7 the evolution of living things compression guide ... · pdf filethe evolution of living...

OBJECTIVES LABS, DEMONSTRATIONS, AND ACTIVITIES TECHNOLOGY RESOURCES

Compression guide:To shorten instructionbecause of time limitations,omit Section 3.

The Evolution of Living ThingsChapter Planning Guide

Chapter Opener

OSP Lesson Plans TR Bellringer Transparency* TR LINK TOLINK TO EARTH SCIENCEEARTH SCIENCE E8 The Rock

Cycle* TR L22 Evidence of Whale Evolution: A* TR L23 Evidence of Whale Evolution: B* TR L24 Comparing Skeletal Structures*CD Science Tutor

SE Connection to Geology Sedimentary Rock,p. 169 ◆g

TE Connection Activity Math, p. 169a TE Connection Activity Art, p. 170 ◆a

TE Connection Activity Geography, p. 171a

Section 1 Change over Time• Identify two kinds of evidence that show that

organisms have evolved.• Describe one pathway through which a modern

whale could have evolved from an ancient mammal.• Explain how comparing organisms can provide

evidence that they have ancestors in common.

OSP Lesson Plans TR Bellringer Transparency* TR L25 Four Parts of Natural Selection* CRF SciLinks Activity*g VID Lab Videos for Life ScienceCD Science Tutor

TE Demonstration Form and Function, p. 175 ◆g

TE Connection Activity Social Studies, p. 175a TE Connection Activity Geography, p. 176g SE Quick Lab Population Growth Versus Food Supply,

p. 177 ◆g

CRF Datasheet for Quick Lab* TE Activity Natural Selection, p. 178b SE Inquiry Lab Survival of the Chocolates, p. 184gCRF Datasheet for Chapter Lab*

PACING • 90 min pp. 174–179Section 2 How Does Evolution Happen?• List four sources of Charles Darwin’s ideas about

evolution.• Describe the four parts of Darwin’s theory of

evolution by natural selection.• Relate genetics to evolution.

OSP Lesson Plans TR Bellringer Transparency* TR L26 Evolution of the Galápagos

Finches* TE Internet Activity, p. 181gCD Science Tutor

TE Connection Activity Real World, p. 181g TE Group Activity Amazing Adaptations, p. 181a SE Science in Action Math, Social Studies, and Language

Arts Activities, p. 190–191g LB Whiz-Bang Demonstrations Adaptation Behooves

You* ◆g

LB Long-Term Projects & Research Ideas Evolution’sExplosion*a

PACING • 45 min pp. 180–183Section 3 Natural Selection in Action• Give three examples of natural selection in action.• Outline the process of speciation.

OSP Parent Letter ■

CD Student One Stop CD Guided Reading Audio CD ■

TR Chapter Starter Transparency* VID Brain Food Video Quiz

SE Start-up Activity, p. 165 ◆gpp. 164–173PACING • 90 min

163A Chapter 7 • The Evolution of Living Things

7

CRF Vocabulary Activity*g SE Chapter Review, pp. 186–187g CRF Chapter Review* ■g

CRF Chapter Tests A* ■g, B*a, C*s SE CRCT Preparation, pp. 188–189gWB CRCT Preparation Workbook*gWB GPS Review Guide*

OSP Test Generator, Test Item ListingTR GPS Review Transparencies*

CHAPTER REVIEW, ASSESSMENT, ANDSTANDARDIZED TEST PREPARATION

PACING • 90 min

Visit go.hrw.com foraccess to Holt OnlineLearning, or enter thekeyword HL7 Homefor a variety of freeonline resources.

This CD-ROM package includes:• Lab Materials QuickList Software• Holt Calendar Planner• Customizable Lesson Plans• Editable Worksheets

• ExamView® Version 5Assessment Suite

• Interactive Teacher’s Edition• Holt PuzzlePro®

• Holt PowerPoint® Resources

Online and Technology Resources

STANDARDS CORRELATIONSKILLS DEVELOPMENT RESOURCES SECTION REVIEW AND ASSESSMENT CORRELATIONS

CRF Directed Reading A* ■b, B*sWB Interactive Textbook* Struggling ReadersStruggling Readers

CRF Vocabulary and Section Summary* ■g

SE Reading Strategy Paired Summarizing, p. 166g TE Connection to Earth Science Rock Layers, p. 168g TE Support for English Language Learners, p. 170 SE Math Practice The Weight of Whales, p. 171g TE Inclusion Strategies, p. 171

SE Reading Checks, pp. 166, 168, 170, 172g TE Reteaching, p. 172b TE Quiz, p. 172g TE Alternative Assessment, p. 172a TE Homework, p. 173g SE Section Review,* p. 173 ■g

CRF Section Quiz* ■g

S7CS3.e, S7L5, S7L5.a,S7L5.c



SE Reading Strategy Brainstorming, p. 174g TE Connection to Geography Galápagos, p. 175g TE Support for English Language Learners, p. 175 TE Reading Strategy Prediction Guide, p. 176g MS Math Skills for Science Multiplying Whole Numbers*g CRF Reinforcement Worksheet Bicentennial Celebration*b

SE Reading Check, p. 175g SE Standards Checks, pp. 176, 177, 178g TE Homework, p. 174g TE Homework, p. 176a TE Reteaching, p. 178b TE Quiz, p. 178g TE Alternative Assessment, p. 178a SE Section Review,* p. 179 ■g


S7CS1.b, S7CS3.b, S7CS5.a,S7CS6.c, S7CS8.c, S7CS9,S7L3.c, S7L5, S7L5.a, S7L5.b



SE Reading Strategy Prediction Guide, p. 180g TE Support for English Language Learners, p. 181 TE Inclusion Strategies, p. 182 ◆

CRF Critical Thinking Taking the Earth’s Pulse*a

SE Reading Check, p. 182g SE Standards Check, p. 181g TE Reteaching, p. 182b TE Quiz, p. 182g TE Alternative Assessment, p. 182a SE Section Review,* p. 183 ■g


S7CS3.a, S7L5, S7L5.b

SE Pre-Reading Activity, p. 164gWB Science Puzzlers, Twisters & Teasers*gSE Science Skills Activity Understanding Accuracy and Precision,

pp. 183A–183BgOSP Datasheet for Science Skills Activity*

Chapter 7 • Chapter Planning Guide 163B

Georgia PerformanceStandards

S7CS3.f, S7CS5.b

CRF Chapter Resource File SS Science Skills Worksheets WB WorkbookOSP One-Stop Planner MS Math Skills for Science Worksheets * Also on One-Stop Planner

SE Student Edition LB Lab Bank CD CD or CD-ROM ◆ Requires advance prepTE Teacher Edition TR Transparencies VID Classroom Video/DVD ■ Also available in Spanish

KEY

Maintained by the NationalScience Teachers Association.See Chapter Enrichment pagesthat follow for a complete listof topics.

www.scilinks.orgCheck out Current Sciencearticles and activities byvisiting the HRW Web siteat go.hrw.com. Just typein the keyword HL5CS07T.

• Lab Videos demonstratethe chapter lab.

• Brain Food Video Quizzeshelp students review thechapter material.

ClassroomVideos

• Guided Reading Audio CD(Also in Spanish)

• Student One Stop• Virtual Investigations• Visual Concepts• Science Tutor

ClassroomCD-ROMs

Search for any lab by topic, standard,difficulty level, or time. Edit any lab tofit your needs, or create your own labs.Use the Lab Materials QuickList softwareto customize your lab materials list.

Planning ResourcesTEST ITEM LISTINGPARENT LETTERLESSON PLANS

Visual ResourcesCHAPTER STARTER

TRANSPARENCYBELLRINGER

TRANSPARENCIES

CONCEPT MAPPING TRANSPARENCYTEACHING TRANSPARENCIES

TEACHING TRANSPARENCIES

This CD-ROM includes all of the resources shown here and the following time-saving tools:

• Lab Materials QuickList Software

• Customizable lesson plans

• Holt Calendar Planner

• The powerful ExamView ®

Version 5 AssessmentSuite

Copyright © by Holt Rinehart and Winston All rights reserved

MULTIPLE CHOICE

1. A limitation of models is thata. they are large enough to see.b. they do not act exactly like the things that they model.c. they are smaller than the things that they model.d. they model unfamiliar things.Answer: B Difficulty: I Section: 3 Objective: 2

2. The length 10 m is equal toa. 100 cm. c. 10,000 mm.b. 1,000 cm. d. Both (b) and (c)Answer: B Difficulty: I Section: 3 Objective: 2

3. To be valid, a hypothesis must bea. testable. c. made into a law.b. supported by evidence. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2 1

4. The statement "Sheila has a stain on her shirt" is an example of a(n)a. law. c. observation.b. hypothesis. d. prediction.Answer: B Difficulty: I Section: 3 Objective: 2

5. A hypothesis is often developed out ofa. observations. c. laws.b. experiments. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2

6. How many milliliters are in 3.5 kL?a. 3,500 mL c. 3,500, 000 mLb. 0.0035 mL d. 35,000 mLAnswer: B Difficulty: I Section: 3 Objective: 2

7. A map of Seattle is an example of aa. law. c. model.b. theory. d. unit.Answer: B Difficulty: I Section: 3 Objective: 2

8. A lab has the safety icons shown below. These icons mean that you should weara. only safety goggles. c. safety goggles and a lab apron.b. only a lab apron. d. safety goggles, a lab apron, and gloves.Answer: B Difficulty: I Section: 3 Objective: 2

9. The law of conservation of mass says the tot al mass before a chemical change isa. more than the total mass after the change.b. less than the total mass after the change.c. the same as the total mass after the change.d. not the same as the total mass after the change.Answer: B Difficulty: I Section: 3 Objective: 2

10. In which of the following areas might you find a geochemist at work?a. studying the chemistry of rocks c. studying fishesb. studying forestry d. studying the atmosphereAnswer: B Difficulty: I Section: 3 Objective: 2

Chapter Resources

Dear Parent,

Your son's or daughter's science class will soon begin exploring the chapter entitled “The

World of Physical Science.” In this chapter, students will learn about how the scientific

method applies to the world of physical science and the role of physical science in the

world. By the end of the chapter, students should demonstrate a clear understanding of the

chapter’s main ideas and be able to discuss the following topics:

1. physical science as the study of energy and matter (Section 1)

2. the role of physical science in the world around them (Section 1)

3. careers that rely on physical science (Section 1)

4. the steps used in the scientific method (Section 2)

5. examples of technology (Section 2)

6. how the scientific method is used to answer questions and solve problems (Section 2)

7. how our knowledge of science changes over time (Section 2)

8. how models represent real objects or systems (Section 3)

9. examples of different ways models are used in science (Section 3)

10. the importance of the International System of Units (Section 4)

11. the appropriate units to use for particular measurements (Section 4)

12. how area and density are derived quantities (Section 4)

Questions to Ask Along the Way

You can help your son or daughter learn about these topics by asking interesting questions

such as the following:

What are some surprising careers that use physical science?

What is a characteristic of a good hypothesis?

When is it a good idea to use a model?

Why do Americans measure things in terms of inches and yards instead of centimeters

and meters ?

163C Chapter 7 • The Evolution of Living Things

The Evolution of Living Things CHAPTER STARTER

The time is 50 million years ago. Theplace is a swamp in North America.Imagine yourself trekking through thesteamy swamp, sidestepping snakes andspiders. Suddenly, out of the trees dashesa 182 kg giant with a huge head, a thickneck, and long, muscular legs.

What is this beast? A velociraptor? Agiant sloth? A prehistoric bear? None ofthe above. It’s a Diatryma, a kind of flight-less bird that was common during theCenozoic era of prehistory, 57 to 35million years ago! Diatryma stood over2 m tall and had an enormous beak andsharp claws.

Scientists know about Diatryma frommany fossils dug up in Wyoming, NewMexico, and New Jersey. Diatryma wasprobably forced out of existence by largemammals. Though the monster bird islong gone, smaller versions of it live inpoultry coops around the world.Diatryma’s fossils indicate that it was adistant cousin of the present-day chicken!

Copyright © by Holt, Rinehart and Winston. All rights reserved.

What If . . . ?

The Evolution of Living Things BELLRINGER TRANSPARENCY


Section: Change Over TimeThe cockroach originated on Earth over 250 millionyears ago and is thriving today all over the world. Agiant deer that was 2 m tall first appeared less than1 million years ago and became extinct around11,000 years ago. Why do you think one animalthrived and the other one perished?

Record your answer in your science journal.

Section: How Does Evolution Happen?The following are characteristics that almost allhumans have in common: upright walking, hair,fingerprints, binocular vision, speech. List theadvantages and disadvantages of each characteristic.Do you think the advantages are greater than thedisadvantages? Why or why not?

Record your responses in your science journal.

Chapter: Rocks: Mineral Mixtures

of

that changed over that descended from

of

exists in the

of

The Evolution of Living Things CONCEPT MAPPING TRANSPARENCY


Use the following terms to complete the concept map below:evolution, evidence, extinct species, living species, common ancestors,DNA, time, fossil record, body structures

GPS REVIEW TRANSPARENCIES

1. According to the dichotomous key on the previous page, what is a flightless mammal that has a long, furry tail with a black tip, a white underbelly, and light brown fur on its body and face?

A beaver C longtail weasel

B eastern mole D opossum

2. According to the dichotomous key on the previous page, what is a mammal with a long, cylindrical, hairless tail and grasping, hand-like paws?

A beaver C opossum

B eastern mole D woodchuck

3. Below is part of a field guide that several students have been using to identify trees in a local park. The students notice that one plant h h dl h l h h f h f ll

Georgia ScienceStandard S7L1.a Grade 7

SAMPLE

SAMPLE SAMPLE SAMPLE

Chapter Enrichmentxx

This Chapter Enrichment provides relevant andinteresting information to expand and enhanceyour presentation of the chapter material.

Change over TimeEvolution of Whales and Other Mammals• Scientists think that all mammals evolved from a

shrewlike ancestor. This ancestor survived the massextinction that wiped out the dinosaurs about 65 mil-lion years ago. This hypothesis is supported by fossilsformed during and after the time of the dinosaurs.

• The first ocean-dwelling mammals appeared in thefossil record about 50 million years ago. Scientiststhink that these mammals were the ancestors ofwhales and shared an ancestor with the artiodactylgroup (even-toed, hoofed mammals). However, othertypes of aquatic mammals, such as dugongs, manatees,and sea lions, probably evolved separately and fromlater branches of the mammal lineage.

• In many ways, whales are more similar to their hoofedmammal relatives than they are to fish. Similaritiesinclude internal structures, behavior, and DNA. Also,whales swim by moving their tails up and down, in amotion similar to a gallop and to the swimming of anotter, whereas fish move their tails sideways.

