unit 2 ecology advance planning - temecula valley unified ......2. compare the different levels of...

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Unit Projects

Unit ProjectsUnit ProjectsUnit Projects

Unit 2Unit 2Advance PlanningChapter 2■ Purchase seeds and gather

materials for MiniLab 2-1.■ Order bromothymol blue and

antacid for MiniLab 2-2.■ Set up or borrow a fish tank

for a Quick Demo.■ Gather or purchase lichens for

a Quick Demo.■ Order cultures of Paramecium

and Didinium for the BioLab.■ Gather materials for the Alter-

native Lab.

Chapter 3■ Gather lichen and other ma-

terials for MiniLab 3-1.■ Purchase or borrow plants for

a Quick Demo. ■ Purchase plankton and gather

materials for Mini Lab 3-2.■ Gather pond water and other

materials for the BioLab.■ Gather sod for a Quick Demo.■ Gather materials for the Alter-

native Lab.

Chapter 4■ Purchase bananas and gather

materials for MiniLab 4-1.■ Purchase radish seeds. Gather

petri dishes and napkins forthe Alternative Lab.

■ Purchase materials for theBioLab.

Chapter 5■ Purchase or gather seeds and

other materials for the Alter-native Lab.

■ Gather gingko leaves for aQuick Demo.

■ Gather soil, water, and con-tainers for MinLab 5-2.

Make a ModelKinesthetic Students can create aworking aquatic ecosystem that

contains both biotic and abiotic elementsin a healthy balance.

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Use the LibraryIntrapersonal Have students usethe library to find out why space

exploration may be dependent on thequest for artificial closed ecosystems.L2

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Final ReportHave students present their group’sfindings in an oral report that could beunderstood by students at your localmiddle school. L3

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EcologyEcologyA tropical rain forest ecosystem consists ofinteractions among organisms, andbetween organisms and their environment.For example, rain forest plants are adaptedto use the ample water and sunlight in theproduction of nutrients. The plants usethese nutrients for their own growth anddevelopment, and, in turn, the nutrientsthat make up the plants may then be passedto animals that feed on them. Scarletmacaws eat seeds and fruits from rain forest trees, but they also eat clay soil thathelps to detoxify many of the poisonousplants that they eat.

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UNIT CONTENTSUNIT CONTENTS

Principles of Ecology

Communities and Biomes

Population Biology

Biological Diversity andConservation

UNIT PROJECTUNIT PROJECT

Use the Glencoe Science Web Site for more project

activities that are connected to this unit.www.glencoe.com/sec/science

Unit 2Unit 2

EcologyBIODIGESTBIODIGEST

Unit ProjectsUnit ProjectsUnit Projects

Unit Projects

Unit 2Unit 2

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Ecology

Unit OverviewThis unit focuses on the relation-ships and interactions that existamong organisms and their envi-ronments. In Chapter 2, studentsare introduced to ecology and thebiotic and abiotic factors thatexist in an ecosystem. Chapter 3centers on the development ofcommunities and describes majorworld biomes. In Chapter 4,environmental factors that limitpopulation growth are presented,and students study the effects ofdemographics. Chapter 5 bringsthe unit to a close with a discus-sion of people’s impact on theenvironment and threats to bio-diversity. Strategies of conserva-tion biology are described.

Introducing the UnitAsk students to look at the scarletmacaws in the photograph anddescribe how these birds aredependent on both living andnonliving things in their environ-ments. Explain that ecologyfocuses on the interactions thattake place in an environment.

Develop a Model of anEcosystemHave students do one of the projects for thisunit as described on the Glencoe Science WebSite. As an alternative, students can do oneof the projects listed on these two pages.

InterviewLinguistic Students can interview a pet shop owner to find out how

to keep fish in an aquarium. Students can describe how to maintain a healthyenvironment for the fish. L1

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DisplayVisual-Spatial Ask students tomake a bulletin board that describes

the experimental Biosphere II in Arizonaand explains why it did not work.

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http://www.glencoe.com/sec/science

Index to National Geographic MagazineThe following articles may be used forresearch relating to this chapter.“Rain Forest Canopy: The High Frontier,” by Edward O. Wilson, December 1991.

Teacher’s Corner

36B

Principles of EcologyPrinciples of Ecology

TransparenciesReproducible MastersSection

Organisms and TheirEnvironment

Nutrition andEnergy Flow

Section 2.1

Section 2.2

Teacher Classroom Resources

Section Focus Transparency 4

Section Focus Transparency 5Basic Concepts Transparency 1Basic Concepts Transparency 2Reteaching Skills Transparencies 1, 2, 3

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Chapter 2 OrganizerChapter 2 Organizer

Activities/FeaturesObjectivesSection

Organisms and TheirEnvironmentNational Science EducationStandards UCP.1-3; A.2;C.4, C.5, C.6; F.3; G.1-3(2 sessions, 1 block)

Nutrition and Energy FlowNational Science EducationStandards UCP.1-3; A.1, A.2; B.6; C.4, C.5, C.6; D.2;F.3-5; G.1, G.2 (3 sessions, 21/2 blocks)

1. Distinguish between the biotic and abiotic factors in the environment.

2. Compare the different levels of biologi-cal organization and living relationshipsimportant in ecology.

3. Explain the difference between a nicheand a habitat.

4. Compare how organisms satisfy theirnutritional needs.

5. Trace the path of energy and matter inan ecosystem.

6. Analyze how nutrients are cycled in theabiotic and biotic parts of the biosphere.

MiniLab 2-1: Salt Tolerance of Seeds, p. 38Problem-Solving Lab 2-1: p. 39Careers in Biology: Science Reporter, p. 40

Problem-Solving Lab 2-2. p. 52MiniLab 2-2: Detecting Carbon Dioxide, p. 56Inside Story: The Carbon Cycle, p. 57Design Your Own BioLab: How can onepopulation affect another? p. 60Biology & Society: The Florida Everglades—An Ecosystem at Risk, p. 62

Section 2.2

Section 2.1

MATERIALS LIST

BioLabp. 60 microscope, microscope slides,coverslips, droppers, beakers or jars,sterile pond water, culture of Didinium,culture of Paramecium

MiniLabsp. 38 seeds (40), small beaker (2),paper towels, zipper-lock plastic bags (2), labels, water, 10% salt watersolutionp. 56 test tubes (2), bromthymol bluesolution, antacid tablet, drinking straw

Alternative Labp. 40 corn seeds (60), pinto bean seeds(60), paper cups (6), plastic sandwichbags (6), water, paper towels, gradu-ated cylinder, labels, pencil

Quick Demosp. 40 aquarium setupp. 45 lichensp. 55 glass bowl, soil, plants, water,plastic wrap

Need Materials? Contact Carolina Biological Supply Company at 1-800-334-5551or at http://www.carolina.com

36A

Assessment Resources Additional ResourcesSpanish ResourcesEnglish/Spanish AudiocassettesCooperative Learning in the Science ClassroomLesson Plans/Block Scheduling

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Chapter Assessment, pp. 7-12MindJogger VideoquizzesPerformance Assessment in the Biology ClassroomAlternate Assessment in the Science ClassroomComputer Test BankBDOL Interactive CD-ROM, Chapter 2 quiz

Refer to pages 4T-5T of the Teacher Guide for an explanation of the National Science Education Standards correlations.

Reinforcement and Study Guide, pp. 7-8Critical Thinking/Problem Solving, p. 2BioLab and MiniLab Worksheets, p. 9Laboratory Manual, pp. 9-10Tech Prep Applications, pp. 3-4Content Mastery, pp. 9-10, 12

Reinforcement and Study Guide, pp. 9-10BioLab and MiniLab Worksheets, pp. 10-12Concept Mapping, p. 2Content Mastery, pp. 9, 11-12Laboratory Manual, pp. 11-14Inside Story Poster

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Key to Teaching StrategiesKey to Teaching Strategies

Level 1 activities should be appropriatefor students with learning difficulties.Level 2 activities should be within theability range of all students.Level 3 activities are designed for above-average students.ELL activities should be within the abilityrange of English Language Learners.

Cooperative Learning activitiesare designed for small group work.These strategies represent student prod-ucts that can be placed into a best-workportfolio.These strategies are useful in a blockscheduling format.

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The following multimedia resources are available from Glencoe.

Biology: The Dynamics of LifeCD-ROM

Video: How Organisms InteractVideo: SymbiosisBioQuest: Antarctic Food WebExploration: Pyramid of Energy

Videodisc ProgramHow Organisms InteractSymbiosisThe Everglades

The Infinite VoyageSecrets From a Fozen World

The Secret of Life SeriesNichePredator–PreyMutualism

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http://www.carolina.com

Section

What Is Ecology?Do you know anyone who likes to

observe nature? Perhaps it is a personwho knows the names of many ani-mals, plants, or rocks. People haveenjoyed studying nature for thou-sands of years. Birdwatchers knowthe names and behaviors of the birdsin their area. Some people carefullyrecord observations of rainfall andtemperature. Others make it a hobbyto study plants; they keep log bookswith records of when plants pro-duced leaves, flowers, and fruit, asshown in Figure 2.1. Some peoplewho are interested in nature record

observations, discuss their results,and note how patterns change fromyear to year.

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s shown in the photographs, people can impact plant andanimal communities in both

positive and negative ways. Learninghow ecological principles explain interaction between organisms andtheir environment can help you understand environmental issuesand form your own opin-ions about them. Inthis section, you willlearn some of thehistory and thefocus of ecology.

SECTION PREVIEW

ObjectivesDistinguish betweenthe biotic and abioticfactors in the environ-ment.Compare the differentlevels of biological organization and livingrelationships importantin ecology.Explain the differencebetween a niche and a habitat.

Vocabularyecologybiosphereabiotic factorbiotic factorpopulation communityecosystem habitatnichesymbiosis commensalismmutualism parasitism

2.1 Organisms and Their Environment

Animals wander into citiesin search of food (above).A wildlife rehabilitatorreleases an owl (inset).

Figure 2.1 An amateur naturestudy log book fromthe 17th century.

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Section 2.1

BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES

Use with Chapter 2,Section 2.1

How do these organisms interact with one another andwith the nonliving parts of the environment?

What might happen if the zebras were removed?

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SECTION FOCUS

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Transparency Interactions WithinEcosystems4

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PrepareKey ConceptsStudents are provided with anoverview of the history of ecol-ogy, living and nonliving factorsin an environment, and closerelationships among organismsthat enhance survival.

Planning■ Gather seeds, salt, and other

materials for MiniLab 2-1.Mustard seeds work very well.You can find them in the spicesection of any supermarket.

■ Set up or borrow a fish tankfor the Quick Demo.

■ Gather or purchase lichens forthe Quick Demo.

■ Gather cups, bags, and seeds(pinto beans or corn) for theAlternative Lab.

1 FocusBellringer Before presenting the lesson,display Section Focus Trans-parency 4 on the overhead pro-jector and have students answerthe accompanying questions.

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Assessment PlannerAssessment PlannerPortfolio Assessment

Portfolio, TWE, pp. 39, 42, 53Performance Assessment

MiniLab, TWE, p. 38Alternative Lab, TWE, pp. 40-41Assessment, TWE, pp. 42, 58, 59MiniLab, SE, pp. 38, 56BioLab, SE, pp. 60-61

Knowledge AssessmentAssessment, TWE, pp. 47, 55Section Assessment, SE, pp. 47, 59Chapter Assessment, SE, pp. 63-65

Skill AssessmentProblem-Solving Lab, TWE, pp. 39, 52MiniLab, TWE, p. 56BioLab, TWE, pp. 60-61

36 PRINCIPLES OF ECOLOGY

Principles of Ecology

What You’ll Learn■ You will describe ecology and

the work of ecologists.■ You will identify important

aspects of an organism’s environment.

■ You will trace the flow ofenergy and nutrients in theliving and nonliving worlds.

Why It’s ImportantTo understand life, you need to know how organisms meettheir needs in their naturalenvironments. To reduce theimpact of an expanding humanpopulation on the naturalworld, it is important to under-stand how living things dependon their environments.

Make a ChainThink of the things you eat.Now consider how these fooditems obtained their food whenthey were alive. Can you makea food chain, starting with thesun and ending with one ofyour food items?

