STEMscopes Georgia Science Student Notebook Grade 7 by acceleratelearning

7 STEMscopes Georgia Student Notebook

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7th grade

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GEORGIA Student Notebook – Seventh Grade ISBN: 978-1-946725-77-6

Published by Accelerate Learning Inc., 5177 Richmond Ave, Suite 800, Houston, TX 77056. Copyright © 2017, by Accelerate Learning Inc. All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without prior written consent of Accelerate Learning Inc., including, but not limited to, in any network or other electronic storage or transmission, or broadcast for distance learning. To learn more, visit us at www.acceleratelearning.com

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GEORGIA

This Student Notebook is designed to be used as a companion piece to our online curriculum. The pages of this book are organized and follow the 5E model.

Student Handout

ENGAGE

A short activity to grab students’ interest

Student Journal

EXPLORE

A hands-on activity in which students get expereince with the concept being taught

STEMscopedia

EXPLAIN

A reference material that includes parent connections, technology, and science news

Reading Science A reading passage about the concept that includes comprehension questions

ELABORATE Math Connection

A set of grade-level appropriate math problems that address the concept

Writing Science

EVALUATE

A writing prompt based on the concept studied in which the students can demonstrate what they have learned

Only student pages are included in this book and directions on how to use these pages are found in our online curriculum. Use the URL address and password provided to you by your district to access our full curriculum.

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Seventh Grade Student Notebook Table of Contents

Lesson

Page

Life Science 7L1AB

Classifying Organisms 7L2A

Cell Structures 7L2B

Levels of Organization 7L2C

Interactions of Body Systems 7L3A

Genes, Chromosomes, and Inherited Traits 7L3B

Asexual and Sexual Reproduction 7L3C

Selective Breeding 7L4AB

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1 19 45 71 91 117 141 165 iii

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Seventh Grade Student Notebook Table of Contents

Life Science Lesson

Page

7L4C

193

Effects on Organisms and Ecosystems 7L4D

Terrestrial Biomes and Aquatic Ecosystems 7L5AB

Natural Selection, Survival, and Reproduction 7L5C

Fossil Evidence of Organisms

217 243 267

Appendix Glossary

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293

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7th Grade Life Science

7L1AB

Classifying Organisms

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7L1AB Classfying Organisms

Student Journal Name:

Date:

Group:

Part I: Where Do I Belong? Reflections and Conclusions 1.

What were the challenges you faced when sorting the organism cards into two groups, plants and animals?

How are fungi and plants alike and different?

Compare the characteristics of the six groups you eventually created with the card sort. What were common characteristics of each group?

animals:________________________________________________________________________ plants:__________________________________________________________________________ fungi:___________________________________________________________________________ protists:_________________________________________________________________________ cacteria:________________________________________________________________________ archaea:________________________________________________________________________

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7L1AB Classifying Organisms

Student Journal Project Design Checklist

Classifying GMOs

Instructions: Use this document to design your project to complete the Mission Deliverable. You will need to identify, organize, and list your tasks. You will also need to identify and list the resources that you need, as well as establish your due dates. Do not forget to number the tasks and the resources. If needed, you may use the reverse side of this document to expand your project design checklist. Your teacher will help you determine due dates.

Tasks

Resources

Due Date

Status Complete Not Complete

Complete Not Complete

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STEMscopedia: CLASSIFYING ORGANISMS 7L1AB Reflect Take a look at the pictures on the right. Think about what the two organisms have in common. They both need food and water to survive. They both grow and reproduce. They both have similar body organs such as lungs and a heart. Are these similarities enough to classify the organisms into the same group? If you answered yes, you are correct! Both organisms are classified as animals. If you answered no, you are also correct! The organisms have differences that scientists use to further classify these animals into smaller, different groups. The elephant is classified as a mammal, and the lizard is classified as a reptile. What process do scientists use to classify all forms of life? History of Classification Humans have always categorized their world in various ways. As early as 300 BCE, Aristotle classified animals by the place they lived (land or water) and by what they looked like (two legs or four legs). Carolus Linnaeus developed the binomial naming system in the 1700s, which gave each organism its scientific name. The broader levels of kingdom, phylum, class, and order were developed in the late 1700s. Until 1937 there were only two kingdoms—Plantae and Animalia—but with further study it was decided that a third kingdom was needed. Kingdom Protista was added at that time. Several years later, Fungi was added and since then, two more kingdoms— Bacteria and Archaea—have been added. Scientists Classify Organisms in Different Ways. Scientists organize the living world using a process called taxonomy: the science of classifying organisms based on shared structures, functions, and relationships to other organisms. For example, organisms can be classified based on their cellular structure. Organisms with nuclei are eukaryotes. Eukaryotes also have organelles, or specialized structures bound in a membrane. They are in a different group than prokaryotes—organisms that do not have nuclei. Also, many unicellular organisms are in a different group than multicellular organisms. For example, bacteria are unicellular organisms. They are in a different group than animals, which are multicellular. Taxonomy is the process of classifying organisms based on similarities.

Living things also can be classified according to the way in which they obtain food. Think about the differences between plants and animals. Plants make their own food and are called autotrophs.

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STEMscopedia: CLASSIFYING ORGANISMS Animals must consume other organisms and are called heterotrophs. This difference classifies plants and animals into two separate groups. Organisms’ method of reproduction can be used to classify organisms into even smaller groups. The two main reproductive methods are asexual and sexual. In asexual reproduction, only one parent is involved in producing offspring. In sexual reproduction, two parents-a male and female-are involved. Scientists use a branching system of classification. The broadest group is the domain. Each domain is subdivided into kingdoms, followed by phylum, class, order, family, genus, and species. We will focus on domains and kingdoms. All living organisms are classified into one of three domains: Bacteria, Archaea, and Eukarya. Domain Bacteria includes organisms commonly referred to as bacteria, which are unicellular prokaryotes. They are tiny organisms that reproduce asexually. Some bacteria are autotrophs (make their own food), but most are heterotrophs (consume their food.) The three domains are further divided into six kingdoms. The first two kingdoms are easy to remember. Domain Bacteria has just one kingdom: Bacteria. Kingdom Archaea also has just one kingdom: Archaea. Identifying the organisms in domain Eukarya is when classification gets more complicated. Domain Eukarya has four kingdoms: Animalia, Plantae, Fungi, and Protista. They are classified based on the complexity of their cellular organization, their ability to obtain nutrients, and their mode of reproduction.

Bacteria

Archaea

Animalia

Plantae

Eukarya Fungi

Protista

The three domains are further divided into six kingdoms. The first two kingdoms are easy to remember. Domain Bacteria has just one kingdom: Eubacteria. Kingdom Archaea also has just one kingdom: Archaebacteria. Identifying the organisms in domain Eukarya is when classification gets more complicated. Domain Eukarya has four kingdoms: Animalia, Plantae, Fungi, and Protista. They are classified based on the complexity of their cellular organization, their ability to obtain nutrients, and their mode of reproduction. Kingdom Archaea are single celled microorganisms without a nucleus in the cell and do not have any other organelles inside the cell. The biochemistry of these organisms is much different than any other life forms. These microorganisms live in very extreme conditions such as hot springs, thermal vents, digestive tracts of some animals. Organisms in kingdom Animalia are the most complex and are commonly referred to as animals. They are multicellular heterotrophs. Most reproduction in this kingdom is sexual, although a few animals can reproduce asexually. For example, if you divide a flatworm in half, each of the two halves will grow into a new flatworm. In the kingdom Plantae, the organisms are referred to as plants and are also very complex. Plants are autotrophs, since they make their own food. They are multicellular and can reproduce asexually or sexually.

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STEMscopedia: CLASSIFYING ORGANISMS Kingdom Fungi includes organisms such as mushrooms and molds. Most fungi are multicellular and can reproduce asexually or sexually. All fungi are heterotrophs. However, the way in which they obtain food is unique. Fungi absorb nutrients from the environment. Think about a piece of moldy bread. The mold is a fungus that releases chemicals to break down the bread into smaller substances. The simple organization of The mold can then absorb these smaller seaweed places them in substances, using them as nutrients. This kingdom Protista one characteristic that makes fungi different from animals. Kingdom Protista includes organisms with fairly simple structures compared to other eukaryotes. There is great diversity among the protists. Most of them are unicellular. However, some protists are multicellular. Some are autotrophs, in which case they resemble plants. Other protists are heterotrophs, more closely resembling animals. They swim through water and consume nutrients from their environment. Their simple organization keeps them in a separate kingdom from plants and animals.

Look Out Protists have been the most difficult group of organisms for scientists to classify. Some protists like green algae have the photosynthetic pigment chlorophyll that gives them a green color similar to plants. Other protists behave more like animals with whip-like structures that allow them to zoom around in the water. You can think of protists as the “other” category. They are single-celled organisms with a nucleus, but their structures are too simple to qualify them as plants or animals.

What Do You Know? Look at the chart below. It lists the taxonomic groups for three different organisms, beginning with order. Which two organisms are most similar to one another? Explain your reasoning below. Common Name

Order

Family

Genus-Species

Human

Primates

Hominidae

Homo-sapiens

Eastern Gorilla

Primates

Hominidae

Gorilla-beringei

Ring-Tailed Lemur

Primates

Lemuridae

Lemur-catta

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STEMscopedia: CLASSIFYING ORGANISMS Dichotomous Keys Identifying an organism’s taxonomic group or common name sometimes requires a dichotomous key. A dichotomous key is used to sort organisms. The key is based on questions about the traits and structures of the organisms. The word “dichotomous” means “cut in two.” When using a dichotomous key to identify an organism, “cut in two” means that a choice must be made about a characteristic at each two-fork branch in the key. Basically you have two options, and you have to decide one way or the other. The characteristics get more specific at each branch of the key. Dichotomous keys may be either written, as shown below on the left, or graphic, as shown on the right.

Let’s take a closer look at the graphic dichotomous key. It shows the method for identifying four different organisms by common name: duck, hen, lizard, and snake. The first step of the key, at the top, refers to the question, “Does the organism have feathers?” If the answer is yes, move to the left side of the key; if the answer is no, move to the right side of the key. Following the left side of the key, the next branch refers to the question, “Does the organism with feathers swim?” If the answer is yes, the organism is a duck. If the answer is no, the organism is a hen. Following the right side of the key, the next branch refers to the question, “Does the organism without feathers have legs?” If the answer is yes, the organism is a lizard. If the answer is no, the organism is a snake. Any type of dichotomous key must be detailed enough for the user to be able to observe an organism and determine which branch choice is the best match to the organism. The dichotomous keys above are very basic. However, some dichotomous keys are quite complex and contain numerous questions to help identify an organism’s binomial classification.

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STEMscopedia: CLASSIFYING ORGANISMS Binomial classification is the system of naming an organism (starting with its kingdom) by its genus and species. So many different species exist within a particular kingdom or phylum. Therefore, the best dichotomous keys focus on a specific bioregion. For example, a dichotomous key may be developed only for the types of organisms that live in oceans. You can see an example of binomial classification for a single species below. The binomial classification of the animal shown here is Panthera pardus. Panthera is the genus name, and pardus is the species name.

What Do You Know? Study the pictures of the insects at the right. Then use the dichotomous key below to identify the binomial classification of each insect. Write your answers on the line next to each insect.

Ant

Butterfly

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STEMscopedia: CLASSIFYING ORGANISMS Connecting With Your Child Creating a Dichotomous Key for Identifying Plants To help your child learn more about the identification of organisms, work together to create a dichotomous key that can be used to identify various plants. For this activity, search for images of different plants on the Internet or in old magazines. Try to find at least six different plants with varying characteristics (such as a pine tree, a palm tree, a strawberry plant, etc.), and print out pictures of each plant. If you are not able to print the images, have your child draw sketches of each plant. Write down at least five distinguishing characteristics for each plant. Characteristics to consider include leaf shape, leaf vein pattern, presence or absence of a trunk, habitat (land or water, jungle or desert, etc.), and any other defining characteristics you would use when describing the plant to another person. If possible, write down the binomial classification (genus and species name) of each plant as well. If you are not able to find the binomial classification, write down the common name of each plant. Create a list of “yes-no” questions that address the characteristics identified in at least one plant. Using index cards or construction paper cut into squares, write the name (genus and species or common name) and a description of a single species on each card. Next, write the “yes-no” questions on another set of index cards, one question per card. It might be useful to use a different color pen for the questions. Using the “yes-no” questions as a guide, start sorting the piles into a branching tree. Be sure that each branch only has two options for answers. You may need to rearrange your questions until you arrive at a dichotomous key in which the questions become increasingly restrictive and the plants make up the bottom row. Once you are satisfied with your key, draw it on a piece of paper. Here are some questions to discuss with your child: Here are some questions to discuss with your child: 1. Why are only inherited traits used to classify the plants? 2. Look at the final dichotomous key. Did you end up grouping any plants together? If so, do these plants have any differences? 3. How are dichotomous keys helpful to scientists when they discover what they think might be a new species?

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7L1AB Classifying Organisms

Reading Science Name:

Date:

Group:

What’s in a Name? 1

Shakespeare famously wrote in Romeo and Juliet, “What’s in a name? That which we call a rose by any other name would smell as sweet.” These words express his belief that it doesn’t matter what we call something. While fiction writers may not always value precision in what things are called, it is very important to scientists. Scientists need a method to organize and classify groups of life-forms. Scientists keep revising the process over time, as our knowledge about the world around us continually grows.

As science discovers more about the characteristics of organisms, our classification systems have become more refined. The most basic level of classification is prokaryote and eukaryote. All species of bacteria and archaea are prokaryotes, which means they are organisms with cells that don’t have a nucleus or other cellular structures enclosed in a membrane. Eukaryotes are those organisms that we can often readily identify by sight. They are animals, flowers, mushrooms, and protists. Each of their cells has a nucleus and other membrane-bound cellular components.

A domain is the largest rank in the classification system. There are three domains: Eukarya, Bacteria, and Archaea. Eukarya is the domain composed of eukaryotes, which are life-forms that have cells with a nucleus and other complex structures enclosed by membranes. Most of the creatures we consider “animals” belong within this domain, as well as all plants, fungi, and protists. Bacteria is the domain composed of bacteria—prokaryotes found in nearly every modern environment and preserved in the oldest fossils on Earth. Though some bacteria cause disease, others can cure illness. Archaea is the domain composed of archaea, which are prokaryotes that often reside in places with extreme conditions like the boiling water of a hot spring or the oxygen-deprived ocean floor.

Every living being on the planet is a member of one of these three domains. All eukaryotes are included in the Eukarya domain. The Bacteria domain encompasses all bacteria, while all of archaea fall into the Archaea domain.

The next smallest classification group is kingdom. The eukaryotic kingdoms are Animalia, Fungi, Plantae, and Protista. The prokaryotic kingdoms are Eubacteria and Archaea. Organisms are classified at this level based on the complexity of their cell makeup and how they obtain nutrients and reproduce.

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7L1AB Classifying Organisms

Reading Science Continued 6 Organisms composed of only one cell are called unicellular. Examples of unicellular life include bacteria, archaea, most protists, and some fungi. Because they only have one cell, these organisms are usually microscopic, but some are large enough to be seen with the naked eye. These organisms must carry out all life processes within that one cell. In contrast, multicellular organisms have more than one cell. In multicellular organisms, individual cells serve specialized purposes and must depend on each other to ensure success as a whole. 7

There are two ways an organism can get nutrients. Autotrophs make their own, while heterotrophs must consume organic matter—often other living things—to get the substances required for survival. Most bacteria and archaea are autotrophs, while nearly all plants are photoautotrophic. Plants use light from the sun to manufacture the food they need to survive. Animals, including people, are heterotrophs. We can walk around all day with our arms outstretched to the sun and still need to consume other animals or plants to get the nutrients we need to survive.

There are two methods species use to reproduce. In sexual reproduction, the method utilized by most multicellular organisms, the offspring are created by combining two different sets of genetic material. In asexual reproduction, the offspring come from a single parent and only carry the genes of that parent. There are many different ways for an organism to reproduce asexually, including simply dividing into two daughter cells in a process called binary fission. Though many unicellular organisms can only reproduce asexually, either method can be used by some multicellular organisms, most notably certain plants and fungi.

Naming and classifying organisms is a tricky process that must incorporate new discoveries and information. Knowing the basics can help you think like a scientist when you read about scientific discoveries.

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7L1AB Classifying Organisms

Reading Science 1.

Why are humans called heterotrophs? A

Humans eat other organisms to get the nutrients they need to survive.

Humans have a complex cell structure.

Humans make offspring by joining two sets of genetic material.

Humans have a nucleus and a cell membrane.

A unicellular protist is part of which domain? A

Archaea

Bacteria

Eukarya

Not enough information to determine

Based on the information in this passage, which of the following is a reasonable conclusion? A

Scientists will never change the classification system again.

Scientists know everything there is to know about all organisms.

Scientists have never changed the classification system.

New scientific discoveries could change the current classification system.

What is the most likely meaning of the root word “photo” in the word photoautotrophic in paragraph 7? A

Picture

Light

Nutrients

Synthesis

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7L1AB Classifying Organisms

Reading Science 5.

Which of the following is the best summary of the passage? A

Eukaryotes and prokaryotes are different. One has a nucleus with a cell membrane and the other does not. Humans are eukaryotes.

There are many ways to classify organisms. They can be either bacteria or archaea.

There are three domains of life. All living creatures are a part of the Eukaryotic, Bacteria, or Archaea domain. There are six kingdoms, and organisms are grouped into kingdoms based on the complexity of their cell structure, how they reproduce, and how they obtain nutrients.

Organisms are everywhere. Some have a complex cell structure and some are unicellular. Some organisms thrive in extreme places. They are called archaea and can even live in hot springs and on ocean floors.

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7L1AB Classifying Organisms

Math Connections Name:

Date:

Group:

As environments and climates change, living things adapt to those changes. Sometimes genetic adaptations and mutations result in a new species. When a new species is discovered, the science of assigning it a scientific name, description, and identification is known as taxonomy. Use the taxonomy classification to figure out the scientific names for each of the animals listed below. Number

Common Name

American robin

Leopard frog

Great horned owl

Mallard duck

Jack rabbit

Ruby-throated hummingbird

Red-sided garter snake

Little brown bat

Harbor seal

Red kangaroo

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Scientific Name

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7L1AB Classifying Organisms

Math Connections Look at each animal on the previous page. Decide whether or not it flies, and solve the equation below next to that characteristic. Then find the answer to the equation in column 1. Choose from the two characteristics in the category. You will either see the scientific name or continue to solve equations and choose characteristics until you end at a scientific name. Begin here Ability to fly

a. Flying

x−21=36

b. Not flying

x−17=−12

x=57 Body covering

a. Feathered

x÷7=15

b. Not feathered

Myotis lucifugus

x=105 Type of feet

a. Web footed, water living

Anas platyrhynchos

b. Not web footed, not water living

−8x=104

x=−13 Type of flight

a. Hovering flight, very small

Archilochus colubris

b. Not hovering flight

x÷−4=−22

x=88 Type of food

a. Mouse eater, nocturnal

Bubo virginianus

b. Insect eater, diurnal

Turdus migratorius

x=5 Body covering

a. Hairy or furred (mammalian)

9x−7=−7

b. Not furred (not mammalian)

2(x+5)=−2

x=−6 Type of legs

a. Legs present

Rana pipiens

b. Legs absent

Thamnophis sirtalis parietalis

a. Aquatic mammal

Phoco vitulina

b. Terrestrial mammal

(5+x) / 6=−1

x=0 Habitat

a. Hopping or jumping locomotion x=−11 Type of locomotion b. Not hopping or jumping locomotion x=9 Type of tail

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−9x+1=−80 8x+7=31

a. Large with large tail used for balance

Macropus rufus

b. Small with small bobbed tail

Lepus townsendii

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7L1AB Classifying Organisms

Writing Science Name:

Date:

Group:

LOOK

THINK about using a dichotomous key to classify organisms. WRITE how to classify organisms based on their similarities and differences using a dichotomous key. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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7L1AB Classifying Organisms

Writing Science

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7th Grade Life Science

7L2A

Cell Structures

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7L2A Cell Structures

Student Handout

Name:

Date:

Sketch the picture on the handout. Answer the three essential questions: 1.

What is this a picture of?

Does it have needs? Explain.

How does it meet its needs?

Complete the T chart with things cells might need and ways they may fill their needs. Cells Need

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Ways Cells Fill Needs

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7L2A Cell Structures

Student Journal Name:

Date:

Group:

Plant and Animal Cell Organelles Background 1.

What is an organelle?

What is the structure and function of the cell membrane?

What is the structure and function of the nucleus?

What is the structure and function of the cytoplasm?

What is the structure and function of the mitochondrion?

What is the structure and function of the chloroplasts?

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7L2A Cell Structures

Student Journal Background, continued 7.

What is the structure and function of the cell wall?

What is the structure and function of vacuoles?

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7L2A Cell Structures

Student Journal Part I: Cell Organelles, Structure, and Function Plant Cell

Organelle

Structure of the Organelle

Functions/Organelle’s Job

Cytoplasm

Chloroplast

Vacuole

Cell Membrane

Nucleus

Cell Wall

Mitochondrion

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7L2A Cell Structures

Student Journal Part I: Cell Organelles, Structure, and Function, continued Animal Cell

Organelle

Structure of the Organelle

Functions/Organelle’s Job

Cytoplasm

Chloroplast

Vacuole

Cell Membrane

Nucleus

Cell Wall

Mitochondrion

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7L2A Cell Structures

Student Journal Part II: Organelles in Plant and Animal Cells 1. Draw and label a diagram of a plant cell. Plant Cells

2. Draw and label a diagram of an animal cell. Animal Cells

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STEMscopedia: CELL STRUCTURES

7L2A

Reflect Think for a moment about your school. It’s organized into parts that perform specific functions. For example, the principal controls everything that goes on in the school, the custodian takes care of wastes, you get energy by eating your lunch in the cafeteria, the hallways transport you from classroom to classroom, and the security guard protects you. Your school would not function without all these individual parts carrying out specific functions in the school. If this organization works so well, do you think a similar type of organization might be at work inside a cell? Why Must Cells Absorb Energy and Nutrients? Every living thing is made up of cells. All living things are called organisms. Most contain single cells. However, humans have multiple cells. To survive, cells play many roles. They grow, divide, and produce more cells. To produce more cells, they need to take in nutrients. Nutrients are defined as food or other substances that provide energy or building material for the survival and growth of a living organism. Just as your school has parts that carry out different functions, each cell in the body has structures that carry out specific functions. These structures are called organelles. An organelle performs a specific function to help meet the basic needs of the cell. Altogether, the sum of these contributions ensures survival of the cell.

Look Out There are many misconceptions about cells. • All cells are flat and small. Cells come in many different shapes and sizes, depending upon their function. • Cells cannot live on their own. Actually, some organisms consist of a single cell that can carry out The mother elephant all life processes needed for survival. doesn’t have larger cells. • The larger the organism, the larger the cells that make up that She’s bigger because she organism. has more cells than the Larger organisms have more cells than smaller organisms. baby.

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STEMscopedia: CELL STRUCTURES • •

Cells look like the color-coded drawing in the books. The pictures are diagrams, not actual cells. Cells look different depending upon their functions. All organisms have all levels of organization. Some organisms consist of a single cell, while others are composed of cells and tissues only. Not all organisms have organs or body systems.

This is a cheek cell under a microscope. It looks much different than a cell diagram.

Cells Reproduce The cell nucleus is one example of an organelle. This structure is found near the center of the cell. The cell nucleus acts like the brain of the cell. It helps control eating, movement, and reproduction. Chromosomes are located inside the nucleus. The genetic information in chromosomes directs the main functions of the cell, including protein synthesis, reproduction, and heredity. During cell reproduction, the cell makes a copy of all of its chromosomes and sends an identical copy to the new cell that is created. Cells obtain energy. Cells must obtain energy in order to survive and carry out its functions. All cells have a cell membrane that surrounds the cytoplasm. The cell membrane functions to hold the cell together. It also functions as a barrier between the cytoplasm and the external environment, allowing only certain substances into or out of the cell. Cells must take in substances from their environment in order to perform basic functions of life. The cytoplasm provides a site for the chemical processes needed to carry out these life functions. Mitochondria plays a vital role in obtaining and processing energy. Many cells typically have several mitochondria in their cytoplasm. Each individual mitochondrion carries out the chemical process known as cellular respiration. Cellular respiration is a series of chemical reactions that break down glucose molecules into carbon dioxide and water. During this breakdown, energy is released. The mitochondria are equipped with structures that capture this energy and store it in a form the cell can use for energy-requiring processes. For example, the energy can be used to allow the cell to grow and divide.

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STEMscopedia: CELL STRUCTURES Cells process waste. Cells have to have a way to remove waste in order to function. Lysosomes hold enzymes that were created by the cell. They are used to digest food and break down the cell when it dies. The cell absorbs food, and the lysosomes attach and release their enzymes. Lysosomes go to work even if there is no food for the cell. When the signal is sent out, lysosomes will actually digest the cell organelles for nutrients.

Try Now Which part of your school functions similarly to the organelles that we have talked about so far? Cell Organelle School Part nucleus cell membrane cytoplasm mitochondria Prokaryotic and eukaryotic are the two main types of cells. Prokaryotic cells are very small and do not have an organized nucleus. Most prokaryotic cells are known as bacteria. They are also able to do many different things such as live without oxygen, live in extreme hot or cold, and even live at the bottom of the ocean. Prokaryotes do not contain mitochondria or chloroplasts, but similar processes occur across the cell membrane. They also reproduce by binary fission and budding instead of mitosis and meiosis in a eukaryote. Eukaryotic cells have a defined nucleus and membrane-bound organelles that carry out specific functions. They also contain organelles and are self-sufficient. They can get very large and create their own parts.

What differences do you notice between the prokaryotic cell and the eukaryotic cell?

Plant cells are different from animal cells. Plant cells contain different structures whose functions differ from that of animal cells. One of these structures is chloroplast. Chloroplasts are needed for a plant cell to carry out photosynthesis. This is the process by which plants use radiant energy to make sugar from water and carbon dioxide. These organelles are green in color due to the presence of the green pigment called chlorophyll. This pigment absorbs light that provides the energy for conducting photosynthesis.

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STEMscopedia: CELL STRUCTURES Plant cells also contain a cell wall. The cell wall is a rigid structure that encloses the cell membrane and is able to provide structural support for a plant. Because of the presence of this cell wall, some scientists don’t believe that plant cells contain lysosomes. With the presence of the cell wall, such large molecules are not able to enter the cell. Plant cells also contain a large vacuole that stores water. In plants, water and sugar move in and out of vacuoles in response to environmental changes.

What Do You Think? If you forget to water some plants, they wilt. Later, after you water them, they perk up. Which plant organelle do you think helps a plant recover from wilting?

Try Now Look at the two diagrams of a plant and animal cell. Create a Venn diagram comparing the differences and similarities of the two types of cells.

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STEMscopedia: CELL STRUCTURES What Do You Know? Study the image below. Label each of the organelles in the diagram. Then, beside each labeled organelle, write the name of a part of a city that would carry out a similar function to that cell part. cell membrane nucleus lysosome mitochondria cytoplasm In the chart below, write how each of the cell parts work together. Organelles lysosome and mitochondria

How they work together

lysosome and cell membrane cell membrane and mitochondria nucleus and all organelles

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STEMscopedia: CELL STRUCTURES Connecting With Your Child Construct and Edible Cell Try making a 3D animal cell model. Use candies to make the various types of organelles. Materials • Jell-O™ (light colors work best) • Water • Spoon • Plastic bags Different fruits and candies can be used to represent the parts of the cell, such as raisins, gummy worms, gumdrops, gumballs, jelly beans, grapes, oranges, sprinkles, dried fruit, and hard candy. Directions The Jell-O™ represents the cytoplasm of the cell. If you make it with a little less water than the instructions state, it will be a little stiffer and will hold the cell parts better. 1. Heat the water to boiling. 2. Pour Jell-O™ into water and stir until it is completely dissolved. Then add cold water. Use the same amount of hot and cold water. 3. Put a 1-gallon plastic bag inside a sturdy container. 4. Pour the cooled gelatin into the bag. Be sure to leave room for the cell components. 5. Seal the bag and put it into the refrigerator. 6. When the Jell-O™ is almost set, open the bag and start adding the components of the cell. Record the parts of the cell that are used to absorb nutrients. What parts help divide the cell? Be sure to list what you used for each part of your cell. 7. Reseal the plastic bag and refrigerate the gelatin until it is fully set.