Homologous Structures• Homologous structures are anatomical features that have

similar evolutionary and embryological origins andexhibit similar anatomical patterns. For example, birdwings, human arms, whale flippers, and deer forelimbsare all homologous. However, bird wings and butterflywings are analogous structures because they functionsimilarly but are anatomically dissimilar.

• Cellular components and biochemicals may also behomologous. For example, hemoglobin molecules fromdifferent vertebrate species have similar amino-acidsequences. But hemocyanin, which transports oxygenin crabs, has a very different sequence and is thereforeanalogous to hemoglobin; that is, the two moleculeshave a similar function but different structure.

Is That a Fact!◆ The California halibut belongs to the family Bothidae,

also known as the left-eyed flounders. Despite thename, about 40% of California halibut adults haveboth eyes on the right side of their body.

Convergent Evolution• When scientists study the fossils,

skeletons, and DNA of speciesthought to be related, the scien-tists sometimes find that theorganisms are not related at all.For example, the jerboa and thekangaroo rat look almost identi-cal, but scientists have concludedthat they have different ancestors.Such cases illustrate convergent evolution, where differ-ent species developed similar adaptations to similarenvironmental conditions and roles.

Frozen Fossils• In some cases, scientists can obtain DNA from ancient

tissues that have not completely decomposed or fossil-ized. Two Japanese geneticists are hoping to create amammoth-elephant hybrid by using tissue from aSiberian mammoth that died and was frozen thou-sands of years ago. However, the chances of findingintact DNA are small, and the genetic structures ofmammoths and elephants are not fully compatible.

Is That a Fact!◆ The human appendix is a vestigial organ, or an organ

that performs little or no apparent function but thatis thought to have had a function in ancestors. Theappendix is a narrow tube attached to the large intes-tine. In chimpanzees, gorillas, and orangutans, theappendix is an intestinal sac that helps them digesttough plant material.

Chapter Enrichment

163E Chapter 7 • The Evolution of Living Things

7

How Does Evolution Happen?Alfred Russel Wallace• Alfred Wallace (1823–1913) was born in England. He

came from a poor family and had no formal scientificeducation. Though originally interested in botany, hebegan to study insects with the encouragement ofBritish naturalist Henry Walter Bates, whom Wallacemet when he was about 20 years old. Bates andWallace explored the Amazon from 1848 to 1852 andfound much evidence to support a theory of evolutionby natural selection.

• From 1854 to 1862, Wallace traveled in the MalayArchipelago to find more evidence of evolution. In1855, he published a preliminary essay, “On the LawWhich Has Regulated the Introduction of NewSpecies.” Meanwhile, nearly 20 years after CharlesDarwin’s voyage on the HMS Beagle, Darwin was stillmulling over his data. In 1858, Wallace mailed anessay to Darwin that explained Wallace’s theory thatnatural selection pressures species to change.

• In July 1858, Wallace’s essay was presented along witha paper by Darwin at a meeting of the Linnean Societyin London. In the following year, after nearly twodecades of delay (because of his doubts and repeatedanalysis), Darwin published On the Origin of Species byMeans of Natural Selection.

Charles Lyell• Charles Lyell (1797–1875), the eldest of 10 children,

was born in Scotland and raised in England. He trav-eled with his father, who was a naturalist, to collectbutter flies and aquatic insects. Lyell continued thisinformal research throughout college. Lyell’s researchin geology led him to the belief that natural processesoccurring over millions of years have shaped Earth’sfeatures. This idea was known as uniformitarianism.Lyell’s work influenced Darwin’s formulation of thetheory of natural selection.

Natural Selection in ActionAdaptive Coloration• Penguins, puffins, killer whales, and blue sharks are

just some of the ocean animals that have white belliesand black or dark blue dorsal surfaces. This type of col-oration is called countershading. When seen from below,the white underside helps the animal blend into thelighter sky above the water. When viewed from above,the dark coloration makes the animal difficult to seeagainst the ocean depths.

Sexual Selection• Sexual selection is the term for the selection of traits

that is brought about by a specific pattern of mating.In many sexual organisms, members of one sex mustcompete with each other for access to mates. Biologiststhink this behavior results when one sex’s investmentin the next generation is greater than the other sex’s.At an extreme, the “choosiness” of one sex may drivethe evolution of traits that confer no apparent advan-tage to the opposite sex. The long tails and colorfulplumage of many male birds are considered examplesof such “runaway sexual selection.”

For background information about teaching strategies and

issues, refer to the Professional Reference for Teachers.

SciLinks is maintained by the National Science Teachers Associationto provide you and your students with interesting, up-to-date links thatwill enrich your classroom presentation of the chapter.

Developed and maintained by theNational Science Teachers Association

Topic: Species and AdaptationSciLinks code: HSM1433

Topic: Fossil RecordSciLinks code: HSM0615

Topic: Galápagos IslandsSciLinks code: HSM0631

Topic: Darwin and NaturalSelection

SciLinks code: HSM0378

Visit www.scilinks.org and enter the SciLinks code for moreinformation about the topic listed.

Chapter 7 • Chapter Enrichment 163F

PRE-READINGPRE-READING

The Evolutionof Living Things

About the PhotoCan you fi nd two eyes and a mouth in thisphoto? They belong to an adult fl ounder.Flounders live off the coast of Georgia and inother coastal areas. Adult fl ounders swim ontheir sides and have both eyes on one side oftheir body. These characteristics allow fl oun-ders to lie fl at and still see all of their sur-roundings. Flounders also look like the sandybottoms of their environment. These adapta-tions help fl ounders survive and reproduce.

Concept Map Beforeyou read the chapter, cre-ate the graphic organizer

entitled “Concept Map” described in theStudy Skills section of the Appendix. Asyou read the chapter, fill in the conceptmap with details aboutevolution and naturalselection.

Biological evolution explainshow populations changeover time.

TheBigIdea

7

Characteristics of ScienceS7CS1 Students will explore the importance of curiosity, honesty,openness, and skepticism in science and will exhibit these traits in their ownefforts to understand how the world works. S7CS3 Students will havethe computation and estimation skills necessary for analyzing data andfollowing scientifi c explanations. S7CS5 Students will use the ideas ofsystem, model, change, and scale in exploring scientifi c and technologicalmatters. S7CS6 Students will communicate scientifi c ideas and activitiesclearly. S7CS8 Students will investigate the characteristics of scientifi cknowledge and how that knowledge is achieved. S7CS9 Students willinvestigate the features of the process of scientifi c inquiry. S7CS10 Studentswill enhance reading in all curriculum areas.

ContentS7L3 Students will recognize how biological traits are passed on to successivegenerations. S7L5 Students will examine the evolution of living organismsthrough inherited characteristics that promote survival of organisms and thesurvival of successive generations of their offspring.

MathM7D1, M7P1, M7P3

Georgia Performance Standards

Georgia Performance Standards

Characteristics of ScienceS7CS1.b Understand that hypotheses can be valuable, even if they turn out not to be completelyaccurate. pp. 184–185S7CS3.a Analyze scientific data by using, interpret-ing, and comparing numbers in several equivalentforms, such as integers, fractions, decimals, andpercents. pp. 183, 190S7CS3.b Use the mean, median, and mode to analyzea set of scientific data. p. 179S7CS3.e Decide what degree of precision is ade-quate, and round off appropriately. p. 171S7CS3.f Address the relationship between accuracyand precision and the importance of each.pp. 183A–183B

S7CS5.a Observe and explain how parts can berelated to other parts in a system such as predator/prey relationships in a community/ecosystem. p. 177S7CS5.b Understand that different models (such asphysical replicas, pictures, and analogies) can beused to represent the same thing. p. 165S7CS6.b Write for scientific purposes incorporatingdata from circle, bar, and line graphs, two-way datatables, diagrams, and symbols. p. 187S7CS6.c Organize scientific information using appro-priate simple tables, charts, and graphs, and identifyrelationships they reveal. pp. 184–185S7CS8.c As prevailing theories are challenged bynew information, scientific knowledge may change.pp. 177, 179S7CS9 Students will investigate the features of theprocess of scientific inquiry. pp. 184–185

S7CS10.a Reading in all curriculum areas: Read aminimum of 25 grade-level appropriate books peryear from a variety of subject disciplines and partici-pate in discussions related to curricular learning inall areas. p. 190; Read both informational and fictional texts in a variety of genres and modes ofdiscourse. p. 191S7CS10.b Discussing books: Respond to a variety oftexts in multiple modes of discourse. p. 190S7CS10.c Building vocabulary knowledge:Demonstrate an understanding of contextual vocab-ulary in various subjects. pp. 173, 186; Use contentvocabulary in writing and speaking. p. 179; Exploreunderstanding of new words found in subject areatexts. pp. 178, 183S7CS10.d Establishing context: Explore life experi-ences related to subject area content. pp. 174, 191;

OverviewTell students that this chapterwill introduce them to evolution—the process by which popula-tions on Earth change over time.Evolution helps explain the vari-ations and adaptations that wesee in organisms around us andin evidence of the past.

Assessing PriorKnowledgeStudents should be familiarwith the following topics:

• scientific methods andmodels

• heredity and genetics

IdentifyingMisconceptionsStudents may have heard thatevolution is “just a theory.”But in academic biology, evolu-tion (defined as the processby which species change overtime) is accepted in the way that“cell theory” is now accepted.Furthermore, the theory ofevolution by natural selection(integrated with modern geneticknowledge) is considered to bestrongly supported and widelyaccepted. Specific models, mech-anisms, rates, and other aspectsof evolution continue to beinvestigated and debated amongscientists, but few biologistsdoubt that evolution happens.

7

164 Chapter 7 • The Evolution of Living Things

START-UPSTART-UP S7CS5.b

Out of Sight, Out of MindIn this activity, you will see how traits can affect thesuccess of an organism in a particular environment.

Procedure1. Count out 25 colored marshmallows and

25 white marshmallows.

2. Ask your partner to look away while you spreadthe marshmallows out on a white cloth. Do notmake a pattern with the marshmallows. Now,ask your partner to turn around and pick the firstmarshmallow that he or she sees.

3. Repeat step 2 ten times.

Analysis1. How many white marshmallows did your partner

pick? How many colored marshmallows did he orshe pick?

2. What did the marshmallows and the cloth rep-resent in your investigation? What effect did thecolor of the cloth have?

3. When an organism blends into its environment,the organism is camouflaged. How does thisactivity model camouflaged organisms in thewild? What are some weaknesses of this model?

Discuss in both writing and speaking how certainwords are subject area related. pp. 179, 183B

ContentS7L3.c Recognize that selective breeding can produce plants or animals with desired traits.pp. 176, 189S7L5 Students will examine the evolution of living organisms through inherited characteris-tics that promote survival of organisms and thesurvival of successive generations of their offspring. pp. 167, 177–181, 183, 187–189S7L5.a Explain that physical characteristics oforganisms have changed over successive generations (e.g. Darwin’s finches and pepperedmoths of Manchester). pp. 170–173, 175–176, 179,186–188

S7L5.b Describe ways in which species on earthhave evolved due to natural selection. pp. 178–183,186–189S7L5.c Explain how the fossil record found insedimentary rock provides evidence for the longhistory of changing life forms. pp. 168–170, 173,186, 188–189

MathM7D1.c Analyze data using measures of centraltendency (mean, median, and mode), includingrecognition of outliers. p. 179M7P1.b Solve problems that arise in mathemat-ics and in other contexts. pp. 183, 190M7P3.d Use the language of mathematics toexpress mathematical ideas precisely. p. 171

START-UPSTART-UP vvM A T E R I A L S

FOR EACH PAIR• cloth, white, approximately 20 cm � 20 cm• marshmallows, colored (all same color), miniature (25)• marshmallows, white, miniature (25)

Teacher’s Notes: Newspaper canbe used as an alternative tomarshmallows in this activity.Instead of using marshmallows,punch 25 holes from the classi-fied section of a newspaper and25 holes from newsprint in mul-tiple colors, such as the Sundaycomics. Instead of using cloth,use the newspaper for the back-ground. Spread the holes on thepaper, and have the “hunter”pick up as many as he or shecan in 15 s. Tally the results.

Answers

1. Answers may vary, but studentsare likely to pick up more coloredmarshmallows than white ones.

2. Sample answer: The marshmal-lows represent organisms thatcould be eaten; the cloth repre-sents the area where they live.

3. Sample answer: Many organismsin the wild blend into their sur-roundings by having colors orpatterns that make them hardto see. This might help them hidefrom things trying to eat them. Aweakness of this model is that it’svery simple—a real “wild” envi-ronment would be more than twocolors and would contain a vari-ety of organisms.

Chapter 7 • The Evolution of Living Things 165

CHAPTER RESOURCESTechnology

Transparencies • Chapter Starter Transparency

Student One Stop

Guided Reading Audio CD• English or Spanish

Classroom Videos• Brain Food Video Quiz

Workbooks

Science Puzzlers, Twisters & Teasers• The Evolution of Living Thingsg

READINGSKILLS

READING STRATEGY

Change over TimeIf someone asked you to describe a frog, you might say that afrog has long hind legs, has bulging eyes, and croaks. But whatcolor skin would you say that a frog has?

Once you start to think about frogs, you realize that frogs dif-fer in many ways. These differences set one kind of frog apartfrom another. The frogs in Figures 1, 2, and 3 look differentfrom each other, yet they may live in the same areas.

Differences Among OrganismsAs you can see, each frog has a different characteristic thatmight help the frog survive. A characteristic that helps anorganism survive and reproduce in its environment is called anadaptation.adaptation. Adaptations may be physical, such as a long neckor striped fur. Or adaptations may be behaviors that help anorganism find food, protect itself, or reproduce.

Living things that have the same characteristics may bemembers of the same species. A speciesspecies is a group of organismsthat can mate with one another to produce fertile offspring. Forexample, all strawberry poison arrow frogs are members of thesame species and can mate with each other to produce morestrawberry poison arrow frogs. Groups of individuals of thesame species living in the same place make up a population.

✓✓Reading Check How can you tell that organisms are membersof the same species?

1

Figure 1 The red-eyed treefrog hides among a tree’sleaves during the day andcomes out at night.

Figure 2 The brightcoloring of the straw-berry poison arrow frogwarns predators thatthe frog is poisonous.

Figure 3 The smokeyjungle frog blends intothe forest floor.

What You Will Learn

Identify two kinds of evidence thatshow that organisms have evolved.Describe one pathway through whicha modern whale could have evolvedfrom an ancient mammal.Explain how comparing organismscan provide evidence that they haveancestors in common.