To find outmore about

ecology, visit the GlencoeScience Web Site. www.glencoe.com/sec/science

2

GETTING STARTEDGETTING STARTED

ChapterChapter

You might think mosquitoesare pests, but for trout andother animals, mosquitoesand their larvae are a majorfood source.

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Theme DevelopmentSystems and interactions is atheme of this chapter. Organismshave niches because of interac-tions among biotic and abioticfactors. A critical aspect of nicheis how organisms obtain nutrientsand energy. Energy flow, a majortheme of Section 2, is tracedthrough the trophic levels of afood chain.

Chapter 2Chapter 2

MultipleLearningStyles

Look for the following logos for strategies that emphasize different learning modalities.

Visual-Spatial Portfolio, pp. 39,53; Quick Demo, p. 40; Enrich-

ment, p. 41; Reinforcement, p. 55Interpersonal Project, p. 43;Reteach, p. 47; Meeting

Individual Needs, pp. 51, 54Intrapersonal Portfolio, p. 42;Meeting Individual Needs, p. 42

Linguistic Biology Journal, pp. 44, 50, 56; Project, p. 46;

Extension, p. 47; Portfolio, p. 58Logical-MathematicalDiscussion Question, p. 54Naturalist Reinforcement, pp. 46, 49; Activity, p. 47;

Biology Journal, p. 52; Going Further, p. 62

GETTING STARTED DEMOGETTING STARTED DEMO

Have students examine thechapter opener photographs.Discuss the feeding relation-ships shown. The trout eats themosquito. Human blood nour-ishes the mosquito. Help stu-dents realize that humans, likethe mosquito and trout,depend on other living thingsfor food. Have students choosean animal product they eat andthen show this feeding relation-ship in a food chain—for exam-ple, sun to grass to cow tohuman.

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If time does not permit teach-ing the entire chapter, use theBioDigest at the end of theunit as an overview.

Resource ManagerResource Manager

Section Focus Transparency 4and Master

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The nonliving environment:Abiotic factors

Ecology includes the study of fea-tures of the environment that are notliving because these features are animportant part of an organism’s life.For example, a complete study of theecology of moles would include anexamination of the types of soil inwhich these animals dig their tunnels.Similarly, a thorough investigation ofthe life cycle of trout would need toinclude whether these fish lay theireggs on rocky or sandy stream bot-toms. The nonliving parts of an organ-ism’s environment are the abiotic factors (ay bi AHT ihk). Examples ofabiotic factors include air currents,temperature, moisture, light, and soil.

Abiotic factors have obvious effectson living things and often determinewhich species survive in a particularenvironment. For example, lack ofrainfall can cause drought in a grass-land, as shown in Figure 2.2. Canyou think of changes in a grasslandthat might result from a drought?Grasses would grow more slowly,wildflowers would produce fewerseeds, and the animals that dependon plants for food would find itharder to survive. Examine otherways that abiotic factors affect livingthings in the MiniLab and Problem-Solving Lab shown on these pages.

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Figure 2.2 Droughts are common ingrasslands. As the grasses dryout, they turn yellow andappear to be dead, but newshoots grow in the low-lyingareas soon after it rains.Some animal species areadapted to living in grass-lands by their ability to bur-row underground and sleepthrough the dry periods.

How does an abiotic factor affect food production?Green plants carry out the process of photosynthesis. Glucose,a sugar, is one of the products produced during this process.Thus, glucose production can be used as a means for judgingthe rate at which the process of photosynthesis is occurring.

AnalysisExamine the following graph of a plant called salt bush

(Atriplex). It shows how this plant’s glucose production isinfluenced by temperature.

Thinking Critically1. Name the abiotic factor influencing photosynthesis and

describe the influence of this factor on photosynthesis.2. Name the biotic factor being influenced.3. Based on the graph, describe the type of ecosystem this

plant might live in. Explain your answer.4. Does the graph tell you how the rate of photosynthesis

might vary for plants other than salt bushes? Explain youranswer.

5. Hypothesize why the formation of glucose drops quicklyafter reaching 30°C.

Problem-Solving Lab 2-1Problem-Solving Lab 2-1 Interpreting Data

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Food Production in Salt Bush

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Purpose Students will determine howtemperature influences the rate atwhich photosynthesis occurs for aspecific plant.

Process Skillsanalyze information, draw a con-clusion, interpret data

Teaching Strategies■ You may wish to introduce theprocess of photosynthesis bydescribing the raw materialsneeded and the role the processplays in providing food for all lifeforms.■ You might explain the termoptimum as it relates to the opti-mum temperature at which pho-tosynthesis occurs for salt bush.

Thinking Critically

1. Temperature. As temperatureincreases, the photosynthesisrate also increases until amaximum of 30°C (optimumtemperature) is reached.Above 30°, the photosynthe-sis rate decreases.

2. food production3. Salt bush appears to benefit

from warm temperaturesbecause it produces maxi-mum food amounts at highertemperatures. It may, there-fore, be found living in thedesert.

4. The graph is specific for saltbush. The responses of otherplants to temperature wouldhave to be determined exper-imentally.

5. High temperatures may dam-age or kill the cells responsi-ble for photosynthesis.

Skill Have students writea lab report summarizing theresults of the lab. Use the Per-formance Task Assessment Listfor Lab Report in PASC,p. 47. L2

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AssessmentAssessment

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Problem-Solving Lab 2-1Problem-Solving Lab 2-1

Ecology definedThe branch of biology that devel-

oped from natural history is calledecology. Ecology is the scientificstudy of interactions among organ-isms and their environments.Ecological study reveals relationshipsamong living and nonliving parts of

MiniLab 2-1MiniLab 2-1 Experimentingthe world. Ecology combines infor-mation and techniques from manyscientific fields, including mathemat-ics, chemistry, physics, geology, andother branches of biology.

You have learned that scientificresearch includes both descriptiveand quantitative methods. Most ecol-ogists use both types of research.They obtain descriptive informationby observing organisms in the fieldand laboratory. They obtain quanti-tative data by making measurementsand carrying out carefully controlledexperiments. Using these methods,ecologists learn a great deal aboutrelationships, such as what organismsa coyote eats, how day length influ-ences the behavior of migratingbirds, how tiny shrimp help rid oceanfishes of parasites, or how acid rainthreatens some of Earth’s forests.

Aspects of Ecological Study

As far as we know, life exists onlyon Earth. Living things can be foundin the air, on land, and in both fresh-and salt water. The biosphere (BI uhsfihr) is the portion of Earth thatsupports life. It extends from high inthe atmosphere to the bottom of theoceans. This life-supporting layermay seem extensive to us, but if youcould shrink Earth to the size of anapple, the biosphere would be thin-ner than the apple’s peel.

Although it is thin, the biosphereis very diverse and supports a widerange of organisms. The climate,soils, plants, and animals in a desertare very different from those in atropical rain forest. Living things areaffected by both the physical envi-ronment and by other living things.Ecologists study these interactionsamong different organisms and theirenvironments.


Salt Tolerance of Seeds Salinity, or the amount of salt dis-solved in water, is an abiotic factor. Might salt water affect howcertain seeds sprout or germinate? Experiment to find out.

Procedure! Soak 20 seeds in freshwater and 20 seeds in salt water

overnight.@ The next day, wrap the seeds in two different moist

paper towels. Slide the towels into separate self-sealingplastic bags.

# Label the bags “fresh” and “salt.”$ Examine all seeds two days later. Count the number of

seeds in each treatment that show signs of root growth orsprouting, which is called germination. Record your data.CAUTION: Be sure to wash your hands after handlingseeds.

Analysis1. Did the germination rates differ between treatments? If

yes, how?2. What abiotic factor was tested in this experiment? What

biotic factor was influenced?3. Might all seeds respond to salt in a similar manner? How

could you find out?

Salt marshFreshwater pond

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2 Teach

Purpose Students will experiment with theabiotic factor of salinity to deter-mine if seed germination isaffected.

Process Skillscollect data, experiment, inter-pret data

Teaching Strategies■ Prepare the 10% sodium chlo-ride (table salt) solution by dis-solving 100 g of table salt in 900mL of tap water.■ Allow students to form ahypothesis prior to the experi-ment. At the conclusion of theactivity, ask if their hypothesiswas supported.■ Ask students to identify thecontrol and the independent anddependent variables in the exper-iment.■ Have students work in smallgroups.

Expected ResultsSeeds soaked in water will showgermination. Seeds in salt waterwill show little or no germina-tion.

Analysis1. Yes. Seeds soaked in tap water

germinate. Seeds soaked insalt water do not.

2. salinity of water; germination3. No, each seed type may

respond differently to salin-ity. Experimentation isneeded.

Performance Have stu-dents design an experiment thatwould determine the minimumpercentage of salinity that can betolerated by a specific seed typeand still allow germination tooccur. Use the Performance TaskAssessment List for Assessing aWhole Experiment and Planningthe Next Experiment in PASC,p. 33. L2

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MiniLab 2-1MiniLab 2-1

PortfolioPortfolio

Studying the Local EnvironmentVisual-Spatial Ask students to ob-serve the natural environment of the

area in which they live on several differentdays. Tell them to prepare a table in whichthey list the biotic and abiotic factors of the environment. Have students summarizethe importance of the abiotic factors listedin their tables.

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MEETING INDIVIDUAL NEEDS MEETING INDIVIDUAL NEEDS

Learning DisabledVisual-Spatial Provide students whomay require reinforcement of the

concepts of biotic and abiotic factors withphotographs from old nature magazines.Ask students to identify all the biotic fac-tors in each photograph. Ask them toexplain why they identified these factorsas biotic.

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People and HabitatsPeople may alter habitats, which changesthe abiotic factors. Have students survey theschool grounds and find five examples ofspecific changes that people made and how

each has affected the abiotic environment. Forexample, a parking lot covered with asphaltreduces the amount of water entering theground. On sunny days the asphalt gets hotterthan unpaved land.

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levels, as shown in Figure 2.4. Theystudy individual organisms, interac-tions among organisms of the samespecies, and interactions among

organisms of different species.Ecologists also study how abiotic fac-tors affect groups of interactingspecies.

2.1 ORGANISMS AND THEIR ENVIRONMENT 41

Figure 2.4 Ecology deals with severallevels of biological organi-zation, including organ-isms, populations, commu-nities, ecosystems, biomes,and the biosphere.

Organism

Communities

Populations

Ecosystems

Biosphere

EnrichmentVisual-Spatial Have studentsobserve organisms in their

habitats, such as insects in a for-est. Ask students to list a fewexamples of how the organismsinteract with other organisms andwith their nonliving environ-ment. Then have them choose anillustration in Figure 2.4 anddescribe its biotic and abioticinteractions.

Revealing MisconceptionsStudents may think an ecologistis the same as an environmental-ist. Ask students how they are dif-ferent. Ecologists investigate ecology.Environmentalists are proponents ofprotecting the environment.

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seeds. Look for signs of germination(small roots growing from a seed), andrecord the number of seeds from eachcontainer that are germinating eachday.

Analysis1. What abiotic factor is being investi-

gated? effect of water on seed germi-nation

2. Which seems to be the optimum (best)time for seed germination? The time

will depend on the seed type used.3. Will the seeds all germinate at the

same time? Explain. No, each seed typewill have its own optimum soakingtime.

Performance Have studentsdesign and then perform an experimentto determine how the abiotic factor of light affects seed germination. Use thePerformance Task Assessment List forDesigning an Experiment in PASC,p. 23. L2

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The living environment: Biotic factors

Look at the goldfish in Figure 2.3.Now consider its relationships withother organisms. It may depend onother living things for food, or it may be food for other life. Thegoldfish needs members of the samespecies to reproduce. To meet itsneeds, the goldfish may competewith organisms of the same or differ-ent species.

A key consideration of ecology isthat living organisms affect otherorganisms. All the living organismsthat inhabit an environment arecalled biotic factors (by AHT ihk).Ecologists investigate how biotic fac-tors affect different species. To helpthem understand the interactions ofthe biotic and abiotic parts of theworld, ecologists have organized theliving world into levels.

