest lactose remains highest in populations with a long history of consuming natural milk products. For example, 95% of people of Northern European descent are lactose tolerant. In contrast only 5-10% of people from East Asia can digest lactose. Adults without lactose tolerance have adverse reactions to dairy products including abdominal cramps, diarrhoea, and vomiting.

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Brescia

1. Explain why many beneficial mutations have not spread through the entire human population?

2. (a) Why would the ability to digest lactose in adults have first developed first in cattle-raising populations?

(b) What is the advantage of being able to digest lactose as an adult?

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78 Sickle Cell Mutation carriers of the sickle cell trait, but do not have the disease. Carriers (heterozygotes) usually only display symptoms when subjected to low oxygen concentrations. Under these conditions, the red blood cells take on a sickle shape. People with two copies of the Hbs mutation suffer from sickle cell disease. The disease causes many complications and results in a shortened life expectancy.

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Key Idea: A point mutation to the HBB gene causes the production of an abnormal haemoglobin molecule. Two copies of the mutation must be inherited for a person to have sickle cell disease. Sickle cell disease is an inherited blood disorder caused by a gene mutation (Hbs), which produces a faulty β-chain haemoglobin protein. People with one copy of the gene are Normal red blood cells

Each red blood cell (RBC) contains about 270 million haemoglobin molecules. In their normal state, the red blood cells have a flattened disc shape which allows them to squeeze through capillaries to offload their oxygen to tissues.

Normal haemoglobin produces normal red blood cells

Mutant haemoglobin produces sickle-shaped red blood cells

The mutated form of haemoglobin has reduced solubility and precipitates when deprived of oxygen. This deforms the red blood cells giving them a rigid sickle shape, which prevents their movement through capillaries.

A functional haemoglobin molecule is made up of two α-chains and two β-chains.

Sickle cell disease

The HBB Gene The gene coding for the β-chain of haemoglobin is on chromosome 11.

HBB gene

p

Sickle cells

β-chain haemoglobin

First base

Normal base: T Substituted base: A

People with two copies of the Hbs mutation are homozygous and have sickle cell disease. They have a reduced life expectancy and suffer from numerous health issues. Sickled cells are broken down, resulting in low haemoglobin levels and reduced oxygen transport, so sufferers are tired and short of breath. Sickled cells can also become stuck in blood vessels and can block oxygen transport to organs and tissues.

DNA

q

Code corresponding to the 1st amino acid

Sickle cell trait

This sequence is the beginning of the DNA template strand for a normal β-chain of haemoglobin (excluding start sequence TAC). The sickle cell mutation involves the substitution of one base for another in the HBB gene, causing one amino acid to be altered. This new amino acid is hydrophobic rather than hydrophilic, which makes the Hb collapse in on itself when deprived of oxygen.

People with one copy of the Hbs mutation are heterozgous for the trait. The Hbs mutation is codominant (both alleles are equally expressed) so both normal and abnormal haemoglobin is produced. People with sickle cell trait usually do not suffer any complications.

1. What effect does the Hbs mutation have on haemoglobin?

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2. (a) Describe the effect of inheriting two copies of the Hbs mutation:

(b) Describe the effect of inheriting a single copy of the Hbs mutation:

(c) Why is it possible for a carrier to have normal and abnormal haemoglobin?

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79 Heterozygous Advantage below, susceptibility to malaria is high in the homozygous dominant condition, but lower in the heterozygous condition. Consequently, the heterozygote has a higher fitness in malaria-prone regions. Heterozygous advantage can result in the stable coexistence of different phenotypes in a population (a state called balanced polymorphism) and can account for the persistence of detrimental alleles. The maintenance of the sickle cell mutation in malaria-prone regions is one of the few well documented examples in which the evidence for heterozygous advantage is conclusive.

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Key Idea: Heterozygous advantage is a phenomenon in which the heterozygote has a greater fitness than either of the homozygotes in certain selective environments. Natural selection operates on phenotypes (and therefore their genotypes) in the prevailing environment. For some phenotypic conditions controlled by a single gene with two alleles, a heterozygote (an individual with two different alleles for a gene) may have a higher fitness than either of the homozygous conditions. This situation is called heterozygous advantage. In the case of the sickle cell allele outlined

The sickle cell allele (HbS)

Sickle cell disease is caused by a mutation in a gene encoding haemoglobin. Genetic analyses show that the mutation arose spontaneously in different regions. The mutant allele (HbS) produces a form of haemoglobin that differs from the functional form by just one amino acid in the b-chain. This small change causes 'sickling' of the red blood cells. The sickling causes the red blood cells to clump together, blocking blood vessels, and causing numerous circulatory and organ problems. Destruction of the red blood cells also leads to anaemia.

Areas affected by falciparum malaria

ffIn heterozygotes (HbSHb), there is a mixture of both

normal and sickle cells and they are said to carry the sickle cell trait. They are generally unaffected by the disease except in low oxygen environments.

ffPeople with two HbS genes (HbSHbS) suffer severe illness and often die prematurely. HbS is therefore considered to be a lethal allele.

Heterozygous advantage in malarial regions

Falciparum malaria is widely distributed throughout central Africa, the Mediterranean, Middle East, and tropical and semi-tropical Asia (Fig. 1). It is transmitted by the Anopheles mosquito, which spreads the protozoan Plasmodium falciparum from person to person as it feeds on blood. Symptoms appear 1-2 weeks after being bitten, and include headache, shaking, chills, and fever. Falciparum malaria is more severe than other forms of malaria, with high fever, convulsions, and coma. Death can occur within days of the first symptoms appearing.

Four species of Plasmodium cause malaria but the variety caused by P. Â falciparum is the most severe.

Fig. 1: Incidence of falciparum malaria

1% - 5%

5% - 10%

HbS

This is a special case of balanced polymorphism, called a balanced lethal system because neither of the homozygotes produces a phenotype that survives, but the heterozygote is viable.

10% - 20%

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allele offers considerable The paradox: The protection against malaria. Sickle cells have low potassium levels, which causes Plasmodium parasites inside these cells to die. Those with a normal phenotype are very susceptible to malaria, but heterozygotes (HbSHb) are much less so. This situation, called heterozygous advantage, has resulted in the HbS allele being present in moderately high frequencies in parts of Africa and Asia despite its harmful effects (Fig. 2).

Anopheles mosquito, the insect vector responsible for spreading Plasmodium.

HbHb HbsHb All red blood cells normal Normal and sickle cells Malaria resistance Susceptible to malaria

HbsHbs All cells are sickled Sickle cell disease

Fig. 2: Frequency of the sickle cell allele

1. Why do carriers of the Hbs allele have an advantage in malaria-prone regions?

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2. With respect to the sickle cell allele, explain how heterozygous advantage can lead to balanced polymorphism:

3. (a) Describe the distribution of malaria throughout the world (Fig. 1):

(b) What do you notice about its distribution compared to the frequency of the Hbs allele (Fig. 2)? Figure 3 shows the general distributions of various haemoglobin disorders that all produce abnormal red blood cells to some degree.

HbE is a mutation that appears to have arisen about 5000 years ago and is caused by a change in the 26th amino acid in the b-chain from glutamic acid to lysine. The HbS mutation changes the 6th amino acid from glutamic acid to valine.

Both HbE and HbC heterozygotes show virtually no (and certainly much less than HbS) symptoms of anaemia (reduced haemoglobin levels). Thalassaemia is a disease in which gene mutations result in the lowered production of haemoglobin and red blood cells. The effects can be very severe.

HbE

HbS

HbC

Thalassaemia

Fig. 3: Distribution : of abnormal blood conditions

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HbC is a mutation that occurs in the same position as HbS, but the mutation produces the amino acid lysine instead of valine.

4. Account for the distribution of red blood cell abnormalities, explaining why these abnormalities persist:

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80 Gene Duplication and Evolution Key Idea: Gene duplication can provide new copies of genes for natural selection to act on. The duplication of whole segments of DNA containing genes is called gene duplication. Gene duplication is important in evolution because it produces more genetic variation for selection pressures to act upon. Like mutations, not all gene duplications become fixed in a population and only

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those providing an advantage become established. Once established the gene may evolve to have a completely different role from the original gene. Gene duplication is very common and has occurred in virtually every species and often more than once. Many crop plants (e.g. kiwifruit) have duplicated not just one gene, but their entire genome. In humans, 38% of our genes have been duplicated.

Before duplication

Gene containing region

After duplication

Gene duplication

ffSometimes having two genes with the same role

Duplicated region

(functionality) can be an advantage and both genes retain their original function. For example, when there is a high demand for a particular protein.

ffUnless two copies of the same gene provide an

advantage, one of the duplicated genes may develop a new function while the other copy continues on with its original function.

ffIn the case of genes that produce proteins with

In Drosophila melanogaster, the fruit fly, 41% of the genes are duplicated

a tendency or ability to perform two functions, there may be adaptive conflict, in which its ability to perform one function compromises its ability to perform another. Gene duplication solves this problem by allowing natural selection to act on the genes so that they follow different evolutionary paths.

Haemoglobin: the role of gene duplication and mutation

ffThe globin proteins are a family of iron-containing

Ancestral globin gene

800

oxygen binding proteins. The evolution of human haemoglobin genes has involved both duplication and mutation.

400

α

β

α

200

ζ

followed by an accumulation of mutations to both copies (2) produce the a- and b-haemoglobin genes. This was a significant event because it allowed for the formation of the large mutliunit haemoglobin protein from the different subunits (a- and b-globins).

β

α

α

ffThe third event was the transposition (change in

γ

position) of these genes to different chromosomes (3). Further duplications and mutations produced the wide family of globin proteins found in humans (4).

β

0

ζ

ψζ ψα2 ψα1 α2 α1 ψθ

α-globin gene family is found on chromosome 16

1. What is meant by gene duplication:

ε

ψβ

δβ β

β-globin gene family is found on chromosome 11

ffMyoglobin, another globin gene, was also formed by duplication, mutation, and transposition. Myoglobin has an oxygen storage role in muscle and the gene is found on chromosome 22.

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Millions of years ago

ffDuplication of an ancestral globin gene (1),

2. What evidence do we have that gene duplication is a common occurrence?

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110 Gene duplication in Antarctic fish Fish living in the near freezing waters of the Antarctic must have a way of ensuring their blood remains ice free. In many species, this is done by producing proteins with antifreeze properties. There are four major antifreeze proteins used by fish (called AFP types I - IV). The gene for the protein AFP III, found in Antarctic eelpout, is very similar to the gene that produces sialic acid synthase (SAS) (also found in humans).

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Gene duplication in colobine monkeys Gene duplication in colobine monkeys has enabled the production of enzymes that optimally perform similar functions in different body environments. The primary food source of colobines, unlike most other primates, is leaves. The leaves are fermented in the gut by bacteria, which are then digested with the assistance of an enzyme produced by RNase genes. In colobines there are two forms of the RNase genes, RNase1 and RNase1B, while in other primates there is only RNase1.

ART G CC 2.0

Molecular studies have found that a slight modification in the SAS gene causes the production and secretion of AFP III. More importantly, the SAS gene also shows ice binding capabilities. It appears that a duplication of the SAS gene produced a new gene that was selected for its ice binding capabilities and diverged to become the AFP III gene in Antarctic eelpout.

The optimal pH for the enzyme RNase1 is 7.4. For RNase1B, the optimal pH is 6.3. In colobine monkeys, the pH of the digestive system is 6-7, but in other primates it is 7.4-8. RNase1B is six times more efficient at degrading RNA in the gut of colobines than RNase1. RNase1 is also expressed in cells outside the digestive system where it degrades double stranded RNA and may assist in defense against viral infection. RNase1B is 300 times less efficient at this function.

AFP III protein

SAS protein

AFP III protein and SAS protein have similar structures and can be modified to have similar functions. This provides evidence for the likelihood of diversification of function after gene duplication.

3. (a) Why aren't all gene duplications retained in a population?

(b) Explain what opportunity could be provided by a gene duplication event in an new environment:

4. When would it be an advantage to have two genes performing the same function?

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5. Outline how a number of different globin proteins have been produced from a single ancestral globin gene:

6. What evidence do we have that the AFPIII protein found in Antarctic eelpout may be have evolved through a duplication of the SAS gene?

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81 An Introduction to Evolutionary Processes that provides the raw material for evolution. Four processes act to cause genetic change in populations. Mutation creates new alleles and alleles may also enter or leave a population through gene flow (migration). Natural selection sorts variation and establishes adaptive phenotypes and is a major agent of evolution. Genetic drift alters alleles frequencies randomly and its effects are due to chance events. Increasingly, genetic drift is being recognised as an important agent of change, especially in small populations.

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Key Idea: Mutations, gene flow, genetic drift, and natural selection all contribute to changes in the genetic makeup (frequency of different alleles) of a population. A population can be regarded as a collection of all its alleles (the gene pool). Changes in the frequency of these alleles in the population over time is what we call evolution. If all the organisms in a population were identical in genotype and phenotype, mutation would be the only factor affecting allele frequencies. Of course, organisms show variation and it is this

Genetic variation

As we have seen in earlier activities, genetic variation arises through mutations and the recombination of alleles through sexual reproduction.

Genetic variation refers to the number of different types of alleles in a population. Genetic variation produces phenotypic variation (e.g. colour of ladybirds). It is this phenotypic variation that is the raw material for natural selection.

For example, a mutation produces a ladybird with a new spotted phenotype (below).

This ladybird population has five different phenotypes (black, dark blue, medium blue, light blue, and pale).

Immigration

Emigration

XX

Natural selection

Genetic drift

Migration (gene flow)

Natural selection is the process where selection pressures act on populations to maintain favourable phenotypes and unfavourable phenotypes are selected against. Over time, favourable phenotypes become more common in the population because the individuals reproduce.

Genetic drift is the change in a population's allele frequency due to random events. Genetic drift has a more pronounced effect in small populations.

Migration is the movement of individuals into and out of a population. Through immigration or emigration, alleles can enter or leave the population. Gene flow tends to decrease the genetic differences between populations because alleles are being exchanged.

For example, black ladybirds are more easily seen by birds and are eaten more often than the other phenotypes. The lighter phenotypes become more common in the next generation.

For example, falling rocks kill a number of ladybirds, but more of the dark blue ladybirds, which have congregated in one area, are crushed than any other phenotype. The proportion of dark blue ladybirds remaining in the population is drastically reduced, and their representation in the next generation is also reduced.

In the example above several black lady birds have left and some very pale lady birds have arrived changing the proportion of remaining phenotypes in the population.

(a) Gene flow:

(b) Genetic drift:

(c) Natural selection:

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1. Define the following terms:

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2. One of the important theoretical concepts in population genetics is that of genetic equilibrium, which state that "for a large, randomly mating population, allele frequencies do not change from generation to generation". If allele frequencies in a population are to remain unchanged, all of the following criteria must be met: the population must be large, there must be no mutation or gene flow, mating must be random, and there must be no natural selection. Evolution is a consequence of few if any of these conditions ever being met in natural populations. For each of the five factors (a-e) below, describe how and why each would affect the allele frequency in a gene pool. Use the diagrams to help you. (a) Population size:

Factors favouring gene pool stability (no evolution)

Factors favouring gene pool change (evolution)

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(b) Mate selection:

Aa

Aa aa AA

Aa

Aa

aa

Aa

Aa

Aa

AA

Aa

Aa aa

Aa

AA

AA

Aa

Aa

AA

AA

Aa Aa

Aa

AA

Aa

Aa

Aa

aa

Aa

aa

Aa Aa

Aa

AA

aa

(c) Gene flow:

AA

Aa

aa

AA

Aa

Assortative mating

Barrier to gene flow

Aa

AA

Aa

aa

aa

AA

aa

AA

Aa

Aa

Aa

AA

AA

Aa

aa

AA

Aa

AA

Aa

aa

Aa

AA

Aa

Aa

Aa

aa

(b) Decrease genetic variation in populations:

aa

Aa

aa

Aa

Aa

a'a

AA

Aa

AA

Aa

aa aa

aa

aa

AA

Aa Aa

Aa

AA

Aa

AA

AA

Aa

Mutations

Aa

AA

Aa

New recessive allele

Aa

aa

Aa

AA

AA

Aa

Aa AA aa AA AA Aa aa Aa aa AA AA Aa aa Aa Aa

AA

3. Identify a factor that tends to:

AA Aa

aa

AA

Gene flow

Aa

No mutation

aa

Aa

Aa

Aa

Emigration

AA

Aa

Aa

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aa

Aa aa

Aa

Aa

(e) Natural selection:

Aa

Aa AA

aa AA

AA

Immigration

Aa AA

aa Aa

No gene flow

Aa

aa

Aa

Aa

Aa

Aa

aa AA AA

aa

Aa AA

(d) Mutation:

(a) Increase genetic variation in populations:

aa

Aa

AA

Aa AA

aa

Aa

AA

Aa

aa

Aa

Random mating

Aa

AA

aa

AA

aa

Aa AA

Aa

Small population

AA

aa

Aa AA

aa

aa Aa

Large population

aa

Aa

Aa

Aa

Aa

aa

Aa Aa

aa

aa

AA

Aa

AA

No natural selection

Aa

aa

AA

Aa

Aa

AA

Aa Aa

Aa

AA

Aa

Aa

aa

Aa

AA

Aa

AA

Aa

Aa

aa

Aa AA

aa

Aa

AA

Natural selection

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82 Genetic Drift Affects Gene Pools generally the result of the founder effect or a genetic bottleneck. In the founder effect, a small proportion of the population becomes isolated, e.g. through a colonisation event. Genetic bottlenecks occur when populations experience catastrophic losses so that only a small proportion of the population survives. Both these mechanisms are well documented in natural populations. In these small populations, genetic drift is an important agent of genetic change.

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Key Idea: Genetic drift is the change in allele frequencies in a population as a result of random events. It can be an important agent of evolution in small populations. Genetic drift is the change in allele frequencies in a population due to random (chance) events. It may result in the loss (or fixation) of any allele, including beneficial ones. Genetic drift is effectively sampling error so its effects are greater when the population is small. In natural systems, small populations are

How does genetic drift reduce variation in populations?

The change in allele frequencies within a population through genetic drift is often illustrated using the random sampling of marbles from a jar. The diagram below represents a population of 20 individuals. The different alleles are represented by blue and grey marbles. The starting population contains an equal number of blue and grey marbles. Random mating is represented by selecting 10 marbles at random. Twenty marbles representing the new allele proportions are placed into a new jar to represent the second generation, and the process is repeated for subsequent generations. Starting population 50 : 50

Second generation 60 : 40

Third generation 70: 30

Draw 6

Draw 7

Draw 9

4

3

1

80

60

40

Population 2000

20

The graph on the right shows the effect of genetic drift on populations of various sizes. Fluctuations are minimal for a large population (2000) but more pronounced in smaller populations (200 and 20), which may lose alleles.

1. (a) Describe the effects of genetic drift:

Allele lost

Population 200 Population 20

0

0

20

40

60 80 Generations

100

120

140

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In small populations, genetic drift can be a major agent of rapid change because the loss of any one individual represents a greater proportion of the total population.

100

Allele frequency (%)

In the example above, the grey marbles are becoming less frequent within the population and the amount of genetic variation within the population is reducing. Unless the proportion of grey marbles increases, it will eventually be lost from the population altogether and the allele for the blue marble becomes fixed (the only variant). If environmental conditions change so that the blue allele becomes detrimental, the population may become extinct (the potentially adaptive grey allele has been lost).

Fourth generation 90: 10

(b) Explain why the effects of genetic drift are more significant in small populations?

2. (a) Genetic drift in a small population would increase / decrease the number of heterozygotes (delete one):

(b) How could this affect a population's long term viability?

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83 Adaptations and Fitness Key Idea: An adaptation is any heritable trait that equips an organism for its functional role in the environment (its niche). An adaptation is any heritable characteristic (trait) that equips an organism for its niche, enhancing its exploitation of the environment and contributing to its survival and successful reproduction (fitness). The adaptations that evolve in species are the result of the selection pressures to which they are

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exposed throughout the course of their evolution. Traits that are not helpful to survival and reproduction will not be favoured and will be lost. Adaptations may be structural (morphological), physiological, or behavioural. The speciation of two New Zealand parrots, the kea and kaka, from a common ancestor illustrates the importance of adaptation to a particular habitat and niche.

Kea are inquisitive and highly intelligent. They have been filmed using tools and are adept at problem solving.

Name: Kea (Nestor notabilis) Habitat

ffAlpine (mountain) regions in the South Island.

Structural adaptations

Petit Deuxmont cc 2.0

ffDense plumage provides insulation against the cold. ffRobust body for surviving in the cold. ffLarge, narrow curved beak and claws for manipulating foods, and to move and investigate objects.

Physiological adaptations

ffExcellent vision and can identify and process a wide

variety of foods, including plants, insect larvae, birds, carrion, mammals (including sheep), and human scraps.

Behavioural adaptations

ffHighly social, intelligent, and curious (characteristics

useful in investigating and exploiting new food sources).

Name: Kaka (Nestor meridionalis)

o

sin

Ro

cc

0 2.

Habitat

ffForest-dwelling, found throughout New Zealand in

localised forest strongholds. More arboreal than kea.

Structural adaptations

ffA brush tongue to remove nectar from flowers. ffStrong, broad beak used for tree climbing, digging out

Proto-kaka The kea and kaka diverged from a common proto-kaka ancestor about 3 mya. The rise of the Southern Alps provided a new alpine habitat that the ancestral kea occupied. The kaka ancestor remained in forested areas.

insects, and opening kauri cones to obtain the seeds.

ffStrong, agile feet are used to hold food and to cling onto branches while feeding.

ffStrong fliers, can weave between trees.

Physiological adaptations

ffExcellent vision and can identify and process a wide

range of foods including seeds, fruits and berries, flowers, buds, nectar, honeydew, and invertebrates. ffProduce a second clutch in a season if food is abundant.

Kaka uses its claws and beak to manipulate food and climb through the branches.

Matt Binns cc 2.0

Behavioural adaptations

ffSeasonal specialists, exploiting different food sources as they become available.

ffWill congregate at abundant food sources or forage alone.

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1. What is adaptation?

2. What event resulted in the kea and the kaka diverging and what was its effect?

3. Describe how the adaptations of kea and kaka help them exploit the foods available in two very different environments:

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84 Natural Selection Affects Gene Pools become relatively more numerous and than unfavourable phenotypes. Over time, natural selection may lead to a permanent change in the genetic makeup of a population. Natural selection is always linked to phenotypic suitability in the prevailing environment so it is a dynamic process. It may favour existing phenotypes or shift the phenotypic median, as is shown in the diagrams below. The top row of diagrams below represents the population phenotypic spread before selection, and the bottom row the spread afterwards.

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Key Idea: Natural selection is responsible for the differential survival of some phenotypes (and genotypes) over others. It is an important cause of genetic change in populations. Natural selection operates on the phenotypes of individuals, produced by their particular combinations of alleles. It results in the differential survival of some genotypes over others. As a result, organisms with phenotypes most suited to the prevailing environment are more likely to survive and breed than those with less suited phenotypes. Favourable phenotypes will Stabilising selection

Directional selection

Eliminated

Increasing birth weight

Frequency

Eliminated

Retained

Frequency

Frequency

Retained

Eliminated

Disruptive selection

Eliminated

Retained

Increasing pigmentation

Retained

Increasing beak size

Frequency

Frequency

Frequency

Two peaks

Increasing birth weight

Extreme variations are selected against and the middle range (most common) phenotypes are retained in greater numbers. Stabilising selection results in decreased variation for the phenotypic character involved. This type of selection operates most of the time in most populations and acts to prevent divergence from the adaptive phenotype, e.g. birth weight of human infants. Stabilising selection predominates when environments are stable.

Increasing beak size

Increasing pigmentation

The adaptive phenotype is shifted in one direction and one phenotype is favoured over others. Directional selection was observed in peppered moths in England during the Industrial Revolution when soot-covered trees were common. In England’s current environment, the selection pressures on the moths are more balanced, although lighter morphs predominate. Selection will be directional when there is a trend in environmental conditions, e.g. warm to cold.

Disruptive selection favours two phenotypic extremes at the expense of intermediate forms. During a prolonged drought on Santa Cruz Island in the Galápagos, it resulted in a population of ground finches that was bimodal for beak size. Competition for the usual medium-sized seed sources was so intense that selection favoured birds able to exploit either small or large seeds. Disruptive selection may occur when environments or resources are fluctuating or distinctly divergent.

(a) Stabilising selection:

(b) Directional selection:

(c) Disruptive selection:

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1. Define the following, including a statement about the type of environment that favours each:

2. Explain why fluctuating (as opposed to stable) environments favour disruptive (diversifying) selection:

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85 Stabilising Selection for Human Birth Weight constrain birth weight to within narrow limits. This is a good example of stabilising selection. It is possible to document this effect by plotting birth weights for a large sample of the population. Carry out the steps below.

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Key Idea: Stabilising selection operates to keep human birth weight within relatively narrow constraints. Selection pressures operate on populations in such a way as to reduce mortality. For humans, selection pressures act to For this activity, you will need a sample of 100 birth weights. You can search birth records online or use the data provided in the appendix at the back of this book.

Group the weights into each of the 12 weight classes indicated on the graph template provided. Calculate the percentage in each weight class.

Step 3:

Graph these in the form of a histogram for the 12 weight classes (use the graphing grid provided right). Be sure to use the scale provided on the left vertical (y) axis.

Step 4:

Create a plot of percentage mortality of newborns in relation to their birth weight. Use the scale on the right y axis and data provided (below). Draw a line of best fit through the points. Weight (kg)

Mortality (%)

1.0

80

1.5

30

2.0

12

2.5

4

3.0

3

Mortality3.5 of newborn babies 2 related 4.0to birth weight 3

4.5 Weight (kg) 5.0

Mortality (%)

50

100

40

80

30

60

20

40

10

20

Percent mortality

Step 2:

The size of the baby and the diameter and shape of the birth canal are the two crucial factors in determining whether a normal delivery is possible.

Percentage of births sampled

Step 1:

7

15

1.0 80 1.5 30 2.0 12 2.5 4 Evidence indicates that the phenotypic norm 3.0 3 is shifting. Researchers estimate that cases 3.5 2 where the baby cannot fit down the birth canal 4.0 3 in the 1960s have increased from 30/1000 4.5 births today, indicating 7 to 36/1000 that there 5.0 15 is less selection against women with narrow

0

0.0

0.5

1.0

1.5

pelves and babies with larger heads. Source: Biology: The Unity & Diversity

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

0

Birth weight (kg)

of Life (4th ed), by Starr and Taggart

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1. Describe the shape of the histogram for birth weights:

2. What is the optimum birth weight in terms of the lowest newborn mortality? 3. Describe the relationship between newborn mortality and birth weight:

4. Describe the selection pressures that are operating to control the range of birth weight:

5. How might modern medical intervention during pregnancy and childbirth have altered these selection pressures?

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86 Directional Selection in Moths Revolution, selection favoured the proliferation of dark (melanic) forms over the pale (non-melanic) forms. Intensive coal burning during this time caused trees to become dark with soot, offering melanic forms greater camouflage against predatory birds. The shift in phenotype at this time is an example of directional selection.

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Key Idea: Selection pressures on the peppered moth during the Industrial Revolution shifted the common phenotype from the grey form to the melanic (dark) form. Genetically determined melanism is a common polymorphism in animals (meaning different forms exist in the population). In the peppered moth (Biston betularia) during the Industrial Olaf Leillinger

Melanic form Genotype: MM or Mm

The peppered moth, Biston betularia, has two forms: a grey mottled form, and a dark melanic Olaf Leillinger form. During the Industrial Revolution, the relative abundance of the two forms changed to favour the dark form. The change was thought to be the result of selective predation by birds. It was proposed that the grey form was more visible to birds in industrial areas where the trees were dark. As a result, birds preyed upon them more often, resulting in higher Grey form numbers of the dark form surviving. Genotype: mm

Frequency of melanic peppered moth related to reduced air pollution

100

150

Melanic Biston betularia

90

Frequency of melanic form of Biston betularia (%)

In the 1940s and 1950s, coal burning was still at intense levels around the industrial centres of Manchester and Liverpool. During this time, the melanic form of the moth was still very dominant. In the rural areas further south and west of these industrial centres, the occurrence of the grey form increased dramatically. With the decline of coal burning factories and the introduction of the Clean Air Act in cities, air quality improved between 1960 and 1980. Sulfur dioxide and smoke levels dropped to a fraction of their previous levels. This coincided with a sharp fall in the relative numbers of melanic moths (right).

Museum collections of the peppered moth over the last 150 years show a marked change in the frequency of the melanic form (above right). Moths collected in 1850, prior to the major onset of the Industrial Revolution in England, were mostly the grey form (above left). Fifty years later the frequency of the darker melanic forms had increased.

80

100

Winter sulfur dioxide

70 60 50

50

Summer smoke

40

0

1960

1965

1970

1975

1980

1985

Summer smoke or winter sulfur dioxide (Âľg m -3)

The gene controlling colour in the peppered moth, is located on a single locus. The allele for the melanic (dark) form (M) is dominant over the allele for the grey (light) form (m).

Year

1. The populations of peppered moth in England have undergone changes in the frequency of an obvious phenotypic character over the last 150 years. What is the phenotypic character?

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2. Describe how the selection pressure on the grey form has changed with change in environment over the last 150 years:

3. Describe the relationship between allele frequency and phenotype frequency:

4. The level of pollution dropped around Manchester and Liverpool between 1960 and 1985. How did the frequency of the darker melanic form change during this period?

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87 Directional Selection in Darwin's Finches more offspring, increasing the proportion of the genes corresponding to that phenotype in the next generation. Numerous studies on both vertebrate and invertebrate populations have shown that natural selection can cause phenotypic changes in a population relatively quickly.

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Seal Key Idea: The effect of natural selection on a population can be verified by making quantitative measurements of phenotypic traits. Natural selection acts on the phenotypes of a population. Individuals with phenotypes that increase their fitness produce The finches on the Galápagos island (Darwin's finches) are famous in that they are commonly used as examples of how evolution produces new species. In this activity you will analyse data from the measurement of beak depths of the medium ground finch (Geospiza fortis) on the island of Daphne Major near the centre of the Galápagos Islands. The measurements were taken in 1976 before a major drought hit the island and in 1978 after the drought (survivors and survivors' offspring).

Beak depth (mm)

No. 1976 birds

No. 1978 survivors

Beak depth of offspring (mm)

Number of birds

7.30-7.79

1

0

7.30-7.79

2 2

7.80-8.29

12

1

7.80-8.29

8.30-8.79

30

3

8.30-8.79

5

8.80-9.29

47

3

8.80-9.29

21

9.30-9.79

45

6

9.30-9.79

34

9.80-10.29

40

9

9.80-10.29

37

10.30-10.79

25

10

10.30-10.79

19

10.80-11.29

3

1

10-80-11.29

15

11.30+

0

0

11.30+

2

1. Use the data above to draw two separate sets of histograms:

(a) On the left hand grid draw side-by-side histograms for the number of 1976 birds per beak depth and the number of 1978 survivors per beak depth. (b) On the right hand grid draw a histogram of the beak depths of the offspring of the 1978 survivors.

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2. (a) Mark the approximate mean beak depth on the graphs of the 1976 beak depths and the 1978 offspring.

(b) How much has the average moved from 1976 to 1978?

(c) Is beak depth heritable? What does this mean for the process of natural selection in the finches?

3. The 1976 drought resulted in plants dying back and not producing seed. Based on the graphs, what can you say about competition between the birds for the remaining seeds, i.e. in what order were the seeds probably used up?

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88 Disruptive Selection in Darwin's Finches

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Key Idea: Disruptive selection in the finch Geospiza fortis produces a bimodal distribution for beak size. The GalĂĄpagos Islands, 970 km west of Ecuador, are home to the finch species Geospiza fortis. A study during a prolonged

drought on Santa Cruz Island showed how disruptive selection can change the distribution of genotypes in a population. During the drought, large and small seeds were more abundant than the preferred intermediate seed size.

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Beak size vs fitness in Geospiza fortis

1.0

The presence or absence of banded individuals was recorded at the end of the year when the birds were recaptured. Recaptured individuals had their beaks measured. The proportion of banded individuals in the population at the end of the year gave a measure of fitness. Absent individuals were presumed dead (fitness = 0).

Measurements of the beak length, width, and depth were combined into one single measure.

Fitness is a measure of the reproductive success of each genotype.

0.8 0.6

Higher fitness

0.4

Higher fitness

0.2 0

-2.0 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 Beak size (single measure)

Fitness related to beak size showed a bimodal distribution (left) typical of disruptive selection.

A.P. Hendry et. al 2009

Local fitness (2004-2006)

Beak sizes of G. fortis were measured over a three year period (2004-2006), at the start and end of each year. At the start of the year, individuals were captured, banded, and their beaks were measured.

2.0

2.5

Fitness showed a bimodal distribution (arrowed) being highest for smaller and larger beak sizes.

Beak size pairing in Geospiza fortis

S.K. Huber et al. 2007

0

-1.0

0

1.0

2.0

-2.0 3.0-2.0 -1.0

0

1.0

2.0

3.0

Female beak size (single measure) ale beak size (single measure)

1.0

0

Pairing under dry conditions

3.0

Large beak G. fortis

2.0 1.0

Small beak G. fortis

0

A 2007 study found that breeding pairs of birds had similar beak sizes. Male and females with small beaks -1.0 -1.0 tended to breed together, and males and females with large beaks tended to breed together. Mate selection -2.0 -2.0 maintained the biomodal distribution in the population 0 1.0 2.0 3.0 0 -2.0 -1.0 1.0 2.0 3.0-2.0 -1.0 during extremely wet conditions. If beak size wasn't a Female beak sizein (single factor matemeasure) selection, the beak size would even out. Female beak size (single measure)

1. (a) How did the drought affect seed size on Santa Cruz Island?

(b) How did the change in seed size during the drought create a selection pressure for changes in beak size?

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-1.0

2.0

4.0

S.K. Huber et al. 2007

1.0

3.0

Male beak size (single measure)

2.0

4.0

Pairing under dry conditions

S.K. Huber et al. 2007

3.0

S.K. Huber et al. 2007

Male beak size (single measure)

4.0

Male beak size (single measure)

Pairing under extremely wet conditions

Pairing under extremely wet conditions

2. How does beak size relate to fitness (differential reproductive success) in G. fortis?

3. (a) Is mate selection in G. fortis random / non-random? (delete one)

(b) Give reasons for your answer:

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89 Selection for Skin Colour in Humans was that skin cancer is not tied to evolutionary fitness because it affects post-reproductive individuals and cannot therefore provide a mechanism for selection. Physiological and epidemiological evidence has now shown that selection pressures on skin colour are finely balanced to produce a skin tone that regulates the effects of the sun's UV radiation on the nutrients vitamin D and folate, both of which are crucial to successful reproduction and therefore evolutionary fitness. The selection is stabilising within each latitudinal region.

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Key Idea: Skin colour is the result of a dynamic balance between two different selection pressures linked to fitness. Pigmented skin of varying tones is a feature of humans that evolved after early humans lost the majority of their body hair. However, the distribution of skin colour globally is not random; people native to equatorial regions have darker skin tones than people from higher latitudes. For many years, biologists postulated that this was because darker skins had evolved to protect against skin cancer. The problem with this explanation

Skin colour in humans: a product of natural selection

Alaska

80°

France

The Netherlands

Iraq

China

Japan

No data

80°

Insufficient UV most of year

40°

Insufficient UV one month

Sufficient UV all year

40°

Sufficient UV all year

40°

Insufficient UV one month

40°

Insufficient UV most of year

Photo: Lisa Grey

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Adapted from Jablonski & Chaplin, Sci. Am. Oct. 2002

Peru

Liberia

Burundi

Human skin colour is the result of two opposing selection pressures. Skin pigmentation has evolved to protect against destruction of folate from ultraviolet light, but the skin must also be light enough to receive the light required to synthesise vitamin D. Vitamin D synthesis is a process that begins in the skin and is inhibited by dark pigment. Folate is needed for healthy neural development in humans and a deficiency is associated with fatal neural tube defects. Vitamin D is required for the absorption of calcium from the diet and therefore normal skeletal development. WEB

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Botswana

Southern India

Malaysia

Women also have a high requirement for calcium during pregnancy and lactation. Populations that live in the tropics receive enough ultraviolet (UV) radiation to synthesise vitamin D all year long. Those that live in northern or southern latitudes do not. In temperate zones, people lack sufficient UV light to make vitamin D for one month of the year. Those nearer the poles lack enough UV light for vitamin D synthesis most of the year (above). Their lighter skins reflect their need to maximise UV absorption (the photos show skin colour in people from different latitudes). © 1988-2016 BIOZONE International ISBN: 978-1-927309-56-8 Photocopying Prohibited


121 1. (a) Describe the role of folate in human physiology:

(b) Describe the role of vitamin D in human physiology:

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2. (a) Early hypotheses to explain skin colour linked pigmentation level only to the degree of protection it gave from UV-induced skin cancer. Explain why this hypothesis was inadequate in accounting for how skin colour evolved:

(b) Explain how the new hypothesis for the evolution of skin colour overcomes these deficiencies:

3. Explain why, in any given geographical region, women tend to have lighter skins (by 3-4% on average) than men:

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4. The Inuit people of Alaska and northern Canada have a diet rich in vitamin D and their skin colour is darker than predicted on the basis of UV intensity at their latitude. Explain this observation:

5. (a) What health problems might be expected for people of African origin (right) now living in northern UK?

(b) How could these people avoid these problems in their new higher latitude environment?

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90

What You Know So Far: Processes in Gene Pools Mutations

HINT: What effect does mutation have on variation? Provide examples of mutations.

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you: Variation, selection, and fitness

HINT: What is variation and how does it arise? What is fitness and what is its significance?

HINT: Describe how natural selection acts upon phenotypic variation. Describe the three types of natural selection.

REVISE

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Natural selection

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91 NCEA Style Question: Mutation and Evolution

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1. HIV/AIDS has killed more than 25 million people globally and infected another 33 million since it was first recognised in 1981. In the mid 1990s, it was found that the HIV-1 virus entered T-cells of the immune system by docking with the receptor protein encoded by the CCR5 gene. Soon after this, it was discovered that the deletion of 32 bases in the gene (mutation CCR5D32) produces a premature stop codon in the mRNA, resulting in a non-functional receptor protein and resistance to HIV-1.

Western Europe has also been the site of many smallpox epidemics before its elimination in 1980. Hypotheses for the prevalence of the CCR5D32 mutation vary. A possible hypothesis is that CCR5D32 may have conveyed some immunity to smallpox or plague or both.

18

% population with CCR5Δ32 mutation

Geographical studies have found that the CCR5D32 mutation is found in light-skinned people of European descent in some areas of northern Europe where it is carried by up to 18% of the population. The mutation is virtually absent in Asian, Middle Eastern, and American Indian populations.

16 14 12 10 8 6 4 2 0

(a) Discuss the nature of the CCR5D32 mutation, including the significance of the premature stop codon to HIV resistance:

(b) Discuss the spread of the CCR5D32 mutation through the European population. Include past and future selection pressures. You may use more paper if required.

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92 KEY TERMS AND IDEAS: Processes in Gene Pools

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1. Test your vocabulary by matching each term to its definition, as identified by its preceding letter code.

adaptation

A The observable characteristics in an organism. B A heritable characteristic of a species that equips it for survival and reproductive success in its environment.

fitness

C The differences between individuals in a population as a result of genes and environment.

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gene pool

genetic drift mutation

natural selection phenotype variation

D The process by which favorable heritable traits become more common in successive generations. E The collective group of genes in a population.