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7L2A Cell Structures

Reading Science Name:

Date:

Group:

A Close Look Into Cells 1

What are cells? Cells are the smallest units that carry out all of the activities of life in organisms. All living organisms are made up of one or more cells. New cells only come from division of existing cells. Cells are similar to humans in that they feed, excrete, and absorb. Humans eat because they need energy. Cells, too, need an energy source. Humans can produce the nutrient vitamin D from absorbing the sun’s rays through the skin. This is similar to how cells allow certain ions through their membranes for nutrients. Some organisms are composed of a single cell, like bacteria or some algae. They can only be seen through the use of a microscope. Other organisms are composed of multiple cells, such as humans, animals, trees, and flowers.

A microscope is an instrument used by scientists to study cells and other microscopic organisms. It is similar to a magnifying glass. The first crude microscope was designed by Dutch maker Zacharias Janssen in 1590. Although it would magnify an image, it was not always clear or sharp. In 1665, English scientist Robert Hooke improved the microscope and used it to look at a very thin slice of cork made from a tree. Hooke observed what appeared to be empty, box-like structures that reminded him of rooms, or cells, that monks lived in. That is how the cell got its name. This exciting discovery led to the invention of a better microscope by Dutch scientist Anton van Leeuwenhoek in 1673. It allowed him to see an image up to 270 times larger than its actual size. Van Leeuwenhoek reported being able to see things in pond water that no one had ever imagined before.

All cells, however, do not look like the square shape of a plant cell that Hooke observed. Human, bacterial, fungal, and algal cells all take on different shapes. As cells were studied over time, different observations and conclusions were made by numerous scientists. Together, their explanations became known as the cell theory, one of the major theories in science. The following are the major ideas of cell theory: 1. All organisms are made up of one or more cells. 2. Cells are the basic units of structure and function in all organisms. 3. All cells come from cells that already exist. Today, cell theory is the basis scientists use to study the parts of cells and how they are organized, reproduce, and change through time.

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7L2A Cell Structures

Reading Science Continued 4

Scientists have found that cells are organized in two different groups: prokaryotic and eukaryotic. Prokaryotic cells, such as bacteria, have no membrane around their genetic material. Eukaryotic cells, found in animal and plant cells, have a nucleus with a membrane around it. The genetic material is kept inside the nucleus.

Every cell of eukaryotic organisms, as small as they are, is made up of even smaller parts known as organelles. What does the name “organelle” mean? Organelle means “little organ.” In your body, there are many different organs, each with a unique function. Each must work together to sustain life. In a similar way, each organelle has a designated job to do that is essential for the overall survival of the cell. Some of these tasks include obtaining energy from food, moving waste to be expelled from the cell, and storing material. Organelles are surrounded by membranes and are found in the cytoplasm.

All cells have a cell membrane that covers the outside of the cell. The cell membrane separates the interior of the cell from its surrounding environment. One of its purposes is to regulate what enters and leaves the cell. The cell membrane keeps materials the cell needs inside the cell. It also prevents harmful substances from entering. The cell membrane also allows food and oxygen (nutrients) to be absorbed into the cell through the membrane. Excreted waste products are expelled through the cell membrane. This is similar to the way the skin of an animal functions to protect the inner regions of the body.

In organisms such as plants, fungi, algae, and many bacteria, the cell membrane is surrounded by a cell wall. Animal cells never have a cell wall. The cell wall helps to protect and support the cell. The structure is made of bundles of tough cellulose fibers and other materials made by the cell. In a multicellular organism, the cell walls of all the cells together provide structure to the whole organism, much like a skeleton.

The nucleus is a structure that directs all the activities of the cell. It is the control center of the cell, in the same way that the brain is the control center of an animal. The instructions that keep the cell running properly come from the nucleus. The nucleus is the largest organelle in the cytoplasm of a eukaryotic cell. The nucleus is separated from the cytoplasm by a membrane. It contains genetic blueprints for the functions of the cells in the form of DNA, our genetic makeup.

Endoplasmic reticulum (ER) is a complex series of folded membranes inside the cytoplasm of the cell. It allows material to be processed and passed throughout the cell. Think of this tubular membrane as the circulatory system in an animal, moving materials where they need to go. The ER takes up a lot of space within some cells. It extends from the nucleus to the cell membrane.

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7L2A Cell Structures

Reading Science Continued 10

A living cell also constantly produces waste products. Like an organism as a whole, the cell must remove these wastes. In the cytoplasm, organelles called lysosomes contain chemicals that aid in breaking down food, cell waste, and worn-out organelles. Lysosomes also recycle substances inside the cell. Wastes the lysosome cannot break down are enclosed in a membrane and moved out of the cell.

All of these parts of the cell are not just thrown together. Each has a special purpose and function, just like the organs within your body have a specific purpose. In fact, each cell performs functions that are similar to the body functions of complex organisms. It is amazing that a cell has that much power and control considering it is the smallest unit of life!

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7L2A Cell Structures

Reading Science 1.

What is the main point of this passage? A

Each cell performs functions that are similar to those of an entire organism.

A living cell doesn‘t make waste products.

Microscopes were invented in 1590. Improvements have allowed scientists to study cells and their components.

Cell theory tells us that cells are the basic unit of life, organisms are made up of cells, and new cells come from existing cells.

Cell theory was developed as a result of which of the following? A

The sole use of a microscope in labs

Observations and conclusions of many scientists

An English scientist, Robert Hooke

A Dutch scientist, Anton van Leeuwenhoek

Examine the diagram of a cell above. Based on the description in this passage, which part of an organism performs a function similar to the part of the cell marked with the arrow? A

Blood vessels

Skin

Bones

Brain

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7L2A Cell Structures

Reading Science 4.

Which body system has a function most similar to the role the lysosome plays for a cell? A

Skeletal system

Nervous system

Excretory system

Circulatory system

What is the definition of a cell according to this passage? A

Genetic blueprints for the function of a cell

Proteins and the chemical that controls the activities

A complex series of folded membranes in the cytoplasm

The smallest units whose purpose is to carry out all of the activities of life in organisms

What is the meaning of the word regulate in paragraph 6? A

Control

Protect

Stop

Allow

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7L2A Cell Structures

Math Connections Name:

Date:

Group:

All eukaryotic cells contain organelles. The unique structures and chemical compositions of individual organelles in plant and animal cells allow the organelles to perform distinct functions within their cell. Some organelles, such as the nucleus, are found in both plant and animal cells. Other organelles are used to distinguish between plant and animal cells. A seventh-grade science class was discussing animal and plant cells. The students discussed the function and structure of the various organelles present in both types of cells. Today the students will analyze the geometry found in the structure of animal cells. Use the materials supplied by your teacher and the picture below to answer the following questions.

The teacher explained that the nucleus and nucleolus of an animal cell are nearly perfect circles. 1.

Use the string and centimeter ruler provided by your teacher to measure the circumference of the nucleus in the magnified pictured above. (Round your answer to the nearest tenth.) cm

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7L2A Cell Structures

Math Connections (Round your answers to the nearest tenth.) 2.

What is the measure of the diameter of the nucleus?

What is the circumference of (the distance around) the nucleolus?

What is the measure of the diameter of the nucleolus?

Use the information from the previous four questions to complete the table below. For the last column, use a calculator to divide the circumference by the diameter. Cell Structure

Circumference

Diameter

cm cm

Circumference ÷Diameter

Nucleus Nucleolus 6.

Compare your results to those of your classmates. What do you notice about the quotient?

For any circle, the ratio between the diameter and circumference is known by the Greek letter π, or “pi,” which is close to the value 3.14. Measure and cut off a piece of string equal to the diameter of the nucleus. Approximately how many of the diameter-sized pieces of string do you need to measure all the way around the circular nucleus? Try it out, explain the results of your experiment, and define what π means to you.

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7L2A Cell Structures

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about the various cells that make up your body. WRITE Explain the basic functions of cells, including how they take in nutrients, grow, and multiply. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; • use correct spelling, capitalization, punctuation, and grammar.

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7L2A Cell Structures

WRITING SCIENCE

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7th Grade Life Science

7L2B

Levels of Organization

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7L2B Levels of Organization

Student Journal Name:

Date:

Group:

Background 1.

What is a cell? Include examples for both plants and animals.

What is tissue? Include examples for both plants and animals.

What is an organ? Include examples for both plants and animals.

What is an organ system? Include examples for both plants and animals.

What is an organism? Include examples for both plants and animals.

What are the levels of organization from smallest to largest?

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7L2B Levels of Organization

Student Journal Part I: Assembly Line 1. Plant Assembly Line

Station Number

Plant Sample

Level

2. Animal Assembly Line Station Number

Animal Sample

Level

3. Describe the differences you observed when looking at different levels of organization.

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7L2B Levels of Organization

Student Journal Part II: Organize the Organism—Plant 1. In the spaces below, paste the appropriate pictures in group 1 to match the correct term.

Cell

Tissue

Organism Organism

Organ

OrganSystem System Organ

2. How do all of these parts of this organism work together for it to function properly? Explain your answer.

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7L2B Levels of Organization

Student Journal Part II: Organize the Organism—Animals 1. In the spaces below, paste the appropriate pictures in group 2 to match the correct term.

Cell

Organism Organism

Tissue

Organ

OrganSystem System Organ

2. How do all of these parts of this organism work together for it to function properly? Explain your answer.

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7L2B Levels of Organization

Student Journal Reflections and Conclusions 1.

Explain the difference between cells and tissues.

Do animal and plant organisms have the same life processes?

If cells did not work together, what would happen to the organism?

Explain the difference between an organ and an organ system.

In the space below, draw the levels of organization of muscle cells.

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STEMscopedia: LEVELS OF ORGANIZATION 7L2B

Reflect What is your body made of? You might say that you are made of atoms or cells. You might even say you are made of organs, like skin and a heart. These answers are all correct. Each focuses on a different level of organization of the human body. Atoms are a nonliving unit of the body. But cells and organs are living units. How do these different living units relate to each other? Where do body systems, like the digestive system, fit into these levels of organization? Organization in Animals In all living things, the cell is the smallest unit of life. Some organisms are unicellular. They are made of a single cell functioning on its own. Bacteria and yeasts are two examples of single celled organisms. Animals are multicellular, meaning they are composed of more than one cell. In fact, the human body is made up of about 100 trillion cells! Cells have a variety of different shapes and structures because they each have a different function. For example, muscle cells tend to be long to allow for contraction. Nerve cells tend to have many branches to help with communication. One main function of red blood cells is to transport oxygen from the lungs to other cells throughout the body. An important function of certain bone cells is to release hormones that help form bones. Cells that are similar in structure and function form tissues. The cells that make up tissues work together to perform a specific activity. Animals have four main types of tissue: • Muscular tissue is involved in movement. For example, skeletal muscles help move the body. The stomach has smooth muscle tissue, which helps to churn foods and break the foods down into smaller pieces. The smooth muscle of the stomach can also expand to hold large amounts of food and then relax when empty. Nerve cells have many branches that help them send signals throughout the body.

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STEMscopedia: LEVELS OF ORGANIZATION • Epithelial tissue is found on the surface of organs and lines the inner spaces of the organs. This tissue type also covers the entire body because it forms skin. The main functions of epithelial tissue are protection, secretion (producing and releasing materials) and absorption (taking in materials). Epithelial tissue that lines the stomach secretes chemicals that help with digestion. • Nervous tissue functions to sense stimuli from the environment Stimuli: things that an and send signals throughout the body. For example, nervous tissue organism can sense in the stomach sends signals to the brain to let a person know when he or she is hungry. Nervous tissue also works with muscle tissue to help the body move. For example, when you touch a hot object, the nervous tissue in your hand sends signals to the brain to contract your muscles in order to move your hand away. • Connective tissue has a variety of functions. This type of tissue connects and holds together structures in the body, providing support and structure. Connective tissue includes bones and fat tissue. Connective tissue is also found under epithelial tissue and helps to support the cells of the epithelial layer. In the stomach, connective tissue can be found under its epithelial tissue also. The next level of organization in animals is the organ. Each organ is made of tissues with similar structure and function. Examples of organs include the heart, skin (the largest human organ), lungs, and stomach. The organ systems are the next level of organization. An organ system consists of two or more organs working together to perform a specific function for the organism. The human body is organized into several main organ systems: circulatory, nervous, skeletal, muscular, integumentary, endocrine, digestive, immune, reproductive, excretory, and respiratory systems. Each system performs specific functions. For example, the integumentary system is made of the skin, hair, nails, and glands. This system receives stimuli from the external Glands: organs that environment and protects the body’s deeper tissues and organs. make and release The digestive system is made of a number of organs. The stomach chemicals called stores food and helps with digestion. The intestines digest food and hormones; hormones absorb nutrients. The liver works as part of the digestive system by control and regulate secreting bile, which is a substance that helps with the break down of body processes fats, or lipids. A single organ can work with multiple organ systems. For example, the liver also works with the circulatory system to filter wastes in the blood.

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STEMscopedia: LEVELS OF ORGANIZATION The final and most complex level of organization in animals is the organism. Organisms are entire living things that perform basic life processes. Organisms take in materials, release energy from food, release wastes, grow, respond to the environment, and reproduce.

Simple The living units of organization from smallest to largest are cells, tissues, organs, organ systems, and organisms. The images here show, from left to right, are an epithelial cell, epithelial tissue, a stomach, the digestive system, and a human body. Note that the images are not to scale.

Complex

What Do You Think? Suppose one organ in an organ system failed to work properly. How would the organ system be affected? Would it still be able to function? Explain your reasoning.

Look Out Not all animals have the same levels of organization. For example, sponges are simple aquatic animals. They are multicellular; however, their cells are not organized into well-defined tissues. They do not have organs or organ systems. A sponge’s essential life functions are carried out on the cellular level. Sponges commonly Getting Technical: Magnetic Resonance Imaging live and grow on coral Magnetic Resonance Imaging, or MRI, is a procedure used by doctors reefs. to help diagnose organ or organ system diseases. The procedure uses magnets and radio signals to generate images of the inside of the body. The magnets and the radio signals in an MRI machine interact with the water in a patient’s body. The machine is then able to measure how much water is present in any given area. This creates an image with various shades of grey from light (where there is a lot of water) to dark (where there is little water). Because the magnetic coils are able create a magnetic force encircling the entire body, the MRI machine is able to image the body in three dimensions, or in 3-D. This is displayed as a series of pictures showing one slice of the body at a time. Doctors examine the images to look for structural abnormalities that may be present in the organs.

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STEMscopedia: LEVELS OF ORGANIZATION

An MRI machine generates a magnetic force that encircles the entire body.

An MRI machine generated this image of the brain and other structures.

Organization in Plants Like animals, plants are made of specialized cells that are organized into tissues. For example, xylem is a tissue that moves water, while the phloem is a tissue that moves sugars. Plant tissues are organized into tissue systems. Plants have three tissue systems: •

The dermal tissue system covers the outside of the plant and provides protection. The dermal tissue system includes epidermal tissue and tiny openings, called stomata, that open and close to allow for gas exchange.

•

The ground tissue system is a general tissue system with a variety of functions including photosynthesis and food storage. The ground tissue contains the photosynthetic cells (chloroplasts) of the plant.

•

he vascular tissue system is the system responsible T for the transport of materials, including water and nutrients, throughout the plant. Xylem and phloem are parts of the vascular tissue system.

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These plant cells group together to form tissue.

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STEMscopedia: LEVELS OF ORGANIZATION What Do You Think? Which tissue system in plants is most similar to the integumentary system in animals? Explain your reasoning. Plant tissue systems are organized into organs. Plants have four main organs: • Leaves are the main organs used to capture sunlight used in photosynthesis. • Roots are the main organs used to absorb water and nutrients from the soil. • Stems are the main organs used to transport materials between leaves and roots. • Reproductive organs (like flowers) produce seeds that grow into new plants. Flowers usually consist of colorful petals that attract insects and other pollinators. Plant organs group together to form the two main organ systems of plants: the root system and the shoot system. The root system is typically underground and includes the root and associated fibers that branch off the main root. This system functions to anchor the plant and absorb water and nutrients from the soil. The shoot system is typically above the ground and includes the stem, the leaves, and the reproductive organs, such as flowers. This system has many functions including photosynthesis and reproduction. As with animals, the organ systems of plants work together to make up the structure and function of the entire organism. The general organization in plants, from smallest to largest units, is shown below.

cells

tissues

tissue system

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organ

organ system

organism

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STEMscopedia: LEVELS OF ORGANIZATION What Do You Think? A specific example of this organization begins with long, narrow, specialized plant cells that work together to form the xylem, which is a tissue. The xylem works with the phloem (another tissue) to form the vascular tissue system. The vascular tissue system works with the dermal tissue system and the ground tissue system to form leaves, which are organs. Finally, leaves work with other organs (roots, stems, and reproductive structures) to make up a plant.

Look Out Not all plants have all the tissue systems and organs. Mosses do not have vascular tissue. Without vascular tissue, mosses cannot transport water long distances. This is why they can only grow in wet areas and why they cannot grow very tall. Mosses also do not reproduce using flowers. They use a simplified reproductive cycle involving tiny structures called spores.

Try Now What Do You Know? The chart on the next page includes images of different structures found in animals or plants. For each structure, describe the smaller living unit that makes up the structure. Also, describe the next largest living unit. Write your answers directly in the chart next to each image. Watch out! Some structures may not have a smaller or larger living unit. The first one is done for you.

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STEMscopedia: LEVELS OF ORGANIZATION Plant Tissue systems make up leaves. Leaves group together to form part of the shoot system.

Leaf

Nerve Cells

Circulatory System

Ground Tissue System

Brain

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STEMscopedia: LEVELS OF ORGANIZATION Connecting With Your Child Identifying Plant Structures To help students learn more about units of organization in plants, dissect plant organs and identify the tissue systems found within the organs. You will need a veined leaf (such as an oak or maple leaf), a stalk of celery, a carrot, a knife, and a hand lens (if available). Begin by identifying the veins of the leaf. The veins represent the vascular tissue system of the leaf, which is an organ. The dermal tissue system can be peeled off carefully to show the ground tissue system beneath. To peel off the dermal tissue system, bend the leaf in half until it snaps, and then peel back the clear dermal tissue system. Be sure to do this in an area of the leaf that is furthest from the thick veins. Next, explain to your child that the part of celery that we eat, the stalk, is actually a stem. Make a cross section of the stem; the dermal tissue system is on the outside. The vascular tissue system will look like clusters of circles. This is easiest to see if a hand lens is available. The rest of the cells in the stem are in the ground tissue system. Now explain to your child that the part of a carrot that we eat is a root. Make a cross-section of the carrot. The root will look much like the stem, but the vascular tissue system is generally found in a single large bundle in the center of the root. Here are some questions to discuss with students: 1. What was the smallest living unit of a plant that you were able to observe? 2. What was the largest living unit you were able to observe? 3. What might happen if a plant organ, such as a leaf or stem, became damaged? How would the organism be affected?

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7L2B Levels of Organization

Reading Science Name:

Date:

Group:

Getting Organized 1

Paige and Lane walked through the door of their home after school to find a disaster. Their dog had chewed up a throw pillow, and the stuffing was scattered everywhere. As they looked around at the dog’s mess, they realized that it was not the only thing cluttering up the place. They also saw clothes on the floor, crayons out of the box, and shoes scattered about. “Organization—that’s what we need,” Paige thought. She could still hear her mother’s voice saying, “It is so much easier to find things and keep our home clean when we organize everything. Even nature is organized.” Looking at this mess, Paige and Lane had to agree.

Organization is important in nature. Organisms, such as Paige, Lane, their dog, and even the trees in their yard, are highly organized and orderly. The tiny cells of Paige’s body are organized into different kinds of tissues. The tissues are organized into working organs. The organs are part of a larger organ system. The organ systems work together to produce Paige’s functioning body.

For example, the cells in Lane’s arm are organized into tissues that form muscles. These specialized muscle cells work together to shorten and lengthen, which causes Lane’s arms to move. The muscles form his body’s muscular system, which works together with the other systems of his body, such as the skeletal system, to help the different parts of Lane’s body move. The circulatory system delivers oxygen to his muscles. His digestive system helps provide the energy needed by his arm muscles. These organized systems all work together to keep Lane’s body functioning.

Realizing that organization helps, Paige and Lane agreed to use an organized approach to getting the house in order. As they worked together to clean up the dog’s pillow mess, Paige and Lane made a plan for keeping things organized. Lane would pick up all the trash he could find, even if it was in Paige’s room. He was also in charge of picking up the laundry scattered around the house. Paige’s job would be to gather all the things that were in the wrong place. She put the crayons back in the box and placed the box back in the art set. She picked up all the shoes and returned them to the closet. Each person had their own job. Working together like the systems in their bodies, Paige and Lane had the house in order quickly and could spend their time doing things that were a bit more fun.

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7L2B Levels of Organization

Reading Science 1.

Complete the following analogy: ORGANIZED CELLS : TISSUES :: A.

TISSUES

ORGANS

BODY

ORGANISMS

: ORGANS.

Increasing complexity

Paige

(3) (2) (1) Cells

The graphic organizer above shows the levels of organization described in paragraph 2. Based on the passage, which label goes in box (2)? A.

Organism

Organ

Organ system

Tissue

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7L2B Levels of Organization

Reading Science 3.

The muscle in Lane’s arm would best be described as which of the following? A.

An organ system

An organ

An organism

A tissue

With which of these statements would Paige’s mother agree? A.

Organization makes things more efficient.

Organization is not found in nature.

Organization increases the amount of work required.

Organization requires too much time.

Which of the following statements is true? A.

Organization is important in nature.

Organization is not found in nature.

Human beings are organized, but microbes are not.

The passage is about the importance of training pets.

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7L2B Levels of Organization

Math Connections Name:

Date:

Group:

Organs are made up of different types of tissue, which In turn are made up of different types of cells. In this activity you will analyze the different geometric structures that cells can assume. Epithelia tissue lines most digestive tracks in animals. One of the cells found in epithelia tissue, called simple columnar, has elongated hexagonal prism shapes (similar to the shape of a honeycomb). When the cells get crowded together, they take the shape of a pyramid. Another type of cell in epithelia tissue, called simple cuboidal cells, is box-like and takes on the shape of a rectangular prism. When crowded together, simple cuboidal cells also assume the shape of a pyramid. You will discover the difference in volume is between a prism and pyramid sharing the same base and the same height. To model the shape, six small equilateral triangle pieces are connected to form the base of a hexagonal prism (model for the simple columnar cell). Two hexagons create the top and bottom bases of the cell. One way to connect the six triangles together is shown below.

Look at only one cross-section piece of the simple columnar cells, a triangular prism-shaped piece. The triangular prism pictured below makes up one out of the six total triangular prisms found in the hexagonal prism cell. 1. Shade in the two congruent, parallel bases in the triangular prism below. Explain why the areas you shaded form the bases of the prism.

Imagine stacking your cut-up triangle pieces inside the triangular prism model. Think of the prism as constructed of many triangle pieces, layered on top of one another. Think about how many triangles the prism would need to be filled up. You would need as many triangles as the distance from one base to the other.

2. If the distance from one base to the other base is 10 mm long, and each triangle is 1 mm thick, how many triangles would it take to fill up the prism? (Use the drawing above to help you.) © Accelerate Learning Inc. - All Rights Reserved

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Answer:

mm 65

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7L2C Levels of Organization

Math Connections If you filled the triangular prism completely full, you would then know the volume of the prism. Determine the volume of the prism after considering the dimensions of one of the triangle bases. 3. Knowing that the distance from base to base is 10 mm, calculate the volume of the triangular prism. 0.06 mm

0.08 mm

Answer:

mm3

4. To find the volume of the triangular-prism cross-section of the cell, use the formula Volume=Area of the Base×Height of the Prism, or V=Bh. Explain how this formula connects to the model from questions 2 & 3.

Answer:

mm3

When the simple columnar cells get crowded, they take on a pyramidal shape. Keeping the dimensions constant with the triangular prism, an example of the pyramid is shown below. Triangular Pyramid

Triangular Prism Imagine filling up the triangular pyramid full of liquid (or materials commonly found in a cell, such as the nucleus, cell membrane, mitochondrion, etc.). Imagine taking that filled triangular pyramid and dumping the contents into the triangular prism (pictured above, on the right). How many times do you think it would take Ms. Simon to fill up the triangular pyramid and transfer the liquid into the triangular prism until the prism is completely filled?

Your guess:

If “three times” was your guess, you are correct. The volume of the triangular pyramid (with the same height and congruently-sized base as a triangular prism) is exactly one-third the volume of the triangular prism. 5. Using the formula for the volume of a triangular prism, what is the formula for the volume of a triangular pyramid? (Use symbols: V for the volume, B for the area of the base, and h for the height of the pyramid.) 66

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7L2C Levels of Organization

Math Connections 6. What is the volume of the triangular pyramid pictured on the page before? The height of the triangle is 0.06 mm, and its base is 0.08 mm. The pyramid’s height (the distance from the top vertex to the bottom base, forming a right angle with the base) is also 10 mm.

Answer:

mm3

Now let’s investigate the volume of simple cuboidal cells. Help the students investigate volume differences between a rectangular prism and a rectangular pyramid that share a congruent base and height. 0.87 mm

0.042 mm 0.051 mm 7. For the shapes above, the base of the rectangular prism is the same as the base of the rectangular pyramid. What is the area of the base for both the prism and the pyramid?

Answer:

mm2

8. The formula for the volume of a rectangular prism is the area of the base multiplied by the height of the prism, or V=Bh, where B represents the area of the base. Calculate the volume of the rectangular prism.

Answer:

mm3

To demonstrate the relationship between the volumes of a rectangular pyramid and a rectangular prism that have congruent bases and equal heights, imagine filling the rectangular pyramid up with sand and them dumping the sand from the pyramid into the rectangular prism. How many times do you think it will take to fill the rectangular prism with sand?

Your guess:

9. If “three times” was your guess, you are correct. The volume of a rectangular pyramid is onethird of the volume of a rectangular prism. Using the formula for the volume of a rectangular prism, what is the formula for the volume of the rectangular pyramid pictured above? (Use symbols V for volume, B for area of the base, and h for height of the pyramid.)

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Answer:

mm3

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7L2B Levels Of Organization

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK As you study the red blood cells in the picture, think about the different levels of organization in plants and animals. WRITE Explain how the relationship among the various levels of organization in plants and animals. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; • use correct spelling, capitalization, punctuation, and grammar.

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7L2B Levels Of Organization

WRITING SCIENCE

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7th Grade Life Science

7L2C

Interaction of Body Systems

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7L2C Interactions of Body Systems

Student Handout

Name:

Date:

Digestion Experiment Answer the following questions in complete sentences. 1. What happened to the color in each beaker after the iodine was added?

2. What is the difference between the foods that changed colors and the foods that didn’t change colors?

3. What other foods have starches in them?

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7L2C Interactions of Body Systems

Student Journal Name:

Date:

Group:

Interactions of Systems Background After reading the Background information in the Student Guide, answer the following questions. 1.

Which two systems function to help your body move?

Your digestive system functions to break down food particles small enough to be used by the body. Which system would then carry these nutrients to the different parts of the body?

Your lungs are where carbon dioxide and oxygen are exchanged. Which organ of the circulatory system provides the force to move the carbon dioxide to the lungs and then move the oxygen around the body?

Describe how the nervous system and endocrine system work together.

Part I: Body System Card Sort Your teacher will give you a set of Body System Cards. Use the information you learned from the background reading and what you know about organs of the human body to sort the parts of each system to the correct system name. Use the information on the cards to complete the table.