Levels of Organizationin Ecology

The study of an individual organ-ism, such as a male deer, known as abuck, might reveal what food items itprefers, how often it eats, and howfar it roams to search for food orshelter. Although it spends a largepart of its time alone, it does interactwith other individuals of its species.For example, it periodically goes insearch of a mate, which may requirebattling with other bucks.

All organisms depend on othersfor food, shelter, reproduction, orprotection. So you can see that thestudy of an individual would provideonly part of the story of its life cycle.To get a more complete picturerequires studying its relationshipswith other organisms.

Ecologists study interactionsamong organisms at several different


CAREERS IN BIOLOGY

Science Reporter

Does science fascinate you? Can you explain complex

ideas and issues in a clear andinteresting way? If so, youshould consider a career as ascience reporter.

Skills for the JobAs a science reporter, you

are a writer first and a scientistsecond. A degree in journalismand/or a scientific field is usually neces-sary, but curiosity and good writing skills are also essential.You might work for newspapers, national magazines, medicalor scientific publications, television networks, or Internetnews services. You could work as a full-time employee or afreelance writer. You must read constantly to stay up-to-date.Many science reporters attend scientific conventions andevents to find news of interest to the public. Then they care-fully and accurately translate what’s new so nonscientists canunderstand it.

For more careers in related fields, be sureto check the Glencoe Science Web Site.

www.glencoe.com/sec/science

Figure 2.3 How might other living things affect this goldfish?

Alternative LabMoisture and Seed Germination

Purpose Students will determine if the amount oftime that seeds are soaked in water influ-ences their future germination.

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Materials120 seeds (corn, pinto beans), six papercups, six plastic sandwich bags, water,paper toweling, graduated cylinder, labelsProcedureGive students the following directions.

1. Label each of six cups with your name,the date, and one of the followingtimes: 1, 6, 12, 24, or 48 hours.

2. Fill each cup with 10 mL of water. Add20 seeds to each cup.

3. Remove the seeds from each cup whenthe time marked is reached. Wrap theseeds in a layer of paper toweling andplace each batch of seeds into a sepa-rate, labeled plastic bag.

4. Seal the bags. Prepare a control bagwith 20 unsoaked seeds. Caution:Remind students to wash their handsafter handling seeds.

5. Starting the next day and continuingfor five days, observe each group of40

Quick DemoQuick Demo

Visual-Spatial Showstudents an aquarium

with live fish and plants. Askwhat nonliving things influ-ence the life of a fish. waterquality, temperature, light,and presence of oxygen Askwhat living things influencethe life of the fish. other fish,plants, and bacteriaP

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Career PathCourses in high school:journalism, biology, phy-

sics, astronomy, geology, andother sciences.College: degree in journalism ora scientific field

Career IssueAsk students if they think sciencereporters should focus primarilyon the inventions, discoveries,and issues that most readers willbe able to understand. Shouldscience reporters avoid highlytechnical topics?

For More InformationFor more information aboutbecoming a science reporter, stu-dents can write to:

The National Association ofScience Writers

P.O. Box 294Greenlawn, NY 11740

CAREERS IN BIOLOGY

CD-ROMBiology: The Dynamicsof Life

Video: How Organisms InteractDisc 1


BioLab and MiniLab Work-sheets, p. 9

Laboratory Manual, pp. 9-10L2

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grows so large it begins affecting thefood supply for another species in thecommunity.

Interactions among living things and abiotic factors form ecosystems

In a healthy forest community,interactions among populations mightinclude birds eating insects, squirrelseating nuts from trees, mushroomsgrowing from decaying leaves or bark,and raccoons fishing in a stream. Inaddition to population interactions,ecologists also study interactionsamong populations and their physicalsurroundings in ecosystems. Anecosystem is made up of the interac-tions among the populations in a com-munity and the community’s physicalsurroundings, or abiotic factors.

There are three major kinds ofecosystems. Terrestrial ecosystemsare those located on land. Examples

include forests, meadows, and desertscrub. Aquatic ecosystems occur inboth fresh- and saltwater. Freshwaterecosystems include ponds, lakes, andstreams. Saltwater ecosystems, alsocalled marine ecosystems, make upapproximately 75 percent of Earth’ssurface. Figure 2.8 shows a marineand a freshwater ecosystem.

Figure 2.7 Beech and maple treesdominate this forestcommunity; therefore,it is called a beech-maple forest. Beech-maple forests arefound in the easternUnited States, Europe,and northeast China.

Figure 2.8 There may be hundreds of populations interacting in apond or tide pool. How do you think the abiotic factorsin these environments affect the biotic factors?

Dragonflies live near moist meadows and ponds. They feed on small insects theycatch while flying. Dragonflies lay their eggsin the pond or on pond plants.

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Organisms living in tide pools must survivedramatic changes in abiotic factors. Whenthe tide is high, ocean waves replenish thewater in the pool. When the tide is low,water in the pool evaporates.

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Visual LearningAsk students to use Figure 2.8 todescribe adaptations that helpanimals living in tide pools sur-vive when the tide is low for sev-eral hours. Responses may includeshells that help the animal retainmoisture or the ability to burrowinto moist sand. Then ask studentshow they think the abiotic factorsin these environments affect thebiotic factors. Responses mayinclude that sunlight affects watertemperature and whether photosyn-thesis will occur. Air dissolved in thewater affects the respiratory andphotosynthetic processes of the pondorganisms, which, in turn, affect theflow of energy.

Interactions within populationsThe marsh marigolds shown in

Figure 2.5 form a population. Apopulation is a group of organisms ofone species that interbreed and livein the same place at the same time.

Members of the same populationmay compete with each other forfood, water, or other resources. Com-petition occurs only if resources arein short supply. How organisms in apopulation share the resources oftheir environment determines howfar apart organisms live and howlarge the populations become.

Some species have adaptations thatreduce competition within a popula-

tion. An example is the life cycle of afrog, shown in Figure 2.6. The juve-nile stage of the frog, called the tad-pole, not only looks very differentfrom the adult but also has com-pletely different food requirements.Many species of insects, includingdragonflies and moths, also producejuveniles that differ from the adult inbody form and food requirements.

Individuals interact within communities

No species lives independently ofother species. Just as a population ismade up of individuals, a communityis made up of several populations. Acommunity is a collection of inter-acting populations. An example of acommunity is shown in Figure 2.7.

A change in one population in acommunity will cause changes in theother populations. Some of thesechanges can be minor, such as when asmall increase in the number of indi-viduals of one population causes asmall decrease in the size of anotherpopulation.

For example, if the population ofmouse-eating hawks increasesslightly, the population of mice will,as a result, decrease slightly. Otherchanges might be more extreme, aswhen the size of one population


Figure 2.5 These marshmarigolds representa population oforganisms. Whatcharacteristics areshared by this groupof flowers that makethem a population?

Figure 2.6 Adult frogs and theiryoung have differentfood requirements.This limits competitionfor food resources forthe species.

Eggs that adult frogs lay in thewater hatch into tadpoles. Tadpoleshave gills, live in water, and eatalgae and small aquatic creatures.

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Adult frogs live both on land andin the water. They breathe airand eat insects such as dragon-flies, grasshoppers, and beetles.

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Visual LearningAsk students to use Figure 2.6 todescribe the adaptations of theadult frog that enable it to swimwell. strong hind legs, webbed feetWhich adaptations allow it tohide or escape from its predators?body coloration, strong hind legsWhat adaptations in the tadpoleenable it to swim well? large tailfin

Performance Have stu-dents write two questions basedon what they have read so far.Organize the class into pairs andhave them use their questions toquiz each other. L2

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Hearing ImpairedIntrapersonal Provide students withpictures of an insect larval stage and

adult stage, such as a caterpillar and but-terfly. Have students research the insect’slife cycle and determine how differencesin the developmental stages help theinsect survive in its community. L2

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PortfolioPortfolio

Limits on LifeIntrapersonal Ask students to findthe names of five organisms that

belong to tide pool or pond communities.Have them research how abiotic factorslimit or affect life and write a report fortheir portfolios.

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VIDEODISCBiology: The Dynamicsof Life

How Organisms Interact (Ch. 4)Disc 1, Side 1, 40 sec.!7TÇ"

P R O J E C TA Miniature Ecosystem

Interpersonal Have students work incooperative groups to create aquari-

ums or terrariums in large, wide-mouthedjars, such as a peanut butter jar. For theaquarium, students will need to purchasematerials from a pet store. For the terrarium,they can obtain soil, plants, and animals

from the environment. Instruct each team tokeep a log of the interactions between pop-ulations and the abiotic factors of their envi-ronment. Caution students to handle liveanimals with care. Remind them to washtheir hands after handling animals, soil, andplants.

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VIDEODISCThe Infinite VoyageSecrets from a Frozen

World, The Southern Ocean—A Rich Marine Ecosystem (Ch. 1)

5 min. 30 sec.!7-8J"


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different materials, and at differenttimes. These differences lead toreduced competition.

Each species is unique in satisfyingall its needs; each species occupies aniche. A niche (nich) is the role andposition a species has in its environ-ment—how it meets its needs forfood and shelter, how it survives, andhow it reproduces. A species’ nicheincludes all its interactions with thebiotic and abiotic parts of its habitat.It is an advantage for a species tooccupy a niche different from thoseof other species. Life may be harsh inthe polar regions, but the polar bear,with its thick coat, flourishes there.Nectar may be deep in the flower,

inaccessible to most species, but thehummingbird, with its long beak,gets it. Unique strategies and struc-tures are important to a species’niche and important for reducingcompetition with other species.

Living relationshipsSome species enhance their

chances of survival by forming rela-tionships with other species.Biologists once assumed that allorganisms living in the same environ-ment are in a continuous battle forsurvival. Some interactions are harm-ful to one species, yet beneficial toanother. Predators are animals suchas lions and insect-eating birds that


A millipede eats decayingleaves near the log.

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These ants eat dead insects.DD

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Organisms inEcosystems

A prairie dog living in a grasslandmakes its home in burrows it digsunderground. Some species of birdsmake their homes in the trees of abeech-maple forest. In these forests,they find food, avoid enemies, andreproduce. The grassland and beech-maple forests are examples of habi-tats. A habitat (HAB uh tat) is theplace where an organism lives out itslife. Organisms of different speciesuse a variety of strategies to live andreproduce in their habitats. Habitatscan change, and even disappear, froman area. Examples of how habitats

change due to both natural andhuman causes are presented in Biologyand Society at the end of this chapter.

Niche Although several species may share

a habitat, the food, shelter, and otheressential resources of that habitat areoften used in different ways. Forexample, if you turn over a log likethe one shown in Figure 2.9, youwill find millipedes, centipedes,insects, and worms living there. Atfirst, it looks like this community ofanimals is competing for foodbecause they all live in the same habi-tat. But close inspection reveals thateach feeds in different ways, on


Figure 2.9 This series of photographs showshow a habitat can be seen as a col-lection of several niches. As you cansee, each species uses the availableresources in a different way.

A worm obtains nourishmentfrom the organic material it eatsas it burrows through the soil.

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A centipede is a predatorthat captures and eatsbeetles and other animals.

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BIOLOGY JOURNAL BIOLOGY JOURNAL

Connecting the DisciplinesLinguistic Have students list in theirjournals specific areas of chemistry,

physics, and geology that might be stud-ied as part of ecology. Also,ask them todescribe the types of quantitative datathat would be used in the specific areasthey have listed. L2

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Bring in a stone or tree barkwith lichens growing on it.Explain that lichens consist oftwo organisms—fungi andalgae. Have students hypothe-size why they coexist.

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Internet Address Book

Note Internet addresses that you find useful in the spacebelow for quick reference.

VIDEODISCThe Secret of LifeNiche (fundamental)

Niche (realized)

!7;TBI"

!7;TLJ"

Concept DevelopmentThe term niche is sometimesdescribed as an activity that aperson is good at but that othersfind difficult. Ask how this is sim-ilar to the biological definition.Organisms in a niche frequentlyhave adaptations that give them anadvantage in their environments.


Video: SymbiosisDisc 1


Symbiosis (Ch. 5)Disc 1, Side 137 sec.!7^É"

Revealing MisconceptionsSome people incorrectly assumethat symbiosis is equivalent tomutualism. Ask students toexplain the relationship betweenthe terms. Symbiosis includes sev-eral kinds of relationships, includingmutualism, which is a relationshipin which both species benefit.

for the ants. In an experiment, ecolo-gists removed the ants from some aca-cia trees. Results showed that thetrees with ants grew faster and sur-vived longer than trees without ants.