F Random changes in allele frequency between generations as a result of the different contributions of individuals to the alleles in the gene pool of the next generation. G A measure of an individual's relative genetic contribution to the next generation as a result of its combination of traits.

H A change in the base sequence of DNA; the ultimate source of new alleles. I A change in the allele frequency of a population over time.

2. Fill in the missing gaps using the word list provided: environmental conditions, adaptive advantage, DNA, harmful, silent, alleles, eliminated.

Mutations are changes in an organism's

and they are the source new

population. Most mutations are

Inherited beneficial mutations provide an

that do not change the amino acid sequence are called

population but may not be subjected to selection pressures unless the

and so are

in a

from the population.

so are retained in the population. Mutations mutations. They are retained in the

change.

3. Compare and contrast the role of genetic drift and natural selection in changing the genetic makeup of a population:

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4. (a) Describe the features of stabilising selection:

(b) Using an example, explain what might cause selection to shift from stabilising to directional:

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93 The Biological Species Concept in reality. For example, some closely related species will interbreed to produce fertile hybrids, e.g. Canis species. The concept of a biological species is also more successfully applied to animals than to plants, which hybridise easily and can reproduce vegetatively. The concept is also problematic for extinct organisms and those that reproduce asexually.

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Key Idea: A biological species is a group of organisms that can successfully interbreed to produce fertile offspring. A biological species is defined as a group of individuals capable of interbreeding to produce fertile offspring and reproductively isolated from other such groups. Although simple by definition, species are more difficult to define

Distribution of Canis species

The global distribution of most species of Canis (dogs and wolves) is shown, right. The grey wolf inhabits the forests of North America, northern Europe, and Siberia. The red wolf and Mexican wolf (original distributions shown) were once distributed more widely, but are now extinct in the wild except for reintroductions. In contrast, the coyote has expanded its original range and is now found throughout North and Central America. The range of the three jackal species overlap in the open savannah of eastern Africa. The dingo is distributed throughout Australia. Distribution of the domestic dog is global as a result of their association with humans. The dog has been able to interbreed with all other members of the genus listed here to form fertile hybrids. Contrast this with members of the horse family, in which hybrids are sterile.

Grey wolf

Grey wolf

Grey wolf

Coyote [range expansion]

Red wolf [former range]

Mexican wolf [former range]

Golden jackal Black-backed jackal Side-striped jackal

Dingo

Coyote

Coyote – red

Canis latrans

Red wolf

Mexican wolf

wolf hybrids

Canis rufus

Canis lupus baileyi

Interbreeding between Canis species

Dingo

Grey wolf

Canis familiaris dingo

Canis lupus

Domestic dog

Side-striped jackal Canis adjustus

Black-backed jackal Canis mesomelas

No Interbreeding

Canis familiaris

No Interbreeding

The ability of many Canis species to interbreed to produce fertile hybrids illustrates one of the problems with the traditional concept of the biological. Red wolves, grey wolves, Mexican wolves, and coyotes can all form fertile hybrids. Red wolves are very rare, and it is possible that hybridisation with coyotes has been a factor in their decline. By contrast, no interbreeding occurs between the three distinct species of jackal, even though their ranges overlap in the Serengeti of eastern Africa. These animals are highly territorial, and simply ignore members of the other jackal species.

Golden jackal Canis aureus

1. (a) Define the term biological species:

(b) In what way do the Canis species contradict the definition of a biological species?

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2. What type of barrier prevents the three species of jackal from interbreeding?

3. Describe the factor that has prevented the dingo from interbreeding with other Canis species (apart from the dog):

4. Describe a possible contributing factor to the occurrence of interbreeding between the coyote and red wolf:

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94 What are Ring Species? Key Idea: A ring species is a connected series of closely related populations, distributed around a geographical barrier, in which adjacent populations in the ring can interbreed, but those at the extremes of the ring are reproductively isolated. The ring species concept was proposed by Ernst Mayr in 1942 to account for the circumpolar distribution of species of herring gulls (Larus species). The idea of a ring species is attractive to biologists because it appears to show speciation

in action. However, such examples are rare, and rigorous analysis of supposed ring species, including the herring gull complex, have shown that they do not meet all the necessary criteria to be ring species as defined. Although ring species are rare, the concept is still helpful because it can allow us to reconstruct the divergence of populations from an ancestral species. Ring species also provide evidence that speciation may occur without complete geographical isolation.

What is a ring species?

Criteria for a ring species ffRing species develop from a single ancestral population

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1

2

3

4

5

with isolation by distance.

A: Natural populations along a cline (environmental gradient). Each population varies slightly from the next. 1

ffThey show expansion of their range around a geographic barrier, such a mountain range or desert.

ffAdjacent populations in the ring can interbreed to produce fertile offspring (gene flow).

1

ffThe terminal populations are reproductively isolated.

5

2

5

B

4

C

2

3

4

3

The variation in populations may occur in a geographical ring, e.g. around a continental shoreline (B). Adjacent populations in the cline can interbreed. If the ring closes (C), the populations at the extremes of the ring may meet but are too different to interbreed.

The circumpolar distribution of Larus subspecies (still often cited in many texts) inspired Mayr to propose the ring species hypothesis. However, mtDNA studies (Liebers et al. 2004) have indicated that there were two ancestral gull populations (not one) and most of Mayr's subspecies in fact deserve species status. Moreover, the Larus complex includes several species, excluded by Mayr, whose taxonomy is unclear. Ring species appear to be a very rare phenomenon if they exist at all. In contrast, cryptic (hidden) species, which are morphologically identical but behave as (reproductively isolated) true species, appear to be common.

Photo right: Greenish warbler populations occupy a ring around the Tibetan Plateau. Eastern and western populations meet in Siberia but do not interbreed. Analyses support their status as a ring species.

JM Garg CC 3.0

Omasz G. Sienicki CC 3.0

Photo left: The herring gull (front) and black-backed gull (rear) do not interbreed at the ends of the circumpolar ring where they coexist. However, genetic analyses do not support a ring species.

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1. What is a ring species?

2. Why is the phenomenon of ring species interesting to evolutionary biologists?

3. Explain why the populations the two extremes of a geographical ring, as depicted in the diagram, cannot interbreed:

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95 Ring Species: The Greenish Warbler desert which includes the Tibetan Plateau, and Taklamakan and Gobi deserts, and extends into Siberia. In Siberia, two distinct subspecies coexist and do not interbreed, but are apparently connected by gene flow around the Himalayas to the south. The greenish warblers may thus form a rare example of a ring species.

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Key Idea: Genetic and song analyses provide strong evidence that greenish warblers form a ring species that originated south of the Himalayas. Greenish warblers (Phylloscopus trochiloides) are found in forests across much of northern and central Asia. They inhabit the ring of mountains surrounding the large area of Populations spread both east and west along the Himalayas. Populations developed unique characteristics, but adjacent populations remained able to breed together.

East and west populations eventually rejoined in Siberia, but because of morphological, behavioural, and genetic differences they do not interbreed.

No gene flow

X

E

H

D

G

C

Genetic data and analysis of song spectra point to a single species establishing on the southern edge of the Himalayas about 10,000 years ago.

B

F

A

Gene flow

The greenish warbler has been touted as "Darwin's missing evidence", showing how one species can diverge and evolve into two when populations are separated and subjected to different selection pressures.

Song spectra of the greenish warbler

B

C

D

E

A

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The two coexisting subspecies of greenish warblers are distinguished by their songs and the number of bars on the wings. The warbler in western Siberia has one light bar across the top of the wing, while the warbler in eastern Siberia has two. Analysis of the songs around the ring show that all songs can be traced to the population labelled A above. Songs become progressively different moving east or west around the ring. The songs of the eastern warblers (H) and western warblers (E) in Siberia are so different that neither recognises the other. Eastern and western forms have subspecies status.

JM Garg, Wikipedia CC 3.0

F

1. How do the eastern and western Siberian populations of greenish warblers differ?

2. Explain how these differences might have occurred:

3. Explain why the greenish warbler is described as "evolution in action":

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96 Prezygotic Reproductive Isolating Mechanisms be associated with behaviour, morphology, or reproductive timing. Single barriers to gene flow (such as geographical barriers) are usually insufficient to isolate a gene pool, so most species commonly have more than one type of barrier. Geographical barriers are not strictly a reproductive isolating mechanism, because they are not part of the species’ biology, although they are usually a necessary precursor to reproductive isolation in sexually reproducing populations.

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Key Idea: Reproductive isolating mechanisms prevent interbreeding between different species. Prezygotic isolating mechanisms occur before fertilisation can take place. Reproductive isolation prevents successful interbreeding between species and is crucial to maintaining species' integrity. Prezygotic isolating mechanisms operate before fertilisation can occur and prevent "gamete wastage". They are the most common type of isolating mechanism and may

Geographical isolation

Example: Geological changes to the lake basins has been instrumental in the proliferation of cichlid fish species in the rift lakes of East Africa (far right). Similarly, many Galápagos Island species (e.g. iguanas, finches) are now quite distinct from the Central and South American mainland species from which they separated.

Lake Victoria

Lake Tanganyika

Lake Malawi

NASA Earth Observatory

Geographical isolation describes the isolation of a species population (gene pool) by some kind of physical barrier, for example, mountain range, water body, isthmus, desert, or ice sheet. Geographical isolation is a frequent first step in the subsequent reproductive isolation of a species.

Hochstetter’s frog

Archey’s frog

Example: Hochstetter’s and Archey’s frogs (right) are sympatric (occur in the same geographical area) in the Coromandel region, but occupy different habitats within that range. Archey’s frog has no webbing between the toes and is found in forested areas away from water where it climbs into damp vegetation. Hochstetter's frog has partial toe webbing and prefers stream margins.

David M. Green cc2.5

Ecological isolation describes the existence of a prezygotic reproductive barrier between two species (or sub-species) as a result of them occupying or breeding in different habitats within the same general geographical area. Ecological isolation includes small scale differences (e.g. ground or tree dwelling) and broad differences (e.g. desert vs grasslands). Ecological isolation often follows geographical isolation, but in many cases the geographical barriers may remain in part.

Photos: DOC-CV

Ecological (habitat) isolation

Periodical cicada emerging

Lorax

Example: Closely related animal species may have different breeding seasons or periods of emergence to prevent interbreeding. The periodical cicadas (Magicicada genus) are an excellent example of this. Periodical cicadas are found in North America. There are several species and some have an overlapping distribution. Most of their life is spent underground as juveniles, emerging to complete their development and to mate. To prevent interbreeding, the various species spend either 13 or 17 years underground developing. Emergence of a single species is synchronised so the entire population emerges at the same time to breed.

Bruce Marlin

Temporal isolation means isolated in time, and it prevents species interbreeding because they mate or they are active at different times. For example individuals from different species do not mate because they are active during different times of the day (e.g. one species is active during the day and the other at night) or in different seasons.

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Periodical cicada

Temporal isolation

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The gametes (eggs and sperm) from different species are often incompatible, so even if the gametes meet, fertilisation is unsuccessful. Gamete isolation is very important in aquatic environments where the gametes are released into the water and fertlisation occurs externally (e.g. reproduction in frogs, fish, and coral). Where fertilisation is internal, the sperm may not survive in the reproductive tract of another species. If the sperm does survive and reach the egg, chemical differences in the gametes prevent fertilisation. Chemical recognition is also used by flowering plants to recognise pollen from the same species. Pollen from a different species is recognised as foreign and it does not germinate.

Male frigatebird display

Behavioural Isolation

In many species, courtship behaviours are a necessary prelude to successful mating. These behaviours may include dances, calls, displays, or the presentation of gifts. The displays are very specific and are unique to each species. This means that mates of the same species recognise and are attracted to the individual performing the behaviour, but members of other species do not recognise or pay attention to the behaviours.

Frog calling

Birds exhibit a wide range of courtship displays. The use of song is widespread but ritualised movements, including nest building, are also common. Example: GalĂĄpagos frigatebirds have an elaborate display in which they inflate a bright red throat pouch to attract a mate.

Empid flies mating

Mechanical (morphological) isolation Structural differences (incompatibility) in the anatomy of reproductive organs prevents sperm transfer between individuals of different species. This is an important isolating mechanism preventing breeding between closely related species of arthropods.

+

Species A

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Many flowering plants have coevolved with their animal pollinators and have flower structures to allow only that insect access. Structural differences in the flowers and pollen of different plant species prevents cross breeding because pollen transfer is restricted to specific pollinators and the pollen itself must be species compatible.

Species B

Orchid

+

Male tree frog calling

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Taollan82; Kirt L. Onthank cc3.0

Red sea urchin

Example: Two species of sea urchin, the red sea urchin (Strongylocentrotus franciscanus) and the purple sea urchin (Strongylocentrotus purpuratus), share the same geographic range. Sea urchins release their gametes into the sea water, but the two species do not interbreed because their gametes are not compatible.

Example: The sexual organs of empid flies have a lock-and-key mechanism. Without the right shaped genitalia, individuals cannot mate.

Kirt L. Onthank cc3.0

Purple sea urchin

Gamete Isolation


130 1. (a) What is a reproductive isolating mechanism?

(b) What role do isolating mechanisms have in maintaining the integrity of a species?

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2. What is a prezygotic isolating mechanism?

3. (a) Why is geographical isolation not regarded as a reproductive isolating mechanism?

(b) Explain why, despite this, it often precedes, and is associated with, reproductive isolation:

4. Distinguish between geographical and ecological isolation:

5. Identify the type(s) of reproductive isolation described in the following examples:

Breeding season for species B

Breeding season for species A

(a) Two species of butterfly (right) coexist in the same habitat but have different breeding seasons:

(b) Male bowerbirds construct elaborate bowers (shelters) to attract a mate. One species, the MacGregor's bowerbird builds a tall structure and decorates it with charcoal. A second species, the satin bowerbird, decorates its bower with bright blue objects:

J

F

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A

M

J

J

A

S

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D

(c) Two species of New Zealand skinks, Oligosoma smithi and O. suteri are sympatric (same area) in north-eastern New Zealand. O. smithi is diurnal and gives birth to live young. O. suteri is nocturnal and lays eggs.

(d) The blackbird (Turdus merula) and the ring ouzel (Turdus torquatus) are two closely related species found in Europe. The blackbird is a woodland species and the ring ouzel tends to inhabit highlands:

(e) Two species of sage plants coexist in a region of Southern California. Black sage (Salvia mellifera) has small flowers and is pollinated by small bees while white sage (S. apiana) has larger flowers providing a larger landing platform for its larger pollinator, carpenter bees. The two species of sage remain reproductively isolated.

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White sage

Black sage

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97 Postzygotic Isolating Mechanisms integrity of closely related species. There are several different postzygotic mechanisms operating at different stages. The first prevents development of the zygote. Even if the zygote develops into a viable offspring there are further mechanisms to prevent long term viability. These include premature death or (more commonly) infertility.

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Key Idea: Postzygotic isolating mechanisms operate after fertilisation has occurred. Postzyotic reproductive isolating mechanisms occur after fertilisation (formation of the zygote) has occurred. Postzygotic isolating mechanisms are less common than prezygotic mechanisms, but are important in maintaining the

Hybrid inviability

Mating between individuals of two species may produce a zygote (fertilised egg), but genetic incompatibility may stop development of the zygote. Fertilised eggs often fail to divide because of mis-matched chromosome numbers from each gamete. Very occasionally, the hybrid zygote will complete embryonic development but will not survive for long.

Hybrid sterility

Even if two species mate and produce hybrid offspring that are vigorous, the species are still reproductively isolated if the hybrids are sterile (genes cannot flow from one species’ gene pool to the other). Such cases are common among the horse family (such as the zebra and donkey shown on the right). One cause of this sterility is the failure of meiosis to produce normal gametes in the hybrid. This can occur if the chromosomes of the two parents are different in number or structure (see the “zebronkey” karyotype on the right). The mule, a cross between a donkey stallion and a horse mare, is also an example of hybrid vigour (they are robust) as well as hybrid sterility. Female mules sometimes produce viable eggs but males are infertile.

Sheep (Ovis) 54 chromosomes

Zebra stallion (2N = 44)

Goat (Capra) 60 chromosomes

X

Donkey jenny (2N = 62)

Karyotype of ‘Zebronkey’ offspring (2N = 53)

Y

Chromosomes contributed by zebra stallion

Chromosomes contributed by donkey jenny

X

AKA

For example, although sheep and goats seem similar (right) and can be mated together, they belong to different genera. Any offspring of a sheep-goat pairing is generally stillborn.

Hybrid breakdown

Hybrid breakdown is common feature of some plant hybrids. The first generation (F1) may be fertile, but the second generation (F2) are infertile or inviable. Examples include hybrids between species of cotton (near right), species within the genus Populus, and strains of the cultivated rice Oryza (far right).

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1. Postzygotic isolating mechanisms are said to reinforce prezygotic ones. Explain why this is the case:

2. Briefly describe how each of the postzygotic isolating mechanisms maintains reproductive isolation:

(a) Hybrid inviability:

(b) Hybrid sterility:

(c) Hybrid breakdown:

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98 Allopatric Speciation populations diverge after geographical separation (allopatric literally means 'other fatherland' in ancient Greek). It has been important in speciation in New Zealand, which has experienced a number of cycles of geographical fragmentation throughout its history as a result of glacials and interglacials.

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Key Idea: Allopatric speciation is the divergence of a species after it is subdivided into geographically isolated populations. Speciation (the formation of new species) most commonly occurs as a result of population separation and subsequent isolation. This is called allopatric speciation because the

Stage 1: Moving into new environments

There are times when the range of a species expands for a variety of different reasons. A single population in a relatively homogeneous environment will move into new regions of their environment when they are subjected to intense competition (whether it is interspecific or intraspecific). The most severe form of competition is between members of the same species since they are competing for identical resources in the habitat. In the diagram on the right there is a 'parent population' of a single species with a common gene pool with regular 'gene flow' (theoretically any individual has access to all members of the opposite sex for mating purposes).

Parent population

Stage 2: Geographical isolation

Isolation of parts of the population may occur due to the formation of physical barriers, such as mountains, deserts, or stretches of water. These barriers may cut off those parts of the population that are at the extremes of the range and gene flow is prevented or rare. The rise and fall of the sea level has been particularly important in functioning as an isolating mechanism. Climatic change can leave 'islands' of habitat separated by large inhospitable zones that the species cannot traverse. Example: In mountainous regions, alpine species can populate extensive areas of habitat during cool climatic periods. During warmer periods, they may become isolated because their habitat is reduced to ‘islands’ of high ground surrounded by inhospitable lowland habitat.

Isolated population B

Parent population

River barrier prevents gene flow

Mountain barrier prevents gene flow

Isolated population A

Stage 3: Different selection pressures

The isolated populations (A and B) may be subjected to quite different selection pressures. These will favour individuals with traits that suit each particular environment. For example, population A will be subjected to selection pressures that relate to drier conditions. This will favour those individuals with phenotypes (and therefore genotypes) that are better suited to dry conditions. They may for instance have a better ability to conserve water. This would result in improved health, allowing better disease resistance and greater reproductive performance (i.e. more of their offspring survive). Finally, as allele frequencies for certain genes change, the population takes on the status of a subspecies. Reproductive isolation is not yet established but the subspecies are significantly different genetically from other related populations.

Wetter climate

Drier climate

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Subspecies A

Sympatric species

The separated populations (isolated subspecies) undergo genetic and behavioural changes. These ensure that the gene pool of each population remains isolated and 'undiluted' by genes from other populations, even if the two populations should be able to remix (due to the removal of the geographical barrier). Gene flow does not occur. The arrows (diagram, right) indicate the zone of overlap between two species after Species B has moved back into the range inhabited by the parent population. Closely-related species whose distribution overlaps are said to be sympatric species. Those that remain geographically isolated are called allopatric species.

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Subspecies B

Parent population

Stage 4: Reproductive isolation

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Parent population

Allopatric species

Species B

River barrier disappears

Mountain barrier remains

Species A

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133 1. Distinguish between an allopatric and sympatric species:

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2. Why do some animals, given the opportunity, might move into new environments?

3. Plants are unable to move. How might plants disperse to new environments?

4. Describe the amount of gene flow within a parent population prior to and during the expansion of a species' range:

5. Explain how cycles of climate change can cause large changes in sea level (up to 200 m):

6. (a) What kinds of physical barriers could isolate different parts of the same population?

(b) How might emigration achieve the same effect as geographical isolation?

7. (a) How might selection pressures differ for a population that becomes isolated from the parent population?

(b) Describe the general effect of the change in selection pressures on the allele frequencies of the isolated gene pool:

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8. Explain how reproductive isolation could develop in geographically separated populations:

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99 Small Flies and Giant Buttercups Kauai

Drosophilidae (commonly known as fruit flies) are a group of small flies found almost everywhere in the world. Two genera, Drosophila and Scaptomyza are found in the Hawaiian islands and between them there are more than Maui 800 species present on a land area of just 16,500 km2; it is one of the The major dispersals densest concentrations of related species found anywhere. The flies range of Drosophila and from 1.5 mm to 20 mm in length and display a startling range of wing forms Scaptomyza. and patterns, body shapes and colours, and head and leg shapes. This diverse array of species and characteristics has made these flies the subject of much evolutionary and genetics research. Genetic analyses show that they are all related to a single species that may have arrived on the islands around 8 million years ago and diversified to exploit a range of unoccupied Hawaii niches. Older species appear on the older islands and more recent species appear as one moves from the oldest to the newest islands. Such evidence points to numerous colonisation events as new islands emerged from Drosophila setosimentum, the sea. The volcanic nature of the islands means that newly isolated a picture winged fly. environments are a frequent occurrence. For example, forested areas may become divided by lava flows, so that flies in one region diverge rapidly from Photo: Karl Magnacca flies in another just tens of metres away. One such species is D. silvestris. Males have a series of hairs on their forelegs, which they brush against females during courtship. Males in the northeastern part of the island have many more of these hairs than the males on the southwestern side of the island. While still the same species, the two demes are already displaying structural and behavioural isolation. Behavioural isolation is clearly an important phenomenon in drosophilid speciation. A second species, D. heteroneura, is closely related to D. silvestris and the two species live sympatrically. Although hybrid offspring are fully viable, hybridisation rarely occurs because male courtship displays are very different.

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Oahu

Photo: Velela

New Zealand alpine buttercups (Ranunculus) are some of the largest in the world and are also the product of repeated speciation events. There are 14 species of Ranunculus in New Zealand; more than in the whole of North and South America combined. They occupy five distinct habitats ranging from snowfields and scree slopes to bogs. Genetic studies have shown that this diversity is the result of numerous isolation events following the growth and recession of glaciers. As the glaciers retreat, alpine habitat becomes restricted and populations are isolated at the tops of mountains. This restricts gene flow and provides the environment for species divergence. When the glaciers expand again, the extent of the alpine habitat increases, allowing isolated populations to come in contact and closely related species to hybridise.

1. Explain why so many drosophilidae are present in Hawaii:

2. Explain why these flies are of interest:

4. Explain why New Zealand has so many alpine buttercups:

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3. Describe the relationship between the age of the islands and the age of the fly species:

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100 Divergence in Allopatric Populations increase and the populations become increasingly isolated from each other. The isolation of the two gene pools may begin with a geographical barrier. This may be followed by progressively greater reduction in gene flow between the populations until the two gene pools are isolated and they each attain species status.

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Key Idea: Speciation may occur in stages marked by increasing isolation of diverging gene pools. Physical separation is followed by increasing reproductive isolation. The diagram below shows a possible sequence of events in the origin of two new species from an ancestral population. Over time, the genetic differences between two populations

Ancestral population

A species of butterfly lives on a plateau. The plateau is covered with grassland strewn with boulders. During colder weather, some butterflies sit on the sun-heated boulders to absorb the heat, while others retreat to the lower altitude grassland to avoid the cold.

Population splits

Population B

Population A

Continued mountain building raises the altitude of the plateau, separating two populations of butterflies, one in the highlands the other in the lowlands.

Evolutionary development or time

Gene flow common

Race B

Race A

Gene flow uncommon

Subspecies B

Subspecies A

Species B

Species A

Separate species

1. Identify the variation in behaviour in the original butterfly population:

Over time, only boulder-sitting butterflies are found in the highlands and grass-sitting butterflies in the lowlands. Occasionally wind brings members of the two groups together, but if they mate, the offspring are usually not viable or have a much lowered fitness.

Eventually gene flow between separated populations ceases as variation between the populations increases. They fail to recognise each other as members of the same species.

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Gene flow very rare

In the highlands, boulder-sitting butterflies (BSBs) do better than grass-sitting butterflies (GSBs). In the lowlands, the opposite is true. BSBs only mate on boulders with other BSBs. Darker BSBs have greater fitness than light BSBs. (they can absorb more heat from the boulders). In the lowlands, light GSBs blend in with the grass and survive better than darker butterflies.

2. What were the selection pressures acting on BSBs in the highlands and GSBs in the lowlands respectively?

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101 Polyploidy as a Source of Variation and has been important in the evolution and speciation of flowering plants (angiosperms). Polyploidy in plants produces a species that is reproductively isolated from the “parent” species, and results in instant speciation. Allopolyploidy (involving different species) and autopolyploidy (involving the same species) are both recognised.

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Key Idea: Polyploidy is a condition in which a cell or organism has three or more times the haploid chromosome number. Polyploidy cells or organisms contain more than two haploid number of chromosomes (i.e. 3N or more). It arises when chromosomes fail to correctly separate during mitosis or meiosis. Polyploidy is rare in animals, but common in plants,

Autopolyploidy

Polyploids that arise within a species are called autopolyploids (the extra chromosomes come from another organism of the same species). Autopolyploidy occurs when chromosomes fail to separate during meiosis or when the cell fails to divide after the chromatids have separated. If a diploid gamete fuses with a haploid gamete, a triploid is formed. Triploids are generally unstable and sterile. However, if two diploid gametes fuse, the resulting tetraploid can be fertile.

Same species

Same species

AA

AA

AA

A

AA

AA

Normal haploid gamete

AA

Diploid gametes

AA

Diploid gamete

AAA

Sterile hybrid

AAAA

Triploid 3N

Fertile hybrid

Tetraploid 4N

Potatoes (left) are autopolyploids. They have a number of ploidy levels, based on a haploid number of 12, ranging from diploid (2n=24) to hexaploid (6n=72). Cultivated potato varieties are tetraploid (4n=48).

Allopolyploidy

Species A

Species B

AA

Infertile hybrid

BB

A

AB

B

Infertile hybrid reproduces asexually.

AABB

AB

cc 3.0 Honeyhuyue

Non-disjunction doubles the chromosome number in the hybrid.

AB

AABB

Union of gametes from this hybrid produces a new species of interbreeding plants: a fertile allopolyploid.

Species C Many crops are allopolyploids, including wheat, rice, and modern brassicas (above).

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Allopolyploidy occurs when two species interbreed to produce a new hybrid with chromosomes from each of the parent species. The hybrid is infertile because the chromosomes cannot pair up. However, mitotic non-disjunction in the sterile hybrid can double the chromosome number and produce homologues, which can pair up during meiosis. Self-fertilisation may then produce a viable, fertile hybrid. Many commercial plant varieties are allopolyploids. They show greater heterozygosity and hybrid vigour than autopolyploids.

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137 Advantages of polyploidy ffThe high frequency of polyploidy in plants indicates that polyploidy provides an adaptive advantage. Often this advantage is the result

of hybrid vigour, where the hybrid shows improvements over the parents (e.g. by being larger or growing more vigorously). The increase in heterozygosity (heterozygous for a gene) reduces the frequency of (expressed) recessive mutations and also contributes to hybrid vigour.

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ffPolyploidy results in gene redundancy and provides opportunities to diversify gene function. Extra copies of the gene not required for

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its original function can be adapted for use in a different way. This can provide an evolutionary advantage. Many polyploids show novel variation or morphologies relative to their parental species.

Common wheat 6N = 42

Tobacco 4N = 48

Banana 3N = 27

Boysenberry 7N = 49

Strawberry 8N = 56

Kiwifruit 6N = 174

Polyploids can be induced ffNew plant varieties can be made by inducing

non-disjunction with chemicals. The induction of polyploidy is a common technique to overcome hybrid sterility during plant breeding.

ffChemicals such as colchicine (right) and N2O

gas inhibit spindle fibre formation and stop the separation of chromosomes during mitosis.

ffIn plants, seeds or seedlings are soaked in a

solution of a spindle inhibiting chemical. The resulting plants will likely develop as polyploids. These can then be propagated and crossed (if fertile) to produce a new variety of plant.

Colchicine

ffSeedless banana and watermelon fruits are produced on triploid

plants, which cannot produce fertile gametes (therefore no seeds).

ffNon-disjunction is induced in a diploid to produce a tetraploid, which is crossed with a normal diploid to produce the seedless triploid hybrid.

1. Explain how polyploidy can result in instant genetic isolation?

2. (a) What advantages do polyploid organisms often have over the parent species?

(b) Explain the origin of these advantages:

4. (a) How does non-disjunction result in polyploidy?

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3. Distinguish between autopolyploidy and allopolyploidy:

(b) Using an example, explain how deliberate induction of non-disjunction can be used in producing crop varieties:

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102 Sympatric Speciation geographic region. Sympatric speciation is rarer than allopatric speciation, although it is not uncommon in plants which form polyploids. There are two situations where sympatric speciation is thought to occur. These are described below. An insect forced to lay its eggs on an An insect forced lay its may eggsgive on an unfamiliar plant to species rise unfamiliar speciesofmay rise to a newplant population fliesgive isolated to a new ofpopulation. flies isolated frompopulation the original from the original population.

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Key Idea: Sympatric speciation is speciation which occurs even when there is no physical barrier separating gene pools. In sympatric (same place) speciation, a new species evolves from a single ancestral species while inhabiting the same

Speciation through niche differentiation

Niche isolation

In a heterogeneous environment (one that is not the same everywhere), there are many microhabitats within the region inhabited by a population. Some organisms prefer to occupy one particular microhabitat most of the time, only rarely coming in contact with those that prefer other microhabitats. Some organisms become so dependent on the resources offered by their particular microhabitat that they never interact with their counterparts in different microhabitats.

Reproductive isolation

Individual groups, which have remained genetically isolated because of their microhabitat preferences, become reproductively isolated. They have become new species with subtle differences in behaviour, structure, and physiology. Gene flow (via sexual reproduction) is limited to organisms that share similar microhabitat preferences (as shown right).

Original host plant species Original host plant species Original host Original host plant species plant species

Example: Some host-specific phytophagous insects (insects that feed on plants) prefer to lay eggs on plants identical to the species they themselves hatched on. Host plant preference leads to isolation within the same geographical area.

Instant speciation by polyploidy

Polyploidy may result in the formation of a new species without isolation from the parent species. This event, occurring during meiosis, produces sudden reproductive isolation for the new group. Because the sex-determining mechanism is disturbed, animals are rarely able to achieve new species status this way (they are sterile). Many plants, on the other hand, are able to reproduce vegetatively, or carry out self pollination. This ability to reproduce on their own enables such polyploid plants to produce a breeding population.

New host plant species New host plant species New host New host plant species plant species

No gene No flow gene flow

Gene flow Gene flow

Origin of Origin ofevent polyploid polyploid event

Parent Parent population population

Speciation by allopolyploidy

This type of polyploidy usually arises from the doubling of chromosomes in a hybrid between two different species. The doubling often makes the hybrid fertile.

Examples: Modern wheat. Swedes are polyploid species formed from a hybrid between a type of cabbage and a type of turnip.

New polyploid plant species New polyploid plantthrough speciesthe spreads outwards spreads outwards the existing parent through population existing parent population

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1. Explain what is meant by sympatric speciation:

2. What is the mechanism for instant speciation? Explain why it is more common in plants than in animals:

3. Explain how niche differentiation could result in the formation of a new species:

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103 Polyploidy and Speciation in Melicytus

Melissa Hutchinson

M. alpinus growth form

Jeremy Rolfe

range of habitats ranging from coastal regions to alpine areas. Polyploidy has played an important role of speciation in Melicytus, including in the most recently named M. drucei, a hybrid found only on Mt. Taranaki. M. drucei is unusual in that it is a stable triploid (3N). The other Melicytus species are diploids (2N) or tetraploids (4N).

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Key Idea: Polyploidy has been an important factor in the evolution of the Melicytus species in New Zealand. The Melicytus genus of plants found in New Zealand comprise 11 species of shrubs and small trees including mahoe. They are divaricating, meaning they have intertangled branches at wide angles to each other. They are found in a diverse

M. alpinus flowers

M. flexuosus

M. flexuosus (left) can grow up to 5 m tall. It is restricted to a few regions south of Pureora in the North Island but widespread throughout the South Island. It has divaricating, near leafless branches with many lenticels (pores) for gas exchange through the stems. It produces small flowers, which sit under the branches. M. flexuosus is diploid (2N=32).

ffM. drucei (right) probably arose through a hybridisation event between M.

flexuosus and M. alpinus. M. drucei, is found only in the Ahukawakawa Swamp and Pouakai Range within Egmont National Park (Taranaki). It is restricted by the Pouakai volcano, and the extent of its habitat is 2 ha.

ffBoth parent species occur in the Central North Island but not within Egmont

National park. The hybridisation event would have occurred when the parent species had more widespread distributions. The limited distribution of M. drucei suggests its formation was a single hybridisation event.

so it is called a permanent odd triploid. M. drucei is most similar in appearance to M. flexuosus, but in height and flower type it resembles the M. alpinus group. M. drucei, is a triploid (2N=48).

M. drucei foliage

With thanks to Bruce Clarkson, Jeremy Wolfe, Melissa Hutchinson, John Barkla, and Rewi Elliot and the NZ Plant Conservation Network for photographs.

WM Clarkson

ffM. drucei is unusual in that it is a stable triploid and produces viable offspring,

1. Has M. drucei arisen through autopolyploidy or allopolyploidy? 2. Using M. drucei as an example, discuss the role of polyploidy in speciation of Melicytus:

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John Barkla

M. alpinus (above) is found on coastal and dry alpine areas of the southern North Island and the South Island. It is a dense shrub growing 1-2 m tall. The external branches look like porcupine quills (hence its common name, porcupine shrub). Most of the leaves are found within the canopy, an adaptation to reduce water loss in dry climates. The small weather resistant flowers (top right) are produced in spring and early summer. M. alpinus is a tetraploid (2N = 64)

3. What evidence is there to suggest that M. drucei arose from a single hybridisation event?

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LINK

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104 Polyploidy and the Domestication of Wheat in the domestication of wheat. Polyploidy has also played a major role in the evolution of crop plants. Most higher organisms are diploid, i.e. have two sets of chromosomes (2N), one set derived from each parent. Diploids formed from hybridisation of different species are usually infertile because the two sets of chromosomes cannot pair properly at meiosis. In such hybrids, there are no gametes produced or the gametes are abnormal. In some cases of allopolyploidy, the chromosomes can be doubled and a tetraploid is formed from the diploid. This restores fertility to a hybrid, because each of the original chromosome sets can pair properly with each other during meiosis. These processes are outlined below.

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Key Idea: The evolution of wheat involved two natural hybridisation events, accompanied by polyploidy. Wheat has been cultivated for more than 9000 years and has undergone many changes during the process of its domestication including hybridisation and polyploidy. Hybrids are the offspring of genetically dissimilar parents. They are important because they recombine the genetic characteristics of parental lines and show increased heterozygosity. This is associated with greater adaptability, survival, growth, and fertility in the offspring (called hybrid vigour). There is evidence to show that interspecific hybridisation (hybridisation between different species) was an important evolutionary mechanism

Polyploidy events in the evolution of wheat

The wild einkorn becomes domesticated in the Middle East. Slight changes in the phenotype occur, but not in the chromosome number.

These two species interbred to form a hybrid and would have initially been sterile.

Wild einkorn

Einkorn

Genome

Genome

2N no.

2N no.

Wild grass

Genome

X

2N no.

The sterile hybrid undergoes amphiploidy (an allopolyploidy event involving doubling the chromosome number in a hybrid between two species). This creates the fertile emmer wheat.

Goat grass

Genome

Common wheat

2N no.

Emmer Wheat

Genome

2N no.

X

Genome

The table on the right and the diagram above show the evolution of the common wheat. Common wheat is thought to have resulted from two sets of crossings between different species to produce hybrids.

Wild einkorn (14 chromosomes, genome AA) evolved into einkorn, which crossed with a wild grass (14 chromosomes, genome BB) and gave rise to emmer wheat (28 chromosomes, genome AABB). Common wheat arose when emmer wheat was crossed with another type of grass (goat grass).

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104 101

Common name

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Sterile hybrid undergoes amphiploidy, doubling the number of chromosomes to create the fertile common wheat.

2N no.

KNOW

These two species interbred to form a hybrid and would have initially been sterile.

Species

Genome

Chromosomes N

Wild einkorn

Triticum aegilopiodes

AA

7

Einkorn

Triticum monococcum

AA

7

Wild grass

Aegilops speltoides

BB

7

Emmer wheat

Triticum dicoccum

AABB

14

Goat grass

Aegilops squarrosa

DD

7

Common wheat

Triticum aestivum

AABBDD

21

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Teosinte

Ancient cereal grasses had heads which shattered readily so that the seeds would be scattered widely.

Modern corn

Modern wheat has been selected for its non-shattering heads, high yield, and high gluten content.

Corn has also evolved during its domestication. Teosinte is thought to be the ancestor to both corn and maize.

1. Using the table on the previous page, label each of the wheats and grasses in the diagram with the correct genome and 2N chromosome number for each plant.

2. Explain the term hybrid vigour:

3. Discuss the role of polyploidy and interspecific hybridisation in the evolution of wheat:

4. Cultivated wheat arose from wild, weedy ancestors through the selection of certain characters.

(a) Identify the phenotypic traits that are desirable in modern wheat varieties:

(b) Suggest how ancient farmers would have carried out a selective breeding programme:

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5. Cultivated American cotton plants have a total of 52 chromosomes (2N = 52). In each cell there are 26 large chromosomes and 26 small chromosomes. Old World cotton plants have 26 chromosomes (2N = 26), all large. Wild American cotton plants have 26 chromosomes, all small. Briefly explain how cultivated American cotton may have originated from Old World cotton and wild American cotton:

6. Why is it important to maintain the biodiversity of wild plants and ancient farm breeds?

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105 What You Know So Far: Isolation and Speciation Reproductive isolating mechanisms

HINT: Explain prezygotic and postzygotic mechanisms

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you: Species concept

HINT: How do you define a species?

Processes of speciation

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HINT: Include definitions for allopatric and sympatric speciation. Explain the role of polyploidy in instant speciation.

REVISE

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106 NCEA Style Question: Speciation Distribution of killer whales in Antarctic waters

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1. Killer whales (Orcinus orca) are found throughout the world's oceans. Researchers have identified that different killer whale populations follow different types of hunting behaviour. In the waters around Antarctica, five populations have been identified (F to J). DNA evidence indicates these populations began to diverge about 250,000 years ago.

Population Population Population Population Population

F prefers to hunt seals on pack ice G's preferred prey is penguins H hunts minke whales I prefers to hunt Patagonian toothfish J hunts Antarctic toothfish.

Researchers believe that these killer whale populations are showing sympatric speciation.

J

F

H

G

I

Source: R. Riesch, Sci. American, Nov. 2016, pp. 54-61

Discuss sympatric speciation using the killer whales as an example. In your discussion include: • how sympatric speciation occurs • the relevant reproductive isolating mechanisms • an explanation of how sympatric speciation differs from allopatric speciation. • a justification as to whether or not sympatric speciation is indeed occurring in killer whales.

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TEST


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107 KEY TERMS AND IDEAS: Isolation and Speciation 1. Test your vocabulary by matching each term to its definition, as identified by its preceding letter code.

