Biología y geología 4 ESO. Andalucía. Dual focus

dual FOCUS

DEMO

biolo gy and geolo gy

4 SECONDARY EDUCATION www.anayaeducacion.es

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The following people have worked on this book: Content: Berta Gallego (adaptation of the material from the book Biología y Geología 4º ESO, and creation of the fact files and activities in this book).

Editorial team: Departamento de Ciencias Naturales (Almudena Alcón, Esther Fernández, Mª Isabel García, Marco Sánchez and Jorge Torres).

Design, technical drawings and maps: Patricia G. Serrano, Juan Carlos Quignón, Miguel A. Castillejo, Miguel A. Díaz-Rullo and Miriam Arribas.

Illustrations: Sara Mateos, Celia López Bacete, Santi Martín, Alicia Posada, M.ª Carmen Fuente, David Menéndez.

Layout: Artesa S.L. and Elvira López.

Corrections: Sergio Borbolla.

Translation: Rachel Bland (Bakun S.L.) Photographs: Age Fotostock (STEVE GSCHMEISSNER, SZ Photo/Süddeutsche Zeitung Photo), Alamy/Cordon Press (Adam Major, Photonesia, Susan E. Degginger, Yakov Oskanov), Archivo Anaya (Candel, C.; Canto, M.; Cosano, P.; González Grande, J. L.; Gragera, R. & Muñiz, E.; Lezama, D.; Martínez, C.; Moreno, C.; Ortega, Á.; Padura, S.; Ruiz, J. B.; Sánchez, J.; Valls, R.; Vázquez, A.), Dreamstime (Piyaphun Juntraverot, Ste-ve Ball, Sue Feldberg), Getty Images (Martin Ruegner), iStock/Getty Images (AndreAnita, aopsan, branex, Cheryl Ramalho, dr322, Elif Bayraktar, Josep Sala Francas, kingkidton, McIninch, micro_photo, Noemi Braña, scanrail, sonatali, Tom Strudley, Tramper2, travelview, Zach Etheridge), 123RF (Achim Prill, angellodeco, Dan Barbalata, jenifoto, Kevin Wells, Roman Fedin, sergiitrofymchuk, ssilver, Анастасия Короткова).

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Important information: The activities proposed in this book should be completed in a separate notebook or on sheets of paper, not in the book itself.

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Index THE SCIENTIFIC METHOD.................................................. 7

5. DYNAMIC EARTH.....................................................................53

1. CELLS: THE BUILDING BLOCKS OF LIFE.......................................................................15

6. THE HISTORY OF EARTH...................................................67

2. GENETIC INFORMATION.....................................................25 3. BIOLOGICAL INHERITANCE..............................................33 4. THE ORIGIN OF LIFE AND EVOLUTION..................................................................... 43

7. ECOSYSTEMS AND THEIR COMPONENTS...........................................................75 8. MATTER AND ENERGY IN ECOSYSTEMS.......................................................................81 9. HUMAN BEINGS AND THE ENVIRONMENT.............................................................. 91

DUAL FOCUS

du al FOCUS

k oo b r u o y f o t In this par ind... you will f

biology and geology

4

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SECONDARY EDUCATION

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cacion.es www.anayaedu

GENETIC INFORMATION

2

Scan this code to consult the glossary for this unit.

RNA which contains the

DNA

Genetic information

This section contains activities for practising and applying the key vocabulary in the unit.

which is expressed through

can be

are

Focus on English

Replicated Transcription and enables

The nucleic acids

Cell division

Regenerates cells

Translation

Mitosis

U

mRNA

forming

Proteins

The Final Challenge!

Produces gametes

Meiosis

Each unit ends with a task or challenge to help you develop your skills by applying your knowledge in a different context.

with 2 divisions

with 4 phases

• Prophase • Metaphase • Anaphase • Telophase

Vocabulary The page that shows the key vocabulary you will encounter in the unit.

forming

y

1º división meiótica

2º división meiótica

• Prophase I • Metaphase I • Anaphase I • Telophase I

• Prophase II • Metaphase II • Anaphase II • Telophase II

Focus on English 1 Listening and Speaking. Listen and repeat the words to improve your pronunciation.

2 Reading

and Writing. Use the branches of the outline to create three sentences about nucleic acids, mitosis and meiosis.

INVENT A STORY ABOUT MITOSIS

The final challenge

BANK LANGUAGE LANGUAGE BANK LANGUAGE BANK GE BANK LANGUA BANK BANK LANGUAGE LANGUAGE LANGUAGE BANK

Imagine mitosis explained as a story with a chromosome as the main character.

Work in groups. In small groups, you are going to write a short story about mitosis.

STEP

Basic exercises

1

STEP

Imagine a chromosome embarking on a journey around a cell in its division phase.

Your story will be a tale of the adventures the chromosome has on its journey.

Make sure your story is as close as possible to the real biological process, but you can also invent features and descriptions to make your chromosome into a character who can think and speak.

The activities on these pages work on the basic unit content, as well as the different language skills.

STEP

phenomenon in which effect is a natural The greenhouse and water vapour, carbon dioxide some gases, mainly Earth through, but rays that heat the allow the Sun’s the Earth emits when infrared rays that retain part of the temperature of the to this process, the it heats up. Thanks to exist. life enough for Earth remains warm

3

tion on the IPCC Look for informa Panel of Climate (Intergovermental its is is and what is Change). What function?

COMP REHE NSIVE WAST

FINAL STEP

of all kinds For manufacturers boilers, of equipment (engines, ensure these burners, etc.), to emit little energy and

clean energy And developing powerful, fusion, which is sources such as nuclear currently being studied.

Darwin’s theory

affect us?

? protect the climate

the father of Cuvier, considered the different ology, thought that . since the Creation had not changed

nist theory? a fixist or evolutio er.

Using public transport instead of your own car.

