hes08 ch06 152-155 s01 8/18/06 10:41 am page 152 biomes

Biomes

152 Chapter 6 Biomes

CC H A P T E R 61 What Is a Biome?

2 Forest Biomes

3 Grassland, Desert, andTundra Biomes

PRE-READING ACTIVITY

Four-CornerFoldBefore youread this chap-

ter, create the FoldNoteentitled “Four-Corner Fold”described in the Reading andStudy Skills section of theAppendix. Label each flap ofthe four-corner fold with“Forest Biomes,” “GrasslandBiomes,” “Desert Biomes,”and “Tundra Biomes.” As youread the chapter, define eachbiome, and write characteristics ofeach biome on theappropriate fold.

This thorny devil lives in the desertof Australia. The grooves in its roughskin help it collect waater to drink.Water from rain or condensationlands on its back and runs along thetiny grooves to iits mouth.

hes08_ch06_152-155_S01 8/18/06 10:41 AM 52

Section 1 What Is a Biome? 153

Earth is covered by many types of ecosystems. Ecologists groupthese ecosystems into larger areas known as biomes. A is alarge region characterized by a specific type of climate and certaintypes of plants and animal communities. The map in Figure 1shows the locations of the world’s major land, or terrestrial, bio-mes. In this chapter, you will take a tour through these terrestrialbiomes—from lush rain forests to scorching deserts and the frozentundra. When you read about each biome, notice the adaptationsof the organisms to their very different environments.

Biomes and VegetationBiomes are described by their vegetation because the plants thatgrow in a certain region are the most noticeable characteristics of that region. The plants, in turn, determine the other organismsthat can live there. For example, mahogany trees grow in tropicalrain forests because they cannot survive cold, dry weather.Organisms that depend on mahogany trees live where trees grow.

Plants in a particular biome have these adaptations thatenable them to survive there. These adaptations include size,shape, and color. For example, plants that grow in the tundratend to be short because they cannot obtain enough water togrow larger. They also have a short summer growing season.Desert plants, such as cactuses, do not have leaves. Instead, cac-tuses have specialized structures to conserve and retain water.

How are ecosystems related to biomes? (See theAppendix for answers to Reading Checks.)■●✓ Reading Check

biomeObjectives

� Describe why vegetation is used toname a biome.

� Explain how temperature andprecipitation determine whichplants grow in an area.

� Explain how latitude and altitudeaffect which plants grow in an area.

Key Termsbiomeclimatelatitudealtitude

S E C T I O N 1

What Is a Biome?

Figure 1 � The ecosystems of theworld can be grouped into regionscalled biomes. These biomes, shownbelow, are named for the vegetationthat grows there.

EARTH SCIENCE CONNECTION

hes08_ch06_152-155_S01 7/27/06 12:26 PM Page 153

Biomes and ClimateBiomes are defined by their plant life, but what factors determinewhich plants can grow in a certain area? The main factor is cli-mate. refers to the weather conditions, such as tempera-ture, precipitation, humidity, and winds, in an area over a longperiod of time. Temperature and precipitation are the two mostimportant factors that determine a region’s climate.

Temperature and Precipitation Most organisms are adapted tolive within a certain range of temperatures and will not survive attemperatures too far outside of their range. Plants are also affectedby the length of the growing season, as shown in Figure 2.

Precipitation also limits the organisms that are found in abiome. All organisms need water. The larger an organism is, themore water it needs. For example, biomes that do not receiveenough rainfall to support large trees support communities domi-nated by small trees, shrubs, and grasses. In biomes where rain-fall is not frequent, the vegetation is mostly made up of cactusesand desert shrubs. In extreme cases, lack of rainfall results in noplants, no matter what the temperature is. As shown in Figure 3,the higher the temperature and precipitation are, the taller anddenser the vegetation is. Notice how much more vegetation existsin a hot, wet tropical rain forest than in a dry desert.

Why does temperature limit which plants can growin a certain biome?■●✓ Reading Check

Climate


Savanna

Temperate grasslandTemperate forest Desert

Temperate

Tropical

Subarctic

Arctic

Taiga

Tundra

Tropical rain forest Desert

DryWet

Hot

Dec

reas

ing

tem

pera

ture

Cold

Decreasing precipitation

Figure 3 � Temperature and precipi-tation help determine the type ofvegetation in an ecosystem. As tem-perature and precipitation decrease,the climate of an area becomes drierand vegetation becomes sparser.

Figure 2 � The soil of the tundrabiome is frozen most of the year.Plants such as these have about twomonths in summer to grow andreproduce before temperaturesbecome too cold again.

hes08_ch06_152-155_S01 7/27/06 12:27 PM Page 154

Section 1 What Is a Biome? 155

1. Describe how plants determine the name of abiome.

2. Explain how temperature affects which plants growin an area.

3. Explain how precipitation affects which plants growin an area.

4. Define latitude and altitude. How is latitude differentfrom altitude? How do these factors affect the organ-isms that live in a biome?

CRITICAL THINKING5. Making Inferences The equator passes through

the country of Ecuador. But the climate in Ecuadorcan range from hot and humid to cool and dry. Writea short paragraph that explains what might cause thisrange in climate.

6. Analyzing Relationships Look at Figure 1, andlocate the equator and 30° north latitude. Whichbiomes are located between these two lines?

WRITING SKILLS

S E C T I O N 1 Review

Figure 4 � Latitude and altitude affect climate and vegetation in similar ways.

Latitude and Altitude Biomes and vegetation vary with latitudeand altitude. is the distance north or south of the equa-tor and is measured in degrees. is the height of an objectabove sea level. Climate varies with latitude and altitude. Forexample, climate gets colder as latitude and altitude increase. So,climate also gets colder as you move farther up a mountain.

