What You’ll Learn■ You will explain the impor-

tance of biological diversity.■ You will distinguish environ-

mental changes that mayresult in the loss of species.

■ You will describe the work ofconservation biologists.

Why It’s ImportantWhen all the members of aspecies die, that species is goneforever. Knowledge of biologicaldiversity leads to strategies toprotect the permanent loss ofspecies from Earth.

Biological Diversity and Conservation

Biological Diversity and Conservation

Michio Hoshino/Minden Pictures

Visit to • study the entire chapter

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information and activities onbiological diversity and conservation

• review content with theInteractive Tutor and self-check quizzes

In the tundra in the fall, carpetsof brilliant red bearberry plantsstretch for miles in all directions.These plants, along with dwarfblueberries, crowberry, and bogrosemary, are some of the pro-ducers on which tundra animalsdepend. The tundra ecosystemwould change significantly ifthis selection of plants were todisappear. The other plantlikeorganisms shown are varieties ofreindeer lichen.

Understandingthe Photo

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110

Vanishing Species5.1

Biological DiversityA rain forest has a greater amount of biological diversity, or biodiver-

sity, than a cornfield. Biodiversity refers to the variety of species in a spe-cific area. The simplest and most common measure of biodiversity is thenumber of different species that live in a certain area. For example, ahectare of farmland, like the one in Figure 5.1B, is dominated by onespecies of plant—corn. In contrast, one hectare of a rain forest may con-

tain 400 species of plants. The cornfield also may containhundreds of species of insects and several species of birds,but the rain forest may have thousands of species of insectsand hundreds of species of birds.

Where is biodiversity found?Areas around the world differ in biodiversity.

A hectare of tropical rain forest in AmazonianPeru may have 300 tree species, while onehectare of temperate deciduous forest in the United States is more likely to have only 30 tree species. Therefore, the tropical rain forest has more biodiver-sity. Biodiversity increases as you movetoward the equator. Tropical regions con-

tain two-thirds of all land species on Earth.

SECTION PREVIEWObjectivesExplain biodiversity andits importance.Relate various threats tothe loss of biodiversity.

Review Vocabularyhabitat: the place where

an organism lives out itslife (p. 42)

New Vocabularybiodiversityextinctionendangered speciesthreatened specieshabitat fragmentationedge effecthabitat degradationacid precipitationozone layerexotic species

Read for Main Ideas Write a definition of biodiversity in the center column. Then, as you read Chapter 5, list factors that make biodiversity important in the left column, and list threats to biodiversity in the right column.

Biodiversity Make the following Foldable to help you identify main ideas about biodiversity.

Fold the top of a vertical piece of paper down and the bottom up to divide the paper into thirds.

Turn the paper horizontally. Unfold and label the three columns as shown.

STEP 1 STEP 2

Biodiversity Threats to

Biodiversity

Importanceof

Biodiversity

5.1 VANISHING SPECIES 111(l)Gary Gray/DRK Photo, (r)Envision/B.W. Hoffman

Figure 5.1A temperate rain forest in Washingtonstate (A) and a corn-field (B) have differentbiodiversities. AA

BB

The richest environments for biodiver-sity all seem to be warm places: tropicalrain forests, coral reefs, and large tropical lakes. Learn one way to mea-sure species diversity in the MiniLab onthis page.

Studying biodiversityHow do ecologists perform experi-

ments related to biodiversity? Thestudy of islands has led to an under-standing of factors that influence biodiversity. In the 1960s, an investi-gation was devised for testing the development of biodiversity onislands. The scientists thought thatusing a miniaturized situation such asvery small islands would help them seeclearly what changes take place whenorganisms move into or out of a defined area. To do this, the scien-tists selected some small islands ofmangrove trees off the coast ofFlorida like those in Figure 5.2. Theycounted the number of insect and spi-der species that were on each island,and then removed all the existingspecies from the islands except for thetrees. Then they observed the follow-ing as organisms moved back onto theislands. 1. Insects and spiders returned first.2. The farther away the island was

from the source of the new species(the mainland), the longer it tookfor the island to be recolonized.

3. Eventually, the islands had aboutthe same number of species thatthey had originally, but the makeupof the community was now differ-ent from the original community.The scientists also saw that the

larger the island, the more habitatsand species it seemed to have, imply-ing that the number of speciesdepends on the number of habitats.

Research like this is not simple to do. Today you can read about projects in rain forests that require

112 BIOLOGICAL DIVERSITY AND CONSERVATION

Measure Species DiversityField InvestigationIndex of diversity (I.D.) isa mathematical way ofexpressing the biodiver-sity and species distribu-tion in a community. Asyou collect data, takecare not to disturb theenvironment.

Procedure ! Copy the data table below.@ Survey a city block or an area designated by your teacher

and in your data table, record the number of differentspecies of trees present.

# Survey the area again. This time, make a list of the treesby assigning each a number as you walk by it. Place an Xunder Tree 1 on your list. If Tree 2 is the same species asTree 1, mark an X below it. Continue to mark an X underthe trees as long as the species is the same as the previousone. When a different species is encountered, mark an Ounder that tree on your list. Continue to mark an O if thenext tree is the same species as the previous. If the nexttree is different, mark an X.

$ Record in your data table: a. the number of “runs.” Runs are represented by a group

of similar symbols in a row. Example: XXOOOXOwould be 4 runs (XX � first run, OOO � second run, X � third run, O � fourth run).

b. the total number of trees counted.% Calculate the I.D. using the formula in the data table.

Analysis1. Analyze Trends from Data Compare how your tree I.D.

might compare with that of a vacant lot and with that ofa grass lawn. Explain.

2. Make Inferences from Data Would it be best to have arelatively low I.D. or high I.D. for an environment? Explainyour answer.

Index of Diversity

Number of species �

Number of runs �

Number of trees �

Index of diversity � Number of species � number of runs

Number of trees

A tree-lined street

Envision/George Mattei

scientists to work 150 meters up inthe canopy while they collect speciesthat live only at that level. Otherresearchers catalogue the organismsthat live in coral reefs, and othersattach radio collars to deer. Still otherswork in laboratories comparing theDNA of members of isolated popula-tions to see how or if these populationsmight be changing.

Importance ofBiodiversity

Compare a parking lot covered withasphalt to your favorite place in nature,perhaps your backyard, a wooded area,or a local lake. You might go to an arealike this to relax or to think. Artists getinspiration from these areas for songs,paintings, photographs, and literature.Looking at one of Art Wolfe’s photo-graphs in the Connection to Art on page128 can help you appreciate the beautybiodiversity gives our world. Beyondbeauty, why is biodiversity important?

Importance to natureLiving things are interdependent.

Animals could not exist without

green plants. Many flowering plantscould not exist without animals topollinate them. Plants are depen-dent on decomposers that breakdown dead or decaying material intonutrients they can absorb. In a rainforest, a tree grows from nutrientsreleased by decomposers. A slotheats the leaves of the tree. Mossgrows on the back of the sloth.Thus, living things can be niches forother living things.

Populations are adapted to livetogether in communities. Althoughecologists have studied many complexrelationships among organisms, manyrelationships are yet to be discovered.Scientists do know that if a species islost from an ecosystem, the loss mayhave consequences for other livingthings in the area. An organism sufferswhen a plant or animal it feeds upon isremoved permanently from a foodchain or food web. A population maysoon exceed the area’s carrying capacityif its predators are removed. If thesymbiotic relationships among organ-isms are broken due to the loss of onespecies, then the remaining species willalso be affected.