Switching off appliances we are not using.

taken to compost Organic remains are into fertiliser. plants to be turned

Unit 4

TION RIES. PROO F OF EVOLU are used in industry, Some materials wood with other metals and Paper, glass, plastics, plants so they are taken to recycling raw materials. can be reused as

mixed where they are . different products materials to make

sm An example of Darwini

1st generation rwinism is a of evolution, Neo-Da synthetic theory based on the Also known as the selection and is is the most theory of natural of thetion Aa Radioactive waste Elimina revised version has to Strict safety of waste. hazardous waste AA s: hazardous type Toxic and premise g itself. special ors. to d to transfer it tion followin in incinerat popula subjected is burned measures are employe ual but the be stored and Inert waste to before s the individ s to be able some pollutant unit is not emits AA aa storage facility, tion. to a central treatment processe s • The evolutionaryIncineration pes the popula ingenerate it into inert ntly in a deep occur but it genoty atmosphere, it is stored permaneAa in the eliminate it or transform es run the where it cannot to ry process Several variationsinto used the reposito be al geologic aa waste. mutations and energy that canfrom the Aa ity comes treatment plant. cause any harm. machines in the • This genetic variabil ction. during sexual reprodu Aa of recombination AA AA variability. n acts on genetic • Natural selectio result of this 2nd generation population as a lly appear in the ance of • Changes will gradua lly lead to the appear process. They eventua natural selection a new species.

Neo-Darwinism

Swapping traditional light bulbs for LEDs.

aa

Speciation through which new evolutionary process Speciation is the a single population. are produced from

on

species

Proof of evolution

t from those that are differen reveals extinct species The fossil record g evidence: It provides the followin . we know today. of modern-day species are the predecessors be • Fossilised species of fossils that can which are groups ces, lar trait. sequen • Phylogenetic l changes of a particu show the gradua traits of ordered by age and that exhibit the which are fossils they how fossils, show ional , and • Transit or taxonomic groups two different species one to the other. progressed from

.

Understand, think, apply..

n of moths ion of the evolutio .

1 Look at the illustrat ing to Neo-Darwinism

2

45

46

AA

AA

AA AA

Aa

Aa

3rd generation AA

AA AA

AA

AA

AA

evidence Palaeontological

The evolution of giraffes according to Darwin

AA

AA

AA

Darwin. It was proposed by n speciation model phic isolation: a The most commo result of geogra these ion occurs as a tions. Over time, suggests speciat s and isolates popula t species. natural barrier appear and become differen own their on populations evolve

scene.

6

Commitment to SDGs

RY THEO CURR ENT EVOLU TIONA ing

2 Insulating rooms and windows in.

of giraffes to keep n heat The evolutio according to Lamarck

theory of natural came before the Reading. Read ‘What ducacion.es resource bank and 5 anayae p his selection?’ in the d Darwin to develo ideas that inspire write the four selection. theory of natural evolution of illustrating the at the pictures each explain and 6 Writing. Look Darwin to Lamarck and giraffes according

suggest? ry of catastrophism explain? s theory trying to

Watch videos on Target 3.9 and complete the associated activities at anayaeducacion.es.

32

E MANA GEME NT

Now you can read your story to the class!

Unit 4

.

Understand, think, apply..

in the tation do the animals hibit?

below waste about comprehensive three management. What d? processes are involve ? Why is 2 What is waste sorting it important? available What options are 3 for sorting in your local area Look for rubbish and waste? explain whether information and g. anythin e improv you would

1 Look at the image

Use

of natural selecti

Wallace both and Alfred Russel n of Charles Darwin The naturalists ions about the evolutio the same conclus , in origin of species independently reached in his book The published them s: species. Darwin following premise n is based on the ages 1859. Natural selectio advant uals gives some individ n of traits, which variations betwee are • The variability there any population, increase the over others. In Some of these occur randomly. an individual, individuals that ctive success of l and the reprodu not produced probability of surviva be inherited and it. These traits must reduce others and by the environment. in a population. n the organisms survival betwee • The struggle for e for survival. lead to a struggl Limited resources als with advantageous or best-suited. Individu fittest, the of fully. The next l success • Surviva more and reproduce variations survive traits. has those same generation then to the tion of organisms to as a result of adapta modifications leads of • The origin of species lation time, the accumu species. environment. With lly results in new varieties, which eventua new breeds and

Write the story of the chromosome in an original and imaginative way. Don’t forget to describe where the story takes place, in this case the nucleus of a cell. Add details about the setting.

.

Understand, think, apply..

it ion. This makes according to its composit bins and collection it needs to be sorted using the different managed properly, For waste to be by the general public, y and personnel.

Waste can be sorted t plants with machiner easier to process. done at waste treatmen points, or it can be

change 4 How does climate personally to help 5 What can we do

l and financial Ensuring politica into ways backing for research efficiency of of increasing the sources renewable energy

consume on COevoluti 2. littleof Lamarck’s theory was Jean evolutionary theory in simple, edabout t to propose an publishss phy,awarene The first scientis ical philoso Raising clean we can do to k in his book, s ofZoolog through actions time over y everyda Choosing source species transform Baptiste de Lamarc his theory, ble energy help renewa andto 1809. According s acquired traits: geothermal switching off appliance the inheritance of example, For ion.

Such as solar, wind, to s perfect using public transport cy toward energy sources, we are not using, natural tenden and a hydrogen very little or no, that emit If we manage to • Organisms have to use or vehicles ms have replace fossil fuels. of heating vehicles ment, organis ng our use environ CO2, moderati in thetowards s in gradually occur change to change etc. of energy,and this leads types extent, • When changesthat run on these and refrigeration, or lesserthe situation creates a greater their organs to we will have improvedatrophy. In other words, use ment or considerably. them through develop organ. or eliminates the transmitted environment, are introduced by the • The acquired traits, to their offspring. strate that the e he could not demon als. was rejected becaus His theory 98 changes in individu the for sible respon environment was

• A body, or main part.

Lastly, re-read and review the text you have written. Make sure it is easy to understand and that there are no spelling mistakes. Change or modify anything you don’t like and correct any errors.

Sorting waste

MANA GEME NT SUSTA INABL E ENER GY Establishing energy ions efficiency regulat

• Decide what other supporting characters you are going to need and give them names.

Create some drawings to illustrate your story.

• An ending.

process ies that nature cannot ment. in such large quantit Waste is produced impact on the environ lates, having a major ries: it all and it accumu d into several catego e can be classifie this type of The waste we produc a huge amount of is There . waste (MSW) environment • Municipal solid lates in the natural accumu It s, varied. batterie as waste and it is very Some items, such ce in food chains. and causes imbalan g. be broken are highly pollutin quantities, it cannot produced in large soil. and • Farm waste. If water ends up polluting down naturally and as acids and of this waste, such mining waste. Some • Industrial and be very toxic. heavy metals, can radiation strong bases, or ous because it emits long This is very hazard s active for a very • Radioactive waste. remain It beings. l to living that is very harmfu time.

.

Understand, think, apply..

• You can give your chromosome character a name.

3

• An introduction, or beginning.