Sometimes, one organism harmsanother. Have you ever owned a dogor cat that was attacked by ticks orfleas? Ticks and fleas, shown inFigure 2.13, are examples of para-sites. A symbiotic relationship inwhich one organism derives benefitat the expense of the other is calledparasitism (PER uh suh tihz um).Parasites have evolved in such a waythat they harm, but usually do notkill, the host. If the host dies, theparasite also will die unless it canquickly find another host. Some par-asites, such as tapeworms and round-worms, live inside other organisms.


Section AssessmentSection Assessment

Understanding Main Ideas 1. List several different biotic and abiotic factors

in an ecosystem.2. Compare and contrast populations and

communities.3. Give examples that would demonstrate the dif-

ferences between the terms niche and habitat.4. A leaf-eating caterpillar turns into a nectar-

eating butterfly. How is this feeding behavior an advantage for this species?

Thinking Critically5. Clownfish are small, tropical marine fish

usually found swimming among the stinging tentacles of sea anemones. What type of symbi-otic relationship do these animals have if theclownfish are protected by the sea anemone, but the anemone does not benefit from theclownfish?

6. Designing an Experiment Design an experi-ment to test the hypothesis that clownfish andsea anemones have a mutualistic relationship.For more help, refer to Practicing ScientificMethods in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

Figure 2.13Ticks cause harm to the animals they liveon when they obtainnutrients from theirhost animal. This relationship is calledparasitism.

Figure 2.12These ants and acacia trees both benefit from living in closeassociation. This mutualistic relationship is so strong that innature the trees and ants are never found apart.

OriginWORDWORD

ecology From the Greekwords oikos, mean-ing “homestead,”and logos, meaning“the study of.”Ecology is the studyof how organismsinteract with their environments.

ReteachInterpersonal Ask studentsto work in groups to provide

examples of biotic and abioticfactors within the classroom orschool.

ExtensionLinguistic Ask students toresearch how abiotic factors

limit life in the Arctic tundra orin a desert environment. Havethem include a written summaryof the information they gather intheir portfolios.

Knowledge Ask studentsto consider the school grounds anecosystem. Have them explainand give examples of populationsand communities that live in this“ecosystem.”

4 CloseActivity

Naturalist Have studentswork in groups to invent

four pairs of organisms that dis-play all four symbiotic relation-ships. Students should name theorganisms, describe the interac-tions, and identify the symbioticrelationships.P

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kill and eat other animals. The ani-mals that predators eat are calledprey. Predator-prey relationshipssuch as the one between lions andwildebeests involve a fight for sur-vival. Use the BioLab at the end ofthis chapter to more closely examinea predator-prey relationship. Butthere are other relationships amongorganisms that help maintain survivalin many species. The relationship in

which there is a close and permanentassociation among organisms of dif-ferent species is called symbiosis(sihm by OH sus). Symbiosis meansliving together.

There are several kinds of symbio-sis. A symbiotic relationship betweenthe peregrine falcon and red-breastedgoose has evolved in the cold arcticregion of Siberia in Russia, as shownin Figure 2.10. Normally, the pere-grine falcon preys upon the red-breasted goose, but the falcon huntsaway from its nesting area. Duringthe nesting season, the falcon fiercelydefends its territory from predators.The geese take advantage of this,choosing nesting areas close to thoseof the falcons, and are thereby pro-tected from predators. The geesebenefit from the relationship, and thefalcon is neither benefited norharmed. This is called a commensalrelationship. Commensalism (kuhMEN suh lihz um) is a symbiotic rela-tionship in which one species benefitsand the other species is neitherharmed nor benefited.

Commensal relationships alsooccur among plant species. Spanishmoss, a kind of flowering plant thatgrows on the branch of a tree, isshown in Figure 2.11. Orchids,ferns, mosses, and other plants some-times grow on the branches of largerplants. The larger plants are notharmed, but the smaller plants bene-fit from the additional habitat.

Sometimes, two species of organ-isms benefit from living in close asso-ciation. A symbiotic relationship inwhich both species benefit is calledmutualism (MYEW chuh lihz um).Ants and acacia trees living in the sub-tropical regions of the world illustratemutualism, as shown in Figure 2.12.The ants protect the tree by attackingany animal that tries to feed on it.The tree provides nectar and a home

Figure 2.11Spanish moss growson and hangs fromthe limbs of trees butdoes not obtain anynutrients or cause anyharm to the trees.

Figure 2.10Red-breasted geese (a) and peregrine falcons (b) both nest in the Siberian arcticin the spring. They share a symbiotic relationship.

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P R O J E C TLiving With a Legume

Linguistic A mutualistic symbiotic rela-tionship exists between clover root

nodules and bacteria. This relationship iscommonly found in leguminous plants.Prepared slides are available of root nodulesthat show this relationship. Have studentsobserve these slides under a microscope and

make diagrams of their observations. Havestudents use caution when working withprepared slides. Ask them to research thename of the bacterium that lives in the nodules. Students should write a report oftheir observations and explain how the relationship benefits both plant and bac-terium.

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VIDEODISCThe Secret of LifePredator-Prey

Mutualism

!<<UX9LJ"

!<DOXUtG"

ReinforcementNaturalist Describe the fol-lowing situations to stu-

dents: A bird builds its nest in thecrook of a tree branch. Algaegrow on the shell of a marine tur-tle. Ask why each situation illus-trates commensalism. Nests at treeheight are protected from somepredators, and the tree is neitherhelped nor harmed. Algae benefit byreceiving light as the turtle swimsnear the water’s surface. The turtleis not harmed nor helped. Bothexamples show relationships betweendifferent species. L1

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3 AssessCheck for UnderstandingHave students explain the rela-tionship between the words ineach of the following pairs.

a. biology—ecologyb. population—ecosystemc. habitat—niched. symbiosis—mutualism

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1. Responses may include the following:Biotic—tree, grass, human, dog, antAbiotic—daylight hours, amount ofrainfall, humidity, air, soil.

2. A population consists of a single speciesthat can interbreed and is present inthe same place at the same time. Acommunity consists of several popula-tions that interact with one another.

3. Responses may be similar to the follow-ing: Squirrel—habitat: forest; niche:gathers, eats, and stores nuts.Mushroom—habitat: moist forest soil;niche: digests and absorbs organic mat-ter. Bat—habitat: cave; niche: fertilizesflowers, eats insects.

4. The caterpillar and the butterfly do notcompete with each other for food.

5. Commensalism. The clownfish bene-fits, but the sea anemone is nothelped nor hurt.

6. The experiment would compare the growth and health of a sea ane-mone and clownfish when they livetogether and when they live sepa-rately.

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Critical Thinking/ProblemSolving, p. 2 L3

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Reinforcement and StudyGuide, pp. 7-8

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organisms are called heterotrophs(HET uh ruh trohfs). Heterotrophsinclude organisms that feed only onautotrophs, organisms that feed onlyon other heterotrophs, and organ-isms that feed on both autotrophsand heterotrophs.

Some heterotrophs, such as graz-ing, seed-eating, and algae-eatinganimals, feed directly on autotrophs.The wildebeests in Figure 2.14depend on plants for their food. Aheterotroph that feeds only on plantsis called a herbivore. Herbivoresinclude rabbits, grasshoppers,beavers, squirrels, bees, elephants,and fruit-eating bats.

Some heterotrophs eat other het-erotrophs. Animals such as lions thatkill and eat only other animals arecalled carnivores. Some animals donot kill for food; instead, they eatanimals that have already died.Scavengers such as black vulturesfeed on carrion and refuse, and play abeneficial role in the ecosystem.Imagine for a moment what the envi-ronment would be like if there wereno vultures to devour animals killed

on the African plains, no buzzards toclean up dead animals along roads,and no ants and beetles to removedead insects and small animals fromsidewalks and basements.

Humans are an example of a thirdtype of heterotroph. The teenagersin Figure 2.15 are eating a variety offoods that include both animal andplant materials. They are omnivores.Raccoons, opossums, and bears areother examples of omnivores.

Figure 2.14 Many kinds of organisms live in the savanna of EastAfrica. Identify theautotrophs and theheterotrophs.

Figure 2.15 People are omnivores because they eatboth autotrophs and heterotrophs.

OriginWORDWORD

herbivore From the Latinwords herba, mean-ing “grass,” andvorare, meaning “todevour.” Herbivoresfeed on grass andother plants.

carnivore From the Latinwords caro, meaning“flesh,” and vorare,meaning “todevour.” Carnivoreseat animals.

omnivore From the Latinwords omnis, mean-ing “all,” and vorare,meaning “todevour.” Carnivoreseat both plants andanimals.

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2 TeachUsing Scientific TermsCall students’ attention to thederivations of the terms herbivore,carnivore, and omnivore, presentedin the margins of these pages.Ask students to explain theappropriateness of each term tothe feeding habits of the organ-isms it describes. Herbivores areorganisms that feed upon grasses andplants; carnivores feed on the flesh ofanimals; omnivores feed on bothplant and animal products.

ReinforcementNaturalist Have students listcommon pets. Ask them to

identify the foods that are typi-cally provided to each pet ontheir list. Challenge students toclassify each pet as an omnivore,carnivore, or herbivore basedupon the foods it eats. L1

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Section


How Organisms Obtain Energy

A roadrunner sprints, a cactusflowers, an aphid reproduces. Energydrives all these events. One of themost important characteristics of aspecies’ niche is how the speciesobtains its energy. Ecologists tracethe flow of energy through commu-nities to discover nutritional relation-ships. The ultimate source of theenergy is the sun, which supplies theenergy that fuels life.

The producers: AutotrophsPlants use the sun’s energy to man-

ufacture food in a process called pho-tosynthesis. Organisms that useenergy from the sun or energy stored

in chemical compounds to manufac-ture their own nutrients are calledautotrophs (AWT uh trohfs). Thegrass in Figure 2.14 is an autotroph.Although plants are the most familiarterrestrial autotrophs, some unicellu-lar organisms also make their ownnutrients. Most other organismsdepend on autotrophs for nutrientsand energy.

The consumers: HeterotrophsA deer nibbles the leaves of a

clover plant, a bison munches grass,an owl swallows a mouse. The deer,buffalo, and owl are incapable of pro-ducing their own food. They obtainnutrients by eating other organisms.Organisms that cannot make theirown food and must feed on other

What eats what? The orioleeats the grasshopper. Thegrasshopper eats the grass.

Organisms, such as the oriole,grasshopper, and grass, need nutri-tion for growth, repair, and energy.How they satisfy their nutritionalneeds is an importantpart of their niche,and an importantfocus of ecology.

SECTION PREVIEW

ObjectivesCompare how organisms satisfy theirnutritional needs.Trace the path ofenergy and matter in an ecosystem.Analyze how nutrientsare cycled in the abioticand biotic parts of thebiosphere.

Vocabularyautotrophheterotrophscavengerdecomposerfood chaintrophic levelfood web

2.2 Nutrition and EnergyFlow

OriginWORDWORD

autotroph From the Greekwords auto, meaning“self,” and trophe,meaning “nourish-ment.” Autotrophsare self-nourishing;they make their own food.

heterotroph From the Greekwords hetero, mean-ing “other,” and trophe, meaning“nourishment.”Heterotrophs consume otherorganisms for theirnutrition.

Orioles (above) andgrasshoppers (inset)form part of a foodchain.

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Section 2.2

PrepareKey ConceptsEnergy is needed for survival.The ways that organisms obtainand pass energy are depicted withfood chains and food webs. Thissection also addresses trophic lev-els and the nitrogen, carbon, andwater cycles.

Planning■ Set up a terrarium to help

show the water cycle.■ Gather bromothymol blue and

antacid for MiniLab 2-2.■ Bring in a fertilizer label for

the Enrichment.■ Purchase duckweed for the

Project on plant growth.■ Prepare sterile pond water or

follow the directions in theBioLab for substitutions.

1 FocusBellringer Before presenting the lesson,display Section Focus Trans-parency 5 on the overhead pro-jector and have students answerthe accompanying questions.