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7L2C Interactions of Body Systems

STUDENT JOURNAL Part I: Body System Card Sort, continued Body Systems

Function

Parts of System

Skeletal System

Muscular System

Integumentary System

Circulatory System

Respiratory System

Digestive System

Nervous System

Endocrine System

Excretory System

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7L2C Interactions of Body Systems

Student Journal Part II: Organ System Links After your group has completed your System Link, list the systems you linked together in order and how they work with the next system. 1. 2. 3. 4. 5. 6. 7. 8. 9.

Part III: Body System Interview 1.

Which system did you chose?

What parts do you contain that make you unique?

Do you work well with other systems? Explain.

What job do you do?

If you stopped working, could the body function without you? Explain.

Why should we hire you over other systems of the human body?

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STEMscopedia: INTERACTIONS OF BODY

SYSTEMS 7L2C

Reflect Imagine your parent just took a dish out of a hot oven without you knowing, and you touched it. What happens next? Your hand jerked away before you were even fully aware of how hot the dish was. Our body systems can and must work together in amazing ways for optimal function and to keep us safe! What is a body system? A body system is a group of tissues, glands, or organs that work together to perform functions that keep an organism alive. All the body systems serve different functions. From moving blood around the body to deliver nutrients and remove wastes to providing support, protection, and movement, the systems of the body keep us alive. That’s why it’s important to keep the body systems healthy and strong. Application Match the following body system with its basic function to review before moving on. cardiovascular

removing toxins from blood

excretory structural support digestive body

moving blood, nutrients, and waste around the

respiratory

processing and responding to the environment

muscular

breaking down food and removing waste

This is the human digestive system. All of the organs shown, including the stomach and intestines, work together to digest food to break it down to the molecules your body needs to get energy.

nervous gas exchange immune movement skeletal

protecting the body from foreign invaders

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STEMscopedia: INTERACTIONS OF BODY

SYSTEMS

Interaction Among Body Systems All of the human body systems work together daily to keep you alive and functioning properly. The body is similar to a complex machine in that if one part does not work properly, some or all of the parts will also be affected.

Look Out Sometimes it is easy to think about the body systems as being separate from one another, but, in truth, none can function without all the rest. No system stands alone. Some might try to argue that certain systems are more important than others, but in actuality, all are equally important in helping the others function. Some might say the nervous system is the most important since it sends and receives the signals necessary to carry out life functions, but the nervous system will not work without oxygen taken in by the respiratory system and delivered by the cardiovascular system. So while the nervous system is in charge of operations, it requires supplies from other systems. Muscular and Skeletal Systems These two systems work closely together to provide the other body systems with support, protection, and functionality. The skeletal system is not just a means of movement and structural support; it is also the source of blood cells for the circulatory and immune systems. The bones would not be able to stand upright or move without the muscular system. The digestive organs, blood vessels, and heart are also made up of muscles. Cardiovascular, Respiratory, and Digestive Systems The respiratory and digestive systems interact with the cardiovascular system to get the necessary oxygen and nutrients delivered to every cell in the body. The blood cells drop off oxygen, and nutrients are absorbed from the bloodstream, which in turn picks up waste from the cells and delivers it to the lungs and kidneys. Cardiovascular, Excretory, and Immune Systems The circulatory system is important for taking waste from the cells and the kidneys of the excretory system, then filtering these wastes out of the blood and removing it from the body. The circulatory system also works with the immune system to deliver white blood cells to wherever they are needed to fight foreign invaders. The circulatory and excretory systems.

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STEMscopedia: INTERACTIONS OF BODY

SYSTEMS

What Do You Think? All systems have importance, but some malfunction occasionally. Think about the different body systems and decide which ones you might be able to live without or with limited functionality. Discuss how it might be possible. Reflexes and Other Involuntary Responses Reflexes are an excellent example of body systems interacting with each other. A reflex is when your body reacts to something, sometimes without you being conscious of the reaction. A reflex you might be glad to have is the amazing connection between your nervous system and your muscles. Because of this lightning fast interaction, we can protect our faces from objects that might hurt us or jump out of the way of danger before we are conscious of it. Another example of an involuntary response most people have experienced is the fight or flight response. If something threatens or scares you, multiple body systems will act together to prepare you for action. Your nervous system will perceive the trigger. Say you hear a loud crash. This will signal your endocrine system to release adrenaline, a potent hormone, into your circulatory system. Your bloodstream will deliver this hormone to all your muscles, allowing them to be ready to fight off a possible threat or run away.

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STEMscopedia: INTERACTIONS OF BODY

SYSTEMS

Connecting With Your Child Body systems interacting with each other to perform everyday tasks may be something most people never notice or take for granted. Together, you and your child can participate in the following activities and brainstorm what systems are working. Procedure: Have your child perform the following activities. After each activity, ask your child which body systems were involved in carrying out the task. Activities: 1. Jumping jacks 2. Smelling a candle 3. Eating a snack 4. Tying a shoe Possible Answers: 1. Muscular, skeletal, respiratory, and cardiovascular 2. Nervous and respiratory 3. Digestive and muscular 4. Nervous and muscular

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7L2C Interactions of Body Systems

Reading Science Name:

Date:

Group:

The Skeletal System 1

Did you know that babies are born with a total of 350 bones, compared to an adult with about 206 of them? The infant bones fuse as the body ages, showing that bones are made of living tissue. The skeletal system is made of all the bones in the human body. A skeleton’s rock-like bones are no longer alive in contrast to the bones in your body. In fact, each bone is a living organ, made of several different tissues. The cells in bones behave the same as other cells within the body. They absorb nutrients and expend energy. Healthy bones are dense and strong.

The skeletal system has five major functions. First, like the internal wooden structure supporting a house, bones are the framework that gives shape and support to your body. Second, bones protect your delicate internal organs. For example, ribs surround the heart and lungs and a skull protects the brain. Third, major muscles attach to the bone and make them move. Fourth, critical to life, blood cells are actually formed in the red marrow of some bones. Marrow is the soft tissue in the center of many bones. Both red and white cells are made in the center of many bones. Red blood cells distribute oxygen to all parts of the body, and white blood cells fight off germs and diseases. Fifth, calcium and phosphorus make bone hard. The skeleton is the place within the body where large amounts of calcium and phosphorus compounds are stored for later use.

Bone is made of living tissue, which explains why a broken bone actually heals. To remain alive, the bone cells depend upon blood. The bone is fed by the blood, which also removes its waste. Deep within a compact bone are the Haversian systems, also known as circular structures. Did you know that upon slicing a bone, you can actually see these systems? They look like the rings of a tree trunk when cut at the tree’s base. Additionally, bones are not smooth, as you might expect. Instead, they are full of pits, round ends, rough spots, bumps, and edges. Without these differences, muscles and ligaments would not be able to attach to the bone. Furthermore, the holes provide gateways for blood vessels and nerve endings to exit the bone.

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7L2C Interactions of Body Systems

Reading Science Continued 4

The shape of a bone generally indicates the function it performs in the body. Can you guess what the longest bone is in your body? It is the femur—the thigh bone. It is actually one-quarter of your height! Deep within the ear, you will find the smallest bone: the stirrup bone. It is usually about one-tenth of an inch long. Another interesting fact is that bone shapes are genetically controlled and will be modified depending upon the work performed by the muscle. Bones adapt to the functions they perform.

There are over 230 moveable and semimoveable joints in the body. A semimoveable joint allows little or no movement, as is seen with bones of the skull. A moveable joint provides for a flexible connection between bones. The body needs joints that provide flexibility with the bones, allowing the body to move back and forth. This is easily seen with the knee. The knee joints work like a door hinge allowing you to move your leg back and forth. Still other bones and joints allow for pivoting, such as the ones in the neck that enable you to turn your head. Additionally, you have shoulder joints that allow the arm bone to move nearly 360 degrees.

Cartilage is a thick smooth layer of cushiony tissue that usually is found at the ends of the bones. It does not contain blood vessels or minerals. As we age, cartilage sometimes wears out, resulting in a common painful condition in older people known as arthritis. Each time they move, they feel intense pain.

Without the skeletal system, we would be like a human beanbag flopping around as one big puddle of skin and organs. Our flexible skeletal system allows us to stand and walk, bend and rotate, and work against the forces of gravity.

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7L2C Interactions of Body Systems

Reading Science

What is the coating, marked by arrows in the diagram shown, at the ends of the leg bones? A

White blood cells

Rock

Marrow

Cartilage

What kind of joint is pictured in the diagram shown? A

A semimoveable joint, allowing back and forth movement

A moveable joint, allowing back and forth movement

A semimoveable joint, allowing twisting

A moveable joint, allowing twisting

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7L2C Interactions of Body Systems

Reading Science 3.

What is the main point of paragraph 3? A

Red blood cells

The skeletal system

The structure of a bone

D Bones, cartilage, and blood vessels

In paragraph 3, which word or words best describes Haversian systems? A

Ligament

Bone marrow

Circular structures

Cartilage

Which sentence would the author disagree with? A

Bones adapt to the functions they perform.

A flexible skeletal system allows mobility for the body.

Bone shapes are genetically controlled and routinely modified depending upon the work performed by the muscle.

Each bone is a nonliving organ comprised of several different tissues.

The skeletal system has many functions. Which of the following body functions does the skeletal system not do? A

Remove germs from the blood

Protect the internal organs

Give shape and support to the body

Produce red and white blood cells

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7L2C Interactions of Body Systems

Math Connections Name:

Date:

Group:

The circulatory system, which comprises the heart, blood, and blood vessels, primarily transports needed substances, such as oxygen, to cells and tissues and carries waste products away from cells and tissues. The healthier our heart is, the better it pumps blood. The more blood-pumping that occurs in our bodies, the more often our cells are able to get what they need to function better and to clear away the waste they do not need. The respiratory system primarily supplies and delivers blood with oxygen to all parts of the body. Through breathing, the body inhales oxygen and exhales carbon dioxide. When you exercise, your heart and lungs work together, helping to pump oxygen and blood faster so you can build stronger muscles. Your target heart rate (THR) is the rate you should strive to achieve when exercising so you don’t overwork or underwork your body. 1.

Take your resting heart rate as soon as you wake up in the morning. Count your pulse for one minute. Do this for three days in a row, and record it in the chart below. Calculate your average resting heart rate for the three days.

Day 1

Day 2

Day 3

Beats per Minute 2.

Average resting heart rate: Calculate your maximum heart rate by subtracting your age from 220. Calculate your heart rate max reserve by subtracting your resting heart rate from your maximum heart rate. Maximum heart rate: Heart rate max reserve:

Calculate the lower limit of your target heart rate. Your lower limit is 60% of your heart rate max reserve. Lower limit of THR:

Calculate the upper limit of your target heart rate. Your upper limit is 80% of your heart rate max reserve. Upper limit of THR:

Calculate your target heart rate by taking the average of the lower and upper limits. Target heart rate:

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7L2C Interactions Of Body Systems

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about the different systems of the human organism. WRITE Explain the main functions of the systems of the human body. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; • use correct spelling, capitalization, punctuation, and grammar.

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7L2C Interactions Of Body Systems

WRITING SCIENCE

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7th Grade Life Science

7L3A

Genes, Chromosomes, and Inherited Traits

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7L3A Genes, Chromosomes, and Inherited Traits

Student Handout

Name:

Date:

As you observe the images above, discuss the following questions with your group. Be prepared to defend your conclusions. 1.

Which set of fruit flies is most likely the offspring’s parents?

What characteristics do you observe that lead you to that conclusion?

What do you know about heredity that leads you to that conclusion?

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7L3A Genes, Chromosomes, and Inherited Traits

Student Journal Name:

Date:

Group:

Background 1.

What is the definition of heredity?

Where is genetic material found in a prokaryotic cell?

Where is genetic material found in a eukaryotic cell?

Part I: What Are Genetic Instructions and Traits? 1.

Put a box around words that mean “genetic instructions” and a circle around the words that mean “traits” in the following sentence: The chef used a recipe to make a delicious, chocolate, five-layer cake.

What traits did your teacher describe for your class to observe and count?

Do you know anyone in your family that has the same results that you do for the traits described by your teacher?

What do you think might be internal traits (those traits that are not so easily observed)?

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7L3A Genes, Chromosomes, and Inherited Traits

Student Journal Part I: What Are Genetic Instructions and Traits?, continued Class Trait Data Table, Total Number of Students Surveyed Trait

Observed

Not Observed

Graph

Graph Key and Percent Observed

Tongue Roll Not Observed

Observed Widow’s Peak Not Observed

Attached Earlobe

Observed Not Observed

Observed Dimples Not Observed

Hitchhiker’s Thumb

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Observed Not Observed

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7L3A Genes, Chromosomes, and Inherited Traits

Student Journal

OFFSPRING B

OFFSPRING A

PARENT 2

PARENT 1

Part II: Pass It On RED

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

GRAY

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

YELLOW

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

BLUE

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

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7L3A Genes, Chromosomes, and Inherited Traits

Student Journal Part II: Pass It On, continued

Do either of the offspring have identical genetic material as compared to parent 1 or parent 2?

Is the genetic material of offspring A identical to offspring B? ___________________________

Why would offspring A have different traits than offspring B if they both have the same parents?

ORANGE

10 11 12 13 14 15 16 17 18 19 20 21 22 23

BROWN

OFFSPRING C

PARENT 4

GROWN UP OFFSPRING BECOMES PARENT 3

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7L3A Genes, Chromosomes, and Inherited Traits

Student Journal Part II: Pass It On, continued 4.

In this simulation, parent 1 and parent 2 make up generation 1. Which individuals make up generation 2 and generation 3? generation 2: ________________________________________________________________ generation 3:_________________________________________________________________

Why can it be stated that offspring C is unique?

Use color-coded evidence from the chromosomes to explain how offspring C could exhibit traits from parents 1 and 2 due to inherited genes.

Explain how traits from parent 1 or parent 2 could show up in a fourth generation of offspring.

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7L3A Genes, Chromosomes, and Inherited Traits

Student Journal Reflections and Conclusions 1.

What governs inherited traits within an individual?

Where is genetic material located?

Describe how the mechanism of heredity allows traits to be passed from one generation to the next.

100

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STEMscopedia: GENES, CHROMOSOMES, AND INHERITED TRAITS

7L3A

Reflect Take a look at the three adult bears shown in these photographs:

Which of these adult bears do you think is most likely to be the parent of the bear cubs shown in the photograph on the right? How did you arrive at your conclusion? Organisms and Inherited Traits Heredity is the transmission of traits from one generation to the next. These include physical traits such as fur color and body shape that are easy to observe. You probably chose the adult black bear (middle picture) as the parent of the bear cubs above. This is because the bear cubs share more physical features with that adult bear than with the other adult bears. Other types of traits are also passed from parents to offspring. These include behavioral traits and biochemical traits. An example of an inherited behavioral trait occurs in migrating butterflies. An example of an inherited biochemical trait is the blood type passed from human parents to their children. Biochemical traits can only be observed by studying the chemical composition of biological samples. Monarch butterflies inherit a behavioral trait that prompts them to migrate.

Genes: The Units of Inheritance Inherited traits are determined by information stored in an organism’s genes. Genes are sequences of DNA that are part of the structure of the organism’s chromosomes. Chromosomes are located in the nucleus of every cell in that organism. An organism has two copies of each chromosome. During sexual reproduction, one copy comes from the organism’s female parent. The other copy comes from the organism’s male parent.

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STEMscopedia: GENES, CHROMOSOMES, AND INHERITED TRAITS

Alleles and Genotypes Because each chromosome is present in two copies, each gene is present in two copies. However, the DNA sequences of the two copies may not be the same. These variations of a gene are called alleles. As an example, suppose that a scientist inspected the chromosomes present in a flowering plant. The scientist might observe something similar to the situation diagrammed below. Alleles for the same gene have been identified on two chromosomes. One allele codes for purple flower color. The other allele codes for white flower color. One allele came from the plant’s female parent. The other allele came from the plant’s male parent. The pair of alleles an organism inherits for each gene determines the genotype of that individual. In the example shown above, suppose the purple color allele is given the abbreviation, P, and the white color allele is given the abbreviation, p. This plant’s genotype for flower color is Pp.

What Do You Think? Suppose a plant has two alleles for purple flowers. What is the plant’s genotype for flower color? What is the genotype for flower color if a plant has two alleles for white flowers? Phenotypes An individual’s phenotype is determined by the traits that are expressed and observed. Suppose that the plant with a genotype of Pp has purple flowers. We say the plant’s phenotype for flower color is purple. The chart below summarizes the possible genotypes and phenotypes resulting from the allele combinations for flower color (purple or white). Remember, in sexual reproduction, an offspring inherits one allele from each parent. Allele Combinations for Purple and White Flowers

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genotype

phenotype

purple

white

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STEMscopedia: GENES, CHROMOSOMES, AND INHERITED TRAITS

Dominant and Recessive Alleles You may have noticed an interesting phenomenon in the chart above. Three different genotypes (PP, Pp, and pp) only produced two phenotypes (purple color or white color). This is because the allele for purple color is dominant and the allele for white color is recessive. Dominant alleles are expressed if they are present. Recessive alleles are only expressed when the dominant allele is absent. Therefore, PP and Pp genotypes have the same purple phenotype. Only the pp genotype has the white phenotype.

If an organism has two different alleles for a trait, such as Pp, it is heterozygous for that trait. If an organism has the same alleles for a trait (PP or pp), it is homozygous for the trait. PP is classified as homozygous dominant and pp is classified as homozygous recessive.

What Do You Think? Study the diagram at the right. It represents four people: two parents and their two children. Parents are indicated by the symbols in the top row. Children are indicated by the symbols in the bottom row. Circles represent females and squares represent males. In this family, only the daughter expresses a particular trait. The other members of the family (unshaded symbols) do not express this trait. Could this trait be dominant, or is it recessive? How do you know?

Key Circle=female Square=male Unshaded=trait not expressed

Shaded=trait expressed

Look Out It is important to remember the differences between traits, genes, alleles, and phenotypes. These terms are often confused. A trait is one particular characteristic such as eye color. The gene is the segment of DNA that codes for that trait. Alleles are the different possibilities for the trait (brown, blue, green.) Phenotype is which one of those possibilities is actually observed in a particular individual. Genetic Variation Recall that each parent contributes a set of chromosomes to a child. This is why children look similar, but not identical, to their parents. However, the set of chromosomes that a child inherits from each parent is random. This is why siblings, other than identical twins, look similar to one another, but not identical. In the case of identical twins, they actually do both inherit the same sets of chromosomes. Humans have 46 chromosomes. This leads to many different possible combinations of chromosomes that each child can inherit.

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STEMscopedia: GENES, CHROMOSOMES, AND INHERITED TRAITS

Career Corner: What does a geneticist do? A geneticist is a scientist who studies the genetic makeup of organisms. Research geneticists study a variety of organisms from single-celled bacteria to worms and fruit flies in order to learn about genes. For example, they might ask questions such as: How many genes are needed to sustain life? Which genes are essential, and which genes can be eliminated without harm to the organism? What does each gene do for the organism? To answer these questions, research geneticists use laboratory techniques to isolate and identify genes at the level of DNA.

Geneticists use DNA maps to analyze genes isolated from living cells.

Clinical geneticists focus specifically on human genetics. They, too, work in the laboratory and use techniques for observing gene structure and function. But, clinical geneticists are often concerned about how genes play specific roles in human health and disease. They want to know which genes are involved in certain diseases and why. Knowing these things can help identify methods for treating these diseases and possibly preventing the diseases from developing in others.

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What Do You Know? Match words from the list below to the appropriate descriptions in the chart. Write your answers in the right column of the chart, directly across from the matching description. Word List: genotype, phenotype, heredity, allele, chromosomes, trait Description

Word

The physical appearance of an individual’s genetic makeup A particular characteristic of an individual The passage of genetic instructions from one generation to the next generation One variation of a particular gene The specific genetic makeup of an individual Contain the genes of an individual Now use what you have learned about heredity to complete the chart below. The allele pairs in the left column represent eye color in fruit flies. R is the dominant color (red) and r is the recessive color (white). Study the chart and fill in the missing phenotypes. Allele Pairs for Eye Color in Fruit Flies Genotype

Phenotype

RR Rr rr

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Connecting With Your Child Genetics: Simulation and Research Run a simulation with your child to explore the possible genotypes and phenotypes of offspring produced from the parental cross shown at the right. Your child should follow this procedure: 1. Gather these materials: a. 2 brown paper lunch bags b. 10 red beads c. 10 blue beads d. A marker 2. Red beads represent the dominant allele, A. Blue beads represent the recessive allele, a. 3. Make up one of the paper bags to represent the female parent. Label the bag, “female.” Place five red and five blue alleles in her bag. What is her genotype? What is her phenotype? 4. Make up the other paper bag to represent the male parent. Place five red and five blue alleles in his bag. Notice that he has the same genotype and phenotype as the female. 5. Without looking, pull one allele from the female bag and one allele from the male bag. This represents their first offspring. Begin a chart to record the genotype and phenotype of this offspring. Place the beads back in their original bags. 6. Shake the bags to mix the alleles and repeat the mating process from Step 5. Record the results as before. Repeat until you have produced 20 offspring. It is unlikely that a single set of parents will produce 20 offspring. However, repeating the process 20 times gives an idea of the likelihood for a particular genotype. For example, if you pull out red, blue (Aa) 10 times, you can say that the likelihood of a child inheriting this genotype is 10 out of 20, or 50%. 7. Ask your child these questions: a. How many of each genotype are present in the offspring? b. How many of each phenotype are present?

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To help your child learn more about heredity, choose a genetic disease to research. Some of the more well-researched genetic diseases include cystic fibrosis, sickle cell anemia, Tay Sachs disease, phenylketonuria, and hemophilia. Instruct your child to research both the nature of the disease, including symptoms and patient outcomes, and the genetics behind the disease (what genes are involved, and why they cause the disease.) During their exploration, your child should also be encouraged to find out how many people are affected, what treatment options are available for them now, and what treatments may be possible in the future. Here are some questions to discuss with your child: • How are genes involved in this disease? • Are there treatments available now for this disease? What are they? • Do scientists hope to find better treatments for this disease in the future? What are they?

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7L3A Genes, Chromosomes, and Inherited Traits

Reading Science Name:

Date:

Group:

The Father of Modern Genetics 1

Between 1856 and 1863, Gregor Mendel conducted over 29,000 experiments in a monastery garden. This curious and observant priest was an avid gardener. He spent many hours gardening. He noticed that the same type of plants would grow in highly predictable ways. What he found out is that heredity happens in a foreseeable manner. Heredity is the passing of traits from parent to offspring. No one noticed his work until 40 years after his death. Biologists found it again while trying to figure out how traits are passed from one generation to another. Our understanding of heredity and genetics is built on his work.

Mendel grew vegetables in the monastery garden. He spent many hours growing peas for the monks of the abbey. While gardening, he noticed that some peas grew on short plants while others grew on tall plants. At the time, most people believed in blended inheritance. If one parent is tall and one is short, blended inheritance predicts a child somewhere in between in height.

However, Gregor Mendel was a perceptive man. He saw that when purebred tall and purebred short peas were cultivated, they only produced tall peas. If the blended inheritance theory were true, a mix of short and tall peas should produce peas that were somewhere in between. That never happened. In fact, a mix of short and tall peas always produced tall peas. The tall trait always won over the short trait. This made no sense. How could short peas keep appearing if it was so easy to erase the short trait? This mystery was solved when the first generation of offspring (F1) were mixed. That usually produced three tall plants and one short plant. The second generation (F2) demonstrated the fact that inherited traits carry on, even when they are hidden from our eyes.

The factors that control traits are called genes. Different forms of genes are called alleles. Hair color is determined by genes. Red hair is a particular allele of the hair color gene. Each organism inherits genetic possibilities, or genotypes. Some of these possibilities are expressed, or observable. It they are visible, they are called phenotypes. Even if an allele is not visible because it is recessive, or hidden by the dominant allele, it is still present. Like the short trait in impure pea plants, it is hiding in the genotypes waiting to be joined with another recessive allele and become visible again.

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Reading Science Continued 5

The discovery of recessive alleles changed how we thought about heredity. Now there could be an explanation for a red-headed child born to brown-haired parents. Each brown-haired parent could carry both the brown-hair and red-hair allele. Since the brown-hair allele is dominant, the parents would each have brown hair. They would still be capable of passing on their recessive red-hair allele. If both passed on the red-hair allele to the same offspring, that child would have red hair.

Generations may pass before recessive alleles are matched with another to become phenotypes. Recessive alleles explain many genetic disorders like sickle cell anemia and Huntington’s disease. They seem like little surprises from nature, but we can calculate the chance that an offspring will have a certain combination of alleles. We can do that using a Punnett square. A Punnett square is a chart that shows all the possible combinations of alleles that can be the product of a genetic cross. This kind of predictive possibility was unfathomable before Mendel’s discovery. It is unfortunate that he never learned how important his work would be for the advancement of science.

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Reading Science 1.

Which words in the passage help the reader understand the meaning of the word avid in paragraph 1? A

What he found out

Many hours gardening

This curious and observant

He noticed

Eye color is also determined by genes. Brown eyes are dominant, and blue eyes are recessive. What must be true for two brown-eyed parents to produce a blue-eyed child? A

One person passes on the blue-eye allele.

They each pass on the blue-eye allele.

One person’s parents are blue-eyed.

One person’s grandparents are blue-eyed.

What can the reader reasonably conclude based on the information in this passage? A

Gregor Mendel was well paid for his research.

Gregor Mendel noticed other things about peas.

Gregor Mendel won a Nobel Prize for his work.

Gregor Mendel hated gardening.

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Reading Science 4.

What can a Punnett square be used to determine? A

The possible combinations of alleles in offspring

What an offspring will look like

The height of offspring

Genetic heritage

Which words in the story help the reader understand the meaning of the word foreseeable in paragraph 1? A

Same type of plants

No one noticed

The passing of traits

Highly predictable ways

What will the result be if a purebred tall pea plant is mixed with a purebred short pea plant? A

A short pea plant, due to chance

A short pea plant, because short is the dominant allele

A tall pea plant, because tall is the dominant allele

A tall pea plant, due to chance

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Math Connections Name:

Date:

Group:

Studying genetics has a multitude of benefits. It helps us identify genetic marks for certain diseases in humans and animals, assists farmers in establishing hardier crops, and predicts patterns of inheritance and indicators in family lines. Inherited traits include expressed external characteristics such as eye color and hair color, and internal characteristics such as blood type. Use the following information to answer questions 1–5. A Punnett Square can assist us in predicting the appearance of certain traits in plants and animals that reproduce sexually. 1.

In 1960, a scientist, Gregor Mendel, used pea plants to determine the dominance of certain traits. In one of his experiments he looked at the inheritance of pod color. Construct a Punnett Square for a pea plant with YY phenotype for a yellow pod cross-pollinated with a pea plant with GG phenotype for a green pod. X

If the Y (yellow pod) allele is dominant over the G (green pod) allele, what percent of offspring will have a yellow pod? What is their genotype?

Suppose two of these offspring were cross-pollinated. Create a Punnett Square to show the potential combinations of genotypes for pod color. X

Calculate each genotype’s percentages. What percentage will have a yellow pod phenotype?

Suppose that the cross-pollination produced 20 offspring. How many of those offspring could be predicted to have green seed pods?

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Math Connections Use the following information to answer questions 6 –11. Punnett Squares can help us predict the probability of certain traits being passed down family lines. Suppose your maternal grandparents had a phenotype of brown hair with genotypes of Bb and BB. Your paternal grandfather has brown hair (Bb), and your paternal grandmother has blonde hair (bb). 6.

Construct the Punnett Squares that represent the possibilities of genotypes for your parents’ hair color. Mom

Dad

What are the possible genotypes for your mother’s hair color? Your father’s hair color?

Knowing each parent has only two possible combinations, construct the Punnett Squares that represent the possibilities of their offspring’s hair color. X

Blonde hair is produced by inheriting double recessive alleles (bb). What is the probability of their offspring having blonde hair?

10. What percentage of their offspring will have a BB genotype for brown hair?

11. How likely is it that the offspring will have brown hair? (Likely, Unlikely, Certain, or Impossible) Support your answer with mathematical reasoning.