Types of waste

Climate change

emitted of the infrared rays CO2 means more words, the natural The increase in are retained, in other average by the Earth’s surface is causing the increases. This is known greenhouse effect The phenomenon the planet to rise. climate temperatures on consequence is main its and g, g with the followin as global warmin around the world evident is change, which effects: . subtropical regions in ing increas • Droughts are ing increasingly becom are torrential rains • Hurricanes and . frequent and intense to lly melting, leading glaciers are gradua coastal • The ice caps and disappearance of the consequent s. rising sea levels and in marine current well as changes as , areas and islands plant cycles, the alter which tems occur, serious • Changes in ecosys and, in the most migration of fauna movement and . earance of species cases, the disapp

Unit 9

GEME NT SUSTA INABL E WAST E MANA

5 The greenhouse effect

Next, define the characters:

• Write an original description of each character.

Use a story structure, making sure it has:

of the ozone layer The destruction the action was caused by of the ozone layer ), which The destruction (chlorofluorocarbons ant gases, CFCs s in the of certain refriger refrigeration system , in aerosols and CFCs were banned were widely used tional efforts ensured h it is a 20th century. Interna to repair, althoug begin could layer meaning the ozone slow process.

2

First, give your story a title. Try to think of an original and catchy title.

AA

AA AA

ion An example of speciat through geographic isolation Individuals of the same species.

and explain

ed accord what has happen s’ available evolutionary theorie Reading. Read ‘Other resource bank and explain the n.es ism. in the anayaeducacio according to neutral ism of evolution fundamental mechan Neo-Darwinism? that proposed by Is it the same as

AA

of moths. colour in this population gives it A gene determines wing dark wings, and allele a Allele A gives the moth with dark wings are better light wings. The individuals to predators than those with camouflaged and less visible wings. white

The hills geographically isolate the populations. Over time, two different species form.

Homologous organs

The resource bank contains audiovisual material that focuses on Sustainable Development Goals.

evidence animals and Biogeographical tion of modern geographical distribu The study of the of evolution: become fossils provides proof to each other. They similar in areas close • Living beings are are. they further apart America and more different the coasts of South been found on the • Similar fossils have the southern Africa. the continents of fauna found on a common • Some flora and suggest they share have traits that of the hemisphere today g the separation independently followin es). origin, but evolved emus and ostrich e, ratites (rheas, continents. For exampl rative anatomy in shape differ Evidence from compa that organs have homologous evolution • Related species ts the concept of function. This suppor to adapt. depending on their which an organ evolves e divergence, in 99 perform through adaptiv similar shapes to are those that acquire Evolution • Analogous organs common origin. without having a but n, functio the same e convergence. through adaptiv

Horse

Cetacean

Human being Bat

Reptile

ce very similar in Embryological eviden related animals are some groups of • The embryos in their first stages. embryo that present in the , there are organs other groups of in • In some animals remain they adult. However, disappear in the related animals.

Skills

ce Biochemical eviden biomolecules. are made from similar organisms.

• All living beings are common to many lic pathways which • There are metabo all the cells. res are similar in scientists • The cell structu have also allowed ues sequencing techniq out their DNA and protein t species and work differen in les molecu phylogenetic to compare these possible to create This has made it . evolutionary history. between species the relationships reveal which trees

Embryonic development Mammal

Bird

Fish

The suggested activities have been specially designed to gradually and continuously develop the four language skills. The main skill worked on in each activity is highlighted:

.

Understand, think, apply..

and of different animals

s of the limbs 3 Look at the diagram res are similar. How is the limb of a bat how the structu of an organ

explain you think of a cetacean? Can different to the limb to the bat’s wing? that is analogous in the ties and differences explain the similari do 4 Speaking. In pairs, and mammals. What birds fish, of ment embryonic develop these traits prove? allow us e, what parameters evidenc ical rs?

5 According to biochem beings come from common ancesto living to all and that to suggest tiate between them ts use to differen What do scientis trees? create phylogenetic

With pharyngeal arches and tail.

With pharyngeal arches and tail.

With pharyngeal arches and tail.

With pharyngeal arches and tail.

The pharyngeal arches disappear, but not the tail.

The pharyngeal arches and tail disappear.

Speaking Listening

Reading Writing 47

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4

CE BANK RESOURpanie s this book.

Go to the

Available

ion.es nayaeducac

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5

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KS OF CELLS: THE BUILDING BLOC

1

LIFE

Eukaryotic cells

Inorganic substances

Minerals Structural function Regulatory function

a nucleus, All eukaryotic cells have variety of a cytoskeleton and a wide organelles.

of organic are made up Living beings substances. and inorganic

matter The composition of living Water Structural function Metabolic function Transport function n Thermoregulatory functio

In this section of the book, the key information is presented in graphic form, using diagrams and illustrations to help you learn each concept.

SUMA

8450903

9

unit

Key concepts

SECONDARY EDUCATION 98-7995I S B N 978-84-6

1

…

t r a p is h t in d An

biolo gy and geolo gy

that accom

+

du al FOCUS

Carbohydrates n Energy-producing functio Energy storage Structural function ns functio Other

Organic substances

Proteins Structural function Enzymatic function Transport function Other functions

e Cytoplasm: a jelly-lik substance that fills the cell.

DNA, or the genetic material of the cell.

Golgi apparatus: transports substances with its vesicles.

Ribosomes

Cell membrane

the Endoplasmic reticulum: rough one (RER) creates one proteins and the smooth (SER) synthesises lipids.

NOT These cells DO lasts, have: chlorop walls. vacuoles or cell

s: contain Lysosomes and other vesicle substances other digestive substances and with different functions.

Cell theory Cells are the structural units of living beings.

Cells are the functional units of living beings.

All cells are produced from other cells via reproduction.

Ribosomes: synthesise proteins.

ent of Centrioles: direct the movem in involved the cytoskeleton and are cell division.

Cytoplasm

Cytoskeleton: a network of filaments that gives the cells their shape and enables them to move.

Nucleic acids ation They contain genetic inform n They control cell functio

Cell membrane: regulates the exchange of substances, detects environmental stimuli and allows cells to communicate.

Nucleus

Mitochondria: obtain energy for the cell through cellular respiration.

Lipids Energy storage Structural function Regulatory function Other functions

Cells All cells have:

Animal eukaryotic cell

Plant eukaryotic cell Mitochondria

Nucleus

Golgi apparatus

Cytoskeleton s Chloroplast: photosynthesi takes place here.