Vocabularyadaptation fossilspecies fossil recordevolution

Paired Summarizing Read thissection silently. In pairs, take turnssummarizing the material. Stop todiscuss ideas that seem confusing.

S7CS3.e Decide what degree of precisionis adequate, and round off appropriately.

S7L5 Students will examine the evolution of livingorganisms through inherited characteristics thatpromote survival of organisms and the survival ofsuccessive generations of their offspring.S7L5.a Explain that physical characteristics oforganisms have changed over successive generations(e.g. Darwin’s fi nches and peppered moths ofManchester).S7L5.c Explain how the fossil record found insedimentary rock provides evidence for the longhistory of changing life forms.

GPS Review Guide

1

OverviewThis section introduces the con-cept of evolution as change overtime in populations of organ-isms. Students will survey evi-dence used to understandevolution and determine ances-try, including the fossil recordand comparisons of organisms’physical and genetic traits.

BellringerHave students respond to thefollowing prompt: “The cock-roach originated on Earth morethan 250 million years ago andis thriving today all over theworld. A giant deer (more than2 m tall!) evolved less than1 million years ago and becameextinct around 11,000 years ago.Why do you think one animalthrived and the other perished?”(Accept all reasonable answers.)

Discussion ----------------------------------gAdaptation Ask students if apolar bear could live comfort-ably in Hawaii. Ask if a fishcould sur vive in a forest. Why orwhy not? Discuss various charac-teristics of animals, such asphysical adaptations, that makethe animals well suited for aspecific environment. l Verbal

Answer to Reading Check

Organisms are members of the same species ifthey mate with each other and produce fertileoffspring.

CHAPTER RESOURCES

Chapter Resource File

CRF • Lesson Plan• Directed Reading Ab• Directed Reading Bs

Technology

Transparencies • Bellringer

Workbooks

Interactive Textbook Struggling Readers Struggling Readers

GPS Review Guide


GPS ReviewGuide

Use these worksheets to helpstudents review standardsS7CS3.e, S7L5, S7L5.a,S7L5.c

Do Species Change over Time?In a single square mile of rain forest, there may be dozens ofspecies of frogs. Across the Earth, there are millions of differ-ent species of organisms. The species that live on Earth todayrange from single-celled bacteria, which lack cell nuclei, tomulticellular fungi, plants, and animals. Have these speciesalways existed on Earth?

Scientists think that Earth has changed a great deal duringits history, and that living things have changed, too. Scientistsestimate that the planet is 4.6 billion years old. Since life firstappeared on Earth, many species have died out, and many newspecies have appeared. Figure 4 shows some of the species thathave existed during Earth’s history.

Scientists observe that species have changed over time. Theyalso observe that the inherited characteristics in populationschange over time. Scientists think that as populations changeover time, new species form. Thus, newer species descendfrom older species. The process in which populations gradu-ally change over time is called evolution.evolution. Scientists continue todevelop theories to explain exactly how evolution happens.

adaptationadaptation a characteristic that improves an individual’s ability to survive and reproduce in a particular environment

speciesspecies a group of organisms that are closely related and can mate to produce fertile offspring

evolutionevolution the process in which inherited characteristics within a population change over generationssuch that new species sometimes arise

Figure 4 This diagram shows some of the many kinds of organisms that have lived on Earth since the planet formed 4.6 billion years ago.

Using the Figure -----gSpecies and Change Ask stu-dents to compare the frogs inFigures 1, 2, and 3 and discussthe unique adaptations of each.Ask students: “If you see a frogthat looks like one of thesefrogs, can you assume that theyare both the same species? (no,not necessarily) How can you tell?(by whether they breed with eachother or not.) Next, have studentslook at Figure 4. Ask them howthey think changes in the planetcould have affected the appear-ance and disappearance of somany types of organisms overtime. (Sample answer: Tem peraturefluctuations due to ice ages andother climatic changes would haveaffected which plants and animalscould survive. Climate changescaused changes in the vegetationand in the availability of food foranimals. Until the planet was ableto support a lot of vegetation, therewouldn’t have been much food foranimals to eat.) l Visual/Verbal

Discussion ---------------------------------------b

Populations Versus SpeciesUnderstanding evolutionrequires understanding thatchanges in populations can leadto changes in species. Thus, stu-dents must be able to distin-guish between populations andspecies. Reinforce these mean-ings with the following exam-ples: All domestic cats are thesame species. Those that live inone city may be a population,but cats that live in other citiesare probably not part of thesame population. All of the liz-ards of a given species that liveon an island may be a singlepopulation and may be the onlypopulation of that species onthe island. All humans are thesame species, but they havemany populations. (Note thateven biologists are sometimesunsure about the designation ofclosely related groups oforganisms.) l Verbal

The gastric brooding frogs of Australia,now extinct, incubated their tadpoles intheir stomachs and gave birth to theiryoung through their mouths!

Is That a Fact!There are more than 100,000 livingmollusk species, and at least 35,000extinct forms are known from the fossilrecord. As a group, mollusks are verysuccessful—there have been molluskson Earth for nearly 600 million years.

Section 1 • Change over Time 167

Evidence of Changes over TimeEvidence that organisms have changed over time is buriedwithin Earth’s crust. The layers are made up of different kindsof rock and soil stacked on top of each other. These layersform when sediments, particles of sand, dust, or soil, are carriedby wind and water and are deposited in an orderly fashion.Older layers are deposited before newer layers and are burieddeeper within Earth.

FossilsThe remains or imprints of once-living organisms found in layersof rock are called fossils.fossils. Examples of fossils are shown inFigure 5. Fossils can be complete organisms, parts of organisms,or just a set of footprints. Fossils usually form when a deadorganism is covered by a layer of sediment. Over time, moresediment settles on top of the organism. Minerals in the sedi-ment may seep into the organism and gradually replace theorganism with stone. If the organism rots away completely afterbeing covered, it may leave an imprint of itself in the rock.

The Fossil RecordBy studying fossils, scientists have made a timeline of lifeknown as the fossil record.fossil record. The fossil record organizes fos-sils by their estimated ages and physical similarities. Fossilsfound in newer layers of Earth’s crust tend to be similar topresent-day organisms. This similarity indicates that the fossil-ized organisms were close relatives of present-day organisms.Fossils from older layers are less similar to present-day organ-isms than fossils from newer layers are. The older fossils areof earlier life-forms, which may not exist anymore.

Describe how fossils form. S7L5.c

Figure 5 The fossil on the left isof a trilobite, an ancient aquaticanimal. The fossils on the rightare of seed ferns.

fossilfossil the trace or remains of anorganism that lived long ago, mostcommonly preserved in sedimentaryrock

fossil recordfossil record a historical sequenceof life indicated by fossils found inlayers of the Earth’s crust

CulturalAwarenessCulturalAwareness g

Historic PaleontologistMary Anning (1799–1847)made some of the mostimportant fossil discoveriesof her time. She was born inLyme Regis in southern GreatBritain, an area with manyfossils. Her father, a cabinet-maker and amateur fossil col-lector, died when Anning was11 years old, leaving the fam-ily in debt. Anning’s fossil-finding skills provided thefamily with needed income.Even before she reached herteens, Anning had discoveredpart of the first Ichthyosaurusto be recognized by scientistsin London.

In the early 1820s, a profes-sional fossil collector sold hisprivate collection and gavethe proceeds to the Anningfamily. He recognized thatthey had contributed manyspecimens for scientificinvestigation. Soon after,Mary Anning took chargeof the family fossil business.However, many of Anning’sfinds ended up uncredited.Many scientists could notaccept that a person of herfinancial and educationalbackground could haveacquired such expertise. Havestudents research to find outone of Anning’s significantfossil finds (For example, shediscovered the first plesiosaurfossil.) l Verbal

Answer to Standards Check

Sample answer: Fossils form whenan organism dies and is covered bylayers of sediment. S7L5.c

CONNECTION toCONNECTION toEarth Science ---------------------------g

Rock Layers Using sedimentary layers asreference points, scientists can find the rela-tive age of a fossil. Use the teaching trans-parency entitled “The Rock Cycle” toillustrate the ways that sedimentary rock iscontinually formed on Earth. Tell studentsthat a common way for fossils to form isfor an organism to be buried under sedi-ment that becomes sedimentary rock. Pointout that a layer of sedimentary rock canform only on top of older rock. l Visual


Transparencies • LINK TOLINK TO EARTH SCIENCEEARTH SCIENCE E8 The Rock Cycle


70 0

hippopotamuses

camels and IIamas

pigs and peccaries

hoofed grazing mammals

toothed whales

baleen whales

Approximate time (millions of years ago)

Evidence of AncestryThe fossil record provides evidence about the order in whichspecies have existed. Scientists observe that all living organ-isms have characteristics in common and inherit characteristicsin similar ways. So, scientists think that all living speciesdescended from common ancestors. Evidence of commonancestors can be found in fossils and in living organisms.

Drawing ConnectionsScientists examine the fossil record to figure out the relation-ships between extinct and living organisms. Scientists drawmodels, such as the one shown in Figure 6, that illustratetheir hypotheses. The short horizontal line at the top left inthe diagram represents a species that lived in the past. Eachbranch in the diagram represents a group of organisms thatdescended from that species.

Scientists think that whales and some types of hoofedmammals have a common ancestor, as Figure 6 shows. Thisancestor was probably a mammal that lived on land between50 million and 70 million years ago. During this time period,the dinosaurs died out and a variety of mammals appeared inthe fossil record. The first ocean-dwelling mammals appearedabout 50 million years ago. Scientists think that all mammalspecies alive today evolved from common ancestors.

Scientists have named and described hundreds of thousandsof living and ancient species. Scientists use information aboutthese species to sketch out a “tree of life” that includes allknown organisms. But scientists know that their informationis incomplete. For example, parts of Earth’s history lack a fossilrecord. In fact, fossils are rare because specific conditions arenecessary for fossils to form.

Sedimentary Rock Fos-sils are most often found insedimentary rock. Sedi mentaryrock usually forms when rockis broken into sediment bywind, water, and other means.The wind and water move thesediment around and depositit. Over time, layers of sedi-ment pile up. Lower layers arecompressed and changed intorock. Find out if your area hasany sedimentary rocks thatcontain fossils. Mark the loca-tion of such rocks on a copy ofa local map.

Figure 6 This diagram isa model of the proposedrelationships between ancientand modern mammals that havecharacteristics similar to whales.

S7L5.c CONNECTIONCONNECTION vvMath ------------------------------------------------------------a

Species Countdown Present thefollowing scenario to students:Imagine that you are a scientifictime traveler assigned to countthe species in your home state1,000 years from now. You knowthat, at present, your home statecontains 2,300 animal speciesand 4,500 plant species. Butmany species are becomingendangered or extinct. Only 55%of the state’s species are expectedto remain in existence after1,000 years. How many speciesshould you expect to count dur-ing your visit to the future? (Tip:Round your answer to two signif-icant figures.) (animals:2,300 � 0.55 � approximately 1,300;plants: 4,500 � 0.55 � approxi-mately 2,500) l Logical

MISCONCEPTIONALERT

Adaptation on Purpose?Students commonly confuseevolutionary adaptationwith intentional change. Forexample, a student might saythat an organism “learns” toadapt or “grows” an adapta-tion to a changing environ-ment. Explain to studentsthat the evolution of adapta-tions happens to populationsover many generations.Evolution never happenswithin a single individual.And new traits arise by chanceand become adaptations in apopulation only if those traitsare both advantageous toindividuals and inheritedby individuals’ offspring.Students may also confuseevolutionary adaptation withacclimation, such as adjust-ment to seasonal changes.Adaptations that enable atype of organism to adjustto changing conditions canevolve, but adaptations evolveonly if traits conferring theadaptations are passed on tofuture generations.

Q: How did the dinosaurs listen to

music?

A: on their fossil records

How Many Toes? Hoofed mammals,or ungulates, are classified into two majorgroups. The even-toed artiodactyls haveeither two or four toes on each foot.Examples are pigs, deer, and cows. Theodd-toed perissodactyls carry their weighton a middle toe. Examples are horses,zebras, tapirs, and rhinoceroses. All ungu-lates have similar foot and ankle bones.


a

b

Examining OrganismsExamining an organism carefully can give scientists clues aboutits ancestors. For example, whales seem similar to fish. Butunlike fish, whales breathe air, give birth to live young, andproduce milk. These traits show that whales are mammals. Thus,scientists think that whales evolved from ancient mammals.

Case Study: Evolution of the WhaleScientists think that the ancient ancestor of whales was prob-ably a mammal that lived on land and that could run onfour legs. A more recent ancestor was probably a mammalthat spent time both on land and in water. Comparisons ofmodern whales and a large number of fossils have supportedthis hypothesis. Figure 7 illustrates some of this evidence.

✓✓Reading Check What kind of organism do scientists think wasan ancient ancestor of whales?

Ambulocetus (AM byoo loh SEE tuhs)This mammal lived in coastal watersabout 49 million years ago. It could swimby kicking its legs and using its tail forbalance. It could also waddle on landby using its short legs. Ambulocetus wasabout the size of a dolphin.

Pakicetus (PAK uh SEE tuhs)Scientists think that whales evolved from land-dwellingmammals that could run on four legs. One of theseancestors may have been Pakicetus, which lived about50 million years ago. The fossil skeleton and an artist’sillustration of Pakicetus are shown here. Pakicetus wasabout the size of a wolf.

Evidence of Whale EvolutionFigure 7

Using the Figure------gEvidence of Whale EvolutionHave students examine each ofthe skeletons in Figure 7 care-fully. Ask them to describe onesimilarity and one differencebetween each successive species.(Sample answer: Pakicetus andAmbulocetus have similar limbsand feet, but the limbs ofAmbulocetus are shorter in propor-tion to its body.)l Visual/Logical ee

CONNECTIONCONNECTION vvArt --------------------------------------------------------------------------------------a

Scientific Illustration Therole of a scientific illustratoris to create accurate picturesof organisms and objects thatscientists study. In the case oflong-extinct species, such asdinosaurs, artists must some-times fill in where science leavesoff. Have students look for andcompare several examples ofillustrations of a specific extinctorganism. Have students try toidentify ways in which artisticinterpretation is used. For com-parison, show students examplesof similar illustrations from hun-dreds of years ago, when muchless was known about manyfossil organisms.l Visual ee


a four-legged land mammal


Transparencies• L22 Evidence of Whale Evolution: A• L23 Evidence of Whale Evolution: B

SUPPORT FOR

English Language LearnersEvidence Students may not under-stand the word evidence. Help studentsdefi ne the word. Then, have them readthe diagram on whale evolution and,in a discussion setting, list the evidencethat whale ancestors lived on land.They may combine what they knowabout whales with information from thediagram to fi ll out the list. (live births,milk-producing, air breathing, tiny hipbones for legs not needed in water)l Verbal


Walking WhalesThe organisms in Figure 7 form a sequence between ancientfour-legged mammals and modern whales. Several pieces ofevidence indicate that these species are related by ancestry.Each species shared some traits with an earlier species. How-ever, some species had new traits that were shared with laterspecies. Yet, each species had traits that allowed it to survivein a particular time and place in Earth’s history.