Figure 4 shows that as latitude and altitude increase, biomesand vegetation change. For example, the trees of tropical rainforests usually grow closer to the equator, while the mosses andlichens of the tundra usually grow closer to the poles. The landlocated in the temperate region, between about 30° and 60° northlatitudes and 30° and 60° south latitudes, is where most of thefood in the world is grown. This region includes biomes such astemperate forests and grasslands, which usually have the moderatetemperatures and fertile soil that are ideal for agriculture.

AltitudeLatitude

www.scilinks.orgTopic: BiomesCode: HE80158

hes08_ch06_152-155_S01 7/27/06 12:28 PM Page 155

156

The air is hot and heavy with humidity. You walk through theshade of the tropical rain forest, step carefully over tangles ofroots and vines, and brush past enormous leaves. Life is allaround you, but you see little vegetation on the forest floor. Birdscall, and monkeys chatter from above.

Tropical Rain ForestsOf all the biomes in the world, forest biomes are the most wide-spread and are home to the greatest diversity of plants, animals,and other organisms. Trees need a lot of water, so forests existwhere precipitation is plentiful. Tropical forests, temperate forests,and taiga are the main forest biomes.

are located in a belt around the Earthnear the equator, as shown in Figure 5. They help regulate worldclimate and play vital roles in the nitrogen, oxygen, and carboncycles. Tropical rain forests are always humid and warm and getabout 200 to 450 cm of rain a year. Because they are near theequator, tropical rain forests get strong sunlight year-round andmaintain a relatively constant temperature year-round. This climateis ideal for a wide variety of plants and animals, as shown inFigure 6. The warm, wet conditions also nourish more species ofplants than any other biome does. While one hectare (10,000 m2)of temperate forest usually contains a few species of trees, the samearea of tropical rain forest may contain more than 100 species.

Tropical rain forests

Objectives

� List three characteristics of tropicalrain forests.

� Name and describe the main layers of a tropical rain forest.

� Describe one plant in a temperatedeciduous forest and an adapta-tion that helps the plant survive.

� Describe one adaptation that mayhelp an animal survive in the taiga.

� Name two threats to the world’sforest biomes.

Key Termstropical rain forestemergent layercanopyepiphyteunderstorytemperate rain foresttemperate deciduous foresttaiga

S E C T I O N 2

Forest Biomes

� Glasswing butterflies live in therain forests of Costa Rica.

� The Rafflessia keithii flowergrows in the rain forests of Borneo.


hes08_ch06_156-164_S02 7/27/06 12:28 PM Page 156

Nutrients in Tropical Rain Forests You might think that thediverse plant life grows on rich soil, but it does not. Most nutri-ents are within plants, not within soil. Organic matter decaysquickly in hot, wet conditions. Decomposers on the rain-forestfloor break down organic matter and return the nutrients to thesoil, but plants quickly absorb the nutrients. Some trees in atropical rain forest support fungi that feed on dead organic mat-ter on the rain-forest floor. In this relationship, the fungi transferthe nutrients from the dead organic matter directly to the tree.

The nutrients are removed so efficiently from the soil in atropical rain forest that water running out of the soil may be asclear as distilled water. Most tropical soils that are cleared ofplants for agriculture lack nutrients and cannot support crops formore than a few years. Many of the trees form above-groundroots, called buttresses or braces, that grow sideways from thetrees and provide the trees with extra support in the thin soil.

Section 2 Forest Biomes 157

Tropical Rain Forest(Limon, Costa Rica)

MonthsJ F M A M J J A S O N D

–60

–40

–20

0

20

40

–50

–30

–10

10

30

Tem

per

atur

e ( ˚C

)

0

10

20

30

40

50

5

15

25

35

45

Prec

ipit

atio

n (

cm)

Figure 5 � The world’s tropical rain forests have heavy rainfall during much of the year and fairlyconstant, high temperatures.

Figure 6 � Species of TropicalRain Forests

� These mountain gorillas live in therain forests of Rwanda.

� The tropical rain forests in the Andes mountains inEcuador are among the wettest places on Earth.

� Scarlet macaws live in the trees of rain forests of Peru.

hes08_ch06_156-164_S02 7/27/06 12:31 PM Page 157

Layers of the Rain Forest In tropical rain forests, different typesof plants grow in different layers, as shown in Figure 7. The fourmain layers above the forest floor are the emergent layer, theupper canopy, the lower canopy, and the understory. The top layeris called the This layer consists of the tallest trees,which reach heights of 60 to 70 m. Trees in the emergent layergrow and emerge into direct sunlight.

The next layer, considered the primary layer of the rain forest,is called the Trees in the canopy can grow more than 30 m tall. The tall trees form a dense layer that absorbs up to 95 percent of the sunlight. The canopy can be split into an uppercanopy and a lower canopy. The lower canopy receives less lightthan the upper canopy does. Plants called such as theorchid in Figure 8, use the entire surface of a tree as a place tolive. Epiphytes grow on tall trees for support. Some grow high inthe canopy, where their leaves can reach the sunlight needed forphotosynthesis. Growing on tall trees also allows them to absorbthe water and nutrients that run down the tree after it rains. Mostanimals that live in the rain forest live in the canopy because theydepend on the abundant flowers and fruits that grow there.

Below the canopy, very little light reaches the next layer,called the Trees and shrubs that are adapted to shadegrow here. Most plants in the understory do not grow more than3.5 m tall. Herbs with large, flat leaves grow on the forest floor.These plants capture the small amount of sunlight that penetratesthe understory. Most of our house plants are native to tropicalrain-forest floors. Because they are adapted to low levels of light,they are able to grow indoors.

In which layer of the rain forest is most of the animal life found?■●✓ Reading Check

understory.

epiphytes,

canopy.

emergent layer.


Emergentlayer

Uppercanopy

Lowercanopy

Understory

Brightlight

Filteredlight

Denseshade

Figure 7 � The plants in tropical rainforests form distinct layers. Theplants in each layer are adapted to aparticular level of light. The tallertrees absorb the most light, while theplants near the forest floor areadapted to growing in the shade.