Endoplasmic reticulum

Prokaryotic cells

Vital functions otrophic Nutrition: aut synthesis and nutrition (photo and heterotrophic sis) the syn mo che nutrition. to they use flagella Interaction: g, sliding or remaining move, spinnin immobile. : through binary Reproduction fission.

t

Ribosomes

uni

cells that have These are small, simple s organelles. no nucleus or membranou

Plasmids are small circular chains of DNA.

Cytoplasm

The DNA is in a single thread.

4

Cytoplasm Vacuole: large ane-bound vesicle that

The process of

membr the origins of life esin theonrigidity helps mainta Early hypothes cell.

Lysosomes and other vesicles

Human evolution Fimbriae, filaments that attach cells to other cells or surfaces. They can also have other filaments to called pili that they use l exchange genetic materia with other bacteria.

Cell membrane

Some bacteria have a capsule that surrounds hominisation the cell wall.

Oparin and Haldane’s hypothesis

of the

The theory of spontaneous generation originated suggested that life NO T In ls DOmatter. se celinert spontaneouslyThefrom trioles.

Redi the 17th century, have: cenFrancesco appeared maggots that demonstrated in rotten meat because flies had laid their eggs there.

In the 19th century, Pasteur demonstrated that even microorganisms didn’t appear spontaneously; they were in the air.

This involved the acquisition of several characteristics: Cell wall: the external Cell covering that protects ✓ Bipedalism, or upright provided several advantages, such asthe cell and maintains ane membrposture: freeing up the hands and being able to see from higher up to detectconsistency. prey and predators. The celldswall surroun the cell and gives ✓ Increase Flagell in acraniummembr size: ane allowed intelligent thought. the cell its shape. ✓ Development of language. ✓ Neoteny: we are born in an immature state of development and are dependent as children for a long period of time.

Alexander Oparin and John Haldan e both suggested that life arose inorganic molecules. According to from hypothesis, biomolecules formed their from chemical reactions between gases the primitive atmosphere. The energyin for these reactions came from solar radiation and the electrical charges in storms.

Meat

…after a few days…

5

4

Cell evolution Our ancestors They lived on the savannah more than 4 million years ago.

They walked upright and had large jaws.

Australopithecus afarensis

Homo habilis

They lived between 1.6 million years ago and 100 000 years ago. They used fire and their tools were more complex.

Homo erectus

Homo antecessor

The earliest remains date back 160 000 years. They became extinct 28 000 years ago. They had a very robust body and a high cranial capacity.

Homo neanderthalensis

Before living beings there were pre-cellular structures, in other words, organic molecules that were simpler than current ones. Around 3 800 million years ago they evolved into prokaryotic organisms. Then, after a process that lasted around 2 000 million years, eukaryotic cells appeared.

Heterotrophic prokaryotes: in an atmosphere without oxygen, they obtained nutrients and energy from the fermentation of organic matter.

Autotrophic prokaryotes: some bacteria survived when organic matter became scarce because they performed photosynthesis.

Homo sapiens

Endosymbiotic theory

Aerobic bacteria (respire O2) Amoeboid prokaryotic organism Formation of mitochondria

Spirochaeta Flagellum

Towards animals

They lived in Africa between 2.3 and 1.6 million years ago.

They made tools.

Activities The resource bank contains activities for you to practise what you have learnt.

18

These were the ancestors of Neanderthals and modern humans.

Aerobic heterotrophic prokaryotes: the presence of oxygen caused organisms to appear that were capable of cell respiration.

The earliest remains date back 200 000 years. Their skull and skeleton have all the modern traits.

Nucleus Towards plants Formation of chloroplasts

According to this theory, proposed

by Lynn Margulis, some organelles in eukaryotic cells originated from prokaryotic organisms that were absorbed by another organism, establishing a symbiotic relationship between the two.

Mitochondria are considered to have developed from heterotrophic bacteria, and chloroplasts from cyanobacteria.

Cyanobacteria cells (photosynthesis)

anayaeducacion.es You can use the activities in the resource bank to review the content of these fact files.

19

7

The

Resource bank www.anayaeducacion.es

This is where you will find resources, techniques and activities to help you consolidate your knowledge.

Go to www.anayaeducacion.es, and follow the steps at the beginning of your Spanish book.

1

THE ENVIR ONMEN T AND ITS

SITUAT ION TODAY Sustainable developme

nt: SDGs

The environment is the collection of physical , chemical, biological and social factors that make up our surroundings and have an impact on our life and our activities.

Environmental impacts

The environment today

Today’s human populat ion far exceeds 7 000 million people and continues to grow at a very rapid rate. Of course, that many people need a huge amount of resources to be able to survive and carry out their daily activitie s, as well as to reach an acceptable level development and well-bein of g.

Our lifestyle is also highly consumption-or iented, where just a rich countries consum few e enormous amounts of matter and energy, while many others not even have the basics to survive. This lifestyle means humans have to overexploit resource s, producing negative effects:

Your book contains references to the online resources you can use to learn more about each topic and to develop your English language skills.

• The loss of biodiversity and the ecosystems inhabited by living beings.

• Deforestation and desertifica tion result of soil loss and an increasinglyas a arid climate.

resources.

• Alterations to the natural environment, which produce several types of environmental impact: loss of biodiver sity, deforestation and desertification, pollution and accumulation of waste.

Concern for the environ

ment

Luckily, in recent years, we have developed a greater awareness of we should react to this how situation and avoid or solve the degradation the environment. of We need to find formulas for develop ment that are more environmentally friendly and respectful. This new model is called sustainable develop ment.

NO POVERTY

ZERO HUNGER

AFFORDABLE AND CLEAN ENERGY

• The pollution of the environmen t and consequences (such as the degradatioits n of bodies of water and soil, global warming and climate change, and the destruction of the ozone layer).

• The accumulation of waste, which space and degrades the environmenoccupies t over time, causing health problems.

Understand, think, apply...

1

Listening. Listen to ‘Exploiting the environm

ent: a

history’ in the anayaed ucacion.es resource bank and answer the following questions: a) Why was the environm ent able to regenera te when exploited by the first human societies ? b) What process increase d the severity of the alterations to the environm ent?

Changing our lifestyle

This model led the UN to adopt a series of Sustaina Goals (SDGs). ble Development

GOOD HEALTH AND WELL-BEING

QUALITY EDUCATION GENDER EQUALITY

CLEAN WATER AND SANITATION

• The depletion of natural

Environmental impact refers to the degrada tion of any environmental factors as a result of human activity.