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allopatric speciation

A A reproductive isolating mechanism that occurs after formation of the zygote.

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polyploidy

B The division of one species, during evolution, into two or more separate species.

postzygotic isolating mechanism

C The situation in which members of a group of organisms breed with each other but not with members of other groups.

prezygotic isolating mechanism

D Speciation as a result of reproductive isolation without any physical separation of the populations, i.e. populations remain within the same range.

reproductive isolation

E

The condition of having a chromosome complement of more than 2N (e.g. 3N).

speciation

F

Group or population of individuals that can interbreed to produce viable offspring.

G A reproductive isolating mechanism that occurs before formation of the zygote.

species

H Speciation in which the populations are physically separated.

sympatric speciation

2. In the following examples, classify the reproductive isolating mechanism as either prezygotic or postzygotic and describe the mechanisms by which the isolation is achieved (e.g. structural isolation, hybrid sterility etc.):

(a) Some different cotton species can produce fertile hybrids, but breakdown of the hybrid occurs in the next generation when the offspring of the hybrid die in their seeds or grow into defective plants:

Prezygotic / postzygotic (delete one)

Mechanism of isolation:

(c) Two skunk species do not mate despite having habitats that overlap because they mate at different times of the year:

Mechanism of isolation:

(b) Many plants have unique arrangements of their floral parts that stops transfer of pollen between plants:

Prezygotic / postzygotic (delete one)

Prezygotic / postzygotic (delete one)

Mechanism of isolation:

(d) Several species of the frog genus Rana, live in the same regions and habitats, where they may occasionally hybridise. The hybrids generally do not complete development, and those that do are weak and do not survive long:

Prezygotic / postzygotic (delete one)

Mechanism of isolation:

3. The diagram below shows the divergence of an ancestral population into two new species. In the boxes below, describe the level of gene flow and its effect for each of the labelled points (a-c):

Ancestral population

(a)

(b)

Population B

(a)

TEST

Subspecies A

Race B

(b)

Species A

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Race A

Population A

(c)

Subspecies B

Species B

(c)

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108 Divergent Evolution accumulation of genetic differences in diverging lines, usually following isolation, so that gene flow between them stops and new species arise. Divergence is a common evolutionary pattern. When it involves the diversification of a large number of species into different niches, it is called adaptive radiation.

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Key Idea: Divergent evolution describes the accumulation of differences between initially more similar lineages so that new species arise from a common ancestor. The divergence of two or more species from a common ancestor is called divergent evolution. It arises through the

An overview of divergent evolution

Species B

Species C

Changes in genetic makeup accumulate and gene flow stops

Divergent evolution in trilobites

mya 251 299 359 416 444

Trilobite diversity

Permian

Carboniferous Devonian Silurian

*

488

Divergent evolution: the lineage splits

Time

542

Common ancestor

Species A

Cambrian

* Ordovician

Trilobites are extinct marine arthropods. They were one of the earliest arthropod groups and were highly successful, diverging many times during their history to exploit a wide range of niches. They appeared in the fossil record near the beginning of the Cambrian and disappeared in the Permian mass extinction (above).

Divergent evolution in a New Zealand species: The saddlebacks

ffThe saddlebacks are a member of the New Zealand wattlebird family (Callaeidae). The family consists of the saddleback, kokako, and the extinct huia.

ffThere are two distinct species of saddleback; the North Island saddleback (Philesturnus rufusater) and the South Island saddleback (Philesturnus carunculatus).

mammalian predators during European settlement reduced the range and distribution of the saddleback. Today the range of the two species do not overlap.

ffWhile they have a similar appearance as adults, the two

1. (a) Define divergent evolution:

(b) What must generally occur for the new species to arise?

2. Suggest why the saddlebacks diverged into two separate species:

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The North Island saddleback

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species show differences in behaviour, breeding, and song. The juvenile birds of each species also differ in appearance.

Duncan Wright CC3.0

ffOnce common throughout New Zealand, the introduction of

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109 Convergent Evolution species from different evolutionary lineages come to resemble each other because they have similar habitats and ecological roles and natural selection has produced similar adaptations.

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Key Idea: Evolution in response to similar selection pressures can result in unrelated species appearing very similar. Convergent evolution describes the process by which

Convergence: same look, different origins

Not all similarities between species are the result of common ancestry. Selection pressures to solve similar problems in particular environments may result in similarity of form and function in unrelated (or distantly related) species. The evolution of succulence in unrelated plant groups (Euphorbia and the cactus family) is an example of convergence in plants. In the example (right), the selection pressures of the aquatic environment have produced a similar streamlined body shape in unrelated vertebrates. Icthyosaurs, penguins, and dolphins each evolved from terrestrial species that took up an aquatic lifestyle. Their general body form has evolved to become similar to that of the shark, which has always been aquatic. Note that flipper shape in mammals, birds, and reptiles is a result of convergence, but its origin from the pentadactyl limb is an example of homology (common ancestry).

Fish: Shark

Reptile: Icthyosaur (extinct)

Mammal: Dolphin

Bird: Penguin

Analogous structures (homoplasies) have the same function and often the same appearance, but different origins. The example (right) shows the structure of the eye in two unrelated taxa (mammals and cephalopod molluscs). The eye appears similar, but has evolved independently.

The wings of birds and insects are also analogous. The wings have the same function, but the two taxa do not share a common ancestor. Longisquama, a lizard-like creature that lived about 220 mya, also had ‘wings’ that probably allowed gliding between trees. These 'wings’ were highly modified long scales or feathers extending from its back and not a modification of the forearm (as in birds).

Jo Naylor cc2.0

Analogous structures arise through convergent evolution

Mammalian eye

Retina

Octopus eye

Iris

Iris

Lens

Lens

Cornea

Retina

Cornea

1. In the example above illustrating convergence in swimming form, describe two ways in which the body form has evolved in response to the particular selection pressures of the aquatic environment: (a)

(b)

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2. Describe two of the selection pressures that have influenced the body form of the swimming animals above: (a)

(b)

3. When early taxonomists encountered new species in the Pacific region and the Americas, they were keen to assign them to existing taxonomic families based on their apparent similarity to European species. In recent times, many of the new species have been found to be quite unrelated to the European families they were assigned to. Explain why the traditional approach did not reveal the true evolutionary relationships of the new species:

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4. For each of the paired examples, briefly describe the adaptations of body shape, diet and locomotion that appear to be similar in both forms, and the likely selection pressures that are acting on these mammals to produce similar body forms:

Convergence between marsupials and placentals

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Marsupial and placental mammals diverged very early in mammalian evolution (about 120 mya), probably in what is now the Americas. Marsupials were widespread throughout the supercontinent of Gondwana as it began to break up through the Cretaceous, but became isolated on the southern continents, while the placentals diversified in the Americas and elsewhere, displacing the marsupials in most habitats around the world. Australia's isolation from other landmasses in the Eocene meant that the Australian marsupials escaped competition with placentals and diversified into many species, ecologically equivalent to the placental species in North America.

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Australia

Wombat

(a)

Adaptations: Rodent-like teeth, eat roots and above ground plants, and can excavate burrows.

North America

Woodchuck

Selection pressures: Diet requires chisel-like

teeth for gnawing. The need to seek safety from predators on open grassland.

Flying phalanger

(b)

Adaptations:

Flying squirrel

Selection pressures:

Marsupial mole

(c)

Adaptations:

Mole

Selection pressures:

Marsupial mouse

(d)

Adaptations:

Mouse

Selection pressures:

(e)

Adaptations:

Selection pressures:

Long-eared bandicoot

Wolf

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Tasmanian wolf (tiger)

Jack rabbit

(f)

Adaptations:

Selection pressures:

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110 Coevolution to happen when different species have close ecological interactions with one another. These ecological relationships include predator-prey and parasite-host relationships, and mutualistic relationships such as those between plants and their pollinators. Competition can also drive coevolution because competitors will evolve adaptations, including those involving symbioses, that lead to niche specialisation and more efficient partitioning of available resources.

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Key Idea: Coevolution involves the reciprocal evolution of species that have close ecological relationships, such as those involving mutualism, competition, or exploitation. Coevolution involves the mutual (reciprocal) evolution of two or more species with an ecological relationship. Each party in the coevolution exerts selective pressures on the other and, over time, the species develop a relationship that may involve mutual dependency. Coevolution is likely

Bees are excellent pollinators; they are strong enough to enter intricate flowers and have medium length tongues which can collect nectar from many flower types. They have good colour vision, which extends into the UV, but they are red-blind, so bee pollinated flowers are typically blue, purplish, or white and they may have nectar guides that are visible as spots.

Predator/prey relationships

Pollinator/plant relationships

NZ’s short tailed bat pollinates wood rose flowers on the forest floor

Bats are nocturnal and colour-blind but have an excellent sense of smell and are capable of long flights. Flowers that have coevolved with bat pollinators are open at night and have light or drab colours that do not attract other pollinators. Bat pollinated flowers also produce strong fragrances that mimic the smell of bats and have a wide bell shape for easy access.

Competitive relationships

Parasite/host relationships

Crossbill

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LINK

39

LINK

40

Trypanosoma brucei

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Predators have evolved strategies to successfully exploit their prey. Effective offensive weapons (e.g. claws and teeth) and hunting ability (including cooperative hunting tactics) are important. In turn, prey have evolved numerous strategies to protect themselves from predators, including large size and strength, rapid escape tactics, protective coverings, defensive weapons, and toxicity. Lions have evolved the ability to hunt cooperatively to increase their chance of securing a kill from swift herd species such as zebra and antelope.

Hummingbirds are important pollinators in the tropics. Their needle-like bills and long tongues can take nectar from flowers with deep tubes. Their ability to hover enables them to feed quickly from dangling flowers. As they feed, their heads are dusted with pollen, which is efficiently transferred between flowers.

In most areas of the Rocky Mountains (USA) squirrels are the main predators of lodgepole pine seeds. In areas where there are no squirrels, crossbill birds are the main predator. Lodgepoles have evolved different pinecones depending on which is the main predator. Where squirrels dominate, the pinecones are heavy (harder to carry), have few seeds, and thin scales. Where crossbills dominate the cones are lighter with more seeds and thicker scales (harder to open). Crossbill bill shape varies depending on the region and cone type so that they can extract the seeds. LINK

41

Trypanosomes are protozoan parasites and are a good example of host-parasite coevolution. Trypanosomes have two hosts, humans and the tsetse fly. The fly vector spreads the parasite between human hosts. Trypanosomes have evolved strategies to evade their host’s defences, but their virulence is constrained by needing to keep their host alive so that they can complete their life cycle. Molecular studies show that Trypanosoma brucei coevolved in Africa with the first hominins around 5 mya, but T. cruzi contact with human hosts occurred in South America only after settlements were made by nomadic cultures. © 1988-2016 BIOZONE International ISBN: 978-1-927309-56-8 Photocopying Prohibited

CDC

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149

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1. (a) What is meant by coevolution?

(b) Why does coevolution occur?

2. Describe some of the strategies that have evolved in plants to attract pollinators:

4. In New Zealand, a mutualistic relationship exists between the beech mistletoe (Peraxilla genus) and its bird pollinators, the tui and bellbird (right). Beech mistletoe have explosive flowers requiring a pollinator to manually open the flower for pollination to occur. The birds twist open the flowers and as the buds spring open, pollen sprays out covering the bird. Pollen is transferred to the next flower the bird visits. Only the tui and bellbirds have access to the nectar inside the flower because not all birds know how to open the flowers. Some native bees have also learned to open the flowers, but they are poor pollinators of mistletoe, with low pollination efficiency.

(a) Why is the relationship between bellbirds and beech mistletoe mutualistic?

Bellbird pollinating mistletoe

(b) Discuss an evolutionary outcome if tui and bellbird numbers become significantly reduced over time:

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5. The monarch butterfly caterpillar feeds on plants in the milkweed family. The caterpillar has adaptations to survive the toxicity of milkweed, which poisons most other animal species. The milkweed's adaptations to surviving the browse damage caused by the monarch caterpillar include a rapid regrowth response when leaf tissue is damaged. (a) What type of ecological relationship is represented here?

(b) Describe the selection pressures on the monarch butterfly and the milkweed plant in this relationship and explain why it is an example of coevolution:

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Jenny Ladley UoC

3. Describe the constraints on the parasite in the coevolution of a host-parasite relationship:


111 Adaptive Radiation in Mammals diagram below shows the divergence of the mammals into major orders, many occupying niches left vacant by the dinosaurs. The vertical extent of each grey shape shows the time span for which a particular order has existed. Those that reach the top of the chart have survived to the present day. The width of a grey shape shows how many species existed at any given time. The dotted lines indicate possible links between the orders for which there is no direct fossil evidence.

10,000 yrs

Holocene

Marsupials

Anteaters, sloths

Pangolins

Hares, rabbits

Rodents

Elephant shrews

Primates

Colugos

Bats

Insectivores

Pinnipoeds

Carnivores

Whales & dolphins

Odd-toed ungulates

Aardvark

Even-toed ungulates

Elephants

Sea-cows

Geologic time scale

Hyraxes

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Key Idea: An ancestral mammal group underwent adaptive radiation about 80 mya and diversified into all the mammalian groups seen today. Adaptive radiation is diversification among the descendants of a single ancestral group to occupy different niches. Mammals underwent an extensive adaptive radiation following the extinction of the dinosaurs. Most of the modern mammalian groups became established very early on. The

Monotremes

150

Pleistocene

1.8 my

Pliocene

5 my

Miocene

25 my

Oligocene

37 my

A

Eocene

53 my

Paleocene

A

D

D

65 my

Cretaceous

B

134 my

Early mammal Megazostrodon

Jurassic

200 my

C

Triassic

1. In general terms, describe the adaptive radiation that occurred in mammals:

3. Explain what occurred at point B (above):

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2. Name the term that you would use to describe the animal groups at point C (above):

4. Describe one thing that the animal orders labelled D (above) have in common:

5. Identify the two orders that appear to have been most successful in terms of the number of species produced:

6. Explain what has happened to the mammal orders labelled A in the diagram above:

7. Name the geological time period during which there was the most adaptive radiation: WEB

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111 108

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151 Rodent biodiversity

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Rodents make up 40% of mammalian species, making them the most successful of the mammalian groups. Fossils with distinctive rodent features first appeared about 66 million years ago, and during their evolution they have spread to all continents except Antarctica and most islands. They are morphologically generalised and highly adaptable, occupying a wide range of habitats including deserts, forests, and Arctic tundra. Their life histories are highly varied and they exhibit a wide range of adaptations for a range of niches (below). In some cases, distantly related species have occupied the same type of habitat and niche in widely separated regions, e.g. the kangaroo rat in western North America deserts (beaver-like rodents) and the jerboa in African deserts (mouse-like rodents).

Squirrel-like rodents

Porcupine-like rodents

Squirrels are found on many continents. Their lifestyles include tree dwelling, ground dwelling, and gliding forms. Like most rodents they are social, with prairie dogs forming large communities called towns.

Capybaras are South American rodents and the largest of all rodents. They occupy habitats from forests to savannahs. Porcupines are found throughout the Old and New Worlds. Their spines make an almost impenetrable defense against predators. The group also includes guinea pigs, which are popular as pets.

Chipmunk

Guinea pig

s

29

ie

0+

ec

sp

sp

ec

7+

ie

s

30

Porcupine

Squirrel

ec

sp

s

ie

ec

sp

2+

7+

10

am

13

ill l ro d e n t, M a s

n s ch ulz

1,

ie

s

c

tr a

B jo r

ys

An

es

Beaver

Dormouse

Kangaroo rat

Rat

Mouse-like rodents

Beavers are one of the larger types of rodents. They live near rivers, streams and lakes, chewing through small trees to build dams across streams and lodges to live in. Gophers live in burrows, while kangaroo rats are so well adapted to the desert they virtually never need to drink.

Rats and mice are found in virtually every part of the world thanks to their generalist adaptations and human assisted travel. There are at least 100 species of rats and mice alone. The group also includes voles, lemmings, jerboas and dormice.

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Beaver-like rodents

8. Providing examples, discuss why rodent adaptive radiation has been so successful:

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152

112 Divergent Evolution in Ratites of ratites were flying birds living about 80 million years ago. These ancestors also had a primitive palate, but they possessed a keeled breastbone. Flightlessness in itself is not unique to ratites; there are other birds that have lost the power of flight, particularly on remote, predator-free islands. All ratites have powerful legs, and many, such as the emu, can run very quickly.

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Key Idea: The ratites are group of birds descended from a single common ancestor that lost the power of flight very early on in their evolutionary development. Ratites are flightless birds that possess two features that distinguish them from other birds; a flat breastbone (instead of the more usual keeled shape) and a primitive palate (roof to the mouth). Fossil evidence indicates that the ancestors

Elephant bird

Ostrich

Two species, extinct, Madagascar

Struthio camelus, Africa

Cassowary

Emu

Three species, Australia & New Guinea.

Dromaius novaehollandiae, Australia.

Rhea

Two species, South America.

Kiwi

*Tinamous from South America were until recently thought to be related to but not part of the ratite group. New evidence suggests they should be included in ratites.

Five species, New Zealand.

It had long been thought that the geographical distribution of modern day and extinct ratite species could be explained in terms of continental drift. The "rafting hypothesis" suggests that the ancestral ratite population existed at a time when the southern continents of South America, Africa, and Australia (and their major offshore islands) were joined as a single land mass called Gondwana. As the continents moved apart as a result of plate tectonics, the early ratite populations were carried with them. New genetic studies have now cast doubt on this interpretation. Mitochondrial DNA (mtDNA) evidence now suggests kiwis are most related to the extinct elephant bird from Madagascar and slightly less closely related to emus in Australia. However, the ancestor to the kiwi arrived in New Zealand long after New Zealand separated from the rest of Gondwana. Ancestral kiwi must therefore have flown there. Moas are now thought to be closely related to tinamous (South America), which can fly. Ostriches were thought to be closely related to elephant birds but mtDNA now suggests they diverged from the other Mesozoic Cenozoic Era ratites early. The conclusionsEra from these new findings suggest that the ratites evolved from flighted birds that flew between continents and independently evolved flightlessness at least six times. Birds evolved from a saurischian

Ratite phylogeny

Moas diverged from tinamous about 55 million years ago.

Birds evolved from a theropod dinosaur ancestor about 150 million years ago.

Ratites

I

C

Fossil evidence suggests that ratite ancestors possessed a keeled breastbone and an archaic palate (roof of mouth)

E

Ratites diverge from the line to the rest of the birds about 100 million years ago.

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108

H

F

B

Moa 1: Anomalopteryx

Moa

Moa 2: Pachyornis Moa 3: Dinornis

D

A

LINK

K

J

Ratites diverged from other birds between 90 and 70 million years ago.

* Lambert et al. 2004. “Ancient DNA solves sex mystery of moa.” Australasian Science, 25(8), Sept. 2004, pp. 14-16.

All other living birds

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(small theropod) dinosaur ancestor about 150 million years ago (below)

Moa

Eleven species (Lambert et al. 2004*), all extinct, New Zealand.

Tinamou Moa 4: Megalapteryx Little spotted kiwi Elephant bird Great spotted kiwi Rowi kiwi SI brown kiwi Kiwi NI brown kiwi Emu

G

Emu

Cassowary Ostrich

L

Rhea 1 Rhea 2

A

Letters indicate common ancestors

75 mya

50 mya

25 mya

Cassowary Rhea

Ostrich

Other birds

Tinamou (can fly) From Mitchell et al

Present

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1. (a) Describe three physical features distinguishing all ratites (excluding tinamous) from most other birds:

(b) Why should tinamous be included in ratites?

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2. Describe two anatomical changes, common to all ratites (excluding tinamous), which have evolved as a result of flightlessness. For each, describe the selection pressures for the anatomical change:

(a) Anatomical change:

Selection pressure:

(b) Anatomical change:

Selection pressure:

3. (a) Name two other flightless birds that are not ratites:

(b) Why are these other flightless species not considered part of the ratite group?

4. Kiwis are ratites that have remained small. They arrived in New Zealand long after the moa. What part might this late arrival have played in kiwi species remaining small?

5. (a) On the phylogenetic tree opposite, circle the branching marking the common ancestor of moa and kiwi. (b) On the phylogenetic tree opposite, circle the branching marking the common ancestor of emus and kiwi.

(b) Which ratite group is actually the closest related to the ostrich?

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6. (a) Based on the rafting hypothesis which ratite would you expect to be most closely related to ostriches?

7. The diversification of ratites may still be explained in part by continental drift. Use the data on the opposite page to suggest a possible sequence of events for the distribution of ratites:


154

113 The Rate of Evolutionary Change equilibrium, are proposed for the rate at which new species arise (below). It is likely that both operate at different times for different taxa in different situations. There is evidence for both models in the fossil record and in living populations.

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Key Idea: New species may arise gradually through accumulation of differences over a long period of time or they may arise relatively suddenly. Two common models, gradualism and punctuated

Punctuated equilibrium

New species New species

Parent Parentspecies species

New species bud off from the parent species and undergo rapid change, followed by a long period of stability.

Phyletic gradualism

New species New species

New New species species

Parent Parentspecies species

Each species undergoes gradual changes in its genetic makeup and phenotype.

A typical pattern

There is abundant evidence in the fossil record that, instead of gradual change, species stayed much the same for long periods of time (called stasis). These periods were punctuated by short bursts of evolution which produce new species quite rapidly. According to the punctuated equilibrium theory, most of a species’ existence is spent in stasis and little time is spent in active evolutionary change. The stimulus for evolution occurs when a crucial aspect of the environment changes, creating new selection pressures.

A typical pattern

New species diverges from the parent species.

Phyletic gradualism assumes that populations slowly diverge by accumulating adaptive characteristics in response to different selective pressures. If species evolve by gradualism, there should be transitional forms seen in the fossil record, as is seen with the evolution of the horse. Trilobites, an extinct marine arthropod, are another group of animals that have exhibited gradualism. In a study in 1987, a researcher found that there was a gradual change in eight lineages over a period of three million years.

(a) Punctuated equilibrium:

(b) Gradualism:

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1. Suggest the kinds of environments that would support the following paces of evolutionary change:

2. In the fossil record of early human evolution, species tend to appear suddenly, linger for often very extended periods before disappearing suddenly. There are few examples of smooth inter-gradations from one species to the next. Which of the models (punctuated equilibrium or gradualism) best describes the rate of human evolution?

3. Some species, such as sharks, horseshoe crabs, and tuatara, apparently show little evolutionary change over long periods of time (hundreds of millions of years).

(a) What term given to this lack of evolutionary change?

(b) Suggest why such species have apparently changed little over evolutionary time:

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155

114 The Geological History of New Zealand evolution of a unique array of organisms. With the exception of three native bat species (one extinct), no land mammals were present and niches occupied by mammals elsewhere in the world were, in New Zealand, filled by birds and insects. The geologic activity of New Zealand over its history has provided ample opportunities for speciation of these taxa.

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Key Idea: New Zealand's geological history and early isolation from other land masses has played a significant role in the evolution of New Zealand's unique flora and fauna. New Zealand became isolated from other land masses around 65 mya when the land mass that became New Zealand split away from Gondwana (below). The isolation resulted in the

The rise and fall of New Zealand

Present day

New Zealand has had a varied geological history, rising from below the sea, becoming half the size of Australia, and sinking to almost nothing before rising again to form high snow covered mountains. The New Zealand landmass is the highest point of a much greater submerged microcontinent known as Zealandia. The rise and fall of Zealandia allowed the organisms present to colonise new landscapes, before retreating to scattered islands. Large scale changes to the sea level (more than 100 m) during glacials has contributed to this fragmentation, periodically joining and separating the islands.

New Zealand is separated into three main islands and numerous small ones. Geological activity still continues, producing a variety of landscapes including snow fields, high rainfall differences between east and west, and low land plains.

Timeline

2 mya to 0.5 mya

New Zealand is joined to the supercontinent Gondwana. Mammals have not yet diversified, dinosaurs still rule. Birds are evolving. Ancient plants including podocarps spread to ancestral New Zealand.

New Zealand assumes roughly its present shape. Changes in sea level during glacials connect the islands. Kakariki arrive and diversify.

70 mya

5 mya

Plate boundary forms and Tasman sea begins to open. Dinosaurs still predominate and mammals are yet to spread widely. New Zealand is well forested with many available niches. Its most ancient organisms are present including geckos, frogs, tuatara, and snails.

The Kaikoura Orogeny begins, uplifting the Southern Alps, producing the first alpine environment in 50 million years. Many plants and animals move into the vacant niches including cicada, kea, and buttercups.

40 mya

25 mya

Erosion reduces New Zealand to less than half its previous size.

New Zealand land mass has eroded to its smallest size (known as the Oligocene Drowning). Many small islands give opportunities for speciation, e.g. geckos and snails.

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150-100 mya

1. How did each of the following geological events provide an opportunity for speciation:

(a) New Zealand separates from Gondwana:

(b) The Oligocene Drowning:

(c) Kaikoura Orogeny:

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LINK

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156

115 Changes in Landscape and Speciation pressures, accelerating the pace of evolutionary change. New Zealand's fragmentation into islands through sea level rise (~30 mya), cooling climate (from ~10 mya), and increasingly mountainous landscape (from ~5 mya) have been associated with many speciation events and has resulted in great diversity and a large number of endemic species.

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Key Idea: New Zealand's fragmentation as a result of changes in sea level created conditions favouring the divergence of many local species. During New Zealand's geological history, periodic cycles of volcanic activity, fragmentation, and sea level change isolated founder populations and exposed them to new selection

Mainland populations

Warm interglacial periods

Populations on the mainland and the offshore island are separated by the physical barrier of the sea.

Three Kings Is.

Island populations

Aupouri Is.

ra

ipa

Ah

Present-day sea level

Area portrayed below

t

gh

rai

St

Poor Knights Is.

Northland Island

Great Barrier Is.

These isolated populations may undergo evolutionary changes that are different from each other.

Pliocene (~5 to 2.5 mya) and some of the interglacials

ffSea level rose as the climate warmed and the polar ice melted.

Manukau Strait

ffMore islands and archipelagos (island chains) were created.

North Island

ffIslands were isolated by large stretches of water.

ffMany populations underwent gene pool changes as they responded to the specific natural selection pressures of smaller habitats.

ffThis period was important for speciation events in New Zealand.

Glacial periods

Three Kings Is.

Snow and ice fields

Mainland and island populations remix

Sea level drops by 60 metres

Poor Knights Is.

Woody vegetation

The sea bed is exposed for thousands of years and is recolonised by terrestrial organisms.

Ranfurly Is.

Subalpine grassland

ffNew Zealand’s shoreline was 60 m lower than it is today so the total landmass was greater than today.

ffThe majority of the landmass was covered by snowfields or tussock grasslands.

Mernoo Is.

ffThe podocarp forests, which covered most of the North

Steppe loess zone (grassland)

Island in more recent times, were restricted to north of Auckland and along the coastline in some regions

ffThe southern cool-temperate beech forests were

widespread. Large areas of the exposed seabed are thought to have been covered by this forest.

Significance During this phase, the distribution ranges of many species were altered. New climatic conditions altered habitat, in some cases drastically, and generated new selection pressures. There was opportunity for species to increase their distribution to what would later become offshore islands. WEB

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115 116

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Last glacial (20,000-18,000 years ago)

Puysegur Is.

Woody vegetation Grassland

Traps Is.

Tundra zone

Glaciers and snow

The diagram above shows New Zealand during a glacial period with the sea level 60 m below present level, exposing large areas of sea bed which was colonised by vegetation.

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157

Current distribution of Paralissotes genus North Cape

Rudolph89 cc 3.0

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Sea level rises in New Zealand during the Pliocene isolated invertebrate populations on an archipelago and contributed to the emergence of several species from a common ancestor. The stag beetles (genus Paralissotes) are an example of this.

Paralissotes

Cape Maria van Diemen

Paralissotes mangonuiensis

Paralissotes oconnori

Paralissotes planus

Whangarei

Stag beetles

The four species of closely related stag beetles found in the upper North Island are thought to have shared a common ancestor prior to the Pliocene rise in sea level. When the climate warmed and the sea level rose, a chain of islands (an archipelago) was created, isolating parts of the population. Over thousands of years of isolation with different selection pressures, each group developed separate species status. Since the fall in sea level, these populations have been able to remix in many cases, but the gene pool of the species remains intact because reproductive isolating mechanisms have developed. The point of origin for each species can be estimated by comparing their present distribution with that of Pliocene Northland.

Auckland

Paralissotes reticulatus

Zone of overlap (sympatric distribution)

1. How have the following influenced New Zealand's landscape? (a) Interglacial periods:

(b) Glacial periods:

(c) How would the changes described in (a) and (b) lead to speciation in land invertebrates?

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2. (a) Consult the map of the Northland region during the Pliocene and determine what land mass P. planus and P. reticulatus were restricted to during their divergence into separate species:

(b) Describe the likely event that allowed these two species to occupy the same region south of Auckland:

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158

116 Speciation in Giant Land Snails regions (see map below). The snails were once widespread in New Zealand, dispersing into a variety of habitats ranging from alpine grasslands to lowland forests. This diversity of habitats coupled with geographic isolation has resulted in a large amount of speciation. Some isolated populations were trapped on mountain 'islands', cut off from other populations by difficult terrain or expanses of ocean during periods of high sea level.

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Key Idea: There are many species of New Zealand Powelliphanta snails. The diversity has arisen through multiple speciation events in diverse habitats. New Zealand's giant land snail (Powelliphanta species) are large, nocturnal, carnivorous snails. They are a very diverse genus with at least 21 species and 51 subspecies. Today most of the species are found in northwest Nelson and north Westland, but they are also located in other

The geographic distribution of giant land snails in New Zealand

Two other groups of giant land snails known as kauri snails and flax snails are distributed within Northland and a few offshore islands.

DoC-KW

DoC-VV

The map on the right shows the distribution of 10 Powelliphanta species. Note that Ross’ land snail has a split distribution (locations 8 and 10) and is sympatric with Speden’s land snail.

1. Marchant’s land snail 2. Travers’ land snail

3. Hochstetter’s land snail 4. Gillies’ land snail

5. Superb land snail

6. Oparara land snail

Marchant’s land snail, P. marchanti, is only found above 900 m. It is the most widely distributed species (Lake Waikaremoana to Mt Taranaki).

Five subspecies of Hochstetter’s land snail, P. hochstetteri, are confined to high forested peaks around Nelson and the Marlborough Sounds.

1

7. Woodformed land snail 8. Ross’ land snail

1

9. Fiordland land snail

1

10. Ross’ and Speden’s land snail

4

3 5 6 7

3

2 2

2

2

2

MM

The superb land snail, P. superba, is found in forest above 450 m in the Heaphy-Aorere area of Northwest Nelson.

Gillies’ land snail, P. gilliesi aurea, is found over a wide range of altitudes in the Golden Bay area of Northwest Nelson.

9

10

Most current populations are restricted to the southern North Island and the northern South Island, but in past times their distribution extended as far north as Waikato.

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MM

8

1. Describe the geographical factors contributing to the evolution of so many species of giant land snails in New Zealand:

2. (a) Name the type of speciation pattern observed here:

(b) What evidence is there to support your answer?

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116 114 115

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159

A

B

N

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Little Wanganui River

Karamea River

Ra dia nt Ra ng e

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Karamea

North Island

N

ller

ng

Co

ok

St

South Island

ge

Glasgow Ran

Westport

Bu

Ra

Ngakawau River

Hochstetter’s land snail

e

X

tiri

X

Ma

Mokihinui River

Travers’ land snail

ra

it

The North Island and South Island are separated by the Cook Strait. This 20 km stretch of ocean forms an impassable barrier and may only be crossed during periods of low sea level as in past ice ages.

Riv

er

KEY

Woodformed land snail (subsp.) Powelliphanta lignaria lignaria

High country/ alpine

Woodformed land snail (subsp.) Powelliphanta lignaria unicolorata

Lowland

These giant land snails cannot cross water. The Westland region of the South Island has a high rainfall with many rivers and their tributaries dissecting the rugged landscape. These water channels pose impassable barriers for the snails and cause the geological isolation of small pockets of the population. This has had the effect of causing a high degree of subspeciation in this region.

Highland

Hochstetter’s land snail (subsp.) Powelliphanta hochstetteri hochstetteri 300 metres

Gillies land snail Powelliphanta gilliesi

C

Lowland

Some populations of land snail are separated by different ecological requirements. One subspecies of Hochstetter’s land snail are found only above 300 m while most Gillies’ land snails occupy lowland habitats.

3. Describe the principal geographical isolating mechanism for each of the examples (A to C) in the diagram above: (a)

(b)

(c)

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4. Two subspecies of the woodformed land snail, P. lignaria lignaria (which has a strong banding pattern on its shell) and P. lignaria unicolorata (which has few bands), were separated by the Mokihinui River. In 1929, the Murchison earthquake caused a temporary dam on the Mokihinui River. When the flood waters were released, the two subspecies were mixed near the river mouth. Colonies of hybrids now occur on both sides of the river (marked by X on diagram A above).

(a) What effect did the earthquake have on the geographical isolation of these two subspecies?

(b) What is a hybrid?

(c) Predict what the appearance of the hybrids might be like:

(d) Explain what the formation of viable hybrids tells you about the reproductive isolation of these subspecies:

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160

117 Origin of New Zealand Parrots unknown Australian ancestor about 100 mya. The origin of this proto-kaka/kakapo was associated with the break-up of Gondwana and formation of the Tasman Sea, when New Zealand moved away from Australia and became isolated. The kakapo split from this lineage 60-80 mya and is our most ancient parrot. Kaka split from the kea line some 3 mya and an early member migrated to produce the now-extinct Norfolk Island kaka. About 400,000 years ago the North and South Island kaka differentiated.

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Key Idea: The kakapo, kea, and kaka evolved from an ancestor that lived around 80 mya. The rise of the Southern Alps provided new habitat occupied by the ancestor of the kea. Recent mitochondrial DNA (mtDNA) studies at Victoria University confirm the existence in New Zealand of two distinct groups of parrots: kakapo-kaka-kea, and the various kakariki (5 species). This research provides an excellent example of the use of DNA analysis to determine evolutionary relationships. The kakapo-kaka-kea group originated from an

Geological event

kakapo

Speciation event

kea

Norfolk Island kaka (extinct)

North Island kaka

South Island kaka

DoC-RM

Kaka (Nestor meridionalis) has a North Island and a South Island subspecies. They feed on fruit, honeydew, and insects.

Low sea level during glacials. Isolation of the North Island from the South Island by the formation of Cook Straight.

kaka

Australia and New Zealand become separated by the formation of the Tasman Sea about 80 mya.

DoC-RM

Kakapo (Strigops habroptilus) is a ground-dwelling (flightless) night parrot that was once widely distributed throughout Fiordland and Stewart Island. They feed on berry fruit.

Source: E.J. Grant-Mackie (Thames High School) and J.A. Grant-Mackie (Geology Dept, University of Auckland), based on mDNA studies by Prof. Geoff Chambers and Dr Wee Ming Boon (Victoria University, Wellington).

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117 114

Beginning of the break-up of the Gondwana segment containing New Zealand about 100 mya.

Proto-kaka

Protokaka/kakapo

The new alpine environment allows the ecological divergence of the kaka and the kea from the proto-kaka about 3 mya.

New Zealand is well-forested 60-80 mya, allowing the ecological divergence of the proto-kaka and kakapo into tree-dwelling and ground-dwelling types.

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Kea (Nestor notabilis) inhabits mountain regions of the South Island. They feed on fruit and insects, and are also scavengers.

The Southern Alps begin to rise around 5 mya. Formation of the Manawatu Strait splits New Zealand.

Vicariance: kaka splits into the North Island and South Island sub-species about 0.4 mya.

Australian ancestor (unknown)

Vicariance: Unknown Australian ancestor gives rise to the proto-kaka/kakapo group about 100 mya. Vicariance is a term to describe the geographical separation of a population. It has been important to speciation events in New Zealand.

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161

New Zealand

North Is.. kaka

an

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Se

a

Australia

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Tas m

Kaka

Separation from Australia

Australia and New Zealand are separated by the formation of the Tasman Sea 80 mya

Kaka and kakapo

Manawatu Strait

Kea

Kea

.

South Is. kaka

Forest

Tundra

Alpine scrub

Late Miocene Period warmer than today 10 mya

Early Pleistocene Glaciation ~ 2.5 mya

Holocene Warm interglacial today

1. What role did geographical isolation play in the divergence of the proto-kaka/kakapo from its Australian ancestor?

2. (a) Describe the two habitats in which the kaka and kea species evolved:

(b) When did these two different habitats emerge?

(c) How could the kaka and the kea have evolved from an ancestral proto-kaka?

3. Identify the species that became cold-adapted:

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4. Why do the modern kaka and kea species in the South Island not interbreed?

5. It has previously been postulated that the kakapo may be related to the Australian night parrots and/or Australian ground parrots, but this has not been supported by modern DNA studies. Suggest a reason for the similarities (appearance, ground nesting, poor flight) between these Australian parrots and the kakapo:

6. The kakapo is described as our most ancient parrot. Why do they deserve this label?

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162

118 Adaptive Radiation in Wrens different habitats throughout early New Zealand. The existing wren family dates from a time of extensive adaptive radiation 20 mya. They were once found throughout New Zealand, but their distribution is now much more restricted. Although all insectivorous, the living and extinct wrens exploited different habitats and feeding niches Fossils of extinct species can illustrate past land connections. Fossils of the Stephens Is. wren (extinct) have been found in both the North and the South Islands, showing that there was a land connection between these islands in the past. The two species of stoutlegged wren may have undergone allopatric speciation 3-5 mya when changing sea levels separated North and South Islands. Later similar events could also explain the evolution of separate sub-species of bush wrens and rifleman.

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Key Idea: The ancestor of New Zealand wrens underwent an adaptive radiation about 20 mya. Only two living species remain due to habitat loss and predation. The New Zealand wrens have been isolated from their probable ancestral stock in Australia for more than 60 million years. Although they are called wrens because they resemble true wrens, they belong to an ancient suborder with no living close relatives. The endemic family to which they belong includes the rifleman, the rock wren, and the bush wren, as well as a number of extinct species. New Zealand wrens are small, insectivorous, and flightless (or with poor flying ability). The ancestral wren was almost certainly insectivorous since all the descendants are. There may well have been several related species, of which the ancestral wren was one, living in

Curved beak wren

Spent time sucrrying up and down tree trunks, probing in crevices for grubs with its curved beak.

Curved beak wren

Stout legged wren Both species were ground dwelling, searching the ground for insects.

Stout legged wren North Island

South Island

Bush wren (recently extinct)

Stephens Is. wren Lived and foraged in grass and underbrush (ecological equivalent of a field mouse).

Stephens Is. Wren

Lived and foraged in the bush searching for insects in the air and on the ground.

Bush Wren

North Island

South Stewart Island Island

Rock wren

Lives in subalpine areas, feeding among rocks and tussock, and surviving winter under the snow layer.

Rock Wren

Rifleman

Lives and feeds in the bush, picking insects from branches and trunks of trees.

Rifleman

Fiordland Southern North Island Alps

South Island

0

Recent

10,000

Pleistocene

Secondary radiation further divergence into new species and sub-species

Pliocene

Miocene

Oligocene

?

5 million

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Primary radiation the first radiation from a common ancestor (22-18 mya).