Further evidence can be found inside the bodies of livingwhales. For example, although modern whales do not havehind limbs, inside their bodies are tiny hip bones, as shownin Figure 7. Scientists think that these hip bones were inheritedfrom the whales’ four-legged ancestors. Scientists often lookat this kind of evidence when they want to determine therelationships between organisms.

d Modern toothed whaleModern whales’ forelimbs are flippers.Modern whales do not have hindlimbs, but they do have tiny hip bones.Modern whales range in size from1.4 m porpoises to 33 m blue whales.

c Dorudon (DOH roo DON)This mammal lived in the oceans about 40 millionyears ago. It resembled a giant dolphin and propelleditself with its massive tail. Dorudon had tiny hindlimbs that it could not use for walking or swimming.

The Weight of WhalesWhales are the largest ani-mals ever known on Earth.One reason whales can growso large is that they live inwater, which supports theirweight in a way that theirbones could not. The bluewhale—the largest type ofwhale in existence—is about24 m long and has a massof about 99,800 kg. Convertthese measurements into feetand pounds, and round towhole numbers.

S7CS3.e, M7P3.d

Answer to Math Practice S7CS3.e,

M7P3.d

length: 24 m � 3.3 ft/m � 79 ftmass: 99,800 kg � 2.21 lb/kg � 221,000 lbNote: Each final answer should berounded to the least number of sig-nificant figures used in the calcula-tion of that answer.

CONNECTIONCONNECTION vvGeography ---------------------------------------------a

Inland Whales Explain tostudents that in 1849, workersconstructing a railroad near thetown of Charlotte, Vermont, dis-covered bones that were lateridentified as those of a belugawhale. Ask students to locateCharlotte on a map and explainwhy this discovery is so unusual.(Charlotte is more than 150 milesfrom the nearest ocean.) Ask stu-dents what these bones tell usabout the history of the landaround Charlotte. (It used to bepart of an ocean.) Explain that theChamplain Sea, an exten sion ofthe ocean, existed for 2,500years after the last glaciersretreated 12,500 years ago.Recently, many fossils of whaleancestors have been found nearthe Himalaya Mountains inPakistan. l Visual/Verbal

StrategiesStrategiesINCLUSIONINCLUSION

• Gifted and TalentedSome students benefit fromexploring a topic in greaterdepth. Ask these students toresearch current theoriesabout the evolution of whalesfrom ancient land mammals.Tell students to include thefollowing for each stage ofthe evolution: a picture (skel-etons or artist’s conception),how the animal walked ormoved, what it probably ate,what type of an environmentit probably lived in, and howit breathed.l Visual/Verbal

Is That a Fact!Baby blue whales can weigh about9 tons (9,000 kg or 20,000 lb) at birthand can grow to 190 tons. Blue whalesare baleen whales and are now thelargest of all whales. The largest amongthe toothed whales is the sperm whale.The largest sperm whale on recordweighed more than 50 tons. Toothedwhales include orcas, dolphins, porpoises,narwhals, belugas, beaked whales, andbottle-nosed whales.

A Vestigial Tail Scientists think thatthe tailbone in humans is a vestigialstructure. In other words, it is an inher-ited remnant of the tails of humans’mammal ancestors.


Comparing OrganismsEvidence that groups of organisms have common ancestry canbe found by comparing the groups’ DNA. Because every organ-ism inherits DNA, every organism inherits the traits determinedby DNA. Organisms contain evidence that populations andspecies undergo changes in traits and DNA over time.

Comparing Skeletal StructuresWhat do your arm, the front leg of a cat, the front flipper ofa dolphin, and the wing of a bat have in common? You mightnotice that these structures do not look alike and are not usedin the same way. But under the surface, they have similarities.Look at Figure 8. The structure and order of bones of a humanarm are similar to those of the front limbs of a cat, a dolphin,and a bat. These similarities suggest that cats, dolphins, bats,and humans had a common ancestor. Over millions of years,changes occurred in the limb bones. Eventually, the bonesperformed different functions in each type of animal.

Comparing DNAWhen scientists compare organism’s traits, such as skeletalstructures, much of the information that they get supportsthe theory that organisms share a common ancestor. To furthersupport this theory, scientists compare organisms’ DNA at amolecular level. Scientists analyze many organisms’ DNA, RNA,proteins, and other molecules. Then, scientists compare thedata for each species. The greater the number of similaritiesbetween the data sets for any two species, the more closely thetwo species are related through a common ancestor. Scientistsuse molecular data, the comparison of traits, and fossils tosupport the theory that because all existing species have DNA,all species share a common ancestor.

✓✓ Reading Check If two species have similar DNA, whathypothesis is supported?

Figure 8 The bones in thefront limbs of these animalsare similar. Similar bones areshown in the same color. Theselimbs are different sizes in life.

Human arm

Cat leg

Dolphin flipper

Bat wing

For another activity relatedto this chapter, go togo.hrw.com and type in thekeyword HL5EVOW.


that they have common ancestry Is That a Fact!In the late 1990s, analysis of geneticand hereditary molecular material froma variety of mammals showed thatwhales share more genetic similaritiesto hippopotamuses than to any otherliving mammal group.

Reteaching -------------------------------------bConcept Map While prompt-ing students for input, create alarge concept map with keyideas from this chapter. l Visual

Quiz --------------------------------------------------------------------g

1. Use the words adaptations,population, and evolutiontogether in a sentence.(Sample answer: Evolution is theprocess by which a popu lationaccumulates inherited adapta-tions over time.)

2. Why are scientists unsureabout some parts of the “treeof life” on Earth? (Sampleanswer: There are many speciesto consider and incomplete infor-mation. Some parts of Earth’s his-tory lack a fossil record becausefossils are formed only rarely.)

AlternativeAssessment ---------------------------aWriting Panda Pedigrees

Scientists study animalskeletons and DNA to

determine evolutionary relation-ships and development becausemerely looking at the outwardappearance of a species can bemisleading. The giant panda andred panda illustrate this prob-lem. The two pandas seem simi-lar, but scientists now believethat the red panda is moreclosely related to raccoons thanto the giant panda. Have stu-dents study these two types ofpandas and write a report basedon recent studies on the classifi-cation of the pandas.l Verbal/Logical



For a variety of links related to thischapter, go to www.scilinks.org

SummarySummary

Review

•• Evolution is the process in which inheritedcharacteristics within a population changeover generations, sometimes giving rise tonew species. Scientists continue to developtheories to explain how evolution happens.

•• Evidence that organisms evolve can befound by comparing living organisms toeach other and to the fossil record. Suchcomparisons provide evidence of commonancestry.

•• Scientists think that modern whalesevolved from an ancient, land-dwellingmammal ancestor. Fossil organisms thatsupport this hypothesis have been found.

•• Evidence of common ancestry among liv-ing organisms is provided by comparingDNA and inherited traits. Species that havea common ancestor will have traits andDNA that are more similar to each otherthan to those of distantly related species.

Using Key Terms

Complete each of the following sentences bychoosing the correct term from the word bank.S7CS10.c

adaptation species fossil evolution

1. Members of the same can mate with oneanother to produce offspring.

2. A(n) helps an organism survive.

3. When populations change over time, hasoccurred.

Understanding Key Ideas

4. A human’s arm, a cat’s front leg, a dolphin’sfront flipper, and a bat’s wing

a. have similar kinds of bones.b. are used in similar ways.c. are very similar to insect wings and jellyfish

tentacles.d. have nothing in common.

5. How does the fossil record show that specieshave changed over time? S7L5.c

6. What evidence do fossils provide about theancestors of whales? S7L5.a, S7L5.c

Critical Thinking

7. Making Comparisons Other than theexamples provided in the text, how arewhales different from fishes?

8. Forming Hypotheses Is a person’s DNA likelyto be more similar to the DNA of his or her bio-logical parents or to the DNA of one of his orher cousins? Explain your answer. S7L5.a

Interpreting Graphics

9. The photograph below shows the layers ofsedimentary rock exposed during the construc-tion of a road. Imagine that a species thatlived 200 million years ago is found in layer b.Would the species’ ancestor, which lived250 million years ago, most likely be foundin layer a or in layer c? Explain your answer.S7L5.c

Topic: Species and Adaptation;Fossil Record

SciLinks code: HSM1433; HSM0615

a

b

c

Answers to Section Review

1. species S7CS10.c

2. adaptation S7CS10.c

3. evolution S7CS10.c

4. a5. Sample answer: Fossils of types

of organisms that no longer existare found. These fossils form asequence of change and adapta-tion of populations of organismsover time. S7L5.c

6. Sample answer: There are fossilsof four-legged land mammalsthat share some characteristicswith modern whales and otherhoofed mammals. Also, there isa sequence of fossil organismsthat have characteristics inbetween those of the ancientfossils and modern whales.S7L5.a, S7L5.c

7. Sample answer: Whales breatheair with lungs (not gills) andbreathe through a spout that islike a nasal passage. Whalesswim in an up-and-down “gallop-ing” motion, as otters do (notside to side as fish do).

8. Sample answer: A person’s DNAis likely to be most similar to thatof his or her biological parents,because the parents are mostclosely related to the personby birth. S7L5.a

9. layer c; That layer is underlayer b, so layer c was probablydeposited earlier than layer band is thus older. S7L5.c

CHAPTER RESOURCES


CRF • Section Quizg • Section Reviewg

• Vocabulary and Section Summaryg

Technology

Transparencies• L24 Comparing Skeletal Structures

h-----------------------------g

Writing Horse Evolution Report Have stu-dents research to find the four mainancestors of the horse known from

the fossil record. (Eohippus, Mesohippus,Merychippus, Pliohippus) Ask students tomake a poster that shows each ancestralhorse in order of appear ance and to writea paragraph about each one, explaining itsunique physical characteristics. Studentsshould conclude their reports with anexplanation of the origin of wild horsesin North America. l Verbal


READING STRATEGY

How Does Evolution Happen?Imagine that you are a scientist in the 1800s. Fossils of some very strange animals have been found. And some familiar fossils have been found where you would least expect them. How did seashells end up on the tops of mountains?

In the 1800s, geologists began to realize that the Earth is mucholder than anyone had previously thought. Evidence showedthat gradual processes had changed the Earth’s surface overmillions of years. Some scientists saw evidence of evolution inthe fossil record. However, no one had been able to explainhow evolution happens—until Charles Darwin.

Charles DarwinIn 1831, 21-year-old Charles Darwin, shown in Figure 1, gradu-ated from college. Like many young people just out of col-lege, Darwin didn’t know what he wanted to do with his life.His father wanted him to become a doctor, but seeing bloodmade Darwin sick. Although he eventually earned a degree intheology, Darwin was most interested in the study of plantsand animals.

So, Darwin signed on for a five-year voyage around theworld. He served as the naturalist—a scientist who studiesnature—on the British ship the HMS Beagle, similar to the shipin Figure 2. During the trip, Darwin made observations thathelped him form a theory about how evolution happens.

2

Figure 1 Charles Darwin wanted to understand the natural world.

Figure 2 Darwin sailed around the world on a ship similar to this one.

What You Will Learn

List four sources of Charles Darwin’sideas about evolution.Describe the four parts of Darwin’stheory of evolution by naturalselection.Relate genetics to evolution.

Vocabularytraitselective breedingnatural selection

Brainstorming The key idea of thissection is natural selection. Brainstormwords and phrases related to naturalselection.

GPS Review Guide

2

OverviewThis section introduces studentsto Charles Darwin and hisfamous life history. Students willlearn the observations and ideasthat helped Darwin formulatehis theory of natural selection.Finally, students will connectconcepts of genetics to explana-tions of evolution.

BellringerHave students respond to thefollowing prompt: “The follow-ing are characteristics thatalmost all humans have in com-mon: upright walking, hair, fin-gerprints, binocular vision, andspeech. List the advantages anddisadvantages of each character-istic.” (Accept all reasonableanswers.)

Discussion ----------------------------------gDinosaurs Ask students todescribe a dinosaur. Ask them toexplain why there are no dino-saurs alive today. Ask why theythink dinosaurs became extinct.(Sample answer: Dinosaurs werewell adapted to their environmentand lived over 150 million years onEarth. But a catastrophic eventchanged the environment fasterthan the dinosaurs could adapt, andthey became extinct.) l Verbal h-----------------------------g

PORTFOLIO

Poster Project Have studentsresearch the natural history and

current status of a specific sea turtle speciesto find examples for each of the four stepsof natural selection. Have them construct adisplay to present their findings. Requirethem to include information about the tur-tle’s reproductive habits, physical adapta-tions, and factors in its environment thataffect its success. l Verbal/Visual

CHAPTER RESOURCES



Technology


Workbooks


Math Skills for Science• Multiplying Whole Numbersb

GPS Review Guide


GPS ReviewGuide

Use these worksheets to helpstudents review standardsS7CS3.b, S7CS5.a, S7CS8.c,S7L3.c, S7L5, S7L5.a, S7L5.b

Darwin’s Excellent AdventureThe Beagle’s journey is charted in Figure 3. Along the way,Darwin collected thousands of plant and animal samples. Hekept careful notes of his observations. One interesting placethat the ship visited was the Galápagos Islands. These islandsare found 965 km (600 mi) west of Ecuador, a country inSouth America.

✓✓Reading Check Where are the Galápagos Islands?

Darwin’s FinchesDarwin noticed that the animals and plants on the GalápagosIslands were a lot like those in Ecuador. However, they werenot exactly the same. The finches of the Galápagos Islands, forexample, were a little different from the finches in Ecuador.And the finches on each island differed from the finches onthe other islands. As Figure 4 shows, the beak of each finchis adapted to the way the bird usually gets food.

Figure 3 The course of theHMS Beagle is shown by thered line. The journey beganand ended in England.

Some Finches of the Galápagos IslandsFigure 4

The warbler finch has a small,narrow beak that it uses to catchsmall insects. This beak workslike a pair of tweezers.

The cactus finch has a tough beakthat it uses for eating cactus partsand insects. This beak works like apair of needle-nose pliers.