5.1 VANISHING SPECIES 113Norm Thomas/Photo Researchers

Figure 5.2Size may be an impor-tant factor in the level ofbiodiversity that anisland can support.Research on red man-grove islets off the coastof Florida showed thatthe larger the island, thegreater its biodiversity.

114 BIOLOGICAL DIVERSITY AND CONSERVATION(l)Tom & Pat Leeson/Photo Researchers, (c)Patti Murray/Earth Scenes, (r)Don & Pat Valenti/DRK Photo

Willow bark was theoriginal source of aspirin.

C

Taxol, a strong anti-cancer drug, wasfirst discovered inthe Pacific yew.

A

Rosy periwinkle is the sourceof drugs for Hodgkin’sdisease and leukemia.

B

Biodiversity brings stabilityBiodiversity can bring stability to an

ecosystem. A pest could easily destroyall the corn in a farmer’s field, but itwould be far more difficult for a singletype of insect or disease to destroy all individuals of a plant species in arain forest. There, instead of beingclumped together, the plants exist scat-tered in many parts of the rain forest,making it more difficult for the diseaseorganism to spread. In summary,ecosystems are stable if their biodiver-sity is maintained. A change in speciescan destabilize them.

Importance to peopleHumans depend on other organisms

for their needs. Oxygen, on which ani-mals depend, is supplied, and carbondioxide is removed from the air bydiverse species of plants and algae liv-ing in a variety of ecosystems through-out the world. Beef, chicken, tuna,shrimp, and pork are a few of the meatsand seafood humans eat. Think of allthe plant products that people eat,from almonds to zucchini. Yet only afew species of plants and animals sup-ply the major portion of the food eaten

by the human population. Biodiversitycould help breeders produce additionalfood crops. For example, throughcrossbreeding with a wild plant, a foodcrop might be made pest-resistant ordrought-tolerant. People also rely onthe living world for raw materials usedin clothes, furniture, and buildings.

Another important reason formaintaining biodiversity is that it canbe used to improve people’s health.Living things supply the world phar-macy. Although drug companies man-ufacture synthetic drugs, activecompounds in these drugs are usuallyfirst isolated from living things, suchas those in Figure 5.3. The antibioticpenicillin came from the moldPenicillium. The antimalarial drugquinine came from the bark of thecinchona tree. Even the importanceof soil microorganisms should not beoverlooked. The drug cyclosporine,which prevents rejection of trans-planted organs, was discovered in asoil fungus in 1971. Preserving biodi-versity ensures there will be a supplyof living things, some of which mayprovide future drugs. Will a cure forcancer or HIV be found in the leavesof an obscure rain forest plant?

Figure 5.3Biodiversity provides thebasis for many importantmedical drugs.

5.1 VANISHING SPECIES 115

Loss of BiodiversityHave you ever seen a flock of passen-

ger pigeons? How about a blue pike, or a dusky seaside sparrow? Unless you have seen a photograph or a speci-men in a museum, your answer will be “No” to each of these questions. These animals are extinct. Extinction(ek STINGK shun) is the disappearanceof a species when the last of its mem-bers dies. Extinction is a natural processand Earth has experienced several massextinctions during its history. There isalso a certain level of natural extinction,called background extinction, that goeson. Scientists estimate that backgroundextinction accounts for the loss of onespecies per year per million species.However, the current rate of extinctionexceeds that by many times. Scientistshypothesize that this rise is due in partto the needs of the expanding humanpopulation, habitat loss, and landexploitation. Is there evidence of a linkbetween land use and species extinc-tion? Look at one scientist’s analysis inthe Problem-Solving Lab on this page.

A species is considered to be anendangered species when its numbersbecome so low that extinction is possi-ble. Figure 5.4 shows species listed asendangered in the United States.

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In 1982, the California condor (Gymnogyps californianus) was nearly extinct in the wild. The 22 remaining condors were captured and placedin reserves. As of 2002, morethan 70 birds were released to the wild. They remainendangered.

A

Figure 5.4In the United States, scientists have developed programs designed to save some endangered species.

The Endangered Species list includes several speciesof sea turtles.

B

Relationship of Land Area to Extinctions

Area in Initial Number PercentIsland km2 of Species Extinctions of Loss

Borneo 751 709 153 30 20

Java 126 806 113 39 35

Bali 5443 66 47 71

115

Interpret DataDoes species extinction correlate to land area? Speciesare at risk of extinction when their habitats are destroyed. Is there a better chance for survival when land area is large?

Solve the ProblemA study of land mammals was conducted by a scientist todetermine the effect of land area on species extinction. Hisresearch was confined to a group of South Pacific islands ofIndonesia. The scientist’s basis for determining the initial num-ber of species present was based on research conducted byearlier scientists and from fossil evidence.

Thinking Critically1. Evaluate Trends from Data From the data, what is the

relationship between island size and the initial number ofspecies?

2. Analyze Trends from Data From the data, how does landarea seem to correlate with loss of species?

3. Analyze Scientific Explanations Hypothesize why thestudy was conducted on only land mammals. What mightbe some strengths and weaknesses of this research?

When the population of a species islikely to become endangered, it is saidto be a threatened species. Africanelephants, for example, are listed as athreatened species. In 1979, the esti-mated wild elephant population wasabout 1.3 million. Twenty years later,the population was estimated to be 700000. In 1998, a survey published by theAfrican Elephant Database estimated aminimum number of elephants atabout 300 000. The United States Fishand Wildlife Service maintains a listingof threatened and endangered speciesfor the United States and the world.Figure 5.5 shows the type of informa-tion available from the Fish andWildlife Service on its Threatened andEndangered Species System database.

Explain why bio-diversity is important.

Threats to BiodiversityComplex interactions among spe-

cies make each ecosystem unique.The species there are usually welladapted to their habitats. Changes to habitats can therefore threatenorganisms with extinction. What aresome of the activities that can bringthis about?

Habitat loss

One of the biggest reasons fordecline in biodiversity is habitat loss.In the 1970s and 1980s, in theAmazonian rain forest, thousands ofhectares of land were cleared in aneffort to create farmland and to sup-ply firewood. Much of this land lostits usefulness for agriculture afteronly a few years because rain forestsoil by itself has little or no usefulnutrient supply. Clearing the land

erased habitats that will not bereestablished easily. Withoutthese habitats, certain plants andanimals become vulnerable toextinction.

Other areas affected by habi-tat loss are coral reefs. Coralreefs, like the one in Figure 5.6,are thought to be similar to trop-ical rain forests in biodiversityrichness. The structure of coralprovides habitats for varieties of fish, anemones, sponges, andother marine organisms. Diseaseand changes in water tempera-ture can damage or kill coral. Asa result, habitats are lost and theorganisms that depend on thecoral also are affected.

Steve Wolper/DRK Photo

Results of Species Search*

Scientific Name Common Name Group Listing Status Current Range

Loxodonta africana African elephant Mammals T Africa

Figure 5.5Through the Fish andWildlife Service, infor-mation is available tothe public on all speciesthreatened or endan-gered. T, under ListingStatus, refers to threat-ened. An E would indi-cate endangered.

*U.S. Fish & Wildlife Service Threatened and Endangered Species System (TESS)

Figure 5.6Coral reefs are rich inbiodiversity. ConcludeHow does removal ofcoral result in a lossof habitat for reeforganisms?

116

Habitat fragmentation

Habitat fragmentation is the sep-aration of wilderness areas from otherwilderness areas. Habitat fragmenta-tion has been found to contribute to:• increased extinction of local species.• disruption of ecological processes.• new opportunities for invasions by

introduced or exotic species.• increased risk of fire.• changes in local climate.Fragmented areas are similar toislands. The smaller the fragment, theless biodiversity the area can support.This is because, as species migratefrom an area that has become unsuit-able for some reason, other speciesthat depend on the migrating individ-uals lose their life support. As a result,overall species diversity declines.