Common ancestor of the New Zeland wrens

1.8 million

Extinction phase during land area reduction due to submergence (50-25 mya)

24 million

Years ago

KEY

Species survives to present

Can/could fly

Species is extinct

Flightless

NOTE: On the diagram, the timescale for the emergence of new sub-species, species, and genera is not linear. As a general rule among birds, new sub-species emerge after 0.5-2 million years of separation, new species after 2-10 million years, new genera after 10-20 million years and new orders with 60-80 million years of separation. LINK

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114 115

NOTE: Time scale is not linear

Many thanks to Ewan Grant-Mackie, Thames High School, and Prof. J.A. Grant-Mackie, Geology Dept, Auckland University, who supplied the information for this exercise.

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New Zealand geology and adaptive radiation of New Zealand wrens

New Zealand during the Oligocene 25 – 30 million years ago

New Zealand shoreline Oligocene

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The adaptive radiation of the New Zealand wrens was a consequence of the break up of the New Zealand land mass during the Oligocene period. Earlier species, as yet undiscovered, may also have existed at this time. A this time (25-30 mya), New Zealand was almost completely submerged, and existed only as a chain of small islands, with a land mass only 18% of what it is today. This was the result of rising sea levels and land subsidence over a period of 5 million years. The reduction in size and break-up of the single land mass had a profound effect on the evolution of the wrens, greatly reducing their range of habitats and causing selective extinctions:

163

Present day

The reduction in species diversity When the New Zealand land mass was largely submerged during the Oligocene, some animals would have retreated to islands of high ground, but would have perished as these became submerged. As a result, many species were lost. The reduction in genetic diversity Not only were species lost, but the genetic diversity of remaining populations would have been severely depleted, with few individuals in a species surviving to pass on their genes. This population bottleneck effect occurs when a very small sample of the total species gene pool manages to survive. When the sea levels dropped again, the survivors moved in to occupy newly available niches.

1. Adaptive radiations have occurred on several occasions in the New Zealand wrens:

(a) What is the difference between primary radiation and secondary radiation?

(b) When did the primary radiation occur following the population bottleneck?

(c) When did the secondary radiation occur?

2. The wrens have undergone two periods where extinctions have occurred; an early one more than 25 million years ago, followed by a recent extinction phase.

(a) What event caused the early extinction phase?

(b) What was the most likely cause for the recent extinction phase of some of the wren species?

(a) Rock wren:

(b) Bush wren:

(c) Stephens Island wren:

(d) Curved beak wren:

(e) Rifleman:

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3. Describe the niche of each wren, including reference to the way in which they may have differentiated:

4. Explain how geological events in New Zealand affected the radiation of the wrens:

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119 Evolution in Hebe suggest that they arrived in New Zealand less than 5 mya from an ancestor in Gondwana or migration from South-east Asia. The pattern of current Hebe distribution in the region of Mt. Taranaki indicates that some of the Hebe species found at high altitude may have first colonised the once high slopes of Kaitake and Pouakai from mountains elsewhere in the North Island. These volcanic remnants once had summits much higher than their current summits.

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Key Idea: New Zealand Hebe species show extensive adaptive radiation. Their distribution around Mt Taranaki reflects past colonisations and current rapid speciation. Many of New Zealand’s angiosperm groups show evidence of spectacular adaptive radiations. The Hebe group of plants consists of ~150 species in 5 genera. Most (2/3) of the species are in a single genus, Hebe, which includes about 20 undescribed polyploids. Hebes share a single common ancestor (they are monophyletic). Recent molecular studies

Hebe species in Taranaki

The current high altitude species on Mt. Taranaki may have originated on Pouakai or Kaitake. Some of the hebes on Pouakai have not yet colonised Mt. Taranaki because of its more recent volcanic activity.

Scale leaves on whipcord foliage (greatly enlarged)

Some Hebe species may have migrated to the newly forming Pouakai where they became established. Failure to do so would have led to their extinction on the older cone.

Species that prefer high altitude may have first colonised the slopes of the original volcanic cone of Kaitake.

Original volcanic cone

Hebe tetragona

Mount Taranaki Current summit: 2518 m Cone: 70,000 years old

Pouakai Current summit: 1337m Cone: 250,000 years old

Habitat preference and distrib ution of Taranaki Hebes

Large leaves on foliage

Hebe “egmontiana”

Hebe species

Habitat

Hebe stricta

Mainly lowland, stream-sides

Hebe macrocarpa

Mainly montain forests

Hebe tetragona

Exposed tussock herbfield

Hebe “egmontiana”

Mainly subalpine scrub & shrubland

Hebe odora (erect form)

Mainly red tussockland

Hebe odora (prostrate form)

Exposed tussock herbfield

Hebe venustula

Subalpine shrubland

Kaitake Current summit: 684m Cone: 525,000 years old

Present a the following locations: Mt. Taranaki

Pouakai

Kaitake

The adaptations of the Hebe species reflect their different habitats. Species at lower altitude have larger leaves. High altitude species have scale leaves. Some species have polyploid chromosome numbers, indicating instant speciation and suggesting that the Hebe group is still evolving rapidly.

1. What process has resulted in instant speciation in Hebe species:

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2. How would high altitude species have first colonised the slopes of Kaitake, despite its low (684 m) summit?

3. What aspect of the Hebes in Taranaki indicates that the group has undergone adaptive radiation?

4. What aspect of the Hebes in Taranaki provides evidence that the group is still evolving rapidly?

5. Suggest why Pouakai has a greater number of Hebe species than Mt. Taranaki, even though it has a lower altitude:

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120 What You Know So Far: Patterns in Evolution Evolution in New Zealand

HINT: Give detail of species involved and geographical events relevant to the example.

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you:

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Patterns of evolution

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HINT: Include clear definitions and describe both rates and patterns of change and patterns of change

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REVISE


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121 NCEA Style Question: Patterns in Evolution

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1. Large marine reptiles known as ichthyosaurs were common in ancient New Zealand waters. Their outward appearance is similar to the dolphins that inhabit New Zealand waters today, and they probably behaved in very much the same way. Evidence suggests that at least some species of ichthyosaur gave birth to live young at sea, as dolphins do now.

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Ichthyosaur

Discuss the pattern of evolution illustrated by this example. In your answer you should consider the selection pressures acting on ichthyosaurs and dolphins during their evolution. You may use more paper if required.

Dolphin

2. New Zealand once had at least six species of wren, most of which evolved from a common ancestor between 22 and 18 million years ago. Only two species are living today. This large number of species is related to the break up of the New Zealand land mass during the Oligocene.

Describe the pattern of evolution shown in wrens. Explain how this pattern arises and discuss the factors that could have led to this pattern in New Zealand wrens. You may use more paper if required.

NZ rifleman

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TEST

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122 KEY TERMS AND IDEAS: Patterns of Evolution 1. Test your vocabulary by matching each term to its correct definition, as identified by its preceding letter code. adaptive radiation

The most recent individual from which all organisms in the group are directly descended.

B

A model for the evolution of lineages in which long periods of stasis are interrupted by brief periods of rapid speciation.

C

The geographical separation or fragmentation of a population.

divergent evolution

D

A form of divergent evolution in which there is rapid speciation of one ancestral species to fill many different ecological niches.

phyletic gradualism

E

A model for the evolution of different forms over a long period of time but with only slight changes occurring between successive generations.

punctuated equilibrium

F

Evolutionary process in which a species or related species follow different evolutionary pathways to eventually become less related.

vicariance

G

Evolution in unrelated species occupying similar niches that causes them to arrive at similar structural, physiological and behavioural solutions.

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A

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common ancestor

convergent evolution

2. Distinguish between vicariance and dispersal as important mechanisms in the evolution of species:

3. The diagrams on the right represents two models showing the rate of evolutionary change.

(a) Name the model represented by pattern A: (b) Describe the features of this model:

Pattern A

(c) Name the model represented by pattern B: (d) Describe the features of this model:

Pattern A

(a) Identify the pattern of evolution displayed by these plants:

(b) Describe the environments associated with the adaptations.

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Cactus

Euphorbia

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4. The two plants shown right are unrelated. The left hand image shows a cactus from North America, while the right hand image shows a Euphorbia from Africa. Both these plants live in deserts.

Pattern B

TEST


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123 The Common Ancestry of Life Molecular phylogenetics has enabled scientists to clarify the very earliest origins of eukaryotes and to recognise two prokaryote domains. Powerful evidence for the common ancestry of all life comes from the commonality in the genetic code and from the similarities in the molecular machinery of all cells.

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Key Idea: Key features shared by all life forms support the hypothesis that life on Earth evolved from a common ancestor. Our knowledge of how organisms are related has grown rapidly in recent decades due to new techniques in molecular phylogenetics. Such techniques compare the DNA, RNA, and proteins of organisms to establish evolutionary relationships.

There is a universal genetic code

DNA encodes the genetic instructions of all life. The form of these genetic instructions, called the genetic code, is effectively universal, i.e. the same combination of three DNA bases code for the same amino acid in almost all organisms. The very few exceptions in which there are coding alternatives are restricted to some bacteria and to mitochondrial DNA.

Domain Bacteria

Cyanobacteria

Proteobacteria (many pathogens)

Other bacteria

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Rocky Mountain Laboratories, NIAID, NIH

Hyperthermophillic bacteria

EII

Chloroplasts have a bacterial origin

Bacteria lack a distinct nucleus and cell organelles. Features of the cell wall are unique to bacteria and are not found among archaea or eukaryotes. Typically found in less extreme environments than archaea. WEB

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Cyanobacteria are considered to be the ancestors of chloroplasts. The evidence for this comes from similarities in the ribosomes and membrane organisation, as well as from genomic studies. Chloroplasts were acquired independently of mitochondria, from a different bacterial lineage, but by a similar process.

Mitochondria have a bacterial origin Evidence from mitochondrial gene sequences, ribosomes, and protein synthesis indicate that mitochondria have a prokaryotic origin. Mitochondria were probably symbiotic inclusions in an early eukaryotic ancestor.

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169 1. Identify three features of the metabolic machinery of cells that support a common ancestry of life: (a)

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(b)

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(c)

2. Suggest why scientists believe that mitochondria were acquired before chloroplasts:

Eukarya (the eukaryotes) are characterised by complex cells with organelles and a membrane-bound nucleus. This domain contains four of the kingdoms recognised under a traditional scheme.

Archaea resemble bacteria but membrane and cell wall composition and aspects of metabolism are very different. They live in extreme environments similar to those on primeval Earth.

Domain Eukarya

Animals

Fungi

Plants

Algae

Domain Archaea

Ciliates

RCN

chloroplasts Bacteria that gave rise to

t gave rise to mitochondria Bacteria tha

Eukaryotes have linear chromosomes

Xiangyux (PD)

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Eukaryotic cells all have large linear chromosomes (above) within the cell nucleus. The evolution of linear chromosomes was related to the appearance of mitosis and meiosis.

Eukaryotes have an archaean origin Archaea superficially resemble bacteria but similarities in their molecular machinery (RNA polymerase and ribosome proteins) show that they are more closely related to eukaryotes.

Living systems share the same molecular machinery

Last Universal Common Ancestor (LUCA)

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In all living systems, the genetic machinery consists of selfreplicating DNA molecules. Some DNA is transcribed into RNA, some of which is translated into proteins. The machinery for translation (left) involves proteins and RNA. Ribosomal RNA analysis support a universal common ancestor.


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124 The Evidence for Evolution the changes must be passed on to the next generation (i.e. be inherited). The evidence for evolution comes from many diverse branches of science and includes evidence from both past and present populations. Drawing on evidence from a number of scientific disciplines helps to build a robust explanation for the evolutionary history of taxa.

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Key Idea: Evidence for the fact that populations evolve comes from many fields of science. Recall that evolution is simply the heritable genetic changes occurring in a population over time. There are two important points to take from this definition. The first is that evolution refers to populations, not individuals. The second is that

Comparative anatomy

Geology

Comparative anatomy examines the similarities and differences in the anatomy of different species. Similarities in anatomy (e.g. the bones forming the arms in humans and the wings in birds and bats) indicate descent from a common ancestor.

Geological strata (the layers of rock, soil, and other deposits such as volcanic ash) can be used to determine the relative order of past events and therefore the relative dates of fossils. Fossils in lower strata are older than fossils in higher (newer) strata, unless strata have been disturbed.

DNA comparisons

Cytochrome c

DNA can be used to determine how closely organisms are related to each other. The greater the similarities between the DNA sequences of species, the more closely related the species are.

Protein evidence

Similarities (and differences) between proteins provides evidence for determining shared ancestry. Fewer differences in amino acid sequences reflects closer genetic relatedness.

EVOLUTION

Developmental evidence

Fossils, like this shark's tooth (left) are the remains of longdead organisms. They provide a record of the appearance and extinction of organisms.

The study of developmental processes and the genes that control them gives insight into evolutionary processes. This field of study is called evolutionary developmental biology (evo-devo).

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Fossil record

Chronometric dating

Biogeography

The geographical distribution of living and extinct organisms provides evidence of common ancestry and can be explained by speciation, extinction, and continental drift. The biogeography of islands, e.g the GalĂĄpagos Islands, provides evidence of how species evolve when separated from their ancestral population on the mainland.

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Radiometric dating techniques (such as carbon dating) allow scientists to determine an absolute date for a fossil by dating it or the rocks around it. Absolute dating has been used to assign ages to strata, and construct the geological time scale.

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125 Fossils requires the normal processes of decay to be permanently arrested. This can occur if the organism's remains are isolated from the air or water and decomposing microbes are prevented from breaking them down. Fossils provide a record of the appearance and extinction of organisms, from species to whole taxonomic groups. Once this record is calibrated against a time scale (by using a broad range of dating techniques), it is possible to build up a picture of the evolutionary changes that have taken place.

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Key Idea: Fossils are the remains of long-dead organisms that have escaped decay and have, after many years, become part of the Earth’s crust. A fossil may be the preserved remains of the organism itself, the impression of it in the sediment (a mould), or marks made by it during its lifetime (trace fossils). For fossilisation to occur, rapid burial of the organism is required (usually in waterborne sediment). This is followed by chemical alteration, whereby minerals are added or removed. Fossilisation Fossilisation best occurs when an organism dies in a place where sediment can be laid down relatively quickly. This is often an aquatic environment, e.g. an estuary, but it can be caused by rapid burial, e.g. by a landslide or volcanic ash.

After death, the flesh may rot or be scavenged, but hard materials, usually bones and teeth, are able to remain long enough for burial.

Soft material such as the cartilagineous skeletons of sharks don't fossilise well. Often the only remains are their teeth (above).

After burial, the bones are subjected to pressure. Minerals in the surrounding sediments move into the bones and replace the minerals in them.

Erosion of the sediments exposes the fossils on the surface.

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1. Describe how a fossil forms:

2. Explain why the rapid burial of an organism is important in the formation of fossils:

3. Explain why the fossil record is biased towards marine organisms with hard parts:

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172 Some fossils act as index fossils ffAn index fossil is a fossil that is characteristic of a particular span of geologic

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time or environment. Index fossils help scientists with relative dating (placing rock layers in a relative order to each other), define boundaries in the geologic time scale, and correlate strata from different regions.

ffTrilobites make excellent index fossils because they are easily recognisable,

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abundant in the fossil record, and different families are characteristic of different geographic distributions and different time periods.

ffTrilobites (meaning three lobes) are a fossil group of extinct marine arthropods.

They first appeared in the fossil record near the beginning of the Cambrian (520 mya) and disappeared in the mass extinction at the end of the Permian (250 mya).

ffThey were a very diverse group and underwent several radiations during the

Cambrian, inhabiting a wide range of marine environments and exhibiting diverse life strategies. The wide diversity in their appearance reflects this.

ffThe trilobite fossil record provides evidence of several evolutionary trends in

the different lineages. These included streamlined shape in swimming forms, broadening of the head in filter feeders, improvement in the ability to curl up into a defensive ball, decreased size, and the evolution of spines as defences (below).

Loss of surface detail could have helped with burrowing. A decrease in size allowed exploitation of new microhabitats.

Spines provided defence from attack and stabilisation on loose surfaces.

An enlargement of the head region was probably an adaptation to filter feeding.

Fossilised trilobite

Elongated and streamlined bodies aided swimming in pelagic (open ocean) forms.

4. (a) Explain the importance of index fossils in determining relative time lines:

(b) Why do trilobites make good index fossils?

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5. What fossil evidence do we have that trilobites were a diverse group adapted to many different niches?

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126 Interpreting the Fossil Record geological events). Strata from widespread locations can be correlated because a particular stratum at one location is the same age as the same stratum at a different location. Placing the strata in a sequential (relative) order of past events in a rock profile allows scientists to provide relative dates of past events, but it can not provide an absolute date for an event.

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Key Idea: Fossils provide a record of the appearance and extinction of organisms. The fossil record can be used to establish the relative order of past events. Fossils provide a record of the appearance and disappearance of organisms over time. Rock layers (strata) are arranged in the order of deposition (unless they have been disturbed by

The formation of rock strata

The Earth's landscape has been shaped over a very long time through natural geological processes that continue today. Over time, layers of sedimentary rock, ash, or lava were deposited. Newer layers were deposited on top of older layers so that the oldest layers became buried. Layers are (usually) deposited horizontally and remain so unless they have been disturbed by geological processes such as mountain building or erosion.

These strata have been disturbed (tilted).

Gaps in the fossil record

One of the difficulties with interpreting the fossil record is that it contains gaps. Without a complete record, it can be difficult to establish the evolutionary history of a taxon. There are several reasons for gaps in the fossil record, including: ffOrganisms are only preserved as fossils rarely and many fossils have not been found.

These strata remain in their original horizontal position.

ffFossils are often destroyed or distorted through changes in the preservation environment.

ffSome organisms do not fossilise well. The record is biased towards organisms with hard parts. Profile with sedimentary rocks containing fossils

Rock strata are arranged in the order that they were deposited (unless they have been disturbed by geological events). The most recent layers are near the surface and the oldest are at the bottom. Fossils can be used to establish the sequential (relative) order of past events in a rock profile. Each rock layer (stratum) is unique in terms of the type of rock (sedimentary or volcanic) and the type of fossils it contains.

Ground surface

Youngest sediments

Extinct species The number of extinct species is far greater than the number of species living today.

Fossil types differ in each stratum Fossils found in a given layer of sedimentary rock are generally significantly different to fossils in other layers.

New fossil types mark changes in environment

In the strata at the end of one geological period, it is common to find many new fossils that become dominant in the next.

Each geological period had a different environment from the others. Their boundaries coincided with drastic environmental changes and the appearance of new niches. These produced new selection pressures resulting in new adaptive features in the surviving species, as they responded to the changes.

Recent fossils are found in more recent sediments The more recent the layer of rock, the more resemblance there is between the fossils found in it and living organisms.

Oldest sediments

More primitive fossils are found in older sediments Fossils in older layers tend to have quite generalised forms. In contrast, organisms alive today have specialised forms.

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Rock strata are layered through time

1. Discuss the importance of fossils as a record of evolutionary change over time:

2. Why can gaps in the fossil record make it difficult to determine an evolutionary sequence?

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174 Trilobite fossil Dated at 375 million years

Rock profile at location 1

Fossils are embedded in the different layers of sedimentary rock

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A

Rock profile at location 2

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B

I

C

J

K

D

L

E

M

A distance of 67 km separates these rock formations

F

N

O

G

H

The questions below relate to the diagram above, showing a hypothetical rock profile from two locations separated by a distance of 67 km. There are some differences between the rock layers at the two locations. Apart from layers D and L which are volcanic ash deposits, all other layers comprise sedimentary rock.

3. Assuming there has been no geologic activity (e.g. tilting or folding), state in which rock layer (A-O) you would find:

(a) The youngest rocks at location 1:

(c) The youngest rocks at location 2:

(b) The oldest rocks at location 1:

(d) The oldest rocks at location 2:

4. (a) State which layer at location 1 is of the same age as layer M at location 2:

(b) Explain the reason for your answer above:

5. The rocks in layer H and O are sedimentary rocks. Explain why there are no visible fossils in these layers:

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6. (a) State which layers present at location 1 are missing at location 2:

(b) State which layers present at location 2 are missing at location 1: 7. Using radiometric dating, the trilobite fossil was determined to be approximately 375 million years old. The volcanic rock layer (D) was dated at 270 million years old, while rock layer B was dated at 80 million years old. Give the approximate age range (i.e. greater than, less than, or between given dates) of the rock layers listed below:

(a) Layer A:

(d) Layer G:

(b) Layer C:

(e) Layer L:

(c) Layer E:

(f) Layer O:

8. Suggest why gaps in the fossil record can make it difficult to determine an evolutionary history?

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127 Transitional Fossils fossils include horses, whales, and Archaeopteryx and other non-avian feathered dinosaurs (below). Archaeopteryx was a transitional form between non-avian dinosaurs and birds. Archaeopteryx was crow-sized (50 cm length) and lived about 150 million years ago. It is regarded as the first primitive bird and had a number of birdlike (avian) features, including feathers. However, it also had many non-avian features, which it shared with theropod dinosaurs of the time.

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Key Idea: Transitional fossils show intermediate states between two different, but related, groups. They provide important links in the fossil record Transitional fossils are fossils with a mixture of features found in two different, but related, groups. Transitional fossils provide important links in the fossil record and provide evidence to support how one group may have given rise to the other by evolutionary processes. Important examples of transitional

Non-avian features

Avian features

Forelimb has three functional fingers with grasping claws

Vertebrae are almost flat-faced

Lacks the reductions and fusions present in other birds

Impressions of feathers attached to the forelimb

Breastbone is small and lacks a keel True teeth set in sockets in the jaws

Belly ribs

The hind-limb girdle is typical of dinosaurs, although modified

Incomplete fusion of the lower leg bones

Long, bony tail, shared with other dinosaurs of the time

Impressions of feathers attached to the tail

Suggested reconstruction of Archaeopteryx based on fossil evidence.

(b) Why are transitional fossils important in understanding evolution?

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1. (a) What is a transitional fossil?

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128 The Evolution of Horses of horse phylogeny. It is a complex tree-like lineage with many divergences (below), and a diverse array of often coexisting species. The environmental transition from forest to grasslands drove many of the changes observed in the fossil record. These include reduction in toe number, increased size of cheek teeth, and increasing body size.

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Key Idea: The evolution of the horse is one of the most robust examples of evolution documented in the fossil record. The evolution of the horse from the ancestral Hyracotherium to modern Equus is well documented in the fossil record. The rich fossil record, which includes numerous transitional fossils, has enabled scientists to develop a robust model Equus

0

The cooler climates that prevailed in the Miocene (23 -5 mya) brought about a reduction in forested areas with grasslands becoming more abundant. The change in vegetation resulted in the equids developing more durable teeth to cope with the harsher diet. Over time the equid molar became longer and squarer with a hard cement-like covering to enable them to grind the grasses which became their primary diet.

5

10

1.6 m

Enamel

15

Dentine

Merychippus

Cement

20

Millions of years ago

Hyracotherium molar

25

1.25 m

30

Mesohippus

35

40

0.6 m

45

50

Hyracotherium (Eohippus)

55

0.4 m

Equus molar

The equids also became taller and faster to enable them to view and escape their predators. This is evident in their overall increase in size and the elongation of their limbs. The reduction in the number of toes from four to one (left) also enabled them to run faster and more efficiently.

The majority of equid evolution took place in North America, although now extinct species did migrate to other areas of the globe at various times. During the late Pliocene (2.6 mya) Equus spread into the Old World and diversified into several species including the modern zebra of Africa and the true horse, Equus caballus. The horse became extinct in the Americas about 11,000 years ago, and was reintroduced in the 16th century by Spanish explorers.

(a) Change in tooth structure:

(b) Limb length:

(c) Reduction in number of toes:

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1. How did the environmental change, from forest to grassland, influence the following aspects of equid evolution:

2. Why does the equid fossil record provide a good example of the evolutionary process?

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129 The Evolution of Whales record of whales includes many transitional forms, which has enabled scientists to develop an excellent model of whale evolution. The evolution of the whales (below) shows a gradual accumulation of adaptive features that have equipped them for life in the open ocean.

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Key Idea: The evolution of whales is well documented in the fossil record, with many transitional forms recording the shift from a terrestrial to an aquatic life. The evolution of modern whales from an ancestral land mammal is well documented in the fossil record. The fossil

Baleen whales: Toothless whales, which have a comb-like structure (baleen) in the jaw. Baleen is composed of the protein keratin and is used to filter food from the water. Examples: blue whale, humpback whale.

Orca

Robert Pittman - NOAA

Modern whales are categorised into two broad suborders based on the presence or absence of teeth. Toothed whales: These have full sets of teeth throughout their lives. Examples: sperm whale and orca.

Humpback whale

50 mya Pakicetus

Pakicetus was a transitional species between carnivorous land mammals and the earliest true whales. It was mainly land dwelling, but foraged for food in water. It had four, long limbs. Its eyes were near the top of the head and its nostrils were at the end of the snout. It had external ears, but they showed features of both terrestrial mammals and fully aquatic mammals.

45 mya Rhodocetus

Rhodocetus was mainly aquatic (water living). It had adaptations for swimming, including shorter legs and a shorter tail. Its eyes had moved to the side of the skull, and the nostrils were located further up the skull. The ear showed specialisations for hearing in water.

Legs became shorter

40 mya Dorudon

Dorudon was fully aquatic. Its adaptations for swimming included a long, streamlined body, a broad powerful muscular tail, the development of flippers and webbing. It had very small hind limbs (not attached to the spine) which would no longer bear weight on land.

Hind limbs became detached from spine

Redrawn from de Muizon Nature 2001 413 pp259-260

The hind limbs became fully internal and vestigial. Studies of modern whales show that limb development begins, but is arrested at the limb bud stage. The nostrils became modified as blowholes. This recent ancestor to modern whales diverged into two groups (toothed and baleen) about 36 million years ago. Baleen whales have teeth in their early fetal stage, but lose them before birth.

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Hind limbs are internal and vestigial (have lost their original function).

Balaena (recent whale ancestor)

1. Why does the whale fossil record provide a good example of the evolutionary process?

2. Briefly describe the adaptations of whales for swimming that evolved over time:

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130 Biogeographical Evidence of species. As described in this activity, island biogeography demonstrates that species on a given island may more closely resemble species on a nearby mainland, rather than species on a distant island with a similar environment.

Galápagos and Cape Verde islands

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Key Idea: Biogeography provides evidence for how the evolution of species is influenced by isolation, continental influences, geological processes, and dispersal ability. Biogeography is the study of the geographical distribution

Galapagos Is

Biologists did not fully appreciate the uniqueness and diversity of tropical island biota until explorers began to bring back samples of flora and fauna from their expeditions in the 19th century. The Galápagos Islands, the oldest of which arose 3-4 million years ago, had species similar to but distinct from those on the South American mainland. Similarly, in the Cape Verde Islands, species had close relatives on the West Africa mainland. This suggested to biologists that ancestral forms found their way from the mainland to the islands where they then underwent evolutionary changes.

South America

900 km

Cape Verde Is

Western Africa

450 km

Pacific Ocean

South Atlantic Ocean

South America

4500 km

Atlantic Ocean

Tristan da Cunha species

Tristan da Cunha

Africa

3000 km

Tristan da Cunha

The island of Tristan da Cunha in the South Atlantic Ocean is a great distance from any other land mass. Even though it is closer to Africa, there are more species closely related to South American species found there (see table on right). This is probably due to the predominant westerly trade winds from the direction of South America. The flowering plants of universal origin are found in both Africa and South America and could have been introduced from either land mass.

South American origin 7 Flowering plants 5 Ferns 30 Liverworts African origin 2 Flowering plants 2 Ferns 5 Liverworts

Universal origin 19 Flowering plants

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1. The Galápagos and the Cape Verde Islands are both tropical islands close to the equator, yet their biotas are quite different. Explain why this is the case:

2. Explain why the majority of the plant species found on Tristan da Cunha originated from South America, despite its greater distance from the island:

3. Using an example, describe how biogeography provides support for evolutionary mechanisms:

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131 Ocean Island Colonisers be marine in habit or able to survive long periods at sea or in the air. Plants also have limited capacity to reach distant islands. Only some have seeds and fruit that are salt water tolerant. Many plants are transferred to the islands by wind or migrating birds. The biota of the Galápagos islands provide a good example of the result of such a colonisation event.

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Key Idea: The biodiversity of oceanic islands often depends on the distance to the mainland and the ability of plants and animals to survive dispersal. Oceanic islands have a unique biota because only certain groups of plants and animals tend to colonise them. The animals that successfully colonise oceanic islands have to

Land mammals: Few non-flying mammals colonise islands, unless these are very close to the mainland. Mammals have a higher metabolism, need more food and water than reptiles, and cannot sustain themselves on long sea journeys.

Small birds, bats, and insects: These animals are blown to islands by accident. They must adapt to life there or perish.

Blown by strong winds

Plants: Plants have limited capacity to reach distant islands. Only some have fruits and seeds that are salt tolerant. Many plants are transported to islands by wind or birds.

Reptiles: Reptiles probably reach distant islands by floating in driftwood or on mats of floating vegetation. A low metabolic rate enables them to survive the long periods without food and water.

Active flight

Oceanic island

Deep ocean

Amphibians: Cannot live away from fresh water. They seldom reach offshore islands unless that island is a continental remnant.

The flightless cormorant (above) is one of a number of bird species that lost the power of flight after becoming an island resident. Giant tortoises, such as the 11 subspecies remaining on the Galápagos today (centre) were, until relatively recently, characteristic of many islands in the Indian Ocean including the Seychelles archipelago, Reunion,

Swimming

Planktonic crustacean larvae

Sea mammals: Seals and sea lions have little difficulty in reaching islands, but they return to the sea after the breeding season and do not colonise the interior. Crustaceans: Larval stages drift to islands. Crabs often evolve novel forms on islands. Many are restricted to shoreline areas. Some crabs, such as coconut crabs, have adapted to an island niche.

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Rafting on drifting vegetation

Seabirds: Seabirds fly to and from islands with relative ease. They may become adapted to life on land, as the flightless cormorant has done in the Galápagos. Others, like the frigate bird, may treat the island as a stopping place.

Mauritius, Farquhar, and Diego Rodriguez. These were almost completely exterminated by early Western sailors, although a small population remains on the island of Aldabra. Another feature of oceanic islands is the adaptive radiation of colonising species into different specialist forms. The three species of Galápagos iguana almost certainly arose,

through speciation, from a hardy traveller from the South American mainland. The marine iguana (above) feeds on shoreline seaweeds and is an adept swimmer. The two species of land iguana (not pictured) feed on cacti, which are numerous. One of these (the pink iguana) was identified as a separate species only in 2009.

1. Describe one feature typical of an oceanic island coloniser and explain its significance:

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A relatively recent (2005) revision of the phylogeny of the finches is shown right. It places the sharp beaked finch more distant from the other ground finches with which it was previously grouped (all are currently Geospiza). A 2015 revision based on whole genome sequencing has split the sharp beaked finches still further into three distinct groups and has suggested a reclassification. The diagram below shows the islands on which the birds are found and the age of the islands in millions of years (in brackets).

The five species of tree finches are largely arboreal (tree dwelling). Their sharp beaks are well suited to grasping insects which form the most of their diet. One species has demonstrated tool use in extracting insects.

Darwin (~0.7)

Wolf (1.0)

The Cocos Island finch is the only one of Darwin's finches to be found outside the Galápagos. DNA analysis shows it is related to the warbler finches. The ancestral finch therefore colonised the Galápagos before colonising Cocos Island.

On Wolf Island, the sharp beaked ground finch has become a specialist blood feeder. Recent genomic analysis has suggested a classification of this species.

Cocos Is

800 km

Galápagos Is. 900 km

Pinta (0.8)

N

Tiasis bicolour (mainland relative)

Warbler finches

Cocos Island finch

Sharp beaked ground finch

Vegetarian finch

Tree finches

Other ground finches

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The Galápagos Islands, off the west coast of Ecuador, consist of 16 main islands and six smaller islands. They are home to 14 species of finches, each of which has evolved from a single species of grassquit, which arrived from Ecuador. A fifteenth species inhabits Cocos Island. After colonising the islands, the grassquits diversified in response to the availability of unexploited feeding niches. This adaptive radiation is most evident in the beaks of the different species, which are adapted for different purposes, including crushing seeds, pecking wood, or probing cactus flowers.

Cactus ground finches

180

South America

Pacific Ocean

Marchena (0.7)

Genovesa (0.3)

Equator

The cactus ground finches (left) have evolved probing beaks to extract seeds and insects from cacti.

Santiago Is. (0.8)

Fernandina (0.7)

Santa Cruz (1.1)

Santa Fé (2.7)

Isabela Is (0.5)

San Cristóbal (2.4)

Ground finches, genus Geospiza (left) have crushing type beaks for seed eating. Three species differ mainly in body size and in the size of their beaks. The other three species have longer beaks and supplement their seed diet with cactus flowers and pulp (the cactus finches) or the eggs and blood of other birds and reptile ticks (the sharp-beaked ground finch).

Española Is. (3.2)

The beak of the warbler finch is the thinnest of the Galápagos finches. It uses it to spear insects and probe flowers for nectar. It is also the most widespread species, found throughout the archipelago.

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Floreana (~1.0)

2. How do we know the finches colonised Cocos Island after colonising the Galápagos Islands?

3. Is there are pattern to how the islands were colonised by the birds? Explain:

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132 Continental Drift and Evolution major crustal plates are driven by a geological process known as plate tectonics. Some continents are drifting apart while others are moving together. Many lines of evidence show that the modern continents were once joined together as ‘supercontinents’. One supercontinent, Gondwana, was made up of the southern continents some 200 mya.

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Key Idea: Fossils of related organisms found on separated continents can be explained by continental drift. Continental drift (the movement of the Earth's continents relative to each other) is a measurable phenomenon; it has happened in the past and continues today. Movements of up to 2-11 cm a year have been recorded between continents using laser technology. The movements of the Earth’s 12 Greenland

Europe

North America

Asia

Africa

India

South America

New Guinea

New Caledonia

Madagascar

Australia

Antarctica

This diagram shows some of the data collected that are used as evidence to indicate how the modern continents once fitted together.

New Zealand

Key

Glossopteris is a hardy plant that grew adjacent to the glacial ice sheets of Gondwana some 350-230 million years ago

Direction of ice sheet movement 350-230 million years ago

Lystrosaurus is a primitive therapsid (mammal-like) reptile 1 m long, that was widely distributed throughout the southern continents about 240 million years ago.

Old Precambrian rocks (older than 650 mya)

Geomagnetic pole direction 150 million years ago

Precambrian basement rocks (650-570 mya)

Distribution of Lystrosaurus

Distribution of Glossopteris

Early Palaeozoic Late PalaeozoicLate Mesozoic folding (570Early Mesozoic folding folding (160350 mya) (350-160 mya) 70 mya)

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1. Name the modern landmasses (continents and large islands) that made up the supercontinent of Gondwana:

2. Cut out the southern continents on page 183 and arrange them to recreate the supercontinent of Gondwana. Take care to cut the shapes out close to the coastlines. When arranging them into the space showing the outline of Gondwana on the following page, take into account the following information: (a) The location of ancient rocks and periods of mountain folding during different geological ages. (b) The direction of ancient ice sheet movements. (c) The geomagnetic orientation of old rocks (the way that magnetic crystals are lined up in ancient rock gives an indication of the direction the magnetic pole was at the time the rock was formed). (d) The distribution of fossils of ancient species such as Lystrosaurus and Glossopteris. 3. 4.

Once you have positioned the modern continents into the pattern of the supercontinent, mark on the diagram: (a) The likely position of the South Pole 350-230 million years ago (as indicated by the movement of the ice sheets). (b) The likely position of the geomagnetic South Pole 150 million years ago (as indicated by ancient geomagnetism). State what general deduction you can make about the position of the polar regions with respect to land masses:

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Gondwana supercontinent coastline about 250-150 million years ago

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5. Fossils of Lystrosaurus are known from Antarctica, South Africa, India and Western China. With the modern continents in their present position, Lystrosaurus could have walked across dry land to get to China, Africa and India. It was not possible for it to walk to Antarctica, however. Explain the distribution of this ancient species in terms of continental drift:

6. The southern beech (Nothofagus) is found only in the southern hemisphere, in such places as New Caledonia, New Guinea, eastern Australia (including Tasmania), New Zealand, and southern South America. Fossils of southern beech trees have also been found in Antarctica. They have never been distributed in South Africa or India. The seeds of the southern beech trees are not readily dispersed by the wind and are rapidly killed by exposure to salt water. (a) Suggest a reason why Nothofagus is not found in Africa or India:

(b) Use a coloured pen to indicate the distribution of Nothofagus on the current world map (on the previous page) and on your completed map of Gondwana above.

(c) State how the arrangement of the continents into Gondwana explains this distribution pattern:

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7. The Atlantic Ocean is currently opening up at the rate of 2 cm per year. At this rate in the past, calculate how long it would have taken to reach its current extent, with the distance from Africa to South America being 2300 km (assume the rate of spreading has been constant):

8. Explain how continental drift provides evidence to support for evolutionary mechanisms:

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New Zealand Australia

New Guinea

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North America

South America

Greenland

Antarctica

Africa

Europe

Madagascar

India

Asia

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183

Cut out the continental land masses that make up the supercontinent of Gondwana and stick them into the space on the previous page

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This page has been deliberately left blank

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185

133 Homologous Structures land vertebrates were amphibians with a pentadactyl limb structure (a limb with five fingers or toes). All vertebrates that descended from these early amphibians have limbs with this same basic pentadactyl pattern. They also illustrate the phenomenon known as adaptive radiation, since the basic limb plan has been adapted to meet the requirements of different niches.

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Key Idea: Homologous structures (homologies) are structural similarities present as a result of common ancestry. The common structural components have been adapted to different purposes in different taxa. The bones of the forelimb of air-breathing vertebrates are composed of similar bones arranged in a comparable pattern. This is indicative of common ancestry. The early

Generalised pentadactyl limb

Specialisations of pentadactyl limbs

The forelimbs and hind limbs have the same arrangement of bones but they have different names. In many cases bones in different parts of the limb have been highly modified to give it a specialised locomotory function.

Forelimb

Hind limb

Humerus (upper arm)

Mole forelimb

Bird wing

Femur (thigh)

Dog front leg

Fibula Tibia

Bat wing

Radius Ulna

Carpals (wrist)

Tarsals (ankle)

Metacarpals (palm)

Metatarsals (sole)

Phalanges (fingers)

Phalanges (toes)

Seal flipper

Human arm

1. Colour code the bones of the generalised pentadactyl limb (above, left) to identify each group of bones. Using the same colour key, colour the comparative bones of the specialised forelimbs (above, right). 2. Briefly describe the purpose of the major anatomical change that has taken place in each of the limb examples above:

(a) Bird wing: (b) Human arm:

(c) Seal flipper:

(d) Dog front leg:

(e) Mole forelimb:

(f) Bat wing:

Highly modified for flight. Forelimb is shaped for aerodynamic lift and feather attachment.

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3. Explain how homology in the pentadactyl limb is evidence for adaptive radiation:

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186

134 Vestigial Structures remain unchanged through a lineage. Their presence can be used to detect common ancestry. Vestigial structures are often homologous to organs that still have a function in other species. For example, the human tail bone (coccyx) has lost its original function (balance and mobility) and is homologous to the fully functioning tail in many other primates.

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Key Idea: The persistence of vestigial structures provides evidence for common ancestry. Vestigial structures are anatomical features that have been retained through a species' evolution but have lost their ancestral function. Having no obvious function, vestigial structures are no longer subject to natural selection and

1.8 m long

Pakicetus (early Eocene). A carnivorous, four limbed, early Eocene whale ancestor. It was still partly terrestrial and not fully adapted for aquatic life. Vestigial organs are common in nature. The vestigial hind limbs of modern whales (right) provide anatomical evidence for their evolution from a carnivorous, four footed, terrestrial ancestor. The oldest known whale, Pakicetus, from the early Eocene (~54 mya) still had four limbs. By the late Eocene (~40 mya), whales were fully marine and had lost almost all traces of their former terrestrial life.