The large ground finch has awide, strong beak that it uses tocrack open big, hard seeds. Thisbeak works like a nutcracker.

S7CS3.b Use the mean, median, and modeto analyze a set of scientifi c data.

S7CS5.a Observe and explain how parts can berelated to other parts in a system such as predator/prey relationships in a community/ecosystem.S7CS8.c As prevailing theories are challenged bynew information, scientifi c knowledge may change.S7L3.c Recognize that selective breeding canproduce plants or animals with desired traits.S7L5 Students will examine the evolution of livingorganisms through inherited characteristics thatpromote survival of organisms and the survival ofsuccessive generations of their offspring.S7L5.a Explain that physical characteristics oforganisms have changed over successive generations(e.g. Darwin’s fi nches and peppered moths ofManchester).S7L5.b Describe ways in which species on earthhave evolved due to natural selection.

Demonstration --------------gForm and Function Show stu-dents the following pieces ofclothing: a sneaker, dress pump,loafer, neck tie, scarf, anklet,knee sock, baseball cap, and skicap. Discuss ways that all ofthese items are related, and notewhich items are more closelyrelated than others. (Relateditems have similar functions.)Explain that scientists such asCharles Darwin study organismsby observing the similarities anddifferences between theorganisms. l Kinesthetic

CONNECTIONCONNECTION vvSocial Studies --------------------a

Writing Darwin’s Voyage Haveinterested studentsresearch in greater detail

Darwin’s voyage and similarlong-distance travel by explorersin the 1800s. Topics for reportsinclude the types of ships usedfor travel in that era, the kindsof food eaten by the explorers,and the sophistication and thor-oughness of maps inthe 1800s. l Verbal PORTFOLIO

CONNECTION toCONNECTION toGeography --------------------------------------------g

Galápagos While displaying aworld map or atlas, explain thefollowing: The Galápagos Islandsare officially part of the countryof Ecuador, although they are1,000 km west of the mainland.They are a group of 19 volcani-cally formed islands. Althoughthey have a land area of only8,000 km2, they are dispersedover almost 60,000 km2 of thePacific Ocean. Biologists nowknow that unique new speciesare likely to arise in such dis-persed areas. l Visual/Logical


965 km (600 mi) west of mainlandEcuador

SUPPORT FOR

English Language LearnersNatural Selection To reinforce the con-cept of natural selection and give studentsa chance to connect it to prior knowledge,ask students to choose an animal fromtheir fi rst country that is not found in theUnited States. Have them research the ani-mal and answer the following questionswith a brief written summary. Evaluatethe summary on the language usage, clar-ity, and completeness of the answers.

• What is the animal’s name in English?• What does it look like?• What does it eat?• Where in your fi rst country does it live?

What is the land and weather like there?• Think about all the answers above. Then

say why you think the animal lives inyour fi rst country and not in the UnitedStates.l Verbal

Section 2 • How Does Evolution Happen? 175

Darwin’s ThinkingAfter returning to England, Darwin puzzled over the animalsof the Galápagos Islands. He tried to explain why the animalsseemed so similar to each other yet had so many differentadaptations. For example, Darwin hypothesized that the islandfinches were descended from South American finches. The firstfinches on the islands may have been blown from South Amer-ica by a storm. Over many generations, the finches may haveevolved adaptations for the various island environments.

During his travels, Darwin came up with many new ideas.Before sharing his ideas, he spent several years analyzing hisevidence and gathering ideas from other people.

What hypothesis did Darwin propose to explain

why the island finches were alike? For why they were different? S7L5.a

Ideas About BreedingIn Darwin’s time, farmers and breeders had produced manykinds of farm animals and plants. These plants and animalshad traits that were desired by the farmers and breeders. Atraittrait is a characteristic that can be passed from parent to off-spring through genes. The process in which humans selectwhich plants or animals to reproduce based on certain desiredtraits is called selective breeding.selective breeding. Most pets, such as the dogsin Figure 5, have been bred for various desired traits.

You can see the results of selective breeding in many kindsof organisms. For example, people have bred horses that areparticularly fast or strong. And farmers have bred crops thatproduce large fruit or that grow in specific climates.

traittrait a genetically determinedcharacteristic

selective breedingselective breeding the humanpractice of breeding animals orplants that have certain desiredtraits

Figure 5 Over the past 12,000 years,dogs have been selectively bred toproduce more than 150 breeds.

READINGSTRATEGY -----------------g

Prediction Guide Before stu-dents read this page, have themanswer the following questions:

• Why did the finches Darwinsaw on the Galápagos Islandslook similar to those he sawin South America?

• Why did they look a little different?

Have students share and evalu-ate their answers with a partnerafter they read the page.l Verbal/Intrapersonal

h-----------------------------a

Writing Island BiogeographyReport Biogeographyis the study of where

animals and plants are foundand how they came to live intheir particu lar location. Bio-geography uses informationfrom the fossil record and inte-grates ideas from biology, geol-ogy, paleontology, and chem-istry. Encourage interestedstudents to write a reportabout island biogeography.Have them include informationabout how biogeography is usedto design and manage terrestrialwildlife refuges.l Verbal/Intrapersonal PORTFOLIO


Darwin hypothesized that the islandfinches were alike because theydescended from the same ancestor.Darwin hypothesized that the islandfinches were different because theyhad evolved adaptations for theirenvironments. S7L5.a

CONNECTIONCONNECTION vvGeography ---------------------------------------------g

Bird Barrier Locate the Rocky Mountainson a map. Explain to students that bird-identification guides for North Americausually classify birds into two groups: birdsthat are east of the Rocky Mountains andbirds that are west of the Rocky Mountains.Brainstorm why ornithologists might usethis system. (Sample answer: because theRockies form a large geo graphical barrier)l Visual/Logical

Is That a Fact!As a result of selective breeding, thesmallest horse is the Falabella, which isonly about 76 cm tall. The largest is theShire, originally bred in England. TheShire can grow to more than 1.73 mhigh at the shoulder and weigh as muchas 910 kg.


Malthus’s Descriptionof Unlimited Population Growth

Qua

ntit

y

Time

Humanpopulation

Foodsupply

Ideas About PopulationDuring Darwin’s time, Thomas Malthus wrote afamous book entitled An Essay on the Principle ofPopulation. Malthus noted that humans have thepotential to reproduce rapidly. He warned that foodsupplies could not support unlimited populationgrowth. Figure 6 illustrates this relationship. How-ever, Malthus pointed out that human populationsare limited by choices that humans make or byproblems such as starvation and disease.

After reading Malthus’s work, Darwin realizedthat any species can produce many offspring. Healso knew that the populations of all species arelimited by starvation, disease, competition, andpredation. Only a limited number of individualssurvive to reproduce. Thus, there is somethingspecial about the survivors. Darwin reasoned thatthe offspring of the survivors inherit traits thathelp the offspring survive in their environment.

Ideas About Earth’s HistoryDarwin had begun to think that species could evolve over time.But most geologists at the time did not think that Earth wasold enough to allow for slow changes. Darwin learned newideas from Principles of Geology, a book by Charles Lyell. Thisbook presented evidence that Earth had formed by naturalprocesses over a long period of time. It became clear to Darwinthat Earth was much older than anyone had imagined.

What did Darwin learn from Charles Lyell?

S7CS8.c

Figure 6 Malthus thought that the humanpopulation could increase more quickly thanthe food supply, with the result that therewould not be enough food for everyone.

Population Growth Versus Food Supply1. Get an egg carton and a bag of rice. Use a

marker to label one row of the carton “Foodsupply.” Then, label the second row “Humanpopulation.”

2. In the row labeled “Food supply,” place onegrain of rice in the first cup. Place two grains ofrice in the second cup, and place three grainsof rice in the third cup. In each subsequent cup,place one more grain than you placed in theprevious cup. Imagine that each grain repre-sents enough food for one person’s lifetime.

3. In the row labeled “Human population,” placeone grain of rice in the first cup. Place twograins in the second cup, and place four grainsin the third cup. In each subsequent cup, placetwice as many grains as you placed in the previ-ous cup. This rice represents people.

4. How many units of food are in the sixth cup?How many “people” are in the sixth cup? If thispattern continued, what would happen?

5. Describe how the patterns in the food supplyand in the human population differ. Explainhow the patterns relate to Malthus’s hypothesis.

S7CS5.a

M A T E R I A L SFOR EACH STUDENT

• egg carton, 12-egg size, empty (2)• marker• rice (about 1 cup) (or lentils or small pebbles)

Answers

4. There are 32 “people” and 6units of “food.” If this patterncontinued, there would be alot more people than foodand not enough food to keepthe people alive.

5. The human population isgrowing much faster thanthe food supply is. This growthpattern is similar to that inMalthus’s prediction.

• Edit or print any lab• Download additional, leveled labs from my.hrw.com

Using the Figure -----a

Two Kinds of Growth Havestudents examine Figure 6. Askstudents to describe the behav-ior of the graph for food supply.(It rises steadily in a straight line.)Explain that the line represent-ing food supply indicates lineargrowth in which food supplyincreases by the addtion of agiven amount of food in eachtime interval. Next, ask studentsto describe the behavior of thegraph for human population.(It rises quickly in a curved line.)Explain that the line represent-ing human population indicatesexponential growth, in whichhuman population increasesby multiplication by a givenpercentage in each time interval.Ask students to suggest alterna-tive titles for this graph. (Sampleanswer: “Human Population GrowthVs. Food Supply”) l Visual/Logical

Is That a Fact!The full title of Malthus’s famousessay was “An Essay on the Principleof Population, as it Affects the FutureImprovement of Society with Remarkson the Speculations of Mr. Godwin,M. Condorcet, and Other Writers.”

Malthus’s work was important ininfluencing ecological scientists andprompting social planners to considerthe potential problems of rapid popu-lation growth. However, Malthus waswrong in his projections of the growthof food supplies. The use of machinery,fossil fuels, and chemicals since his timeenabled food production to increasemore rapidly than Malthus thoughtpossible.



that Earth had been formed bynatural proc esses over a longperiod of time S7CS8.c

1 2

43

Darwin’s Theory of Natural SelectionAfter his voyage on the HMS Beagle, Darwin privately strug-gled with his ideas for about 20 years. Then, in 1858, Darwinreceived a letter from a fellow naturalist named Alfred RusselWallace. Wallace had arrived at the same ideas about evolutionthat Darwin had. In 1859, Darwin published a famous bookcalled On the Origin of Species by Means of Natural Selection. Inhis book, Darwin proposed the theory that evolution happensthrough natural selection. Natural selection is the process bywhich organisms that are better adapted to their environmentsurvive and reproduce more successfully than less well adaptedorganisms do. The process has four parts and is explained inFigure 7.

What is natural selection? S7CS10.c, S7L5.b

natural selectionnatural selection the processby which individuals that are betteradapted to their environment surviveand reproduce more successfullythan less well adapted individualsdo; a theory to explain the mecha-nism of evolution

Four Parts of Natural SelectionFigure 7

Successful Reproduction The tarantulas thatare best adapted to their environment are likelyto have many offspring that survive.

Overproduction A tarantula’s egg sac may hold500–1,000 eggs. Some of the eggs will surviveand develop into adult spiders. Some will not.

Struggle to Survive Some tarantulas may becaught by predators, such as this wasp. Othertarantulas may starve or get a disease. Onlysome of the tarantulas will survive to adulthood.

Inherited Variation Every individual has itsown combination of traits. Each tarantula issimilar to, but not identical to, its parents.

vv-----------------------------------------------------b

Natural Selection Have students carefullystudy Figure 7 and begin to create theirown table, concept map, or other graphicorganizer about the four parts of naturalselection. For each part of the figure, call onseveral students to restate the meaning intheir own words, and then ask students towrite their own version of the explanationon their graphic organizer. Finally, for eachpart, ask students to describe an additionalexample of the same process with anotherorganism besides a tarantula. l Visual

Reteaching -------------------------------------bWriting Terms Have students

list the key terms andany unfamiliar terms

from this chapter. For each term,they should write a definitionand then write sample sentencesusing the term. l Verbal

Quiz --------------------------------------------------------------------g

1. Who was Charles Lyell?(He was a British geologist.)

2. What did Darwin learn fromLyell’s data about the age ofEarth? (Darwin learned fromLyell that Earth was old enoughfor slow changes to happen ina population.)

AlternativeAssessment ---------------------------aWriting Darwin’s Journal

Charles Darwin’s journalscontain notes and records

from his travels. Ask students toimagine that they are travelingwith Darwin and keeping theirown journals. Their notes anddrawings should reflect whatthey see, what questions arisefrom their observations, andwhat hypotheses that they form.Encourage students to writejournal entries about animals onthe Galápagos Islands otherthan the finches, such as theGalápagos tortoise and marineiguanas. l Verbal/Intrapersonal


Natural selection is the process bywhich organisms that are betteradapted to their environment sur-vive and reproduce more success-fully than less well adaptedorganisms do. S7CS10.c, S7L5.b

In 1809, French naturalist Jean BaptisteLamarck’s theory of evolution byacquired characteristics stated that ifan animal changed a body part throughuse or nonuse, that change would beinherited by its offspring. For example,larger leg muscles as a result of exten-sive running would be passed on to thenext generation. However, genetic stud-ies in the 1930s and 1940s disprovedthis mechanism for inheriting traits.




SummarySummary

Review

Genetics and EvolutionDarwin lacked evidence for parts of his theory. For example,he knew that organisms inherit traits, but not how they inherittraits. He knew that there is great variation among organisms,but not how that variation occurs. Today, scientists have foundmost of the evidence that Darwin lacked. They know thatvariation happens as a result of differences in genes. Changesin genes may happen whenever organisms produce offspring.Some genes make an organism more likely to survive to repro-duce. The process called selection happens when only organismsthat carry these genes can survive to reproduce. New fossildiscoveries and new information about genes add to scientists’understanding of natural selection and evolution.

•• Darwin explained thatevolution occurs throughnatural selection. Histheory has four parts:1. Each species pro-

duces more offspringthan will survive toreproduce.

2. Individuals withina population haveslightly different traits.

3. Individuals within apopulation competewith each other forlimited resources.

4. Individuals that arebetter equipped tolive in an environmentare more likely to sur-vive to reproduce.

•• Modern genetics helpsexplain the theory ofnatural selection.

Using Key Terms

1. In your own words, write adefinition for the term trait.S7CS10.c

2. Use the following terms in thesame sentence: selective breedingand natural selection. S7CS10.d


3. Modern scientific explanationsof evolution S7L5

a. have replaced Darwin’s theory.b. rely on genetics instead of

natural selection.c. fail to explain how traits are

inherited.d. combine the principles of

natural selection and geneticinheritance.