Geographic isolation can lead togenetic isolation. When an individualorganism’s habitat becomes too small,its population becomes isolated fromother populations of its species. Theorganism doesn’t have the chance tobreed with members of its species inother populations.

Habitat fragmentation, as shown inFigure 5.7, presents problems fororganisms that need large areas togather food or find mates. Large pred-ators may not be able to obtainenough food if restricted to too smallan area. Habitat fragmentation also

makes it difficult for species to re-establish themselves in an area.Imagine a small fragment of forestwhere a species of salamander lives. Afast-burning fire started by lightningdestroys trees and the salamanders liv-ing there. In a nonfragmented forest,as the area recovers, new salamanderswould eventually move into the area.However, if the burned forest was iso-lated from another forest where othersalamanders live, no route would existfor these salamanders to reestablishpopulations in the burned area. In thenext section of this chapter, read aboutcorridors that connect one piece offragmented land to another.

Edge Effect The edge of a habitat or ecosystem

is where one habitat or ecosystemmeets another. This can be where aforest meets a field, where watermeets land, or where a road cutsthrough a field or wooded area. Thedifferent conditions along the bound-aries of an ecosystem are called edgeeffects. An edge may have two differ-ent sets of abiotic factors. Edges tendto have greater biodiversity becausedifferent habitats with differentspecies are brought together. Whenan edge changes, animals from onearea might migrate from the area or move to the new edge, thereby

5.1 VANISHING SPECIES 117Michael Fredericks Jr. /Animals Animals

Figure 5.7Wildlife areas that arebroken up or surrounded by development result inhabitat fragmentation.The areas remaining maybe too small to supportreproducing populations.The pathway from onehabitat to another may becut off or greatly reducedin size.

bringing species from different ecosys-tems in contact with one another. If apiece of land is cleared or divided by aroad, new edges are created. Thisaction may expose animals attracted tothe edge to more predators than theywere previously.

What happens at the edge of ahabitat may affect what goes on in theinterior of the area. In a developedarea, there may be more housecats,and therefore, birds that nestedundisturbed in the area before may bepreyed upon.

Habitat degradationAnother threat to biodiversity is

habitat degradation, the damage to ahabitat by pollution. Three types ofpollution are air, water, and land pol-lution. Air pollution can cause breath-ing problems and irritate membranesin the eyes and nose. Pollutants enterthe atmosphere in many ways—including volcanic eruptions and for-est fires. Burning fossil fuels is also amajor source of air pollutants such assulfur dioxide.

Acid precipitation—rain, snow,sleet, and fog with low pH values—has been linked to the deterioration

of some forests and lakes. Sulfur diox-ide from coal-burning factories andnitrogen oxides from automobileexhaust combine with water vapor inthe air to form acidic droplets ofwater vapor. When these droplets fallfrom the sky, the moisture leachescalcium, potassium, and other nutri-ents from the soil. This loss of nutri-ents can lead to the death of trees.Acid precipitation also damages planttissues and interferes with plantgrowth. Worldwide, many trees suchas those shown in Figure 5.8 aredying and acid rain and fog arethought to be the cause. Acid precip-itation also is linked to degrading lakeecosystems. When acid rain falls into alake, or enters as runoff from streams,the pH of the lake water falls.

Ultraviolet waves emitted by theSun also can cause damage to livingorganisms. Ozone, a compound con-sisting of three oxygen atoms, isfound mainly in a region of Earth’satmosphere between about 15 km and35 km altitude. The ozone in thisregion—known as the ozone layer—absorbs some of the ultraviolet wavesstriking the atmosphere, reducing theultraviolet radiation reaching Earth’ssurface. Over some parts of Antarc-tica, the amount of ozone overhead isreduced by as much as 60 percentduring the Antarctic spring. Ozoneamounts then increase during thesummer. This seasonal ozone reduc-tion is known as the Antarctic ozonehole, and is caused by the presence inthe atmosphere of human-producedchemicals such as chlorofluorocar-bons (CFCs). Smaller seasonal reduc-tions also have been observed overthe Arctic and there is a small down-ward trend in global ozone concentra-tions. However, the causes of thisozone loss and its biological conse-quences are still uncertain.

118 BIOLOGICAL DIVERSITY AND CONSERVATIONWill & Deni McIntyre/Photo Researchers

PhysicalScience

Connection

Environmentalimpact ofgeneratingelectricity Morethan 50% of theelectrical energyproduced in theUnited Statescomes fromburning coal.Compared to otherfossil fuels, coalcontains moreimpurities, such assulfur. As a result,more pollutants,such as sulfurdioxide, areproduced whencoal is burned thanwhen oil or naturalgas is burned.

Figure 5.8Acid precipitation andacid fog may be majorcontributors of damageto these trees.

Water pollutionWater pollution degrades aquatic

habitats in streams, rivers, lakes, andoceans. A variety of pollutants can affectaquatic life. Excess fertilizers and ani-mal wastes, as shown in Figure 5.9, areoften carried by rain into streams andlakes. The sudden availability ofnutrients causes algal blooms, theexcessive growth of algae. As the algaedie, they sink and decay, removingneeded oxygen from the water. Siltfrom eroded soils can also enter waterand clog the gills of fishes. Deter-gents, heavy metals, and industrialchemicals in runoff can cause death inaquatic organisms. Abandoned driftnets in oceans have been known toentangle and kill dolphins, whales,and other sea life.

Land pollutionHow much garbage does your

family produce every day? Trash, orsolid waste, is made up of the cans,bottles, paper, plastic, metals, dirt,

and spoiled food that people throwaway every day. The averageAmerican produces about 1.8 kg ofsolid waste daily. That’s a total ofabout 657 kg of waste per person peryear. At what rate does it decom-pose? Although some of it mightdecompose quickly, most trashbecomes part of the billions of tonsof solid waste that are buried inlandfills. Strict controls on thedesign, construction, and placementof landfills are meant to reduce con-tamination of groundwater supplies.

The use of pesticides and otherchemicals can also lead to habi-tat degradation. For many years,DDT was used liberally to controlinsects and to kill mosquito larvae.Birds that fed on DDT-treatedcrops, or insects, fish, and othersmall animals exposed to DDT, were observed to have high levels of DDT in their bodies. The DDTwas passed on in food chains to the predators that ate these animals.

5.1 VANISHING SPECIES 119(l)Doug Sokell/Tom Stack & Associates, (r)Matt Meadows

The cattle on this feedlot producenitrogen-rich liquid and solid wastes.Because of the volume of these wastes,research is ongoing as to how to makegood use of them.

A

Large amounts of phosphorus in runofffrom fertilized fields can stimulate therapid growth of algae in waterwaysdownstream. This lush growth consumesall or most of the oxygen in the water,making it impossible for insects, fishes,and other animals to live.

B

PhysicalScience

Connection

Wave energy Thesun emits radiantenergy that iscarried byelectromagneticwaves, such asinfrared, visiblelight andultraviolet waves.The energy carriedby electromagneticwaves increases astheir wavelengthdecreases.Ultraviolet waveshave shorterwavelengths thanvisible light andcarry moreenergy—enoughenergy to damageliving cells.

Figure 5.9Runoff from large feedlots and agricul-tural operations can contain largeamounts of nitrogen and phosphorus.

Understanding Main Ideas1. What are two reasons for a species to become

threatened or endangered?