Ancestors of modern whales

2.5 m long

20-25 m long

Protocetus (mid Eocene). Much more whale-like than Pakicetus. The hind limbs were greatly reduced and although they still protruded from the body (arrowed), they were useless for swimming.

Basilosaurus (late Eocene). A very large ancestor of modern whales. The hind limbs contained all the leg bones, but were vestigial and located entirely within the main body, leaving a tissue flap on the surface (arrowed).

Femur

Pelvis

Vestigial hind limb

Forelimb

Modern right whale up to 20 m

Vestigial organs in birds and reptiles

RM-DoC

In all snakes (far left), one lobe of the lung is vestigial (there is not sufficient room in the narrow body cavity for it). In some snakes there are also vestiges of the pelvic girdle and hind limbs of their walking ancestors. Like all ratites, kiwis (left) are flightless. However, more than in other ratites, the wings of kiwis are reduced to tiny vestiges. Kiwis evolved in the absence of predators to a totally ground dwelling existence.

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1. In terms of natural selection explain how structures, that were once useful to an organism, could become vestigial:

2. Suggest why a vestigial structure, once it has been reduced to a certain size, may not disappear altogether:

3. Whale evolution shows the presence of transitional forms (fossils that are intermediate between modern forms and very early ancestors). Suggest how vestigial structures indicate the common ancestry of these forms:

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187

135 Homologous Proteins ancestry) could be studied at the molecular level as well and the results compared to phylogenies established using other methods. Protein sequencing provides an excellent tool for establishing homologies. A protein has a specific number of amino acids arranged in a specific order. Any differences in the sequence reflect changes in the DNA sequence. Commonly studied proteins include blood proteins, such as haemoglobin, and the respiratory protein cytochrome c.

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Key Idea: Proteins are the product of gene expression, so an analysis of the differences between the same protein in different taxa gives an indication of species relatedness. Traditionally, phylogenies were based largely on anatomical traits, and biologists attempted to determine the relationships between taxa based on similarity or by tracing the appearance of key characteristics. With the advent of new molecular techniques, homologies (similarities arising from shared

Haemoglobin homology Human – chimpanzee 0

Chicken 45

Horse 25

Gibbon 2

Rhesus monkey 8

Gorilla 1

Mouse 27

Dog 15

Frog 67

Kangaroo 38

Increasing difference in amino acid sequence

Primates

Placental mammals

Marsupial

Non-mammalian vertebrates

Haemoglobin is the oxygen-transporting blood protein found in most vertebrates. The beta chain haemoglobin sequences from different organisms can be compared to determine evolutionary relationships.

As genetic relatedness decreases, the number of amino acid differences between the haemoglobin beta chains of different vertebrates increases (above). For example, there are no amino acid differences between humans and chimpanzees, indicating they recently shared a common ancestor. Humans and frogs have 67 amino acid differences, indicating they had a common ancestor a very long time ago.

Highly conserved proteins

The Pax-6 protein provides evidence for evolution

Some proteins are common in many different species. These proteins are called highly conserved proteins, meaning they change (mutate) very little over time. This is because they have critical roles in the organism (e.g. in cellular respiration) and mutations are likely to be lethal.

ffThe Pax-6 gene belongs to a family of master genes that regulate the formation of a number of organs, including the eye, during embryonic development.

ffThe Pax-6 gene produces the Pax-6 protein, which acts

Evidence indicates that highly conserved proteins are homologous and have been derived from a common ancestor. Because they are highly conserved, changes in the amino acid sequence are likely to represent major divergences between groups during the course of evolution.

as a transcription factor to control the expression of other genes.

ffScientists know the role of Pax-6 in eye development

because they created a knockout model in mice where the Pax-6 gene is not expressed. The knockout model is eyeless or has very underdeveloped eyes.

ffThe Pax-6 gene is so highly conserved that the gene

ffThis suggests the Pax-6 proteins are homologous, and

Emw

the gene has been inherited from a common ancestor.

An experiment inserted mouse Pax-6 gene into fly DNA and turned it on in a fly's legs. The fly developed morphologically normal eyes on its legs!

Histones (right) are a family of proteins that associate with DNA and organise it so that it can fit inside the cell nucleus.

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from one species can be inserted into another species, and still produce a normal eye.

Cytochrome C (left) is a respiratory protein located in the electron transport chain in mitochondria.

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Using immunology to determine phylogeny Precipitate forms

Human

Gorilla

Baboon

Lemur

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The immune system of one species will recognise the blood proteins of another species as foreign and form antibodies against them. This property can be used to determine the extent of relatedness between species. Blood proteins, such as albumins, are used to prepare antiserum in rabbits, a distantly related species. The antiserum contains antibodies against the test blood proteins (e.g. human) and will react to those proteins in any blood sample they are mixed with. The extent of the reaction indicates how similar the proteins are; the greater the reaction, the more similar the proteins. This principle is illustrated (right) for antiserum produced to human blood and its reaction with the blood of other primates and a rat.

30

Millions of years ago 20 10

Rat

Decreasing recognition of the antibodies against human blood proteins

0

North American tree frogs

European tree frogs

Cricket frog Chorus frogs

Australian tree frog

60

50

40

30

20

10

0

Immunological distance

The relationships among tree frogs have been established by immunological studies based on blood proteins such as immunoglobulins and albumins. The immunological distance is a measure of the number of amino acid substitutions between two groups. This, in turn, has been calibrated to provide a time scale showing when the various related groups diverged.

1. Compare the differences in the haemoglobin sequence of humans, rhesus monkeys, and horses. What do these tell you about the relative relatedness of these organisms?

2. (a) What is a highly conserved protein?

(b) What type of proteins tend to be highly conserved?

(c) Why are the proteins named in (b) highly conserved?

(d) Why are highly conserved proteins good for constructing phylogenies?

3. (a) Describe the role of the Pax-6 gene:

(b) What evidence is there that the Pax-6 protein is highly conserved?

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136 The Molecular Clock Hypothesis species last shared a common ancestor and can be used to construct a phylogenetic tree. The molecular clock for each species, and each protein, may run at different rates, so molecular clock data is calibrated with other evidence (e.g. morphological) to confirm phylogeny. Molecular clock calculations are carried out on DNA or amino acid sequences.

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Key Idea: The molecular clock hypothesis proposes that mutations occur at a steady rate and that changes in DNA sequences between species can determine phylogeny. The molecular clock hypothesis states that mutations occur at a relatively constant rate for any given gene. The genetic difference between any two species can indicate when two

In a theoretical example, the DNA sequence for a gene in two species (A & B, right) alive today differs by four bases. The mutation rate for the gene is approximately one base per 25 million years. Based on this rate, it can be determined that the common ancestor for these two species lived 50 mya.

Time 0

+ 25 million years

+ 50 million years

mutation 1 occurred

mutation 2 occurred

CAATTGATCG

CAATCGATCG

(A)

CAATTTATCT

CAATTTATTT

(B)

Common ancestor

CAATTTATCG

Cytochrome c and the molecular clock theory

Human

1

2

3

4

5

6

7

8

9

Gly

Asp

Val

Glu

Lys

Gly

Lys

Lys

Ile

10

Phe Ile

Pig

Chicken

Ile

Dogfish

Drosophila

<<

Wheat

<<

Asn

Pro

Asp

Yeast

<<

Ser

Ala

Lys

Ala

Thr

12

13

14

15

16

17

18

19

20

21

22

Met

Lys

Cys

Ser

Gln

Cys

His

Thr

Val

Glu

Lys

Val

Gln

Ala

Val

Val

Gln

Ala

Val

Val

Gln

Ala

Asn

Leu

Val

Gln

Arg

Ala

Ala

Lys

Thr

Arg

Ala

Lys

Thr

Arg

Glu

Ala

Ala

11

Leu

Asp

Ala

Leu

This table shows the N-terminal 22 amino acid residues of human cytochrome c, with corresponding sequences from other organisms aligned beneath. Sequences are aligned to give the most position matches. A shaded square indicates no change. In every case, the cytochrome's heme group is attached to the Cys-14 and Cys-17. In Drosophila, wheat, and yeast, arrows indicate that several amino acids precede the sequence shown. Human Monkey Dog

The sequence homology of cytochrome c (right), a respiratory protein, has been used to construct a phylogenetic tree for some species. Overall, the phylogeny aligns well to other evolutionary data, although the tree indicates that primates branched off before the marsupials diverged from other placental mammals, which is incorrect based on other evidence. Highly conserved proteins, such as cytochrome c, change very little over time and between species because they carry out important roles and if they changed too much they may no longer function properly.

Horse Donkey

Pig Kangaroo Rabbit Pigeon

Ancestral

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Duck Chicken Turtle Rattlesnake Tuna Screwworm fly

Samia cynthis (moth) Neurospora crassa (mold) Saccharomyces (bakerâ&#x20AC;&#x2122;s yeast) Candida krusei (yeast)

organism

30

25

20

15

10

Average amino acid substitutions

1. Describe a limitation of using molecular clocks to establish phylogeny:

5

0

2. For cytochrome c, suggest why amino acids 14 and 17 are unchanged in all the organisms shown in the table:

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137 Homologous DNA Sequences the DNA is the same and cannot provide specific information about what the similarities or differences are. Although it has largely been replaced by DNA sequence analysis, DNA hybridisation is still used in microbial studies and has been used to determine the date of human divergence from apes, which has been estimated at 10 and 5 million years ago.

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Key Idea: DNA hybridisation compares DNA similarity between species and can be used to measure relatedness. DNA hybridisation is a technique used to quantify the DNA similarity between species. More closely related species have fewer genetic differences than more distantly related species. The method provides information only about how much of

DNA hybridisation technique

1. DNA from the two species to be compared is extracted, purified and cut into short fragments.

1. How can DNA hybridisation give a measure of genetic relatedness between species?

2. The mixture is heated so the DNA separates. The DNA from the two species is mixed together. 3. As it cools, bonds form between compatible nucleotides. Hybrid double-stranded DNA forms.

4. If species share low similarity, the hybrid DNA will have few bonds (and the strands will be weakly held together). The number of bonds (and therefore the strength of the hybrid DNA) increases with increasing similarity.

5. The similarity is measured by heating the hybrid DNA to force it to form single strands. The greater the similarity, the more heat that is required to break the hybrid DNA apart.

2. Why do the double strands of DNA break when they are heated?

3. What is responsible for the hybridisation between the DNA strands?

Human DNA

Chimpanzee DNA

4. The graph below shows the results of a DNA hybridisation between humans and other primates.

Fragments of double stranded DNA held together by hydrogen bonds.

Similarity of human DNA to that of other primates

0

20

DNA similarity (%) 40 60

80

Human

Cool the samples

Hybrid DNA

97.6%

Gibbon

94.7%

Rhesus monkey

91.1%

Vervet monkey

90.5%

Capuchin monkey Galago

84.2%

58.0%

(a) Which primate is most closely related to humans?

(b) Which primate is most distantly related to humans?

5. Hybrid DNA from species A and B comes apart at a lower temperature that of species A and C. Which species is A most closely related to? These bases match WEB

KNOW

100%

Chimpanzee

No Cla t fo ssr r o Us om e

Single-stranded DNA from the two species is mixed

Primate species

Heat the DNA samples. Heat disrupts the hydrogen bonding so the strands separate.

100

137

These bases do not match

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191

138 Developmental Evidence for Evolution the appearance of a growing embryo. Today, developmental biology focuses on the genetic control of development and its role in producing the large differences we see in the adult appearance of different species. Differences in gene expression during development are behind these differences.

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Key Idea: Similarities in the development of embryos, including the genetic control of that development, provides strong evidence for evolution. Developmental biology studies the processes by which organisms grow and develop. In the past, it was restricted to

60

Developmental biology

Like humans, mice have digits that become fully separated by interdigital apoptosis during development. In bat forelimbs, this controlled destruction of the tissue between the forelimb digits is inhibited. The developmental program is the result of different patterns of expression of the same genes in the two types of embryos.

20

Mouse

Chicken

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Carnegie stage of embryonic development Stage 14 Limb buds

IV

III

Stage 17 Digits form

Stage 23 Digits separate

Apoptosis suppressed by expression of an inhibitory growth factor V

II

I

Bat wings are highly specialised structures with unique features, such as elongated wrist and fingers (I-V) and membranous wing surfaces. The forelimb structures of bats and mice are homologous, but how the limb looks and works is quite different.

Rhesus monkey

30

0

As we have seen, homology (e.g. in limb structure) is evidence of shared ancestry. How do these homologous structures become so different in appearance? The answer lies in the way the same genes are regulated during development.

Human

40

10

Limb homology and the control of development

All vertebrate limbs form as buds at the same stage of development. At first, the limbs resemble paddles, but apoptosis (programmed cell death) of the tissue between the developing bones separates the digits to form fingers and toes.

50

Days

During development, vertebrate embryos pass through the same stages, in the same sequence, regardless of the total time period of development. This similarity is strong evidence of their shared ancestry. The stage of embryonic development is identified using a standardised system based on the development of structures, not by size or the number of days of development. The Carnegie stages (right) cover the first 60 days of development.

Increased expression of a bone growth regulator elongates digits.

IV III

I II

No Cla t fo ssr r o Us om e

V

1. Describe a feature of vertebrate embryonic development that supports evolution from a common ancestor:

2. Explain how different specialised limb structures can arise from a basic pentadactyl structure:

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LINK

WEB

133 138

KNOW


192

139 Evolution of Novel Forms structure, i.e. the body is made up of repeating units. These are more obvious in taxa where the repeating 'modules' have been less modified, e.g. centipedes. In arthropods, modification of individual segments through duplication and modification of genes has seen the evolution of insects, arachnids, and crustaceans. For example, a gene involved in the development of appendages in arthropods can be duplicated and the duplicate gene modified. This produces a set of modifications to some appendages, enabling a new set of functions without having to modify all other the appendages (below).

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Key Idea: The varied appendages of arthropods (and some other animals) can be linked to the duplication and modification of genes and their expression. Evolutionary developmental biology (or evo-devo) is a relatively new area in evolutionary biology that examines how modifications in developmental processes can lead to novel features. Even very small changes (mutations) in the genes controlling development can have a profound effect on morphology, and have been important in the evolution of novel structures and body plans. Arthropods, as well as annelids and vertebrates, have a highly modular body

Evolution: you work with what you've got!

Four principles underlie the role of developmental genes in the evolution of novel forms: (1) Evolution works with what is already present: New structures are modifications of pre-existing structures.

(2) Multifunctionality and (3) redundancy: Functional redundancy in any part of a multifunctional structure allows for specialisation and division of labour through the development of two separate structures. Example: the diversity of appendages (including mouthparts) in arthropods. (4) Modularity: Modular architecture in animals (e.g. arthropods) enables modification and specialisation of individual body parts. Genetic switches allow changes in one part of a structure, independent of other parts.

Myriopods

Insects

Arachnids

Crustaceans

Segmental modifications produce a large amount of variation in arthropods.

Developmental genes and arthropods Antp

A

Head (mandible/maxillae) Head (other mouthparts)

Scr

Thoracic legs

Antp

B

Abdomen Wings

Abdomen end

Antp

abd

Scr

Antp

Ubx

C

D

abd-A

By looking at the DNA sequences in a series of genes we can piece together the order in which genes were duplicated and modified. The sequence above shows the order in which genes that are expressed in various parts of an arthropod appeared, starting with the original antennapedia (Antp) gene, which controls the development of appendages near the head.

We can identify which body segments the genes are expressed in and so work out the order in which body segments were modified. Above we start with a primitive arthropod (A). Three genes control development of the head, the middle segments, and the tail. Subsequent duplication and modification of genes produces an arthropod resembling a centipede (B), then a primitive wingless insect (C), and finally a modern winged insect (D).

1. Describe how modularity allows the evolution of complex features:

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Scr

2. Outline how studying the duplication of genes provides evidence for evolution:

WEB

KNOW

LINK

139 138

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140 What You Know So Far: Evidence for Evolution Interpreting the fossil record

HINT: Include reference to relative dating and past environments.

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you:

193

Homologous proteins and DNA sequences

HINT: How can sequence homology help determine phylogeny?

Biogeographical evidence

HINT: What do homology and vestigial structures tell us about common ancestry?

HINT: Include reference to island biogeography and continental drift.

No Cla t fo ssr r o Us om e

Homologous structures

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REVISE


141 NCEA Style Question: Evidence for Evolution In 2004, a fossil of an unknown vertebrate was discovered in northern Canada and subsequently called Tiktaalik roseae. The Tiktaalik fossil was quite well preserved and many interesting features could be identified. These are shown on the photograph of the fossil below. The shoulder bones are not attached to the skull, allowing its neck to turn independently of the body.

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194

Tiktaalik's head is flattened horizontally like that of a crocodile with the eyes on top, looking up.

Rod-like bones that help pump water over gills are present, but the presence of ribs indicates that lungs were also present.

The bones of the limbs have a primitive pentadactyl arrangement, similar to tetrapods, which allowed it to support its body weight.

do

he

og

ed

Gh

The fossil of Tiktaalik was covered with scales much like those of fish.

Fish-like fins are clearly visible.

1. Use the information above to place Tiktaalik on the time line of vertebrate evolution. Discuss the evidence for your decision.

Jawless fish

Bony fish

Amphibians

Reptiles

Birds

Mammals

150 mya

300 mya

365 mya

400 mya

550 mya

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Vertebrate ancestor

TEST

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195

142 KEY TERMS AND IDEAS: Evidence for Evolution

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1. Test your vocabulary by matching each term to its definition, as identified by its preceding letter code. fossil

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A The science determining the relative order of past events, without necessarily determining their absolute age.

fossil record

B The fossilised remains of organisms that illustrate an evolutionary transition. They possess both primitive and derived characteristics.

homologous structure

C A structure that has lost its ancestral function but has been retained through evolution in a much reduced.

phylogenetic tree

D The preserved remains or traces of a past organism.

relative dating

E The sum total of current paleontological knowledge. It is all the fossils that have existed throughout life’s history, whether they have been found or not.

transitional fossil

F Structures in different but related species that are derived from the same ancestral structure but now serve different purposes, e.g. wings and fins.

vestigial structure

G The evolutionary history or genealogy of a group of organisms represented as a ‘tree’ showing descent of new species from the ancestral one.

2. The diagram right shows the evolutionary relationship of a group of birds based on DNA similarities:

(a) Place an X next to the last common ancestor of all the birds:

(b) How many years ago did storks diverge from vultures?

DNA difference score

10

5

0

Flamingo

Ibis

(c) What are the most closely related birds?

(d) What is the difference in DNA (score) between:

i: Storks and vultures:

ii: Ibises and shoebills:

Pelican

Stork

New World vulture

(e) Which of the birds is the least related to vultures?

50

(f) How long ago did ibises and vultures share a common ancestor?

3. (a) The diagrams right show the forelimbs of a whale, bird, and human. Shade the diagram to indicate which bones are homologous. Use the same colour to indicate the equivalent bones in each limb.

(b) What does the homology of these bones indicate?

40

30

20

Human

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10

0

Millions of years ago

No Cla t fo ssr r o Us om e

Shoebill

Bird

Whale

TEST


Trends in human evolution

No Cla t fo ssr r o Us om e

Achievement Standard

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3.6

Key terms

Recognisable trends characterise the evolution of humans: bipedalism, increase in brain size, reduction in teeth, reduction in facial projection, and increasing importance of art, spirituality, tool technology, and sociality.

Biological evolution ape

Au. afarensis

Achievement criteria and explanatory notes

Ardipithecus ramidus

Achievement criteria for achieved, merit, and excellence

Australopithecus spp.

c

A

Demonstrate understanding of trends in human evolution: Use biological ideas to describe trends in human evolution.

c

M

Demonstrate in-depth understanding of trends in human evolution: Use biological ideas to explain how or why trends in human evolution occur.

c

E

Demonstrate comprehensive understanding of trends in human evolution: Link biological ideas about trends in human evolution. This may involve justifying, relating, evaluating, comparing and contrasting, and analysing using scientific evidence.

bipedal (bipedalism) carrying angle Denisovans

Dmanisi fossils gracile

hominid

hominoid Homo

H. erectus

H. ergaster

H. floresiensis H. habilis

H. heidelbergensis

H. neanderthalensis

Explanatory notes: Trends in human evolution

H. sapiens

Trends in human evolution refer to changes over time in relation to…

primate

Paranthropus spp.

1

Human biological evolution begins with early bipedal hominins and may require comparison with living hominids. These trends involve:

a

Skeletal changes linked to bipedalism.

robust

b

Changes in skull and endocranial features that reveal changes in brain structure.

sexual dimorphism

c

Changes in the manipulative ability of the hand.

2

Human cultural evolution including:

a

The use of tools (stone, wood, and bone) and changes in tool technology.

Cultural evolution

b

The use of fire

Acheulean (tool)

c

Clothing

Broca's area

d

Abstract thought, including communication, language, and art.

e

Food gathering, including hunter gatherer to domestication of plants and animals.

f

Shelter including caves, temporary settlements and permanent settlements.

3

Patterns of dispersal of hominins. Hominins refers to living and fossil species belonging to the human lineage.

prognathic

valgus angle

c

Mesolithic

Mousterian (tool) Neolithic

Oldowan (tool) Palaeolithic

Wernicke's area Dispersal multiregional hypothesis Out of Africa hypothesis

c

143 - 157

161 - 169

No Cla t fo ssr r o Us om e

c

prehensile

Activity number

173 - 179


What you need to know for this Achievement Standard

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Humans as primates

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Activities 142 - 146

By the end of this section you should be able to:

c

Describe primate characteristics as they relate to humans, especially features of the hand and skull.

c

Describe the anatomical and behavioural features that are unique to humans.

c

State the full classification of modern humans.

The biological evolution of humans Activities 147 - 160, 182

By the end of this section you should be able to:

c

Describe the selection pressures on early hominins and the benefits of reducing body hair and adopting a bipedal gait as a form of locomotion.

c

Describe the anatomical features associated with bipedalism, including features of the pelvis, the significance of the valgus (carrying) angle, and the position of the foramen magnum.

c

Describe trends in the size and shape of the skull, face, and dentition from Australopithecus through to early Homo species to Neanderthals and modern humans. Explain what endocranial features tell us about changes in brain size and organisation.

c

Describe trends in the dexterity and manipulative abilities of the hand from Australopithecus through to early Homo species to Neanderthals and modern humans. Relate these to the emergence and increasing sophistication of tool use.

The cultural evolution of humans Activities 161 - 172, 182

By the end of this section you should be able to:

Describe the features of the Palaeolithic tool cultures (Oldowan, Acheulean, Mousterian), identifying advancements in tool technology at each stage.

c

Explain how the controlled use of fire influenced and benefited human cultural evolution.

c

Explain the significance of purpose-made clothing in human cultural evolution. Identify when humans began to make and wear clothing, explain why, and describe the evidence for its origin.

c

Describe trends in and consequences of brain development, including the beginning of abstract thought and the development of language and of the areas of the brain associated with it.

c

Describe and explain the increasing importance of art and spirituality in human cultural evolution and relate these trends to other changes occurring at the same time.

c

Describe and explain the change from a hunter-gatherer lifestyle to one involving the domestication of plants and animals. Describe trends in the types of shelter associated with these changes, including reference to caves, and temporary and permanent settlements.

Patterns of hominin dispersal Activities 173 - 182

By the end of this section you should be able to:

No Cla t fo ssr r o Us om e

c

c

Compare and contrast the main hypotheses for the origin and dispersal of hominins, including evidence. Include reference to the out of Africa and multiregional hypotheses.

c

Describe and explain how new fossil and genetic evidence is revealing a more complicated picture of human origins and dispersal, including the likely interbreeding between hominin populations and its consequence to modern populations. Include reference to the Dmanisi fossils, Denisovans, Neanderthals, Homo naledi, and/or the Flores finds. Explain the importance of accurate dating to the interpretation of these finds.


198

143 General Primate Characteristics

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Key Idea: Primates exhibit unique, but quite generalised, morphological, physiological, and behavioural features. Morphological features include five digits on the hands and

feet, physiological features include a longer gestation than other mammals, and behavioural features include prolonged infant dependency and keen social behaviour.

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The gestation (pregnancy period) in primates is longer than most other mammals. Primates typically have one young per pregnancy (below). Infancy is prolonged with longer periods of infant dependency and a large parental investment in each offspring. This nurturing increases the survival rate of the young and allows cultural development.

The life span of a primate is generally longer than most other mammals and there is a greater dependency on highly flexible learned behaviour. Primates tend to be highly sociable (above). Unusually for mammals, adult males of many primate species often associate permanently with the group. The brain is large and generally more complex than in other mammals. There is an emphasis on vision, the visual areas of the brain are enhanced. Well developed binocular, stereoscopic vision provides overlapping visual fields and good depth perception. Colour vision is probably present in all primates, except specialised nocturnal forms.

RA

Chimpanzees and gorillas spend more time out of trees than do either of the Asian apes. The chimpanzee above shows typical knuckle-walking behaviour. Their relatively long arms facilitate this mode of locomotion.

KNOW

LINK

No Cla t fo ssr r o Us om e

Primates have a generalised dental pattern particularly in the back teeth. Unspecialised teeth enabled primates to adopt a flexible omnivorous diet.

Primates have a tendency toward erectness, particularly in the upper body, as seen in the gorilla, above. This tendency is associated with sitting, standing, leaping, and (in some) walking. WEB

A trend towards a reduced snout and flattened face and reduced olfactory regions in the brain. Baboons go against this trend, with a secondary increase in muzzle length.

Gibbons are the smallest of the apes and are specialised to use brachiation (a technique of under-branch swinging), in combination with rapid climbing, midair leaps, and bipedal running, to move quickly through the forest.

LINK

143 144 145

Monkeys walk quadrupedally on the palms of their hands and the soles of their feet. In the trees, they walk along the tops of branches, gripping them with their hands and feet.

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199 1. On the diagram of the capuchin below, briefly describe the general physical characteristics of all primates as indicated:

No Cla t fo ssr r o Us om e

The primate pictured is a white-fronted capuchin monkey (Cebus albifrons) from northern South America. These monkeys inhabit the mid-canopy deciduous, gallery forests.

Brain size and specialisation:

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Vision:

Collarbone:

Face shape and snout:

Teeth shape and dental arrangement:

Posture:

Hands and feet:

Limb joints:

Reproduction:

Social organisation:

No Cla t fo ssr r o Us om e

2. Humans belong to the order Primates. Describe the features of humans that characterise their primate heritage:

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200

144 Hominoids and Hominins flattened noses. Hominins (humans and their extinct closest ancestors) are a subtribe within this larger taxon identified by human features including dentition and brain size. The older taxon hominid is now a collective term encompassing the great apes and hominins and no longer refers just to humans.

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Key Idea: The hominins include modern humans and their extinct ancestors. Hominins are part of a larger superfamily, the hominoids, which also includes the apes. The hominoids (apes as well as humans and their ancestors) are large, tailless primates, with bony eye ridges and

Family Hominidae (hominids)

Superfamily Hominoidea

Hominoid features (lesser apes & hominids) • • • •

No tail Semi-erect or fully erect posture Broad chest, pelvis, and shoulders Relatively long arms and mobile shoulder joints • Larger brain

Characteristic features of the hominids: • Large and sexually dimorphic • Most predominately quadrupedal • Most omnivorous • Typical ape-like dentition but teeth large in gorillas and small in humans • Complex social behaviour

Subfamily Ponginae

Family Hylobatidae

Subfamily Homininae

Features possessed to varying degrees by subfamily Homininae: • Partially or habitually bipedal and ground dwelling • Large cerebral cortex • Reduced canines • Highly sensitive skin, body hair reduced

Orangutan

Siamang

Tribe Gorillini: Gorillas

Gibbon

Characteristic features of the lesser apes:

• • • •

Tribe Hominini: Humans, their ancestors, and chimpanzees

Subtribe Hominina Humans & their ancestors

All found in Southeast Asia Long forearms with hook-like fingers specialised for brachiation Pads on the rump (ischial callosities) Arboreal; sleep on tree branches and do not build nests

Subtribe Australopithecina Australopithecines (extinct)

Subtribe Panina Chimpanzees

Hominins

1. Use the information above to complete the phylogeny of Hominoidea:

Hominoidea

Superfamily

No Cla t fo ssr r o Us om e

Family

Subfamily

Tribe

Subtribe

2. What are the differences between hominoids and hominins?

KNOW

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201

145 The Primate Hand up, hold, and manipulate them, although the degree to which a primate can do this depends on the species. Humans have a highly advanced ability to manipulate objects with their hands because the thumb is very long relative to the hand.

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No Cla t fo ssr r o Us om e

Key Idea: Primates have grasping hands, but the human hand is particularly developed with respect to dexterity and the manipulation of objects. Primates have a grasping hand. They are able to pick things

The fingers have end tactile pads that contain huge numbers of nerve endings, producing a highly sensitive surface.

Index finger and little finger are able to pivot and move towards each other, allowing the fingers to form around small objects.

Large muscles, especially around the thumb, produce a powerful grip.

Nails are found on at least some digits in all modern primates.

Flexible joints in the hand allow it to flex, increasing dexterity.

Highly mobile thumb, able to touch all other fingers on the hand.

Chimpanzees are very capable tool users, but their dexterity is limited by the length of their hand compared to the thumb and the rigid wrist bones that limit wrist rotation.

New research suggests manipulating objects may not have been the only important factor in the evolution of the human hand. The human hand shape is one of the only configurations possible that maintains dexterity while allowing the hand to form a fist. Although a punch with a closed fist produces the same force as a slap with an open palm, a punch delivers the force to a smaller area, producing a much greater impact and potential for damage to an opponent.

LBS

Grips of the human hand

Power grip

1. Name two possible selective pressures acting on the human hand:

Precision grip

No Cla t fo ssr r o Us om e

Power grip

All photos LBS

Precision/ power grip

2. Explain why being able to manipulate objects is an evolutionary advantage:

3. Identify two features that make the human hand so dexterous and compare them to a chimpanzee hand:

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LINK

LINK

WEB

153 143 145

KNOW


202

146 Primate Skull Features Gorilla

Orangutan

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No Cla t fo ssr r o Us om e

Key Idea: Identification and comparison of different parts of a primate skull can help to identify the type of primate and various aspects of its biology (e.g. diet). The skull of the gorilla is not typical of primate skulls in general. It is highly specialised for its niche, which includes processing a low-grade diet of foliage. It is shown here to acquaint you with the terms used in describing the features of primate skulls. The skulls shown on the right are of two apes (a male gorilla and an orangutan), and an Old World monkey (a baboon). The baboon skull is clearly quite different from those of the apes. Diastema (gap

Baboon

between two teeth)

1. Label the gorilla skull above, using the list of anatomical terms in the box above. (b)

(a)

(c)

Male gorilla skull

(d)

(e)

(k)

(j)

(f)

Anatomical terms

Brow ridge Sagittal crest Zygomatic bone (malar) Foramen magnum Nuchal crest Prognathic muzzle

Mandible Zygomatic arch (=cheek bone) Canine Molars Cranial vault

(g)

(i)

(h)

2. Briefly describe the function or significance of each of the seven features below that are found on gorilla skulls:

(b) Nuchal crest:

(c) Massive zygomatic arch:

(d) Massive molars:

(e) Foramen magnum at rear:

(f) Large canines:

(g) Heavy brow ridge:

3. The female skull differs markedly from the male skull in a number of ways. Briefly describe four features that are different between the male skull (above) and the female skull (right) which is shown smaller here: (a) (b) (c)

Female gorilla skull

(d) LINK

KNOW

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(a) Large sagittal crest:

LINK

147 150

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203

147 Human Skull Anatomy

No Cla t fo ssr r o Us om e

Key Idea: An understanding of simple skull anatomy is useful when comparing the skulls of humans and their ancestors. Knowing the names of the major bones, as well as the features associated with a modern human skull, will help

you to identify some of the evolutionary â&#x20AC;&#x2DC;landmarksâ&#x20AC;&#x2122; in the development of humans. Use this page to compare the features of a modern human skull with the skulls of early humans described later in this topic.

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1. Label the views of a modern human skull using the list of anatomical terms in the blue box below: (g)

(a)

(b) (c)

(d)

(e)

(f)

(h)

Anatomical terms

Glabella, frontal bone, zygomatic arch, nasal bones, maxilla, occipital bone, nuchal line, mastoid process, sagittal suture, mandible, temporal line, parietal bone, foramen magnum, malar (zygomatic) bone, occipital protuberance

(i)

(o)

(j)

(k)

(l)

(n)

No Cla t fo ssr r o Us om e

(m)

(p)

2. Describe six features considered to be characteristic of modern human skulls: (a) (b) (c)

(d) (e) (f) Š 1988-2016 BIOZONE International ISBN: 978-1-927309-56-8 Photocopying Prohibited

LINK

LINK

150 146

KNOW


204

148 Trends in Human Evolution: Overview here. The early australopithecines were almost certainly ancestral to Homo habilis, which was ancestral to modern humans. Some populations of Homo erectus migrated out of Africa, eventually giving rise to populations of Homo in the Middle East and Europe. Neanderthals eventually evolved in Western Europe and modern humans in Africa.

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No Cla t fo ssr r o Us om e

Key Idea: The hominin fossil record shows clear evolutionary trends towards bipedalism, increased brain size, increased height, and increased technical ability. The diagram below and opposite shows a consensus view of the trends in hominin evolution over time. Only the five species representative of the general trends are shown

Australopithecus afarensis

Mean brain volume 1016 cm3

Mean brain volume 552 cm3

Mean brain volume 457 cm3

3.9 million -

Homo erectus

Homo habilis

2.8 million -

2.9 million years ago

1.9 million -

1.5 million years ago

600,000 years ago

179 cm

130 cm

110 cm

0

CC

4.

u

co

es

s en

rD

e di

Oldowan tools

Australopithecus afarensis

Homo habilis

1. Describe the general changes in the following trends:

(a) Angle of the face:

(b) Size of the brain and skull:

(c) Height and stance:

(d) Skill at tool making:

WEB

KNOW

LINK

LINK

LINK

148 150 151 162

Acheulean tools

Homo erectus

No Cla t fo ssr r o Us om e

Di

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205 Climate and environmental changes Forested

Fluctuating glacial/ interglacials

Open grassland

Cool

No Cla t fo ssr r o Us om e

Warm

2 mya

Present

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4 mya

Homo neanderthalensis

Homo sapiens

Mean brain volume 1512 cm3

Mean brain volume 1335 cm3

500,000 - 40,000 years ago

200,000 years ago - present

183 cm

Didier Descouens CC 4.0

170 cm

Mousterian tools

Neolithic tools

Homo sapiens

Homo neanderthalensis and Homo sapiens lived at roughly the same time. However H. sapiens evolved in warmer Africa and H. neanderthalensis evolved in cooler Europe. They may have overlapped in space for a few thousand years as H. sapiens migrated out of Africa.

Homo neanderthalensis

Homo neanderthalensis became extinct about 30,000 years ago.

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Homo heidelbergensis (not shown)

2. What was happening to the climate and environment as human ancestors evolved?

3. The skulls of Homo neanderthalensis and Homo sapiens are similarly sized. Describe the main differences between them:

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206

149 Human Evolution: Probable Phylogenies of fossil data. The hominin lineage underwent an adaptive radiation about 3 mya, producing many different species. The genus Australopithecus gave rise to the genus Homo and the genus Paranthropus, which coexisted with early Homo, but eventually became extinct about 1 mya. The genus Homo is represented by many species as successive waves migrated out of Africa. Homo sapiens, which migrated out of Africa 80,000-60,000 years ago, is now the only living species.

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Key Idea: Homo sapiens are the last representative of a once extensive, multi-branched hominin evolutionary tree. Distinguishing the human lineage from all these species can be difficult and in some cases open to interpretation. The diagram below shows a possible evolutionary history of hominins, demonstrating the fact that human evolution was not a linear sequence and that many phylogenies are tenable. There is much controversy over the interpretation Denisovan hominin dated at > 30,000 (Russia). Species currently not assigned.

Homo sapiens

Homo neanderthalensis

Homo Homo floresiensis Finds such as H. georgicus erectus

*

Homo sapiens idaltu

generate debate over the various models of the hominin lineage. H. georgicus is found outside Africa somewhat earlier than expected.

?

*

Homo heidelbergensis

Homo antecessor

1

*

?

2

Homo habilis

Homo ergaster

Homo georgicus

*

Time (millions of years ago)

Australopithecus sediba

*

Australopithecus africanus

? ?

Homo naledi

*

3

Homo rudolfensis

Australopithecus garhi

Homo naledi was discovered in 2013 in Rising Star Cave, South Africa. Becuase the bones where found on the surface it is very difficult to date. It may have lived as long ago as 2.8 million years ago.

?

Australopithecus afarensis

?

Australopithecus anamensis

*

*

Orrorin tugenensis

*

6

?

Sahelanthropus tchadensis

*

149 148 157

*

Ardipithecus ramidus ramidus

5

LINK

?

?

Species in bold are representative of the trends seen in hominin evolution.

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Australopithecus bahrelghazali

?

4

LINK

Paranthropus aethiopicus

?

?

Australopithecus deyiremeda

*

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*

?

Kenyanthropus platyops

7

Paranthropus robustus

Paranthropus boisei

Ardipithecus ramidus kadabba

*

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0

*The species marked with an asterisk (*) were all unknown a decade or so ago (and may be missing from many textbooks on the subject). There are likely to be many as yet â&#x20AC;&#x2DC;undiscoveredâ&#x20AC;&#x2122; species in the fossil record between 7 and 4 million years ago.

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Group

Examples

Homo erectus, Homo ergaster, Homo floresiensis

Homo erectus and closely related species show increasingly sophisticated tool cultures. H. erectus spread throughout Asia. There is much debate over how the different erectine species are related, with some paleontologists suggesting that all the erectines should be labelled as one species.

Homo habilis

This group shows the first signs of brain enlargement, more meat in the diet as well as the first recognisable stone tool culture. The post-cranial (below the head) skeleton remains small and slight, much like that of the australopithecines.

Paranthropines

Paranthropus robustus, Paranthropus boisei

These early hominins represent a group specialised for eating a bulky, low-grade vegetarian diet. They evolved large cheek teeth, powerful chewing muscles and a generally robust skull (large crests for muscle attachment, heavily buttressed face).

Australopithecines

Australopithecus afarensis, Australopithecus africanus, Australopithecus sediba

The earliest australopithecines were among the first apes to achieve bipedalism. They possessed a gracile body form and were probably opportunistic omnivores, scavenging meat from carcasses and exploiting a range of resources.

Ardipithecus ramidus, Orrorin tugenensis

Essentially chimpanzee-like animals that have begun to show some human characteristics in their locomotion (bipedalism) and in the shape and arrangement of their teeth. Sahelanthropus tchadensis may be a common ancestor of chimpanzees and humans.

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Homo sapiens, Homo neanderthalensis, Homo heidelbergensis

There have been many recent discoveries of relatively recent Homo species throughout Eastern Europe and Asia. How these fit into the hominin lineage and how they are related to modern humans are still debated. These specimens influence the interpretations of early human migration across the world.

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Archaic and modern humans

Erectines

Habilines

Very early hominids

1. On the opposite page, colour in the blue outlined species boxes so that all species in the group are coloured the same: archaic and modern humans (orange), erectines (green), habilines (red), paranthropines (yellow), australopithecines (black), and very early hominins (blue).