ChemistryConnection to

Medicines from Plants Manyof the medicines we use comefrom plants native to tropical rainforests. Chemists extract and testchemicals found in plants to deter-mine if the chemicals can cure orfight diseases. Rosy periwinkle, aplant that grows in the tropicalrain forests of Madagascar, is thesource of two medicines, vinblas-tine and vincristine. Vinblastine isused to treat Hodgkin’s disease, atype of cancer, and vincristine isused to treat childhood leukemia.

hes08_ch06_156-164_S02 8/25/06 8:36 AM Page 158

Species Diversity in Rain Forests The tropical rain forest is thebiome with the greatest amount of species diversity. The diversityof rain-forest vegetation has led to the evolution of a diverse com-munity of animals. Most rain-forest animals are specialists that usespecific resources in particular ways. Some rain-forest animals haveamazing adaptations for capturing prey, and other animals haveadaptations that they use to escape predators. For example, thecollared anteater in Figure 8 uses its long tongue to reach insects insmall cracks and holes where other animals cannot reach. Thewreathed hornbill (shown below) uses its strong, curved beak tocrack open nutshells. Insects, such as the Costa Rican mantis inFigure 8, use camouflage to avoid predators. These insects may beshaped like leaves or twigs.

EcofactA Little Land, A Lot of SpeciesTropical rain forests cover less than7 percent of Earth’s land surfacebut contain at least 50 percent ofall the plant and animal species inthe world.

Figure 8 � Examples of plantand animal adaptations in thetropical rain forest include thelong tongue of a collared anteater,

the strong, curved beak of awreathed hornbill, the shape of aCosta Rican mantis, and an orchidattached to a tall tree.

159

hes08_ch06_156-164_S02 7/27/06 12:33 PM Page 159


Deforestation,Climate, and Floods

A plant absorbs water from the soilthrough its roots and transports thewater to its stems and leaves. Waterthen evaporates from pores in plantleaves into the atmosphere througha process called transpiration. Alarge tree may transpire as much as5 tons of water on a hot day. Waterabsorbs heat when it evaporates.Therefore, the temperature is muchcooler under a tree on a hot daythan under a wood or brick shelter.Trees that provide shade aroundhomes keep homes much cooler inthe summer.

When rain falls on a forest, muchof the rain is absorbed by plant rootsand transpired into the air as watervapor. Water vapor forms rain clouds.Much of this water will fall as rainsomewhere downwind from the for-est. Because of the role trees play in

flow freely down the river andspread across fields and into townsduring the seasonal monsoon rains.

Deforestation has also causedterrible floods in places such asBangladesh. The Ganges River startshigh in the Himalaya Mountainsand flows through Bangladesh.Deforestation of the Himalaya

transpiration, deforestation, the clear-ing of trees, can change the climate.If a forest is cut down or replaced bysmaller plants, much of the rainfall isnot absorbed by plants. Instead, therain runs off the soil and causesflooding as well as soil erosion. Theclimate downwind from the forestbecomes drier.

Deforestation led to the disas-trous flooding of the Yangtze Riverin China in 1998. More than 2,000people died in the floods, and atleast 13 million people had to leavetheir homes. When the YangtzeRiver flooded, the water pouredinto a flood plain where over 400million people lived. It is estimatedthat 85 percent of the forest in theYangtze River basin has been cutdown. The millions of tons of waterthat these trees once absorbed now

� A man makes his way past floodedbuildings in his street on a makeshiftraft after the Yangtze River floodedin July 1998. Water of the YangtzeRiver reached record-high levels.

Threats to Rain Forests Tropical rain forests once covered about20 percent of Earth’s surface. Today, they cover only about 7 per-cent. Every minute of every day, 100 acres of tropical rain forestare cleared for logging operations, agriculture, or oil exploration.Habitat destruction occurs when land inhabited by an organismis destroyed or altered. Habitat destruction is the usual reason fora species becoming extinct.

An estimated 50 million people live in tropical rain forests.These people are also threatened by habitat destruction. Theirfood, building materials, culture, and traditions come from andare uniquely connected to the rain forest. The loss of this habitatdestroys their way of life.

Plants and animals that live in rain forests are also threatenedby trading. Many plant species found only in tropical rain forestsare valuable and marketable to industries. Animals are threatenedby exotic-pet trading. Some exotic-pet traders illegally trap ani-mals, such as parrots, and sell them in pet stores at high prices.

What are two main threats to the organisms thatlive in tropical rain forests?■●✓ Reading Check

www.scilinks.orgTopic: Threats to

Rain ForestsCode: HE81521

hes08_ch06_156-164_S02 7/27/06 12:37 PM Page 160

Temperate Forestsoccurs in North America, Australia, and

New Zealand. Temperate rain forests have large amounts of pre-cipitation, high humidity, and moderate temperatures. The PacificNorthwest shown, in Figure 9, houses North America’s only tem-perate rain forest, where tree branches are draped with mossesand tree trunks are covered in lichens. The forest floor is blan-keted with lush ferns. Evergreen trees that are 90 m tall, such asthe Sitka spruce and the Douglas fir, dominate the forest. Otherlarge trees, such as western hemlock, Pacific silver fir, and red-wood, can also be found in temperate rain forests.

Even though the temperate rain forest of the PacificNorthwest is located north of most other rain forests, it stillmaintains a moderate temperature year-round. The temperaterain forest also rarely freezes because the nearby Pacific Oceanwaters keep temperatures mild by blowing cool ocean wind overthe forest. As this ocean wind meets the coastal mountains, alarge amount of rainfall is produced. The rainfall keeps the tem-perate rain forest cool and moist.