4. Describe the observations thatDarwin made about the specieson the Galápagos Islands. S7L5.a

5. Summarize the ideas that Darwindeveloped from books by Malthusand Lyell. S7CS8.c

6. Describe the four parts ofDarwin’s theory of evolutionby natural selection. S7L5.b

7. What knowledge did Darwinlack that modern scientists nowuse to explain evolution?

Math Skills

8. In a sample of 80 beetles,50 beetles had 4 spots each,and the rest had 6 spots each.What was the average numberof spots per beetle? S7CS3.b,

M7D1.c

Critical Thinking

9. Making Comparisons In selec-tive breeding, humans influencethe course of evolution. Whatdetermines the course of evolu-tion in natural selection? S7L5

10. Predicting ConsequencesSuppose that an island in thePacific Ocean was just formed bya volcano. Over the next millionyears, how might species evolveon this island? S7L5.a, S7L5.b

Topic: Galápagos Islands;Darwin and Natural Selection

SciLinks code: HSM0631; HSM0378


1. Sample answer: A trait is aform of an inherited character-istic. S7CS10.c

2. Sample answer: Selectivebreeding happens when humanschoose which organisms willreproduce, and natural selectionhappens when the environment“chooses.” S7CS10.d

3. d S7L5

4. Darwin observed that manyof the species of the GalápagosIslands were similar to those ofSouth America but had uniqueadaptations. S7L5.a

5. From Malthus, Darwin de-veloped the idea that popula-tions are limited by food andother problems. From Lyell,Darwin developed tha idea thatconditions on Earth couldchange slowly over longperiods of time. S7CS8.c

6. Sample answer: Over-production means that everyorganism can produce moreoffspring than will likely survive;inherited variation means thatall offspring will have some dif-ferences; struggle to survivemeans the offspring have tocompete with each other andwith other organisms aroundthem; and successful reproduc-tion means those that are bestadapted will probably havemore offpsring like themselves.S7L5.b

7. Sample answer: Darwin lackedthe knowledge of genetics thathelps explain how organismsinherit traits and why there isso much variety in organisms.

8. {(50�4) � [(80�50) � 6]} � 80 � 4.75 spots average perbeetle S7CS3.b, M7D1.c

9. Sample answer: natural forcesand other organisms S7L5

10.Sample answer: Species on theisland might evolve in a waysimilar to those of the GalápagosIslands. S7L5.a, S7L5.b

oRate Debate Evolutionary scientistsdo not yet agree on how often newspecies arise. Gradualism, the theorythat Darwin supported, holds thatchanges in species occur slowly andsteadily over thousands of years. Inthe 1970s, Stephen Jay Gould and oth-ers proposed the theory of punctuatedequilib rium, which holds that speciescan remain unchanged for millions ofyears until dramatic environmentalchanges prompt speciation.

CHAPTER RESOURCES



• Vocabulary and Section Summaryg • Reinforcement Worksheetb • SciLinks Activityg

• Datasheet for Quick Lab

Technology

Transparencies• L25 Four Parts of Natural Selection


READING STRATEGY

Natural Selection in ActionHave you ever had to take an antibiotic? Antibiotics aresupposed to kill bacteria. But sometimes, bacteria are notkilled by the medicine. Do you know why?

A population of bacteria might develop an adaptation throughnatural selection. Most bacteria are killed by the chemicals inantibiotics. But a few of the bacteria have an adaptation thatmakes them naturally resistant to, or not killed by, the antibi-otic. These few bacteria survive antibiotic treatment, continueto reproduce, and pass the adaptation to their offspring. Afterseveral generations, almost all the bacteria in the populationcarry the adaptation of antibiotic resistance.

Changes in PopulationsThe theory of natural selection explains how a populationchanges in response to its environment. Through ongoingnatural selection, a population adapts to its environment.Well-adapted individuals will likely survive and reproduce.

Adaptation to HuntingChanges in populations are sometimes observed when a newforce affects the survival of individuals. Scientists think thathunting in Uganda is affecting Uganda’s elephant population.In 1930, about 99% of the male elephants in one area hadtusks. Only 1% of the elephants were born without tusks.Today, as many as 15% of the male elephants in that arealack tusks. What happened?

A male African elephant that has tusks isshown in Figure 1. The ivory of an elephant’stusks is very valuable. People hunt theelephants for their tusks. As a result, fewerof the elephants that have tusks survive toreproduce, and more of the tuskless elephantssurvive. When the tuskless elephants reproduce,they pass the tuskless trait to their offspring.

3

Figure 1 The ivory tusks of Africanelephants are very valuable. Someelephants are born without tusks.

What You Will Learn

Give three examples of natural selection in action.Outline the process of speciation.

Vocabularygeneration timespeciation

Prediction Guide Before readingthis section, write the title of eachheading in this section. Next, undereach heading, write what you thinkyou will learn.

S7CS3.a Analyze scientifi c data by using,interpreting, and comparing numbers in

several equivalent forms, such as integers, fractions,decimals, and percents.S7L5 Students will examine the evolution of livingorganisms through inherited characteristics thatpromote survival of organisms and the survival ofsuccessive generations of their offspring.S7L5.b Describe ways in which species on earthhave evolved due to natural selection.

GPS Review Guide

3

OverviewIn this section, students will seeexamples of natural selection atwork. They will relate a species’generation time to its ability toadapt. Students will also exam-ine the process of speciation.

BellringerHave students respond to thefollowing prompt: “Write thefour parts of natural selection,and create a mnemonic deviceto remember each part by usingthe first letter of the words.”(Sample answer: Overproduction,genetic Variation, Struggle to sur-vive, successful Reproduction;Olga’s Vacation Seemed Relaxing.)

Debate--------------------------------------------------------gPeople and Nature During thepast several hundred years, arapidly expanding human popu-lation has caused some speciesto become extinct either fromhabitat destruction or overhunt-ing. Have students takes sidesand debate the following issue:If people are as much a part ofthe environment as trees andbirds are, are people’s actionsjust parts of natural processes?l Verbal/Intrapersonal

MISCONCEPTIONALERT

Tuskless Elephants It is important tounderstand that there were always sometuskless elephants in the wild popula-tions. These animals were naturallytuskless—they were born without tusksand never developed tusks. Because thetuskless elephants are not hunted, theyare more likely to pass their traits tofuture generations.

CHAPTER RESOURCES



Technology


Workbooks


GPS Review Guide


GPS ReviewGuide

Use these worksheets to helpstudents review standardsS7CS3.a, S7L5, S7L5.b

Insecticide ResistanceTo control insect pests, many people use insecticides, chemicalsthat kill insects. Sometimes, an insecticide that used to workwell no longer affects an insect population. The reason is thata few insects in the population are resistant to the chemical.These insects survive insecticide treatment and pass the resis-tance trait to their offspring. Figure 2 shows how an insectpopulation becomes resistant to some insecticides.

Insect populations can evolve quickly because insectsproduce many offspring and have a short generation time.Generation time is the average time between one generationand the next.

Why do insects quickly develop resistance to

insecticides? S7L5

Competition for MatesFor organisms that reproduce sexually, competition for matescan select for adaptations. For example, in many bird species,females prefer to mate with colorful males. So, colorful maleshave more offspring than noncolorful males do. Because col-orful males are more likely to pass on their genes to the nextgeneration, the proportion of colorful males is likely to increasefrom generation to generation.

generation timegeneration time the periodbetween the birth of one generationand the birth of the next generation

Natural Selection of Insecticide ResistanceFigure 2

An insecticide willkill most insects,but a few maysurvive. Thesesurvivors havegenes that makethem resistant tothe insecticide.

1

3 In time, thereplacementpopulation ofinsects is madeup mostly ofindividualsthat have theinsecticide-resistance genes.

2 The survivors thenreproduce, passingthe insecticide-resistance genesto their offspring.

4 When the samekind of insecti cideis used on theinsects, only a feware killed becausemost of them areresistant to thatinsecticide.

CONNECTIONCONNECTION vvReal World----------------------------------------------g

Natural Pest Control Theuse of natural predators againstinsect pests can provide an alter-native to chemical insecticides.Ladybugs, for example, whichare actually beetles, are used tocombat infestations of aphids,whiteflies, fruitworms, mites,broccoli worms, and tomatohornworms. Ladybugs can bepurchased in large numbers andreleased on crops. Many speciesof bats are voracious hunters ofmosquitoes and other smallinsects. Bat houses are becomingincreasingly popular. Encouragestudents to research methodsfor encouraging ladybugs, bats,and other insect predators.l Kinesthetic/Intrapersonal ee


because they often produce manyoffspring and have short generationtimes S7L5

GroupGroup vv -------a

Amazing Adaptations Havegroups of students collaborateto create depictions of hypo-thetical organisms that haveinteresting adaptations forbizarre imaginary environments,conditions, or other planets.Students should create cap-tions to explain each organism’sunique traits. As an alternative,have students research and makeposters about interesting culturalpractices of people who live inextreme environments suchas the Arctic or a desert.l Visual/Kinestheticcc

ee

INTERNETINTERNET vvEssay -------------------------------------------------------------------------g

For an internet activity related to thischapter, have students go to go.hrw.comand type in the keyword HL5EVOW.

SUPPORT FOR

English Language LearnersExpanding Vocabulary As studentsread this section they will encountermany unfamiliar words. Remind themto use the context to fi nd the mean-ing and write it and the word in theirscience journals. When students havefi nished reading, have them confi rmtheir guesses with a dictionary. Theyshould copy correct defi nitions from adictionary as needed to complete thelist. Diffi cult words may include: adapta-tion, result, resistance, insecticide, mate (asa verb).l Verbal Section 3 • Natural Selection in Action 181

Forming a New SpeciesSometimes, drastic changes that can form a new species takeplace. In the animal kingdom, a species is a group of organismsthat can mate with each other to produce fertile offspring. Anew species may form after a group becomes separated fromthe original population. This group forms a new population.Over time, the new population adapts to its new environment.Eventually, the new population and the original populationdiffer so greatly that they can no longer mate successfully. Thenew population may then be considered a new species. Theformation of a new species as a result of evolution is calledspeciationspeciation (SPEE shee AY shuhn). Figure 3 shows how new spe-cies of Galápagos finches may have formed. Speciation mayhappen in other ways as well.

SeparationSpeciation often begins when a part of a population becomesseparated from the rest. The process of separation can happen inseveral ways. For example, a newly formed canyon, mountainrange, or lake can divide the members of a population.

✓✓ Reading Check How can parts of a population become separated?

Some finches left the mainland and reached one of the islands (separation).

The finches reproduced and adapted to the environment (adaptation).

Some finches flew to a second island (separation).

The finches reproduced and adapted to the different envi-ronment (adaptation).

Some finches flew back to the first island but could no longer interbreed with the finches there (division).

This process may have occurred over and over again as the finches flew to the other islands.

speciationspeciation the formation of new species as a result of evolution

The Evolution of Galápagos Finch SpeciesFigure 3

1 2 3

4 5 6

Reteaching -------------------------------------bSelection Have students place20 black beans and 20 red beanson a piece of black paper. Callthe display Generation 1. Tellstudents that the beans are fishand ask which would most likelybe eaten first by the bean shark.Then tell them to add 5 blackbeans and take away 5 red ones.Call this Generation 2. Havestudents predict and modelGeneration 3. l Visual

Quiz ---------------------------------------------------------------------g

Concept Mapping Construct aconcept map that shows how apopulation of mosquitoes candevelop resistance to a pesticide.

AlternativeAssessment ---------------------------a

PORTFOLIO

Species Report Haveeach student research

and give an oral presentationon how the three steps of specia-tion (separation, adaptation,and division) worked in provid-ing a particular animal with adistinctive feature. Species of theGalapágos Islands are goodexamples. l Verbal


Sample answer: A newly formedcanyon, mountain range, or lakecould separate the members of apopulation.

2. Genetic variation: Spread the rabbitson your desk. Notice the colors.

3. Struggle to survive: For 1 min, try totake rabbits from each other. Yoursare “safe” if you are touching them.

4. Successful reproduction: Look at yoursurviving rabbits. Suppose only thosethat have an X will reproduce.

As a class, tally and discuss the results.l Visualcc

ee


• Learning Disabled• Attention Deficit Disorder• Behavior Control IssuesGuide students through a simulation.Trace nine rabbit outlines on a singlepage, and place an X on five of them.For each student, make one copy oneach of three colors of paper. Have eachstudent label his or her rabbits. Promptstudents through the following stages:

1. Overproduction: Cut out the rabbits.




Leopard frogTree frog

Pickerel frogBullfrog

March 1 April 1 May 1 June 1 July 1

Mat

ing

beha

vior

Month

Mating Times

SummarySummary

Review

AdaptationPopulations constantly undergo natural selection.After two groups have separated, natural selec-tion may act on each group in different ways.Over many generations, the separated groups mayevolve different sets of traits. If the environmentalconditions for each group differ, the adaptationsin the groups will also differ.

DivisionOver many generations, two separated groups ofa population may become very different. Even ifa geographical barrier is removed, the groups maynot be able to interbreed anymore. At this point,the two groups are no longer the same species.

Figure 4 shows another way that populationsmay stop interbreeding. Leopard frogs and pick-erel frogs probably had the same ancestor species.Then, at some point, some of these frogs beganto mate at different times during the year.

•• Natural selectionexplains how popula-tions adapt to changesin their environment. Avariety of examples ofsuch adaptations canbe found.

•• Natural selection alsoexplains how one spe-cies may evolve intoanother. Speciationoccurs as populationsundergo separation,adaptation, and division.

Using Key Terms

1. In your own words, write adefinition for the term speciation.S7CS10.c


2. Two populations have evolvedinto two species when S7L5.b

a. the populations are separated.b. the populations look different.c. the populations can no longer

interbreed.d. the populations adapt.

3. Explain why the number oftuskless elephants in Ugandamay be increasing. S7L5

Math Skills

4. A female cockroach can produce80 offspring at a time. If half ofthe offspring produced by a cer-tain female are female and eachfemale produces 80 offspring,how many cockroaches are therein the third generation? S7CS3.a,

M7P1.b

Critical Thinking

5. Forming Hypotheses Mostkinds of cactus have leaves thatgrow in the form of spines. Thestems or trunks become thick,juicy pads or barrels. Explainhow these cactus parts mighthave evolved. S7L5.b

6. Making Comparisons Sug-gest an organism other thanan insect that might evolve anadaptation to human activities.S7L5.b

Topic: Species and AdaptationSciLinks code: HSM1433

Figure 4 The leopard frog and the pickerelfrog are similar species. However, leopardfrogs do not search for mates at the sametime of year that pickerel frogs do.