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7L3A Genes, Chromosomes, And Inherited Traits

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about the similarities and differences between parents and their offspring. WRITE Explain how characteristics are transmitted from parents to their offspring. Be sure to clearly state your central idea; organize your thoughts; develop your essay in detail; choose your words carefully; use correct spelling, capitalization, punctuation, and grammar.

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WRITING SCIENCE

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7th Grade Life Science

7L3B

Asexual and Sexual Reproduction

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7L3B Asexual and Sexual Reproduction

Student Journal Name:

Date:

Group:

Background 1.

What two factors determine the traits inherited by an organism?

What is asexual reproduction?

What is binary fission?

What are spores?

What is budding?

What is vegetative propagation?

What is sexual reproduction?

Offspring from asexual reproduction are from sexual reproduction are

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Student Journal Part I: Guess Who? 1.

Which organism reproduced asexually?

Were the offspring of this organism uniform (they looked identical to each other and to the the parent) or diverse (they had a variety of appearances)? Explain your answer.

Which organism reproduced sexually?

Were the offspring of this organism uniform or diverse? Explain your answer.

Offspring from the asexual and sexual reproduction may differ in whether they are uniform or diverse. However, they may also share some similarities. What similarities do these organisms share?

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Student Journal Part II: Did You Say Flesh-Eating Bacteria? Draw and label the observations from the patient’s lab work in the petri dishes. Include your analysis of the cell type and prescription. Patient 1: Condition __________________ Type of cell: □ Prokaryotic (no nucleus) □ Eukaryotic (has nucleus) Prescription:

□ Antibiotic □ Antifungal

Patient 2: Condition __________________ Type of cell: □ Prokaryotic (no nucleus) □ Eukaryotic (has nucleus) Prescription:

□ Antibiotic □ Antifungal

2 Patient 3: Condition __________________ Type of cell: □ Prokaryotic (no nucleus) □ Eukaryotic (has nucleus) Prescription:

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□ Antibiotic □ Antifungal

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Student Journal Part II: Did You Say Flesh-Eating Bacteria? continued 1.

What differences did you observe between prokaryotic and eukaryotic cells?

What similarities did you observe between prokaryotic and eukaryotic cells?

Eukaryotic fungi can cause fungal infections. Human cells are eukaryotic. How can this information cause problems with treatment?

Eukaryotic fungi can reproduce sexually, creating diverse offspring. How might this complicate treatment?

Bacteria are prokaryotic and reproduce quickly and asexually through binary fission, during which one cell becomes two cells with identical DNA. How does this reproduction strategy promote survival of the species?

Antibiotics can be very successful in treating bacterial infections. What is it about the reproductive strategy of bacteria that allows antibiotics to be so successful?

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Student Journal Reflections and Conclusions 1.

What type of offspring result from sexual reproduction? How are they different from offspring resulting from asexual reproduction? Explain your answer.

How do scientists determine if offspring result from sexual or asexual reproduction? What evidence would scientists use to arrive at this determination? Explain your answer.

Do some organisms have the ability to reproduce both sexually and asexually? Are they prokaryotic or eukaryotic? Explain your answer using some examples.

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Student Journal Reflections and Conclusions, continued 1.

After a forest fire, plants quickly begin to repopulate the disturbed area. What advantage would the plants that can reproduce asexually have over the plants that only reproduce sexually after such an event?

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STEMscopedia: ASEXUAL AND SEXUAL REPRODUCTION

7L3B

Reflect Imagine a gardener checking on his growing plants at the beginning of spring. He notices a few tiny insects eating some of his plants. The gardener isn’t worried—a few insects are not a concern. But when he comes back several weeks later, his plants are covered in these small insects. There are at least ten times as many insects as there were several weeks ago! Where did all of these insects come from? How do organisms make more of their species? Reproduction produces offspring. Reproduction is a process by which an organism produces offspring, or young. All organisms reproduce. If they didn’t, no species would survive past a single generation. Reproduction allows organisms to pass on their traits, or characteristics, to their offspring. Parents pass on their traits through their genetic material, or DNA.

The tiny insects developing inside these eggs will grow into adult insects.

Asexual reproduction requires one parent. Asexual reproduction is a type of reproduction in which one parent makes an exact copy of itself. The parent passes its genetic material to its offspring. Therefore, the offspring have the same traits as their parent and as each other. The offspring are uniform, or the same. Think of it as making a copy on a copy machine. The parent is like the piece of paper you put into the machine. The offspring are like the copies that come out. The offspring, like the copies, all look like their parent and like each other. Most prokaryotic organisms reproduce asexually through binary fission.

There are different forms of asexual reproduction. Prokaryotic organisms, such as bacteria, go through a process called binary fission. First, a single-celled bacterium makes a copy of the DNA it has in its cell. Then, the bacterium splits in half, forming two cells. Each cell gets a copy of the original DNA.

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Prokaryotic: describes a simple, one-celled organism that lacks a nucleus and other membrane-bound organelles

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Eukaryotic organisms reproduce asexually in several ways. Fungi, such as mushrooms, form spores. Spores are tiny reproductive structures that contain a copy of the parent DNA. Some organisms reproduce by budding. In budding, a smaller version of the parent organism grows out of the parent. Eventually, it separates from the parent and begins to function on its own. This would be similar to another person growing out of your body!

Eukaryotic: describes an organism that has cells with a nucleus and other membrane-bound organelles

Hydra are tiny aquatic animals. The hydra shown to the left is reproducing by budding. The arrow is pointing to the offspring that is growing out of the parent hydra toward the front of the image.

Plants can reproduce asexually through a process called vegetative propagation. An entire new plant can grow out of a portion of the parent plant. For example, if you removed a part of the stem and leaf and put it in water, it would form roots and grow to be an adult plant. It would be an exact genetic copy of its parent. Have you ever noticed the “eyes” of potatoes? The eyes are actually buds that sprout new leafy branches. This is an example of asexual reproduction. If you planted the sprouting parts, they would eventually grow into adult potato plants.

The sprouting buds of this red potato are an example of vegetative propagation.

Look Out Bacteria, fungi, and plants are not the only organisms that reproduce asexually. In some animals, like fish, reptiles, and amphibians, an unfertilized egg can develop into a full-grown adult. This offspring would only have a copy of the female’s DNA. For example, in some insects called aphids, asexual reproduction can occur when an unfertilized egg develops inside the female. Once the egg has fully developed, the female gives birth to a genetically identical offspring!

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Sexual reproduction requires two parents. Unlike asexual reproduction, sexual reproduction requires a male and female. Each parent contributes half of their genetic material, or DNA, to the offspring. The female contributes her DNA in an egg cell. The male Dominant trait: if contributes his DNA in a present, determines the sperm cell. When the egg trait of an organism and sperm combine, they form the new offspring. Recessive trait: a Offspring may look similar trait that is masked if a These puppies are a product of to their parents, but they are dominant trait is present sexual reproduction. They each not exact copies. In sexual have a unique mixture of their reproduction, each offspring parents’ traits. has a mixture of its parents’ traits. Parents may pass on dominant traits or recessive traits to their offspring. Each offspring may be different from its siblings. For example, suppose the father in a human family does not have freckles, but his wife does. Among their children, one child might not have freckles, but the other children might have them. In sexual reproduction, the offspring have a unique combination of their parents’ traits. This is why organisms that reproduce sexually have diverse offspring.

What Do You Think? Take a look at the two graphic organizers below. Which graphic organizer best represents asexual reproduction? Which graphic organizer best represents sexual reproduction? Explain your answers.

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Getting Technical: Cloning Plants Remember that vegetative propagation is a method of asexual reproduction used by plants. Agritechnologists have learned how to use vegetative propagation in the laboratory to make many copies of crop-producing plants at once. An agritechnologist is a scientist who works with technology associated with agriculture, or farming. In the lab, the scientists take cuttings of a crop plant they want to clone, or copy. They might take a whole stem, leaf, or even just a few plant cells. They place the cuttings in test tubes. The test tubes contain water and nutrients and are exposed to light. The cuttings begin to grow roots, leaves, and other structures. They can be planted in the ground and will grow into full-sized crops. Through this method, an agritechnologist can get thousands of young plants from a single adult plant. This method can produce a lot of plants, which is helpful when a farmer is trying to grow crops. However, plants produced asexually are genetically identical. If the adult plant is vulnerable to a disease, all of its clones will also be vulnerable to that disease. A disease could easily wipe out an entire farm’s crops.

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What Do You Know? Use what you know about asexual and sexual reproduction to sort the following terms into the correct column. If the term is related to asexual reproduction, write it in the column on the left. If the term is related to sexual reproduction, write it in the column on the right. If the term is related to both types of reproduction, write it in both columns. Once you have sorted the terms, give a short explanation as to why you put each term in a particular column. Terms: DNA, budding, male and female, one parent, unique, spores, uniform, traits, egg, and sperm

Asexual Reproduction

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Sexual Reproduction

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Connecting With Your Child Asexual Reproduction in Plants To help your child learn more about asexual reproduction, test the vegetative propagation capabilities of a household plant. Choose a common household plant such as the spider plant (scientific name: Chlorophytum comosum). Try vegetative propagation using several different parts of the plant such as a piece of stem, a piece of root, a leaf (with no stem), a leaf with some stem, and the tip of a leaf. Place a toothpick on either side of your plant part (or in the case of the leaf, put the toothpick right through it). Then, place the plant part in a cup of water and position the toothpicks so a portion of the plant part is suspended in the water. Ensure the plant part is not totally submerged and that it has access to light and air. Change the water every few days to prevent it from getting stagnant. Observe how long it takes the plant to start growing, and note if the plant part does not grow at all. You and your child could also try planting the plant parts in some potting soil to see if that changes your results. You can also try this with a potato that has sprouted or an avocado pit. Here are some questions to discuss with students: 1. Which parts of the plant successfully formed new plants? 2. How does the DNA in the new plants compare to the DNA of the parent plant? 3. Why might this strategy be an advantage for plants in the wild? 4. How might gardeners use this method to populate their gardens?

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Reading Science Name:

Date:

Group:

Like Father, Like Mother 1

Landon glances across the dinner table. He thinks to himself that his father’s curly hair looks just like his own. He wishes his hair were straight like his mother’s because he thinks he looks better with straight hair. Landon works hard to make it straighter. He uses hair gel and combs it straight, but it usually curls right back up. He has his mother’s nose, but not her hair. Emily, his sister, is also the result of the combination of the DNA from both of his parents. The process of mixing genetic material from two parents to create offspring is called sexual reproduction. Most eukaryotic organisms, like Landon, are formed through the process of sexual reproduction. Emily has straight hair like their mother’s. Landon realizes that he and Emily are evidence that sexual reproduction creates diverse offspring.

Landon’s dinner plate is filled with one of his favorite foods: mashed potatoes. The potatoes are fresh from his grandmother’s garden. He remembers helping her get ready to plant the potatoes in early spring. They cut potatoes into several pieces and planted the pieces in a straight row in the garden. When these eukaryotic plants came up, he noticed that each plant looked like all the others. These identical offspring with uniform traits are the result of asexual reproduction. Landon’s grandmother grew new potatoes by cutting whole potatoes into smaller pieces. This is a type of asexual reproduction called vegetative propagation.

After dinner, Landon wants to go watch television. His mother insists that he first put the leftover food into the refrigerator. Perhaps she knows that the cool temperature inside the refrigerator would stop the growth of bacteria. Bacteria, which are prokaryotic, can reproduce asexually in as little as 20 minutes. This rapid asexual reproduction, called binary fission, would produce thousands and thousands of identical bacterial cells. They could cause Landon’s tasty leftover food to spoil before the end of his favorite show.

Landon finishes up the dishes and puts away the leftovers. As he sets the last dinner glass back into the cupboard, he catches a glimpse of his curly hair in his reflection. He thinks to himself that his mother’s nose and his father’s hair are actually a good combination. It looks pretty good on him.

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Reading Science 1.

Which of these statements best describes Landon and Emily? A.

Both are the product of asexual reproduction.

Emily is a prokaryote, and Landon is a eukaryote.

Landon and Emily are identical.

Landon and Emily are eukaryotic products of sexual reproduction.

Which of these explains why Landon has his father’s curly hair and his mother’s nose? A.

He is prokaryotic.

Landon and Emily are identical.

His father is older than his mother.

He was formed by binary fission.

Based on the context, vegetative means – A.

sexual reproduction.

binary fission.

growing.

organisms.

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Reading Science ___1 ___

___2 ___

Diverse Offspring

Identical Offspring

Two Parents

Most Eukaryotes

One Parent

Plants: Vegetative Propagation

Bacteria: __3 __

Examine the graphic organizer shown. Which phrase is the best label for box 2? A.

Sexual Reproduction

Asexual Reproduction

Binary Fission

Prokaryotic Cells

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Reading Science 5.

What is the best summary of this passage? A.

Organisms reproduce through sexual or asexual reproduction.

Rapid sexual reproduction is binary fission.

All eukaryotic plants look the same.

All things begin through asexual reproduction.

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Math Connections Name:

Date:

Group:

Mrs. Creote is helping her seventh grade science class understand differences with the genetics of offspring for species that reproduce asexually (reproduction with one parent) or sexually (reproduction with a female and a male parent). The students in Mrs. Creote’s class are trying to determine benefits and detriments to both types of reproduction. Thus far, the class has learned that some organisms procreate asexually at an extremely fast rate. This allows for these organisms to populate a given environment quickly and can aid in their ability to avoid extinction or population decline. A downfall to asexual reproduction is that there is no diversity in an organism’s offspring. All progeny from an organism that reproduce asexually will be identical to the parent organism. This lack of diversity is a problem during times of competition, predation, and natural selection. An organism that reproduces sexually is disadvantaged by a slower rate at which propagation occurs, but these same organisms are more richly diversified and benefit from characteristic traits that can help them adapt and survive in their particular environments. Help the students in Mrs. Creote’s class answer math questions about the reproduction rates of varying organisms as well as solve questions about diversity in offspring.

Organism Protists Fungi Rotifers

Populations of Various Organisms Over Time Initial Population Population 1 Month 80 240 55 220 175 1050

Population 2 Months 720 880 6300

The organisms in the above table are capable of reproducing asexually. A scientist monitored the rate at which each organism reproduced over the course of two months after an initial count of a sample population. Use the table above to help you answer questions 1-6. 1.

Based on the rate of reproduction, how many organisms would scientists expect to see in the fungi population after 3 months of reproduction if the initial population started with 5 organisms.

Rotifers are near-microscopic organisms that live in water. During times of low population, Rotifers practice asexual reproduction. Calculate how many organisms the scientist would expect to see in the rotifer population after 6 months of reproduction if the initial population started with 12 organisms.

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Math Connections Use the table from the previous page to help you answer questions 3-6. 3.

Protists are found almost anywhere where there is water. Using the reproduction rate from the table, calculate how many organisms the scientist would expect to see in the protist population after 9 months of reproduction if the initial population started with only 7 organisms.

Some rotifers are capable of also producing sexually and typically do so when their population is plentiful. By changing to sexual reproduction, these rotifers can build diversity to help sustain their population through environmental challenges. The scientist studying this table believes that once the rotifer population exceeds 50,000 they will stop reproducing asexually. During which month, after the initial population shown, can the scientist expect to see a switch in the rotifers’ reproduction style?

Using the information in the table on the previous page, during which month will the fungi population exceed 10,000?

Using the information in the table on the previous page, during which month will the protists population exceed 125,000?

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Math Connections Mrs. Creote designed a lab to help her students understand the probability of sexually reproducing rats passing on certain characteristics to their offspring. Mrs. Creote explained that the data collected below could help predict, for a certain population of black or white haired rats, the probability of an offspring being born with white hair.

Use the information above to answer questions 7-9. 7. How many observations were made in this population of rats? 8.

What percent of the population is born with white hair?

Based on this percent, what number of rats would you predict would have white hair if you made 96 observations in this population?

The table below is data collected by another class. For each population of rats found in different areas in the city, the students observed 40 rats. They recorded their data in the table below. Number of White-Haired Rats in Areas A-G of the City Area A B C D E F White-Haired Rats 10 11 11 12 11 9

G 7

Use the table above to answer questions 10-11. 10. Using this data, what is the mean number of white-haired rats for the areas observed? Round to the nearest hundredth.

11. What measure of central tendency could best represent this data? Support your reasoning with mathematical proof.

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7L3B Asexual and Sexual Reproduction

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about the role of asexual reproduction in the birth of identical twins. WRITE Explain how the relationship between type of reproduction, asexual or sexual, and the uniform or diverse offspring that type of reproduction may produce. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; • use correct spelling, capitalization, punctuation, and grammar.

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7L3B Asexual and Sexual Reproduction

WRITING SCIENCE

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7th Grade Life Science

7L3C

Selective Breeding

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7L3C Selective Breeding

Student Handout

Name:

Date:

Selective breeding is a process in which humans choose the genetic traits they want in the offspring of a plant or an animal. Parent organisms with the desired genetic traits are chosen to breed with each other to increase the chance that the offspring will have the desired traits. Over several generations, selective breeding can produce changes in the genetic traits of organisms, resulting in a new breed or variety in a species. Humans have used selective breeding to develop a wide variety of breeds in some species such as dogs, cattle, cats, tomatoes, and apples. Instructions: Choose the parents that would be most likely to produce offspring with the desired traits. Male Parents Female Parents

1 2

5 6

3 4

7 8

Desired Traits in Offspring

Parents

Black, short fur White, long fur Black, long fur White, short fur Identify the genetic trait(s) that occurred due to selective breeding as shown in the pictures. 1. Genetic Trait(s) _______________________________________________ 2.

Genetic Trait(s) _______________________________________________

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7L3C Selective Breeding

Student Journal Name:

Date:

Group:

Selective Breed (Artificially Selecting Dogs) Part I 1.

Which of the dogs below would you selectively breed to produce offspring that would be most effective in scaring away a feral hog in southeastern New Mexico? Explain.

Tell why you would want that trait in your dog and write it in the Importance column. Physical Trait

Function

Importance

1. above average number of olfactory receptors smell 2. above average number of eye cells called rods

sight

3. long pointed ears

hearing

4. long legs

speed

5. large heart

endurance

6. large muscles

strength

7. coat color

camouflage

8. long/short hair

body temperature

Behavioral Trait

Function

9. trainability

high/low

10. disposition

mean/friendly

11. bark

loud/quiet

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Importance

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7L3C Selective Breeding

Student Journal Part II

Circle the form you choose next to the trait. For traits that you do not think will affect your breed’s ability to help the scientist, circle “any.” Physical Trait

Form

1. olfactory receptors

above average

average

below average

any

2. number of eye cells

above average

average

below average

any

3. long pointed ears

above average

average

below average

any

4. long legs

above average

average

below average

any

5. large heart

above average

average

below average

any

6. large muscles

above average

average

below average

any

7. coat color

above average

average

below average

any

8. long/short hair

above average

average

below average

any

9. trainability

high

average

low

any

10. disposition

vicious

compatible

meek

any

11. bark

very loud

average

quiet

any

Behavioral Trait

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7L3C Selective Breeding

Student Journal 1.

Which traits did you choose that would have the above average form?

Why did you choose those traits?

Which traits did you choose to have any form?

Why did you choose those traits?

The two dog breeds I have choose to mate are:

The two traits I think are the most important for the new breed to inherit are:

The breed of the mother is .

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and

. The breed of the father is

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7L3C Selective Breeding

Student Journal Use the chart below to keep track of your puppies’ traits. Physical Trait

Puppy 1

Puppy 2

Puppy 3

1. smell 2. sight 3. hearing 4. speed 5. endurance 6. strength 7. coat color 8. hair length Behavioral Trait 9. trainability 10. disposition 11. bark 1.

What is the probability of any of your puppies getting the mother’s trait?

What is the probability of any of your puppies getting the father’s trait?

Why is this true?

Which of your puppies do you think would be best for the assigned task?

If you were to conduct the dog breeding for another generation, which pups would you select to be the parents? (Don’t select brothers and sisters!)

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STEMscopedia: SELECTIVE BREEDING 7L3C

Reflect If you were told to buy a dog, what would you think about? Would you think about the breed you want? The characteristics you want your dog to possess? Or just as long as the dog showed affection toward you, would you care? Scientists describe dogs’ evolution as selective breeding. Selective breeding is defined as the favorable traits that a breeder wants to have passed on to the next generation. Careful breeding can result in these favorable traits being passed on from the parents to the offspring for several generations or to create a whole new breed. Some examples of modern characteristic crossing can be seen in modern day plant crossings such as broccoflower. Broccoflower is a cross between broccoli and cauliflower. Neither broccoli nor cauliflower existed prior to agriculturists breeding wild mustard plants for various traits.

Selective breeding has created the Spanish water dog.

Another example is the modern Spanish water dog. This breed of dog was created from crossing a shepherd with a poodle. This combination created a herding dog that is more stocky, shorter in stature, and hypoallergenic. What other crossings have created modern day breeds, foods, or items that you see or have? Make a short list below. Why Is Selective Breeding Important? If mankind did not use selective breeding over many thousands of years, we would not have many of the modern day species or breeds or items we call “everyday.” We wouldn’t have corn, wheat, domesticated animals (cats, dogs, horses, cows), or cotton fabric made from the finest cotton species, etc.

Domesticated animals.

Ancient corn versus modern corn.

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Ancient fabric versus modern fabric.

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STEMscopedia: SELECTIVE BREEDING How Have We Arrived at New Populations, Species, or Breeds? Each population, species, or breed arrived at its modern point as a result of unique variations: inherited traits that have gradually changed over time as they were passed on from one generation to the next. Environmental changes and selective breeding have helped variation through selective pressures. Some variations within a population or species are a result of gene mutations. Genes are segments of DNA found on chromosomes that determine the expression of the inherited traits received from the parents’ genetic makeup that is passed on through egg and sperm. Variations can result from this genetic mix-up (fertilization of egg and sperm), from random mutations, or changes in DNA, or from external pressures (radiation, chemicals). Evolution can play a role in creating variation within a population or species. Survival of the fittest is a notion that the individuals in the population that best allow the species to survive in their given environment with the given resources available will be able to reproduce and create viable offspring—that is, offspring that can reproduce and have offspring of their own. Finally, environmental changes or selective breeding have driven many of the modern species we know of. Environmental changes have created the polar bear as a lineage of the grizzly bear. Both are genetically identical, except the polar bear has adapted to an arctic environment with adaptations that allow it to survive, and the grizzly bear has adapted further to the forest environment. If these two species met, they could breed and have offspring. This breeding results in what we call the grolar bear (or grizzly bear). What Is One Way That Humans Have Benefited From Selective Breeding? One way humans have benefitted from selective breeding is through the creation of modern domesticated animals. Through breeding efforts, ancient farmers had horses and oxen that could plow their fields to prepare them for agricultural use or to harvest crops; they had domesticated dogs for protection; and they had dog sled teams and stagecoach horses for the transportation of goods.

Oxen

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Gene: segment of DNA on a chromosome Adaptation: characteristics that allow a species to survive and reproduce

Stage coach

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STEMscopedia: SELECTIVE BREEDING Look Out Many animals and plants are becoming labeled as “harmful,” although we’ve been selectively breeding them for thousands of years. This labeling is called genetically modified organisms, or GMOs. GMOs are nothing more than organisms that have been selected because of their characteristics and then bred to produce better offspring. For example, ancient corn did not provide many nutrients or enough kernels per cob. Through selective breeding, Native Americans, pioneers, and modern man have been able to produce a crop that is higher in nutrition and produces 200–400 kernels per cob. Be informed before placing judgment on items that could save thousands of lives by producing food, medicines, or more.

What Do You Think? Look at the two pictures to the right, can you identify the original breeds/species that created them? What characteristics do you notice? What other species/breed has those same/separate characteristics? Ligers come from crossing lions and tigers. Papples come from crossing pears and apples. In nature, neither of these crossings would occur, but thanks to scientists and agriculturists, these breeds/species exist.

Liger

Career Corner: Farmer As more and more land is consumed by housing, stores, and parking lots, there doesn’t seem to be enough land left to grow the crops and herds that will feed the growing human population. How will this happen then? How will we feed all of the people on the planet? Farmers have been working closely with geneticists and scientists to figure out how to yield more food and increase its nutritional value from the same size crop.

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Papple

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STEMscopedia: SELECTIVE BREEDING Try Now Take some time to explore the foods in your pantry, fridge, and house. 1. Identify two plant-based products and two animal-based products. 2. Take a photograph or draw a detailed, colored picture of four species/items. 3. Can you identify the four organisms’ origins? That is, how did these modern day items/species come about? (Research may be required.) 4. Using the Internet, can you identify the four organisms’ evolutionary pathway to become what you have in your pantry, fridge, or house? 5. Can you make a prediction as to how these same items might have to be changed to feed more people?

Prediction

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STEMscopedia: SELECTIVE BREEDING What do you know? Not everything we see in organisms around us is due to selective breeding. Nature also can change traits in species over time. For each example trait, state if it is due to selective breeding and then what could be a possible advantage of such a trait, either in nature or to humanity. Example Trait

Selective Breeding? (yes or no)

Advantage of Trait

Cows produce more milk than their calf needs.

Camels can go long periods without drinking water.

Leaf bugs look nearly identical to tree leaves.

A cactus is covered in spines.

Apples have large, sweet fruit.

Some dog breeds are excellent retrievers.

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STEMscopedia: SELECTIVE BREEDING Connecting With Your Child A Look in Your Home/Neighborhood To help your child learn more about selective breeding, take them on a trip through your home or neighborhood. As students learned in the lesson, selective breeding is a way that humans have manipulated natural species to create modern day species. For this activity, you should note all of the species/breeds/items that your child thinks has been modified since ancient times to modern times. Explain to your child that there is no right or wrong answer here, that they are simply listing these items for now. If you do not have access to a computer, locate one you can have your child use for the rest of this activity. Have your child take the list you generated to the computer and run a basic search of the history of each item’s modernization. That is, did each item have an ancient ancestor that was selectively bred to create the modern versions your child saw on your trip? Here are some questions to discuss with your child: 1. Are there many types of selective breeding we came into contact with on our trip? 2. Why would these species/breeds have been selectively bred? 3. What types of species/breeds might have had the same type of pressure to be selectively breed? 4. What do you think each species’/breed’s future will entail? What will be selectively bred within each moving forward in time? 5. What is one of these species/breeds that will be crucial to the human race’s ability to survive in a future that requires more?

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7L3C Selective Breeding

Reading Science Name:

Date:

Group:

Corn, Dogs, and Genes 1

Have you ever heard that all dogs are related to wolves? For some dogs, such as huskies, German shepherds, and akitas, the resemblance to wolves is quite striking. You can see how they may be related. But what about other dogs? Pugs look nothing like wolves. Neither do Chihuahuas, dachshunds, or toy poodles. Yet these dogs are also distant relatives of the wolf. So how did we get from wolves to toy poodles? The answer is artificial selection. Humans change specific characteristics of organisms by a process known as selective breeding.

How have humans been able to choose which traits of organisms are passed onto offspring? Selective breeding is a process in which humans choose the genetic traits they want in the offspring of a plant or an animal. These genetic traits are determined by the genes found in DNA that are passed from parent to offspring in each generation. Parent organisms with the desired genetic traits are chosen to breed with each other. This increases the chance that the offspring will also have the desired traits. Over several generations, selective breeding can produce changes in the genes of organisms that can result in a new breed or variety within a species. Humans have used selective breeding to develop a wide variety of breeds in some species, such as dogs, cattle, corn, and apples.

Grains are an example from very early in human history. People would selectively breed certain types of grains to grow more bountiful crops. They would choose plants with the traits that they desired. By choosing those traits, people were then able to change the gene pool of the plant to get populations that they wanted. Let’s use corn as an example. The corn that we know today grows on very tall and sturdy green stalks. Each stalk has several large ears of corn. Each ear has outer layers of tough green leaves to protect the hundreds of beautiful yellow kernels found underneath. The corn that we know takes two hands to hold and eat. A person can have a fairly good meal with one ear of corn. But the corn of prehistoric times did not look at all like the corn that we use for food today. Prehistoric corn looked much more like modern day wheat. It grew on small stalks, and the kernels were not protected by thick green leaves. So how did it change from a wheat-like plant to what we know today? Selective breeding.