2. The relationships between ancestral hominins is open to interpretation. The diagram opposite allows for various phylogenies to be constructed as hypotheses because the exact lineages are unknown. Starting at Australopithecus afarensis, complete three likely lineages for the evolution of Homo sapiens by writing the species in order of appearance. You can use the dotted lines to help you but other paths may be possible. The first one has been started for you:

Australopithecus (a)

afarensis , Homo habilis, Homo ergaster...

(c)

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(b)

3. Explain how finds such as Homo naledi and Homo georgicus force us to rethink our understanding of how and where humans evolved:

4. Which hominin existed for the longest length of time? 5. Which hominin is the probable most recent ancestor of Homo sapiens?


208

150 Trends in Skull Anatomy Modern humans have rather gracile skulls compared to their ancestors. The cheek bones and jaw are both smaller and the brow ridges are much reduced relative to earlier hominins. These changes tend to reflect a change in diet to one that requires less chewing (e.g. from tough vegetable matter to a greater amount of (cooked) meat).

Skull features

3. Braincase (a) Shape of forehead (slope, height). (b) Rear view: where is skull the widest, low down or high up? Shape: pentagonal, rounded, bell-shaped? (c) Presence of crests: Nuchal crest for neck muscles, Sagittal crest for jaw muscles. (d) Shape of occipital region (back of skull) when viewed from the side: presence of bun? (e) Dorsal (top) view: where is the skull widest (rear, middle ear, etc.)? (f) Position of foramen magnum (opening at base of skull connected to spine).

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Key Idea: The trend in hominin skulls has been towards a greater volume, flatter face, and more gracile features. The shape of the modern human skull is quite different from its ancestors and that of Neanderthals. The human skull has a very high forehead and domed skull, whereas early ancestors had flatter foreheads and more elongated skulls. The skulls show in this activity are representative of the many hominins both modern and prehistoric. The features mentioned below and shown in the diagram below are features that should be noted when looking at trends in skull evolution. 1. Face (a) Size of the face compared to the braincase. (b) Degree of prognathism (snout or muzzle development) of the jaw and mid face (mid-face projection). (c) Development of brow ridges (supraorbital tori): size, thickness, arching. (d) Size of cheek region. 2. Jaws (mandible) (a) Size and thickness of lower jaw. (b) Degree of curvature of dental arcade (tooth row). (c) Presence or absence of chin.

Sagittal crest present? (site of attachment for jaw muscles)

Shape and slope of forehead

Brow ridge development?

Brain case: size and shape

Facial angle

Nuchal crest present? (site of attachment for neck muscles)

Size and shape of zygomatic arch (cheek bones)

Size of biting front teeth (incisors), canines and molars

Position of the foramen magnum (hole at the base of the skull that joins on to the spine)

Degree of prognathism (snout or muzzle)

Size of mandible (jaw bone)

Diastema (gap) between incisors and canines present of absent?

Chin present?

(a) Australopithecus afarensis:

(b) Homo habilis:

(c) Homo erectus:

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150 146 147

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1. For each of the hominin species describe the features of the skull. Use the diagram above as a guide.

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209

Australopithecus afarensis

Homo habilis

Homo erectus Heavy brow ridge

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Sloping forehead

Large teeth, including large canines

Angle/position of foramen magnum (FM)

FM

FM

No chin

Prominent cheek bones

Large jaw

Homo neanderthalensis

Homo sapiens

Occipital bun

ffNeanderthals evolved in Southern and Western Europe

and are generally thought of as being adapted for the cooler conditions found there. However examination of the nasal cavity finds it does not fit the general rule in mammals that in cold climates there is usually a reduction in the size of the nose and nasal cavities. The Neanderthal nose size is therefore a bit of an oddity and may be linked simply to the degree of facial projection. Also the internal sinuses are small and do follow the rule for cold climates.

ffThe skull features a large occipital 'bun' which may

reflect an enlarged occipital lobe. The occipital lobe is involved with visual processing. It could also reflect a larger cerebellum, which is involved in the coordination of movement and spatial information.

(d) Homo neanderthalensis:

(e) Homo sapiens:

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FM

ffThe modern human skull sports a high vertical forehead

and large domed skull. This reflects an increase in the size of the frontal lobe of the cerebral cortex.

ffThere is no brow ridge and the facial and cheek bones have

all been reduced in size. The jaw is smaller relative to the skull than in any other hominin, as are the cheek bones and teeth. This may reflect a shift in diet to food that required less chewing (less powerful musculature would be needed so muscle attachments can be less robust).

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FM

ffThere is also no nuchal ridge as the skull is now balanced

directly above the spine so only small muscles are required to hold it upright. There is a prominent chin which acts as a buttress (support) for the small jaw.


210

151 Trends in Brain Volume adult brain averages around 1335 cm3, but ranges between 1000 and 2000 cm3. But intelligence is not just a function of brain size. There are large mammals, such as elephants and whales, with brain volumes greater than ourselves and yet are (arguably) not considered to be as intelligent. It appears that relative brain size is the important thing (brain size relative to body size). Modern humans have a brain volume three times that predicted for an ape with our body size.

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Key Idea: The evolution of a large brain was crucial to our development of language, technology, and culture. The human brain is responsible for our unique behavioural qualities. It makes up just 2% of our body weight, but demands about 20% of the body’s energy at rest. This makes the brain an expensive organ to maintain. The selection pressures for increased brain size must have been considerable for additional energy to be made available. The normal human Brain volume for hominin species

Years ago (mya)

Hominin species

Growth in brain size in humans and chimpanzees

Average brain vo lume (cm3)

1500

Australopithecus afarensis

3.5

457

1300

Paranthropus robustus

2.0

520

1100

Paranthropus boisei

2.5

1.5

Homo rudolfensis

2.0

Homo habilis

1.8 ?

Homo naledi Homo ergaster

Homo heidelbergensis Homo floresiensis

860

1016

0.05

1512

900 700 500

Chimpanzees

100

380

0.08

Humans

300

1250

0.05

Homo sapiens

700

0.5

0.2

Homo neanderthalensis

515

552 560

1.8

Homo erectus

450

Brain size (cm3)

Australopithecus africanus

0

1335

Table above: Summary of the changes in estimated brain volume recorded from fossil hominins. The dates for each species are generally the middle of their time range for long-lived species or at the beginning of their time range for short-lived species.

Graph above right: In most primates, including chimpanzees, brain growth, relative to body size, slows markedly after birth while body growth continues. In human infants, brain growth does not slow until more than a year after birth, which results in larger brain masses for humans than for chimpanzees at any given age (or body weight).

2

4

6

8

10

Age (years)

12

14

16

18

20

2016 research shows that rapid brain expansion in humans was linked to a single substitution mutation about 800,000 years ago. This mutation changed the function of an existing gene and is associated with rapid proliferation of nerve cells in the neocortex. The mutation is unique to humans and is fixed in the human genome (all humans have it).

1. Plot the data in the table on the estimated Brain volume for hominin species (above) onto the graph below. Changes in hominin brain volume over time

1600

Mean volume of 1335 cm3 for living humans

1200 1000 800 600

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Estimated brain volume (cm3)

1400

Mean volume of 400 cm3 for chimpanzees

400 200 0

4.0

3.0

2.0

Millions of years ago

1.0

0

2. There were two ‘bursts’ (sudden increases) of brain expansion during human evolution. Indicate on the graph you have plotted where you think these two events occurred. LINK

KNOW

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148 167

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211

Brain size vs body height in hominins

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Brain size vs body height in hominins ffBrain size can be correlated with body height in

Frontal lobe

2000

hominins. Three distinct clusters emerge, indicating three phases of evolutionary development.

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ffHomo floresiensis, found on the Indonesian island

1500

Brain volume (cm3)

of Flores, clearly falls outside these clusters. Its brain size to body size ratio is similar to that of the Australopithecines, but key aspects of its morphology, such as its small canine teeth and organisation of the brain, identify it as Homo. In addition, the Flores finds were associated with relatively advanced stone tools.

Homo sapiens

1000

Erectines

Homo naledi

500

Australopithecines

Homo floresiensis

A. afarensis

0

1.00

1.25

1.50

1.75

2.00

Height (m)

H. sapiens

3. Explain the significance of the high energy requirement of a relatively large brain:

4. Comment on the significance of the brain/body size growth curve in humans compared with other primates:

5. (a) With respect to the brain size: body size ratio, comment on the position of H. floresiensis with respect to other hominins:

(b) Comment on the significance of the Flores finds:

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6. There is no firm date for H. naledi. Based on your plot opposite, what approximate date would you assign to this fossil?

7. What evidence is there that human brain expansion was associated with a beneficial mutation?

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Brocaâ&#x20AC;&#x2122;s ar

Controls the lips, jaw, to palate, and during spee


212

152 Trends in Dentition the course of hominin evolution, there was a general trend for a reduction in the size of the teeth tooth and jaw. This was a likely consequence of including a greater proportion of cooked foods, which required less chewing, in the diet. The teeth of modern humans are relatively small and generalised, reflecting an omnivorous diet of mainly processed (e.g. cooked) foods.

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Key Idea: Changes in dentition (the type, number, and arrangement of teeth) and jaw structure of our hominin ancestors can reveal information about our evolution. During early hominin evolution teeth (especially the molars) and jaws tended to be large. The paranthropines are the extreme example of this trend. Their diet of coarse vegetation required very large and powerful jaws and molars. During

Early hominins

Australopithecus afarensis • • • • •

Relatively large canine teeth Relatively large jaw V-shaped dental arcade Thin tooth enamel Diet probably consisted of fruits with some tougher material

Late hominins

Homo habilis

• Reduced canine teeth • Large molars and incisors • Dental arcade more like H. sapiens but still intermediate • Thick tooth enamel • Diet probably included vegetable matter and some meat (probably from scavenging)

Homo erectus

• • • • • •

Thick jaw bones No chin Relatively large molars Parabolic dental arcade Thick tooth enamel Diet probably included vegetable material and a large proportion of meat

Homo sapiens

• Shortened jaw, allows large bite force to be generated with little effort • Chin reinforces jaw, but leaves room for tongue muscles • Thick tooth enamel • Small molars adapted to chewing cooked and soft food • Parabolic dental arcade

Dental formulae all follow: I-2, C-1, P-2, M-3

Adaptations to a coarse diet

Paranthropus boisei had jaws and teeth adapted to a diet of very coarse vegetation and hard seeds. Their jaws produced a massive bite force of 2161 newtons, which helped to break food up. A modern human's maximum bite force is 777 newtons.

Teeth had a very thick coating of enamel to protect them.

Massive molars and premolars aided effective grinding action.

1. Describe the general trend in the evolution of hominin teeth:

2. What is one possible purpose of the chin in modern humans?

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150

The L shape of the jaw and the position of its joint allows the molars and premolars to meet at the same time giving an effective chewing action.

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In many primates, the canine teeth are used in behavioural and social interactions, especially in species which show marked sexual dimorphism. Threat gestures, such as yawning (above), help maintain social order.

Reduced size of canines permitted rotatory action, helping to grind coarse food up. The reduced size of the incisors provides more room for molars.

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213

153 The Importance of Ardi our understanding of hominin evolution. Until recently, it had been theorised that our earliest ancestors moved about very much like the chimpanzees of today. However the evidence from the Ar. ramidus skeleton shows that this is not the case and that bipedalism developed in quite a different way to what was once thought. Moreover, a dextrous hand developed early and is also an ancient trait.

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Key Idea: Analysis of the skeleton of Ardipithecus ramidus has produced findings that suggest bipedalism and a manipulative hand are very ancient features. The first fossils of Ardipithecus ramidus were discovered in the Middle Awash region of northeastern Ethiopia in 1994. After many years of excavation, a partial skeleton was unearthed. Studying the skeleton of Ar. ramidus is beginning to change

Brow ridge

Skull: The skull of Ar. ramidus shares certain features with Australopithecus, including a reduction in the size of the canine teeth in both male and females. This implies a reduction in aggression between males. The orientation of the base of the skull on which the brain stem rests suggests that the parts of the brain involved in visual and spatial perception were already beginning to develop.

Relatively small cheek bones

Prognathic muzzle

Reduced canine teeth

Ardipithecus ramidus skull features

Pelvis: The pelvis of Ar. ramidus indicates that the modern pelvis, evolved for bipedal locomotion, began its evolution in the trees. Although several features of the upper pelvis strongly indicate bipedalism, features of the lower pelvis show that muscles associated with tree climbing were still well developed.

The primitive features of the Ardipithecus hand that are shared with Homo.

Human hand

Features associated with bipedalism that are shared by Ardipithecus and Homo

Feature associated with tree climbing that is shared by Ardipithecus and Pan

Foot: The foot of Ar. ramidus is a generalised one, with some human-like features, such as a rigid foot, as well as some modern ape-like features, such as an opposable big toe. These features indicate that Ar. ramidus spent considerable time climbing in trees.

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Well developed thumb

Short, flexible palm

Socket joint for femur

Human pelvis

Images redrawn from C. Owen Lovejoy, et al Science, vol 326, 2009

Short metacarpals

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Hand: Analysis of the hand of Ar. ramidus shows that it is similar to our own, and that human hands are therefore close to the primitive form and not as greatly modified for tool use as was previously thought. Ar. ramidus had a flexible wrist and the opposable thumb was well developed. By contrast, chimpanzees move on the ground by knuckle walking, a motion that requires strengthening of the wrist and knuckle bones and lengthening of the palm, making the hand less flexible and not as dextrous.

Lack of strengthened knuckles

Ardipithecus ramidus pelvis

Chimpanzee pelvis

The foot is rigid in both Ardipithecus and Homo

Big toe points to the side

Homo sapiens foot

Big toe points forward

LINK

Ardipithecus ramidus foot

LINK

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145 155 153

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214 Proposed evolutionary tree with Ardipithecus Pan (chimpanzee) - Knuckle walker - Skilled climber - Short stiff back - Flexible, grasping feet - Strengthened wrist and elongated palm - Large incisors for eating fruit - Similar size in males and females - Canine teeth in males larger than in females

Homo - Habitual upright walker - Terrestrial biped - 'S' shaped flexible lower back - Multiple environment omnivore - Similar size in males and females - Small canines in males

Chimpanzee-human Last Common Ancestor (CLCA)

- Long, flexible lower back - Short flexible palm and wrist - Palm walking tree climber (not brachiating or knuckle walking) - Canines larger in males

Ardipithecus

- Facultative upright walker - Able tree climber - Retained long flexible lower back - Woodland and forest omnivore - Similar body size in both sexes - Small canine teeth in males

This simplified evolutionary tree of hominids shows that chimpanzees have continued to evolve into a specialised tree climber and are not simple modifications of the Chimpanzee-human Last Common Ancestor (CLCA). Indeed, the CLCA was an ape-like creature with many generalised features that have undergone further modification in both humans and chimps alike.

1. Describe the evidence for reduced aggression between Ar. ramidus males:

2. Explain why the human hand might now be viewed as the primitive type:

3. Describe the evidence for bipedalism developing in a primarily arboreal (tree-dwelling) ancestor rather than in a knuckle walking, terrestrial ancestor:

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Modified from C Owen Lovejoy, et al Science, vol 326, 2009

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Gorilla

4. How does having a generalised body plan increase possible evolutionary pathways?

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215

154 Bipedalism and Nakedness both evolutionary responses to the changing climate of East Africa about 7-3 mya. However, a 2009 analysis of the 4.4 mya Ardipithecus fossils indicates that these very early hominins were still primarily forest dwellers, so any current hypotheses must account for the emergence of bipedalism in a forested environment. The Ardipithecus finds indicate that bipedalism was strongly associated with provisioning, and was later reinforced by a move into less forested habitats as savannah became established throughout Africa in the later Miocene.

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Key Idea: Bipedalism provided advantages such as better provisioning, greater safety, and greater efficiencies in locomotion and thermoregulation. The first major step in the evolution of humans as a distinct group from apes was their ability to adopt the habitually upright stance we call bipedalism. Closely linked to this shift was the reduction in body hair. A number of selection pressures for hair reduction are described below (left). Early studies suggested that bipedalism and hair reduction were

Hair reduction

Retention of head hair

Hair on the head and shoulders has been retained to reflect and radiate heat before it reaches exposed skin.

Parasite control

A reduction in body hair would have made it easier to control external parasites such as fleas and lice. This would have been increasingly important when early hominins began to use a 'home base'. Many external parasites need to complete their life cycle at a single location so that hatching eggs can reinfect their host.

Bipedalism

Seeing over the grass

An upright posture may have helped early hominins to see predators or locate carcasses at a distance. Carrying offspring

Walking upright enabled early hominins to carry their offspring, so the family group could move together. Provisioning as a selection pressure The ability to carry food while walking seems to have been important in the initial development of bipedalism. Females would have favoured males able to provide energy-rich foods, which would improve offspring survival and increase reproductive rate. The ability to carry food from its source to a place of safety would have had a great survival advantage. Efficient locomotion

Thermoregulation

About 3 mya, the vegetation patterns in East Africa began to favour open grasslands, with fewer forested areas. This environment would have provided fewer opportunities for shelter from the sun, creating a selection pressure for the refinement of several thermoregulatory mechanisms.

Holding tools and weapons

Tool use was probably a consequence of bipedalism, rather than a cause. Upright walking appears to have been established well before the development of hunting in early hominids. Thermoregulation

Upright walking exposes 60% less surface area to the sun at midday and there is greater air flow across the body when it is lifted higher off the ground.

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Shorter, finer hairs (not hair loss) in early hominins would have allowed greater heat loss via radiation from the skin surface. Well developed sweat glands in humans enable heat loss at 700 watts m-2 of skin (greater than any other mammal).

Once bipedalism was established, changing habitats would have provided selection pressure for greater efficiency. Being able to move across the growing savannah without expending large amounts of energy would have offered a great survival advantage.

1. What advantages might an early human ancestor have gained by adopting a bipedal stance?

2. (a) What selection pressures are likely to have been important in the evolution of bipedalism initially?

(b) What environmental changes could have reinforced the advantages of bipedalism to human ancestors?

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LINK

LINK

WEB

156 155 154

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216

155 Adaptations for Bipedalism adapted for climbing rather than upright walking. They can walk on two legs but with difficulty and with a lurching gait. The evolution of the human skeleton has brought the body in line with the centre of gravity. This allows a person to walk without tilting to the side or backwards and forwards.

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Key Idea: Important changes in the skeleton are associated with the move to bipedal locomotion in early hominins. The features of the human skeleton that help it maintain a bipedal posture are best seen when compared to the habitual knuckle walker, the chimpanzee (below). Chimpanzees are

Comparing humans and chimpanzees

Humans have several notable skeletal adaptations for bipedalism that chimpanzees lack. The foramen magnum is centrally positioned on the bottom of the skull, helping it balance on top of the spine. The spine is S-shaped. This brings the centre of gravity in line with the body and helps to cushion the forces acting the on the body during walking and running. The femoral head is angled so that the knee is positioned under the centre of the body which helps the body remained balanced during walking. The pelvis is short and broad, providing attachments for the large gluteus muscles that assist with keeping the body upright.

Foramen magnum (FM) further forward so the skull balances on the spine

Human

Human

Chimpanzee

Chimpanzee

Foramen magnum (FM) toward the back of skull

Long narrow pelvis

Broad, basin-like pelvis

Gluteus muscles prevent tilting when the opposite leg is off the ground.

Femoral head angled and strengthened

The carrying (valgus) angle ensures the knee is brought under the body during walking.

S-shaped spine acts like a spring

Straight spine

Chimpanzee in standing position

Human

Chimpanzee

Human

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Chimpanzee

1. Describe the features of the human skeleton that are adaptations for bringing the body in line with the centre of gravity:

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LINK

LINK

155 154 156

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217 Quadruped: Straight spine and rear-ward FM, femur is at right angles to knee so an upright stance is less stable.

Biped: S-shaped spine and forward FM. Femur (thigh) is angled out from knee (the carrying angle). A longer femur provides a longer, more efficient stride.

Evidence that Australopithecus afarensis was bipedal Chimpanzee

Human End of femur at the knee joint

End of femur at the knee joint

Bony buttress

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End of femur at the knee joint

Australopithecine

Lateral condyle

Inner (medial) condyle

Chimpanzee foot

Lighter shading represents points of contact with the ground

Curved toe bones

Big toe diverges (well separated from other toes

The foot of a chimpanzee has relatively long, curved toes, with an opposable big toe adapted from grasping but ill-suited to upright walking. The foot transmits weight from the heel, along the outside of the foot, and then through the middle toes.

Human foot

Lighter shading represents points of contact with the ground

Large heel bears increased weight

Australopithecine footprints

Direction of weight transmission during walking

Big toe aligned with other toes (not opposable)

The human foot is adapted as a weight bearing platform rather than a grasping structure. The toes are reduced relative to those of chimpanzees. The foot is arched so transmits weight from the heel, along the outside of the foot, across the ball and through the big toe. This weight transference conserves energy during locomotion.

Heel bone missing from fossil

Foot bones (OH8) from Bed I at Olduvai Gorge

The australopithecine foot had an aligned big toe, as in humans, making it difficult if not impossible to grasp branches with the hindlimbs. The heel bones that have been found also indicate habitual bipedalism. Computer simulations suggest that A. afarensis could walk like humans but could not have walked like a chimpanzee.

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2. Study the images of the human and chimpanzee foot in this activity. What features of the human foot produce an efficient platform for walking? Contrast these with the chimpanzee foot.

3. Describe features of each of the following in A. afarensis that provide evidence of bipedalism:

(a) Foot:

(b) Knee joint:

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218

156 Analysis of Lucy's Skeleton with bipedal locomotion. Although there is no doubt that Lucy was habitually bipedal, a number of skeletal features suggest that tree climbing was still an important part of this hominin's niche, perhaps associated with escape, security, or foraging. A. afarensis is an important because she shows transitional stages between earlier apes and modern humans.

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Key Idea: The skeleton of Australopithecus afarensis shows both advanced and primitve features. The reconstruction of Lucy (Australopithecus afarensis), below, shows the skeletal features of an early bipedal hominin. Lucy still possessed ape-like features but she was a fully-bipedal hominin with all the adaptations associated

Lucy’s* ape-like characteristics

Lucy’s bipedal features

Shape of the tooth row (dental arcade) is half way between the straight-sided U-shape of an ape jaw and the more rounded, parabolic shape of a human jaw.

The foramen magnum was much further forward than in apes and much closer to the position in humans.

Lucy’s lumbar vertebrae were broad for effective weight transmission from the upper body to the pelvis. The australopithecine spine had an S shaped curvature, similar to that of modern humans.

Shoulder joint orientated towards the head, similar to the orientation in chimpanzees and other arboreal quadrupeds.

Lucy’s pelvis was broad and basin shaped, similar to a human pelvis. It would have supported the upper body when upright.

Funnel-shaped chest (thorax).

Lucy’s limbs showed human-like features consistent with bipedalism. The femoral (valgus) angle was similar to humans, bringing the knees under the body.

Arms relatively long compared to legs. Highly mobile wrist.

Curved finger bones.

Butressing of the knee was more similar to humans than to apes.

Relatively short legs.

Arched feet, wide heels, and big toes aligned with the other toes and not opposable.

Highly mobile ankle joint.

Toes are long and curved.

Redrawn from a photograph by © David L. Brill 1985

*Lucy is the name given to a specimen of Australopithecus afarensis

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1. When she was discovered, Lucy was labelled "the missing link" by media, highlighting the fact her skeleton showed both ape-like and human-like features. Describe the features that show Lucy was habitually bipedal and contrast these with features that show her ape ancestry:

LINK

KNOW

LINK

154 155

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219

157 Hominin Data Sheets the data that you have collected. The data sheets for each hominin have some clearly defined places for answers. Use the ‘Additional notes’ box for comments on culture, skeleton, habitat, etc. It is useful to make comparisons between hominins dated immediately before and after the one you are making notes about. Note that extra information is provided here: you are not required to provide detail for every species. The trends are important.

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Key Idea: The following data sheets will help you consolidate information on the various hominin species. This exercise will allow you to collate the information on various hominin species from a wide range of sources. The data summary sheets give you space to describe key features and points on each species. Your descriptions should be brief; in many cases, key words or brief sentences will be all that is required. Below are some ideas on how you can analyse

Skull features

Note the size of the skull, the shape of the braincase and face. The size and shape of the jaw and the dentition and the implications of these on diet.

Skeleton

This section mainly deals with what is called the post-cranial skeleton; the skeleton apart from the skull. Various features can be investigated: (a) Structure of the pelvis: shape, size of birth canal. (b) Angle of the femur (thigh bone) and the knee joint. (c) Structure of the spine: curvature and relative size of the vertebrae. (d) Depth of rib cage. (e) Structure of the foot; evidence for adaptations for walking and primitive features if present. (f) General bone thickness and limb proportions.

Geographic distribution

List the regions (e.g. east Africa, Asia) or the countries (e.g. Kenya) where fossils of the species have been found to date. The sites are marked on the map with a triangle.

Habitat

Describe the nature of the habitat of the hominin if known. This may be African open savannah for the earlier forms but may include more varied habitats (sub-tropical forests, temperate forests, tundra, and even subarctic) for the later, more widespread hominins.

Culture

The various hominin species each have characteristic cultural features. Consider the following points: (a) Stone tool technology used. (b) Other materials used (wood, bone, ivory, clay for pottery, copper, bronze, iron, precious metals). (c) Degree of workmanship required to produce the tool. (d) Evidence of using fire (e.g. to cook (hearth), to hunt, for security from predators). (e) Evidence of artistic expression (e.g. rock paintings, carvings, statues) and their significance. (f) Evidence of abstract thought, spirituality and religion (e.g. burials, cannibalism). (g) Evidence of spoken word (voice box development), written word, higher technologies for communication.

Ardipithecus ramidus

Europe

Asia

Ardipithecus existed from 5.8 to 4.4 million years ago. It stood 1.2 m high and weighed around 50 kg. The brain case was small, at around 350 cm3, and the jaw had reduced canine teeth. Fossils of the pelvis show it was capable of being bipedal but it still had an opposable toe and spent time climbing. The hand was characterised by a short palm and a flexible wrist. Ar. ramidus was probably an omnivore and fruit eater.

Africa

Australia

= Fossil sites

Years:

mya

Brain size:

cm3

Height:

m

Weight:

kg

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Diet:

Geographic distribution: Additional notes:

Redrawn from C. Owen Lovejoy et. al, Science, vol 326, 2009

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KNOW


Europe

Australopithecus spp.

Asia

Australopithecus anamensis Africa

Gué

A. anamensis was discovered at Kanapoi, Kenya. The find consists of complete upper and lower jaws, teeth from several individuals, a piece of skull, arm bones and a leg bone. A. anamensis existed between 4.2 and 3.9 mya. The teeth and jaws are similar to older fossil apes. The lower leg bones, however, show strong evidence of bipedalism and the upper arm bone is extremely human-like.

rin N icola 3.0

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s CC

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220

Australopithecus garhi

This find, made in Ethiopia, is known from a partial skull. This skull, dated at about 2.5 mya, differs from other species of Australopithecus in its combination of features: the primitive skull shape and extremely large size of the teeth (especially molars). The brain case is 450 cm3. Stone artefacts found nearby suggest this hominin may have used tools before Homo habilis.

= Fossil sites

= Fossil sites

2.0

Australopithecus sediba

3.0

A. afarensis

Brett Eloff. Courtesy Profberger and Wits University CC 4.0

3.5

A.anamensis

4.0

Mya

Australopithecus afarensis

Small, gracile, small-brained, and bipedal, A. afarensis existed between 3.9 and 3.0 mya. The skull is similar to that of a chimpanzee, except for more human-like teeth. Brain size 375-550 cm3. The humanlike pelvis and leg bones confirm they were bipedal. Height ranges from 1.0 to 1.5 m, weight 29-42 kg (sexual dimorphism). Some researchers claim such differences suggest two separate species, not sexual dimorphism. Nicknames: Lucy, The First Family, Laetoli footprints.

A. afr icanus

A.garhi

2.5

Ji-Elle CC 3.0

Australopithecus sediba was discovered in cave deposits at the Malapa site in South Africa. Features seen in the brain, feet, hands, and pelvis of A. sediba suggest this species was on the direct evolutionary line to Homo. However, it also exhibits australopithecine features such as long upper limbs and a small cranial capacity of about 420 cm3.

A. sediba

Europe

Asia

Africa

Australia

= Fossil sites

Artist's reconstruction

Years:

mya

Brain size:

cm3

Height:

m

Weight:

kg

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Geographic distribution:

Additional notes:

Composite reconstruction

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Australopithecus africanus

Europe Asia

A. africanus existed between 3.0 and 2.0 mya. Similar to A. afarensis, it was also small, gracile, and bipedal, but slightly larger in size. Brain size may also have been slightly larger, ranging from 420 to 500 cm3. Weight 40 kg, height 1.3 m. Generally considered to be specific to South Africa. Differs from the early australopithecines in east Africa by having larger back teeth and smaller canines. The jaw shape is human-like.

Africa

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221

Australia

= Fossil sites

Years:

mya

Brain size:

cm3

Height:

m

Weight:

kg

Artist's reconstruction

Geographic distribution:

Additional notes:

Sts 5 skull from Sterkfontein South Africa

Paranthropus boisei

Europe

Asia

One of a group of robust species of early hominin. Existing between 2.1 and 1.1 mya, it had a brain size of 500-545 cm3. Weight 34-49 kg and height 1.24-1.37 m (sexually dimorphic). Known for its massive jaws, large molars, and attachments on the skull associated with chewing muscle. Probably fed on a tough diet of low grade foods: tubers, grains, and other plant material. This species is also referred to by some researchers as Australopithecus boisei.

Africa

Australia

= Fossil sites

Years:

mya

Brain size:

cm3

Height:

m

Weight:

kg

Artist's reconstruction

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Geographic distribution:

Additional notes:

OH 5 found at Olduvai Gorge in Tanzania

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Paranthropus robustus P. robustus lived 2.0-1.5 mya and had a brain size of about 520 cm3. It had similar body proportions to A. africanus, but a larger and more robust skull and teeth. Height 1-1.2 m and weight 40-54 kg (sexually dimorphic). The massive face was flat or dished, with large brow ridges and no forehead. Massive grinding teeth set in a large jaw suggest that it probably fed on a diet of tough, coarse plant food that needed a lot of chewing. May have used bones as digging tools. Some researchers classify this species as Australopithecus robustus. Artist's reconstruction

Europe Asia

Africa

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222

Australia

= Fossil sites

Years:

mya

Brain size:

cm3

Height:

m

Weight:

kg

Geographic distribution:

Additional notes:

SK 48 from Swartkrans in South Africa

Homo habilis

H. habilis existed between 2.4 and 1.5 mya. Although similar to australopithecines in many ways (e.g. height of males is 1.3 m, weight 40 kg), their brain size was considerably larger (500 to 800 cm3). Some researchers argue that this species is too variable in its present classification. Instead, they propose that it be split into two species: Homo habilis (ER-1813, shown below) and the more robust Homo rudolfensis (ER-1470). One H. habilis brain cast shows a bulge of the Broca’s area, suggesting rudimentary speech.

Europe

Asia

Africa

Australia

= Fossil sites

Years:

mya

Brain size:

cm3

Height:

m

Weight:

kg

Artist's reconstruction

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Geographic distribution:

Additional notes:

KNM-ER 1813 skull from Koobi Fora region to the east of Lake Turkana, Kenya

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Homo ergaster

Asia

Larger brained than previous Homo species, with volumes of 850 to 1000 cm3. Previously considered to be part of Homo erectus, but now thought to be a separate species. Homo ergaster refers to what used to be called early African forms of Homo erectus, existing 1.8 to 1.4 mya. Earliest hominin with human-like body proportions. A nearly complete skeleton of a 9 year old boy was 1.6 m tall (estimated 1.8 m and 60 kg adult size).

Africa

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223 Europe

Australia

= Fossil sites

Years:

mya

Brain size:

cm3

Height:

m

Weight:

kg

Artist's reconstruction

Geographic distribution:

Additional notes:

KMN-ER 3733 skull from Koobi Fora region to the east of Lake Turkana, Kenya

Homo georgicus

Europe

Dmanisi

Asia

Fossils found in Dmanisi, Georgia in 2002 were originally classified as H. ergaster, but size differences have since lead to the new classification Homo georgicus. The fossils, which include four skulls and several jaw bones have been dated at 1.8 mya. The small size (1.5 m tall and ~50 kg) and cranial capacity (600-780 cm3) of the fossils place H. georgicus as a descendent of H. habilis and predecessor of H. erectus. Tooth-wear patterns indicate an omnivorous diet. They may have been the earliest hominin to venture out of Africa, some 800,000 years before H. erectus. This finding challenges the theories that hominins required a large brain and advanced tool making skills to be able to migrate out of Africa.

Africa

Australia

= Fossil sites

Years:

mya

Brain size:

cm3

Height:

m

Weight:

kg

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Geographic distribution:

www.skullsunlimited.com

Additional notes:

H. georgicus exhibited strong sexual dimorphism; the males were considerably larger than the females. This is quite a primitive trait, and not observed to the same degree in later more modern hominins such as Homo neanderthalensis.

D2700 (skull), and D2735 (lower jaw) of Homo georgicus from Dmanisi, Georgia

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224

Homo erectus

Asia

Africa

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Homo erectus is reserved for the later Asian forms (shown here), with dates ranging from 1 million to 300,000 years ago. At one time thought to be the first humans to venture out of Africa (but see H. georgicus). They differ from H. ergaster by having skulls that were strongly buttressed with ridges of bone, skull walls greatly thickened, and larger brain volumes (range: 1000 to 1250 cm3). Height 1.7 m and weight 60+ kg. These simple huntergatherers used stone tools and fire.

Europe

Australia

= Fossil sites

Years:

Brain size:

cm3

Weight:

kg

Artist's reconstruction

Height:

m

Geographic distribution:

Additional notes:

Homo erectus pekinenis or 'Peking Man' from Zhoukoudian Cave, near Peking in China

Homo floresiensis

Europe

Asia

A nearly complete skeleton (LB1), with a mix of primitive and derived features, was discovered on the Island of Flores, Indonesia, and named Homo floresiensis. The specimen, was small, 1.06 m tall, and weighed only 25 kg. It also had a very small brain capacity (only 380 cm3).

Subsequent H. floresiensis fossils have been found in conjunction with tools and remnants of fire indicating that the species had advanced behaviours. Fossils have been dated at 100,000-60,000 years.

Africa

Australia

= Fossil sites

Years:

mya

Brain size:

cm3

Height:

m

Weight:

kg

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Geographic distribution:

www.skullsunlimited.com

Additional notes:

LB1 skull from Liang Bua Cave, Flores Island, Indonesia

Some anthropologists argue that Homo floresiensis is a microcephalic, or malnourished version of modern H. sapiens. However, variations in its teeth, lack of chin, and low twist of the forearm bones lend support for a new species.

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Homo antecessor

225

Asia

Africa

Australia

= Fossil sites = Fossil sites

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Homo antecessor, a highly controversial species, dated 780,000-625,000 years ago. Discoveries at the Gran Dolina site in the Sierra de Atapuerca, Spain, make these the earliest known European hominin specimens. Fossils consist of nearly 80 postcranial, cranial, facial, and mandibular bones as well as teeth of at least six individuals. H. antecessor (‘pioneer’) shows a mixture of primitive and modern traits, with an especially modernlooking midface. Brain volume 10001150 cm3, height 1.6-1.8 m, weight 90 kg.

Europe

Years:

Homo antecessor from Gran Dolina, Sima de los Huesos in the Sierra de Atapuerca, Spain

Denisovan fossils

mya

Height:

cm3

Brain size:

g

Weight:

Geographic distribution:

Europe

Asia

Fossil fragments (tooth, finger bone, and toe bone) belonging to a previously unknown species of Homo were found in the Denisova cave in Altai mountains, Siberia, Russia. Carbon dating estimates their age at about 40,000 years. The Denisova hominin existed at the same time as modern humans and Neanderthals. The Denisova hominin has yet to be classified as a new species.

Africa

= Fossil sites

Australia

Additional notes:

Too few fossil fragments have been found for scientists to put together a physical description of the Denisova hominin.

Homo heidelbergensis

Europe

Asia

Homo heidelbergensis is probably a group of related but variable subspecies. Formerly known as archaic humans they have both modern and more primitive features. It is likely that both modern humans (in Africa) and Neanderthals (in Europe) evolved from this species. They had brain sizes ranging from 1100 to 1400 cm3. Height ~1.8 m, weight ~65 kg.

Africa

Australia

= Fossil sites

Years:

Brain size:

cm3

Weight:

kg

Artist's reconstruction

Height:

m

No Cla t fo ssr r o Us om e

Geographic distribution:

Additional notes:

Homo sapiens rhodesiensis or 'Rhodesia Man', from Broken Hill Mine, Kabwe in Zambia

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Homo neanderthalensis Neanderthals existed between 230,000 and 30,000 years ago. Average brain size was 1512 cm3 and they had short, squat, cold-adapted bodies with thick, heavy bones (height 1.5-1.7 m, weight 66-78 kg). Neanderthals and modern humans separated between 700,000 and 400,000 years ago, but there was probably some gene flow between nonAfrican humans and Neanderthals as recently as 100,000 to 50,000 years ago.

Europe

Okladnikov

Asia Africa

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226

Australia

= Fossil sites

Years:

Brain size:

cm3

Weight:

kg

Artist's reconstruction

Height:

m

Geographic distribution:

Additional notes:

La Ferrassie Skull, Le Bugue, Dordogne Valley in France

Homo sapiens

Europe

Asia

The first anatomically modern humans (AMH) appear about 160,000 years ago in southern African and the Middle East. Average brain volume 1335 cm3, height 1.75 m (males), weight 70 kg (males). Skeleton gracile. Humans underwent a sudden cultural revolution about 40,000 years ago, with the appearance of Cro-Magnon culture. Using a wider range of materials, their tool kits became markedly more sophisticated. They were skilled hunters, tool-makers and artists (cave art and music).

Artist's reconstruction

Africa

Australia

= Fossil sites

Years:

Height:

m

Brain size:

cm3

Weight:

kg

No Cla t fo ssr r o Us om e

Geographic distribution:

Additional notes:

'Cro-Magnon Man', from Cro-Magnon, Dordogne Valley in France

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158 What You Know So Far: Biological Evolution Trends in skull anatomy

HINT: Changes in skull size, brain volume and dentition.

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you:

227

Primate characteristics

HINT: General features of primates. Features of a dextrous hand.

Adaptations for bipedalism

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HINT: Adaptations for bipedalism. Selection pressures for bipedalism.

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REVISE


228

159 NCEA Style Question: Biological Evolution

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1. The diagram below shows the foot of a chimpanzee, a human, and Australopithecus afarensis.

Chimpanzee foot

Australopithecus afarensis foot

Compare the foot structures above. Use the diagrams to analyse and describe the evidence that Australopithecus afarensis was bipedal. Discuss the selective advantages of being bipedal within the environment in which Australopithecus afarensis evolved. You may use more paper if required.

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Human foot

TEST

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229

160 KEY TERMS AND IDEAS: Biological Evolution 1. Using the dd information you have learned in this chapter, identify the fossils below:

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(a) Decide whether or not the jaw below (b) The image below shows the top and (c) Describe the features that is that of a modern human. Circle rear of a non-human hominin skull. show the features that identify and annotate the photo to describe Annotate the photo and describe the this as a human features to support your argument in features that identify it as non-human. femur. the space below

48 cm

2. Draw lines to match up the hominid name with its meaning, then match the name to the correct skull number (1-8 below). Meaning:

Australopithecus afarensis

Man from the Neander Valley.