1. Sample answer: Speciation isone species evolving into two.S7CS10.c

2. c S7L5.b

3. Sample answer: The number oftuskless elephants is increasingbecause hunters are killing offthe elephants with tusks beforethey can breed. S7L5

4. 128,000 cockroachesCalculations:First generation: 80 cockroachesSecond generation: (80 � 2) � 80 �

3,200 cockroachesThird generation: (3,200 � 2) � 80 � 128,000 cockroachesS7CS3.a, M7P1.b

5. Sample answer: Cactusesevolved from plants that hadadaptations to dry conditions,such as spiny leavers that keepanimals from eating the plant orthick stems that store water.S7L5.b

6. Sample answer: Rodents mightadapt to eating our garbage.S7L5.b

CHAPTER RESOURCES



• Vocabulary and Section Summaryg • Critical Thinkinga

Technology

Transparencies• L26 Evolution of the Galápagos Finches

Is That a Fact!Some species that have adapted to livein total darkness no longer even haveeyes! Just as whales have evolved intolegless forms, these species have com-pletely adapted to life without light,and some have evolved forms lackingeyes altogether. There are blind cavefish, eels, salamanders, worms, shrimp,crayfish, spiders, beetles, and crickets.

Section 3 • Natural Selection in Action 183

Exploring Habits of Mind

Understanding Accuracyand PrecisionThe common meanings of the words accuracy and precisionare almost the same. However, the scientific meanings ofthese terms differ.

Tutorial

1 Defining Accuracy Accuracy describes how close an estimatedmeasurement is to the true value. In other words, accuracy has todo with the correctness of a measurement.

2 Defining Precision Precision is the exactness with which ameasurement is made and reported. Precision depends on thesensitivity of the measuring tool. In other words, precision describeswhether a measurement is more approximate or more exact.

3 Applying Accuracy and Precision The tool that you use to collectdata affects the accuracy and precision of your measurements.Look at the rulers shown on the left. If the rulers were manufac-tured correctly, you can use either ruler to make an accuratemeasurement. But notice that the red ruler has a mark at eachmillimeter and that the blue ruler has a mark at each centimeter.The red ruler is a more-sensitive measuring tool than the blueruler is. So, you can use the red ruler to make more-precisemeasurements. You can use the red ruler to estimate the lengthto one more place value than you can if you use the blue ruler,as the table shows.

Ruler Length (cm) Length (mm)Blue 6.3 63

Red 6.26 62.6

4 Evaluating Accuracy and Precision Suppose the bone indicatedon the left is 6.264 cm long. The following measurements areexamples of the ways in which some different measurementscan be described in terms of accuracy and precision:

A measurement of 6.26 cm is both accurate and precise.A measurement of 6 cm is accurate but not precise.A measurement of 7.39 cm is not accurate, but it is precise.A measurement of 7 cm is neither accurate nor precise.

S7CS3.f Address the relationshipbetween accuracy and precision and

the importance of each.

Science Skills ActivityTeacher’s NotesIn this activity, students willaddress the relationship betweenaccuracy and precision in mea-surements (covers standardS7CS3.f).


183A Chapter 7 • The Evolution of Living Things

on the board. Ask students to tell you whichmeasurements were accurate and why themeasurements were accurate. (The taredbalance made accurate measurements; theother measurements included the mass of thecup.) Ask students to compare the precisionof the measurements made by each balance.(The precision of the measurements made byeach balance was the same.) Ask studentshow they would improve the accuracy ofthe results. (Sample answer: Remember totare both balances.) l Visual/Logical


• Developmentally DelayedA demonstration can help students under-stand how scientists can obtain data thathave the same precision but different accu-racy. Set up two balances. Place a paper cupon each balance. Tare one balance, but“forget” to tare the other one. Then, placea washer in each cup, and record the massof each washer. Repeat the process twicemore, adding the same type of washer toeach cup, and recording the resulting masses.Write the three results from each balance

ReadingEnhancementUse the Internet or booksfrom your library to findexamples of both a scientificuse and an everyday use ofthe words accuracy andprecision. In your sciencejournal, write a short reportexplaining the meanings ofthe words accuracy andprecision in the examplesthat you find. S7CS10.d

To improve yourreading skills, go

to the Reading Workshopsection of the Appendix.

You Try It!Scientists who study the evolution of living organisms often needto measure them. Beak size, leg length, body mass, and many othermeasurable characteristics can tell scientists how organisms function.Sometimes, this information can also demonstrate how organismsare related to one another.

Two scientists are studying a ruby-throated hummingbird(Archilochus colubris). They each measure the hummingbird fourtimes. Each time, the actual mass of the hummingbird is 3.302 g, andthe actual body length is 8.749 cm. Review their data below, andanswer the following questions.

Scientist A Scientist B

Trial Mass (g) Bodylength (cm) Trial Mass (g) Body

length (cm)

1 3.3 8.8 1 3.30 8.32

2 3.3 8.7 2 3.29 8.17

3 3.3 8.7 3 3.31 8.76

4 3.3 8.8 4 3.30 7.99

1 Evaluating Accuracy Look at the mass measurements that eachscientist recorded. Are the data that one scientist recorded moreaccurate than the data that the other scientist recorded? Explainyour answer.

2 Evaluating Accuracy Look at the body length measurements thateach scientist recorded. Are the data that one scientist recordedmore accurate than the data that the other scientist recorded?Explain your answer.

3 Evaluating Precision Which scientist’s data are more precise? Whatdoes precision tell you about the tools that each scientist is using?

4 Making Inferences Why are accuracy and precision important inscientific investigations?

5 Selecting Tools For each of the following examples, list two toolsthat can be used to make the measurement. Indicate which toolis more precise.

a. the length of time to read a sentenceb. the mass of a textbookc. the volume of liquid in a glassd. the length of a pencil

6 Enhancing Experiments Suggest one way to improve accuracy ofdata. Suggest one way to improve precision of data.

Answers to You Try It!

1. The data of both scientists areequally accurate. The actual valueis very close to the measurementsthat each scientist found.

2. The body length data that scientist Arecorded are more accurate thanthe body length data that scientist Brecorded. Scientist A’s body lengthmeasurements are closer to theactual value than scientist B’s bodylength measurements are.

3. Scientist B’s data are more pre-cise than scientist A’s data.Scientist B is using more-sensitivemeasuring tools than scientist A is.

4. Answers may vary.5. Sample answer: a. a stopwatch

that has a second hand and a wallclock that has no second hand;stopwatchb. a bathroom scale that has kilogramincrements and a balance thathas gram increments; balancec. a graduated cylinder that hasmilliliter graduations and a beakerthat has 10 milliliter graduations;graduated cylinderd. a ruler showing centimetersand a ruler showing millimeters;ruler showing millimeters

6. Sample answer: Accuracy canbe improved by reducing humanerror. Precision can be improvedby using more-sensitive measuringtools.

Chapter 7 • Science Skills Activity 183B

Survival of the ChocolatesImagine a world populated with candy, and hold that deliciousthought in your head for just a moment. Try to apply the ideaof natural selection to a population of candy-coated chocolates.According to the theory of natural selection, individuals whohave favorable adaptations are more likely to survive. In the“species” of candy-coated chocolates you will study in thisexperiment, the characteristics of individual chocolates mayhelp them “survive.” For example, shell strength (the strengthof the candy coating) could be an adaptive advantage. Plan anexperiment to find out which characteristics of the chocolatesare favorable “adaptations.”

Ask a Question

1 What might “survival” mean for a candy-coated chocolate?What are some ways you can test which chocolates are the“strongest” or “most fit” for their environment? Also, write downany other questions that you could ask about the “survival” ofthe chocolates.

Form a Hypothesis

2 Form a hypothesis, and make a prediction. For example, if youchose to study candy color, your prediction might be similar tothis: If the colored shell is the strongest, then fewer of thechocolates with this color of shell will when .

Form a hypothesis aboutthe fate of the candy-coatedchocolates.

Predict what will happen tothe candy-coated chocolates.

Design and conduct anexperiment to test yourhypothesis.

• chocolates, candy-coated,small, in a variety of colors(about 100)

• items to be determined bythe students and approvedby the teacher

OBJECTIVES

MATERIALS

SAFETY

OBJECTIVES

Using Scientifi c Methods

LabInquiryInquiry LabLab

Survival of theChocolates

Teacher’s Notes

Time RequiredOne or two 45-minute classperiods

Lab Ratings

rTeacher Prep f

Student Set-Up ff

Concept Level ff

Clean Up f

Safety CautionSafety concerns will vary witheach design.

Preparation NotesBe prepared for a variety ofexperimental designs. For exam-ple, students may wish to testwhich color will crack easiestunder physical stress or whichcolor will dissolve more quicklyin water. This lab is an oppor-tunity to reinforce scientificmethods and practice designingexperiments. Encourage studentsto brainstorm a variety of possi-ble hypotheses and ways oftesting the hypotheses. Havestudents identify scientificmethods in their experiments.


CHAPTER RESOURCES


CRF • Datasheet for Chapter Lab• Lab Notes and Answers

Technology

Classroom Videos • Lab Video

Karma Houston-Hughes

Kyrene Middle SchoolTempe, Arizona

CLASSROOM

TESTED& APPRO

VED


Test the Hypothesis

3 Design a procedure to determine which typeof candy-coated chocolate is most likelyto survive. In your plan, be sure to includematerials and tools you may need to completethis procedure.

4 Check your experimental design with yourteacher before you begin. Your teacher willsupply the candy and assist you in gatheringmaterials and tools.

5 Record your results in a data table. Be sure toorganize your data in a clear and understand-able way.

Analyze the Results

1 Describing Events Write a report thatdescribes your experiment. Be sure to includetables and graphs of the data you collected.

Draw Conclusions

2 Evaluating Data In your report, explain howyour data either support or do not supportyour hypothesis. Include possible errors andways to improve your procedure.

Applying Your DataCan you think of another characteristic of thechocolates that can be tested to determinewhich type is best adapted to survive? Explainyour idea, and describe how you might test it.

S7CS1.b Understand that hypotheses can be valuable,even if they turn out not to be completely accurate.

S7CS6.c Organize scientifi c information using appropriatesimple tables, charts, and graphs, and identify relationshipsthey reveal.

S7CS9 Students will investigate the features of the process ofscientifi c inquiry.

Lab Safety S7CS2.a, S7CS2.b, S7CS2.c, S7CS4.c

Form a Hypothesis

2. Answers may vary. The examplestatement is only an examplefor format. Students may wishto investigate a characteristicother than candy shell hardness.Help them make a predictionabout their own experiment.Check that all students haveformed testable hypotheses.

Test the Hypothesis

4. Answers may vary. Check thatstudents have planned a con-trolled experiment and that eachfactor is accounted for. Also,check that they have plannedfor all materials they will need.

5. Answers may vary. Studentsshould conduct their own experi-ment and record all procedures,observations, and results.Students should use data tablesto record results where appropriate.

Analyze the Results

1. Reports may vary but shoulddescribe all parts of the experi-ment and present the resultswith tables, diagrams, or graphsas appropriate.

Draw Conclusions

2. Reports may vary but shouldinclude a conclusion that thehypothesis was supported ornot. Check that student conclu-sions are directly related to thehypothesis and were logicallydrawn from the experimentalresults.

CHAPTER RESOURCESWorkbooks

Whiz-Bang Demonstrations• Adaptation Behooves Youg

Long-Term Projects & Research Ideas • Evolution’s Explosiona

Chapter 7 • Chapter Lab 185

USING KEY TERMS UNDERSTANDING KEY IDEAS

Complete each of the following sen-tences by choosing the correct termfrom the word bank. S7CS10.c

adaptationevolutiongeneration timespeciesspeciationfossil recordselective breedingnatural selection

1 When a single population evolves intotwo populations that cannot inter-breed anymore, has occurred.

2 Darwin’s theory of explained theprocess by which organisms becomewell-adapted to their environment.

3 A group of organisms that can matewith each other to produce offspringis known as a(n) .

4 The provides information aboutorganisms that have lived in the past.

5 In , humans select organisms withdesirable traits that will be passed fromone generation to another.

6 A(n) helps an organism survivebetter in its environment.

7 Populations of insects and bacteria canevolve quickly because they usuallyhave a short .

Multiple Choice

8 Fossils are commonly found in S7L5.c

a. sedimentary rock. b. all kinds of rock. c. granite. d. loose sand.

9 The fact that all organisms haveDNA as their genetic material isevidence that

a. all organisms undergo naturalselection.

b. all organisms may have descendedfrom a common ancestor.

c. selective breeding takes placeevery day.

d. genetic resistance rarely occurs.

0 Charles Darwin puzzled over differ-ences in the of the different speciesof Galápagos fi nches. S7L5.a

a. webbed feet b. beaks c. bone structure of the wings d. eye color

q Darwin observed variations amongindividuals within a population, buthe did not realize that these variationswere caused by S7L5.a, S7L5.b

a. interbreeding. b. differences in food. c. differences in genes. d. selective breeding.