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7L3C Selective Breeding

Reading Science 4

The change began when people started the practice of agriculture, or growing their own crops. The theory goes that they began to notice that certain plants had different traits than other plants. Some plants had larger fruits. Some plants had stronger stalks. Some plants grew taller. So people began to use only the seeds from the plants that had the traits that they wanted. In other words, they chose the plants with the genes that they wanted. In the case of corn, people most likely only planted the seeds of those plants with the larger kernels. In other words, they selectively bred the plants that had the genes that they wanted, such as the gene for larger kernels. With each new generation of corn, only those plants with the largest kernels were replanted. Over generations, corn grew larger and larger kernels. Several thousand years later, selective breeding changed the gene pool of corn and created the corn that we know today.

Let’s go back to the dog example. Dogs have been documented to have been a part of human culture for at least 7,000 years. Archaeological evidence shows that early humans domesticated wolves perhaps as far back as 20,000 years ago. Early humans likely adopted orphaned wolves to keep for both protection and for help with hunting. A modern-day experiment called the Farm-Fox Experiment explores how species of animals can become domesticated. Certain individual animals show less fear toward humans. These animals are bred to animals with this same trait. Their offspring also have less natural fear of humans. Over many generations, the fear of humans can actually be bred out and replaced with affection for humans. In this way, animals can be domesticated. Therefore, it is hypothesized that a similar process occurred when early humans domesticated wolves into the dogs that live with us today.

The domesticated dog did not change much for many thousand years. However, as civilization changed, so too did the need for different types of dogs. This led to the many different breeds of dogs that we see today. Dogs that were very good at hunting were only bred to other dogs that were very good at hunting. This led to a variety of hunting dogs, from bird dogs to big game dogs. As towns and cities grew, there was greater need to get rid of rodents. In these cases, small dogs that could fit in holes and under buildings were greatly desired. These dogs also had to be fierce in temperament. Therefore, dogs with these traits were selectively bred, leading to breeds such as the terriers. As society changed, those from wealthy families desired small and pretty dogs to play with. So dogs were selectively bred with those that were kind, had silky coats, and could be carried under the arm. This led to breeds such as the toy breeds.

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7L3C Selective Breeding

Reading Science 7

The domestication of animals and selectively breeding crops have helped people. There are other ways that we have altered the genes of organisms to benefit society. Advances in modern science have allowed genetic outcomes to be changed through artificial selection in other ways. In gene therapy, DNA itself is used to help fight specific types of diseases. In the most basic sense, properly working genes are used to replace mutated genes. Somatic gene therapy works to treat the nonreproductive cells of people. Therefore, it can only be used for individuals with a disease. Clinical trials look promising, but gene therapy has not yet been shown to completely correct genetic disorders. Who knows where this next level of artificial selection could take us with future studies. One day we may be able to select gene treatments that cure any type of disease!

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7L3C Selective Breeding

Reading Science 1.

Humans have the ability to change the characteristics, or traits, of organisms over time. What is this process called? A.

Selective breeding

Artificial selection

Gene therapy

Both A and B

Which of the following statements is true regarding selective breeding? A.

Selective breeding only works in plants.

Selective breeding produces changes in genes.

Selective breeding only works in animals.

All of the above.

Which of the following statements is NOT true? A.

The corn that we grow today has not changed since prehistoric times.

Early humans planted seeds from corn plants with large kernels.

It took many generations for corn plants to change.

Humans have selectively bred many different types of crops.

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7L3C Selective Breeding

Reading Science 4.

How has selective breeding changed the wolf into the many different breeds of domestic dogs that we know today? A.

Animals with the traits that were desired were bred to each other.

As civilization changed, so did our need and desire for different types of dogs.

The fear of humans was bred out of wild wolves.

All of the above

Which of the following statements about gene therapy is not true? A.

Functioning genes are used to replace mutated genes.

Gene therapy can cure any disease.

Somatic gene therapy only works on individuals.

Therapy is another form of artificial selection.

Imagine that a student wants to breed a species of rose that has a wonderful smell. The student has many different types of roses, but none of the individual roses has the wonderful smell that the student wants. What is the best way to go about breeding a pure species rose with the trait that the student wants? A.

Breed one generation of roses, and only use those that have the best smell from that generation.

Breed many generations of roses, only choosing the parent plants and offspring that have the best smell in each generation.

Breed the roses with another species of flower that smells good.

If none of the roses has a good smell, then the student cannot breed a rose with a good smell.

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7L3C Selective Breeding

Math Connections Name:

Date:

Group:

In selective breeding, the favorable traits to be passed on to the next generation are chosen by the breeder. Careful breeding of food crops such as corn and wheat have resulted in plants that yield more food per acre. Selective breeding of such domestic animals as dogs have led to incredible diversity from their wolf ancestors. Suppose we wanted to create a breed of rabbit with a spotted coat and stand-up ears. We are starting with two parents. One parent has a solid coat with stand-up ears. The other has a spotted coat with floppy ears. The stand-up ears are a dominant genotype. The spotted coat is a dominant genotype. Breeding Round 1: Each parent will only pass one allele on for each gene. The possible combinations are listed below: Parent 1 – Solid coat (ss) & Stand-up ears (Ee) Parent 2 – Spotted coat (Ss) & Floppy ears (ee) Parent 2 Combinations

Parent 1 Combinations

1. Fill in the Punnett Square with the possible offspring from the two parents. 2. What percentage of this breeding round would result in rabbits with spotted coats and stand-up ears?

sE se

3. What two genotypes resulted in the intended new breed?

sE se

Breeding Round 2: In the next round of breeding, they choose to breed two of the rabbits from the litter with the double-dominant alleles for spotted coats (SS) and stand-up ears (Ee). Parent 2 Combinations

Parent 1 Combinations

SE SE Se SE

4. Fill in the Punnett Square with the possible offspring from the two parents. 5. What percentage of this breeding round would result in rabbits with spotted coats and stand-up ears? Breeding Round 3: In the third round, the parents choose two of the rabbits with double-dominant alleles from both spotted coats (SS) and stand-up ears (EE).

6. What percentage of the litter would have spotted coats and stand-up ears?

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7L3C Selective Breeding

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about the different traits possessed by living things. WRITE Explain how selective breeding can result in desired traits of plants and animals. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar

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WRITING SCIENCE

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7th Grade Life Science

7L4AB

Interactions, Matter, and Energy in Ecosystems

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7L4AB Interactions, Matter, and Energy in Ecosystems

Student Handout

Name:

Date:

Use the three steps below to draw a diagram to explain the flow of energy through a food chain. 1.

What is the original source of all energy in a food chain? Draw this first.

Choose four organisms that might be related through a food chain. Add these organisms to the diagram.

Place arrows in between each part of the food chain. What do the labels represent? Label each arrow, describing what it represents.

Add a caption to explain your food chain diagram.

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7L4AB Interactions, Matter, and Energy in Ecosystems

Student Journal Name:

Date:

Group:

Observe each picture. Carefully consider the information provided and decide if the organism in or on the host organism is helping, harming, or not affecting the organism. Place a check in the correct column. Leave the “Complete After Reading” column blank for the class discussion. Data Collection Table Picture

Help

Harm

Not Affected

Complete After Reading

Clownfish in anemone Bee on flower

Tick on arm

Egret on deer Barnacle on whale Remora fish on shark Plover bird on crocodile Ladybug on plant Brown-headed cowbird eggs in another bird’s nest Athlete’s foot on human foot © Accelerate Learning Inc. - All Rights Reserved

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7L4AB Interactions, Matter, and Energy in Ecosystems

Student Journal Name:

Date:

Group:

Background 1.

What is a food chain?

What do the arrows in a food chain represent?

Where do organisms get the energy they need to survive?

Producers: Primary Consumers: Secondary Consumers: Decomposers: 4.

What is a food web?

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7L4AB Interactions, Matter, and Energy in Ecosystems

Student Journal Part I: Diagram the Energy Flow Through a Food Chain 1. Draw a diagram of the model you created that shows how energy flows through a food chain. Use arrows to show the energy path flowing from one organism to another.

2. Use the information on the Organism Cards to list the parts of your food chain below. Example: the Sun = energy source

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7L4AB Interactions, Matter, and Energy in Ecosystems

Student Journal

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Desert

Forest

Marine

African Grassland

Ecosystem

Link 1

Link 2

Link 3

Link 4

Link 5

Part II: Comparison Table

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7L4AB Interactions, Matter, and Energy in Ecosystems

Student Journal Part III: Diagram the Energy Flow Through a Food Web Draw a diagram of the model you created that shows how energy flows through a food web. Use arrows to show the energy path flowing from one organism to another. Include a legend to provide details about color representation. For example, the green lines show energy flowing from plants.

Legend

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7L4AB Interactions, Matter, and Energy in Ecosystems

Student Journal Part III: Diagram the Energy Flow Through a Food Web, continued 1.

What do the lines represent in your food web model?

What is the role of a decomposer in a food chain or web?

How many different relationships did you discover in your food web model? Describe.

Part IV: Diagram the Energy Flow Through an Energy Pyramid 1. Complete the blanks on the diagram below using organisms from your ecosystem to demonstrate how energy transforms in an energy pyramid.

2. Fill in the blanks to complete these statements: In my

ecosystem, if the

contributes 1,000 calories, then the these

receives

calories, only

calorie is available from the original

as a third-level consumer.

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calories. Of calories are transferred to the

. Finally, only 1,000 for the

(producer)

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7L4AB Interactions, Matter, and Energy in Ecosystems

Student Journal Reflections and Conclusions 1.

What is the difference between a food chain and a food web?

What information does a food web show that is not demonstrated on an energy pyramid? What is demonstrated more clearly on an energy pyramid than on a food web?

What would happen to your chosen ecosystem if a disease killed off all of its decomposers?

Choose one organism to remove from your chosen ecosystem. How would that organism’s absence affect the other organisms in the ecosystem?

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STEMscopedia: Interactions, Matter, and

Energy in Ecosystems 7L4AB

Reflect Your muscles use energy to help you move, and your nervous system uses energy to help you understand the world around you. But how does your body obtain and use this energy? Animals, including humans, get their energy by eating other organisms. For example, you may have eaten an apple at breakfast that provided your body with energy later in the day. Where did the energy stored in the apple come from? We know that energy cannot be created or destroyed, so where does the source of energy in living systems begin, and how does it move through these systems? Energy flows through food chains and food webs. Maintaining life on Earth requires a continual input of energy from the Sun. Energy from the Sun travels through a number of different organisms in a food chain. Plants, algae, and some bacteria can convert light energy from the Sun into usable, chemical energy. This process is called photosynthesis. These types of organisms are called primary producers. Primary producers are also called autotrophs because they produce their own food. “Auto” refers to self, and “troph” refers to feeding, so autotrophs are self-feeders.

A food chain shows the path of food energy in an ecosystem. Consumers, also called heterotrophs, are organisms that obtain their energy by eating other organisms. Different types of heterotrophs are classified according to what they eat. Herbivores eat producers; the root “herb” refers to plants. Herbivores are primary consumers because they are the first consumer level in a food chain. Examples of common primary consumers include rabbits, squirrels, and cows. The next level of consumers, called secondary consumers, eats the primary consumers. Secondary consumers are also called carnivores because they eat other animals. The root “carn” refers to meat. Some common secondary consumers include wolves, eagles, and lions. A consumer that eats secondary consumers is a tertiary, or third-level consumer. Snakes and hawks are often the tertiary consumers in a food chain. Omnivores are a unique group of consumers because they eat both producers and other organisms. So omnivores can be classified as primary or secondary consumers, depending on what they choose to eat in a particular situation. Raccoons, brown bears, and many humans are omnivores.

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Organisms called decomposers fill the last link in a food chain. These organisms break down the remains and wastes of other organisms. Decomposers are important because they help return important nutrients to the environment. Certain bacteria and fungi act as decomposers. Ecosystems have both living and nonliving components. Energy from the Sun is only one abiotic (nonliving) factor of an ecosystem. All biotic factors (living things) must interact with the nonliving things in its environment. The abiotic components of an ecosystem are the air, water, soil, rocks, temperature, and solar energy. Each ecosystem is unique in the amount of each abiotic component it has. Deserts have less water than prairies, and tundras have lower temperatures than savannahs.

Look Out The consumer level of an animal can vary, depending on the path of energy in a particular food chain. For example, suppose a mouse eats grass and is the primary consumer. If a snake eats the mouse, the snake is a secondary consumer. On the other hand, suppose an insect eats grass and is the primary consumer. If a mouse eats the insect and the snake eats the mouse, the snake is a tertiary consumer. The important thing to remember is that food chains end with a top-level consumer that does not have any natural enemies. Alligators, hawks, and polar bears are examples of top-level consumers. In terrestrial ecosystems, food webs involve organisms that live on land. A food chain is useful for tracing energy flow, but it only tells part of the story. A food web shows the complexity of interactions between the different trophic levels. The food web shown below illustrates food relationships in a terrestrial ecosystem. Terrestrial refers to land, so a terrestrial ecosystem is located on land rather than in the water. The soil is a major abiotic component of a terrestrial ecosystem. It provides places where seeds can grow so that grass and trees may begin a food chain. Notice the direction the arrows are pointing. They are not showing who eats whom but the direction the energy flows. When looking at a diagram of a food web it is best to say the energy of this organism is passed or transferred to the next organism. You can see how several food chains overlap in this diagram. The primary producers are plants. Insects like grasshoppers and butterflies are primary consumers that eat the plants. Frogs and raccoons are secondary consumers that eat the insects, and snakes and eagles are tertiary consumers (also carnivores) that eat the secondary consumers. There are two things missing from this food web. Draw in the energy source near the producer and an example of a decomposer somewhere in the diagram. Be sure to draw the arrows that show the flow of energy in the right direction.

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Energy in Ecosystems

What Do You Think? Take a look at the terrestrial food web at right. Identify each organism as a producer (autotroph), primary consumer (heterotroph), secondary consumer (heterotroph), or tertiary consumer (heterotroph). Which organisms do you think do the job of eating dead plant and animal matter? Keep in mind that a single organism may fall into more than one heterotroph category. Be sure to draw in the energy source and an example of a decomposer.

Look Out What abiotic components are important to this ecosystem? Autotrophs are called primary producers, but they do not produce energy. Energy cannot be produced or destroyed; it is only converted from one form to another. Producers convert light energy into chemical energy. Other organisms can then use this chemical energy. In aquatic ecosystems, food webs involve organisms that live in water. Terrestrial ecosystems may be more familiar to us, but aquatic ecosystems make up the largest part of our biosphere. Aquatic ecosystems include marine and freshwater ecosystems. Marine ecosystems are saltwater environments like oceans, coral reefs, and salt marshes. Freshwater ecosystems are water environments with very low salt content and include rivers, streams, and ponds. Like all ecosystems, aquatic ecosystems consist of food webs with producers and consumers. Tiny aquatic plants called phytoplankton are the main producers in aquatic ecosystems. Algae are a common type of phytoplankton. Tiny aquatic animals called zooplankton and small animals without backbones called invertebrates are primary consumers that feed on phytoplankton. Fish and larger aquatic life eat these primary consumers and make up the higher consumer levels of the food chain. Water is a major abiotic component in this ecosystem. It provides areas for fish to swim and a large area for phytoplankton to grow near the surface. In the marine food web shown here, algae are the primary producers. Minnows, insect larvae, and snails are secondary consumers. Bass and sunfish are tertiary consumers. This food chain has a fourth consumer level, called a quaternary level. Snapper turtles eat the tertiary consumers, so they belong to this group. Bacteria and fungi also act as decomposers in aquatic ecosystems.

Algae are common producers in aquatic food webs.

What abiotic components would be important in this ecosystem?

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Looking to the Future: Protecting Food Webs What would happen to a food web if one group of organisms were removed? Every organism in a food web plays an important role. For example, in some terrestrial ecosystems, frogs are a food source for organisms like eagles and snakes. If frogs were not available, eagles and snakes would have less food and would decrease in number. Frogs are also regulators of the populations below them on the food chain. Frogs are secondary consumers. They eat insects, spiders, and small fish. If there were not enough secondary consumers to eat the primary consumers, the number of primary consumers would increase. If there were too many primary consumers, they could completely consume and destroy the plant populations. Removing one link in a food web has ripple effects. This is an important consideration because as humans take up more of Earth’s landscape, we often displace wild animals and plants. This can have dramatic effects on an ecosystem. As we consider conservation strategies, it is important to think about entire ecosystems. Efforts to save eagle habitats are not enough if we don’t consider the habitats of the eagle’s food sources. Changing an abiotic factor can have effects on an ecosystem, too. If there is too much rain, the area floods and many organisms can be killed. If there is not enough rain, there is a drought and many organisms will either leave the area or die. Food webs in ecosystems reveal predator/prey relationships and parasite/ host relationships. Different species in an ecosystem interact and form relationships within a food web. These relationships can be divided into three main categories: competition, predation, and symbiotic. Competition occurs when more than one group of organisms tries to use the same resource such as food, water, or living space. The organisms that get the needed resources will survive, while other organisms may not. Predation is a type of feeding relationship in which one animal hunts and eats another animal. The carnivores we’ve discussed so far, including lions, eagles, and turtles, are predators because they hunt for food. The animals eaten by the predators are the prey. In an aquatic food web, a shark is a predator and a seal is the prey.

The spider is a predator and the fly is the prey in this relationship.

Symbiosis describes a close, long-term relationship between two species. Mutualism is a type of symbiosis in which both species benefit. For example, certain bacteria live in the guts of animals. The bacteria have access to food and provide the animals with essential vitamins. Both the bacteria and the animals benefit from the relationship. Commensalism is a symbiotic A tick is a parasite that relationship in which one species benefits and the other is not obviously feeds on a human host. affected. Marine animals called barnacles live on gray whales. The barnacles obtain food while riding on the whales, but the whales seem to be

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Energy in Ecosystems

unaffected. Parasitism is a form of symbiosis in which an organism called a parasite feeds on another organism called a host. Parasites are generally much smaller than the host. In this relationship, the parasite benefits by receiving food and the host is usually weakened but not killed. An example of parasitism is a tick (parasite) feeding on the blood of a human (host). Study the images below. Identify the trophic levels shown in each image. Write producer, primary consumer, secondary consumer, or tertiary consumer next to the correct image in the right column of the table. Also identify any predator/prey relationships by writing predation across from the image in the right column.

What Do You Know? Food Relationships Close to Home To help your child learn more about relationships in food webs, go on a nature walk around your neighborhood or school. First, ask your child to list the different trophic levels found in food webs. Then have your child identify and record the trophic level(s) of each organism you observe on the walk. Image

Trophic Level Squirrel: Nut:

Bear: Fish:

Caterpillars: Leaf:

Bird: Insect:

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Connecting With Your Child Some common examples include trees and grasses (producers), insects and rabbits (primary consumers), smaller birds (secondary consumers), and snakes (tertiary consumers). You might also ask your child to look for decomposers by searching for mushrooms. Many insects that live under rocks and logs break down dead leaves and tree limbs, but these organisms are considered scavengers. Remind your child that the unaided eye cannot see decomposers like bacteria. If your child is not sure about the organisms’ trophic levels, suggest recording the names and drawing sketches or taking photographs of the organisms. During the trip, encourage your child to gather as much information about each trophic level as possible. After returning home, your child can conduct additional research on the trophic levels and feeding options for each organism as necessary. Once all of the information has been gathered and recorded, have your child draw a food web for the organisms you observed. If possible, take your child on a trip to a zoo or nature park and repeat the activity. Here are some questions to discuss with your child: 1. Which trophic level is the most common in your food web? Why do you think this is so? (Higher trophic levels are generally less common because of the energy required to maintain these organisms.) 2. What examples of predation did you observe? Is there any completion in your food web? Explain. 3. You were probably not able to directly observe parasitism. Why do you think this is so?

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7L4AB Interactions, Matter, and Energy in Ecosystems

Reading Science Name:

Date:

Group:

Food Webs 1

In 1958, the Chinese government started a policy called the Kill a Sparrow Campaign. They encouraged residents to kill all sparrows. The government thought sparrows were eating too many grain seeds. They thought killing sparrows would increase grain crop harvests. The campaign was successful. The number of sparrows was greatly lowered. At first it looked like the campaign had met its goal. That year’s grain harvest was larger than usual. However, the next year’s harvest was almost completely destroyed by a locust swarm. Thirty million Chinese people died during the Great Chinese Famine, which was partially caused by the Kill a Sparrow Campaign. How could one policy cause such widespread devastation?

The plan to reduce sparrows did not consider the place sparrows held in the human food web. Food chains are the path of energy from one organism to another in an ecosystem. Several interrelated food chains in an ecosystem form a food web. Humans don’t eat sparrows. Sparrows don’t eat humans. Therefore, sparrows are not a part of the human food chain. However, sparrows are a part of our food web. They prey on the pests that eat our food.

All food webs start with the energy produced by the sun. The sun causes photosynthesis in plants. Photosynthesis captures energy from the sun as carbohydrates. There are two sides to a food web: the grazing web and the decomposing web. In the grazing web, energy starts with the sun. It moves to plants in the form of photosynthesis. Energy moves into herbivores when they eat the plants. Finally, carnivores get the energy when they prey on the herbivores. In the decomposing web, energy starts in plants and animals that have died. Energy moves into decomposers like earthworms and fungi when they eat a decomposing organism. When carnivores like birds eat the decomposers, the energy is moved back into the grazing web.

The human and sparrow food chains are connected in two major ways. First, sparrows eat grain seed. Sometimes the birds eat the seeds that humans plant. They affect the human food chain by taking some grain. In that way, they decrease the amount of food available for humans to eat.

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Reading Science Continued 5

Second, sparrows may reduce the amount of grain seeds that grow; however, they also increase the amount of grain available for humans to eat by killing locusts. Locusts are insects that travel in large swarms. These swarms can contain billions of locusts. Locusts eat any green plant. When they travel in swarms, they can strip a crop within just a few hours. Sparrows eat locusts and other insects that eat crops. They are like a natural pesticide that protects human food sources. Sparrows eat far more insects than seeds. Overall, the sparrow’s presence increases the amount of grain available for humans to eat. Although they are not directly in the human food chain, they are an important part of the human food web.

Clearly, the plan to reduce sparrows did not consider the place sparrows held in the human food web. The organisms in food webs are connected and interdependent. We rely on the sparrow to help manage pests that threaten our crops, although we know they sometimes eat the seeds. They depend on us for seeds. We depend on them for pest control. Changes in one food chain can affect another food chain in ways that are unexpected and life altering.

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Reading Science 1.

Complete the following analogy: CARNIVORES : MEAT :: HERBIVORES :

CARNIVORES

LOCUSTS

PLANTS

HUNTERS

Ultimately, how should the Kill a Sparrow Campaign be evaluated? A

It was successful because that year’s harvest was plentiful.

It was successful because the sparrows did not eat the grain seeds.

It was unsuccessful because all the sparrows did not die.

It was unsuccessful because when the locusts came the next year, there were no sparrows around to eat them.

Which conclusion is true based on the information in this passage? A

Changing one organism in a food web would not have any effect on any other food web.

It is easy to see all the ways that food webs are connected.

Food chains are always separate from each other.

Food webs are connected to each other and sensitive to any changes.

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Reading Science 4.

Why is the decomposing web important? A

Decomposers help remove waste and use that energy to provide food for other animals.

It is a pathway for energy to move between organisms that is independent of the grazing web.

Decomposers take energy away from the grazing web, decreasing the food available to other animals.

Decomposers are animals like worms and fungi.

Why are sparrows important to the human food web? A

Humans eat sparrows and find them to be quite a delicacy.

Sparrows are biologically much like humans and eat the same foods as humans.

Sparrows eat insects and worms that destroy food crops that humans eat.

Sparrows eat other sparrows’ young.

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7L4AB Interactions, Matter, and Energy in Ecosystems

Math Connections Name:

Date:

Group:

The average lifespan of a gazelle changes based on the number of predators in the area and the percentage of necessary food and water supply available to the animal. Answer questions 1-4 using the chart below.

Predators (per 1 km2) 4 6 8 10

Average Lifespan of a Gazelle in the Wild (in years) Percent of Food and Water Supply Available 100% 80% 60% 17 15 13 16 14 12 15 13 11 14 12 10

40% 11 10 9 8

What is the relationship between the number of predators and the amount of food and water available to the gazelle?

Which combination of predators and available food and water will give the gazelle the longest lifespan?

Which combination of predators and available food and water will give the gazelle the shortest lifespan?

What possible combinations of predators and available food and water will allow the gazelle to live an average of 12 years?

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Math Connections Another example of organism relationships is between the lady beetle and trees. Lady beetles eat aphids, scale insects, thrips, meal bugs, and mites; all of which feed off plants. Use the line graph below to answer questions 5-7.

Effect of Lady Beetles on Trees

Is the relationship between the lady beetle and tree a positive or negative relationship? How does the data in the graph support your conclusion?

How many leaves would you predict a tree to have if there were 50 lady beetles per 100 square yards?

How would the introduction of a lady beetle predator affect the leaves of the tree?

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7L4AB Interactions, Matter, and Energy in Ecosystems

Math Connections Sometimes survival is not only dependent upon the number of prey in an area, but also the size of the area in which the predator hunts. The chart below shows different members of the same species and the areas in which they hunt. Use the chart to answer questions 8-11. Hunting Area and Available Prey Predator A Predator B Predator C

Predator D

Hunting Area (km2)

25.23

49.52

35.47

32.08

Survival Rate (Precentage)

50.46

99.04

71.14

64.16

What is the relationship between the area in which the predator hunts and its survival rate?

Write an equation that will determine the species’ survival rate, s, based on the size of the area, a, in which it hunts.

10. Using your equation from above, what would the survival rate be for a predator with a hunting area of 28.95 km²?

11. Does this chart take factors other than the hunting area into account when determining rate of survival?

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WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about examples of producer/consumer, predator/prey, and parasite/host relationships. WRITE Describe the producer/consumer, predator/prey, and parasite/host relationships as they occur in food webs within marine, freshwater, and terrestrial ecosystems. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar

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WRITING SCIENCE

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7th Grade Life Science

7L4C

Effects on Organisms and Ecosystems

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7L4C Effects on Organisms and Ecosystems

Student Handout

Name:

Date:

Why Do Birds Change Their Songs? Singing is one of the first things to come to mind when you think about birds. While a human cannot distinguish birdsongs as acutely as a bird can, the pitch of the song can be measured and studied. Ornithologists are biologists who specialize in studying birds, though many different kinds of scientists examine bird behavior because the feathered creatures are vital components of many different ecosystems. At Louisiana State University, behavioral ecologist Elizabeth Derryberry examined the songs of white-crowned sparrows. Dr. Derryberry found old records containing sparrow songs from 1970 and compared these songs to recordings from present-day sparrows. To accurately analyze the songs, she made new recordings in the same location as the old ones and used aerial photographs to analyze how the environment had changed over time. Dr. Derryberry found that the vegetation had grown thicker since 1970, and as a behavioral response, the sparrow’s songs had slowed down in tempo. Because young male sparrows learn to sing by listening to other adult males, these slower songs eventually became more and more common with each generation, until a slow mating song was the dominant one. Urban development has a very different effect, however. Peter Marra, a conservation scientist at the Smithsonian Conservation Biology Institute, has been studying a variety of city birds and how the urban environment impacts their songs. Cities are noisy places with constant traffic and buildings that absorb sound. Compared with their country-dwelling cousins, many city bird species have raised the pitch of their songs to a higher, or mid-frequency, tune. Birds of the same species will sing songs with lower pitches in undeveloped, natural land, but the noise of the city narrows the range of urban birds. Steve Nowicki, a biologist at Duke University, has studied the impact this change in pitch may have on mating habits for future generations of birds. Because songs are learned, if enough differences emerge over time in city birds, they may lose the ability to effectively communicate with their country-dwelling counterparts. During mating seasons, birds are sensitive to subtle changes in song. If country and city birds are singing in different languages, they may not be able to mate!

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Student Handout

How do birds respond to sudden changes in their environment?

Why do you think the changes in the birds’ songs are effective adaptations in the two situations discussed in the article?

How might urban factors like highways, buildings, and human waste affect other types of animals?