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BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES

Use with Chapter 2,Section 2.2

What is the source of all energy in this ecosystem?

What path does this energy take to get to the hawk?

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Learning DisabledLinguistic Have students who under-stand the concept of producer and

consumer work with students who are having difficulty. Group the terms pro-ducer, plant, and autotroph and consumer, heterotroph, and animal. Have studentsanalyze the meanings of the groups.

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Cultural DiversityCultural Adaptations to theEnvironmentHumans occupy all types of habitats, adapt-ing to Earth’s varying environments in manyways. For example, people have designedclothing suited to a wide range of climateconditions, from heavy rainfall to sub-zerotemperatures. People around the world useavailable materials to create shelters

adapted to their environments. Ask studentsto describe some examples of using availablematerials to meet needs created by the envi-ronment. Inuit groups in North America builthomes from snow and ice to conserve heat.Groups living in the southwestern UnitedStates built homes using a mud and clay mix-ture called adobe.

Resource ManagerResource ManagerSection Focus Transparency 5 and

Master

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Concept Mapping, p. 2

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Food chains: Pathways for matter and energy

The wetlands community picturedin Figure 2.16 illustrates examples offood chains. A food chain is a simplemodel that scientists use to show howmatter and energy move through anecosystem. Nutrients and energyproceed from autotrophs to het-erotrophs and, eventually, to decom-posers.

A food chain is typically drawn usingarrows to indicate the direction inwhich energy is transferred from oneorganism to the next. One food chainin Figure 2.16 could be shown as

algae ➜ fish ➜ heron

Food chains can consist of threelinks, or steps, but most have no

more than five links. This is becausethe amount of energy remaining inthe fifth link is only a small portionof what was available at the first link.A portion of the energy is lost as heatat each link. It makes sense, then,that typical food chains are three orfour links long.

2.2 NUTRITION AND ENERGY FLOW 51

Second-order heterotrophs, which are carni-vores, make up the third trophic level. Theyfeed on first-order heterotrophs. The heronis a carnivorous bird that feeds on fishes,frogs, and other small animals of the wet-land habitat.

CC

Third-order heterotrophs, carnivoresthat feed on second-order heterotrophs,make up the fourth trophic level. An alli-gator eating a shorebird is one exampleof a third-order heterotroph. Bacteriaand fungi decompose all the links of thefood chain when organisms die.

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ReinforcementAsk students to describe possiblefood chains, other than the oneshown in Figure 2.16. They arelikely to substitute different organ-isms in place of those shown or men-tioned in the text. Accept all logicalresponses.

Visual LearningAsk students to use Figure 2.16to identify other animals thatmight occupy the third trophiclevel. Responses may include otherbirds of prey such as owls or eagles orland animals such as lions, bears, orcats. Accept all logical responses.

Some organisms, such as fungi,break down and absorb nutrientsfrom dead organisms. These organ-isms are called decomposers.Decomposers break down the com-plex compounds of dead and decay-ing plants and animals into simplermolecules that can be more easilyabsorbed by the decomposers, and byother organisms. Some protozoans,many bacteria, and most fungi carryout this essential process of decom-position.

Matter and Energy Flow in Ecosystems

When you pick an apple from atree and eat it, you are consumingcarbon, nitrogen, and other elementsthe tree has used to produce the fruit.That apple also contains energy fromthe sunlight trapped by the tree’sleaves while the apple was growingand ripening.

Matter and energy flow throughorganisms in ecosystems. You havealready learned that feeding relation-ships and symbiotic relationshipsdescribe ways in which organismsinteract. Ecologists study these inter-actions to make models that trace theflow of matter and energy throughecosystems.

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Figure 2.16 In order for a wetland ecosystem to function, itsorganisms must depend on each other for a supplyof energy. Follow the steps in the wetland foodchain shown here.

First-order heterotrophs, or herbi-vores, compose the second trophiclevel of a food chain. For example,in this wetland, small fishes andcrustaceans feed on algae.

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The first trophic level in all foodchains is made up of photosyntheticautotrophs—the producers. In thiswetland community, grasses, mangrove and cypress trees, and aquatic phytoplankton are autotrophs.

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Discussion QuestionsAsk students to explain what thearrow in all food chains repre-sents. The arrow shows in whichdirection matter and energy aremoving through the food chain.Why must all second-levelorganisms be consumers? By defi-nition, these organisms feed on orconsume other organisms. Whymust all third-level organisms becarnivores and not herbivores? Bydefinition, these organisms feed onother animals and are thereforemeat or flesh eaters. L2

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Living as a DecomposerLinguistic Have students assumethey are decomposers. Ask them to

write a short paragraph that describes: a) what they look like, b) where they live,c) what they are going to eat. L2

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English Language LearnersInterpersonal Have students workin pairs to list some of the foods

they have consumed in the past 24 hours.Then have each pair determine if theywere a first-order, second-order, or third-order consumer of each food.

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Human DietsHave students write out a restaurantmenu that incorporates several food

items that would illustrate humans actingas first-order, second-order, and third-orderconsumers.

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VIDEODISCThe Infinite Voyage: Secrets from a Frozen

WorldKrill: The Vital Link of a FoodChain (Ch. 2) 5 min. 30 sec.

!77BB"


Basic Concepts Trans-parency 1 and Master

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base of the ecological pyramid repre-sents the autotrophs, or first trophiclevel. Higher trophic levels are lay-ered on top of one another. Examineeach type of ecological pyramid inFigures 2.18, 2.19 and 2.20. Eachpyramid gives different information

about an ecosystem. Observe thateach pyramid summarizes interac-tions of matter and energy at eachtrophic level. Notice that the initialsource of energy for all three of theseecological pyramids is energy fromthe sun.


Figure 2.17 A forest communityfood web includesmany organisms ateach trophic level.Arrows indicate theflow of materials andenergy.

Red tail hawk

Grizzly bear

Marmot

Grouse

Chipmunk

Seeds

Berries

Grasses

Insects

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Chalkboard ExampleWrite the word human at the topof the chalkboard. Ask studentsto complete a food web thatincludes the two trophic levelsbelow humans, using as many dif-ferent organisms for each level aspossible. Examples of first-orderconsumers may include chickens,cows, sheep, and pigs; examples ofproducers may include grass, shrubs,lettuce, pears, and corn. Ask stu-dents to explain why this repre-sents a food web rather than afood chain. A food chain involvesonly one organism for each trophiclevel.

Tying to PreviousKnowledgeHave students review the mean-ings of the terms scavenger anddecomposer. Ask them to describethe role of each type of organismin a food chain or food web.

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How can you organize trophic level information?Diagrams or charts may help to summarize information orconcepts in a more logical and simpler manner. This is thecase with information that shows relationships amongtrophic levels.

AnalysisCopy the diagram above. It will show, when completed

correctly, the various relationships in a food chain.

Thinking Critically1. Each box represents a trophic level. Write the name for

each trophic level in the proper box. Use these choices: 1storder heterotroph, autotroph; 3rd order heterotroph; 2ndorder heterotroph.

2. Each bracket identifies one or more traits of the trophiclevels. Use the following labels to identify them in theirproper order: herbivore, autotroph, carnivore, het-erotroph, producer.

3. What is being represented by the small arrows connectingtrophic levels?

Problem-Solving Lab 2-2Problem-Solving Lab 2-2 Applying Concepts

Trophic levels represent links in the chain

Each organism in a food chain rep-resents a feeding step, or trophiclevel (TROHF ihk), in the passage ofenergy and materials. Examine howenergy flows through trophic levelsin the Problem-Solving Lab shownhere. A food chain represents onlyone possible route for the transfer ofmatter and energy in an ecosystem.Many other routes may exist. As

Figure 2.16 indicates, many differentspecies occupy each trophic level in awetlands ecosystem. In addition,many different kinds of organisms eata variety of foods, so a single speciesmay feed at several trophic levels.For example, the great blue heroneats largemouth black bass, but it alsoeats minnows, bluegills, and frogs.The alligator may feed on the heron,fish, or even a deer that comes tooclose. Can you think of other possi-ble food chains in this ecosystem?

Food websSimple food chains are easy to

study, but they cannot indicate thecomplex relationships that existamong organisms that feed on morethan one species. Ecologists who areparticularly interested in energy flowin an ecosystem set up experimentswith as many organisms in the com-munity as they can. The model theycreate, a food web, expresses all thepossible feeding relationships at eachtrophic level in a community. A foodweb is a more realistic model than afood chain because most organismsdepend on more than one otherspecies for food. Notice how the foodweb of the forest ecosystem shown inFigure 2.17 represents a network ofinterconnected food chains. In anactual ecosystem, many more plantsand animals would be involved in thefood web.

Energy and trophic levels:Ecological pyramids

How can you show how energy isused in an ecosystem? Ecologists usefood chains and food webs to modelthe distribution of matter and energy within an ecosystem. Theyalso use another kind of model, called an ecological pyramid. An eco-logical pyramid shows how energyflows through an ecosystem. The


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Purpose Students use their knowledge oftrophic levels to organize andsummarize information.

Process Skillsthink critically, classify, sequence

Teaching Strategies■ You may wish to provide theoutline diagrams to students.■ Allow students to work insmall groups to complete the lab.■ Remind students that there isonly one correct placement foreach label.■ Review and/or define any termthat is still not clear to students.

Thinking Critically

1. Starting at the lowest level:autotroph;1st-order heterotroph;2nd-order heterotroph;3rd-order heterotroph.

2. Starting at the lowest level onthe left: producer, herbivore,carnivore (top two levels). Onthe right, the lowest level isautotroph and the top threelevels are heterotrophs.

3. Small arrows show directionof energy from one trophiclevel to next.

Skill Ask students to pre-pare a concept map of the ideascovered in this lab. Their mapsmust include all terms used onthe diagram. Use the Perfor-mance Task Assessment List forConcept Map in PASC, p. 89.

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Problem-Solving Lab 2-2Problem-Solving Lab 2-2


It’s a JungleNaturalist Have students comparetrophic levels to the organization of

a business. Ask them to diagram a specificbusiness to show how each level ofemployee supports the next level. L2

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PortfolioPortfolio

Making a Food WebVisual-Spatial Ask students to designa food web using the following

organisms: wheat, rat, fox, human, cow,corn, rabbit, hawk, grass. Have them use a colored pencil or marker to outline onefood chain in this web. Ask them to indicate tropic levels as well as omnivores,herbivores, and carnivores. L1

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BioQuest: Antarctic Food WebDisc 1


Exploration: Pyramid of EnergyDisc 1


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Cycles in NatureFood chains, food webs, and eco-

logical pyramids all show how energymoves in only one direction throughthe trophic levels of an ecosystem.Ecological pyramids also show howenergy is lost from one trophic levelto the next. This energy is lost to theenvironment as heat generated by the body processes of organisms.Sunlight is the primary source of allthis energy, so energy is always beingreplenished.

Matter, in the form of nutrients,also moves through the organisms ateach trophic level. But matter cannotbe replenished like the energy fromsunlight. The atoms of carbon, nitro-gen, and other elements that make upthe bodies of organisms alive todayare the same atoms that have been onEarth since life began. Matter is con-stantly recycled.

The water cycleLife on Earth depends on water.

Even before there was life on Earth,water cycled through stages, asshown in Figure 2.21. Have you everleft a glass of water out and a fewdays later observed there was lesswater in the glass? This is the resultof evaporation. Just as the water

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Figure 2.21 In the water cycle,water is constantlymoving betweenthe atmosphereand Earth.

Figure 2.20Pyramid of biomass Each barin the pyramid repre-sents the amount ofbiomass within atrophic level. Noticethat biomassdecreases as thetrophic levelincreases.

Second orderconsumers

Herbivores

Producers

Evaporation

Runoff

Oceans

Groundwater

Lakes

Evaporation

Transpiration

Precipitation

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ReinforcementVisual-Spatial Have studentsdiagram the water cycle for

inclusion in their portfolios.Encourage them to label themajor processes involved in thewater cycle, such as evaporation,condensation, precipitation, res-piration, transpiration, excretion,and decomposition. Students mayuse library reference materials ifnecessary.