2. Explain how land that gets broken up can contribute to loss of species diversity.

3. What is an edge effect? Explain how change in an ecosystem’s edges can affect organisms.

4. How can exotic species affect populations ofnative species?

Thinking Critically5. Explain the interactions in a tropical ecosystem

that enable it to have great biodiversity.

6. Recognize Cause and Effect Explain why wateris not subject to loss, but is subject to degrada-tion. How does water degradation affect biodiver-sity? For more help, refer to Recognize Cause andEffect in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

120 BIOLOGICAL DIVERSITY AND CONSERVATION(l)G. Carleton Ray/Photo Researchers, (r)Scott Camazine/Photo Researchers

Zebra mussels were introducedunintentionally into the Great Lakesfrom the ballast of ships. These fast-growing mussels clear the water, butblock many food chains.

B

Kudzu was introducedintentionally into the U.S. as anornamental and to reduce soilerosion. However, it grows rapidly,smothering areas of native plants.

A

Because of the DDT in their bodies,some species of predators, such asthe bald eagle and the peregrine fal-con, were found to lay eggs with verythin shells that cracked easily, killingthe chicks and leading to sharp pop-ulation declines. These observationscontributed to the ban on DDT inthe United States in 1972.

Exotic speciesPeople sometimes introduce a new

species into an ecosystem, either inten-tionally or unintentionally. Thesespecies can cause problems for thenative species. When people broughtgoats to Santa Catalina Island, locatedoff the coast of California, 48 nativespecies of plants soon disappearedfrom the local environment. Building

the Erie canal in the nineteenth century made it possible for the sealamprey to swim into the GreatLakes. The sea lamprey, whichresembles an eel, clamps onto a fish’sbody and, using its sharp teeth andtongue, sucks fluids out of the fish.The lamprey has totally eliminatedcertain fish species from some of theGreat Lakes. Exotic species, such asthe goat and the lamprey, are notnative to a particular area. Someother examples of exotic species are shown in Figure 5.10. Whenexotic species are introduced, thesespecies can grow at an exponentialrate due to the fact that they are notimmediately as vulnerable to localcompetitors or predators as are theestablished native species.

Figure 5.10Exotic species can cause many problemswhen introduced intonew ecosystems eitherintentionally or unintentionally.

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5.2SECTION PREVIEWObjectivesDescribe strategies usedin conservation biology.Relate success in protect-ing an endangered speciesto the methods used toprotect it.

Review Vocabularybiodiversity: the variety

and abundance of lifein an area (p. 111)

New Vocabularyconservation biologynatural resourceshabitat corridorssustainable usereintroduction programscaptivity

5.2 CONSERVATION OF BIODIVERSITY 121

Conservation BiologyConservation biology is the study and implementation of methods to

protect biodiversity. Effective conservation strategies are based on prin-ciples of ecology. These strategies include natural resource conservationand species conservation. Even soil has to be conserved. Learn aboutwhat can happen to soil in the MiniLab on the next page.

Natural resources are those parts of the environment that are usefulor necessary for living organisms. Natural resources include sunlight,water, air, and plant and animal resources. Because species are dependentupon sufficient supplies of natural resources, they must be consideredduring the planning of any conservation activity.

Legal protections of species In response to concern about species extinction, the U.S. Endangered

Species Act became law in 1973. This law made it illegal to harm anyspecies on the endangered or threatened species lists. Further, the lawmade it illegal for federal agencies to fund any project that would harmorganisms on these lists. Harm includes changing an ecosystem whereendangered or threatened species live.

Back from the BrinkUsing Prior KnowledgeWhoops! Have you ever stoodat the sink and watched as aring slid off your soapy fingerand slipped down the drainbefore you could grab it?Could you retrieve it? Theloss of a species is thought bymany to be a significantoccurrence. Once that speciesis gone, the unique role that itplayed and the unique geneticmessage that it contained are goneforever. Scientists, like the onesshown here reintroducing a gray wolf tothe wild, are making efforts to keep species from becoming extinct.Research Research some organisms that have been brought back from the brinkof extinction. Describe the steps taken for one such organism. What are thestrengths and weaknesses of such programs?

Conservation of Biodiversity

(t)Jeff Lepore/Photo Researchers, (b)Victoria McCormick/Animals Animals

A gray wolf

Matt Meadows

122 BIOLOGICAL DIVERSITY AND CONSERVATION

Worldwide, the Convention on Inter-national Trade in Endangered Species(CITES) has established lists ofspecies for which international trade isprohibited or controlled. This agree-ment has been endorsed by more than120 countries.

Preserving habitatsThe importance of preserving habi-

tats has been recognized in the UnitedStates and many other countries. Ahabitat is the physical location wherean organism lives and interacts withits environment. One way that habi-tats have been protected is throughthe creation of natural preserves andparks. The United States establishedits first national park—YellowstoneNational Park—in 1872. InitiallyYellowstone was created to protect theregion’s unique geology. However, itsecological importance is recognized asbeing equally significant. Species ofbear, bison, moose, and elk roam thepark in much the same way that theyroamed the area hundreds of yearsago. Other national parks in theUnited States include Big CypressNational Preserve, Crater LakeNational Park, Big Bend NationalPark, and Sequoia National Park.Each park protects a unique naturalenvironment and provides habitats formany organisms.

Establishing parks and other pro-tected regions has been an effectiveway to preserve ecosystems and thecommunities of species that live inthem. Although natural preservesmake up a relatively small amount ofland in some countries, these areascontain a large amount of biodiversity.For example, 3.9 percent of the landin the Democratic Republic of Congoin Africa has been protected. How-ever, this small amount of land ishome to almost 90 percent of thenation’s bird species.

InvestigateConservation of Soil Soil is as important a natural resourceas plant and animal species and should be conserved. Howdoes one conserve soil? What factors speed up the unneces-sary loss or erosion of soil?

Procedure! Copy the data table below.

@ Measure 200 mL of water in a beaker.# Fill a tray with soil as shown in the

photograph.$ Pour the water onto the soil,

tilting the tray over a dish as indi-cated in thephotograph.

% Wait for allwater and soilto drain intothe dish.

^ Pour the soiland water from the dish into a graduated cylinder. Wait sev-eral minutes for the soil to settle. Measure the volume of soiland water that washed or eroded into the dish. Record thesevalues in your data table.

& Repeat steps 2–6. This time use a section of soil in whichgrass is growing. CAUTION: Always wash your hands withsoap and water after working with soil.

* Make wise choices about disposal of the materials.

Analysis1. Analyze Trends from Data What part of the experiment

simulated soil erosion?2. Make Inferences from Data Based on this experiment,

explain why farmers usually plant unused fields with sometype of crop cover.

Soil Erosion

Volume of Volume ofSource of Original Collected Volume ofSample Water Water Eroded Soil

Bare soil

Soil with grass

Habitat corridorsIs it better to protect one large

piece of land or several smaller, disconnected pieces of land? Recallthe research describing the numberof insect and spider species onislands of different sizes. In general,larger islands had more species thansmaller islands had. Therefore, ageneral strategy for protecting thebiodiversity of an area probably is to protect the largest area possible.However, research is showing thatkeeping wildlife populations com-pletely separate from one anothermay be resulting in inbreedingwithin populations. Therefore, an-other strategy for preserving biodi-versity is to connect protected areaswith habitat corridors.

Corridors such as the one in Figure 5.11 are being built in Flor-ida to protect the Florida panther.Habitat corridors are protectedstrips of land that allow the migrationof organisms from one wildernessarea to another. Research has shownthat corridors can help overcomesome of the effects of habitat destruc-tion and are beneficial for both plantsand animals.