Australopithecus africanus

Handy man

Homo neanderthalensis

Southern Ape from Afar, Ethiopia

Homo sapiens

Southern Ape from Africa

Homo habilis

Man from the island of Flores or Flores man

Homo erectus

Knowing, or wise man

Homo floresiensis

Upright man

1

2

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4

3

6

5

Skull number:

No Cla t fo ssr r o Us om e

Name:

7

TEST


230

161 Cultural Evolution behaviours also evolved as they were learned and passed on to offspring. This non-genetic means of adaptation, called cultural evolution, further enhanced the success of early humans.

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Key Idea: Cultural evolution is a term used to describe the transmission of and changes to knowledge and ideas over successive generations. In addition to the physical evolution of humans, ideas and

Environmental forces

Over many millions of years, the evolution of human ancestors has been directed by natural selection. Environmental forces such as climate change, food supply, and predators, acted on the gene pool.

Climate change

The climate became drier and the forests which were the homes of the earlier primates gradually disappeared. This reduced shelter and meant that traditional food sources became scarce or disappeared. New food resources had to be investigated.

Resulting physical features

In response to these selective pressures humans evolved an upright stance with the head balanced on the spine and a large brain capable of learning, planning and passing on ideas. An upright stance freed the hands to grasp and manipulate objects in a very sensitive and precise way.

Fierce predators

Predators made a ground dwelling lifestyle dangerous. Early humans would have to develop solutions to protect themselves from attack.

Adopted niche

Predominantly ground living, opportunist/ scavenger. Able to exploit a number of varied habitats and utilise a range of food resources.

Cultural forces

The unique combination of brain and specialised physical features allowed early humans to learn from others and manipulate their environment to begin changing it to suit themselves.

Social intelligence

Technical intelligence

Being able to predict, using current observations, the habits of potential game, the rhythms of the seasons, and the geography of the landscape (e.g. location of water sources and caves).

Language to communicate ideas, plan survival strategies, and coordinate group activities such as resource gathering and hunting of increasingly larger game. Group bonding behaviour improves survival opportunities for members.

Producing artefacts from mental templates required an understanding of abstract ideas and physical processes: the fracturing behaviour of stone, angles of striking stone and how hard to strike, and the trajectory of a thrown projectile.

The modern human mind

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Natural history intelligence

Creating artefacts and images with symbolic meaning as a means of communication. Using knowledge of animal habits, tools, advanced planning and communication to coordinate the hunting of large game.

1. What is cultural evolution?

WEB

KNOW

LINK

LINK

LINK

LINK

161 162 166 168 169

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231 Development of agriculture

Development of stable settlements

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People learned to cultivate plants, especially grains, and domesticate animals. In the Middle East, about 8000 BC, they learned to grow wheat. In Mexico, about 500 BC, they began to grow maize. Rice (Asia)

Communities of grain cultivators became established. People lived in relatively large, permanent settlements. Such people developed qualities such as patience, industry, and a sense of property, preparing the way for further cultural evolution.

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Maize Maize Wheat Rice (Asia) MaizeAmerica) Wheat Rice (Asia) (Central (Central America) (Middle East) Wheat (Central America) (Middle East) (Middle East)

Maize

(Central America)

Rice (Asia)

Wheat

Donkey

(Middle East)

Development of cities

Arabian camel

Goat

Sheep

As communities became larger, trade and commerce began to develop. Large cities grew up where markets and trading systems developed. These were places where people could develop special skills such as pottery and metal work. It also resulted in rivalry and, in some cases war, between states.

The present and the future

The knowledge explosion

The success of humans as a species has presented modern populations with a number of complex problems (e.g. global pollution and over-population) and many ethical considerations. To live sustainably in a healthy environment, humans will need to change many of the current practices surrounding resource use and distribution.

Sharing ideas became easier once people began living in cities and the technology developed to spread knowledge. Rapid developments in science and technology in the last 200 years have influenced almost every aspect of daily life and significantly increased the rate of cultural evolution.

An increasing knowledge and expertise in genetics has made it possible to direct genetic change in other organisms, including our own species. Such abilities have many biological, ethical, and social implications.

Manipulation of the environment (e.g. damming rivers) allows humans to exploit resources in a way that wasn't previously possible. Medical advances have increased the human lifespan and advancements in technology have allowed humans to produce material goods at a staggering rate.

The move from opportunist scavenger to hunter-gatherer was a major stage in mankind's cultural evolution. It was taken in a series of small steps, over a very long time (perhaps a million years). A few human societies, such as the Australian aborigines last century, were still at this stage until very recently. 2. Describe two probable effects of a drying climate on the selection pressures directing the evolution of early hominins:

(a) Manufacture of bone and stone tools:

(b) Shelters and clothing:

(c) Use of fire:

(d) Cooperative hunting:

(e) Development of agriculture:

(f) Commerce and communication:

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3. Explain how each of the cultural developments listed below enhanced the survival ability of early humans:


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162 Trends in Palaeolithic Tool Cultures about 3.3 mya in eastern Africa, until the development of sophisticated tool kits in the Mesolithic (Middle Stone Age) about 10,000 ya. These tool cultures are known mostly by their stone implements. While other materials, such as wood, were probably also used, they did not preserve well.

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Key Idea: The development of stone tools is a defining characteristic of Homo. Particular, identifiable types can be matched with specific time periods and species. The Palaeolithic (Old Stone Age) is a period of early cultural development spanning the emergence of the first stone tools

Timeline of stone tool technologies

Oldowan

3.3 mya

3 mya

Oldowan (pebble) tool culture

Probably made by Homo habilis, these were crudely fashioned river-worn pebbles. A minimum number of flakes were knocked off from several angles to produce a core with a cutting edge (e.g. chopper, discoid, polyhedron). Although the cores may have been used as tools, it is known that the sharp flakes were also useful in cutting.

Acheulian

Mousterian

Upper Paleolithic

2 mya

1 mya

Flakes removed from one side only

Flakes removed from two sides

Chopper

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Polyhedron

Discoid

Biface shape: bulges outwards on both sides and has tear-drop shape

The core is the tool

Side-on view

Hand axe

Mousterian tool culture

Upper Palaeolithic tool culture

Flakes (not shown) and the cores are used as tools

Proto-biface

Acheulean tool culture

There was a rather sudden increase in the sophistication of tool making about 35,000 to 40,000 years ago. Both the modern Homo sapiens and the last of the Neanderthals produced flint tools of much finer workmanship using a technique called punch blade. Long, thin flakes are removed and shaped into different tool types. A number of European sub-cultures, e.g. Solutrean, emerged. Other material such as bone, ivory and antler became increasingly utilised to produce very fine tools such as needles.

Flakes removed from all sides

Cores

Made by H. erectus and archaic H. sapiens, these tools were typically 'tear drop' in shape and were crafted with a slight bulge on each broad surface (a bi-face). They ranged in size and are often referred to as hand axes although it is not clearly understood how they were used. They differ from the pebble tools in that there appears to be a standard design and each tool is manufactured using a great many more blows to remove flakes.

Made by Neanderthals and more refined than Acheulian tools. Flint became commonly used. This stone would chip in a predictable way when struck with another hard object so finer workmanship was possible. A particular technique from this period is known as the Levallois method. It involves the preparation of a core and striking off a large oval flake which is then retouched on one surface only (see the photograph on the right; the retouched surface is visible).

Present

Cleaver

Levallois scraper

Levallois method

Flake

Core

Handaxe from Le Moustier France. Flint, 8.5 cm.

Side scraper

Punch blade method

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Oldest dated stone tools

Solutrean blade

Bone needle

Core

Burin

Finely worked edge

Throwing stick

Flake

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233

A

D

B

C

1. Name the culture associated with each of the tools above (A-D) and describe the features that help identify them:

(a) Tool A culture:

(b) Tool B culture:

(c) Tool C culture:

(d) Tool D culture:

2. Identify the hominin species associated with, and the approximate time period for, each of the tool cultures below:

(a) Oldowan:

(b) Acheulean:

(c) Mousterian:

(d) Upper Palaeolithic:

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3. Describe the general trends in the design of the stone tool from Oldowan to Upper Palaeolithic cultures:

4. The tools that are recovered from early human prehistoric sites are almost invariably stone, bone or ivory. Explain why tools made from other materials are almost never recovered from these sites:

5. Name the materials used to make tools in the Upper Palaeolithic culture that were seldom used in earlier cultures:

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163 Palaeolithic Tool Use century. Hunter-gatherer people existed in places like the Kalahari desert in south west Africa, the Australian outback, and some of the more remote areas of South East Asia and South America. Anthropologists studying these primitive cultures gathered valuable insights into how our ancestors may have lived.

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Key Idea: Stone tool technology can be adapted for numerous purposes including spear heads, blades, and axes. It is possible to infer how the stone tools of early hominins were used by studying how similar tools have been used by recent 'stone age' societies. People using only stone-based technology were still in existence well into the first half of last

7

5

6

3

1

8

4

2

1. First match each of the diagrams above with the description of their function in the table below (place 1-8 in number column). Secondly, assign each tool with its correct name from the list below: Side scraper, borer, denticulate tool, spear point, chopper, backed flake, early hand-axe, late hand-axe No.

Name of tool

Description

This tool was probably used to scrape the fat and sinew from the underside of a freshly killed animal, in preparation for curing.

(b)

The curved, sharp edge of this tool would probably have been used to shave wood chips from spear heads.

(c)

Later forms of this tool were probably used to skin and dismember carcasses.

(d)

A simple tool used as an axe, probably to cut into wood or possibly to dismember a carcass.

(e)

Early forms of this tool may have been used as a pick-like tool to expose root tubers growing under plants.

(f)

Used as a knife, this tool had only one side with a sharp cutting edge so that pressure could be applied to the blunt edge.

(g)

Hafted to a pole with greased sinew or plant fibre, this flint tool would have provided an effective cutting edge for the spear.

(h)

The sharp narrow point of this tool makes it an effective drill when twisted back and forth. In this way, holes could be made in materials such as hides, wood, and ivory.

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(a)

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235

164 Fire started by natural events such as lightning. Whatever its origin, the controlled use of fire changed the course of both physical and cultural evolution, influencing dietary range and improving survival. Possible evidence exists for the use of fire up to a million years ago, but real evidence of controlled use of fire dates back only a few hundred thousand years.

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Key Idea: The controlled used of fire by early humans allowed them to eat a greater range of foods and to expand their range into darker and colder places. Just when and how early human ancestors began using fire is debated and may never be precisely known. It is likely that early fire was "captured" from the wild, e.g. from fires

Naturally set fires were the most likely source of early fire. Burning embers may have been carried back to home sites, or the fire used where it was.

The development of the hand-drill meant early humans could make fire when and where they needed it.

A not so obvious, but important use of fire, is its use in the construction of weapons. Wooden spear tips can be hardened in fire, allowing them to be made sharper and improving their penetrative power. Rocks heated in a fire become brittle and are therefore easier to shape into tools, such as blades and spearheads. The blade also holds a sharper edge.

Fire may also have been used as a hunting tool by setting fire to forests to drive out game. Fire could also be used for protection to drive off predators.

Fire provides light and can be used as a torch, allowing early humans to explore dark places such as caves. It may have helped with bonding, such as sitting around a campfire. Fire provided light and warmth at night.

Cooking is the most obvious use of fire. Cooking food makes it easier to chew and digest, releasing energy more quickly for the body to use. Fire also kills parasites and pathogens in the food. Fire can also be used to preserve food. Meat can be smoked and vegetable material can be dried.

1. List four uses of fire:

2. (a) Describe two important consequences of cooking food:

(b) Explain how cooking food provided a selection pressure for a smaller jaw and teeth:

3. Discuss the influence of fire on human cultural evolution:

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165 Shelter and Clothing body hair. However this then limited the ability to survive in cold climates as humanity migrated north out of Africa into Europe and beyond. The use of animal skins or woven plant material to make clothing provided a way of keeping warm. Building shelters allowed humans to shelter from both the weather and possible predators.

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Key Idea: The development of clothing and techniques to build shelters allowed the expansion of humans into colder climatic areas. Human ancestors would have had a far greater amount of body hair than humans today. The move into hot open grassland provided a selection pressure for the reduction of

Early humans and their ancestors are often depicted in popular texts wearing animal skins. However there is little direct evidence of humans wearing clothes until 26,000 years ago (the evidence is a finely worked bone needle). Evidence from burial sites also shows humans were adorning themselves (or at least their dead) with necklaces as far back as 35,000 years ago. The divergence of head lice and body lice (which live in clothes) suggests human ancestors began wearing clothes some 100,000 years ago. This finely worked bone needle is almost identical in shape to needles used today. This needle is dated between 17,000 and 10,000 years old.

Rosino

Liang Bua cave, Flores Island, Indonesia.

Didier Descouens CC 3.0

Although often called cavemen, human ancestors probably didn't start using caves regularly as shelter until they could control the use of fire. Bones of early australopithecines or Homo found in caves were likely taken there by predators or been washed in by ancient streams. Some of the first evidence of caves being used by humans is from the Atapuerca cave in Spain. It is dated at 1.2 million years old, but it is difficult to tell the exact relationship of the fossils to the cave.

Hide drying on rack

The first evidence of humans building purpose-built shelters dates to around 400,000 years ago. Post holes in the ground indicate poles were used as scaffolding for the shelter. Preserved bones from around 17,000 years ago in the Ukraine show humans there used mammoth bones and tusks as scaffolding, probably because there would have been few trees available to make wood scaffolding from.

1. (a) Identify the evidence for humans building purpose built shelters:

(b) Identify the evidence for humans making clothing:

(c) Suggest a reason why there is so little evidence of humans building shelters or making clothes:

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2. Suggest a reason why caves where probably not regularly used by humans and their ancestors until the controlled use of fire was developed:

3. What is the main purpose of clothing?

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166 Art and Spirituality western and eastern Europe. Growing evidence suggests Neanderthals too were culturally sophisticated. The stimulus for the new cultural development was probably a need to represent ideas about the unknown, such as death, hunting success, and fertility, in a concrete way. A wide range of materials were used to do this. Ivory, bone, clay, and stone were used to create sculptures, and the walls of rock shelters and caves were adorned with drawings, paintings, and basrelief (sculptures that stand out slightly from the rock wall).

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Key Idea: Human art and culture can be dated to as far back as 290,000 years. However a major cultural explosion took place about 35,000 years ago. Until recently, it was believed that art and spiritual beliefs first developed with the arrival of modern humans, particularly in Europe. However ancient artworks dating to nearly 300,000 years ago can be found outside of Europe. The beginning of a period 35,000 years ago marks a dramatic cultural development occurring simultaneously over large parts of

The evolution of art

ffArt requires at least some form of abstract thought.

To take an image in the mind and draw it or model it in real life first requires the formation of the idea and then the use of technical skill and imagination to shape an object or draw an image.

opportunistic. The image shown left is a drawing of a figure known as the Venus of Berekhat. It is a small statue just 3.5 cm high. It is thought a rock that looked vaguely human was used as a start and then shaped further (although this is debated). The statue is dated to about 230,000 years old.

ffSimilarly, rock painting may have developed from

Venus of Berekhat

simply adorning the body with pigments. The oldest known site where ochre (a red pigment) was used is dated at 164,000 years old in South Africa.

Body paint

Art and spiritualism

Artistic expression of spiritual ideas

Ancient paintings were created using natural pigments such as charcoal, manganese oxide, and ochre, which were applied to grease smeared on the rock surface. Although we can never be certain of what the artist was thinking at the time, it is likely that much of the ancient art had a religious or spiritual purpose. This can be hypothesised because: ffmany paintings occur in places that are difficult to access, e.g. deep in caves and often on the cave roof. ffmany paintings in some way represent animals that were hunted or fertility (e.g. female genitals represented as "pubic triangles"). ffmany figurines represent pregnant females or attributes in women related to fertility.

Burial ffThe oldest known intentional human burial is dated at 100,000

years, in Israel. Artefacts found with the bodies suggest a ritual of sorts. Burials became more common as ancient humans spread over the globe. Burials also became more elaborate, at least for some. Recent comparisons of burial sites show that the majority were plain with simple everyday items left with the body. Relatively few graves contained lavish or ornate materials which suggests some people had greater status than others.

ffThe leaving of personal items in the grave may indicate

religious or spiritual beliefs of what happens after death.

ffThe Neanderthals of Europe and Southwest Asia buried their

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Mesolithic tomb, France (modern human)

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Rama CC SA 2.0

dead with signs of ritualisation. The position and orientation of the body are consistently the same and some graves included grave goods such as tools or animal bones (although the validity of grave goods with burials is disputed).

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JosĂŠ-Manuel Benito PD

ffSome archaeologists think that the first art was

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238 Stages in art Bronze age begins in Europe 3200 BC

0 AD

Iron age begins in Europe 1500 BC

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Neolithic era begins in Europe 4000 BC Earliest example of pottery. Found in Xianrendong Cave. Dated to 18,000 BC.

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Earliest Japanese art. 14,000 BC

25,000 BC. Earliest ceramic art.

25,000 BC

Earliest of the European Venus figurines (37,000 BC).

The earliest Asian art is dated to 38,000 BC, found in the Sulawesi Cave in Indonesia.

Oldest known parietal art (cave paintings) Cave of El Castillo, 39,000 BC.

Earliest musical instruments. There is debate over the dating of various flutes but the oldest are at least 43,000 years old.

50,000 BC

Neanderthal artists create the La Ferrassie Cave Cupules in France, dated to 60,000 BC.

JosĂŠ-Manuel Benito CC 2.5

Earliest African art, the Venus of Tan-Tan, dated to 100,000 BC.

100,000 BC

200,000 BC

Bhimbetka petroglyphs, India, dated to at least 290,000 BC. Consist of depressions (cupules) hammered into the rock of the Bhimbetka cave.

Most Venus figurines (right) are small (approx 10 cm high) figurines of women with exaggerated breasts, buttocks, and body fat. They may have represented desirable traits among women to enhance fertility and survival. Venus of Berekhat, dated to 230,000 BC. The oldest known mobiliary art (figurines).

Venus of Willendor (30,000 years old)

300,000 BC

1. What evidence is there that much of the ancient art found so far had a religious or spiritual purpose?

2. What might the various Venus figurines have represented?

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3. What evidence is there that personal status may have played a part in ancient human society?

4. The earliest examples of musical instruments are about 43,000 years old. Explain why it is likely musical instruments were probably used well before this date:

5. Clearly, early humans devoted great effort to art and ceremony. How might these skills have been adaptive?

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Don Hitchcock CC 3.0

This Aurignacian (Upper Palaeolithic) flute, made from an animal bone, is about 43,000 years old. A similar flutelike piece of cave bear bone has been found at a Neanderthal hunting camp in Slovenia. The bone, also dated at about 43,000 years ago, suggests that Neanderthals may have made music but there is debate over the dating.

Ubirr rock paintings. Earliest known art in Australia (and Oceania) dated to 30,000 BC.


239

167 Communication and Changes in the Brain important specialisation of the human brain is the capacity for language. This is a result of the development of Wernicke’s and Broca’s areas. Specific differences associated with the left and right hemispheres of the brain are associated with these specialisations.

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Key Idea: The human brain is characterised by a highly enlarged cerebrum and well developed areas associated with speech and comprehension of language. The human brain is very large for a primate of our size, but this may not be as important as its internal organisation. The most

Wernicke's and Broca's areas

Wernicke's area is part of the brain in the cerebral cortex that is linked to speech. It is involved in comprehension and understanding of written words and spoken language. Its function becomes apparent if it is damaged. A person will then be able to speak fluently, but produce meaningless phrases.

Broca's area is also found in the cerebral cortex but in the frontal lobe of the brain. Broca's area is involved with the production of speech. It was discovered by Pierre Paul Broca when studying two patients who had lost the ability to speak after sustaining head injuries.

Frontal lobe

Wernicke’s area

The area concerned with understanding spoken words.

Broca’s area

Cerebellum (largely motor control)

Controls the muscles of the lips, jaw, tongue, soft palate, and vocal cords during speech.

Communication is probably the most important aspect of human cultural evolution. Humans communicate to request help, inform others, and share attitudes as a way of social bonding. The ability to accurately convey ideas to others, both in the present and future, has allowed humans to work together, often over multiple generations, to create buildings and technology, or more efficiently gather food.

Australopithecus with brain endocast

We do not know exactly when Homo began to use language, but comparing the features associated with language in modern humans with fossils of ancient hominins can give us an idea. Cranial endocasts of Homo habilis show that the brain appears to have development in both Broca's and Wernicke's areas. However, to produce the range of sounds used by modern humans in verbal communication, the larynx and the hyoid bone must also show certain features.

Boneclones

Didier Descouens CC SA 4.0

Evolution of communication

Neanderthal hyoid bone

The hyoid bone is located in the throat and anchors the tongue muscles. The structure of the hyoid bone and its position in Homo erectus suggests that H. erectus was not able to make the same range of sounds we can. However the structure and positioning of the hyoid bone in Neanderthals suggests they probably could make a similar range of sounds to modern humans. This suggestion is supported by computer generated models based on a Neanderthal hyoid fossil.

(a) Broca's area:

(b) Wernicke's area:

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1. What is the function of:

2. Homo erectus probably couldn't communicate verbally in the same way as Homo sapiens, but Neanderthals probably could. Explain why:

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168 Mesolithic Culture fishing, and food gathering techniques, which may have arisen because the warming climate would have resulted in increased productivity. The Mesolithic occurred during the current Holocene epoch, which is relatively warm compared to the previous epoch, the Pleistocene. The warmer climate resulted in glacial retreats, the growth of forests in Europe and deserts in North Africa, and the disappearance of the animals hunted during the glacial period.

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Key Idea: The Mesolithic period is marked climatically by the change from glacial to warmer climates, and archaeologically by the refinement and further development of human tools. The Mesolithic (Middle Stone Age) period occurred in Europe 12,000-3000 years ago, as the last glacial period ended. The tools produced at the time were small bladed geometric stone tools (microliths), and were often fitted into a handle of wood or bone. Mesolithic people used a wide variety of hunting,

Tools of the mesolithic period

Sickles: These two sickles are made of flint embedded into a handle made of horn (below, right) and an antler (right). Such tools were used to cut the grasses to gather their seeds and date from the Mesolithic period.

Didier Descouens

Antler handle

Harpoon: This flat harpoon is made of bone, and dates between 12,000 and 9500 years ago. It was found in France.

Single flint blade

Three flint microliths embedded to create cutting edge

Horn handle

Didier Descouens

Bone fish hook: This fish hook dates from the Mesolithic period and was found in Sweden.

Microlith: Made of flint or chert (a sedimentary rock). Microliths formed the points of hunting weapons such as spears. This microlith was found in the Tourasse cave, France.

1. The Mesolithic culture replaced the Upper Palaeolithic culture. When did the Mesolithic culture begin?

2. (a) Describe the key features that characterise the Mesolithic culture:

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(b) How did the Mesolithic culture differ from the Upper Palaeolithic culture?

3. Explain the significance of the warmer climate experienced during the Mesolithic period:

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169 Neolithic Culture years ago. Domestication of animals and the development of farming allowed a shift away from the hunter-gatherer economy of the Mesolithic to a food producing culture. Not all individuals had to be involved in food gathering activities, and some people developed specialised craft skills (e.g. potters). As permanent settlements developed, ideas and knowledge could be more easily transferred between people, resulting in a rapid expansion of cultural evolution during this period.

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Key Idea: The Neolithic is characterised by advances in farming and animal domestication practices, the development of crafts (e.g. pottery and weaving), the use of polished stone and flint tools, and the development of permanent settlements. The date of the Neolithic (New Stone Age) culture varies with geographic location. In the middle East it dates from about 10,000 years ago, and in Europe from 4000-2000

The origin of agriculture

Mesoamerica

Fertile Crescent

North China

Southest Asia

Beans, maize, peppers, squash, gourds, cotton, guinea-pigs, llamas

Barley, wheat, Emmer, Einkorn, lentils, peas, sheep, goats, cattle

Rice and millet

5000 years ago

10,000 years ago

Rice, bananas, sugar cane, citrus fruits, coconuts, soya beans, yam, millet, tea, taro, pigs

7000 years ago

Maize

South America

Lima beans, potatoes, squash, beans, and pumpkins

Africa

Millets, sorghum, groundnuts, yams, dates, coffee, and melons

Region of origin

Date (years ago)

Dog

Wolf

many places?

13,000

Goat

Bezoar goat

Iraq

10,000

Sheep

Asiatic mouflon

Iran, Iraq, Levant

10,000

Cattle

Aurochs

Southwest Asia

10,000

Pig

Boar

Anatolia

9000

Domestic fowl

Red jungle fowl

Indus Valley

4000

Horse

Wild horse

Southern Ukraine

6000

Arabian camel

Wild camel

Southern Arabia

5000

Bactrian camel

Wild camel

Iran

4500

Llama

Guanaco

Andean plateau

6000

Water buffalo

Indian wild buffalo

Indus Valley

4500

Ass

Wild ass

Northeast Africa

5500

Each domesticated animal was bred from the wild ancestor. The date indicates the earliest record of the domesticated form.

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Grindstone: This Neolithic grindstone was used to grind grain so it could be used in cooking.

JosĂŠ-Manuel Benito

Sandstein

Wild ancestor

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Domesticated animal

Neolithic people produced a wide range of purposespecific tools to harvest, store, and prepare food. The photo, above, displays food and cooking items retrieved from a Neolithic site in Europe. The containers are made of antlers and wood. LINK

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242 Dr J.F Burka: http://en.wikipedia.org/wiki/File:Orkney_Skara_Brae.jpg

Ox shoulder blade shovel Wickerwork basket

Antler pick

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The development of permanent settlements

Neolithic village at Skara Brae, Scotland.

The development of agricultural practices significantly changed the lifestyle of Neolithic people. The huntergatherer lifestyle gave way to food production using agricultural techniques. The need to tend to crops and animals resulted in a shift away from a nomadic lifestyle to living in permanent settlements.

Skara Brae, Scotland, is the location of Europe's most complete stone-built Neolithic village (above). It consisted of ten houses, and was occupied between 3180 and 2500 years ago. The people of Skara Brae raised cattle and sheep, and may have cultivated barley. The presence of fish bones and shells amongst the ruins suggest their diet was supplemented with seafood from the nearby ocean.

Neolithic excavation kit: Used in the construction of massive earthworks in Britain (such as Avebury Stone Circle). The pick made from an antler was used to loosen chalk, while the ox shoulder blade was used to shovel the soft rock into a wickerwork basket.

Arrow head: Made of flint, this finely worked Neolithic arrow head was recovered from the Algerian Sahara desert and is about 6000 years old, it is about 3 cm long.

1. The Neolithic culture replaced the Mesolithic culture. When did the Neolithic culture begin

(a) In the middle East?

(b) In Europe?

2. Describe the key cultural developments that characterise the Neolithic culture:

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3. Why was the shift of Neolithic people from hunter-gatherers to farmers an important step in cultural evolution?

4. How did the establishment of permanent settlements influence cultural evolution during the Neolithic period?

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170 What You Know So Far: Cultural Evolution Fire, shelter, and clothing

HINT: Uses and development

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you:

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Palaeolithic tool cultures

HINT: Oldowan, Acheulean, Mousterian, Upper Palaeolithic

Art, spirituality, and communication

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HINT: Development and art, culture, and communication. Development of the brain

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171 NCEA Style Question; Cultural Evolution

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1. Early Palaeolithic tool culture lasted almost 2.5 million years with only a few major developments in that time. At the beginning of the Upper Palaeolithic, about 40,000 years ago, there was a rapid expansion in the types and complexity of tools being made by humans. These represented a massive developmental leap in comparison to earlier stone tools.

Compare the stone tools of early species of Homo with stone tools from the Upper Palaeolithic. Discuss the developments that allowed the production of more complex tools and the effects these had on human cultural development. You may use more paper if required.

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TEST

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172 KEY TERMS AND IDEAS: Cultural Evolution 1. Test your vocabulary for this chapter by matching each term to its correct definition.

No Cla t fo ssr r o Us om e

Acheulean tools

A Area of the brain that allows the processing and comprehension of speech patterns. B The carrying angle of the femur to the knee, which in humans and their ancestors brings the knee under the centre of gravity.

cultural evolution

C A tool type sometimes referred to as pebble tools and associated with Homo habilis.

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Broca's area

Mousterian tools

D Tear drop shaped stone tools associated with Homo erectus and archaic Homo sapiens.

Oldowan tools

E Advanced tool type associated with Neanderthals. Made by striking a flake and retouching one side of it (the Levallois method).

valgus angle

F The change over time in accumulation of knowledge, rules, standards, skills, and mental abilities that humans use to survive.

Wernicke's area

G Area of the brain that allows for the production of speech sounds by controlling the jaw, tongue, lips, and vocal cords.

2. Identify the following tools as Oldowan, Acheulean, Mousterian, or Upper Palaeolithic:

A

B

C

2. (a) A:

(c) C:

(b) B:

(d) D:

D

3. Homo erectus is believed to be the first user of fire. Describe the benefit the use of fire would have had for them:

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4. Homo sapiens societies changed from being hunter-gatherer societies to agricultural societies about 10,000 BC. The development of agricultural skills brought many advantages to Homo sapiens, but there were disadvantages too. Describe one advantage and one disadvantage of developing an agricultural society:

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246

173 The Origin of Modern Humans hypothesis proposes that modern humans evolved from Homo erectus everywhere that Homo erectus preceded them. The replacement hypothesis proposes that modern humans evolved from an African Homo erectus (via an intermediate species called Homo heidelbergensis) and replaced all other forms of Homo throughout the Old World.

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Key Idea: The two main contesting theories on the origin of modern humans are the multiregional hypothesis and the replacement (out-of-Africa) hypothesis. Two primary hypotheses have been put forward to explain where modern humans evolved and what happened to the Homo species that preceded them. The multiregional Multiregional model

Replacement model

In this model, modern Homo sapiens emerged gradually throughout the world and, as the populations dispersed, they remained in 'genetic contact'. This gene flow between neighbouring populations ensured that the general 'modern human blueprint' was adopted by all. This limited gene flow still allowed for slight anatomical differences to be retained or develop in the regional populations. This model is based largely on fossil evidence and the anatomical characteristics of modern populations, but advocates of the model maintain that the mitochondrial DNA data can be interpreted in a way that supports it.

Also known as the “Out of Africa Hypothesis” and “Eve Hypothesis”. This model states that modern humans evolved from archaics in one location, Africa, and then spread, replacing the archaic populations, without interbreeding. Modern human variation is thus a relatively recent phenomenon. Mitochondrial DNA (mtDNA) analysis of modern endemic human populations showed that the highest level of genetic variation in mtDNA occurs in African populations, implying that H. sapiens arose first in Africa. Using the genetic distance between African populations and others as a measure of time, this model places the origin of modern humans at back to a single female (Eve) who lived there some 200,000 years ago.

Modern Homo sapiens

European Modern

African Modern

Asian Modern

European Modern

Present

African Modern

Asian Modern

Extinct

Extinct

Archaic Homo sapiens

European Archaic

African Archaic

European Archaic

Asian Archaic

African Archaic

Asian Archaic

0.5 mya

Gene flow

Little or no gene flow

Gene flow

Little or no gene flow

Homo erectus

European H. erectus

African H. erectus

European

Asian H. erectus

African H. erectus

Asian H. erectus

1.0 mya

African origin

Predictions made by this model

1. Fossils that show the change from one stage to the next in all geographic regions (transitional forms). 2. Modern traits should appear in the fossil record somewhat simultaneously all over the Old World range of Archaic Homo sapiens. 3. Today’s modern “racial” traits characteristic of a particular region can be traced back to ancient forms in that region. 4. The human species today should have a high degree of genetic diversity since it is an old species with distinct populations that have had a lot of time to accumulate genetic differences. 5. The amount of genetic variation within each modern human group is about the same since they have all been evolving together.

1. Transitional forms would be found in only one place (in this case Africa) which is the area of origin for modern humans. 2. Modern traits should appear first in one location (Africa) and then later elsewhere as the modern population spread to other parts of the Old World. 3. Modern and archaic populations should overlap in time outside the area that moderns originated (the process of replacement would not be instantaneous). 4. Humans today should have relatively little genetic diversity since the species is young. 5. Today’s modern populations should differ in the amount of genetic variation, the most diversity being found in the region where moderns first evolved (this would have been the oldest group and therefore the one that had the most time for genetic variation to accumulate).

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173 174 175

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Predictions made by this model

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African origin

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247 Evidence for dispersal

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There is little doubt that humans evolved in Africa. Fossils of ancient hominins such as Australopithecus afarensis, A. africanus and Homo habilis are all found in Africa. Analysis of fossils and genetic evidence supports theories that Homo erectus migrated out of Africa about 1.8 mya. Populations of H. erectus remaining in Africa gave rise to H. heidelbergensis, which also migrated out of Africa about 650,000 years ago but remained in Europe and Western Asia. Those populations gave rise to H. neanderthalensis. Homo heidelbergensis in Africa eventually gave rise to H. sapiens. H sapiens began to migrate out of Africa between 120,000 and 80,000 years ago but the movement was halted by a period of cold climatic conditions. Around 60,000 years ago the final migration of modern humans out of Africa and across Europe and Asia began.

Africa E

S

China

N

W+S Asia

M. East

MYA 3.0

Europe

Acheulean stone tools are found throughout Africa, Europe, and South and Western Asia, but appear to be largely absent from Eastern Asia. Tool cultures develop first in Africa then move to other parts of the world.

1.0

Analysis of various loci in the human genome show humans have very little genetic diversity. The analysis shows that outside of Africa, human genetic diversity is a sub-set of African genetic diversity.

Diversity (0 = low)

Locus (measurement)

Africa

Asia

Europe

30 microsatellites

0.807

0.685

0.730

Xq 13.3 (short arm X chromosome)

0.035

0.025

0.034

50 autosomal sequences

0.115

0.061

0.064

mtDNA control region

2.08

1.75

1.08

0.3

0.1

0.03

0.01

Oldowan Acheulian/ Palaeolithic

Acheulian-like Neolithic

Diversity in the CD4 locus on chromosome 12. Blue shading represents the amount of diversity.

1. State at what date the two models suggest that anatomically modern humans shared a common ancestry:

(a) Replacement model:

years ago (b) Multiregional model:

years ago

2. (a) Which hominin was the first to migrate out of Africa?

(b) At about what date did this migration occur?

3. How many successive waves of Homo migrated out of Africa?

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4. In the out of Africa model, modern humans move out of Africa to populate the rest of the world.

(a) Describe the fate of the other human populations already inhabiting these regions, according to this theory:

(b) Identify one example of such a population:

5. Summarise the evidence above and decide which hypothesis it supports: multiregional or out-of-Africa:

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174 The Dispersal of Modern Humans absence of ‘land bridges’ formed during the drop in sea level that occurs with the onset of glacials. Recent evidence suggests that island-hopping and coastal migration may also have been important, e.g. for the movement of people into Indonesia. The late development of boating and rafting technology slowed dispersal into Australia and the Pacific. New Zealand was one of the last places on Earth to be populated. (On the map, ya = years ago.)

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Key Idea: Hominins evolved in Africa. Around 60,000 years ago Homo sapiens began the final hominin migration out of Africa, eventually reaching all parts of the world. The map below shows a suggested probable origin and dispersal of modern humans throughout the world. An African origin is almost certain, with south eastern Africa being the most likely region. The dispersal was affected at crucial stages by the last glacial, when Ice sheets covered much of Europe. Dispersal was also affected by the presence or

The first modern humans appear in Europe 40,000 - 35,000 years ago

Iceland

Cro-Magnon 30,000 ya

The earliest dating in East Asia for modern humans is 67,000 years ago from Liujiang County in southern China

Skuhl 101,000 - 81,000 ya

Qafzeh 120,000 - 92,000 ya

Afar, Ethiopia 160,000 ya

Omo 130,000 ya

The probable area of origin for modern humans is south eastern Africa some 200,000 years ago

The Flores fossils, at 38,000 - 13,000 years suggests there may have been waves of movement into Indonesia.

Border Cave 115,000 - 62,000 ya

Lake Mungo 31,000 ya

New evidence suggests first permanent Maori settlement in New Zealand only 700 years ago (not 1200 years)

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Klasies River Mouth 120,000 - 84,000 ya

Australia has been occupied for at least 50,000 years. New genomic evidence (yet to be corroborated) indicates that the ancestors of Aboriginal Australians left Africa about 24,000 years before the later migration wave that populated Asia and Europe.

Malakunanja II 50,000 ya

1. (a) Study the map above and suggest why humans reached Australia before they reached Western Europe, even though Australia is further away from their point of origin:

(b) Suggest why New Zealand was one of the last land masses populated by humans:

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The movement of humans into new parts of the world has often been cited as the major reason for the extinction of the many large animals that lived around 40,000 to 15,000 years ago, such as the woolly mammoth. The loss of megafauna is often correlated with the arrival of humans. However, other evidence suggests climate change near the end of the last glaciation was the major factor in the extinction of these animals. Also, good evidence of mammoth hunting is relatively difficult to find, suggesting humans did not play a big part in their extinction. As with many aspects of studying ancient humans, the answer is open to debate.

Earliest modern humans travelled across what is now the Bering Strait, via the temporary ice-age land bridge to the Americas between 20,000 and 15,000 years ago

Hawaii

Iceland

The latest mtDNA analysis suggests three migrations into the Americas. The first 15,000-18,000 years ago along the western coast into South America, the second 10,000 years ago into North America, and the third 4,000 years ago along the northern coast into Greenland.

A coastal Atlantic route has also been proposed for the populating of the Americas. In this model, inhabitants of Western Europe would have travelled along the southern margins of the Atlantic sea ice to the Americas. The argument is based on similarities between the Solutrean tool culture of ice age western Europe and the tool culture of the Clovis people of America (above).

KEY

Region covered by ice or tundra in the last ice age

Over land migration route

Coastal migration / island hopping

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Polynesia populated progressively between 4500 - 700 years ago

2. Using examples, discuss the importance of land bridges and glaciations in the global dispersal of modern humans:

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175 New Findings: Denisovans

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Key Idea: DNA evidence suggests that early modern humans interbred with a previously unknown Homo species. The finding of fragments of bone and teeth in a cave in Siberia indicated that another, until then unknown Homo species once

lived in Asia. The Denisovans, (after the cave in which the fossils were found) have yet to be assigned a species name. They are sometimes called Homo sapiens ssp. Denisova.

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The Denisova cave finds

ffIn 2008, archeologists discovered a fragment of finger

bone in the Denisova cave, in Siberia. The bone fragment belonged to a juvenile female (named X-woman).

ffArtefacts, such as a bracelet, were found at the same level as the finger bone.

ffIn 2010, a molar tooth was found at a different level to the

finger bone, indicating it belonged to a different individual. A toe bone found in 2011 was at the same level as the tooth.

ffThe molar found in the Denisova cave has unique

characteristics, which are not present in the molars of Neanderthals or modern humans.

ffCarbon dating estimates the age of the artefacts and bone fragment at 40,000 years.

temperature and in acidic soil conditions. The cool temperatures within the Denisova cave preserved the DNA in the fossil fragments. The fossils contained very low levels of DNA contamination from other organisms.

The Denisova cave, in the Altai mountains, Siberia, Russia

Using genome analysis to classify the Denisova cave fossils African French

Han Chinese

Possible interbreeding ~100,000 years ago

Interbreeding

Melanesian

Interbreeding

~40,000 years ago

~60,000 years ago

Denisova

?

~400,000 years ago

Vindija Neanderthal

~300,000 years ago

Source: New Scientist 13 Aug 2011

Nuclear DNA analysis suggests the Denisova fossils belong to a previously unknown hominin species that existed at the same time as modern humans and Neanderthals, but was genetically distinct from them (above). The fossils are called the Denisovans, because they have not yet been formally classified.