Knowledge Have studentsexplain how the movement ofwater through its cycle differsfrom the movement of energythrough the trophic levels. L2

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The pyramid of energy shown inFigure 2.18 illustrates that energydecreases at each succeeding trophiclevel. The total energy transfer fromone trophic level to the next is onlyabout ten percent because organismsfail to capture and eat all the foodavailable at the trophic level belowthem. When an organism consumesfood, it uses some of the energy inthe food for metabolism, some forbuilding body tissues, and some isgiven off as waste. When the organ-ism is eaten, the energy that was usedto build body tissue is available asenergy to be used by the organismthat consumed it. The energy lost ateach successive trophic level entersthe environment as heat.

Ecologists construct a pyramid ofnumbers based on the populationsizes of organisms in each trophiclevel. The pyramid of numbers inFigure 2.19 shows that populationsizes decrease at each higher trophiclevel. This is not always true. Forexample, one tree can be food for 50000 insects. In this case, the pyramidwould be inverted.

A pyramid of biomass, such as theone shown in Figure 2.20, expressesthe weight of living material at eachtrophic level. Ecologists calculate thebiomass at each trophic level by find-ing the average weight of eachspecies at that trophic level and mul-tiplying by the estimated number oforganisms in each population.


Figure 2.19Pyramid of numbers Each barin the pyramid repre-sents population sizewithin a trophic level.Notice that popula-tion size decreases asthe trophic levelincreases.

Figure 2.18 Pyramid ofenergy Each bar inthe pyramid repre-sents energy avail-able within a trophiclevel. Notice thatenergy decreases asthe trophic levelincreases.

Hawks 1

Grasshoppers260

Partridges25

Grass3000

Producers

Herbivores

Carnivores

Top carnivores

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Concept DevelopmentHave students imagine a roped-off patch of forest. All the producers, herbivores, and con-sumers are put into piles. Askwhich pile would be largest. theproducer pile Explain that a bio-mass pyramid is made afterweighing the piles. Burning thepiles and measuring the energyleads to a pyramid of energy.Counting organisms leads to apyramid of numbers.

Discussion QuestionLogical-Mathematical Havestudents analyze the error in

logic for the following scenario.Humans are not at the mercy ofproducers for their food becausethey eat animals as a food source.Thus, people would not suffer ifall autotrophs were suddenly todie out. Students should recognizethat the animals humans eat arethemselves dependent on producersfor their food. L3

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English Language Learners/Learning Disabled

Interpersonal Have students workin pairs to count the number of grass

plants, ants, earthworms, or beetles in aten-centimeter-square area on the schoolgrounds. Students should then use thissmall sample to estimate the biomass for aten-square meter area.

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A terrarium, such as a largeglass bowl containing soil andplants and capped with plasticwrap, can be used to show thewater cycle. Through evapora-tion and transpiration, waterleaves the soil. The water vaporcondenses on the plastic wrapand drops accumulate, simulat-ing cloud formation. When thedrops are large enough, theyfall back to the soil, simulatingprecipitation.

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Follow the Light EnergyVisual-Spatial Have students assumethey are a “packet” of light energy

from the sun with a value of 100 energyunits. Have them trace their path througha simple food chain and indicate theirvalue at each level. Have them assumethat only ten percent of the energy ispassed from one level to the next. L2

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VIDEODISCThe Secret of LifePyramid of Biomass

!7;TtD"

VIDEODISCSTV: WaterWater Quality

Unit 1, Side 1, 1 min. 37 sec.Hydrologic Cycle

!8)60Y83"


Reteaching Skills Trans-parency 3 and Master

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The Carbon Cycle

From proteins to sugars, carbon is the building block of the molecules of life. Linked carbon atoms form the frame

for molecules produced by plants and other living things.Organisms use these carbon molecules for growth and energy.

Critical Thinking How is carbon released from the bodies oforganisms? Forests use carbon dioxide.

INSIDESSTORTORYY

INSIDE

Atmosphere Carbondioxide gas is one form ofcarbon in the air.

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PhotosynthesisAutotrophs use car-bon dioxide in photo-synthesis. In photo-synthesis, the sun’senergy is used to make high-energy carbon molecules.

22Wastes Auto-trophs and hetero-trophs break downthe high-energycarbon moleculesfor energy. Carbondioxide is releasedas a waste.

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Organisms use high-energy carbonmolecules for growth. A large amountof the world’s carbon is contained inliving things.

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Fuel Over millions of years, the remains of deadorganisms are converted into fossil fuels, such as coal,gas, and oil. These fuels contain carbon molecules.

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Pollution Combustionof fossil fuels and woodreleases carbon dioxide.

77Carbon dioxide

Soil When organisms die and decay, the carbon molecules inthem enter the soil.Microorganisms breakdown the molecules,releasing carbon dioxide.

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IINSIDENSIDESSTORTORYY

INSIDE

Purpose Students study the cycling of car-bon in the environment.

Teaching Strategies■ Help students understand thatplants remove carbon dioxidefrom the atmosphere and use itto create nutrients. When plantsand animals use the nutrients forenergy, carbon dioxide isreturned to the atmosphere.■ Help students understandother ways carbon dioxide entersthe atmosphere.

Visual Learning■ Have students trace a carbon

molecule from the atmos-phere, through two trophiclevels, and back into theatmosphere.

Critical ThinkingThe carbon is released in theform of carbon dioxide throughrespiration, decay, or burning.

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Detecting Carbon DioxideCarbon dioxide is given offduring respiration. When car-bon dioxide is dissolved inwater, an acid is formed.Certain chemicals called indi-cators can be used to detectacids. One indicator, calledbromothymol blue, willchange from its normal bluecolor to green or yellow if an acid is present.

Procedure! Half fill a test tube with bromothymol blue solution.@ Add a quarter of an effervescent antacid tablet to the

tube and note any color change. # Half fill a test tube with bromothymol blue solution.

Using a straw, exhale into the bromothymol blue at least30 times. CAUTION: Do not inhale the bromothymol blue.Record any color change in the test tube.

Analysis1. Describe the color change that occurs when carbon

dioxide is added to bromothymol blue.2. What was the chemical composition of the bubbles seen

in the tube with the antacid tablet?3. Does exhaled air contain carbon dioxide? Explain.

MiniLab 2-2MiniLab 2-2 Observing and Inferring

evaporated from the glass, waterevaporates from lakes and oceans andbecomes water vapor in the air.

Have you ever noticed the drops ofwater that form on a cold can ofsoda? The water vapor in the air con-denses on the surface of the canbecause the can is colder than thesurrounding air. Just as water vaporcondenses on cans, it also condenseson dust in the air and forms clouds.Further condensation makes smalldrops that build in size until they fallfrom the clouds as precipitation inthe form of rain, ice, or snow. Thewater falls on Earth and accumulatesin oceans and lakes where evapora-tion continues.

Plants and animals need water tolive. Plants pull water from theground and lose water from theirleaves through transpiration. Thisputs water vapor into the air. Animalsbreathe out water vapor in everybreath; when they urinate, water isreturned to the environment. Naturalprocesses constantly recycle waterthroughout the environment.

The carbon cycleAll life on Earth is based on carbon

molecules. Atoms of carbon form theframework for proteins, carbohy-drates, fats, and other important mol-ecules. More than any other element,carbon is the molecule of life.

The carbon cycle starts with theautotrophs. During photosynthesis,energy from the sun is used to con-vert carbon dioxide gas into energy-rich carbon molecules. Autotrophsuse these molecules for growth andenergy. Heterotrophs, which feedeither directly or indirectly on theautotrophs, also use the carbon mole-cules for growth and energy. Whenthe autotrophs and heterotrophs usethe carbon molecules for energy, car-bon dioxide is released and returnedto the atmosphere. Learn how todetect the presence of carbon dioxidein the MiniLab shown here. The car-bon cycle is described in the InsideStory on the next page.

The nitrogen cycleIf you add nitrogen fertilizer to a

lawn, houseplants, or garden, youmay see that it makes them greener,bushier, and taller. Even though theair is 78 percent nitrogen, plantsseem to do better when they receivenitrogen fertilizer. This is becauseplants cannot use the nitrogen in theair. They use nitrogen in the soil thathas been converted into more usableforms.


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Purpose Students will use bromothymolblue to test for the presence ofcarbon dioxide gas.

Process Skillsacquire information, draw a con-clusion, observe and infer, recog-nize cause and effect

Safety PrecautionsCaution students not to inhale ordrink the bromothymol solution.Have them wear goggles and alab apron.

Teaching Strategies■ Prepare bromothymol bluesolution as follows: Stock solu-tion—add 0.5 g bromothymolblue powder to 500 mL distilledwater. Dilute 10 mL stock solu-tion with 500 mL of distilledwater. (If solution is green, addone or more drops of NH4OHuntil a blue color appears. If solu-tion is deep blue, add one ormore drops of HCl until a lightblue color appears.)■ An effervescent antacid mustbe used. Check the label to besure the ingredients include acarbonate or bicarbonate and aweak acid such as citric acid.■ Bromothymol blue does notactually indicate the presence ofcarbon dioxide. It changes colorin the presence of any acid solu-tion, such as the carbonic acidformed by carbon dioxide andwater.

Expected ResultsBromothymol blue will change togreen or yellow when an antacidtablet is added or exhaled air isbubbled through the indicator.The color change shows that car-bon dioxide is present.

Analysis1. Bromothymol blue changes

to green or yellow when car-bon dioxide gas is added.

2. carbon dioxide3. Yes, the color change in the

bromothymol blue indicatedthe presence of carbon diox-ide.

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MiniLab 2-2MiniLab 2-2


A Wet Life CycleLinguistic Have students write adescription of what it would be like

to be a molecule of water that is cycledthrough an ecosystem. Where would theyspend most of their time, what siteswould they visit, and how many changesin phase (gas, liquid, solid) might theyexperience? L2

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English Language LearnersVisual-Spatial Have students workin groups to prepare a concept map

describing the carbon cycle. Included inthis map should be terms such as con-sumers, photosynthesis, respiration, decay,and producers. Group students who arelearning English with those who are flu-ent in the language. L2

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Skill Have students make a hypothe-sis for an experiment using bromothymolblue and a decomposer. Use the Perform-ance Task Assessment List for Formulating aHypothesis in PASC, p. 21. L2

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VIDEODISCThe Secret of LifeCarbon Cycle

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Portfolio Have studentssummarize the carbon cycle anddraw their own diagrams. Askthem to label the parts of thecycle and use arrows to show thedirection of movement.


Resource ManagerResource ManagerBioLab and MiniLab Worksheets,

p. 10 Laboratory Manual, pp. 11-14Reteaching Skills Transparency 1 and

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Figure 2.23In the phosphorus cycle, phosphorusmoves between the living and non-living parts of the environment.

Section AssessmentSection Assessment

Understanding Main Ideas1. What is the difference between an autotroph

and a heterotroph?2. Why do autotrophs always occupy the lowest

level of ecological pyramids?3. Give two examples of how nitrogen cycles

from the abiotic portion of the environment into living things and back.

4. Describe a food chain that was not presented in this section.

Thinking Critically5. The country of Avorare has many starving

people. Should you encourage the people togrow crops such as vegetables, wheat, and corn,or is it better to encourage them to use the landto raise cattle for beef?

6. Designing an Experiment Suppose there is a fertilizer called GrowFast. It contains extra nitrogen and phosphorus. Design an experiment to see if GrowFast increases thegrowth rate of plants. For more help, refer to the Practicing Scientific Methods in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

cycle. Phosphorus also has a long-term cycle, where phosphates washedinto the sea are incorporated intorock as insoluble compounds.Millions of years later, as the envi-

ronment changes, the rock contain-ing phosphorus is exposed. As therock erodes and disintegrates, thephosphorus again becomes part ofthe local ecological system.

Death

Limestone

Phosphorusin soil

Phosphorus incorporatedinto limestone

Long-term phosphorus cycleShort-term phosphorus cycle

Ocean

Phosphates washedinto ocean

ReteachHave students identify the trophiclevel of each organism in a foodchain and indicate the directionof energy flow.

ExtensionNaturalist Have studentsspeculate about the conse-

quences to a food web if anorganism at the second trophiclevel were to be eliminated. Thiswould eliminate a food source forsome organisms at the third trophiclevel.