Working with peopleSaying an area is protected does

not automatically make all the speciesthere safe. Parks and protected areasusually hire people, such as rangers,to manage the parks and ensure theprotection of organisms. In someareas, access by people is restricted.In other lands, people can harvestfood or obtain materials but this sortof activity is managed. The philoso-phy of sustainable use strives toenable people to use natural re-sources in ways that will benefitthem and maintain the ecosystem.For example, in Figure 5.12, peopleharvest Brazil nuts to eat and to sell.This provides the opportunity toearn a living and the ecology of thearea is maintained.

5.2 CONSERVATION OF BIODIVERSITY 123(t)Charlie Heidecker/Visuals Unlimited, (bl)Tony Morrison/South American Pictures, (br)KS Studios

Figure 5.12Sustainable use of wildlife areas enables peopleto protect these areas. The sale of Brazil nuts,sustainably harvested from rain forests in theAmazon, provides income for people living there.

Figure 5.11In Florida, the Floridapanther can move fromone habitat to anotherby crossing under ahighway. Constructionof these habitat corri-dors has resulted in adecrease of panthersbeing struck by cars.

124 BIOLOGICAL DIVERSITY AND CONSERVATION(t)M.C. Chamberlain/DRK Photo, (b)Alan D. Carey/Photo Researchers

Reintroduction and speciespreservation programs

The year is 1991. A wildlife managercarries a cage containing a captive-bredblack-footed ferret, like the one inFigure 5.13. She opens the cage door, and the ferret steps out onto the ground. In the 1970s, the black-footed ferret was almost lost from thewild and was listed as an endangeredspecies. The ferret depends uponprairie dogs for food, and prairie doghabitat had been reduced by rural land use. In 1981, a small populationof black-footed ferrets was found by a rancher. Biologists studied the ferrets and established a captive-breeding program at the NationalBlack-footed Ferret ConservationCenter in Wyoming. The captive-breeding program has become a suc-cess, and black-footed ferrets havebeen released into the wild in a num-ber of western states. Reintroductionprograms, such as this one, releaseorganisms into an area where thespecies once lived. Today, about350 black-footed ferrets live in thewild. To learn about the controversysurrounding the reintroduction ofsome species to the wild, read theProblem-Solving Lab.

Figure 5.13A black-footed ferret is reintroduced into itsnative habitat in Wyoming. The caregiverwears a mask to reduce the chances she willtransmit a human disease to the ferret.

Think CriticallyWhy are conservation effortssometimes controversial? Therehave been many attempts to breedwild animals or move them fromone area to another. The goal is topreserve wildlife species. However,reintroduction programs of somespecies can have unintended consequences.

Solve the ProblemCase 1: In March 1998, the U.S. Fish and Wildlife Service rein-troduced 11 captive-bred Mexican gray wolves (Canis lupusbaileyi) into parts of Arizona. They had been extinct from thearea for 20 years. By law, ranchers are not allowed to killnative wolves. However, reintroduced wolves received speciallegal status under the Endangered Species Act and can bekilled by ranchers if the wolves threaten livestock.

Case 2: In 1995, a group of gray wolves (Canis lupus) was cap-tured in Canada and introduced into Yellowstone NationalPark, where gray wolves once had been abundant. Because thewolves killed some cattle in the region, legal pressure wasmounted to have the wolves removed from the park. InDecember 1997, a United States district court ruled that thewolves should be removed from the park. However, somegroups have appealed the decision and the future home of thewolves is undecided.

Thinking Critically1. Evaluate the Impact of Research on Society Imagine

that you are a rancher described in Case 1. What complaintsmight you have about the 1998 reintroduction program?

2. Evaluate the Impact of Research on Society In Case 1,describe the arguments that might be offered in favor ofthe reintroduction program.

3. Evaluate the Impact of Research on Society In Case 2,describe the role that scientists might have in decidingwhether the wolves should be removed.

A gray wolf

The most successful reintroductionsoccur when organisms are taken froman area in the wild and transported to anew suitable habitat. The brown peli-can was once common along the shoresof the Gulf of Mexico. DDT causedthis bird’s eggs to break, and the brownpelican completely disappeared fromthese areas. After DDT was banned inthe United States in 1972, 50 brownpelicans were taken from Florida andput on Grand Terre Island in Loui-siana. The population grew and spread,and today more than 7000 brown peli-cans live in the area.

CaptivitySome species no longer exist in the

wild, but a small number of individualorganisms is maintained by humans. Anorganism that is held by people is saidto be in captivity. The ginkgo tree, asshown in Figure 5.14, is an example ofa species surviving extinction because itwas kept by people. The ginkgo is anancient tree; all similar species becameextinct long ago. However, Chinesemonks planted the ginkgo tree aroundtheir temples, thereby preventing thetree from becoming extinct.

Protecting plant speciesThe ideal way to protect a plant

species is to allow it to exist in a natural

ecosystem. But seeds can be cooled andstored for long periods of time. Byestablishing seed banks for threatenedand endangered plants, the species canbe reintroduced if they become extinct.

Reintroductions of captive animalsare more difficult than for plants.Keeping animals in captivity, withenough space, adequate care, andproper food, is expensive. Animals keptin captivity may lose the necessarybehaviors to survive and reproduce inthe wild. Despite the difficultiesinvolved, some species held in captivity,such as the Arabian oryx and theCalifornia condor, have been reintro-duced to their native habitats afterbecoming nearly extinct in the wild.

Understanding Main Ideas1. Contrast the fields of conservation biology and

ecology.2. Describe the U.S. Endangered Species Act. When

did it become law, and how does it help protector preserve endangered species?

3. Evaluate the difficulties with reintroduction programs using captive-born animals.

4. Choose one species that you have read about,either here or in your library, and explain howconservation strategies lead to its recovery.

Thinking Critically5. How can habitat degradation cause changes in an

area’s biodiversity?

6. Get the Big Picture How might habitat corridors help overcome problems with habitatfragmentation? Research some actual situationsconcerning the Florida panther, including thecosts involved. For more help, refer to Get theBig Picture in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

5.2 CONSERVATION OF BIODIVERSITY 125Sid Greenberg/Photo Researchers

Figure 5.14The ginkgo tree wouldprobably be extinct ifnot for the care givento specimens that hadbeen planted onmonastery grounds.Ginkgo biloba survivespollution well, makingit useful for urbanlandscapes.

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126 BIOLOGICAL DIVERSITY AND CONSERVATION

Before YouBegin

What would it be like toown a pet like a snake or ablack-footed ferret? Use

as aresearch tool to locateinformation on exotic pets.Consider any animal asexotic if it is not commonlydomesticated and is notnative to your area.

Researching Informationon Exotic Pets

Problem How can you use the

to gather infor-mation on keeping an exotic animal as a pet?

ObjectivesIn this BioLab, you will: ■ Select one animal that is con-

sidered an exotic pet.■ Use the Internet to collect

and compare informationfrom other students.

■ Conclude whether the animalyou have chosen would orwould not make a good pet.

Materials access to the Internet

PREPARATIONPREPARATION

A rhesus monkey

1. Copy the data table and use it as a guide forthe information to be researched.

2. Pick an exotic pet from the following list ofchoices: hedgehog, large cat such as tiger orpanther, monkey, ape, and iguana.

3. Go toto find links that will provide you with information for this BioLab.

4. Post your findings in the data table at

PROCEDUREPROCEDURE

A hedgehog

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bdol.glencoe.com/internet_lab.