What are some long-term consequences for bird populations if these changes persist? How could this affect the rest of the ecosystem?

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7L4C Effects on Organisms and Ecosystems

Student Journal Name:

Date:

Group:

Ecological Summit Your role (circle one):

population ecologist

community ecologist

Your colleague’s name: 1. Define the two different types of data, and then list one example of each that you have in your set of evidence. Quantative: Qualitative: 2.

Using the ecological summit article and your evidence sheet, what are some key facts that may be important to solving this case? Fact

Importance

Based on your evidence, what predictions can you make about the cause of the Frog Fiasco?

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Student Journal Ecological Summit, continued Collaborate with your colleague to complete the rest of the Student Journal. 4. Discuss with your colleague the important facts that you have found. List and summarize the significant points that your colleague shares with you.

5. Based on the evidence you have analyzed with your colleague, brainstorm possible causes for the Frog Fiasco together. Use circles and lines to relate the evidence and possible causes to the problem and to relate pieces of evidence and possible causes to each other, as applicable.

The Crisis: Frog Fiasco

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Student Journal Ecological Summit, continued 6. EcoCity and its people need you to help them understand what caused so many frogs to become roadkill in areas usually uncommon for them. In a clear and concise essay of approximately four paragraphs, summarize your explanation by making a claim and backing it up with all of the scientific evidence and related reasoning that you and your colleague have used to draw this conclusion. Also, apply your prior knowledge of ecosystems, and be as creative and descriptive as possible.

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Student Journal Reflections and Conclusions 1.

How does your initial prediction compare with the conclusion drawn from the cooperative analysis done by you and your colleague? What evidence supports your conclusion?

Using the EcoCity Food Web on the Community Patterns page, what predictions can you make about other populations within the area? How have they likely been affected by an ecological event? Cite one or more specific types of organisms in your predictions.

What do you predict would happen if the factor causing this situation were reversed over the next year? In what ways would the populations and communities be affected by those conditions? Use specific examples to explain your prediction.

Use additional paper as necessary. Use all of the following terms to develop a graphic organizer. Terms: individual, population, community, food web, reproduction, habitat, abiotic patterns, diet, predators, male-to-female ratio, biosphere, carrying capacity, ecosystem, limiting factor, niche

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STEMscopedia: EFFECTS ON ORGANISMS AND

ECOSYSTEMS 7L4C

Reflect Have you ever wondered what affects individual organisms, populations, and ecosystems? Resource availability, disease, climate, and human activity affect them. Does it impact their survival? Can we change the effect on the ecosystem? Individual organisms, population, and ecosystems are interconnected. Individual organisms are one of a species (one lion), a population is a group of species (a pride of lions), and an ecosystem is all the living and nonliving things in an area. Ecosystems can be large or small. Living parts of the ecosystem include trees, plants, animals, and microorganisms. Nonliving parts of the ecosystem include rocks, landforms, weather, soil, climate, and water. Living and nonliving parts of the ecosystem interact to affect the survival and flourish of species. This coral reef is full of life and an example of living and nonliving parts working together to flourish. This coral reef is full of life and an example of living and nonliving parts This coral reef is full working together to flourish. of life and an example of living and nonliving Resource availability affects individual organisms, populations, and parts working together ecosystems. to flourish. Resources include food, water, air, shelter, and light. Light: Plants need light to help them make food through the process of photosynthesis. Some plants need more light than others. They will grow poorly if there is not enough light. Other plants grow well in the shade and may not do as well with too much light. Animals also need light to help balance their wake and sleep cycles. Light from the Sun allows animals to see during the day, which helps them search for their food source. Sunlight also provides energy in the form of heat to keep organisms warm. Water: Water is essential for life on Earth. All organisms need water to survive, but like light, the required amount varies among different organisms. For example, organisms in dry ecosystems do not need as much water as organisms in wet ecosystems. Think about cactus plants that grow in the desert. They have special structures to help them survive with little water. Kangaroo rats never need to drink water. Kangaroo rats have adaptations that allow them to survive in extremely dry environments. They can get the water they need from their food. Shelter: Organisms need shelter that will protect them from harsh weather conditions. Some organisms also need protection from other organisms. For example, mice often seek shelter by burrowing in the ground to stay warm and to hide from predators. Many birds build nests to provide shelter for their eggs.

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Ecosystems that are able to provide these basic needs thrive and organisms flourish. When the basic needs of organisms are not met, species will struggle for survival.

An ecosystem provides food, air, water, and shelter.

Diseases affect organisms. Viruses, fungi, parasites, and bacteria cause disease. Ecosystems with defense mechanisms to fight these are strong, flourishing environments. More diverse ecosystems are able to fight diseases due to the evolution and diversity of species. Invasive species are one of the biggest threats to an ecosystem. Disease attacks species as they weaken and the organisms are unable to combat the disease. Kudzu is an invasive species brought to America to help in erosion control. Kudzu competes with other species for resources.

Climates affect organisms. Climate change has a major effect on species and ecosystems. Global warming can cause animal species to migrate to warmer climates. Plant species migrate at a slower rate. Global warming will lead to the extinction of some species in many parts of the world. When climate changes, the cycle patterns also change, which causes nesting and breeding patterns to alter. The food web of ecosystems can also be disrupted or permanently changed when climate changes occur. Wetlands shrinking or drying up is known as a threshold effect. Threshold effects can cause stress or extinction of species or entire ecosystems. As global warming increases, Canada is predicted to be one of the most affected areas. Species won’t be able to migrate fast enough to survive the rapid climate change, which will cause a major change in the ecosystem and possible extinction of species.

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Global warming will cause lakes to dry up and reduce the freshwater supply.

Global warming will have harmful effects on the polar bear.

As the ice caps melt and the oceans warm, the ice algae decreases. This will alter the food web of the polar bear.

Human activity impacts ecosystems. Humans are harming species and ecosystems through pollution. Pollution includes agricultural waste, industrial waste, household waste, greenhouse gases, and deforestation. Lakes, rivers, and oceans get polluted through waste runoff from farmers and industry. Farmers use pesticides on their fields, which enters waterways. This runoff builds up and, over time, pollution depletes oxygen supply in waterway ecosystems through the bloom of excess algae. The algae takes over the waterways, and other life can’t survive. Greenhouse gases are the burning of fossil fuels and are a factor in global warming. Agricultural runoff into rivers Deforestation is the removal or clearing of and lakes cause algae to vast amounts of forest. Over 18 million acres bloom rapidly. of forest are destroyed a year. The amount of tropical rainforest has decreased by 50% and these forests are still being cleared. The tropical rainforest is home to hundreds of thousands of known species. Deforestation also adds to the greenhouse effect by removing trees, which produce oxygen.

Look Out Humans are not the only organisms that can change the environment. For example, beavers build dams by stacking branches and other materials into large piles. The dams block water flow and can cause flooding in surrounding areas. But dams can be helpful, too. They create ponds and provide a new place for fish and other water organisms to live. Sometimes, however, beavers can cut down so many trees that they destroy their own habitat! This beaver dam blocks water flow.

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What Do You Think? Not all human activities are bad for the environment. What are some ways that humans help their environment? What can humans do to reduce their impact on other organisms? What happens to organisms if their environment changes? Can you think of good and bad changes? Life on Earth is a delicate balance. When something in an environment changes, it has an effect on the organisms living in that environment. Take a look at the graph. It shows the change in the rainforest in the last 75 years. Carefully analyze how the decrease in the size of the rainforest has changed. Does this graph alarm you? How do you think the ecosystem is changing? Explain your reasoning.

Tropical rainforest acres.

What Do You Know? How can humans influence populations for the good? What happens when the deer population keeps increasing? Deer eat saplings and underbrush. This leaves smaller animals without shelter and food when deer overgraze. The bird population is also affected when the deer population increases and the trees and small animal populations decrease. Farmers kill mountain lions, which eat deer, and the mountain lion populations have decreased. Increases in the deer population also lead to increases in the tick population. Ticks carry diseases that can affect humans. How can the deer population be controlled?

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STEMscopedia: EFFECTS ON ORGANISMS AND

ECOSYSTEMS

Try Now Use the data below to answer the following questions. 2000 2004

2007

2012

2015

Deer Saplings Mountin Lions Cardinals

500 50 5 20

625 30 5 5

500 50 10 10

200 200 20 40

325 100 10 30

1. Analyze what the data represents. Explain your answer.

2. Why has the deer population increased? _____________________________________________ 3. Why has the bird population decreased? _____________________________________________ 4. Why is the deer population decreasing in 2015? _______________________________________ 5. What factors might humans introduce to decrease the deer population? ____________________ ________________________________________________________________________________

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Connecting With Your Child Growing a Garden For this investigation, you will need the following materials: • • • • • • • •

Seasonal growth chart Several types of seeds (flowers or plants) Yard or plant pots (2) Top soil Fertilizer Plant markers Water access Journal

Start When selecting seeds look at your seasonal growth chart and select plants that will grow in your climate. Also, select plants that won’t grow in your climate. Select an area of your yard for planting plots. Prepare the soil for planting. When the soil is ready, add topsoil to half. Leave the other half as is. Plant seeds of both types (ones that grow and ones that don’t grow) in the soil. Add markers to the seeds with the names on them. Add fertilizer to the side with topsoil only. Water both sides. Watch the seeds over the next few days and chart the growth in your journal. If there isn’t rain, water the side with topsoil and fertilizer, but not the other side. Don’t use pesticides to kill bugs. Chart the growth in your journal over the next few weeks. Here are some questions to discuss with your child. 1. Why did some plants do better than others? 2. How did the topsoil and fertilizer affect the growth? 3. What happens when droughts happen? 4. Did you lose any plants to nature (bugs, weather)? 5. Analyze the data you collected and interpret what it means.

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Reading Science Name:

Date:

Group:

Kelp Forests and Ecosystem Balance 1

Along the coastlines of the northern Pacific Ocean, there exists a unique and interesting ecosystem, the giant kelp forests. The kelp in these ocean forests can rise up to 80 meters from the ocean floor. They provide a multilayered habitat for a variety of sea organisms. Two organisms play a fundamental role in the health of this ecosystem: the sea otter and the sea urchin. The sea otters are vital to the balance within this ecosystem. Their presence largely determines whether the coastline will support a kelp forest or become overgrazed by sea urchins.

How is this dynamic equilibrium maintained? The sea otters eat a variety of shellfish, but sea urchins are a large portion of their diet. In turn, the sea urchins are herbivores that feed on ocean plants, especially the giant kelp. The sea otters’ feeding habits limit the population of sea urchins. This allows the kelp to grow and reproduce. The combination of sea otters, sea urchins, and kelp form an interaction called a trophic cascade within this dynamic ecosystem. The presence of the sea otters maintains the balance of the kelp forest ecosystem.

So what could occur if external factors interfered with this system? Apex consumers are organisms at the top of the food chain. Apex consumers, such as the sea otter, play a critical role in the health of an ecosystem. Sometimes an external factor alters the apex consumer population. This can affect not only the individual organisms of that species but also entire populations and communities in the ecosystem. When the size of apex consumer populations decreases, the health of the entire ecosystem can become compromised.

In the 1990s, scientists noticed that the sea otter populations were suddenly declining in the northern Pacific coastal ecosystems. They proposed that there might be some type of external factor affecting the sea otter population. At the time, they did not understand why this was occurring. As a result of this decline, the kelp forests were starting to disappear. As the otter populations were removed from the system, the sea urchin populations grew without the controls provided by the otters’ feeding habits. As a result, the sea urchin population exploded. They began to eat the holdfasts that attached the kelp to the ocean floor.

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Reading Science 5

In many places, the kelp forests became so overgrazed by sea urchins that they turned into areas called urchin barrens. This caused problems since kelp forests have a positive effect on the coastline. The giant kelp beds reduced both wave height and intensity near the shore. This created safe and diverse habitats for many different ocean creatures. The disappearance of the kelp forests affected the populations of many other organisms. In fact, the entire kelp forest community was altered as a result of the decline in sea otters.

So why were the otters disappearing? After several studies, scientists found that orcas (killer whales) had shifted their diets. They were now eating sea otters at a level that had not been seen before the 1990s. Orcas traditionally feed on sea lions and harbor seals, and sometimes on larger whales. However, in the years after 1990, expanding commercial fishing practices shifted the food sources of the sea lions and harbor seals.

Other scientists offered a different explanation for the change in the orca’s feeding habits. It may have been due to shifts in the temperatures of the oceans as a result of climate change. Shifting ocean currents may have changed the patterns of fish and other prey for the sea lions and harbor seals. Sea lions and harbor seals may have had to move to new hunting grounds, making it difficult for the orcas to find them; Or, perhaps the numbers of the orcas’ traditional prey declined enough to force the orcas to look for another food source. Whatever the reason, factors that were external to the kelp forest ecosystem at first affected the individual otters within that ecosystem. The consequences, however, had a severe effect on all of the populations of organisms within the entire kelp forest community.

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7L4C Effects on Organisms and Ecosystems

Reading Science 1.

Based on the passage, what might have caused orcas to eat fewer sea lions and harbor seals? A.

The orcas were eating too many fish, so the sea lions and harbor seals left.

The fish that the sea lions and harbor seals eat were being commercially overfished.

Sea otters were eating the sea lions’ and harbor seals’ food.

The sea lions and harbor seals began eating the kelp forests.

What would be an example of a food chain in the giant kelp forest ecosystem? A.

The orcas were eating too many fish, so the sea lions and harbor seals left.

The orcas eat the sea otters, which eat sea lions and harbor seals.

The sea otters are eaten by the orcas, which also eat sea lions and sea urchins.

The giant kelp is eaten by the sea urchins, which are eaten by the sea otters.

What is the immediate cause of the decline in the sea otter population? A.

The feeding habits of the orcas

The feeding habits of the sea urchins

The feeding habits of the other organisms within the kelp forest

The feeding habits of harbor seals and sea lions

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Reading Science 4.

What would be a negative consequence of the kelp forest ecosystem falling out of balance? A.

Increased wave height and intensity

A loss of diversity within the ecosystem

An increase in the sea urchin population

All of the above

The combination of sea otters, sea urchins, and kelp form ________. A.

a northern Pacific coastline

a trophic cascade

an apex consumer

good fishing grounds for commercial fishermen

What is an urchin barren? A.

A giant kelp forest that has been overgrazed by sea urchins

A situation in which the sea otters have eaten all of the urchins

An external factor that has affected the sea urchins

None of the above

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7L4C Effects on Organisms and Ecosystems

Math Connections Name:

Date:

Group:

Ecosystem Responses As the world’s population increases, access to freshwater decreases. This relationship holds true for both industrialized and developing countries of any climate. Complete the activities below to further investigate the relationship between population growth and water availability. 1.

Using the table below, create a line graph that compares the change in world population and average water availability per capita during the years 1950 to 2050. Remember to provide a title for your graph, a legend, and label your x-axis and y-axis. Year

World Population (Billions)

1950 1975 1995 2025 2050

2.5 4.0 5.9 8.2 9.1

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Average Water Availability Per Capita (m3 per capita) 15,500 12,000 7,500 5,000 4,300

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Math Connections 2.

The quantity of water available to a population can also be described in three qualitative terms—sufficiency, stress, and scarcity.

•

Relative sufficiency indicates that there is more than 1,700 m3 of freshwater available per capita. Stress indicates that there is 1,000 to 1,700 m3 of freshwater available per capita. Scarcity indicates that there is less than 1,000 m3 of freshwater available per capita.

• •

Using the world population values from the table on page 1, complete the table below. Use scientific notation when reporting Population Living Under Water Stress and Population Living Under Water Scarcity.

Year

World Population in Billions

1950 1995 2025 2050 1.

Percentage Living Under Water Sufficiency

97% 92% 58%

Population Living Under Water Sufficiency (billions)

Percentage Living Under Water Stress

Population Living Under Water Stress

Percentage Living Under Water Scarcity

Population Living Under Water Scarcity

0% 5% 26% 24%

10%

Create a pie chart that depicts the conditions of relative water sufficiency, stress, and scarcity in the year 2050.

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Math Connections 4.

What is the rate of change in the world population predicted from 1950 and 2050?

What is the rate of change in the average water availability per capita predicted from 1950 and 2050?

Describe the relationship between the world population and per capita water availability based on your tables and graphs?

What do you think contributes to this relationship?

Based on the data, in what ways might the world be different in 2050 than it is today? What would need to change to reverse the situation?

Droughts not only affect human populations, but also ecosystem populations. Experts believe that decreased water availability in California is responsible for a 15% decline in waterfowl populations between 2012 and 2013. If waterfowl populations were 450,000 in 2012 and the rate of population change stayed the same, estimate California’s waterfowl population in 2015.

10. How does the relationship between waterfowl population and water availability differ from the relationship between human population and water availability? Explain. © Accelerate Learning Inc. - All Rights Reserved

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7L4C Effects on Organisms and Ecosystems

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about how resource availability, disease, climate, and human activity affect individual organisms, populations, communities, and ecosystems. Observe the trends on the graphs below. WRITE Choose one of the graphs to analyze. Using the information in the graph, explain how resource availability, disease, climate, and human activity could have affected the organisms, populations, and ecosystems.

Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar © Accelerate Learning Inc. - All Rights Reserved

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WRITING SCIENCE

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7th Grade Life Science

7L4D

Terrestrial Biomes and Aquatic Ecosystems

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7L4D Terrestrial Biomes and Aquatic Ecosystems

Student Journal Name:

Date:

Group:

Background 1.

What is a habitat?

What is a microhabitat?

What is biodiversity?

What is sustainability?

What is succession?

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7L4D Terrestrial Biomes and Aquatic Ecosystems

Student Journal Part I: Biomes Biome Notes

General climate factors

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Freshwater Biomes Abiotic features of the biome (soil type, geology or landforms, water resources)

Biodiversity of the biome (organisms commonly found there)

Marine Biomes Abiotic features of the biome (soil type, geology or landforms, water resources)

Biodiversity of the biome (organisms commonly found there)

Forest Biomes Abiotic features of the biome (soil type, geology or landforms, water resources)

Biodiversity of the biome (organisms commonly found there)

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7L4D Terrestrial Biomes and Aquatic Ecosystems

Student Journal Part I: Biomes, continued Biome Notes

General climate factors

Grassland Biomes Abiotic features of the biome (soil type, geology or landforms, water resources)

Biodiversity of the biome (organisms commonly found there)

Desert Biomes Abiotic features of the biome (soil type, geology or landforms, water resources)

Biodiversity of the biome (organisms commonly found there)

Tundra Biomes Abiotic features of the biome (soil type, geology or landforms, water resources)

Biodiversity of the biome (organisms commonly found there)

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Student Journal Part II: Biodiversity Round 1 1.

How many trees were left standing?

Why were so many trees wiped out?

How did the lack of biodiversity in this ecosystem contribute to its sustainability?

Round 2 4.

How many trees were left standing?

Why were so many trees left standing?

How did the biodiversity of this ecosystem contribute to its sustainability?

Why is biodiversity important?

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7L4D Terrestrial Biomes and Aquatic Ecosystems

Student Journal Reflections and Conclusions 1.

What are the abiotic factors that typically define a biome?

What is the difference between a biome and a microhabitat?

How does biodiversity contribute to the sustainability of a habitat?

What natural disturbances might disrupt a habitat?

What human activities might disrupt a habitat?

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Reflect

7L4D

How would you describe the environment where you live? Are there lots of trees? Is it sandy and dry? Do you live near water? Answering these questions can Climate: the general weather help you decide in which biome you live. A biome is a large area patterns of an area over a that has similar plants, animals, and climate. period of time Our earth is divided into several biomes, and each of these biomes falls into one of two categories: land or aquatic. Land biomes are large land mass areas, such as the tropical rain forest (jungle), savannah (grasslands), taiga, tundra, mountain, and temperate forests. Aquatic biomes are listed as freshwater, estuarine, and marine. Go into your yard and look around — how far can you see? A biome is far larger than you can see — it may cover thousands of square miles! How are land biomes categorized? Land biomes are categorized by the plants and animals there, but also by the temperature and amount of precipitation. Some biomes, such as the tundra and taiga, stay very cold. Other biomes, such as the tropical rain forest and temperate forests, may be warmer. Tropical Rain Forest Tropical rain forests are found in areas along Earth’s equator. They have thick vegetation, poor soil, heavy precipitation (many get more than 100 inches of rain per year), and stay warm year-round. Tropical rain forests are important because they have the greatest biodiversity of all the land biomes. Scientists discover new species of plants and animals in rain forests Almost every day. According to WWF — World Wide Fund For Nature, between 1999 and 2009 at least 1,200 new species of plants and vertebrates have been discovered in the Amazon biome. The new species include 637 plants, 257 fish, 216 amphibians, 55 reptiles, Biodiversity: the variety of 16 birds and 39 mammals. Tropical rain forests have broadliving things in an area leafed plants, vines, many types of insects, and small mammals.

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Savannah Savannahs are known by several names throughout the world. In parts of Europe, they are called steppes. In the United States, we call them prairies. These areas are usually flat lands that are covered with grasses. They serve as grazing lands for many large mammals, such as buffalo, antelope, sheep, and cows. Savannahs have very few trees — you can see for long distances here. They have cold winters and warm summers. Savannahs have animals that burrow, birds, insects, and large mammals.

Burrow: to dig a home underground

Taiga Also known as the boreal forest, this is an area that is covered with cone-bearing trees such as spruce and pine. “Taiga” is a Russian word that means “forest.” This biome has very cold, snowy winters and warm, humid summers. These biomes stretch over northern Europe and North America. The plants that live here have thick waxy coatings over the leaves so that they do not lose much water. The taiga is an area where many insects and birds migrate in the summer. Some animals that live here are snowshoe hares, moose, wolverines, and bobcats. Tundra The tundra is a very cold, flat biome. Found at the most northern land areas of the Earth, the tundra has few plants and animals living there. The soil is permanently frozen, and is known as permafrost. Although the ground may be covered with ice, the tundra gets very little precipitation. During warmer periods, the ice may melt, forming ponds and marshes that migrating birds and insects may visit. Most of the plants that live here are small, such as mosses, lichens, and shrubs. Small mammals, such as mice and shrews, birds, mosquitoes, and larger mammals, such as reindeer, live in the tundra.

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Migrate: to move from one region to another, especially according to seasons

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Mountain The mountain biome has a wide range of biodiversity based on location and elevation. It is also known by the name “alpine.” Its cold and windy weather enables few large plants are to survive here. Poor, rocky soil also makes it difficult for plants to grow, and the high winds can easily knock down large trees. The air is thin, and the carbon dioxide (CO2) that plants need for photosynthesis is in limited supply. Cold-blooded animals do not live here, because it is too cold for them to survive. Warm-blooded animals who live here have specialized blood that helps them get maximum oxygen (O2) from the air. Llamas, mountain goats, and foxes live in mountain biomes. Temperate Forests This biome is also known as the deciduous forest because the trees lose their leaves in the winter. Temperate forests are found in the eastern United States, western Europe, and eastern Asia. Rich soil, significant rainfall (around 50 inches per year), and distinct seasons make this a biome that supports a wide variety of plants and animals. In the winter, many animals, such as squirrels and bears, hibernate because food sources may be limited. Trees such as oak, sweet gum, hickory, and maple provide both food and shelter for many animals. Each spring, these Hibernate: to spend the winter trees will bud new leaves. Animals in a semi-sleep condition found here may include owls, deer, snakes, and frogs.

What are characteristics of the aquatic biomes? Freshwater Freshwater includes ponds and lakes, which are still water, and rivers and streams, which are moving water. Some ponds and lakes may be seasonal, the result of snow melting at higher elevations. Freshwater biomes represent only 1% of water found on earth!! Many types of water grasses, algae, and lilies make their homes in fresh water. Plants that are found in moving water must have a way to attach so that they do not float downstream. Fish, amphibians, reptiles, and birds also live in freshwater biomes. Wetlands are land areas that are covered by water. Many ponds and lakes provide freshwater wetland homes to a wide variety of animals, many of whom migrate.

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Estuarine The term estuarine refers to where fresh water and salt water mix. This usually happens in a region where a river or stream empties into the ocean. Whether it is a small stream that dumps into a bay or the Mississippi River emptying into the Gulf of Mexico, the mixed water is too salty to be called fresh and too fresh to be called salty. Estuarine water is about half the salinity of ocean water (about 18 parts per million). Estuaries serve as nursery grounds for many ocean animals such as crabs, shrimp, shellfish, and fish. Seaweed, marsh Salinity: the amount of salt grasses, and plants that grow along the water’s edge help to in water protect the young animals as they grow as well as provide food for many other animals. Many estuaries include wetland marsh areas that are home to a wide variety of animals, many of whom migrate. Marine The marine biome is the largest biome in the world. Approximately 75% of the Earth’s surface is covered by oceans. Plants and animals that live here have developed adaptations that help them survive in saltwater. The marine biome is divided into two regions: shallow waters and deep ocean. Shallow waters are home to coral reefs. Coral reefs have the greatest biodiversity of any biome on earth. Corals, crabs, octopus, and a wide variety of fish call coral reef areas home. Deep oceans have far fewer species of plants and animals than shallow waters, but they are home to larger animals such as sea turtles, whales, sharks, and squid. Oceans also contain algae — tiny plants that produce oxygen during photosynthesis. Up to 80% of the oxygen you breathe was made in the ocean by some of the smallest plants on Earth! How do environmental changes affect a biome? Several thousand years ago, an ice age period began on Earth. Large areas of Europe, Asia, and North America were covered by thick sheets of ice. Plants and animals that lived in this area either had to migrate to warmer areas or risk dying because of no food, losing their homes, or freezing to death. Entire biomes went into deep-freeze, and many species of plants and animals were wiped out during this time.

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Some species were able to adapt to the changing conditions. Woolly mammoths grew longer hair and thicker layers of fat to survive the freezing temperatures. Scientists have been able to study mammoths that were discovered — they had been frozen for thousands of years! During the Ice Age, much of the water on earth was in the form of ice. Sea levels were much lower, and this affected the plants and animals that lived in the ocean. Since water levels were lower, land was exposed in shallower areas. This gave land animals more area to migrate. As the ice began to melt, sea levels rose. At one point, much of the southeastern United States was underwater. Fossilized sea shells have been found in northern Mississippi, Alabama, and Georgia, and they have even been found on the slopes of the Great Smoky Mountains! When sea levels rise, they make less surface land available for land plants and animals to live on. When sea levels drop, there is more surface land available. On a smaller scale, natural disasters can hurt biomes. Hurricanes cause great devastation to estuaries and the species that live there. During hurricanes Katrina, Rita, and Ike, oyster beds in the northern Gulf of Mexico were heavily damaged by sand and debris stirred up by large waves. Several years later, the populations of Gulf oysters still have not returned to pre-hurricane numbers. High winds from these hurricanes knocked down thousands of trees and destroyed habitats for both plants and animals. Wildfires and droughts are also natural disasters that can have severe impacts on biomes. A wildfire may destroy thousands of acres of forest or grassland, burning up plants and forcing animals to migrate or die. A wildfire can be beneficial, however, as it adds nutrients to the soil. These nutrients enrich the soil and feed new plants that grow there. Habitat: the place where an organism naturally lives

A drought can change lush green areas to cracked, dry ground in as little as a month. Droughts kill thousands of plants because they need water to grow. Animals must migrate to find water or die from dehydration.

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Look Out Humans also cause large environmental changes to biomes. Cleacutting tropical rain forest areas can turn a forest into an area that resembles a savannah. Entire species of plants and animals can be wiped out because their habitats have been destroyed. More than 150 acres of rain forest land are destroyed each minute. Humans clear the forest areas to provide lumber, space for homes and businesses, and grazing areas for cattle. We need to remember that if we destroy habitats for our own interests, we may potentially cause plants and animals to become extinct.

What Do You Think?

Look at the pictures above. The picture on the left shows a tropical rain forest. Thousands of species of plants and animals live here. The picture on the right shows a taiga forest area that has been clear cut, killing trees and forcing animals from their habitats. The soil is now exposed, making it much easier for this land to weather and erode.