The keys to sustainable development

A sustainable develop ment model is any model that meets the needs of the present, while preserving the environment and not compromising the ability of future generat ions to meet their own needs.

2 Speaking. In pairs, create a dialogue

that reflects a highly consumerist lifestyle. Cover the following points:

− Examples of this form

of consumption.

− Impact on the environm

ent.

− Ways to change this

lifestyle.

CLIMATE ACTION

DECENT WORK AND ECONOMIC GROWTH

LIFE BELOW WATER

INDUSTRY, INNOVATION AND INFRASTRUCTURE

LIFE ON LAND

REDUCED INEQUALITIES

PEACE, JUSTICE AND STRONG INSTITUTIONS

SUSTAINABLE CITIES AND COMMUNITIES

Using clean and renewable energies

RESPONSIBLE CONSUMPTION AND PRODUCTION

Sharing resources more fairly

PARTNERSHIPS FOR THE GOALS

Broadly, the SDGs aim to: • Stop the overexploitation

of natural resources.

• Reduce pollution.

• Solve the problem of waste. This is only possible if we generate waste and use what less we produce to obtain materials and energy.

• Protect natural areas.

• Avoid social inequali ty.

Protecting natural landscapes

Understand, think, apply...

3

Recycling materials

Writing.

Choose an SDG and write a text explainin what it consists of: importan g t figures, goal targets and the actions for achieving it. What can we do persona lly? Look for information on the United Nation’s web page.

4 What does sustainable development consist of?

5 Do you think the Covid-19 pandemic has affected existing social inequalities?

Respecting the environment

92

93

Resources organised

by unit

Interactive activities

8

All the resources are clearly organised so you can find the ones related to your unit.

l Audiovoisuuarces

res

Glossary

QcoRde

Unit 9

uunn i

itt

THE ORIGINS OF LIFE AND EVOLUTION

4

Scan this code to consult the glossary for this unit.

Spontaneous generation Oparin’s hypothesis

several theories have been proposed to explain it

Cell evolution Endosymbiotic theory Fixism

Inheritance of acquired traits

which opposes

Biodiversity

is the result of

has been explained by

Natural selection Neo-Darwinism

Biological evolution Palaeontological

which includes

of which there is much

Human evolution

Evidence

Biogeographical

that is

From comparative anatomy

via a process of

Embryological Hominisation

particularly the genera

Biochemical with changes such as

Australopithecus

Homo

Bipedalism Increase in cranial capacity Language Neoteny

Focus on English 1 Listening and Speaking. Listen and repeat the words to improve your pronunciation.

2 Reading and Writing. Use the branches of the outline to create three sentences about the evolution of life.

ANK B E G A U ANK NK G B N E G LA A U G N A NGUAGE BA

BANK

1

THE ORIGIN OF BIODIVERSITY

Biodiversity, or biological diversity, is the variety of species that inhabit, or have inhabited, the Earth.

Biodiversity and adaptation Adaptation is how living beings adapt to the conditions of the environment they live in. Adaptations can be: • Structural: affecting specific organs of the body.

• Physiological: affecting the function of the organism.

• Behavioural: actions carried out by organisms that benefit them.

Biodiversity and evolution Biological evolution is the process of slow and gradual changes that take place in living beings over millions of years.

Today we know that Earth’s huge biodiversity exists as a result of evolution from a common ancestor, and that all species originate from others.

Early theories about the origin of biodiversity Fixist theories Fixist theories upheld that all species were inalterable and had existed since the beginning of time. The creationists thought that all species were the result of divine creation.

However, when palaeontologists studied fossils, they realised that some species that had become extinct and others had appeared later.

The first evolutionist ideas emerged to explain these facts.

George Cuvier, however, believed that the changes were the result of a series of catastrophes that caused the extinction of several species.

These species were then replaced by means of divine creation (catastrophism).

George Cuvier, considered the father of palaeontology, thought that the different species had not changed since the Creation.

Understand, think, apply...

1 Speaking. In pairs, take it in turns to explain what environmental conditions these animals have adapted to: a) Birds that migrate to warm areas in winter. b) Birds with a strong hooked beak. c) Arabian camels, or dromedaries, which produce water from the fat in their humps. d) Animals that hibernate.

44

2 What kind of adaptation do the animals in the previous activity exhibit?

3 What did the theory of catastrophism suggest?

What facts was this theory trying to explain?

4 Is catastrophism a fixist or evolutionist theory?

Explain your answer.

Lamarck’s theory of evolution The first scientist to propose an evolutionary theory was Jean Baptiste de Lamarck in his book, Zoological philosophy, published in 1809. According to his theory, species transform over time through the inheritance of acquired traits:

Unit 4

The evolution of giraffes according to Lamarck

• Organisms have a natural tendency towards perfection.

• When changes occur in the environment, organisms have to use their organs to a greater or lesser extent, and this leads to changes in them through development or atrophy. In other words, use creates or eliminates the organ.

• The acquired traits, introduced by the environment, are transmitted to their offspring.

His theory was rejected because he could not demonstrate that the environment was responsible for the changes in individuals.

Darwin’s theory of natural selection The naturalists Charles Darwin and Alfred Russel Wallace both independently reached the same conclusions about the evolution of species. Darwin published them in his book The origin of species, in 1859. Natural selection is based on the following premises: • The variability of traits, which gives some individuals advantages over others. In any population, there are variations between individuals that occur randomly. Some of these increase the probability of survival and the reproductive success of an individual, and others reduce it. These traits must be inherited and not produced by the environment.

• The struggle for survival between the organisms in a population.

Limited resources lead to a struggle for survival.

The evolution of giraffes according to Darwin

• Survival of the fittest, or best-suited. Individuals with advantageous variations survive and reproduce more successfully. The next generation then has those same traits.

• The origin of species as a result of adaptation of organisms to the environment. With time, the accumulation of modifications leads to new breeds and varieties, which eventually results in new species.

Understand, think, apply...

5

Reading. Read ‘What came before the theory of natural selection?’ in the anayaeducacion.es resource bank and write the four ideas that inspired Darwin to develop his theory of natural selection.

6 Writing. Look at the pictures illustrating the evolution of giraffes according to Lamarck and Darwin and explain each scene.

45

2

CURRENT EVOLUTIONARY THEORIES. PROOF OF EVOLUTION

Neo-Darwinism

An example of Darwinism

Also known as the synthetic theory of evolution, Neo-Darwinism is a revised version of the theory of natural selection and is based on the following premises:

1st generation Aa

• The evolutionary unit is not the individual but the population itself.