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internet_lab

(tl)George Calef/DRK Photo, (tr)Aldo Brando/Peter Arnold, Inc., (b)Renee Stockdale/Animals Animals

Scarlet macaw

Exotic pet choice

Scientific name

Natural habitat (where found in nature)

Adult size

Dietary needs

Special health problems

Source of medical care, if needed

Safety issues for humans

Size of cage area needed

Special environmental needs

Social needs

Cost of purchase

Cost of maintaining (monthly estimate)

Care issues (high/low maintenance)

Additional information

Additional sources

Data Table

Category Response

A ferret

Iguanas

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

1. Define Operationally What is meant by the term domesticated?2. Interpret Data Does your data make it clear as to why the organism you

selected is considered exotic or not? Explain.3. Analyze Data Look at the findings posted

by other students. Which of the animalsresearched would make a pet? Which wouldnot be a wise choice? Why?

4. Think Critically What positive contributionmight be made to the cause of conservationwhen keeping an exotic pet? Explain.

5. Think Critically How can keeping exoticpets be a negative influence on conservationbiology efforts?

6. Analyze Data What are some reasons whyzoos rather than individuals are better able tohandle exotic animals?

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5.2 CONSERVATION OF BIODIVERSITY 127

Use the link below to post your findings in the data table provided for this activity.Use additional data from other students toanswer the questions for this BioLab.

(t)Renee Stockdale/Animals Animals, (b)Fred Bruemmer/DRK Photo

128 BIOLOGICAL DIVERSITY AND CONSERVATIONArt Wolfe

Poetry and Prose Look in your neighborhoodfor a small area or an individual organism thatinterests you. Photograph or draw the area ororganism. Then write a caption that connects tothe photo or illustration.

To find out more about Art Wolfe or peo-ple who write about, take photographs of, or illustrate science creatively, visitbdol.glencoe.com/art

Photographing Life

Art Wolfe received a degree in fine arts fromthe University of Washington where he

was trained as a painter. He applied his knowl-edge of art and painting to become one of theworld’s best wildlife photographers. With morethan 1 million images to his credit, Wolfe’s pho-tographs of Earth and its inhabitants capture thebest nature has to offer.

Although he has captured many landscapes onfilm, photographer Art Wolfe is probably mostwell-known for his images of wildlife. Theseinclude just about every organism from A to Z in a variety of places around the world. Wolfe,for example, has traveled to Antarctica to photo-graph playful Adélie penguins as they waddleacross the ice sheet. Journeys to the northernhemisphere brought Wolfe into contact withbrown bears, mule deer, and wolves. Treks toAfrica have allowed the photographer to capturethe intricate patterns and symmetry of zebras,both alone and in herds.

Capturing the moment Wolfe generally hasfour goals in mind when out on a shoot. One ofthe goals is to get as close as possible to his sub-ject. This, according to the artist, allows him tofreeze the instant of contact between himself andhis subject.

Another of Wolfe’s goals is to try to capture ananimal in its natural surroundings. Says Wolfe ofone of his images of a black bear, “. . . habitat is asimportant as the animal.” Wolfe’s third goal is tocapture patterns in nature, such as the patterns ina herd of zebras. His fourth goal while out on ashoot is to try to capture an animal’s behavior.Among Wolfe’s photographs illustrating this goalare brown bears sparring in a cold Alaskan river, aNorthern gannet meticulously constructing itsnest, a snowy owl chick practicing a fierce stare,and mule deer foraging in a grassy field some-where in Montana.

Preserving nature for posterity Wolfe’s work has been seen by wide audiences. His photographs help people appreciate the naturalworld and want to protect it. In 1998, the North American Nature Photography Associa-tion awarded Wolfe its prestigious OutstandingPhotographer of the Year Award. That year, Wolfe also received the first Rachel Carson Awardpresented by the National Audubon Society forhis work in calling attention to animals and habi-tats that are in danger of disappearing forever.

Snowy owl chick

Section 5.1Vocabularyacid precipitation

(p. 118)biodiversity (p. 111)edge effect (p. 117)endangered species

(p. 115)exotic species (p. 120)extinction (p. 115)habitat degradation

(p. 118)habitat fragmentation

(p. 117)ozone layer (p. 118)threatened species

(p. 116)

VanishingSpecies

STUDY GUIDESTUDY GUIDE

CHAPTER 5 ASSESSMENT 129(t)Michael Sewell/Peter Arnold, Inc., (b)Jeff Lepore/Photo Researchers

To help you review biologicaldiversity and conservation, use the Organiza-tional Study Foldables on page 111.

Section 5.2Vocabularycaptivity (p. 125)conservation biology

(p. 121)habitat corridors

(p. 123)natural resources

(p. 121)reintroduction programs

(p. 124)sustainable use (p. 123)

Conservation ofBiodiversity

bdol.glencoe.com/vocabulary_puzzlemaker

Key Concepts■ Biodiversity refers to the variety of life in

an area.■ The most common measure of biodiversity

is the number of species in an area.■ Maintaining biodiversity is important

because if a species is lost from anecosystem, the loss may have conse-quences for other species in the samearea, including humans.

■ Extinctions occur when the last membersof species die.

■ Habitat loss, fragmentation, and degrada-tion have accelerated the rate of extinctions.

■ Exotic species, introduced on purpose orby accident, upset the normal ecologicalbalance in a given area because there areno natural competitors or predators in thatarea to keep their growth in check.

Key Concepts■ Conservation biology is the study and

implementation of methods to preserveEarth’s biodiversity.

■ In 1973, the Endangered Species Act wassigned into law in response to concernsabout species extinction. The law protectsspecies on the endangered and threatenedspecies lists in an effort to prevent theirextinction.

■ Larger protected areas generally have greaterbiodiversity than smaller protected areas.

■ Animal reintroduction programs have beenmore successful when the reintroducedorganisms come from the wild rather thanfrom captivity.

Review the Chapter 5 vocabulary words listed inthe Study Guide on page 129. Match the wordswith the definitions below.

1. when the last member of a species dies 2. number of species that live in an area 3. use of resources of wilderness areas in ways

that do no damage 4. separation of wilderness into smaller parts 5. release of captive organisms into areas where

they once lived

6. In a study of major bodies of water in theworld, aquatic ecologists sampled equal volumes of water and counted the numberof species in each sample. Where would you expect to find the smallest number ofspecies?A. Lake Victoria, a very large tropical lake

in East AfricaB. the Great Barrier Reef, a coral reef off

the coast of AustraliaC. Lake Champlain, a large lake between

New York and VermontD. coral reefs in the Red Sea, between Israel

and Egypt

7. A protected wildlife area allows local huntersto shoot deer when the deer population risesabove a certain level. This is an effort toprevent ________.A. habitat lossB. habitat fragmentationC. habitat degradationD. habitat conservation

8. The variety of species in an ecosystem isreferred to as its ________.A. endangered speciesB. edge effectC. biodiversityD. threatened species

9. The few remaining California condors,nearly extinct in the wild, were taken andbred in captivity. Offspring were successfullyreleased. The success might be due to thefact that ________.A. the birds were released in an area away

from the factors that caused them to die out

B. corridors were built to allow the birds tofly unrestricted in the wild

C. the bird is an exotic species and whenreleased survived because there were nopredators

D. the birds were reintroduced to an areasimilar to their original territory but inanother state.

10. Open Ended Each year, more than a millionpeople die from malaria, which is carried bymosquitoes. These mosquitoes could be con-trolled by the application of DDT. Researchand analyze the strengths and weaknesses ofexplanations about DDT use.

11. Open Ended Research how island size may help in planning national parks and preserves. Use scientific evidence to discussthe strengths and weaknesses of thishypothesis.

12. Open Ended Why is habitat loss a threat tobiodiversity? Describe a situation in which aspecific animal or plant might be at risk.