Temperate rain forest


Mountains left few trees to stop thewater flowing down the mountain.So, most of the water flows into theriver when it rains. Heavy rains haveeroded and carried away so muchsoil from the slopes of the moun-tains that the soil has formed a new

never been flooded before. Thetownspeople claimed that authoritieshad permitted developers to coverthe hills with homes. These develop-ers cut down most of the trees andcovered much of the land withasphalt. After heavy rains, the waterwas no longer absorbed by trees andsoil, so the water flowed down thehills and flooded the town.

CRITICAL THINKING

1. Identifying RelationshipsHow might deforestation in Chinaand other countries affect the over-all climate of the Earth?

2. Analyzing a ViewpointImagine that you are a city councilmember and must vote on whetherto clear a forest so that a mall canbe built. List the pros and cons ofeach viewpoint. After reviewingyour list, how would you vote?Explain your answer.

island in the Bay of Bengal, which isoff the coast of Bangladesh.

People are beginning to under-stand the connection between defor-estation and floods. People heldprotests in northern Italy in 2000after floods covered a town that had

� Deforestation reduces the amount of water that is absorbed by plantsafter it rains. The more trees that are cleared from a forest, the more likelya flood will occur in that area.

Figure 9 � The only temperate rainforest in North America is located inthe Pacific Northwest, as shownabove in Olympic National Park inWashington State.


hes08_ch06_156-164_S02 7/27/06 12:41 PM Page 161

Temperate Deciduous ForestsIf you walk through a North American deciduous forest in thefall, you will immerse yourself in color. Leaves in every shade oforange, red, and yellow crackle beneath your feet. Most birdshave flown south. The forest is quieter than it was in the summer.You see mostly chipmunks and squirrels gathering and storing thefood they will need during the long, cold winter.

In trees drop their broad, flatleaves each fall. These forests once dominated vast regions of theEarth, including parts of North America, Europe, and Asia.Today, temperate deciduous forests are generally located between30° and 50° north latitudes, as shown in Figure 10. The range oftemperatures in a temperate deciduous forest can be extreme, andthe growing season lasts for only four to six months. Summertemperatures can soar to 35°C. Winter temperatures often fallbelow freezing, so little water is available for plants. Just as temper-atures change with the seasons, so does the vegetation, as shown inFigure 11. Although there is enough moisture for decomposition,temperatures are low during the winter. As a result, organic matterdecomposes fairly slowly. This means that the soil contains moreorganic matter and nutrients than the soil in a tropical rain forest.

Plants of Temperate Deciduous Forests Like the plants of tropi-cal rain forests, the plants in deciduous forests grow in layers.Tall trees, such as maple, oak, and birch, dominate the forestcanopy. Small trees and shrubs cover the understory. Because thefloor of a deciduous forest gets more light than the floor of a rainforest does, more plants such as ferns, herbs, and mosses grow ina deciduous forest.

temperate deciduous forests,

Temperate Deciduous Forest(Stuttgart, Germany)

0

10

20

30

40

50

5

15

25

35

45

–60

–40

–20

0

20

40

–50

–30

–10

10

30

J F M A M J J A S O N D

Months

Prec

ipit

atio

n (

cm)

Tem

per

atur

e ( ˚C

)

Figure 10 � The difference betweensummer and winter temperatures in temperate deciduous forests is extreme.

Figure 11 � The change of seasonsin a temperate deciduous forest inMichigan is shown below.

162

www.scilinks.orgTopic: Temperate

Deciduous Forests

Code: HE81503

hes08_ch06_156-164_S02 7/27/06 12:42 PM Page 162

Temperate-forest plants are adapted to survive seasonalchanges. In the fall, most deciduous trees begin to shed theirleaves. In the winter, moisture in the soil changes to ice, whichcauses the remaining leaves to fall to the ground. Herb seeds,bulbs, and rhizomes (underground stems) become dormant in the ground and are insulated by the soil, leaf litter, and snow.In the spring, when the sunlight increases and the tempera-ture rises, trees grow new leaves, seeds germinate, and rhizomes and roots grow new shoots and stems.

Animals of Temperate Deciduous Forests The animals oftemperate deciduous forests are adapted to use the forestplants for food and shelter. Squirrels eat the nuts, seeds,and fruits in the treetops. Bears feast on the leaves andberries of the forest plants. Grasshoppers, such as the oneshown in Figure 12, eat almost all types of vegetationfound throughout the forest. Deer and other herbivoresnibble leaves from trees and shrubs.

Many birds nest in the relative safety of the canopy.Most of these birds are migratory. Because many birdscannot survive harsh winters, each fall they fly south forwarmer weather and more available food. Each spring,they return north to nest and feed. Animals that do notmigrate use various strategies for surviving the winter. Forexample, some mammals reduce their activity so that theydo not need as much food for energy.

TaigaThe is the northern coniferous forest that stretches in a broadband across the Northern Hemisphere just below the Arctic Circle.As shown in Figure 13, winters are long (6 to 10 months) and haveaverage temperatures that are below freezing and often fall to–20°C. Many trees seem like straight, dead shafts of bark andwood—until you look up and see their green tops. Plant growth ismost abundant during the summer months because of nearly con-stant daylight and larger amounts of precipitation.

taiga


0

10

20

30

40

50

5

15

25

35

45

–60

–40

–20

0

20

40

–50

–30

–10

10

30


Months

Taiga(Edmonton, Canada)

Prec

ipit

atio

n(c

m)

Tem

per

atur

e ( ˚C

)

Figure 13 � The taiga has long, coldwinters and small amounts of precipi-tation, as shown in the climatogrambelow.

Figure 12 � Grasshoppers, wood-peckers, and deer are among themany animals that live in the temper-ate deciduous forest.

hes08_ch06_156-164_S02 7/27/06 12:43 PM Page 163

Plants of the Taiga A conifer is a tree with needle-like leaves andseeds that develop in cones. The shape of the leaves and their waxycoating prevent the tree from losing too much water. This is espe-cially important when the ground is frozen and the roots cannotreplace lost water by absorbing more from the soil. As Figure 14shows, many conifers are shaped like a large cone. The cone-likeshape helps to prevent snow from building up on the branches andcausing the branches to break under the weight.