Several variations in genotypes occur in the population.

• This genetic variability comes from the mutations and the processes of recombination during sexual reproduction.

AA AA

aa Aa

aa

Aa

• Natural selection acts on genetic variability.

AA

• Changes will gradually appear in the population as a result of this natural selection process. They eventually lead to the appearance of a new species.

Aa

AA

2nd generation

Speciation

aa AA AA

AA

Speciation is the evolutionary process through which new species are produced from a single population.

AA

AA AA

AA

The most common speciation model was proposed by Darwin. It suggests speciation occurs as a result of geographic isolation: a natural barrier appears and isolates populations. Over time, these populations evolve on their own and become different species.

Proof of evolution

Aa

3rd generation AA

• Fossilised species are the predecessors of modern-day species.

• Phylogenetic sequences, which are groups of fossils that can be ordered by age and show the gradual changes of a particular trait.

• Transitional fossils, which are fossils that exhibit the traits of two different species or taxonomic groups, and show how they progressed from one to the other.

AA

AA

AA AA

Palaeontological evidence The fossil record reveals extinct species that are different from those we know today. It provides the following evidence:

Aa

AA

AA AA

AA

AA

A gene determines wing colour in this population of moths.

Allele A gives the moth dark wings, and allele a gives it light wings. The individuals with dark wings are better camouflaged and less visible to predators than those with white wings.

An example of speciation through geographic isolation Individuals of the same species.

Understand, think, apply...

1 Look at the illustration of the evolution of moths and explain what has happened according to Neo-Darwinism.

2

46

Reading.

Read ‘Other evolutionary theories’ available in the anayaeducacion.es resource bank and explain the fundamental mechanism of evolution according to neutralism.

Is it the same as that proposed by Neo-Darwinism?

The hills geographically isolate the populations. Over time, two different species form.

Unit 4

Biogeographical evidence

Homologous organs

The study of the geographical distribution of modern animals and fossils provides proof of evolution: • Living beings are similar in areas close to each other. They become more different the further apart they are.

• Similar fossils have been found on the coasts of South America and Africa.

• Some flora and fauna found on the continents of the southern hemisphere today have traits that suggest they share a common origin, but evolved independently following the separation of the continents. For example, ratites (rheas, emus and ostriches).

Horse

Cetacean

Evidence from comparative anatomy • Related species have homologous organs that differ in shape depending on their function. This supports the concept of evolution through adaptive divergence, in which an organ evolves to adapt.

Human being

• Analogous organs are those that acquire similar shapes to perform the same function, but without having a common origin. Evolution through adaptive convergence.

Embryological evidence

Bat Reptile

• The embryos in some groups of related animals are very similar in their first stages.

• In some animals, there are organs present in the embryo that disappear in the adult. However, they remain in other groups of related animals.

Biochemical evidence • All living beings are made from similar biomolecules.

• There are metabolic pathways which are common to many organisms.

• The cell structures are similar in all the cells.

DNA and protein sequencing techniques have also allowed scientists to compare these molecules in different species and work out their evolutionary history. This has made it possible to create phylogenetic trees which reveal the relationships between species.

Understand, think, apply...

Embryonic development Fish

With pharyngeal arches and tail.

Bird

With pharyngeal arches and tail.

With pharyngeal arches and tail.

The pharyngeal arches disappear, but not the tail.

The pharyngeal arches and tail disappear.

3 Look at the diagrams of the limbs of different animals and explain how the structures are similar. How is the limb of a bat different to the limb of a cetacean? Can you think of an organ that is analogous to the bat’s wing?

4 Speaking. In pairs, explain the similarities and differences in the

With pharyngeal arches and tail.

Mammal

embryonic development of fish, birds and mammals. What do these traits prove?

5 According to biochemical evidence, what parameters allow us to suggest that all living beings come from common ancestors?

What do scientists use to differentiate between them and to create phylogenetic trees?

47

3

HUMAN EVOLUTION

The process of hominisation Human beings (Homo sapiens) belong to the group of hominids, and we are the only living species of this group. Although they are not completely sure, scientists believe that our most ancient ancestor belonged to the genus Australopithecus. The discovery of fossils of other hominid species has allowed them to reconstruct the phylogenetic history of modern humans.

Gorilla skeleton

The process of hominisation meant the acquisition of a set of traits that differentiate us from our primate relatives.

The characteristics of hominids • Bipedalism, or an upright posture, provided several advantages, such as freeing the hands to pick up and transport objects. Being able to see from higher up also helped detect prey and predators. It implied several anatomical changes: — The vertebral column took on an S shape.

— The pelvis became wider and shorter.

— The femur was more robust and leaned inwards.

— The bones in the feet changed to maintain balance and support body weight.

• An increase in cranium size and an increase in the volume and complexity of the brain (encephalisation) especially at the front, enabled intelligent thinking. The human brain is seven times larger than that of other mammals of a similar size.

• Development of language. Anatomical traits developed that permitted the articulation of a wide variety of complex sounds, as well as the association of these sounds to objects and thoughts.

• Neoteny. We are born in an immature state of development, particularly in terms of the brain, because the pelvis is narrow. We are dependent as children for a long period of time.

Understand, think, apply...

1 Speaking. Look at the pictures above. In pairs, talk about the differences between the gorilla skeleton and the human skeleton.

2 Write a definition of the following traits, neoteny, bipedalism, opposable thumb, hominisation.

3 Which anatomical changes did bipedalism involve, and what were their advantages?

48

Human skeleton

Unit 4

Our ancestors Fossils show us that our most ancient relatives belonged to the genus Australopithecus. They were followed by the genus Homo, which included different species.

• Australopithecus. They lived in small groups on the savannah more than 4 million years ago. They were short (1.3 m), but their pelvis and limbs show that they walked upright. Their skull and brain were small, and they had large jaws.

• Homo habilis. This was the most primitive species of the Homo genus.

They made rudimentary tools, which demonstrates conceptual thinking. They lived in Africa between 2.3 and 1.6 million years ago.

They were about 1.5 m tall and had a cranial capacity between 600 and 800 cm3.

• Homo erectus. They lived between 1.6 million years ago and 100 000 years ago. They were taller, at 1.70 metres tall, with a cranial capacity of 1 100 cm3. They used fire and their tools were more complex.