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Nuclear genome analysis suggests the Denisovans were a sister group to the Neanderthals. They probably shared a more recent common ancestor with Neanderthals (~300,000 years ago) than with present day humans (~400,000 years ago). The Denisovan's interbred with the ancestors of the present day Melanesian's (right), and possibly with the Neanderthals, but not the ancestors of other present day populations, such as the Han Chinese. Melanesian DNA includes between 4% and 6% Denisovan DNA.

1. Why are the Denisovans difficult to classify?

A Melanesian women

2. (a) What modern human lineage appears to have interbred with the Denisovans:

(b) What percentage of DNA does this lineage appear to share with the Denisovans?

3. Why was the Denisovan DNA in remarkably good condition?

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Obersachse

ffFossil DNA degrades quite rapidly with increasing


251

176 New Interpretations: The Neanderthals closest relative to modern humans, so there is considerable interest in mapping the Neanderthal genome. By comparing the Neanderthal genome to the genome of present-day humans, it may be possible to identify genes in modern humans that have been influenced by positive selection.

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Key Idea: New, more complete analysis of Neanderthal DNA is revealing multiple interbreeding events with early humans. Neanderthals appeared about 400,000 years ago, and disappeared 25,000-30,000 years ago. They lived in Europe and parts of western and central Asia. Neanderthals are the

Front view Neanderthal skull

Image: Bone clones

La Ferrassie Neanderthal skull, France

Difficulties in analysing Neanderthal DNA ffThe DNA is often degraded to small fragments less than 200 base pairs

long. This makes it difficult to obtain sequence overlaps (critical for assembly of the genome).

ffThe DNA is often of poor quality because it has been chemically modified and degraded by the environment.

95-99% of the DNA obtained from the Neanderthal fossils analysed was from microbes that colonised the bone after the Neanderthal died. Researchers must be careful not to contaminate the sample with their own DNA.

What has been found?

The Neanderthal legacy

The continuing analysis of Neanderthal (and Denisovan) DNA has found that there were at least five interbreeding events between humans (H. sapiens), Neanderthals, and Denisovans.

ffBetween humans and Neanderthals. Analysis shows that

Analysis of Neanderthal DNA published in 2016 suggests that they carried various mutations that made them up to 40% less reproductively fit than modern humans. When interbreeding occurred with humans, some of these mutations would have been passed to the human gene pool. Over time most of the harmful mutations were discarded through natural selection, but some have remained. Other genes that may have been beneficial also entered the gene pool. However the benefits that these genes once conferred may no longer exist as the human lifestyle becomes more sedentary and diets change.

ffSome human populations that migrated east across Eurasia

Studies matching health problems to Neanderthal DNA have found that genetic variants inherited from Neanderthals are linked to an increase in the risk of heart attacks, depression, skin disorders, and nicotine addiction. However, the Neanderthal DNA may not necessarily be causing the health problem. It might just be associated with human DNA that is.

ffBetween archaic humans and Neanderthals. Analysis in

2016 shows there may have been an interbreeding event around 100,000 years ago when an early wave of humans migrating out of Africa met a group of Neanderthals migrating from Europe to Asia. between 1-4% of the genomes of people outside of Africa is derived from Neanderthals (more than for Africans). It is thought these encounters may have occurred as humans migrated out of Africa around 50,000 - 60,000 years ago and met Neanderthal populations already in the Middle East. interbred with the Denisovans. Evidence of this in found in Melanesian DNA (see opposite).

ffDenisovans also interbred with Neanderthals, probably about 50,000 years ago (see opposite).

ffDenisovans interbred with an unknown group of hominins,

possibly an offshoot of H. erectus, about 100,000 years ago.

Some genes that were possibly inherited from Neanderthals or Denisovans have provided benefits. Tibetans appear to have inherited Denisovan genes that enabled high altitude adaptation. Humans may also have inherited genes associated with immunity to new diseases found outside of Africa, but already encountered by Neanderthals.

1. What percentage of Neanderthal DNA is present in modern humans?

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NIH

ffSamples are often contaminated with the DNA of other organisms. Between

DNA being extracted from a Neanderthal fossil

2. In which group of modern humans is Neanderthal DNA mostly found and why?

3. Describe some possible positive and negative effects of Neanderthal DNA in modern humans:

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177 Problems With Interpretation: H. floresiensis floresiensis, thought to have lived on the island as recently as 18,000 years ago. However, revised dates in 2016 indicate that H. floresiensis lived ~190,000-50,000 years ago. The new date is close to the time that modern humans reached the area, suggesting that encounter with H. sapiens may have contributed to the demise of the Flores population.

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Key Idea: The discovery of Homo floresiensis has proved highly controversial with several hypotheses proposed to explain its position in hominin evolution. In 2003, hominin fossils, including an almost complete skeleton, were discovered on the island of Flores, Indonesia. The fossils were assigned to a new species, Homo

Homo floresiensis was very small and fully bipedal. Although the brain was very small, its organisation was advanced and stone tools associated with the skeleton indicated well established hunting technology. In contrast to these features, aspects of the skeleton showed primitive features found only in apes and early hominins. H. floresiensis probably lived 190,000 to 50,000 years ago. Its discovery caused widespread controversy and several opposing hypotheses were put forward to explain its place in human evolution. Since its discovery, earlier fossils dating to 700,000 years old have been found.

Different interpretations of the fossils

Brain size: Very small, only 380 cc.

The discovery of Homo floresiensis caused a storm of controversy, not helped by the fact that the specimens were removed from their repository by one palaeontologist, kept from other scientists for three months, and returned damaged. The Indonesian government also denied scientists access to the cave where the fossils were found for two years. Several hypotheses were eventually put forward to explain how such a small statured hominin evolved or survived. These included:

3D scans showed expansion of the prefrontal cortex and temporal lobes, brain regions associated with complex thought.

Facial features: Relatively modern dentition, but teeth are large relative to the rest of the skull.

ffH. floresiensis evolved a result of island dwarfism. Island

dwarfism is a relatively common occurrence where large animals become smaller over time when isolated, e.g. the extinct pygmy elephants on Flores showed this adaptation.

No chin present.

ffH. floresiensis is not a new species but instead an individual with a disease or disorder. Some scientists put forward the idea that the small skull was a result of microcephaly, a neurodevelopment disorder. Others thought that perhaps H. floresiensis suffered from congenital hypothyroidism.

ffDetailed examination of the bones showed no overlap with

C aC yn

ail

Sc

4.0

Homo floresiensis

Homo sapiens

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any features expected from individuals with the diseases or disorders listed above. A study of the bones and joints of the arm, shoulder, and lower limbs concluded that H. floresiensis was more similar to early humans and apes than modern humans. Small brain size coupled with more advanced brain organisation indicate possible parallel evolution of sapiens-like features.

1. Explain the effect that the Flores finds had on the hypothesis that hominins continually evolved larger brains and bodies:

2. Describe the different interpretations of the H. floresiensis bones:

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177 149 151

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Rosino

The fossils were discovered in Liang Bua, a limestone cave on Flores Island, Indonesia. The cave contains 12 m of stratified deposits. The remains of modern humans, as well as Homo floresiensis, have been found in the cave.


253

178 Dating a Prehistoric Site modern human remains. It illustrates the way human activity is revealed at archaeological excavations. Occupation sites included shallow caves or rocky overhangs of limestone. The floors of these caves accumulated the debris of natural rockfalls, together with the detritus of human occupation at various layers, called occupation horizons. Accurately dating these finds is important to understanding their significance.

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Key Idea: A wide array of techniques can be used for dating artefacts, some of which show a high degree of reliability. The use of several appropriate techniques to date material improves the reliability of the date determined. The diagram below shows a rock shelter typical of those found in the Dordogne Valley of Southwest France. Such shelters have yielded a rich source of Neanderthal and

Dating method

Rock shelter used by early humans

Enlarged below

Dating range

Datable materials

(years ago)

Radiocarbon (14C)

1000 - 50,000+

Potassium-argon (K/Ar)

10,000 - 100 million

Volcanic rocks and minerals

Uranium series decay

less than 1 million

Marine carbonate, coral, shell

Thermoluminescence

less than 200,000

Ceramics (burnt clay)

Fission track

1000 - 100 million

Volcanic rock, glass, pottery

Electron spin resonance

2000 - 500,000

Bone, teeth, loess, burnt flint

Bone, shell, charcoal

Limestone cave formations can be dated using uranium series decay measurements. This method can be used to date calcite deposits up to the age of 300,000 years. Rock fall from the roof of the overhanging shelter.

Occupation horizon A, with evidence of an ancient hearth in its uppermost layer.

A

Occupation horizon B, with evidence of a human burial.

B

Zone without any evidence of human occupation.

Charcoal

Bones Skull of an early human but unable to directly determine its age.

1. What is the significance of occupation horizons?

Hearth The remains of an ancient fireplace was dated at 18,500 ± 1000 years old.

Tooth A bison's tooth was dated at 45,000 ± 2500 years old.

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Pottery Pottery bowl dated at 7000 ± 350 years old.

2. Determine the approximate date range for the items below (Hint: take into account layers/artefacts with known dates):

(a) The skull at point B:

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254

Interpreting Fossil Sites Charcoal fragments (possible evidence of fire use and excellent for radiocarbon dating).

Photo: RA

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Human skull

Bones from a large mammal with evidence of butchering (cut and scrape marks from stone tools). These provide information on the past ecology and environment of the hominins in question.

Excavation through rock strata (layers). The individual layers can be dated using both chronometric (absolute) and relative dating methods.

Stone tools

istock

Searching for ancient human remains, including the evidence of culture, is the work of palaeoanthropologists. Organic materials, such as bones and teeth, are examined and analysed by physical anthropologists, while cultural materials, such as tools, weapons, shelters, and artworks, are examined by archaeologists. Both these disciplines, palaeoanthropology and archaeology, are closely associated with other scientific disciplines, including geochemistry (for chronometric dates), geology (for reconstructions of past physical landscapes), and palaeontology (for knowledge of the past species assemblages). The reconstruction of a dig site, pictured above, illustrates some of the features that may be present at a site of hominin activity. Naturally, the type of information recovered from a site will depend on several factors, including the original nature of the site and its contents, the past and recent site environment, and earlier disturbance by people or animals. During its period of occupation, a site represents an interplay between additive and subtractive processes; building vs destruction, growth vs decay. Organic matter decays, and other features of the site, such as tools, can be disarranged, weathered, or broken down. The archaeologists goal is to maximise the recovery of information, and recent trends have been to excavate and process artifacts immediately, and sometimes to leave part of the site intact so that future work, perhaps involving better methodologies, is still possible.

3. Which dating method or methods could have been used to date each of the following, at the site on the previous page:

(a) Pottery bowl:

(c) Hearth:

(b) Skull:

(d) Tooth:

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4. Explain why palaeoanthropologists date and interpret all of the remains at a particular site of interest (e.g. animal bones, pollen, and vegetation, as well as hominin remains):

5. Outline the importance of involving several scientific disciplines when interpreting a site of hominin activity:

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179 Problems with Dating: H. naledi dozens of teeth. Interestingly, no other types of animal or plant have been found in the cave and there is no indication of water flowing in the past. This has led the investigators to hypothesise that the bodies were deliberately placed there by other Homo naledi. Also the lack of other flora or fauna and sediments (other than cave dust) has made it very difficult to date the fossils. They have both advanced and primitive features, which some think puts them at the cusp of the transition between Australopithecus and Homo.

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Key Idea: The discovery of Homo naledi presents problems. The placement of the bones appears deliberate, which seems unlikely for an ancient hominin, and they are difficult to date because there are no dateable sediments around them. In 2013 two cavers exploring the Rising Star cave system near Johannesburg in South Africa found a passage that led to a chamber containing the bones of a new hominin species. Excavation has found more than 1500 specimens from at least 15 individuals including ribs, skulls, jaws, and

The Rising Star cave system

Cave entrance

Superman's crawl may have been higher in the past, allowing easier access.

Bodies were probably dropped down the shaft over a long period of time (maybe centuries)

Dinaledi chamber

Dragonâ&#x20AC;&#x2122;s back

10 metres

Supermanâ&#x20AC;&#x2122;s crawl (less than 25 cm high)

Fossil find

Dating Homo naledi ffDating the Homo naledi bones is problematic because they

were found deep in the cave. Ordinarily, fossils can be dated by relative dating. Other fossils in the sediment can be used to date the unknown fossils. For example, if the bones of a predator species of a known age had been found in the cave, then it may imply that H. naledi lived at the same time. However, only H. naledi bones have been found, expect for a few small birds on the surface. Radiocarbon dating cannot be used because it only dates accurately to 50,000 years of age and H. naledi is likely to be much older than that.

ffIf the bones had been washed into the cave by a river

tried, such as measuring parts of the skull and teeth and comparing them to other hominin fossils. These techniques have put the age of the bones at ~1-3 million years old.

No Cla t fo ssr r o Us om e

ffVarious anatomical ways of dating the fossils have been

Lee R Berger CC 4.0

system it may have been possible to use the sediments deposited or other bones that had been washed in to provide a date. The excavation team has yet to find any evidence of a river or water flow. One other way of dating the bones is by dating the flowstones found in the cave. Flowstones are sheets of calcium carbonate built up by water flowing down cave walls (similar to stalactites). However the flowstones do not cover much of the cave floor and fossils.

1. Describe one of the problems in explaining the deliberate placement Homo naldei bones in the Dinaledi chamber.

2. Describe two reasons why dating the H. naledi bones is difficult:

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180 What You Know So Far: Patterns of Dispersal New finds and controversies

HINT: Interpretations of new finds and their significance.

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Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you: The origins of humans

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HINT: Out-of-Africa or multiregional? Evidence for each.

REVISE

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181 NCEA Style Question: Patterns of Dispersal 1. Two important models for human dispersal are the out-of Africa model and the multiregional model. Africa

Asia

Europe

Africa

Asia

Evidence from stone tools suggests Homo erectus reached China 1.27 million years ago. The most recent fossil finds suggest it remained there until 143,000 years ago.

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Europe

African origin

Multiregional model

African origin

Out-of-Africa model

Analysis of DNA from the Y chromosome indicates that all living males today are related to a man that lived between 140,000 and 500,000 years ago, probably in Africa.

Discuss which of the models for human dispersal (shown above) the data support. In your answer you should: • describe the out-of-Africa and muliregional models • explain what the data above suggests about the dispersal of the genus Homo • discuss how the data supports (or does not support) the models above You may use more paper if required.

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Analysis of mitochondrial DNA shows there are 6 different groups within the human population. Only one of these groups, L3, is found outside of Africa. L3 is believed to have arisen about 100,000 years ago.

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182 A Summary of Trends in Hominin Evolution (below and on page 261). Add notes about significant developments and trends. Notes may include information about the tool technology (including the main user of the tool), skull features and brain size, bipedalism, how food and diet influenced dentition, and hominin distribution.

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Key Idea: Specific trends can be seen in human physical (biological) and cultural evolution. Use this activity to revise your knowledge about trends in human evolution. Cut out the images on page 259 and place them in their correct place on the timeline of human evolution

Millions of years ago

3

2

Skull and body features

Jaw shape

Brain size and features

REVISE

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Tools

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Homo neanderthalensis

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Australopithecus afarensis

Mean brain volume 1335 cm3

Mean brain volume 1512 cm3

Homo habilis

Mean brain volume 1250 cm3

Homo erectus

Mean brain volume 457 cm3

Mean brain volume 552 cm3

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Homo heidelbergensis

Mean brain volume 1016 cm3

Homo sapiens

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This page has been deliberately left blank

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1

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2

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183 Scholarship Question: Return of the Dodo Could species become de-extinct? Extinction is part of the evolution of life. The loss of an organism leaves a vacant niche and provides the opportunity for another organism to evolve into that ecological space. The rate of natural (or background) extinction is about 0.1 species per million years. The extinction rate over the last 400 years is estimated to be around 1000 times greater than this. This is because human activity since 1600 AD has directly or indirectly caused the extinction of over 400 known species. These include the dodo, the moa, the Tasmanian tiger, and more.

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Technology has now developed to the point that DNA can be extracted from the 30,000 year old bones of Neanderthals. Technology also now enables animals to be routinely cloned. Many organisms on the brink of extinction are now having DNA, sperm, and egg samples cryogenically frozen to preserve them in the event of their extinction in the near future. The hope is that technology will enable the organism to be cloned and so return to the world in the future. Many argue that now, with the ability to extract DNA from fossils and to clone animals, some of the animals that were exterminated by humanity should be returned to the world (de-extinction). There has been only one case of de-extinction. The Pyrenean ibex was a subspecies of Spanish ibex. It became extinct in 2000. Scientists used DNA from the last female to create 285 cloned embryos that were implanted into Spanish ibex. In July 2003, one clone survived to birth, but died after only a few minutes due to lung defects. The dodo (Raphus cucullatus) is a possible candidate for de-extinction. Endemic to the island of Mauritius, the dodo was first recorded in 1598 and was exterminated by 1662 so completely that only one complete skeleton exists and no complete specimen is known. Scientists are not even sure what the dodo looked like because of the variation in sketches by 17th century artists. However enough DNA has been extracted from bone that the genetic relationship of the dodo to other birds has been identified.

Phylogeny of the dodo

Victoria crowned pigeon

Nicobar pigeon

Rodrigues solitaire (extinct)

Dodo (extinct)

J. Patrick Fischer CC 4.0

The flightless dodo stood about 1 metre tall and weighed between 10 and 20 kilograms. Only one egg exists and its authenticity is in dispute. The dodo egg, apparently, is larger than an ostrich egg.

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Tooth-billed pigeon

The Nicobar pigeon measures about 40 cm long and weighs about 500 grams. It lives in coastal regions of Andaman and Nicobar Islands, India. Its egg is about the size of a chicken's egg.

1. Analyse the information provided and integrate it with your biological knowledge to discuss: • • •

The evolutionary and ecological factors that contribute to declining populations and increasing rates of extinction. Use examples to support your discussion. How humans could manipulate the transfer of dodo DNA to restore a population of dodos to Mauritius and the possible biological implications of doing this. Justify your opinion on whether restoring extinct organisms is a possibility.

You may use extra paper if needed.

TEST

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184 Scholarship Question: Stickleback Speciation Speciation in three-spined sticklebacks The three-spine stickleback (Gasterosteus aculeatus) are freshwater fish found above 30° north in marine and freshwater environments. It has been the subject of many scientific studies for many reasons including its breeding behaviour, varied morphology, and population genetics. The three spined-stickleback may be anadromous, migrating from the sea to lakes or they may be entirely restricted to fresh water.

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In British Columbia (Canada) there are a five lakes that contain two forms of stickleback (known as stickleback species pairs). They remain in the lake throughout their life cycles. There is a limnetic form that lives in the shallows and feeds on free-swimming plankton and a benthic form that lives deeper in the lake and feeds on prey in the lake sediment. Studies of these two forms from the five different British Columbia lakes have found the following:

ffMitochondrial DNA analysis shows that the benthic and limnetic forms in each lake are more closely related to each other than to sticklebacks in other lakes.

ffThe two forms never mate with each other.

ffThe benthic forms in one lake will spawn successfully with the benthic forms in another lake, and the limnetic forms in one lake will spawn successfully with the limnetic forms in another lake.

ffA benthic form will display to benthic forms of stickleback from Japan.

ffAnalysis of nuclear DNA shows the limnetic forms in all 5 lakes are more related to each other (and marine lineages) than to benthic forms.

ffSampling of the lakes over three years produced frequencies of three forms of stickleback: Year

Total fish in sample

Frequency of benthics

Frequency of limnetics

Frequency of F2 hybrids

1

1057

0.50

0.48

0.019

2

962

0.50

0.49

0.010

3

994

0.49

0.49

0.014

ffExperiments into the selection factors in the three-spined stickleback bred limnetic forms with benthic forms by artificially

fertilising eggs from one form with sperm from another (and vice-versa), producing a population of hybrid fish. The fish were introduced into an artificial pond and left to interbreed. Measurements and observation of the second generation of hybrids were then taken. It was found that the second generation (F2) hybrids were sorting into benthic and limnetic niches. Those fish that were at the extremes of this sorting (they spent all their time either feeding on free swimming prey or bottom dwelling prey) grew faster than those that ate a mixture of prey.

1. Analyse the information presented. Justify whether the benthic and limnetic forms are separate species and establish a justified speciation history of the three-spined stickle back. Your justification should include:

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• Evidence for and against speciation • Factors that influence speciation • A justified history of the formation of the benthic and limnetic forms

TEST

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Appendix

Questioning terms in biology

Birth weight data for activity 85

The following terms are often used when asking questions in examinations and assessments.

The birth weights for 100 babies are displayed below.

Interpret data to reach stated conclusions.

Annotate:

Add brief notes to a diagram, drawing or graph.

Apply:

Use an idea, equation, principle, theory, or law in a new situation.

Calculate: Find an answer using mathematical methods. Show the working unless instructed not to.

Compare: Give an account of similarities between two or more items, referring to both (or all) of them throughout.

Construct: Represent or develop in graphical form. Contrast:

Show differences. Set in opposition.

Define:

Give the precise meaning of a word or phrase as concisely as possible.

Derive:

Manipulate a mathematical equation to give a new equation or result.

Describe: Define, name, draw annotated diagrams, give characteristics of, or an account of. Design:

Produce a plan, object, simulation or model.

Determine: Find the only possible answer. Discuss:

Show understanding by linking ideas. Where necessary, justify, relate, evaluate, compare and contrast, or analyse.

Distinguish: Give the difference(s) between two or more items. Draw:

Represent by means of pencil lines. Add labels unless told not to do so.

Estimate:

Find an approximate value for an unknown quantity, based on the information provided and application of scientific knowledge.

Evaluate:

Assess the implications and limitations.

Explain:

Provide a reason as to how or why something occurs.

Identify:

Find an answer from a number of possibilities.

Illustrate:

Give concrete examples. Explain clearly by using comparisons or examples.

Interpret:

Comment upon, give examples, describe relationships. Describe, then evaluate.

List:

Give a sequence of answers with no elaboration.

Measure:

Find a value for a quantity.

Outline:

Give a brief account or summary. Include essential information only.

Predict:

Give an expected result.

Solve:

Obtain an answer using numerical methods.

State:

Give a specific name, value, or other answer. No supporting argument or calculation is necessary.

Suggest:

Propose a hypothesis or other possible explanation.

3.740 3.830 3.530 3.095 3.630 1.560 3.910 4.180 3.570 2.660 3.150 3.400 3.380 2.660 3.375 3.840 3.630 3.810 2.640 3.955 2.980 3.350 3.780 3.260 4.510 3.800 4.170 4.400 3.770 3.400 3.825 3.130 3.400 3.260 4.100 3.220 3.135 3.090 3.830 3.970 3.840 4.710 4.050 4.560 3.350 3.380 3.690 1.495 3.260 3.430

Summarise: Give a brief, condensed account. Include conclusions and avoid unnecessary details.

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3.510 3.230 3.570 3.620 3.260 3.315 3.230 3.790 2.620 3.030 3.350 3.970 3.915 2.040 4.050 3.105 3.790 3.060 2.770 3.400 1.950 3.800 2.390 2.860 4.110 1.970 3.800 4.490 2.640 3.550 4.050 4.220 2.860 4.060 3.740 4.082 3.000 3.230 2.800 4.050 4.300 3.030 3.160 3.300 2.350 3.970 2.980 3.550 3.070 2.715

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Analyse:

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Photo Credits

We acknowledge the generosity of the following individuals and organisations who have provided photographs for this edition: • Cereal Research Centre, AAFC for their photograph of a pheromone trap • Rogan Colbourne for his photograph of North Island kokako • Scott McDougall for the photographs of New Zealand falcon and the pukeko with chick • Andrew Dunn for the banded snail photographs • Alex Wild for his photograph of swollen thorn Acacia • Missouri Botanical Gardens for their photograph of egg mimicry in Passiflora • California Academy of Sciences for the photo of the ground finch • Mike Meads for the use of his excellent photographs of the Superb and Gillies giant land snails • Rocky Mountain Laboratories, NIAID, NIH • The late Dr. M Soper, for his photograph of the waxeye • Tony Northrup for the photo of the chimpanzee • www.skullsunlimited. com for some of the hominin skulls • Grotte de Rouffignac, for drawings and photographs of the Rouffignac Cave • April Nobile www.AntWeb.org for the photo of the slavemaker ant • Landcare research for the photo of the German wasp • Peter Bray, Airborne Honey Ltd for the picture of anal tubes of beech scale insects • C.R. Veitch, DoC for short-tailed bat photo • J. Barkle, DoC for photo of Dactylanthus taylorii • Jenny Ladley (University of Canterbury) for the photographs of the tui and the bellbird in mistletoe • Professor Jeff Podos, Biology Department, University of Massachusetts Amherst for his photographs of Galápagos finches • Melicytus photos were generously supplied by John Barkle, Jeremy Rolfe, Melissa Hutchinson, and Bruce Clarkson. We are also grateful to Rewi Elliot and the NZ Plant Conservation Network for helping to obtain the Melicytus images.

Contributors identified by coded credits are: CDC: Centers for Diseases Control and prevention, Atlanta, USA, DoC: Department of Conservation (NZ), DoC-KW: K Walker, DoC-RM: Rod Morris, DoC-VV: V. Vercoe, F&B: Forest and Bird Society (NZ), LBS: Lissa Bainbridge-Smith, MM: Mike Meads, NASA: National Aeronautics and Space Administration, NIH: National Institute for Health, NOAA: National Oceanic and Atmospheric Administration, RA: Richard Allan, TM: Tracy Montford, USDA: United States Department of Agriculture. We acknowledge our use of royalty-free images, purchased by BIOZONE International Ltd from the following sources: iStock images, Dollar Photo Club, Corel Corporation from various titles in their Professional Photos CD-ROM collection; IMSI (International Microcomputer Software Inc.) images from IMSI’s MasterClips® and MasterPhotosTM Collection, 1895 Francisco Blvd. East, San Rafael, CA 94901-5506, USA; ©1996 Digital Stock, Medicine and Health Care collection; ©Hemera Technologies Inc, 1997-2001; © 2005 JupiterImages Corporation www.clipart.com; ©1994., ©Digital Vision; Gazelle Technologies Inc.; ©1994-1996 Education Interactive Imaging (UK), PhotoDisc®, Inc. USA, www.photodisc.com; Bone clones for some skull images. We also acknowledge the following clipart providers: TechPool Studios, for their clipart collection of human anatomy: Copyright ©1994, TechPool Studios Corp. USA (some of these images have been modified); Totem Graphics, for clipart; Corel Corporation, for vector art from the Corel MEGAGALLERY collection.

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We also acknowledge the photographers that have made their images available through Wikimedia Commons under Creative Commons Licences 2.0, 2.5., 3.0, or 4.0: • AKA • Bjorn Christian Torrissen • Alvesgaspar • Stan Shebs • Kristian Peters • Orikirin 1998 • Lazaregagnidze • Chriwick Chap • Tangopaso • Melodi2 • Coolstock • Thergothon • Heuchera • Michael (inski) • Rudolph89 • Brocken Inaglory • Brian Gratwicke • Artfarmer • Greg Hume at en.wikipedia • ATamari • Adrian A. Smith • Kalyan Varma • Alex Wild • Karora • Graham Collins • Onno Zweers • flowergarden@noaa.gov • small • Charlesjsharp • Snake3yes • Jo Naylor • it:Utente:Cits • Art G • Rosino • Olaf Leillinger • Omasz G. Sienicki • JM Garg • David M. Green • Bruce Marlin • Lorax • Kirt L Onthank • Taollan82 • Velela • Duncan Wright • Bjorn schultz • Xiangyux • Emw • Ghedoghedo • Petit Deuxmont • Matt Binns • Didier Descouens • Guerin Nicolas • Ji-Elle • Brett Eloff • José-Manuel Benito • Don Hitchcock • Sandstein • Dr. John F. Burka • Obersachse • Lee R Berger • J Patrick Fischer

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Index Classification, primates 200 Clothing, and human evolution 236 Coevolution 148 Colonisers, oceanic island 179-180 Common ancestor 145 Communication methods 66 Communication 65-67 - bees 18 - evolution of 239 - pheromones 9 Competition 52, 59-60 - intraspecific 80 Conflict behaviour 78 Conserved protein 187 Continental drift, and evolution 181 Convergent evolution 146-147 Cooperative behaviour 71-77 Core area 86 Courtship 90-91 Crepuscular activity 38 Cultural evolution 230-242 Cytochrome c 189

Evolutionary processes 111 Exogenous rhythm 36 Exploitation 52, 58 External cue 36

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A Abscission 44 Absolute dating 253 Acheulean tools 232 Activity patterns 41-43 Activity patterns, types 38 Actograms 41-43 Adaptation 114 Adaptations - for bipedalism 216-217 - NZ parrots 114 Adaptive behaviour 3 Adaptive radiation 150-151, 185 - Darwin's finches 180 - Hebe 164 - ratites 152 - wrens 162-163 Aggressive behaviour 78 Agonistic behaviour 78 Agriculture, and human evolution 241 Agriculture, development of 231 Allelopathy 22 Allopatric speciation 132, 135 Allopolyploidy 136, 138-140 Altruistic behaviour 71-72 Analogous structures 146 Animal behaviour record 68 Animal communication 65-67 Annual rhythms 33 Archaea, domain 169 Archaeopteryx 175 Ardipithecus 220-221 - Ar. kadabba 206 - Ar. ramidus 206-207, 213-214, 219 Art, and human evolution 237-238 Astronomical cycles 33 Attack behaviour, cooperative 76 Australopithecus 204, 220-221 - A. afarensis 204, 206-207, 209, 212, 218, 220 - A. africanus 206-207, 221 - A. anamensis 206 - A. bahrelghazali 206 - A. garhi 206 - A. sediba 206-207 Autopolyploidy 136 Auxin 24-25

C Carrying angle 216 Cave painting 237-238 Chloroplasts, origin 168 Circadian rhythms 36, 38 Circadian rhythms, NZ birds 38 Circalunar rhythm 36 Circannual rhythm 36 Circatidal rhythm 36

G GalĂĄpagos islands 179-180 Gamete isolation 129 Gause's competitive exclusion principle 59 Gene duplication 109-110 Gene flow 111 Genetic bottleneck 113 Genetic code 168 Genetic drift 111, 113 Genetic switches 192 Genetic variation 111 Genotype 103 Geographical barriers 128,132 Geographical isolation 128, 132 - and New Zealand speciation 157-161 Geological history, New Zealand 155-156 Gondwana 155 Gradualism 154 Gravitropism 23, 25-26

D Daily rhythms, humans 39 Daily rhythms, plants 45 Darwin's finches - adaptive radiation 180 - natural selection 118-119 Dating methods 253-254 Dating, relative 173 Day length, plant responses to 47 Defensive behaviour, cooperative 75 Denisova cave 250 Denisovan hominin 206, 225, 250 Dentition, trends in human 212 Developmental biology 191 Diastema 202 Directional selection 115, 117-118 Dispersal 11 Dispersal patterns, human 248-249 Disruptive selection 115, 119 Diurnal activity 38 Divergent evolution 145 Divergent evolution, ratites 152 DNA hybridisation 190 DNA, and human evolution 250-251 Dominance hierarchies 78, 82, 84, 85 Dormancy, plants 44

E Ecological isolation 128 Embryological evidence, for evolution 191 Endogenous rhythm 34-35 Endogenous rhythm 36, 39 Entrainment 35, 43 Environmental cue 34 Ethogram 67 Eukarya, domain 169 Eusocial 70 Evo-devo 192 Evolution 111 - and continental drift 181 - and gene duplication 109-110 - convergent 146-147 - cultural 230-242 - Darwin's finches 118-119, 180 - divergent 145 - evidence for 170 - Hebe 164 - horses 176 - human trends 204-205 - New Zealand invertebrates 157-159 - New Zealand parrots 160-161 - novel forms 192 - rate of change 154 - whales 177, 186

H Habitat isolation 128 Haemoglobin mutation 106-107 Harmful mutation 104, 106-107 Hebe evolution 164 Herbivory 52 Heterozygous advantage 107 Hierarchies 78, 80, 82, 84, 85 Home range 86-88 Homing behaviour 20-21 Hominidae 200 Hominin definition 200 Hominin features 219-226 Hominini 200 Hominoid definition 200 Hominoidea 200 Homo 204-205, 222-226, 251-252, 255 - H. antecessor 206, 225 - H. erectus 204, 206-207, 209, 212, 224 - H. ergaster 206-207, 223 - H. floresiensis 206-207, 224, 252 - H. georgicus 206, 223 - H. habilis 204, 206-207, 209, 212, 222 - H. heidelbergensis 206-207, 225 - H. naledi 206, 255 - H. neanderthalensis 205-207, 209, 226, 251 - H. rudolfensis 206 - H. sapiens 205-207, 209, 212, 226 Homologous proteins 187-188 Homologous structure 185 Homology, anatomical 185 Homology, DNA 190 Homology, protein 187-188 Horse evolution 176 Human biological clock 34

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B Bacteria, domain 168 Balanced polymorphism 107 Behaviour 3, 68-78 Behaviour, record 68 Behavioural isolation 129 Beneficial mutation 104-105 Biogeography 178 Biological clocks 34-35 Biological rhythms 36-40 - human 39-40 Biological species 125 Bipedalism, in hominins 215-217 Brain, human 239 Brain, volume of hominins 210-211 Breeding behaviour 90-91 Breeding territories 95 Broca's area, in human speech 239 Brood parasites 92

F Facultative mutualism 55 Fire, use of 235 Fitness 90, 103, 114 Fixed action pattern 65 Food gathering, cooperative 77 Foraging, ants 18 Foraging, cooperative 77 Foramen magnum 208 Fossil 171-172 Fossil record 173 Fossil, transitional 175-177 Fossils, role in dating 173, 253-255 Founder effect 113 Free-running period 41, 43 Fruit fall 44

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272 New Zealand birds - adaptation 114 - competition 59 - migration 14, 17 - speciation 145, 160, 162 New Zealand plants - polyploidy 139 - speciation 139, 164 New Zealand, geological history 155-156 New Zealand, speciation 157-161 Niche differentiation 59, 138 Nocturnal activity 38 Non-disjunction 137 Novel forms, evolution of 192

Seed germination 44 Selection pressure 103 Shelters, human use 236 Short-day plants 47 Sickle cell disease 106-107 Silent mutation 104 Skeleton, adaptations for bipedalism 216-218 Skin colour, humans 120 Skull, human 203 - primate features 202-203 - trends 208-209 Sleep movements, plants 28, 45 Social behaviour and survival 73-74 Social groups, types 69 Social organisation 70 Speciation, defined 132 - allopatric 132-135 - by polyploidy 136, 140-141 - in New Zealand 145, 157-164 - sympatric 138-140 Species formation, stages in 135 Species interactions 3, 52-61 Species, definition 125 Species, Canis 125 Spirituality, and human evolution 237-238 Stabilising selection 115-116, 120 Star compass navigation 15 Stasis 154 Stimuli 4 Stone age tools 232-234 Strata, rock 173 Stratification 44 Sun compass navigation 15 Symbiosis 52 Sympatric speciation 138-140

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Human birth weight, stabilising selection 116 Human brain 239 Human dispersal, evidence 247 Human evolution 204-207 - agriculture 241 - bipedalism 215-217 - competing models 246-247 - nakedness 216 - permanent settlement 242 Human skull 203 Hybrid breakdown 131 Hybrid inviability 131 Hybrid sterility 131 Hybridisation, Melicytus 139 Hybridisation, wheat 136, 140-141 Hylobatidae 200

JK Jet lag 35 Kaka - adaptation 114 - origin 160 Kea - adaptation 114 - origin 160 Kenyanthropus platyops 206 Kin selection 71-73 Kineses 3, 5-6 Klinokinesis 5 Klinotaxis 7 L Lek system 95 Long-day plant 47 Lucy, skeleton 218

M Magnetic compass navigation 15 Malaria, and heterozygous advantage 107 Mammals, adaptive radiation in 150-151 Mating systems 94 Mechanical isolation 129 Meiosis, non-disjunction 137 Melatonin, role in sleep 34 Melicytus , evolution in 139 Mesolithic culture 240 Migration 10-17, 111 - birds 14-17 Mitochondria, origin 168 Mobbing behaviour 71 Models of human evolution 246-247 Modern human 205-207, 209, 212, 226 - dispersal patterns 248-249 Modularity, and evolution of body forms 192 Molecular clock hypothesis 189 Molecular phylogenetics 168 Monogamy 94 Mousterian tools 232 Multiregional model, human evolution 246 Mutation 104-108 Mutation 111 Mutualism 52, 54-57 N Nakedness, human evolution 216 Nastic response 3, 22, 27-28 Natural selection 107, 111, 115-120 Navigation 3 - in ants 18 - in bees 18 - in salmon 21 - mechanisms 15 - migratory birds 14-17 Neanderthal burial 237 Neanderthal interbreeding 251 Neanderthals 205-207, 209, 226, 251 Neolithic culture 241-242

PQ Palaeolithic tools 232-234 Paranthropus aethiopicus 206 Paranthropus boisei 206-207, 212, 221 Paranthropus robustus 206-207, 222 Parasitism 52, 54 Parental care 92, 94 Parrots, New Zealand 114, 160 Pentadactyl limb 185 Peppered moths, directional selection 117 Phase shift 41 Phenotype 103 Pheromones 7, 9 Photoperiodism, in plants 46-47 Phototropism 23-24 Phyletic gradualism 154 Phylogenetics 168 Phylogeny, human evolution 206-207 Phytochrome 46 Plant hormones 24-25 - in timing responses 44 Plant responses 22 Plant rhythms 22, 44-45 Polyandry 94 Polygny 94 Polygynandry 94 Polyploidy 136, 138 - in Melicytus 139 - in speciation 136, 138, 140-141 Population change 111 Postzygotic isolating mechanisms 131 Predation 52, 58 Presocial species 70 Prezygotic isolating mechanism 128-129 Primate characteristics 198, 201-202 Primate classification 200 Primate hand 201 Primate, skull features 202-203 Protein homology 187-188 Protein, conserved 189 Pukeko communication 67 Punctuated equilibrium 154

T Taxes 3, 7 Temporal isolation 128 Territories 80, 86, 89, 95 Timing behaviour 3 Tools, in human evolution 232-234 Transitional fossil 175-177 Transitional fossil, horse 176 Transitional fossil, whale 177 Trilobite, as index fossils 172 Tropism 3, 22-26 U Upper Palaeolithic tools 232 V Valgus angle 216 Variation , defined 103 Vernalisation 44 Vestigial structure 186

R Ratites, adaptive radiation 152 Relative dating 173, 254 Replacement model, human evolution 247 Reproductive effort 92-93 Reproductive isolating mechanisms 128-131 Reproductive isolation 132, 138 Reproductive strategies 92 Rhythms, plant 44-45 Ring species 126-127 Rising Star Cave 255 Round dance, bee navigation 18 S Saddlebacks, speciation in 145 Sahelanthropus tchadensis 206

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W Waggle dance, bee navigation 18 Wernicke's area 239 Whale evolution 177, 186 Wheat, speciation 136, 140-141 Woodlouse behaviour 5 Wren, adaptive radiation 162-163

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I Index fossil, use in dating 172 Innate response 3 Instant speciation 138-140 Interspecific competition 59-60 Intraspecific competition 80 Isolating mechanisms 128-132

O Obligatory mutualism 55 Occupation horizon 253 Oceanic island colonisers 179-180 Oldowan tools 232 Orientation behaviour 3-5, 7, 22-26 - round dance 77 Orrorin tugenensis 206-207 Orthokinesis 5 Out of Africa hypothesis, human evolution 247

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