Conifer needles contain substances that make the soil acidicwhen the needles fall to the ground. Most plants

cannot grow in acidic soil, which is one reasonthe forest floor of the taiga has few plants. Inaddition, soil forms slowly in the taigabecause the climate and acidity of the fallenleaves slow decomposition.

Animals of the Taiga The taiga has many lakesand swamps that in summer attract birds that feed

on aquatic organisms. Many birds migrate south toavoid winter in the taiga. Because food is scarce during the

winter, some year-round residents, such as jumping mice, burrowunderground to hibernate. As shown in Figure 15, some animals,such as snowshoe hares, have adapted to avoid predation by lynxes,wolves, and foxes by shedding their brown summer fur and grow-ing white fur that camouflages them in the winter snow.


1. List three characteristics of tropical rain forests.

2. Name the main layers of a tropical rain forest. Whatkinds of plants grow in each layer?

3. Describe two ways in which tropical rain forests ofthe world are being threatened.

4. Describe how a plant survives the change of sea-sons in a temperate deciduous forest. Write a shortparagraph to explain your answer.

CRITICAL THINKING5. Evaluating Information Which would be better

suited for agricultural development: the soil of a tropi-cal rain forest or the soil of a temperate deciduousforest? Explain your answer.

6. Identifying Relationships How does a snowshoehare avoid predation by other animals during thewinter in a taiga biome? How might this affect theanimal that depends on the snowshoe hare for food?WRITING SKILLS


Figure 14 � The taiga has cold win-ter temperatures, a small amount ofannual precipitation, and coniferoustrees. The seeds of conifers are pro-tected inside tough cones like theone above. Also, the narrow shapeand waxy coating of conifer needleshelp the tree retain water.

Figure 15 � In the taiga, a snowshoehare’s fur changes color according tothe seasons to help camouflage theanimal from predators.

hes08_ch06_156-164_S02 7/27/06 12:44 PM Page 164

In areas with too little precipitation for large trees to survive, thebiomes are dominated by smaller plants. Where there is almostno rainfall at all, few plants can grow and we find desert. Thus,warm areas with little precipitation are characterized by savannaand desert biomes. Temperate areas have grassland, chaparral,and desert biomes, and cold areas have tundra and desert biomes.

SavannasParts of Africa, western India, northern Australia, and some partsof South America are covered by grassland called savanna.A

is a tropical biome dominated by grasses, shrubs, andsmall trees. As Figure 16 shows, rain falls mainly during the wetseason, which lasts for only a few months of the year. This is theonly time that plants can grow. The plants support an amazingvariety of herbivores, such as antelopes, giraffes, and elephants,as well as the predators that hunt them—cheetahs, lions, and hye-nas, for example.

Plants of the Savanna Because most of the rain falls duringthe wet season, plants must be able to survive prolonged pe-riods of time without water. During the dry season, plants losetheir leaves or die down to the ground. When the rain returns,they start to grow again. Many plants have large, horizontalroot systems so they can draw water from as large an area aspossible. The coarse savanna grasses have vertical leaves thatexpose less of their surface area to the hot sun to further helpthe grasses conserve water. Some trees of the savanna also losetheir leaves during the dry season to conserve water. Trees andshrubs often have thorns or sharp leaves that keep hungry herbivores away.

Name two herbivores and two predators thatsavanna plants support.■●✓ Reading Check

savanna

Objectives

� Describe the difference betweentropical and temperate grasslands.

� Describe the climate in a chaparralbiome.

� Describe two desert animals andthe adaptations that help themsurvive.

� Describe one threat to the tundrabiome.

Key Termssavannatemperate grasslandchaparraldeserttundrapermafrost

S E C T I O N 3

Grassland, Desert, and Tundra Biomes

Tropical Savanna(Nairobi, Kenya)

0

10

20

30

40

50

5

15

25

35

45

–60

–40

–20

0

20

40

–50

–30

–10

10

30


Months

Prec

ipit

atio

n (

cm)

Tem

per

atur

e ( ˚C

)

Figure 16 � Savannas have periodsof heavy rainfall followed by periodsof drought.

Section 3 Grassland, Desert, and Tundra Biomes 165


hes08_ch06_165-173_S03 7/27/06 12:47 PM Page 165


Figure 17 � Herbivores of thesavanna, such as the elephants shownhere, range widely in search of food.

Temperate Grassland(Wichita, Kansas)

0

10

20

30

40

50

5

15

25

35

45

–60

–40

–20

0

20

40

–50

–30

–10

10

30


Months

Prec

ipit

atio

n (

cm)

Tem

per

atur

e ( ˚C

)

Figure 18 � Temperate grasslandsare characterized by small amountsof rainfall, periodic droughts, andhigh temperatures in the summer.

GeofactDeep Soil Gravel or sand becomesfertile soil when decomposersslowly break down organic mattersuch as dead leaves. Decomposerswork most effectively in hot, wetweather. As a result, the world’sdeepest soil is in grasslands. In tem-perate grassland biomes, wintersare cold and summers are dry,which causes leaves to break downslowly. So, organic matter builds upover time. Some North Americanprairies had more than 2 m of top-soil when the first farmers arrived.

AAnimals of the Savanna Grazing herbivores, such as the elephantsshown in Figure 17, have adopted a migratory way of life. Theyfollow the rains to areas of newly sprouted grass and wateringholes. Some predators follow and stalk migratory animals for food.Many savanna animals give birth only during the rainy season,when food is most abundant and the young are more likely to sur-vive. Also, some species of herbivores eat vegetation at differentheights than other species do. For example, small gazelles graze ongrasses, black rhinos browse on shrubs, and giraffes feed on treeleaves.