• Homo antecessor. These were the ancestors of both Neanderthals and modern humans. The remains found at Atapuerca, Burgos, are 850 000 years old and show that they lived in a temperate climate.

They were hunters and cannibals.

• Homo neanderthalensis. The oldest remains found are from 160 000 years ago. They had a very robust body and a high cranial capacity.

They were hunters, they used tools and buried their dead. They became extinct 28 000 years ago. It seems they lived alongside Homo sapiens, who ended up displacing them.

• Homo sapiens. The earliest remains are around 200 000 years old and were found in Africa. From Africa they moved to the other continents. Their skull and skeleton had all the modern traits. They lived in caves, where they left examples of their art. This demonstrates abstract thinking, which was possible because of the complexity of their brains.

Understand, think, apply...

4 Which genus do the fossils of the first true bipeds belong to?

5

Writing.

Choose one of the species of the Homo genus and write an explanation of its characteristics. You can find information in the educational mini-guides of the Museum of Human Evolution.

Our ancestors

Australopithecus afarensis

Homo habilis

Homo erectus

Homo antecessor

Homo neanderthalensis

Homo sapiens

49

4

HYPOTHESES ON THE ORIGIN OF LIFE

Early hypotheses Life appeared on Earth about 3 800 million years ago. Early theories about the origins of the Earth were based on magic or unknown forces.

Pasteur’s experiment 1 T he nutrient

broth is poured in through the neck of the flask.

Spontaneous generation This theory suggested that life originated spontaneously from inert matter. In the 17th century, Francesco Redi demonstrated that maggots appeared in rotten meat because flies had previously laid their eggs there.

Heat

In the 19th century, Louis Pasteur demonstrated that not even microorganisms appeared spontaneously. He established that they were in the air and developed on organic matter, which they fed on.

2 The neck of the

flask is bent into an S shape.

Oparin and Haldane’s hypotheses In the 1930s, Alexander Oparin and John Haldane both suggested that life arose from inorganic molecules.

According to their hypothesis, biomolecules formed from chemical reactions between the gases in Earth’s primitive atmosphere, which they believed was made up of water vapour (H2O), hydrogen (H2), methane (CH4) and ammonia (NH3). The energy for these reactions came from solar radiation and the electrical charges in storms. This formed simple sugars, fatty acids and nucleotides, which fell into the seas to form the ‘primordial soup’. These molecules then interacted and formed other, more complex ones, such as proteins and nucleic acids. As they became more complex, these molecules acquired the capacity to self-replicate.

In 1953, the scientists Stanley Miller and Harold Urey developed an experiment to check Oparin’s hypothesis.

3 The broth in the flask

is brought to a vigorous boil. The steam comes out from the tube.

4 Dust and bacteria are trapped here.

As the broth cools, the air in the flask contracts, dragging more air in from the outside. The dust particles and the microorganisms settle in the bend in the neck.

Understand, think, apply...

1 Writing. Look at the illustration of the experiment performed by Francesco Redi on the right and explain what it consists of. Do you think it was based on the scientific method?

2 How did Pasteur demonstrate that microorganisms did not appear from nowhere?

3 Look at the illustration of Pasteur’s experiment and explain what would happen to the broth if the flask was tilted, allowing dust and bacteria to get in.

4

50

Listening.

Listen to ‘Miller’s and Urey’s experiment’ available in the anayaeducacion.es resource bank and explain what this experiment demonstrated.

Meat

…after a few days…

Unit 4

The evolution of cells Before living beings there were pre-cellular structures, in other words, organic molecules that were simpler than current ones. Around 3 800 million years ago, they evolved into prokaryotic organisms: bacteria. Later, after a process that lasted around 2 000 million years, eukaryotic cells appeared.

• Heterotrophic prokaryotes. In an atmosphere that had no oxygen, the first prokaryotic cells obtained nutrients and energy from the fermentation of organic matter in the environment.

• Autotrophic prokaryotes. When organic matter began to become scarce, many bacteria died.

However, cyanobacteria were able to survive because they could synthesise organic matter through photosynthesis. As a result of this process, the atmosphere became enriched with oxygen.

Some chemosynthetic prokaryotes began to use this oxygen, obtaining energy from the oxidation of inorganic substances.

• Aerobic heterotrophic prokaryotes. The presence of oxygen caused organisms to appear that were capable of carrying out cellular respiration. As sources of matter in the environment began to run out, these heterotrophs acquired the ability to obtain the nutrients synthesised by autotrophs.

Endosymbiotic theory Aerobic bacteria (respire O2)

Amoeboid prokaryotic organism

Spirochaeta

Formation of mitochondria

• Eukaryotes. These emerged around 1 800 million years ago from prokaryotic cells.

Towards animals

Endosymbiotic theory

Flagellum Nucleus

Proposed by Lynn Margulis in 1967, this theory aims to explain the origin of eukaryotic cells. It suggests that some organelles in eukaryotic cells, especially chloroplasts and mitochondria, originated from prokaryotic organisms that were absorbed by another organism, establishing a symbiotic relationship between the two. Mitochondria are considered to have developed from heterotrophic bacteria, and chloroplasts from cyanobacteria.

Towards plants Cyanobacteria cells (photosynthesis)

Formation of chloroplasts

Understand, think, apply...

5

Listening. Listen to ‘The main principles of endosymbiotic theory’ available in the anayaeducacion.es resource bank and write down the four mentioned in the recording.

6 Speaking. In pairs, look at the diagram above and take it in turns to explain how mitochondria, flagella and chloroplasts are formed according to endosymbiotic theory.

anayaeducacion.es There are interactive activities in your resource bank.

51

The final challenge

ORGANISE A DEBATE Imagine a palaeontologist has come to class and has told you about different hypotheses for the origins of life. To get an in-depth understanding, you have decided to prepare a debate.

Work in groups. Divide the class into groups to organise a debate on the origins of life.

STEP

1

Investigate the hypotheses that exist about the origins of life. Prepare cards for each of them and share them between the groups.

For example: • Primordial soup.

STEP

2

Do some research into the hypothesis you have to defend in the debate.

• Look for information and gather data that supports your hypothesis.

• Prepare some arguments to defend your position.

• Panspermia.

• Hydrothermal hypothesis.

• Clay hypothesis.

STEP

3

Choose a spokesperson for the group. This person will be responsible for introducing the hypothesis at the beginning of the debate.

As a class, choose a moderator. The moderator will be responsible for introducing the presentations, ensuring the participants are respectful, and making sure each group gets the same amount of time.

52

FINAL STEP Start the debate.