13. Analyze A national park has four choicesfor how roads will cross through the park.Which method would produce the leasthabitat fragmentation? Give reasons foryour choice.

130 CHAPTER 5 ASSESSMENT

A. B. C. D.

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CHAPTER 5 ASSESSMENT 131

bdol.glencoe.com

State Wetland Data

Total number of Percentendangered wetlandspecies dependent

157 plants 65

510 vertebrates 58

A. B.

bdol.glencoe.com/standardized_test

14. Refer to the illustration below. An adultmale Florida panther requires an average of 10.52 km2 of territory to survive andreproduce. Development has changed a particular panther’s territory from 21 km2

in diagram A to the territory configurationin diagram B which is broken up by road-ways. What can be done to improve thepanther’s habitat in situation B?

15. Using the idea of carrying capacity, design aplan for sustainable use of trout in a mid-western lake.

16. In recent years there have been some important successes with reintroduction programs.Visit to investigatesome of the success stories. What are the simi-larities between each of the successful reintro-ductions? Make a map to show the range of atleast two species before and after their reintro-duction and relate your findings to the class.

REAL WORLD BIOCHALLENGE

Habitat fragmentation

Multiple ChoiceUse the graph below to answer questions 17 and18 about wetland-dependent species in a north-eastern state.

17. Calculate the number of endangered plantsthat are wetland dependent.A. 157 C. 102B. 296 D. 123

18. What is the total number of endangeredspecies that are wetland dependent?A. 102 C. 296B. 157 D. 398

19. A federally funded project was halted when anendangered species was found on the land.This probably occurred because ________.A. the U.S. Endangered Species Act forbids

the developmentB. a reintroduction program was under wayC. the endangered species was an animal

and not a plantD. the Endangered Species list needed to be

updated

20. Which of the following is an abiotic factorassociated with loss of biodiversity?A. An exotic species is introduced to the

area.B. A predator disappears.C. A population doubles.D. Habitat corridors open new territories.

Constructed Response/Grid InRecord your answers on your answer document.

21. Open Ended Large carnivores have a greater chance of becoming extinct than smaller organ-isms. What factors make this statement true? Provide examples.

22. Open Ended Why is it important for people to know something about the social and economicas well as the scientific aspects of an area when planning a national park?

EcologyAn organism’s environment is the source of all its

needs and all its threats. Living things dependon their environments for food, water, and shelter.Yet, environments may contain things that caninjure or kill organisms, such as storms, diseases,or predators. Ecology is the study of the interactionsbetween organisms and their environments.

Symbiosis

Bees pollinate flowers, and inreturn, bees obtain nectar.

132

Relationships formed between organismsare important biotic factors in an environ-

ment. Adaptations, which can be physiological, structural,or behavioral, enable organisms to profit from relationships. In symbiosis,the close relationship between two species, at least one species profits.There are three categories of symbiosis that depend on whether theother species profits, suffers, or is unaffected by the relationship.

Mutualism In mutualism, both species benefit from their relationship.For example, bees have a mutualistic relationship with flowers. As thebee eats nectar from the flower, pollen becomes attached to the bee.The bee moves to another flower, and some of the pollen from the firstflower may pollinate the second flower. The bee gets food, and theplant is able to reproduce.

EcosystemsThe relationships among living things and how

the nonliving environment affects life are the keyaspects of ecology. An ecosystem is made up of allthe interactions among organisms and their envi-ronment that occur within a defined space.

Abiotic FactorsAround the world there are many types of bio-

mes, such as rain forests and grasslands. The non-living parts of the environment, called abioticfactors, influence life. For example, latitude, tem-perature, and precipitation influence the type oflife in a terrestrial biome.

Hot temperatures and little pre-cipitation are abiotic factorsin this desert biome.

This coral reef’s survival strategiesinclude methods of obtaining needsand avoiding dangers.

Clingfish hide in thespines of a sea urchin.

(t)Fred Bavendam/Minden Pictures, (c)Nigel J. Dennis/Photo Researchers, (bl)D.R. Specker/Animals Animals, (br)W. Gregory Brown/Animals Animals

Ecology

A tree parasitized by mistletoe

133

Commensalism In commensalism, one speciesbenefits, while another species is neither helpednor hurt. A clingfish hiding in the stinging spinesof a sea urchin is an example of commensalism.The clingfish hides from predators because thesea urchin’s sting deters many predatory organ-isms. The clingfish benefits from the relationship,but the sea urchin is not harmed.

Parasitism Another form of symbiosis is para-sitism, which exists when a smaller parasiteobtains its nutrition from a larger host. The rela-tionship benefits the parasite, and is harmful tothe host. An example of parasitism includes atapeworm in the intestines of a human.

The water cycle, featuring evaporation fromlakes and oceans, condensation to produce clouds,and precipitation, provides an understanding ofhow water cycles through an ecosystem. Nitrogenand carbon also cycle through ecosystems. In thecarbon cycle, plants produce nutrients from carbondioxide in the atmosphere. When these nutrientsare broken down, energy is released. Carbon diox-ide is also released and returns to the atmosphere.

Biotic FactorsLiving organisms and the effects they have on

each other are biotic factors. A population consistsof one species. Within a community, different pop-ulations compete for needs, predators kill prey,and diseases spread.

Autotrophs andHeterotrophs

Organisms that make their own food, such as plants and algae, are called autotrophs.Organisms that cannot make their food must con-sume other organisms. These organisms are calledheterotrophs or consumers. Heterotrophs thatconsume only plants are called herbivores.Heterotrophs that consume only animals are called carnivores. Omnivores are heterotrophsthat consume plants and animals.

Nutrient and Energy FlowLife on Earth depends on energy from the sun.

Plants use this light energy to make food. Animalseat plants or other animals for food.

The path the nutrients and energy take can beshown in a food chain such as:

rose ➔ aphid ➔ ladybug

This shows that the aphid eats the rose andobtains its nutrients and energy. The ladybug eatsthe aphid and obtains its nutrients and energy.This food chain is simple. More complex feedingrelationships are represented by a food web.

In summary, nutrients cycle through ecosystems.Today, there is as much nitrogen and carbon orphosphorus and water as there was millions ofyears ago. Energy is transferred from one organ-ism to another, but at each transfer, some energyis given off to the environment as heat.

In photosynthesis, plants use nonliving (abiotic) materi-als, including water, carbon dioxide, and light energy, toproduce energy-rich nutrients. For this reason, photo-synthetic organisms are called producers.

(t)Dana White/ImageQuest, (b)Doug Sokell/Visuals Unlimited

Ecology

Pioneer Species

As lichens grow, theybreak down rocks andproduce soil.134

Trophic LevelsNutrients and energy move from autotroph

to herbivore to carnivore. Each of these steps iscalled a trophic level. If a forest area were ropedoff and three piles created—autotrophs, herbi-vores, and carnivores, the autotroph pile would belarger than the herbivore pile, which would belarger than the carnivore pile. The mass of thepiles indicates the biological mass, or biomass, ofthe three trophic levels. The mass of autotrophs isusually about ten times the mass of the herbi-vores, and the mass of the herbivores is about tentimes the mass of the carnivores.

Population SizeA population is defined as all the members of

one species living in an area. The size of a popula-tion is influenced by the environment. For exam-ple, a lack of food could limit the number oforganisms. Other limiting factors in populationgrowth are water, shelter, and space. As popula-tion size increases, competition for some neededitems intensifies.

Carrying CapacityThe maximum population size an environment

can support is called its carrying capacity. Whenpopulation size rises above the carrying capacity,some organisms die because they cannot meet alltheir needs. The population falls back to belowthe carrying capacity until it reaches equilibriumwith the environment.