Temperate GrasslandsTemperate grassland covers large areas of the interior of conti-nents, where there is moderate rainfall, but still too little for treesto grow. The prairies in North America, the steppes in Asia, theveldt in South Africa, and the pampas in South America are tem-perate grasslands. Their locations are shown in Figure 18. Twoexamples of temperate grasslands are shown in Figure 19.

Mountains often play a crucial role in maintaining grasslands.For example, in North America, rain clouds moving from thewest release most of their moisture as they pass over the RockyMountains. As a result, the shortgrass prairie just east of theRockies receives so little rain that it looks almost like a desert.

hes08_ch06_165-173_S03 7/27/06 12:48 PM Page 166

The amount of rain increases as you move east, which permitsthe growth of taller grasses and some shrubs. Grassland plantsdry out in the summer, so lightning strikes often start fires.

Plants of Temperate Grasslands Temperate grassland vegetationconsists of grasses and wildflowers. Although there is only a sin-gle layer of vegetation, many species may be present. Shrubs andtrees grow only where the soil contains extra water, usually onthe banks of streams.

The root systems of grassland plants form dense layers thatsurvive drought and fire. Figure 20 shows how the heights ofgrasses and the depths of their roots vary.

Grasslands are highly productive because of their fertile soil.The summer is hot and the winter is cold, so the plants die backto their roots in the winter. Low temperatures in the winter slowdecomposition. As a result, the rate at which dead plants decay isslower than the rate at which new vegetation is added each year.Over time, organic matter accumulates in the soil. This meansthat grasslands have the most fertile soil in the world. Mostgrasslands have been converted to farmland for growing cropssuch as wheat and corn.


Figure 19 � The steppes in Asia (left)and the pampas in South America(right) are dominated by grasses andother plants that are adapted to tem-perate grasslands.

HistoryConnection to

The State of Bison More than60 million bison once roamed thetemperate grasslands of NorthAmerica. But these large grass-eating mammals were almostbrought to extinction by the late1800s because of hunting bywestern settlers. By 1889, fewerthan 1,100 bison remained inNorth America! The first bill tosave the bison was introduced byCongress in 1874. In 1903,President Theodore Rooseveltstarted the National WildlifeRefuge System to provide pro-tected areas for bison and otheranimals. Today, North Americahas more than 200,000 bison.

Shortgrass prairie(about 25 cm rain per year)

Mixed or middlegrass prairie

(about 50 cm rain per year)

Tallgrass prairie(up to 88 cm rain per year)

Figure 20 � The height of grasslandplants and the depth of their rootsdepend on the amount of rainfallthat the grasslands receive.

hes08_ch06_165-173_S03 7/27/06 12:50 PM 7

Animals of Temperate Grasslands Grazing animals, such aspronghorn antelope and bison, have large, flat back teeth forchewing the coarse prairie grasses. Other grassland animals, suchas badgers, prairie dogs, and burrowing owls, live protected inunderground burrows as shown in Figure 21. The burrows shieldthe animals from fire and weather and protect them from preda-tors on the open grasslands.

Threats to Temperate Grasslands Farming and overgrazing havechanged the grasslands. Grain crops cannot hold the soil in placeas well as native grasses can because the roots of crops are shal-low and the soil is ploughed regularly, so soil erosion eventuallyoccurs. Erosion is also caused by overgrazing. When grasses areconstantly eaten and trampled, the grasses cannot regenerate orhold the soil. This constant use can change fruitful grasslandsinto less productive, desertlike biomes.

ChaparralTemperate woodland biomes have fairly dry climates but receiveenough rainfall to support more plants than a desert does. Onetype of temperate woodlands consists of scattered tree communi-ties made up of coniferous trees such as piñon pines and junipers,as shown in Figure 22.

is a temperate shrubland biome that is foundin all fives parts of the world with a Mediterranean climate.These areas have moderately dry, coastal climates, with little or

The chaparral


Figure 21 � Prairie dogs, such asthose shown here, live in temperategrasslands. Prairie dogs live incolonies and burrow in the groundto build mounds, holes, and tunnels.

Figure 22 � Temperate woodlandsare usually too dry to support a for-est, but they receive sufficient pre-cipitation to support vegetation thatgrows in bunches, such as the piñonand juniper trees shown here.

QuickLABSponging It Up

Procedure1. Completely saturate two small

sponges with water and allowthe excess water to drain off.

2. Measure each sponge’s mass byusing an electric balance.Record the mass.

3. Using plastic wrap, completelycover one of the sponges.

4. Place the sponges outside in a sunny place for 10 to 15 minutes.

5. Measure each sponge’s massafter removing it from outside.Record the mass.

Analysis1. Which sponge lost the most

mass? Why?2. How was the covering you cre-

ated for the sponge similar tothe adaptations of the plants inthe chaparral biome?

hes08_ch06_165-173_S03 7/27/06 12:53 PM Page 168

no rain in the summer. Look at the famous white letters that spellHollywood across the California hills in Figure 23. Now imaginethe scrub-covered settings common in old westerns. Both of theselandscapes are part of the chaparral biome. As shown in Figure 24,chaparral is located in the middle latitudes, about 30° north andsouth of the equator.

Plants of the Chaparral Most chaparral plants are low-lying, ever-green shrubs and small trees that tend to grow in dense patches.Common chaparral plants include chamise, manzanita, scrub oak,olive trees, and herbs, such as sage and bay. These plants havesmall, leathery leaves that retain water. The leaves also contain oilsthat promote burning, which is an advantage because natural firesdestroy trees that might compete with chaparral plants for light andspace. Chaparral plants are so well adapted to fire that they canresprout from small bits of surviving plant tissue.

Animals of the Chaparral A common adaptation of chaparral ani-mals is camouflage, which is shape or coloring that allows an ani-mal to blend into its environment. Animals such as quail, lizards,chipmunks, and mule deer have a brownish-gray coloring that letsthem move through the brush without being noticed.