• The moderator should start the debate by introducing each group.

• The spokesperson of each group should give an initial presentation about the hypothesis.

During the debate, respect the rules of conduct for participating. Always raise your hand when you want to speak and listen carefully, without interrupting, when others are speaking.

Watch the video on Target 9.a and complete the associated activities at anayaeducacion.es.

Go to the

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unit

4

THE ORIGINS OF LIFE AND EVOLUTION

Biodiversity and evolution Biodiversity or biological diversity This is the variety of species that inhabit, or have inhabited, the Earth.

Biological evolution Slow and gradual changes that take place in living beings over millions of years.

Biodiversity on Earth exists as a result of evolution from a common ancestor.

Theories about the origin of biodiversity Evolutionary theories propose that species evolve and change over time.

Lamarck’s theory of evolution According to Lamarck’s theory, species transform over time through the inheritance of acquired traits:

Modern day giraffes come from giraffes with short necks.

When the lower leaves became scarce, the giraffes stretched their necks and legs to reach higher leaves.

They transmitted this trait to their offspring, which also elongated their necks and legs. The process repeated until they reached the lengths we see today.

His theory was rejected because Lamarck could not demonstrate that the environment was responsible for the changes in individuals.

Darwin’s theory of evolution Darwin and Wallace both proposed natural selection as the mechanism for the evolution of species: In giraffe populations there were individuals with short necks and others with long necks. These traits were transmitted down through the generations.

The individuals have random variations. Some make survival and reproductive success more probable, while others make it less probable.

These characteristics can be inherited.

16

When leaves became scarce, the ‘long neck’ trait was an advantage. As they were better adapted to the new conditions, the giraffes with long necks reproduced more than those with short necks, many of which died.

Limited resources lead to a test, struggle for survival. The fitls or most well-suited, individua survive and reproduce more successfully.

After many generations, all the giraffes in the population had long necks.

With time, the accumulation of modifications leads to the appearance of new species.

Neo-Darwinism or the synthetic theory of evolution ✓ The evolutionary unit is not the individual

✓ Natural selection acts on genetic variability. but the population itself. Several variations in ✓ Changes will appear in the population as a result genotypes occur in the population. of this natural selection process. ✓ The genetic variability comes from mutations and recombination.

2nd generation

1st generation Aa

aa

AA AA

AA

aa

AA AA

Aa

aa

Aa

AA AA AA

AA AA

AA

Aa

Aa

Aa

Proof of evolution Palaeontological evidence

Biogeographical evidence

• Fossils from different extinct species.

• Fossilised species are the

• Living beings are similar in areas close to each other.

predecessors of modern-day species.

• Fossils that show progressive change (phylogenetic sequences).

• Fossils with traits from two groups or species.

• There are fossils common to

both South America and Africa.

• There are organisms on the continents of the southern hemisphere that have a common origin.

Evidence from comparative anatomy

• Similar molecules in living beings.

• Common metabolic pathways in organisms.

• Similar cell structures in cells.

• DNA sequencing allows relationships to be established between species.

Embryological evidence

• Homologous organs in related species with different shapes depending on function.

• Analogous organs acquire similar shapes to perform the same function.

Human being Horse

Biochemical evidence

• Embryos in related

animals are similar in their first stages.

• Some organs present in embryos disappear in adults, but remain in other groups of related animals.

Fish

Bird

With pharyngeal arches and tail.

With pharyngeal arches and tail.

With pharyngeal arches and tail.

With pharyngeal arches and tail.

The pharyngeal arches disappear, but not the tail.

The pharyngeal arches and tail disappear.

Cetacean

Reptile

Mammal

Bat

17

Human evolution The process of hominisation This involved the acquisition of several characteristics: ✓ Bipedalism, or upright posture: provided several advantages, such as freeing up the hands and being able to see from higher up to detect prey and predators. ✓ Increase in cranium size: allowed intelligent thought. ✓ Development of language. ✓ Neoteny: we are born in an immature state of development and are dependent as children for a long period of time.

Our ancestors They lived on the savannah more than 4 million years ago.

They walked upright and had large jaws.

Australopithecus afarensis

Homo habilis

They lived in Africa between 2.3 and 1.6 million years ago.

They made tools.

18

They lived between 1.6 million years ago and 100 000 years ago. They used fire and their tools were more complex.

Homo erectus

Homo antecessor

These were the ancestors of Neanderthals and modern humans.

The earliest remains date back 160 000 years. They became extinct 28 000 years ago. They had a very robust body and a high cranial capacity.

Homo neanderthalensis

Homo sapiens

The earliest remains date back 200 000 years. Their skull and skeleton have all the modern traits.

Early hypotheses on the origins of life The theory of spontaneous generation suggested that life originated spontaneously from inert matter. In the 17th century, Francesco Redi demonstrated that maggots appeared in rotten meat because flies had laid their eggs there.

In the 19th century, Pasteur demonstrated that even microorganisms didn’t appear spontaneously; they were in the air.

Oparin and Haldane’s hypothesis Alexander Oparin and John Haldane both suggested that life arose from inorganic molecules. According to their hypothesis, biomolecules formed from chemical reactions between gases in the primitive atmosphere. The energy for these reactions came from solar radiation and the electrical charges in storms.

Meat

…after a few days…

Cell evolution Before living beings there were pre-cellular structures, in other words, organic molecules that were simpler than current ones. Around 3 800 million years ago they evolved into prokaryotic organisms. Then, after a process that lasted around 2 000 million years, eukaryotic cells appeared.

Heterotrophic prokaryotes: in an atmosphere without oxygen, they obtained nutrients and energy from the fermentation of organic matter.

Autotrophic prokaryotes: some bacteria survived when organic matter became scarce because they performed photosynthesis.

Aerobic heterotrophic prokaryotes: the presence of oxygen caused organisms to appear that were capable of cell respiration.

Endosymbiotic theory Aerobic bacteria (respire O2) Amoeboid prokaryotic organism Formation of mitochondria

Spirochaeta Flagellum

Towards animals Nucleus Towards plants Formation of chloroplasts

According to this theory, proposed

by Lynn Margulis, some organelles in eukaryotic cells originated from prokaryotic organisms that were absorbed by another organism, establishing a symbiotic relationship between the two.

Mitochondria are considered to have developed from heterotrophic bacteria, and chloroplasts from cyanobacteria.

Cyanobacteria cells (photosynthesis)

anayaeducacion.es You can use the activities in the resource bank to review the content of these fact files.

19