12. Sample answer: Living organisms can becompared in terms of body structures withother living organisms and with organismsfrom the fossil record. Also, the DNA of living organisms can be compared. S7L5

ANSWERS

Using Key Terms 1. speciation S7CS10.c

2. natural selection S7CS10.c

3. species S7CS10.c

4. fossil record S7CS10.c

5. selective breeding S7CS10.c

6. adaptation S7CS10.c

7. generation time S7CS10.c

Understanding Key Ideas8. a S7L5.c

9. b10. b S7L5.a

11. c S7L5.a, S7L5.b

Assignment GuideSECTION QUESTIONS

1 2–4, 6, 8, 9, 12, 13, 21,22

2 5, 10, 11, 14, 15, 17, 23

3 1, 7, 16, 18, 19, 20


Perc

enta

ge o

f birt

hs

Infant Birthsby Birth Weight

Weight (lb)2 4 6 8 10

0

5

10

15

20

Prob

abili

ty o

f dea

th (

%)

Infant Deathsby Birth Weight

10

1

Weight (lb)2 4 6 8

100CRITICAL THINKING

INTERPRETING GRAPHICS

Short Answer

w Identify two ways that organisms canbe compared to provide evidence ofevolution from a common ancestor.S7L5

e Describe evidence that supports thehypothesis that whales evolved fromland-dwelling mammals. S7L5.a

r Why are some animals more likelyto survive to adulthood than otheranimals are? S7L5.b

t Explain how genetics is related toevolution. S7L5

y Outline an example of the processof speciation. S7L5.b

uConcept Mapping Use the followingterms to create a concept map: struggleto survive, theory, genetic variation,Darwin, overpopulation, natural selection,and successful reproduction. S7L5.b

iMaking Inferences How could natu-ral selection affect the songs thatbirds sing? S7L5.b

oForming Hypotheses In Australia,many animals look like mammalsfrom other parts of the world. Butmost of the mammals in Australia aremarsupials, which carry their young inpouches after birth. Few kinds of mar-supials are found anywhere else in theworld. What is a possible explanationfor the presence of so many of theseunique mammals in Australia? S7L5.b

pAnalyzing Relationships Geologistshave evidence that the continentswere once a single giant continent.This giant landform eventually splitapart, and the individual continentsmoved to their current positions.What role might this drifting of conti-nents have played in evolution? S7L5.b

The graphs below show informationabout the infants that are born and theinfants that have died in a population.The weight of each infant was measuredat birth. Use the graphs to answer thequestions that follow.

a What is the most common birthweight? S7CS6.b

s At which birth weight is an infantmost likely to survive? S7CS6.b

d How do the principles of natural selec-tion help explain why there are moredeaths among babies whose birthweights are low than among babieswhose birth weights are average? S7CS6.b,

S7L5.b

13. Sample answer: Whales share many inter-nal similarities with hoofed land mammals.Ancient fossils of four-legged land mam-mals exist from times when whales did notexist, but some of these fossils sharedcharacteristics with modern whales andother hoofed mammals. A sequence of fos-sil organisms shows how the characteris-tics of modern whales could have evolvedfrom those of ancient land mammals. S7L5.a

14. Sample answer: Those animalsthat are better adapted to theconditions of their environment,including the condition of com-petition with other organisms,are more likely to survive toadulthood. S7L5.b

15. Sample answer: Genetics pro-vides a tool with which to ana-lyze and explain what happensinside cells as organismsevolve. S7L5

16. Answers may vary. Studentanswers may resemble thedescription of the speciationof the Galápagos finches givenin the student text. S7L5.b

Critical Thinking17. An answer to this

exercise can befound at the endof this book. S7L5.b

18. Sample answer: A bird’s songcould be an advantage if thesong helps the bird find matesor food, but the song could bea disadvantage if it attracts predators. So, natural selectionwould mean that birds whosesongs were not an advantagemight not survive, and songswould evolve that gave birdssome kind of advantage. S7L5.b

19. Sample answer: Australia is anisland, so the marsupials therecould have evolved separatelyfrom other mammals aroundthe world. S7L5.b

20. Sample answer: As the conti-nents drifted apart, populationsof species would have beenseparated and may have hadto adapt to new environmentalconditions. The separated populations would likely haveevolved into separate speciesover time. S7L5.b

Interpreting Graphics21. about 7 lb S7CS6.b

22. about 7 lb S7CS6.b

23. Sample answer: The infantswho are best adapted to survivebirth are those that weigh about7 lb at birth. S7CS6.b, S7L5.b

CHAPTER RESOURCES


CRF • Chapter Reviewg• Chapter Test Ag• Chapter Test Ba• Chapter Test Cs• Vocabulary Activityg

Workbooks

Study Guide• Study Guide is also available in Spanish.

Chapter 7 • Chapter Review 187

Multiple Choice

1. Which of the following factorsis necessary in order for naturalselection to occur in a species?

A. genetic variation within a population

B. an abundance of food resources

C. a hospitable environment

D. a strong family structure

Use the diagram below to answer question 2.

Cocoa finchTree finch

Vegetarian finchWarbler finch

Grassquit

Ground finch

2. The branching diagram shows therelationship between several speciesof fi nches. Which species’ DNA is mostsimilar to the DNA of the tree fi nch?

A. Ground fi nch

B. Cocoa fi nch

C. Vegetarian fi nch

D. Warbler fi nch

3. Which of the following is an exampleof natural selection?

A. bears moving into a new part of a forestover many generations

B. a tree growing towards sunlight

C. shrubs growing longer thorns over manygenerations

D. a plant growing between rocks

4. Charles Darwin noticed that fi ncheson different islands of the GalápagosIslands were similar but that theirbeaks differed. What explanation forthese differences did he propose?

A. The beaks of the fi nches are adapted tothe way the bird usually gets food.

B. Specifi c genetic mutations occur thatmake beak size change in response torandom selection factors.

C. The different beaks of the fi nches wouldone day evolve into identical beaks.

D. Beak size is related to the size of thefi nch.

5. A scientist is studying fossils fromdifferent layers of sedimentary rock.Which rock layer will contain fossilsthat most closely resemble present-dayorganisms?

A. older rock layers

B. newer rock layers

C. all of the rock layers

D. none of the rock layers

6. A population of organisms is separatedinto two groups for many years. Whenwill the two populations be consideredtwo different species?

A. when the populations live in differenthabitats

B. when the populations eat different food

C. when the populations behave differently

D. when the populations can no longerinterbreed


Answer Key and Standards Guide

Teacher’s NotesTo provide practice undermore realistic testing conditions,give students 20 minutes toanswer all of the questions inthis Criterion-ReferencedCompetency Test Preparation.

Question 2 A, C, D: The diagram indicates thatcocoa finches and tree finches share the most-recent common ancestor. These two species areconnected by the shortest lines on the diagram.B: Correct.

Question 3 A: Bears moving into a new habitatis most likely an example of a learned behavior, notan inherited trait. B, D: Natural selection does notoccur over a single generation. C: Correct.

Question 1 A: Correct. B, C: Individuals that aremore adapted to their environment are better ableto thrive in their environments and to compete foravailable food resources than less adapted individualsare. Therefore, a hospitable environment and anabundance of food resources are not necessaryfor natural selection. D: Natural selection does notdepend on family structure.

Question Answer Standard

1 A S7L5.b

2 B S7L5

3 C S7L5.b

4 A S7L5.a

5 B S7L5.c

6 D S7L5

7 A S7L5

8 B S7L3.c

9 C S7L5

10 * S7L5.c

11 * S7L5.b

*See Test Doctor.

• CRCT Test Preparation worksheets from the Student Edition• Additional Test Preparation worksheets

CRCT Preparation Workbook

CRCT PreparationWorkbook

Use the test practiceworksheets to help studentsprepare for standardized tests.

CR

CT

Prep

aration

Use the table below to answer question 7.

Average Beak Measurements ofBirds of the Colores Islands

Island

Average beak length

(mm)

Average beak width

(mm)

Number of uniquespecies

Verde 9.7 6.5 5

Azul 8.9 8.7 15

Rosa 5.2 8.0 10

7. The table above shows average beak measurements for birds living on three islands. If narrow beaks are best for eating insects, on which island would you expect to fi nd the most birds that eat insects?

A. Verde Island

B. Azul Island

C. Rosa Island

D. Verde Island and Azul Island

8. Which of the following is an example of selective breeding?

A. Populations of lizards that have a certain trait become more numerous after a change in climate.

B. Farmers allow only sheep that produce the best wool to breed.

C. A population of bacteria develops resistance to an antibiotic.

D. A population of insects develops resistance to a pesticide after farmers repeatedly use the same pesticide to kill the insects.

9. Charles Darwin’s theory of natural selection was based partly on his observation that

A. DNA is the genetic material of all living things.

B. all eukaryotic cells have a nucleus.

C. some organisms have more offspring than others do.

D. garden pea plants can self-pollinate.

Open Response

10. A scientist is studying fossils found in the Georgia Coastal Plain. Fossil A resembles fossil B, but fossil B was found in a deeper layer than fossil A was. Briefl y describe the relationship between the fossils.

11. A population of lizards is separated when a canyon forms. The process of erosion widens the canyon, and the lizards become further separated. How will scientists know when the original species of lizard becomes two new species?

Chapter 7 • Criterion-Referenced Competency Test Preparation 189

Question 7 A: Correct. B: Birdson Azul Island have the widest beaks(an average width of 8.7 mm). C: Birdson Rosa Island have beaks that are amedium width (an average width of8.0 mm). D: Birds on each island havebeaks that are different average widths.

Question 8 A: A change in thepopulations of lizards after a changein climate is an example of naturalselection. The change is not an exampleof selective breeding. B: Correct.C: A population of bacteria developsantibiotic resistance through naturalselection. D: A population of insectsdevelops pesticide resistance throughnatural selection.

Question 9 A, B: Darwin did notknow how traits are inherited. He didnot know that DNA, which is stored inthe nuclei of eukaryotic organisms,controls traits. C: Correct. D: Mendel,not Darwin, experimented with peaplants.

Question 10 Full-credit answersshould include the following points:• Fossil A is the youngest fossil, and

fossil B is the oldest fossil.• Because of their similarity, fossils A

and B may be related to each otheror share a common ancestor.

Question 11 Full-credit answersshould include the following points:• Speciation is the formation of new

species as a result of evolution.• The two groups are considered to

be different species when they canno longer interbreed.

Question 4 A: Correct. B: Genetic mutationsthat affect beak size occur randomly. But selectionfactors, such as food availability, act to selectspecific traits, such as particular beak size.C: Describing how the beaks will change does notexplain how the different beaks developed. D: Beakshape and size are related to the type of food that isavailable. They are not related to the size of the finch.

Question 5 A: The fossils in older rock layersare less closely related to present-day organismsthan the fossils in newer rock layers are. B: Correct.C: Rock layers may contain some of the same fossils,but each layer will likely be different from the othersin some way. D: Newer rock layers contain fossilsthat tend to be similar to present-day organisms.

Question 6 A, B, C: Speciation occurs whenpopulations can no longer interbreed. Two popula-tions may live in different habitats, eat differentfoods, and behave differently but still be part of thesame species. D: Correct.

Sciencein Action

Language ArtsLanguage ArtsBefore you read this story, pre-dict what you think will happen.

Write a paragraph that “gives away” theending that you predict. After you have readthe story, listen to some of the predictionsmade by your classmates. Discuss youropinions about the possible endings. S7CS10.b

MathMathThe population of endangered plant species Ais 322 plants. If scientists can increase thenumber of plants by 7% each year, in howmany years will the population reach at least500 plants? (Hint: Round to whole numbers.)S7CS3.a, M7P1.b

Sciencein Action

WRITINGSKILL

Science Fiction“The Anatomy Lesson”by Scott SandersDo you know the feeling you get when youhave an important test? A medical studentfaces a similar situation in this story. Thestudent needs to learn the bones of thehuman body for an anatomy exam the nextday. The student goes to the anatomy libraryto study. The librarian lets him check out abox of bones that are supposed to be froma human skeleton. But something is wrong.There are too many bones. They are thewrong shape. They don’t fit together cor-rectly. Somebody must be playing a joke!Find out what’s going on and why the stu-dent and the librarian will never be the sameafter “The Anatomy Lesson.” You can read itin the Holt Anthology of Science Fiction. S7CS10.a

Focus onFocus onGEORGIAGEORGIA

Science, Technology,and SocietySeed BanksScientists in Georgia are making deposits in aspecial kind of bank. These banks are not formoney. They are for seeds! Saving the seedsof endangered plants that grow in Georgia,such as the smooth purple coneflower andthe Great Plains ladies’-tresses, can preventthese plants from becoming extinct. Boththe State Botanical Garden of Georgia andthe Georgia Southern Botanical Garden haveseed banks that are helping to preserve severaltypes of endangered plants in Georgia. Manyof the plants being preserved by seed banksmay provide food or medicine in the future.

Science, Technology,and SocietyTeaching Strategy -- GENERAL

To help students understand theimportance of seed banks andthe function of seed banks inthe conservation of endangeredplant species, have studentsresearch endangered or threat-ened plants that are native toGeorgia. Suggest to students thatthey contact the State BotanicalGarden of Georgia or the GeorgiaSouthern Botanical Garden tolearn what scientists are doingto preserve the native plants ofGeorgia. Then, have studentspresent an oral report on theinformation that they gathered.

Science FictionBackgroundAbout the Author ScottSanders (1945–) writes many dif-ferent kinds of stories. Early inlife, he chose to become a writerrather than a scientist, althoughhe still has an interest science.Sanders has written about folk-lore, physics, the naturalist JohnJames Audubon, and settlers ofIndiana. Much of his work isnonfiction. His writing has beenpublished in books and periodi-cals, such as the Chicago Sun-Times, Harper’s, and Omni.

Answer to Math Activity

7 years S7CS3.a, M7P1.b

Answer to Language Arts Activity

Student paragraphs may vary. Have studentscompare their predictions to the story’s endingand to other students’ predictions. S7CS10.b


Social StudiesSocial StudiesResearch a story of creation thatcomes from a Greek, Roman, or

Native American civilization. Write a para-graph summarizing the myth, and share itwith a classmate. S7CS10.a

To learn more about theseScience in Action topics, visitgo.hrw.com and type in thekeyword HL5EVOF.

Check out Current Science®

articles related to this chapterby visiting go.hrw.com. Justtype in the keyword HL5CS07.

WRITINGSKILL

Raymond PierottiCanine Evolution Raymond Pierotti thinks that it’s natural that he became an evo-lutionary biologist. He grew up exploring the desert around his home in New Mexico.He was fascinated by the abundant wildlife surviving in the bleak landscape. “One ofmy earliest memories is getting coyotes to sing with me from my backyard,” he says.

Pierotti now studies the evolutionary relationships between wolves, coyotes, anddomestic dogs. Some of his ideas come from the traditions of the Comanches. Accord-ing to the Comanche creation story, humans came from wolves. Although Pierottidoesn’t believe that humans evolved from wolves, he sees the creation story as a sug-gestion that humans and wolves have evolved together. “Wolves are very similar tohumans in many ways,” says Pierotti. “They livein family groups and hunt together. It is possiblethat wolves actually taught humans how to huntin packs, and there are ancient stories of wolvesand humans hunting together and sharing thefood. I think it was this relationship that inspiredthe Comanche creation stories.” S7CS10.d

People in SciencePeople in SciencePeople in Science

vv ----------------------------------------- GENERAL

Have every student write orpresent a report on a breed ofdog. The report should focus onthe origin and evolution of thebreed, with particular attentionpaid to the culture that bred itand why those characteristicswere chosen. The report couldalso explore whether thesebreeds make good householdpets and why. Students can eas-ily find information on dogbreeds on the Internet by search-ing for either the name of abreed or for “dog breeds” andvisiting any of several sites thatcollect information on differentbreeds.

Answer to Social Studies Activity

Student summaries may vary. Have studentsshare their summaries with each other or withthe entire class, and then discuss similaritiesbetween the myths. S7CS10.a

Chapter 7 • Science in Action 191

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