Threats to the Chaparral Worldwide, the greatest threat to chapar-ral is human development. Because chaparral biomes get a lot ofsun, are near the oceans, and have a mild climate year-round,humans tend to develop the land for commercial and residential use.

How does camouflage help chaparral animals?■●✓ Reading Check


Chaparral(Santa Barbara, California)

0

10

20

30

40

50

5

15

25

35

45

–60

–40

–20

0

20

40

–50

–30

–10

10

30


Months

Prec

ipit

atio

n (

cm)

Tem

per

atur

e ( ˚C

)

Figure 24 � Chaparral biomes arelocated in areas that haveMediterranean climates.

Figure 23 � The chaparral biome inthe Hollywood hills is home to plantssuch as the manzanita, which isshown above.

hes08_ch06_165-173_S03 7/27/06 12:54 PM Page 169

DesertsWhen some people think of a desert, they think of the hot sandthat surrounds the Egyptian pyramids. Other people picture theSonoran Desert and its mighty saguaro cactuses, or the magnificentrock formations of Monument Valley in Arizona and Utah. Manykinds of deserts are located throughout the world, but one charac-teristic that they share is that they are the driest places on Earth.

are areas that have widely scattered vegetation and re-ceive very little rain. In extreme cases, it never rains and there is novegetation. The distribution of Earth’s deserts is shown in Figure 25.Even in hot deserts near the equator, there is so little insulatingmoisture in the air that the temperature changes rapidly during a24-hour period. The temperature may go from 40°C (104°F) duringthe day to near-freezing at night. Deserts are often located nearmountain ranges, which block the passage of rain clouds.

Deserts

Desert(Cairo, Egypt)

0

10

20

30

40

50

5

15

25

35

45

–60

–40

–20

0

20

40

–50

–30

–10

10

30


Months

Prec

ipit

atio

n (

cm)

Tem

per

atur

e ( ˚C

)

Figure 25 � Deserts are the driestplaces on Earth. They typicallyreceive less than 25 cm of precipita-tion a year.

170 Chapter 6 Biomes170

� The flapnecked chameleon livesin the deserts of Botswana.

� The Sonoran Desert in Arizonaappears lush with plant life justafter the winter rains.

hes08_ch06_165-173_S03 7/27/06 12:55 PM Page 170

Plants of the Desert All desert plants have adaptations forobtaining and conserving water, which allow the plants to live indry, desert conditions. Plants called succulents, such as cactuses,have thick, fleshy stems and leaves that store water. Their leavesalso have a waxy coating that prevents water loss. Sharp spineson cactuses keep thirsty animals from devouring the plant’s juicyflesh. Rainfall rarely penetrates deeply into the soil, so manyplants’ roots spread out just under the surface of the soil toabsorb as much rain as possible.

Many desert shrubs drop their leaves during dry periods andgrow new leaves when it rains again. When conditions are too dry,some plants die and drop seeds that stay dormant in the soil untilthe next rainfall. Then, new plants quickly germinate, grow, andbloom before the soil becomes dry again. Some desert plants haveadapted so that they can survive even if their water content dropsto as low as 30 percent of their mass. Water levels below 50 to 75 percent are fatal for most plants.

Animals of the Desert Reptiles, such as Gila monsters and rattlesnakes, have thick, scaly skin that prevents water loss.Amphibians, such as the spadefoot toad, survive scorching desertsummers by estivating—burying themselves in the ground andsleeping through the dry season. Some animals, such as the elfowl shown in Figure 26, nest in cactuses to avoid predators.Desert insects and spiders are covered with body armor that helpsthem retain water. In addition, most desert animals are nocturnal,which means they are active mainly at night or at dusk, when theair is cooler.


Figure 26 � Desert plants surviveharsh conditions by growing deeproots to reach groundwater and byhaving specialized structures thatlimit the loss of water. Desert animalsbury themselves underground or bur-row in cactuses to avoid extremetemperatures and predators.

FIELD ACTIVITYFIELD ACTIVITY Miniature Desert Create aminiature desert by growing asmall cactus garden. Purchasetwo or three small cactus plants,or take several cuttings from alarge cactus. To take cuttings,carefully break off the shootsgrowing at the base of the parentcactus. Place the plants in rockyor sandy soil similar to the soil ina desert. Keep the cactuses inbright sunlight, and do not waterthem frequently. Record yourobservations of your cactus gar-den in your Ecolog.

� Elf owls burrow in cactuses to avoidhot temperatures during the day.

� This sidewinder has a unique wayof moving so that only small portionsof its body are in contact with thehot sands at any one time.

hes08_ch06_165-173_S03 7/27/06 12:56 PM Page 171

TundraThe biome is located in northern arctic regions, as shownin Figure 27. The winter is too cold and dry to permit the growthof trees in this biome. In many areas of the tundra, the deeperlayers of soil, called are permanently frozen through-out the year. As a result, the topsoil is very thin. In the summer,when the thin topsoil layer thaws, the tundra landscape becomesquite moist and spongy and is dotted with bogs. These wet areasare ideal breeding grounds for enormous numbers of swarminginsects, such as mosquitoes and black flies, and for the manybirds that feed on the insects.

Vegetation of the Tundra Figure 28 shows the Alaskan tundra inthe summer. Mosses and lichens, which can grow without soil, covervast areas of rocks in the tundra. The soil is thin, so plants havewide, shallow roots to help anchor them against the icy winds. Mostflowering plants of the tundra, such as campion and gentian, areshort. Growing close to the ground keeps the plants out of the windand helps them absorb heat from the sunlit soil during the brief sum-mer. Woody plants and perennials such as willow and birch haveevolved dwarf forms and grow flat or grow along the ground.

permafrost,

tundra

172 Chapter 6 Biomes172

Tundra(Reykjavik, Iceland)

0

10

20

30

40

50

5

15

25

35

45

–60

–40

–20

0

20

40

–50

–30

–10

10

30


Months

Prec

ipit

atio

n (

cm)

Tem

per

atur

e ( ˚C

)

Figure 27 � The precipitation thatthe tundra biome receives remainsfrozen much of the year.