Performance Have stu-dents diagram, label, and explainone of the following: a food web,water cycle, energy or biomasspyramid, or carbon cycle.

4 CloseActivity

Visual-Spatial List on thechalkboard 20 different

organisms. Have students usethese organisms to create a foodweb.

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As Figure 2.22 shows, lightningand certain bacteria convert thenitrogen in the air into these moreusable forms. Chemical fertilizersalso give plants nitrogen in a formthey can use.

Plants use the nitrogen to makeimportant molecules such as pro-teins. Herbivores eat plants and con-vert nitrogen-containing plant pro-teins into nitrogen-containing animalproteins. After you eat your food,you convert the proteins in your foodinto human proteins. Urine, an ani-mal waste, contains excess nitrogen.When an animal urinates, nitrogenreturns to the water or soil. Whenorganisms die, their nitrogen mole-cules return to the soil. Plants reusethese nitrogen molecules. Bacteria

also act on these molecules and putnitrogen back into the air.

The phosphorus cycle Materials other than water, carbon,

and nitrogen cycle through ecosys-tems. Substances such as sulfur, cal-cium, and phosphorus, as well as oth-ers, must also cycle through anecosystem. One essential element,phosphorus, cycles in two ways.

All organisms require phosphorusfor growth and development. Plantsobtain phosphorus from the soil.Animals get phosphorus by eatingplants, as shown in Figure 2.23.When these animals die, theydecompose and the phosphorus isreturned to the soil to be used again.This is the short-term phosphorus

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Figure 2.22In the nitrogen cycle,nitrogen is convertedfrom a gas to com-pounds important for life and back to a gas.

Nitrogen inatmosphere

Storm cloudsand lightning

Animal wastesDeath

Amino acidsynthesis

Decay bacteria

Nitrates

Infiltration ofground water

Ammonia,ammonium, andnitrate fertilizers

Runoff

Bacteria in soiland root nodules

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ReinforcementAsk students to trace the roles ofproducers, consumers, anddecomposers in the cycling ofnitrogen. Producers take in nitro-gen compounds in soil and pass thesecompounds to consumers that eat theproducers. Decomposers break downthe nitrogen compounds and releasenitrogen gas to the air.

EnrichmentShow students plant fertilizerlabels. These fertilizers addnitrogen and phosphorous to thesoil because these substances arefrequently in short supply.Explain the numbers on the label.For example, a plant fertilizerthat is labeled 20-20-10 contains20 percent nitrogen, 20 percentphosphorous, and 10 percentpotassium compounds.

Performance Assessmentin the Biology Classroom, p. 59,First-Level Biological Magnifi-cation. Have students completethis activity to expand upon theirknowledge of environmentalproblems that can harm organ-isms.

3 AssessCheck for UnderstandingHave students explain the rela-tionship between the words ineach of the following pairs.

a. autotroph—producerb. heterotroph—consumerc. recycling—carbond. lightning—nitrogen cycleP

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PortfolioPortfolio

Cycles and GardeningLinguistic Ask students to write areport for local gardeners, explain-

ing how the water and nitrogen cyclesaffect their success in growing flowersand vegetables. Have students includediagrams showing both cycles.

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VIDEODISCThe Secret of LifeNitrogen Cycle

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Section AssessmentSection AssessmentSection Assessment1. An autotroph makes its own nutrients.

A heterotroph must consume anotherorganism to meet its nutritional needs.

2. Autotrophs capture light energy andcreate nutrients. When eaten, theyprovide nutrients for other organisms.

3. (1) Nitrogen in the air passes to bacteria, which form compounds usedby plants. Decay of dead plants returns

nitrogen to air. (2) Nitrogen in airpasses to bacteria and again moves toplants. Plants are eaten by consumers,passing along nitrogen. Decay of deadconsumers returns nitrogen to air.

4. Any realistic food chain is acceptable.Arrows should show the correct flowof energy.

5. Crops are better because growing

them takes less land than raising cattle.Crops provide more energy for peoplethan cattle, at a higher trophic level.

6. Designs should include control andexperimental groups. Sample sizeshould be greater than one plant.Students should define growth, as theincrease in plant height.

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Resource ManagerResource ManagerReteaching Skills Transparency 2 and

Master Reinforcement and Study Guide,

pp. 9-10Content Mastery, pp. 9, 11-12 L1

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PLAN THE EXPERIMENTPLAN THE EXPERIMENT

1. Review the discussion of feed-ing relationships in this chapter.

2. Decide which materials youwill use in your investigation.Record your list.

3. Be sure that your experimentalplan contains a control, tests asingle variable such as popula-tion size, and allows for thecollection of quantitative data.

4. Prepare a list of numbereddirections. Explain how youwill use each of your materials.

Check the PlanDiscuss the following points

with other group members todecide final procedures. Make anyneeded changes to your plan.1. What will you measure to

determine the effect of theDidinium on Paramecium? Ifyou count Paramecia, will youcount all you can see in thefield of vision of the micro-


1. Analyzing Data What differ-ences did you observe among theexperimental groups? Were thesedifferences due to the presence ofDidinium? Explain.

2. Drawing Conclusions Did theParamecium die out in any cul-ture? Why or why not?

3. Checking Your Hypothesis Wasyour hypothesis supported byyour data? If not, suggest a newhypothesis.

4. Thinking Critically List severalways that your methods may have

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

scope at a certain power? Willyou have multiple trials? If so,how many?

2. What single factor will youvary? For example, will you putno Didinium in one culture ofParamecium and 5 mL ofDidinium culture in anotherculture of Paramecium?

3. How long will you observe thepopulations?

4. How will you estimate thechanges in the populations ofParamecium and Didinium dur-ing the experiment?

5. Your teacher must approveyour plan before you proceed.

6. Carry out your experiment.7. Make a data table that has

Date, Number of Paramecium,and Number of Didiniumacross the top. Place the dataobtained for each culture inrows. Design and complete agraph of your data.

affected the outcome of theexperiment.

Going FurtherGoing Further

Project Based on this lab experience, designanother experiment that would help youanswer any questions that arose from yourwork. What factors might you allow to vary ifyou kept the number of Didinium constant?

To find out more aboutpopulation biology, visit

the Glencoe Science Web Site.www.glencoe.com/sec/science

A Didinium capturesa Paramecium.

YOUR OWNDESIGN

YOUR OWNDESIGN

1. Only cultures containingboth Didinium and Parame-cium showed a decline innumbers after a period oftime. This difference was dueto the presence of Didiniumbecause they preyed upon theParamecium.

2. Paramecium died out in themixed culture. They werepreyed upon by Didinium.

3. In most cases, hypotheses willbe supported.

4. The list may include: count-ing errors, too few samples,or cultures becoming con-taminated or being affectedby temperature.

Error AnalysisThe amount of initial culture ofthe two species should be equaland can be quantified by premea-suring the volume in the pipettes.

Skill Ask students to pre-pare a summary of this experi-ment in their journals. Use thePerformance Task AssessmentList for Writing in Science inPASC, p. 87. L2

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ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

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with no predators added. Food will have tobe added to these cultures. Use one alfalfapill (available from pharmacies) per liter ofwater. Note: If one culture receives food, allcultures must receive food to maintain con-trol conditions.

Data and ObservationsDepending on the experiment, data andobservations will vary. Typically, when thepopulations are mixed together, both willinitially increase in number. A decrease inprey will then be detected as the predatorpopulation feeds upon them, with a finaldrop in the population of predators as theirfood supply runs out.

Going FurtherGoing Further

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How can one populationaffect another?

W hy don’t prey populations disappear when predators are present?Prey organisms have evolved a variety of defenses to avoid being

eaten. For example, some caterpillars are distasteful to birds, and somefishes confuse predators by appearing to have eyes at both ends of theirbodies. Just as prey have evolved defenses to avoid predators, predators have evolved mechanisms to overcome those defenses.

Even single-celled protists such as Paramecium have predators. Didinium is another unicellular protist that attacks and devours Paramecium larger than itself. Do populations of Paramecium change when a population of Didinium is present? In this investigation, you will use various methods to determine how both of these species interact.

YOUR OWNDESIGN

YOUR OWNDESIGN

■ Use appropriate variables, con-stants, and controls in experimentaldesign.

Possible Materialsmicroscopemicroscope slidescoverslipsculture of Didiniumculture of Parameciumbeakers or jarseyedropperssterile pond water

Safety PrecautionsTake care when using electrical

equipment. Always use goggles in thelab. Handle slides and coverslipscarefully. Dispose of broken glass in acontainer provided by your teacher.

Skill HandbookUse the Skill Handbook if you need

additional help with this lab.

PREPARATIONPREPARATION

ProblemHow does a population of

Paramecium react to a population ofDidinium?

HypothesesHave your group agree on an

hypothesis to be tested. Record yourhypothesis.

ObjectivesIn this BioLab, you will:■ Design an experiment to establish

the relationships betweenParamecium and Didinium.

Didinium

Paramecium

YOUR OWNDESIGN

YOUR OWNDESIGN

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Time Allotment Initial preparation: one class ses-sion; ten-minute sessions for oneto two weeks every other day.

Process Skillsobserve, record and analyze data,design an experiment, separateand control variables

Safety PrecautionsUse oven mitts when handlinghot, sterile pond water. Have stu-dents wash their hands after thelab.

Alternative Materials■ Artificial pond water, called

Chalkey’s solution, may beprepared as follows. Dissolve 1g sodium chloride, with 0.04 gpotassium chloride, and 0.06 gcalcium chloride in 1 L of dis-tilled water. Dilute the pre-pared solution by adding 100mL of solution to 900 mL ofdistilled water.

■ To prepare sterile pond water,filter the water and place it inflat pans. Boil for 15 minutes.Allow to cool before using.

Possible HypothesesIn general, if a predator popula-tion is added to a prey popula-tion, the size of the predatorpopulation will increase while theprey population decreases.

However, if a small predatorpopulation is added to a largeprey population, no observabledifference will occur in the sizesof the populations.

PREPARATIONPREPARATION

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Teaching Strategies■ A lower magnification provides a widerfield of view, making counting easier.■ Methyl cellulose, available from supplyhouses, may be used to slow the protozoans.

Troubleshooting■ Cover or stack culture dishes to prevent

drying out.

■ Have students examine unmixed culturesfirst so they can later distinguish betweenParamecium and Didinium.

■ Suggest that several low-power fieldcounts be made and an average of thesecounts be used in the data tables.

Possible ProceduresControls will consist of Paramecium cultures


BioLab and MiniLab Work-sheets, p. 11 L2

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Chapter 2 AssessmentChapter 2 Assessment

SUMMARYSUMMARY

Section 2.1

Section 2.2

Main Ideas■ Natural history, the observation of how organ-

isms live out their lives in nature, led to thedevelopment of the science of ecology—thestudy of the interactions of organisms with oneanother and with their environments.

■ Ecologists classify and study the biological levelsof organization from the individual up to theecosystem. Ecologists study the abiotic and bioticfactors that are a part of an organism’s habitat.They investigate the strategies an organism usesto exist in its niche. An aspect of its niche mayinvolve symbiosis with other organisms.

Vocabularyabiotic factor (p. 39)biosphere (p. 38)biotic factor (p. 40)commensalism (p. 46)community (p. 42)ecology (p. 38)ecosystem (p. 43)habitat (p. 44)mutualism (p. 46)niche (p. 45)parasitism (p. 47)population (p. 42)symbiosis (p. 46)

■ Autotrophs, such as plants, make nutrients thatcan be used by the plants and by heterotrophs.Heterotrophs include herbivores, carnivores,omnivores, and decomposers.

■ Food chains are simple models that show oneway that materials move from autotrophs toheterotrophs and eventually to decomposers.

■ Food webs represent many interconnected foodchains and illustrate possible ways materials aretransferred within an ecosystem. Energy fromthe sun fuels life in the ecosystems. Althoughthe sun adds new energy, the materials of life,such as carbon and nitrogen, do not increase.These materials are used and reused as theycycle through the ecosystem.