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Try Now Take some time to explore how humans can affect biodiversity in an area. 1. Measure a 1 meter square area outside. 2. Make a sketch of your area. Note how many different plants, animals, and fungi you are able to see. 3. Using a shovel or a rake, completely clear that area — remove all the plant material. 4. After a day or two, make another sketch of your area — see how many plants, animals, and fungi you are able to see. 5. Record your observations for a week. 6. Where did the animals go? How did removing the plants affect the animals?

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Career Corner: Conservation Biologist Conservation biologists are people who study Earth’s biodiversity and try to protect habitats and the species who live there. Many in this field pick specific areas to study and protect, such as rain forests, wetlands, or coral reefs. Many conservation biologists work with the Environmental Protection Agency, a U.S. government agency that serves to protect the environment. Scientists study species populations and the effects of pollution. They also alert the public to species that are Endangered: at risk of becoming threatened or endangered. By studying how humans disappearing completely affect the environment, plant species, and animal numbers, conservation biologists can predict possible extinctions. If you like keeping nature safe and protecting plants and animals from harm, conservation biology might be a great field for you!

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Connecting With Your Child Sit down with your child and select several different countries. Using encyclopedias, books, and the Internet, find pictures of each of these countries. Identify which biomes you can see in each country. Do some countries have more than one biome represented? If you have one, spin a globe and stop it with your left hand. Look at what is underneath your left thumb. See if you can predict which biome can be found on the Earth where your left thumb landed. Here are some questions to discuss with your child: 1. How big is a biome? 2.

Can some biomes be bigger than others?

Are the same types of plants and animals always found in a biome?

Is there an event that could cause a biome to disappear completely?

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7L4D Terrestrial Biomes and Aquatic Ecosystems

Reading Science Name:

Date:

Group:

The Desert Ecosystem 1

The sun is rising on a spring day in the Mojave Desert. During the day, the temperature will rise to over 40°C (102°F). During the year, only 33 cm (13 in.) of rain will fall. It is hard to imagine any life flourishing in this extreme environment, but many plants and animals find a way to thrive. The desert ecosystem supports a variety of organisms. The foundation of all biotic life in the desert is the creosote bush, which is the most common producer in the Mojave. It gets its energy from photosynthesis and provides food to many consumers in the desert, including beetles, mice, and rats. In turn, the mice and rats are eaten by snakes, and the snakes are eaten by hawks.

Producers are those organisms that use sunlight, water, and carbon dioxide to make their own food, while consumers are those organisms that need to eat other organisms for food. In the desert, the creosote bush, the Mojave yucca, the beavertail cactus, and other plants are the producers that keep consumers fed. They rely on abiotic factors to survive. Without these nonliving factors, like sunshine, water sources, land, rocks, soil, and air, producers cannot produce.

The kangaroo rat is a small mammal that lives in the Mojave Desert. These furry animals and their coyote predators are xerocoles — animals adapted to live in the desert. Coyotes consider kangaroo rats to be tiny, tasty snacks. Coyotes are an important organism in the desert because they keep the rodent population under control. In terms of organization, an individual coyote organism is part of a population, meaning all of the coyotes in the Mojave Desert. A community is formed when a population of coyotes exists with populations of other organisms that live in the same place at the same time. Since the coyote is so widespread within the desert, most desert life is a part of its community. The kangaroo rat, the creosote bush, and the red-tailed hawk are all members of the coyote’s community. The ecosystem includes all of the living and nonliving things that interact with each other in an environment.

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Reading Science Continued 4

The most salient factors in the desert ecosystem are abiotic — the sun and water. All living organisms in the desert have adapted to the sun’s relentless glare and intense heat. The sun has also shaped the terrain by ensuring that the only producers who can survive must do so by being spread out far enough that they do not have to compete for water. To prevent overcrowding, a fully mature creosote bush will not leave enough water in the nearby soil for a seed to germinate. Only seeds that land far away from mature plants can get enough water to grow. Each desert organism has to find ways to get enough water and relies on others for getting the things it needs to survive.

Although the desert ecosystem is very large, there are smaller habitats within the desert, such as the creosote bush, which supports an ecosystem all its own. Its leaves provide a microhabitat of shelter and food for beetles, millipedes, and grasshoppers, which are then eaten by mice and rats. The rodents like to make their burrows in the loose soil underneath the bushes’ leaves because they help to hide the entrances. In the creosote bush ecosystem, arthropods, rodents, and the shrub interact within the environment of the creosote bush. These organisms cannot exist in the same manner outside of that habitat. They rely on the ecosystem within the creosote bush to provide for their needs.

Studying the desert’s foliage and animals gives us insight into this unique ecosystem. In the desert, each plant and animal exists in a delicate balance to conserve water and survive despite the raging sun. Together, they form the diversity and beautiful colors of the desert.

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7L4D Terrestrial Biomes and Aquatic Ecosystems

Reading Science 1.

Which of these is an example of an abiotic factor? A

Creosote plant

Rocky desert soil

Kangaroo rat

Coyote

Based on the context of paragraph 4, what are salient factors? A

Important factors

Ignorable factors

Interesting factors

Intended factors

Which of these is an example of a biotic factor? A

Hot desert sun

Mojave River

Acrid desert air

Mojave grasshoppers

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7L4D Terrestrial Biomes and Aquatic Ecosystems

Reading Science 4.

Which words in the story help the reader understand the meaning of the word flourishing in paragraph 1? A

Many plants

The desert ecosystem

Find a way to thrive

Extreme environment

Which level of organization do all of the Mojave grasshoppers in a creosote bush microhabitat form? A

Organism

Population

Ecosystem

Community

What would be the most likely result of the death of all creosote bushes in the Mojave Desert? A

More coyotes

More red-tailed hawks

An overflow of Mojave grasshoppers

The eventual death of many organisms in its ecosystem

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7L4D Terrestrial Biomes and Aquatic Ecosystems

Math Connections Name:

Date:

Group:

Floods: Short-term Impact When floods occur, habitats are affected in ways that upset the balance of flora and fauna in an area. In 2011, Hurricane Irene devastated the East Coast: North Carolina, Virginia, New Jersey, New York, Vermont, and New Hampshire were in its path. The flooding from Irene greatly affected the trout population in several Vermont watersheds. Below is a chart displaying the data collected before and after Irene hit Vermont. Wild Trout Populations in Vermont Watershed

Pre-Irene Post-Irene (trout per mile) (trout per mile)

Slide brook

1,100

425

Union brook

450

275

Stony brook

750

250

Dog river

900

425

Create a double bar graph comparing the trout populations before and after Irene hit Vermont. Include a key.

1. What was the mean number of trout prior to Hurricane Irene?

2. What was the mean number of trout after Hurricane Irene?

3. What was the percent decrease in the mean number of trout in the four watersheds?

4. What percentage of the trout in all four watersheds were from stony brook prior to the storm?

5. What percentage of the trout in all four watersheds came from stony brook after the storm?

6. Which watershed experienced the largest percent decrease among the four watersheds?

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7L4D Terrestrial Biomes and Aquatic Ecosystems

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about Earth’s biomes. WRITE Describe the characteristics of each of Earth’s major biomes, and explain how changes in environmental conditions can affect the survival of individuals and entire species of organisms. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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7L4D Terrestrial Biomes and Aquatic Ecosystems

WRITING SCIENCE

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7th Grade Life Science

7L5AB

Natural Selection, Survival, and Reproduction

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7L5AB Natural Selection, Survival, and Reproduction

Student Journal Name:

Date:

Group:

Background 1.

What is a trait, and why is it important?

What is an adaptation?

Why do animals migrate?

What physiological changes can occur during hibernation?

What are some examples of internal structures that allow organisms to survive in their environment?

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7L5AB Natural Selection, Survival, and Reproduction

Student Journal Part I: Implement Your Investigation Collect, Record, and Organize Data Record the data from the observation cards in the data table below. 10-Year Study Data Population A (# of birds)

Year

Population B (# of birds)

Small Seed Yield

Large Seed Yield

Weather

1 2 3 4 5 6 7 8 9 10 Input your data into a spreadsheet program and make a graph of your data, or use the graph provided below.

Label for y-axis______________

Bird Population Changes

Population Legend: Small beak Large beak Label for x-axis ________________

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7L5AB Natural Selection, Survival, and Reproduction

Student Journal Part I: Implement Your Investigation, continued 1.

In what ways might a 10-year drought affect the subpopulations of this bird species? Explain your answer.

What other variables not addressed in this specific investigation could have additional influence on subpopulation survival and success? Explain your answer.

In what ways is the survival and success of these natural populations different from selectively bred domesticated populations? Explain your answer.

How do traits and adaptations assist in the survival of a species? Include examples in your answer.

What traits allowed the two bird populations to survive in the same habitat?

Did the changes in weather affect each population the same way? Why or why not?

Why do you think bird population B adapted to have a stronger beak?

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7L5AB Natural Selection, Survival, and Reproduction

Student Journal Part II: Graphing Data 1.

In the space below, graph the data from your Student Guide.

What correlation do you see between plant height and average precipitation?

Why would plant height start to decrease even though the precipitation is still increasing?

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7L5AB Natural Selection, Survival, and Reproduction

Student Journal Reflections and Conclusions 1.

Is the hypothesis supported by the data? Explain.

How did the results reveal a relationship between the independent and dependent variable?

Where could errors have been made while collecting or organizing data?

What can you conclude about this investigation?

What would you do differently if you were to conduct this experiment again?

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STEMscopedia: NATURAL SELECTION, SURVIVAL AND REPRODUCTION 7L5AB

Reflect What is the first thing you think of when you think of a giraffe? Giraffes are unique animals because they have such long necks. Fossil evidence indicates that the neck of a modern-day giraffe is much longer than the neck of an ancient giraffe or its ancestors. How and why did the giraffe change in such a manner? What are the advantages of having a long neck? Can you think of any other organisms with physical adaptations that help them survive in their environment? Adaptations, Natural Selection, and Species Survival Structures of living organisms demonstrate adaptations that allow for specific functions. For example, a giraffe’s long neck is an adaptation because it allows the giraffe to reach leaves located on high tree branches. This provides giraffes an advantage because they can reach food that other animals cannot. Adaptations are structures or behaviors in organisms that help them survive in their environment. Since a longer neck provides an advantage, giraffes with this trait are more likely to survive, reproduce, and pass the trait on to their offspring than are giraffes with shorter necks. This is called natural selection, which is the process that occurs over generations by which favorable traits become more common in a species or population and unfavorable traits become less common.

Look Out Many people mistakenly believe that species change to meet the conditions of their environments, but this is untrue. Animals with traits more favorable for the habitats in which they live will be more likely to survive and reproduce. When they reproduce, they pass on their traits to the next generation. The process repeats over many generations until animals with favorable traits are more widespread. For example, there is scientific evidence from geneticists to document the claim that polar bears split from grizzly bears several million years ago. The bears underwent many adaptations and have become a new species. One adaptation was acquiring white fur. However, grizzly bears did not consciously decide to become white to better camouflage in the Arctic snow. Instead, grizzly bears that happened to be born with lighter fur were able to camouflage better, thereby being more successful hunters and obtaining a more life-sustaining food supply. These bears were then more likely to thrive in the harsh climate, reproduce, and pass on their traits to their offspring. Therefore, lighter fur was a favorable trait and was passed down from generation to generation until polar bears became whitish in color. This is an example of natural selection.

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STEMscopedia: NATURAL SELECTION, SURVIVAL AND REPRODUCTION Examples of Natural Selection One challenge for animals that live in water is acquiring enough oxygen. Animals that live on land use lungs to obtain oxygen from the air. Fish have gills to help them take in enough oxygen from the water. Fish gills are internal. Amphibians also have gills during the time they live in the water. These gills can be found externally on amphibians, as is evidenced in this photograph of a salamander. The gills look like feathery structures on each side of the salamander’s body. The gills are adapted to have many fringes to increase their surface area so the gills can absorb more oxygen from the water. Animals are not the only organisms to experience natural selection. Plants also have adaptations that help them survive. Water lilies, for example, possess large, thin leaves. The structure of these leaves helps water lilies float, so they can obtain sunlight to perform photosynthesis. The ability to float is an advantage because plants that have this leaf structure can produce more food during photosynthesis. The extra food helps plants make more seeds to pass on this trait to more offspring in the next generation. Tulips also have a special adaptation. They store their food in parts called bulbs, which grow underground. During winter or other harsh conditions like a drought, the aboveground structures of the plant—stems, leaves, and flowers—die, but the bulb stays alive. In the spring or when circumstances are favorable, the bulb produces a new stem, new leaves, and new flowers. This adaptation helps plants survive harsh environmental conditions. An internal adaptation that some plants have is the xylem, which is a structure that moves water throughout the plant. The xylem is an adaptation that permits plants to grow in drier climates, allowing them to draw water up from deep in the soil. Not all plants have xylem. For example, mosses do not have xylem and are limited to growing in wet climates.

Look Out Natural selection does not have a “goal.” Organisms cannot plan to have “better” offspring. Organisms that are born with more favorable traits are more likely to survive and reproduce than organisms born with less favorable traits. Those organisms that survive and reproduce pass their traits on to the next generation. So what makes a trait more or less favorable? Many times it depends on the environment. A trait that is favorable for survival in the Arctic may not be favorable for living in the desert or the rain forest.

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STEMscopedia: NATURAL SELECTION, SURVIVAL AND REPRODUCTION Genetic Variation Genetic variation is vital for species survival. Read carefully to discover how it relates to natural selection. Natural selection describes how a population changes in response to alterations in its environment. Natural selection is possible because of genetic variation among organisms within a population. A population is a group of organisms of the same species inhabiting a specific region. The changes that occur to a population are called adaptations. The adaptations are inherited by offspring; therefore, they must be carried on genes. Alleles are different forms of genes. What can cause different alleles? Mutations are changes in alleles of genes. Mutations happen by chance and can either be beneficial, neutral, or harmful to organisms by producing either favorable, neutral, or unfavorable adaptations. Genetic variation refers to the variety of alleles that exist and are expressed in a population. Genetic variation guarantees a population a better chance for survival if the environment should suddenly change. There are many types of traits that can demonstrate genetic variation such as size, color, shape, formation of features, and function of body parts. One genetic variation expressed by squirrels is fur color.

What Do You Think? Genetic Variation and Natural Selection in Operation Imagine a population of hares living in an environment that is covered in snow most of the year. The climate has exhibited similar weather conditions for hundreds of years. There are two alleles for fur color in the hare population—one for brown fur and one for white fur. The hares with the allele for white fur have a better chance for survival because they are less visible to predators such as the foxes, wolves, and birds of prey. Therefore, most of the hare population have white fur. Only a small percentage of the brown hare population has managed to survive. Due to global warming, the climate of the hares’ environment warms and snow melts. Within a few years, there is only snow on the ground for a few weeks each year. Predators are now able to see the white hares on the brown dirt much more easily than the brown hares that camouflage into the new landscape. The brown hares survive to pass on their traits to their offspring. The trend begins to reverse so that the population of the brown hares increases and the population of the white hares decreases.

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STEMscopedia: NATURAL SELECTION, SURVIVAL AND REPRODUCTION

Which of the following graphs best expresses the situation of the hares described above?

What do you think would happen if, after 30 years of warm weather, the climate shifted and was cold again, resulting in snow covering the ground half the year?

What Do You Know? Populations and species demonstrate unique variations and inherited traits that have gradually changed over time as they were passed from one generation to the next. Changes in features through natural selection can enhance the survival of a species or produce desired genetic traits. One example of small-scale evolution in action is seen in the peppered moth. During the Industrial Revolution in Great Britain, factories emitted enough soot and smoke to blacken the bark of trees. Pale-colored moths that rested on the trees used to be camouflaged, but during this time, darker moths became the ones with the advantage. Darker moths blended in better with their environment, lived long enough to reproduce, and passed on darker coloring to their offspring. Darker coloring became the more advantageous adaptation in these moths. In the years since, smoke pollution has decreased and the population of the pale-colored moths is increasing once again. This demonstrates that natural selection partially depends upon the environment of an organism. Similar adaptations have occurred in other countries that had experienced industrial change. You are going to model how this gradual change in color helped protect peppered moths from predators.

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STEMscopedia: NATURAL SELECTION, SURVIVAL AND REPRODUCTION Materials • Sheet of white paper • Newspaper • Pencil • Tweezers or forceps • Timer • Hole punch • 30 circles punched out of newspaper with hole punch • 30 circles punched out of white paper with hole punch Procedure 1. Place a sheet of white paper on a table and spread the 30 newspaper circles and 30 white paper circles all over the sheet of white paper. 2. Acting as the “predator,” use the tweezers to pick up as many of the circles as you can in 15 seconds. 3. Record the data on the chart below. 4. Repeat the activity until you have completed each of the following trials: • • • • • •

White paper with both newspaper and white circles Newspaper with both newspaper and white circles White paper with white circles White paper with newspaper circles Newspaper with white circles Newspaper with newspaper circles Trial

Background

Circles: Starting Population Newspaper White

White

Newspaper

White

Newspaper

White

Newspaper

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Circles: Number Picked Up Newspaper White

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STEMscopedia: NATURAL SELECTION, SURVIVAL AND REPRODUCTION Answer the following questions about your experiment. 1. What did the experiment demonstrate about how prey are selected by predators? 2.

What moth coloration is the best adaptation for a dark (newspaper) background? How do you know?

After Trial 1, what would you expect the next generation of moths to look like?

After Trial 2, what would you expect the next generation of moths to look like?

Charles Darwin’s Ideas Charles Darwin believed that natural selection was the process for evolution. He published a book in 1859 that would change the scientific world called On the Origin of Species by Means of Natural Selection. Darwin reached the following four conclusions: • • • •

Over time, organisms change. All organisms descended from a common ancestor. Evolution is a gradual process. Natural selection is the method by which evolution occurs.

The Process of Natural Selection 1. Populations of organisms over-reproduce because many will not survive to reproduce their own offspring. Many members of populations will fall victim to predators, disease, lack of an adequate food supplies, and harsh climate conditions. 2. Populations possess individuals that express a variety of inherited traits. 3. Organisms that possess favorable adaptations survive to pass on their traits to their offspring. 4. The number of organisms possessing the favorable adaptations increases. There is potential for these organisms to eventually (over a long period of time) evolve into a new species.

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STEMscopedia: NATURAL SELECTION, SURVIVAL AND REPRODUCTION Connecting With Your Child Scientists in the Spotlight: Peter and Rosemary Grant Peter and Rosemary Grant are biologists who studied the Galapagos finches. They were able to observe natural selection over the course of a few generations of the finches when the environment drastically changed. For example, in 1977, a drought resulted in more large seeds and fewer smaller seeds being produced. The average beak size of medium ground finches was measurably larger after the drought than before the drought. Then, after a particularly wet year in 1985, the average finch beak was measurably smaller. Smaller seeds were more plentiful and smaller-beaked finches were more successful at survival and reproduction that year. This data is important because it helped scientists measure and describe natural selection. Obtaining the data took years of careful measuring and weighing. The Grants spent a few months each year on the Galapagos Islands. They measured the finches and collected weather data for many years. This dedication resulted in a long-term study that showed natural selection in action. Using the information from the Grants’ research on Galapagos finches, help your child to construct a graph that shows the trend of what happened to the sizes of the beaks of medium ground finches over a 10-year period from about 1976 to 1986. Make sure to discuss why the average size changes of the population occurred. Animal Adaptations Peter and Rosemary Grant’s finches and the peppered moths are just two examples of animal adaptations over time. Many species have evolved from their ancestors. With your child, research an animal species that has changed and discuss the adaptations that have evolved in that species. Compare the ancestors to the modern day species. How are they still similar? How have they changed? Here are some questions to discuss with your child. 1. What evidence have scientists found that supports the evolution of this species? 2. What type of environment supports these adaptations? 3. How would a major climate change affect this species?

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7L5AB Natural Selection, Survival, and Reproduction

Reading Science Name:

Date:

Group:

Darwin’s Fancy With Finches 1

Whales are mammals that live in water. They can hold their breath under the water for a long time, yet they still need to go up to the surface to breathe. This is evidence that the modern whale’s ancestors used to live on land. They changed over time to be able to live in the ocean. White hair in animals is due to the loss of the chemical that causes the hair to be colored. Biologists conclude that the ancestors to polar bears lost their dark hair over time. The change in polar bears and whales is described by a theory known as natural selection. This theory was described in 1859 in Charles Darwin’s book, On the Origin of Species by Means of Natural Selection. Through the process of natural selection, organisms evolve adaptations to their environment over time. Evolution means changes in the inherited traits of a species. Natural selection also plays a role in the origin of new species. Natural selection means that the organisms with traits that best fit their environment will be more likely to survive. Over time, they will have more offspring.

Charles Darwin was just 22 years old in 1831. He was sailing as a naturalist on the HMS Beagle. This journey led him to develop his theory of evolution. His job was to collect samples of plants and animals he found while sailing around the world. He found many unusual animals and plants in the Galápagos Islands. These islands are found 600 miles west of the coast of Ecuador. Darwin studied 14 types of small birds called finches. He wondered how there could be so many different, yet similar, species of finches living so close to each other on this chain of islands. For the next 20 years, Darwin studied the animals and plants he had found. He developed a hypothesis that became known as the theory of evolution by natural selection. Even today, this theory is one of the most important concepts in life science.

The following four factors describe natural selection: 1. In general, organisms have more offspring than can survive. 2. Individuals of a species have variations. 3. These variations affect the survival and reproduction of individuals. 4. Some variations enhance survival and reproduction in the offspring. These traits will become more and more common in the population over time.

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7L5AB Natural Selection, Survival, and Reproduction

Reading Science Continued 4

This is particularly true for variations that provide a survival advantage to individuals within the environment. Variations come from changes in an organism’s DNA, which is also known as mutation. Variations may include the organism’s color, chemical makeup, shape, and size. Camouflage coloring, for example, is a protective adaptation. An organism with camouflage can blend in with the environment to avoid predators. Those individuals that survive can have offspring. They will pass on those variations through their genes. This is how adaptation of species occurs.

Darwin’s finches are the classic example of how this can happen. He studied the types of beak sizes and shapes of the Galápagos finches. All 14 species of these finches are closely related. Each island has its own variations of environment from spot to spot. There are also changes over time. The environment had periods of severe drought. There were also long periods of El Niño with heavy rains. These variations affect the geography, climate, and plants of the islands. Finches that did not fit their environment did not survive. There was little or no human activity on the islands, so people had not had an effect on these species. Thus, biologists conclude that the adaptations in the finches are due to changes in environment and natural selection. Darwin studied how the size of the beaks related to the different diets of the different types of finch he found on the islands. Darwin described evidence that one species of finch was a “common ancestor” to all 14 species he had found. It had likely evolved into many different species on each island in the Galápagos. Environmental conditions affect the food types that grow on each island. The birds adapted to the local food sources on each island. The finches’ main adaptation was the shape and type of their beaks.

Today, adaptations of species can be seen in our everyday lives. For example, some insects evolved over many years to resist some of the chemicals used to kill them. Their resistance to insecticides has made it more and more difficult to control them. Insecticide resistance causes loss of money for farmers, and in some cases, the loss of the crops. Adaptations also affect human health. Biologists have seen that many harmful bacteria and viruses have evolved resistance to medicines used against them. One example is the HIV epidemic. Doctors have found that the HIV virus will rapidly evolve to resist drugs that had once been able to control it. Resistance to medicines is another example that illustrates Darwin’s natural selection process.

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7L5AB Natural Selection, Survival, and Reproduction

Reading Science 1.

What is natural selection? A

A process that happens in the absence of environmental conditions

A single process of adaptation within an individual

The survival of the fittest

An ability to predict the outcome of a defined species over time

What does Darwin’s controversial book, On the Origin of Species by Means of Natural Selection, illustrate? A

The importance of variations in organisms

That traits affect how likely an organism is to reproduce

How species evolve by adapting to their environment

All the above

Complete the following analogy: BEAK SIZE : GALÁPAGOS FINCHES :: WHITE HAIR : A

WHALES

TIGERS

GIRAFFES

POLAR BEARS

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7L5AB Natural Selection, Survival, and Reproduction

Reading Science 4.

Based on context, the term resistance in paragraph 6 means which of the following? A

Opposition

Approval

Variation

Individualized

Based on the information in paragraph 5, which of the finches in the diagram above is most likely to have adapted to an area where the main food source is large, hard seeds? A

(4)

(3)

(2)

(1)

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7L5AB Natural Selection, Survival, and Reproduction

Math Connections Name:

Date:

Group:

Applying the Hardy-Weinberg Principle The frequencies of alleles within a population change is due to different levels of reproductive success among individuals, as some produce more successful offspring than others. Allelic frequencies can also change when more individuals are produced than the environment can support, and strong competition for resources results. The Hardy-Weinberg equation is often used to test whether evolution is occurring in a population. The Hardy-Weinberg equilibrium states that, at a locus with two alleles, the three genotypes will appear in the following proportions: p2 Expected frequency of dominant homozygote (YY) 1.

2pq Expected frequency of heterozygotes (Yy)

q2 Expected frequency of recessive homozgote (yy)

Fill in the missing values in the Hardy-Weinberg diagram:

Phenotype Genotype frequency Number of Individuals (total = 500) Number of Alleles (total = 1000) Allelic frequency

Hardy-Weinberg Principle Parent Generation YY Yy 0.49 0.42 245

yy 0.09

210

Y: 2(245) + 210 = 700

y: 2(__) + 210 = ___

700Y/1000 total = 0.7

______ y/1000 =___

Hardy-Weinberg analysis

p(.7)

q(.3)

p(.7)

q(.3)

p2=.49

pq=.21

q2=.09

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2pq

predicted frequency of YY offspring

predicted frequency of Yy offspring

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7L5AB Natural Selection, Survival, and Reproduction

Math Connections Use the Hardy-Weinberg principle to help you answer the questions about this scenario: In plants, violet flower color (V) is dominant over white (v). If p = 0.8 and q = 0.2 in a population of 500 plants:

Phenotype Genotype frequency Number of Individuals (total = 500) Number of Alleles (total = 1000) Allelic frequency

Hardy-Weinberg Principle Parent Generation VV Vv 2 2pq p

vv q2

V: 2(___) +___ = ___

v: 2(__) + ___ = ___

___V/1000 total = ___

______v/1000 =___

What probability would you expect for a plant to be homozygous dominant (VV)?

What probability would you expect for a plant to be heterozygous (Vv)?

What probability would you expect for a plant to be homozygous recessive (vv)?

How many plants would you expect to have violet flowers?

How many plants would you expect to have white flowers?

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7L5AB Natural Selection, Survival, and Reproduction

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about the evolution of living organisms. WRITE Explain how physical characteristics of organisms have changed over successive generations, and describe ways in which species on earth have evolved due to natural selection. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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WRITING SCIENCE

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7th Grade Life Science

7L5C

Fossil Evidence of Organisms

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7L5C Fossil Evidence of Organisms

Student Handout

Name:

Date:

The Same or Not? Complete the Venn diagram below as you view the photos your teacher has provided.

Photo 1

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Photo 2

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7L5C Fossils as Evidence of Change

Student Journal Name:

Date:

Group:

Skeleton Sort! Activity Ever wonder how the dog evolved from the wolf? Or how the horse has changed over time? By studying fossils, we can learn how a species has changed to adapt to its environment. A paleontologist is a scientist who studies fossils and tries to identify the age and species of these organisms. In this activity, you act as a paleontologist and try to determine the chronological order of a series of skeletons. Answer the following questions below. 1.

What similarities did you notice in the horse skeletons over time?

What similarities did you notice in the dog skeletons and images over time?

What other tools or information could help you determine that these species are ancestors of the horse and dog?

Early horses lived in jungle areas with soft, wet ground. Eventually they moved out of the jungle onto the drier grasslands and steppes. Observe the pattern of the horse’s toes. Identify the cause and effect of this change.

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7L5C Fossils as Evidence of Change

Student Journal 5.

In general, the species Canis lupus (wolf) is larger than Canis lupus familiaris (dog). Although there are breeds of dogs that are larger than wolves, most modern dogs are smaller. So the pattern of adaptation is toward smaller animals. What might be the cause of this change?

What patterns can be used to identify the ancestry line of an organism?