Exponential GrowthIf a population has no predators, and the

organisms are in a resource-rich environment, population size would grow quickly. This fastgrowth is called exponential growth. Exponentialgrowth cannot continue forever; at some point,some need will become a limiting factor in thepopulation’s growth.

Vital StatisticsEnergy in a 100 m � 100 m section of forest: Producers—24 055 000 kilocaloriesHerbivores—2 515 000 kilocaloriesCarnivores—235 000 kilocalories

Populations may be kept below theircarrying capacity due to predation.

The first organisms to colonize new areas are pioneer species. Rockyareas, such as land recently covered by a lava flow, have pioneer

species different from areas that already have soil. Rocky areas are usu-ally first colonized by lichens.

On rock Lichens are made up of two organisms, a species of fungusand a species of photosynthetic algae or bacteria. The fungus holds itsphotosynthetic partner between thick fiber layers, allowing just enoughlight to penetrate to allow photosynthesis (food production) withoutdrying out the lichen. The fungus provides a tough case and the photo-synthetic partner supplies nutrition. Through this mutualistic relation-ship, lichens are able to survive in the harshest of climates such as highon mountains, in cold arctic regions, and in hot deserts.

(t)J & B Photographers/Animals Animals, (b)Doug Sokell/Visuals Unlimited

Ecology

135

Dandelions are an effective pioneer species for secondary successionbecause they grow fast and disperse many seeds.

SuccessionWhat happens when a building is torn down

and not replaced? Usually the land begins tochange almost immediately. New plants sprout.No doubt, one of the first things to grow areweeds. Blown in or carried by animals into anarea that already has soil, plants act as pio-neer species, the first organisms to thrive in anew environment.

After the plants take hold in an area, othersappear, including annual flowers, grasses andthen bushes. These provide shade. Now tree seeds germinate. Once the tree saplings are large enough, they shade the ground, blockingthe sun from plants underneath. New conditionsare forming to make the environment suitable for other organisms. If left to themselves longenough, abandoned areas become new forests.Succession is the process by which these and othertypes of areas change.

BiodiversityDuring succession, the species living in an

ecosystem change, usually by moving in or dyingout of an area, over time. Consequently, theecosystem changes too. Earth’s biosphere, the partof the planet that supports life, changes over timeas well. The measure of change that takes place ina small habitat or a large ecosystem is the numberof species of organisms—plants, animals, bacteria,fungi, and other microorganisms that are found inthe area. This number of species in an area is thearea’s biodiversity.

PopulationsThere are many pressures that act as controls

on the growth of all populations. Predators anddisease help control populations. In addition,Earth’s organisms compete with each other forfood, shelter, and space. Some of these pressuresbring about the extinction or threat of extinctionof species. How to use and find enough of theresources needed by all living organisms, especiallyland, food, air, and water, is of immediate concernfor maintaining Earth’s biodiversity. As land is con-verted for other uses, organisms lose their habitats.When organisms die out of a habitat that has beendestroyed, organisms that depend on those habi-tats are also affected.

The variety of species in coral reefs is important in maintaining Earth’s biodversity.

In soil After existing land is dis-turbed, such as after a forest fire, sec-ondary succession begins as pioneerspecies appear. Most pioneer plantsproduce many small seeds that aredispersed easily over wide areas, sothat when land is disturbed, the seedsare there, ready to grow. Anothercharacteristic of pioneer species isthey tend to grow and reproducequickly. When a fresh patch of soil isdisturbed, pioneer species sproutquickly and produce many new seedsto colonize other areas.

(t)Bruce Watkins/Animals Animals, (b)Envision/B.W. Hoffman

136 UNIT 2 STANDARDIZED TEST PRACTICE

Multiple ChoiceUse the graph below to answer questions 1–3. Thegraph compares the growth rates of two organismswhen grown together and when grown separately.

1. When grown separately, how would you bestdescribe what happened to organism 2 duringweek 3?A. It reached carrying capacity.B. The population died out.C. It became threatened.D. It began to grow exponentially.

2. When the organisms were grown together,what was the approximate rate of growthbetween weeks 2 and 6?A. 75 per week C. 50 per weekB. 100 per month D. 25 per day

3. From the data, the association between theorganisms is ________.A. commensalism C. mutualismB. parasitism D. socialism

4. The number of species in an area is known as________.A. population C. biodiversityB. competition D. carrying capacity

5. Which of the following is a biotic factor in anecosystem?A. number of predatorsB. amount of light receivedC. average precipitationD. average temperature

Study the graph and answer questions 6–9.

6. In which interval were there more extinctionsfor mammals than for birds?A. 1600–1649 C. 1750–1799B. 1650–1699 D. 1850–1859

7. In which interval were there the most mammalextinctions?A. 1600–1649 C. 1850–1859B. 1650–1699 D. 1900–1949

8. Approximately how many bird species becameextinct in the interval 1650–1699?A. 5 C. 15B. 10 D. 20

9. Approximately how many bird species becameextinct in the interval 1600–1949?A. 37 C. 110B. 70 D. 300

Nu

mb

er o

f sp

ecie

s g

oin

g e

xtin

ct

1600–1649

1650–1699

1700–1749

1750–1799

1800–1849

1850–1899

1900–1949

10

20

30

40

Years

Extinctions of Birds and Mammals

BirdsMammals

Nu

mb

er p

rese

nt

in h

un

dre

ds

Time in weeks1 2 3 4 5 6 7

1

2

3

4

5

Organisms #1 and #2

grown together

Organism #1 grown alone

Organism #2 grown alone

Growth Rates of Two Organisms

Stumbling Is NotFalling

From time to time you find a question that com-pletely throws you. You read the question overand over, and it still doesn’t make sense. If it is a multiple choice question, focus on somethingin the question that you do know somethingabout. Eliminate as many of the choices as youcan. Take a best guess, and move on.

10. According to the food web shown, all organ-isms except the cactus are ________.A. decomposersB. consumersC. producersD. scavengers

11. Texas horned lizards may have declined innumber because they are ________.A. preyed upon by harvester antsB. protected by lawC. a threatened speciesD. losing their supply of food

12. The Texas horned lizard primarily competeswith ________ for its food.A. snakesB. cactus plantsC. other lizardsD. fire ants

13. Horned lizards are ectotherms. Energy theyabsorb by lying on hot rocks is transferred by________.A. convectionB. radiationC. conductionD. evaporation

Constructed ResponseRecord your answers on your answer document.

14. Open Ended What eventually happens to a population that is currently experiencing exponentialgrowth? Explain.

15. Open Ended Describe how a specific abiotic factor and a specific biotic factor could affect the life of a deer.

bdol.glencoe.com/standardized_test UNIT 2 STANDARDIZED TEST PRACTICE 137

Use the information below and your knowledge of science to answer questions 10–13.

The Texas Horned LizardThe Texas “horny toad,” Phrynosoma cornutum, is known by many names, but it is a lizard—a true reptile—

and not a toad. Despite its spiny appearance, this lizard was collected extensively as a pet for many years. However,horned lizards do not do well as pets, and once in captivity, most starve to death even if food is available.

In the wild, horned lizards will eat some grasshoppers and beetles, but harvester ants make up about 66 percent of their diet. Where harvester ant habitats have been damaged, horned lizard populations havealso declined. When fire ants established themselves in Texas, harvester ant populations decreased. Thehorned lizard will not feed on fire ants.

Texas hornedlizard

Diamondback rattlesnake

Decomposers

Prickly pear catus

Harvester ants

HawksCoyotes

Other lizards

Desert Food Web