Vocabularyautotroph (p. 48)decomposer (p. 50)food chain (p. 51)food web (p. 52)heterotroph (p. 49)scavenger (p. 49)trophic level (p. 52)

Nutrition andEnergy Flow

CHAPTER 2 ASSESSMENT 63

1. Which of the following would be abiotic fac-tors for a polar bear?a. extreme cold, floating iceb. eating only live preyc. large body sized. paws with thick hair

2. Organisms that use the sun’s energy to makefood are called ________.a. herbivores c. autotrophsb. animals d. heterotrophs

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS 3. In the food web below, which of the organ-isms, X, Y, or Z, is a herbivore?a. Z c. both X and Yb. Y d. X

Organisms and TheirEnvironment

Grass

X Grasshopper

Y Z

63

Main IdeasSummary statements can be used bystudents to review the major con-cepts of the chapter.

Using the VocabularyTo reinforce chapter vocabulary, usethe Content Mastery Booklet andthe activities in the Interactive Tutorfor Biology: The Dynamics of Life onthe Glencoe Science Web Site.www.glencoe.com/sec/science

1. a2. c3. d

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS


All ChapterAssessment

questions and answers have beenvalidated for accuracy and suitabil-ity by The Princeton Review.

Resource ManagerResource ManagerChapter Assessment, pp. 7-12MindJogger VideoquizzesComputer Test BankBDOL Interactive CD-ROM, Chapter

2 quiz

This subtropical region receives between 100and 165 cm (40-65 inches) of rain each year,

but only during the rainy season, which lastsfrom May to October. The heavy rainfall causesshallow Lake Okeechobee to overflow. A wide,thin sheet of water spreads out from the lake,creating an extensive marshy area.

Early in the twentieth century, the slow-mov-ing river that flows out of Lake Okeechobee was80 km (50 miles) wide in some places, and only15-90 cm (six inches to three feet) deep. Thiswetland teemed with fishes, amphibians, andother animals that fed millions of wading birds.Healthy populations of crocodiles, alligators, andother large animals also lived here. During thedry season, from December to April, water levelsin the marshes gradually dropped. Fishes andother water dwellers moved into deeper poolsthat held water all year long.

Changing the Everglades Water from LakeOkeechobee is no longer allowed to flood thecountryside. Instead, it is diverted into channelsto create dry land for agriculture and homes, and

stored behind levees to supply water for cities. Asa result, half the acreage of the original Evergladeshas been drained. Habitats have disappeared.

Different ViewpointsEverglades National Park was established to

preserve a portion of the Everglades. But the landthat forms the park is an island surrounded byfarms and towns and cut off from the waters ofLake Okeechobee. Human needs determine howmuch water comes into the park. When reservesare low, water is held back for people to use,depriving Everglades habitats of the moisture theyneed. If floods threaten, large amounts of waterare released quickly. These sudden flows destroythe nests of wading birds and other animals.

Restoring the Everglades In 1993, Floridadeveloped a restoration plan for rescuing theEverglades. The goals of the plan are to restore,as much as possible, the natural flow of unpol-luted water through the area, recover nativehabitats and species, and create a sustainableecosystem that permits both humans and nativespecies to flourish.

The Florida Everglades—An Ecosystem at RiskThe Florida Everglades ecosystem covers the southern portion of theFlorida peninsula. As with any wetlands, water is the critical factorthat defines the ecology of the area.

INVESTIGATING THE ISSUEINVESTIGATING THE ISSUEATLANTICOCEAN

LakeOkeechobee

EvergladesNational Park

Florida

Big CypressNational Parks

Analyzing the Issue When EvergladesNational Park was established, scientists andgovernment officials believed a portion of theEverglades ecosystem could be preserved bydrawing boundaries around it and declaring it off limits to development. Why did thisapproach fail to preserve the Everglades?

To find out more about theEverglades, visit the Glencoe

Science Web Site. www.glencoe.com/sec/science

The map (above) shows the loca-tion of the Everglades (inset).

62

Purpose Students gain an understandingof the complexity of ecosystemsand learn some ways in whichhuman activities can affect theenvironment.

BackgroundEverglades water that flows allthe way to the Gulf coast carrieswith it nutrients that support thegrowth of mangrove swamps andsea grass beds. These two estuar-ine communities feed and shelteryoung fish, shellfish, and otherimportant links in the marinefood chain. Changes in the waterflow of the area sometimes resultin the discharge of large amountsof freshwater into Florida Bay,changing the salinity of the waterand endangering the health ofmangroves and sea grass.Pollutants and excessive amountsof fresh water may also be endan-gering the coral reefs off theFlorida coast.

Teaching StrategiesAfter students have completedthe reading, invite them to dis-cuss issues involved in balancingthe needs of both human andwildlife populations. Point outthat one of the main reasons whysouth Florida’s human populationhas increased over the past 100years is the strong attraction ofthe Everglades. Also, manyFlorida residents work in thetourism industry, and theEverglades brings large numbersof tourists to the state.

Investigating the IssueThe park was cut off from itswater source. Even though landand wildlife inside the park wereprotected from development, notenough clean water was providedto keep the park healthy.

L2

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Going FurtherGoing FurtherGoing Further

Naturalist Everglades habitats includesea grass beds, coastal prairies, man-

grove swamps, freshwater sloughs, marlprairies, hammocks, and pinelands. Invitestudents to find out what kinds of environ-mental conditions characterize one or moreof these habitats and what kinds of organisms live there. L3

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VIDEODISCSTV: Water, Water ManagementUnit 3, Side 1, 3 min. 9 sec.

Everglades

VIDEOTAPEMindJogger Videoquizzes

Chapter 2: Principles of EcologyHave students work in groups as they playthe videoquiz game to review key chapterconcepts.


The Everglades (Ch. 6)Disc 1, Side 1, 29 sec.!7hÑ"

!;XRV'86"




CHAPTER 2 ASSESSMENT 65

19. Plants absorb ________ from the air, and withthe sun’s light energy they make high-energycarbon molecules.

20. Lightning and bacteria act to move and con-vert ________ from the air into compounds inthe soil that can be readily used by plants.

21. Explain how pesticides sprayed on the waterin a wetland ecosystem could affect a differ-ent ecosystem.

22. Sloths are slow-moving herbivores that havealgae growing in their fur. Caterpillars of cer-tain kinds of moths eat the algae. Birds eat themoths. Using this example, draw a food chainand describe one symbiotic relationship.

23. Sequencing Place the following organismsin correct order in a food chain: mouse,hawk, wheat, snake.

24. Sequencing Describe one example of feed-ing relationships that cycle matter through anecosystem.

25. Concept Mapping Complete the conceptmap by using the following vocabulary terms:autotrophs, decomposers, food webs, heterotrophs.

THINKING CRITICALLYTHINKING CRITICALLY

APPLYING MAIN IDEASAPPLYING MAIN IDEAS

ASSESSING KNOWLEDGE & SKILLSASSESSING KNOWLEDGE & SKILLS

The graph below compares the growth ratesof two organisms when grown together andwhen grown separately.

Interpreting Data Use the graph and infor-mation to answer the following questions.1. When grown separately, approximately

how long after the extinction ofOrganism 2 did it take the population ofOrganism 1 to reach its highest point?a. 3 days c. 3 weeksb. 1 week d. 5 weeks

2. When the organisms were growntogether, what was the approximate rateof growth between weeks 2 and 6?a. 75 per week c. 50 per weekb. 100 per month d. 25 per day

3. Observing and Inferring From thedata, it is clear that the associationbetween the organisms is ________.a. commensalism c. mutualism b. parasitism d. socialism

4. Hypothesizing Describe one possiblebenefit that Organism 2 gets from itsassociation with Organism 1. Explain a possible reason why the associationlowers the population of Organism 1.

Num

ber p

rese

nt in

hun

dred

s

Time in weeks

Organism #1 and #2

grown together

Organism #1 alone

Organism #2 alone

1 2 3 4 5 6 7

1

2

3

4

5

Growth Rates of Two Organisms

For additional review, use the assessmentoptions for this chapter found on the Biology: TheDynamics of Life Interactive CD-ROM and on theGlencoe Science Web Site.www.glencoe.com/sec/science

CD-ROM

show interactions between

2.

1.

such as

3.

4.

65

23. wheat ⇒ mouse ⇒ snake ⇒hawk

24. There are a variety of accept-able answers such as the follow-ing. Plants provide nitrogen toanimals that eat the plants.Bacteria and other decomposersrelease nitrogen and carbondioxide when they feed upondecaying organisms. Animalsobtain carbon when eatingother organisms.

25. 1. food webs 2. autotrophs 3.heterotrophs 4. decomposers

THINKING CRITICALLYTHINKING CRITICALLY

Chapter 2 AssessmentChapter 2 AssessmentChapter 2 AssessmentChapter 2 Assessment

4. Which organism is a carnivore?a. human c. lionb. rabbit d. opossum

5. Biotic factors in a wetland community mightinclude ________.a. water c. temperatureb. crayfishes d. soil type

6. Which of the following would decrease theamount of carbon dioxide in the air?a. a maple tree growingb. a dog runningc. a person driving a car to workd. a forest burning

7. As energy flows through an ecosystem,energy ________ at each trophic level.a. remains the sameb. increasesc. decreases then increasesd. decreases

8. An elk eats grass. A grizzly bear eats the elk.This is an example of a ________.a. pyramid of numbersb. commensal relationshipc. food webd. food chain

9. Which of the following is true concerning theflow of energy and matter in an ecosystem?a. Both energy and matter are recycled and

used again.b. Matter is recycled and used again, energy

is lost.c. Energy is recycled and used again, matter

is lost.d. Neither energy nor matter are recycled

and used again.

10. Cowbirds get their namebecause they follow cows and eat the insects disturbed by the walk-ing cows. Cowbirdshave an unusual methodfor reproducing. Thebrown-headed cowbird goesto the nest of a different birdspecies, such as the red-wing blackbird. Thecowbird rolls one of the blackbird’s eggs outof the nest and lays its own egg in place. Theblackbird protects the cowbird egg and feedsthe chick when it hatches. This descriptionbest describes part of the cowbird’s ________.a. community c. nicheb. habitat d. tropic level

11. For the cowbird description in question 10,the symbiotic relationship between the cowand the cowbird is ________. The associationbetween the cowbird and the blackbird is a(n)________ relationship.

12. The presence of predators, prey, and para-sites are examples of ________ factors in anorganism’s habitat.

13. A close and permanent relationship betweentwo organisms is called ________. If bothorganisms benefit it is ________.

14. A group of organisms of the same species living in the same area is called a(n) ________.When the group includes different species, it is called a ________.

15. A(n) ________ eats both plants and animals.A(n) ________ eats only plants.

16. A(n) ________ chain is a model of how matterand energy pass through organisms. Eachorganism is at a different ________ level.

17. ________ is a branch of biology that studiesthe interactions of organisms and their envi-ronment.

18. An ecological pyramid that shows the amountof energy for different trophic levels is calleda(n) ________. If it shows how many organ-isms are at each tropic level, it is called a(n)________.

64 CHAPTER 2 ASSESSMENT

TEST–TAKING TIPTEST–TAKING TIP

Quiet ZoneIt’s best to study in an environment similar to theone in which you’ll be tested. Blaring stereos,video game machines, chatty friends, and beepersare NOT allowed in the classroom during testtime. So why get used to them?

64

4. c5. b6. a7. d8. d9. b

10. c11. commensalism, parasitic12. biotic13. symbiosis, mutualism14. population, community15. omnivore, herbivore16. food, trophic17. Ecology18. pyramid of energy, pyramid of

numbers19. carbon dioxide20. nitrogen

21. The pesticide may be carried inthe water to other bodies ofwater or may be carried fromone organism to another.

22. Algae ⇒ Caterpillar/Moth ⇒Bird. The symbiotic relationshipbetween the algae and thesloth is commensal because thealgae have a place to growundisturbed, while the sloth isneither helped nor harmed.

APPLYING MAIN IDEASAPPLYING MAIN IDEAS


1. c 2. a3. b4. Organism #2 most likely

benefits by obtainingnutrients from Organism#1. Other possible bene-fits include anything thathelps Organism #2 satisfyits needs. The populationsize of Organism #1 isprobably lowered becauseOrganism #1 is weakenedand cannot grow orreproduce as quickly. Theinteractions of the speciesmay also cause moredeaths in the populationof Organism #1.


unit 2 ecology advance planning - temecula valley unified ......2. compare the different levels of...

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