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STEMscopedia: FOSSIL EVIDENCE OF ORGANISMS

7L5C

Reflect Evolutionary theory is the basic idea that life has existed for billions of years and has changed over time. Does the fossil record document all these changes? Paleontologists are scientists who study the fossil record. Fossil: mineral replacement, preserved remain, or trace of organisms that lived in the past Thousands of layers of sedimentary rock not only provide evidence of the history of Earth itself but also of changes in organisms whose fossil remains have been found in those layers. The collection of fossils and their placement in chronological order, such as through the location of the sedimentary layers in which they are found or through radioactive dating, is known as the fossil record. It documents the existence, diversity, extinction, and change of many life-forms throughout the history of life on Earth. What Evidence Exists for Evolutionary Change? The fossil record provides anatomical similarities and differences between organisms living today and in the past. Thus the fossil record enables scientists to infer the lines of evolutionary descent. Examples of this include the following: • insufficient oxygen (e.g., when an organism becomes trapped in amber) • low temperatures (e.g., when an organism becomes frozen in a glacier)

Preserved remains can help scientists understand human ancestry.

• high soil acidity (e.g., when an organism falls into a peat bog) However, if these conditions are not present, the remains will not be fossilized. This makes building up the story of evolution of any one species difficult. In most cases, there are big gaps in fossil records. It is often like putting together a jigsaw puzzle with half the pieces missing.

These mosquitoes have been preserved in amber.

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Fossil Formation Evidence of change is supported by two types of fossils. Trace fossils are the remains of ancient activity, such as the burrow left by a worm or a stone tool made by a prehistoric person. Body fossils are the preserved remains of the actual body parts of an animal or plant such as a skeleton or a pollen grain. Trace fossils are footprints, burrows, or impressions that were made by an animal or a plant while it was living and that have hardened into stone. For example, huge dinosaurs left their footprints preserved in the soft mud of a shallow sea that covered Central Texas 113 million years ago. The fossilized tracks provide clues to the habits of the dinosaurs, such as travelling in herds, or which species became predator or prey. The soft limestone mud also had fossils of palm trees and fossil shells that provide clues that a shallow sea once covered the area. Body fossils are the preserved parts of organisms or whole organisms. When most animals or plants die, they simply decay or are eaten by another animal. However, on rare occasions, an organism dies and is quickly covered by sediment at the bottom of a body of water. After layers of sediment accumulate, pressure causes minerals to replace the organism’s cells, or fill in a mold where the plant or animal had dissolved. Continued pressure causes the minerals to harden, and a fossil is formed if the rock layers are not disturbed. Sometimes, such as in the case of complete dinosaur skeletons, entire organisms are preserved. Another example is the Petrified Forest in Arizona where trunks of dead trees were washed up onto the sides of the rivers during big floods, and buried in sediment (dirt, rocks, sand, volcanic ash). Over time, minerals replaced the wood, creating entire petrified (fossilized) tree trunks. Fossils also formed in ancient times when insects were preserved in amber (hardened tree sap), or when mammoths died and were permanently frozen. However, most fossils found are simply fragments of the original organism.

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STEMscopedia: FOSSIL EVIDENCE OF The Fossil Record Shows Evolution From Simple to Complex Organisms Fossil remains have been found in sedimentary rocks of all ages. Fossils of the simplest organisms are found in the oldest sedimentary rocks, and fossils of more complex organisms are found in he newest rocks. This supports the theory of evolution, which states that simple life-forms gradually evolve into more complex ones. The chronological order of rock layers is usually determined by their order in an undisturbed sequence of strata. In undisturbed sedimentary rock, the oldest layers would be found at the bottom and the youngest layers would be found at the top. In disturbed rock layers, the determination must be made based on the presence of index fossils, comparison to undisturbed strata, or radiometric dating.

ORGANISMS In undisturbed rock, the sequence here can be read in chronological order from bottom (oldest) to top (youngest). The shark tooth fossil in layer 1 is older than the fern fossil in layer 3.

Evidence of Common Ancestry: Homologies The fossil record is not the only evidence that supports the common ancestry of organisms. Homologies, or similarities in characteristics between two organisms because they originated from a common ancestor, also support the common ancestry of organisms. A homologous structure is something that is similar in position, structure, or evolutionary origin. • Embryonic and Developmental Homologies: Comparison of the embryological development of different species also reveals similarities that show relationships not evident in the fully formed anatomy. Species with similar origins also show similar embryonic development patterns. We can learn a lot about a species by studying the embryo and patterns of development. For example, certain snake embryos have small buds that look like limbs. The buds disappear in later developmental stages. This suggests that snakes evolved from an ancestor that had limbs. • Anatomical Homologies: Species with common origins (e.g., birds, reptiles, and mammals) all show similar patterns of anatomy, such as those in the bones of the forelimbs. Anatomical homologies are similar anatomical structures that exist between species and can be identified as a link to a common ancestor. Mammals share certain traits such as breathing air, having hair or fur, and producing milk for their young. All mammals show similar patterns of bone structures in their forelimbs. Although the function of each is different, this diagram shows similarities in the anatomical structure of forelimbs in mammals (bat and human), birds (penguin), and reptiles (alligator).

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Note: The Geologic Time Scale on the below shows the fossil evidence of evolution for each major time division of Earth’s history.

Millions of Years Ago 0

Geologic Time Scale Era

Period

Cenozoic

Quaternary Tertiary

65 144

Cretaceous Mesozoic

Fossil Record

End of the Dinosaurs

Jurassic

213

Triassic

248

Permian

286 320

Carboniferous

Paleozoic

First Dinosaurs, Mammals, Birds

Swamps, Forests First Reptiles First Amphibians

360

Devonian

408

Silurian

438

Ordovician

First Land Plants

505

Cambrian

First Fishes

Precambrian

Precambrian Seas

590 700

Precambrian

First Invertebrates

4,600

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What Do You Think? Take a look at the photographs below. Do you think the elephant on the left is a direct descendant of the woolly mammoth on the right? Explain your reasoning.

How Does Evolution Occur? According to the theory of evolution, changes in species occur due to natural selection, reproduction, and environmental conditions. Charles Darwin proposed the theory of evolution by natural selection in 1859, which suggested that all creatures descended from common ancestors. His theory contended that organisms evolve through natural selection, a gradual process by which subsequent generations of organisms develop characteristics that help them survive in their surrounding conditions through mutations. Mutations that benefit an organism are passed on to subsequent generations. However, it is important to note that natural selection is not a deliberate process. Organisms do not choose which traits to pass on to their offspring—it is a natural process that favors certain traits in a particular environment. Organisms that do not have these favorable characteristics will gradually decrease in number, and the gene pool of the population will change. As Darwin’s theory was accepted, so was the theory of gradualism. This is the idea that evolution occurs gradually. Changes or adaptations appear slowly and sequentially over time. Usually, mutations are either harmful or neutral. In rare instances, a mutation proves beneficial to the organism. If so, it will occur more in the next generation and spread throughout the population. In this way, natural selection influences the evolutionary process, keeping and adding up the beneficial mutations and eliminating the harmful ones.

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What Do You Know? 1. Describe how the fossil record gives evidence of evolution.

2. Explain how evolution accounts for the diversity of living things.

3. Describe what life might have been like millions of years ago. What evidence is there for this?

4. How do physical characteristics of organisms demonstrate/support the theory of evolution?

5. How does natural selection affect the evolution of species on Earth?

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Connecting With Your Child Evolutionary Trees To help your child learn more about the theory of evolution, work together to create an evolutionary tree. Also called a phylogenetic tree or a tree of life, this diagram shows how species may be related to each other through physical characteristics, genetics, or character traits. According to Darwin’s theory of evolution by natural selection, all species share a common ancestor. First, have your child choose 12 organisms to include in the evolutionary tree, including three aquatic animals, three land mammals, three insects, and three reptiles. Search for photographs of these creatures on the Internet or in old magazines. Get a piece of large poster board, a ruler, glue, and a pencil. This evolutionary tree will focus on the physical characteristics of organisms. Brainstorm with your child different characteristics to use on the tree. Some ideas include: • presence or absence of a backbone • presence of hair, fur, or scales • warm or cold bloodedness • lungs or gills • external structures such as fins, claws, or hooves • food preference (omnivore, carnivore, or herbivore) Turn the poster board to a landscape format. Write “Common Ancestor” at the bottom of the poster board, and draw a large “Y” above the term. Leave plenty of room above the “Y” to draw your tree “branches.” Now choose a characteristic for each side of the “Y” (e.g., presence or absence of a backbone). Separate the 12 organisms into two piles according to this characteristic. Now look at the organisms in each group and choose a characteristic to separate each of the two groups into smaller groups. You might find that one group, such as the organisms without backbones, cannot be further separated. If this is the case, glue these organisms onto the correct side of the “Y” at the top. For any group(s) that can be further separated, draw a “V” on the correct side(s) of the “Y” at the top. Place the organisms on either side of the “V.” For characteristics such as hair, fur, or scales, you will need to draw an extra line or two on the “V”—one line for each form of the characteristic. Continue with this process until only one organism is left and glue the picture of the organism at the end of the branch. For ideas about how evolutionary trees are drawn and organized, you may want to do an Internet search prior to this activity using the term, “evolutionary tree.”

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7L5C Fossil Evidence of Organisms

Reading Science Name:

Date:

Group:

Dating Rocks 1

Canyons are like books. They tell the story of Earth’s past to those who can read them. The Grand Canyon tells more than one billion years of the story! Look at the picture at right. Notice that many layers are visible where the Colorado River has cut through the rocks. Each layer has a different color and is found at roughly the same position on both sides of the canyon. The oldest rocks are found in the bottom of the canyon, while the newest rocks are found near the rim. The river has carved the canyon over the last 5–6 million years.

Stratigraphy is the description and classification of sedimentary rock layers, or strata. It is used to determine the relative ages of rocks. In the 1600s, William Smith was nicknamed “Strata” by his friends for his interest in rock layers. The principles he came up with are still used in stratigraphy today. The first principle states that older rocks are on the bottom, and younger rocks are on the top. The next principle is that sediments are laid down horizontally. So layers that are at an angle must have moved after they were deposited. Another principle Steno suggested is that sediments deposit over a wide area. Just like snow does not fall only on one street corner, sediments are not limited to small areas. Therefore the same stratum can be observed in different locations. The last principle states that anything that cuts through strata has to have happened after the strata were deposited. So all the strata found in the Grand Canyon are older than the Colorado River’s path through them.

Sometimes a stratum provides clues to a particular event. One such event is the extinction that marks the end of the Cretaceous period. Dinosaurs and many other life-forms vanished in a short period of time. The speed and pattern of extinction gave rise to several theories. The composition of the stratum between the Cretaceous and Paleogene periods is unusual. This thin stratum is found all over the world. It is rich in iridium. Iridium is a metal that is very rare in the Earth’s crust but very common in asteroids. Scientists think a large asteroid containing a large amount of iridium hit the Earth. Iridium was then thrown into the atmosphere and deposited over time into the stratum. Two other pieces of evidence support an asteroid impact. Along the Gulf Coast and the Caribbean, deposits consistent with an ancient, large tsunami have been found. An impact crater is located in the Yucatan peninsula of Mexico. Scientists believe that the impact of the asteroid caused major changes in climate that led to the extinctions.

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Reading Science Continued 4

Combining stratigraphy with the fossil record allows scientists to extend Earth’s story to locations around the world. William Smith was a British geologist in the 1800s. He first observed strata in coal mines. Smith noticed that strata were always present in the same order in each mine. Moreover, he identified each stratum through the unique combination of plant and animal fossils it contained. These fossil combinations are known as assemblages. Fossils in older strata were of simpler organisms than fossils in younger strata. Because of his observations, Smith added another principle to the ones written by Steno. The principle of faunal succession states that each stratum contains a unique assemblage, or variety, of organisms. Furthermore, assemblages are observed in the same vertical order over large horizontal distances. If the same assemblage is found in a stratum in a distant location, both strata are assumed to have the same age.

The assemblage found in the rocks below the iridium-rich stratum contains the fossils of many familiar dinosaurs, such as Triceratops and Tyrannosaurus rex. Some areas of continents were covered in shallow oceans. Fossils of ammonites, a relative of squid, and carnivorous marine reptiles such as the mosasaur have been found. While mammal fossils were present, they were less common and small. Early mammals were often no larger than today’s rats. Immediately above the iridium-rich boundary layer, the number of different species found is much smaller. No dinosaur fossils exist. As the rocks move toward the surface from the iridium layer, there is a gradually increase in the number of different mammals and birds.

Stratigraphy can only provide the order of stratum formation. Scientists can state that one rock is older than another, but not exactly how old the rock really is. The location of specific fossils confirms the order. One can determine how old rocks are. Radiometric dating is a process used to determine the actual age of rocks. Radiometry relies on radioactive decay. Naturally occurring radioactive elements decay through a series of steps. Eventually, they transform into their nonradioactive end products. Each radioactive element decays with a predictable rate. The ratio of radioactive element to product therefore provides a date of when the rock became solid.

Several different elements are used for radiometric dating. Radioactive uranium decays into lead. The decay of uranium was used to date the oldest rock on Earth, which is a crystal of zircon found on a sheep ranch in Australia. The crystal is tiny, about twice the thickness of human hair in each dimension. Scientists measured the amount of uranium and lead in the crystal and found that it dates to about 4.4 billion years old! This suggests that the Earth had a solid crust at that time. The oldest fossils of microscopic life-forms date back to 3.4 billion years ago. However, some scientists believe older fossils might have been lost to recycling of the Earth’s crust. Stratigraphy, combined with radiometric dating of Earth’s rocks, tells a fascinating story of Earth’s history. To figure out the true age of Earth itself, we have to look to space.

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7L5C Fossil Evidence of Organisms

Reading Science 8

Sometimes The age of the Earth itself cannot be determined from Earth’s rocks. Rocks are constantly recycled back into the mantle only to become solid again. Scientists hypothesize that meteorites formed at the same time as Earth. As meteorites don’t recycle their components, the age of the meteorite will be the same as the age of its formation. Radiometric dating of meteorites yields an age of about 4.5 billion years.

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Reading Science 1.

Which of the following statements is NOT true about the Grand Canyon? A. The Grand Canyon is older than the rocks in its walls. B. The oldest rocks in the canyon are found near the bottom. C. The rock layers on both sides are in the same order. D. The canyon is about 5–6 million years old.

Scientists observe several strata that are tilted at an angle. What most likely caused the tilting? A. The strata were deposited at an angle. B. Fossils were deposited within each stratum. C. The strata were moved after they were deposited. D. The strata were deposited in a small area.

Scientists believe that the boundary stratum between the Cretaceous and Paleogene was caused by an asteroid. What evidence is most consistent with this theory? A. The stratum is found all over the world. B. The stratum is thin. C. The stratum contains iridium. D. Few fossils are found in the stratum.

Which statement best summarizes the principle of faunal succession? A. Different combinations of fossils are found in different strata. B. Some fossils are found in multiple strata, other fossils only in one stratum. C. Some strata contain marine fossils, while others contain fossils of terrestrial organisms. D. Fossils in older strata are more primitive than fossils in more recent strata.

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Reading Science 5.

What evidence is most consistent with dinosaurs becoming extinct at the end of the Cretaceous era? A. Mammal fossils are rare in the Cretaceous and numerous in the Paleogene. B. No dinosaur fossils are found above the Cretaceous Paleogene boundary. C. The Cretaceous Paleogene boundary layer contains few or no fossils. D. Dinosaur fossils are not found in the oldest rocks on Earth.

Radioactive uranium decays into lead. What relative amount of uranium and lead would the reader expect to find in the oldest rocks? A. Very little uranium and very little lead B. A lot of uranium and very little lead C. Very little uranium and a lot of lead D. A lot of uranium and a lot of lead

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7L5C Fossil Evidence of Organisms

Math Connections Name:

Date:

Group:

Radioactive dating is used to date specimens of igneous rock. Elements can vary in form based on a difference in the number of neutrons in the atom’s nucleus. These various forms are called isotopes. Some isotopes are radioactive and can be used to date rocks using their known half-life, the amount of time for the original number of atoms to fall to half its original value. Different minerals contain different radioactive isotopes. Once the rock has cooled, radioactive decay begins, and the original, or parent, atoms begin to decay and form daughter atoms. The proportion of the parent to daughter atoms in a substance can tell us how many half-lives have occurred. The number of half-lives is multiplied by the length of one half-life, and the age of the substance is revealed. This chart shows the parent isotopes, daughter isotopes, and half-life of the parent isotopes. Parent Isotope

Daughter Isotope

Half-life of Parent

Uranium-235

Lead-207

704 billion years

Rubidium-87

Strontium-87

48.8 billion years

Thorium-232

Lead-208

14 billion years

Uranium-238

Lead-206

4.74 billion years

Potassium-40

Argon-40

1.25 billion years

Carbon-14

Nitrogen-14

5730 million years

A rock sample from an area in southern Canada contained the mineral muscovite with a ratio of potassium-40 to argon-40 proportional to 0.058 of a half-life. What is the age of the specimen? (Use scientific notation to simplify the problem.)

A sandstone rock sample from Western Australia was found to contain zircon crystal with a ration of uranium-238 to lead-206 proportional to 0.89 of a half-life. What is the age of the specimen? (Use scientific notation to simplify the problem.)

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Math Connections The proportion of the parent to daughter atoms in a substance can tell us how many half-lives have occurred. To calculate the fraction of original parent material left in a specimen, you can use the number of half-lives as follows: y=1/2x, where y is the fraction of original material, and x is the number of half-lives. Use the equation above to calculate how much of a parent isotope is left based on the number of half-lives experienced. Assume 100 parent atoms are in the original specimen. Number of Parent Atoms

Number of Daughter Atoms

Number of HalfLives

Fraction of Original Material Left

100

0.4

3/4

1/2

2 .

3 4 5 6

3. Plot the relationship of: (a) number of parent atoms vs. number of half-lives and (b) number of daughter atoms vs. number of half-lives on the graph below. Use a different color and a different label on each line.

Number of Atoms

100

Key

Parent Daughter

50 25

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3 4 Number of Half-Lives

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7L5C Fossil Evidence of Organisms

Math Connections 4. Describe the relationships on the graph. Are they linear?

5. How does the number of parent atoms compare to the number of daughter atoms?

In 1990, Sue, the most complete Tyrannosaurus Rex skeleton discovered to date, was found in the hills of South Dakota. The ratio of carbon-14 to nitrogen-14 was 99 to 1. The number of half-lives of the carbon-14 was found to be 0.011. 6. Use your charts to find the age of Sue.

7. What was the fraction of original material left?

Suppose you had 5 rock specimens, all containing the fictitious radioactive isotope “funium" (Fu). Funium decays into the daughter isotope called “gamesium" (Ga) The half-life of Fu is 50 million years. Use your chart above to help you figure out the half-life of each specimen.

Sample

Number of Fu Atoms

Number of Ga Atoms

Fraction of Original Material Left

Half-Life

Age in Millions of Years

13.

240

14.

120

1/2

15.

180

1/4

100

16.

210

1/8

150

17.

225

1/16

200

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7L5C Fossil Evidence of Organisms

WRITING SCIENCE Name:

Date:

Group:

LOOK

THINK Think about fossils and where they are found. WRITE Explain how fossils found in sedimentary rock layers provide evidence that life forms have changed over time. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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WRITING SCIENCE

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GLOSSARY OF TERMS abiotic

balance

abiotic – not living or produced asexual reproduction – the reproductive process that by living things involves one parent and Animalia – major group of produces offspring identical to animals that does not contain the parent prokaryotes. all the members of this kingdom are multicellular autotroph – an organism that obtains its energy from an eukaryotes abiotic source such as sunlight animals – multicellular or inorganic chemicals eukaryotic organisms in bacteria – one of the kingdom Animalia three taxonomic domains; aquatic – relating to water; includes prokaryotic, singleliving in or near water or taking celled organisms that lack a place in water membrane-enclosed nucleus and that can be classified Archaea – kingdom of by shape; microorganisms unicellular organisms that are important as decomposers; prokaryotes like bacteria but widely distributed and can also share characteristics with break down just about any type eukaryotes of organic matter asexual – a method of reproduction that requires only one parent

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balance – to bring into or to maintain in a state of equilibrium

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GLOSSARY OF TERMS behavior

behavior – how something acts binary fission – a type of asexual reproduction in which one cell divides to form two identical cells; occurs in prokaryotic cells biodiversity – the number of different species of plants and animals in an area biotic – living or produced by living things cell – the smallest unit of an organism; it is enclosed by a membrane and performs life functions cell – the basic structural and functional unit of living organisms cell membrane – a protective layer that surrounds a cell or an organelle

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classification

cell wall – a tough, protective barrier that surrounds the outer membrane of some types of cells chloroplast – a membranebound organelle in plants that is the site of photosynthesis chromosome – a structure made of DNA that contains the genetic information needed to make new cells and carry out cell functions circulatory system – body system that circulates blood through the body, supplies oxygen and nutrients, and removes waste classification – the grouping and characterization of things based on systematic examination and shared characteristics

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GLOSSARY OF TERMS commensalism

endocrine system

commensalism – an interaction between organisms in which one organism benefits, and the other neither benefits nor harms”

desert – a barren area of land where little precipitation occurs and consequently living conditions are hostile for plant and animal life

community – all of the populations of different species in a particular area

digestive system – the group of organs that work together to break down food by physical and chemical processes into nutrients that the body can use

competition – more than one individual or population in an ecosystem relying upon the same limited resources

ecosystem – a system consisting of all of the interactions that occur between consumer – an organism that the abiotic and biotic factors must consume other organisms within an environment; a for nutrients system comprising all the biotic and abiotic factors in an area cytoplasm – the jelly-like and all the interactions among material inside the outer them membrane of a cell that holds the nucleus, organelles, and endocrine system – body other components of the cell system that regulates the body by secreting hormones into the decay – the natural process or bloodstream; controls growth, result of being slowly broken reproduction, and metabolism down or decomposed, chiefly by bacteria and fungi © Accelerate Learning Inc. - All Rights Reserved

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GLOSSARY OF TERMS estuaries

estuaries – the opening of a freshwater river into a large body of salt water eukaryote – all living organisms other than the eubacteria and archaebacteria; made up of cells with DNA in the form of chromosomes in a nucleus eukaryotic – a cell containing a membrane-enclosed nucleus and organelles evolution – change in the frequencies of alleles in a population over time excretory system – body system that filters, collects, and removes excess fluids and wastes from the bloodstream expression – the process of making known one’s thoughts, feelings, or appearance

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freshwater ecosystem favorable traits – a trait that is beneficial to an organism and will likely be selected by natural selection food chain – a path of energy transfer from one organism to another food web – overlapping food chains with different pathways for the flow of food energy in an ecosystem fossils – impressions of organisms left in rock layers that indicate the organisms once lived in the area freshwater ecosystem – an ecosystem found in streams, lakes, and rivers where the water has less than 1% salt content

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GLOSSARY OF TERMS Fungi

Fungi – kingdom of heterotrophic eukaryotes that reproduce through asexual spores and have chitin in their cell wall; microorganisms important as decomposers; widely distributed and can break down just about any type of organic matter gene pool – all the genes in a population generation – all of the offspring that are at the same stage of descent from a common ancestor; mothers and daughters represent two separate groups

imprint

genetics – the study of genes, heredity, and variation in living organisms habitat – the place where an organism naturally lives and grows heredity – process of characteristics transmitted from parent to offspring heterotroph – an organism that must consume other organisms for energy host – an organism within or upon which another organism (parasite, commensal, or mutualist) resides

genes – the basic physical and functional unit of heredity made human interaction – how humans affect and interact with up of DNA their surrounding environment genetic variation – differences imprint – a distinctive mark, in the alleles among the symbol, or logo left behind as members of a population an impression © Accelerate Learning Inc. - All Rights Reserved

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GLOSSARY OF TERMS inherited characteristics inherited characteristics – a characteristic that is passed from parent to offspring inherited traits – passing of a trait from a parent to an offspring

mutualism

marine ecosystem – an ecosystem found in oceans, seas, and gulfs where the water has a salt content of at least 3.5%

mitochondria – the organelle where cellular respiration takes integumentary system – body place in eukaryotic cells system that reacts to external model – a smaller or larger environmental conditions and physical copy of an object protects the body’s deeper tissues multicellular – an organism made up of more than one, kingdoms – the highest level often different, cells of taxonomic classification beneath that of the three muscular system – body domains system that allows the body to move and provides strength, limiting factors – biotic or balance, and warmth abiotic environmental factors that restrict the growth of a mutualism – an interaction population between organisms or species lysosome – organelle involved that is helpful to both in the breakdown of foreign material and debris using digestive enzymes 298

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GLOSSARY OF TERMS natural selection

natural selection – process of selection whereby favorable traits become more common and less favorable traits become less common in following generations; differential survival and reproductive success among a group of organisms due to differences in the inherited traits or characteristics of the organisms nervous system – body system that functions as the control center, coordinating all actions and reactions niche – the ecological role played by an organism

phsiology

offspring – a new living thing made by other living things organ – a large mass of similar tissue that make up a part of an organism that performs a specific function organelle – a membranebound structure inside a eukaryotic cell that performs a specific function or set of functions organism – a living thing such as a plant or animal; any continuous mass, or a series of things in contact or in proximity to a living system

parasitism – the symbiotic nucleus – a membrane-bound relationship in which one structure in eukaryotic cells that organism benefits while the other is harmed contains the DNA occurrence – how often something appears

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physiology – the study of living organisms and their parts

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GLOSSARY OF TERMS Plantae

Plantae – kingdom of autotrophic eukaryotes that includes all plants plants – multicellular eukaryotes of the kingdom Plantae population – members of the same species that live in the same geographical area; may be distinctly different than populations living elsewhere due to the spread of local adaptations within a population; a group of interacting organisms of the same species predator – an organism that captures and consumes another organism for nourishment prey – an organism that is captured and consumed by another organism for nourishment

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reproduction

producer – an organism that is capable of performing photosynthesis, transforming energy from the Sun, and using carbon dioxide and water to make food prokaryote – organism that lacks a true nucleus and membrane-bound organelles prokaryotic – a cell lacking a nucleus or any other membrane-enclosed organelle protist – a large group of eukaryotic organisms which belong to the kingdom Protista Protista – kingdom of singlecelled and simple multiplecelled eukaryotic organisms reproduction – the process by which organisms produce more of their own kind

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GLOSSARY OF TERMS reproduction system

reproduction system – male and female systems used to produce offspring respiratory system – body system in which breathing supplies oxygen to the blood and gets rid of carbon dioxide

systems

sexual reproduction – the reproductive process involving two parents whose genetic material is combined to produce a new organism different from themselves skeletal system – body system that holds organs in place, provides structural support, stores minerals, and generates new blood cells

sediments – Earth material that is broken down by processes of weathering; can be eroded and deposited by the agents of water, wind, ice, and species – a group of organisms with similar gravity characteristics that are able to selective breeding – a form interbreed or exchange genetic of artificial selection whereby material deliberate breeding results survival – the avoidance of in desired traits in plants or death or extinction animals sexual – a method of reproduction that requires both a male and female parent

SSS GA18 SN Grade 7.indb 301

systems – a set of interacting components forming an integrated whole or set of elements

301

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GLOSSARY OF TERMS taiga

variation

variation – a distinct feature, behavior, or physiology of an organism that occurs to individuals within a population temperate – related to a region or species or climate characterized by mild temperatures taiga – a biome characterized by its coniferous evergreen forests and cold temperatures

terrestrial biome – biomes that are on or of Earth tissue – a large mass of similar cells that make up a part of an organism and perform a specific function trait – a characteristic of an organism controlled by genetics tropical rainforest – an ecosystem that occurs close to the equator tundra – a biome characterized by vast, treeless plains and extremely cold temperatures unicellular – an organism made up of one cell 302

SSS GA18 SN Grade 7.indb 302

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7 STEMscopes Georgia Student Notebook

I belong to:

a part of STEMscopes NGSS

Georgia_7th_Book.indd 1

7th grade

My teacher is:

developed by Accelerate Learning, Inc. & Rice University

Notebook

(800) 531-0864

6/23/17 11:20 AM