Figure 28 � During its brief summer,the Alaskan tundra is covered byflowering plants and lichens.

Venn DiagramCreate the

Graphic Organizer entitled“Venn Diagram” described in theAppendix. Label the circles with“Tundra” and “Desert.” Then, fillin the diagram withcharacteristics thateach biome shareswith the other.

hes08_ch06_165-173_S03 7/27/06 12:57 PM Page 172

Animals of the Tundra Millions of migratorybirds fly to the tundra to breed in the summer.Food is abundant in the form of plants, mollusks,worms, and especially insects. Caribou, shown inFigure 29, migrate throughout the tundra insearch of food and water. Wolves roam the tun-dra and prey on caribou, moose, and smaller ani-mals, such as lemmings, mice, and hares. Theseanimals burrow underground during the winterbut they are still active. Many animals that live inthe tundra year-round, such as arctic foxes, lose their brown fur andgrow white fur that camouflages them with the winter snow. Theseanimals are also extremely well insulated.

Threats to the Tundra The tundra is one of the most fragilebiomes on the planet. Its food chains are relatively simple, so theyare easily disrupted. Because conditions are so extreme, the land iseasily damaged and slow to recover. Until recently, the tundra wasundisturbed by humans. But oil has been located in some tundraregions, such as in northern Alaska. Oil exploration, extraction,and transport has disrupted the habitats of the plants and animalsin many parts of the tundra. Pollution caused by spills or leaks ofoil and other toxic materials may also poison the food and watersources of the organisms that live in the tundra.


1. Describe two desert animals and the adaptationsthat help them survive.

2. Describe how tropical grasslands differ from temper-ate grasslands.

3. Compare the plants that live in deserts with theplants that live in the tundra biome.

4. Describe one threat to the tundra biome.

CRITICAL THINKING5. Making Inferences Former grasslands are among

the most productive farming regions. Read thedescription of temperate grasslands in this sectionand explain why this statement is true.

6. Analyzing Relationships Explain why elephantsand caribou, which live in very different biomes, bothmigrate.

READING SKILLS


079_PFPO

Figure 29 � Many migratory ani-mals, such as geese (left) and caribou(below), return to the tundra eachyear to breed.

MATHPRACTICEU.S. Oil Production Onaverage, the United States produces an estimated 8.1 million barrels of oil per day. Howmany millions of barrels of oil doesthe United States produce in 1 year?If all of the oil-producing countriesof the world produce an estimated74.13 million barrels of oil per day,what percentage of worldwide oildoes the United States produce?

hes08_ch06_165-173_S03 7/27/06 12:58 PM Page 173

HighlightsC H A P T E R 6

1 What Is a Biome?

2 Forest Biomes

3 Grassland, Desert, andTundra Biomes

KKey Termsbiome, 153climate, 154latitude, 155altitude, 155

Main Ideas� Scientists classify the ecosystems of the worldinto large areas called biomes.

� Biomes are described by their plant lifebecause specific climate conditions support thegrowth of specific types of vegetation.

� Climate determines which plants can grow inan area. Latitude and altitude affect climate insimilar ways.

tropical rain forest,156

emergent layer, 158canopy, 158epiphyte, 158understory, 158temperate rain

forest, 161temperate deciduous

forest, 162taiga, 163

� Major forest biomes include tropical rainforest, temperate rain forest, temperate decidu-ous forest, temperate evergreen forest, andtaiga.

� Tropical rain forests have high rainfall andhigh temperatures throughout the year. Theyare the most diverse of all biomes.

� Temperate forests experience seasonal varia-tions in precipitation and temperature. Theirvegetation is adapted to surviving thesechanges.

� Forest biomes are threatened by deforesta-tion through logging, ranching, and farming.

savanna, 165temperate grassland,

166chaparral, 168desert, 170tundra, 172permafrost, 172

� Savannas are located north and south oftropical rain forests and have distinct wet seasons.

� Temperate grasslands get too little rainfall tosupport trees. Grasslands are dominated mostlyby different types of grasses and floweringplants.

� Deserts are the driest biomes on Earth.

� Plants and animals found in each biomeadapt to the environment in which they live.

174 Chapter 6 Highlights

hes08_ch06_174-177_HCR 8/18/06 11:11 AM Page 174

Review

Chapter 6 Review 175

Using Key TermsUse each of the following terms in a separatesentence.

1. biome2. climate3. epiphyte4. tundra5. permafrost

For each pair of terms, explain how the meaningsof the terms differ.

6. understory and canopy7. latitude and altitude8. chaparral and desert9. tropical rain forest and temperate deciduous

forest

Understanding Key Ideas10. Approximately what percentage of the Earth’s

species do tropical rain forests contain?a. 7 percentb. 20 percentc. 40 percentd. 50 percent

11. Animal species of the tropical rain foresta. compete more for available resources than

species native to other biomes do.b. have adaptations that minimize

competition.c. have adaptations to cope with extreme

variations in climate.d. are never camouflaged.

12. Migration of animals in the savanna ismostly a response toa. predation.b. altitude.c. rainfall.d. temperature.

13. Spadefoot toads survive the dry conditionsof the desert bya. migrating to seasonal watering holes.b. finding underground springs.c. burying themselves in the ground.d. drinking cactus juice.

14. The tundra is most suitable to a vertebratethata. requires nesting sites in tall trees.b. is coldblooded.c. has a green outer skin for camouflage.d. can migrate hundreds of kilometers each

summer.15. A biome that has a large amount of rainfall,

high temperatures, and poor soil is aa. temperate woodland.b. temperate rain forest.c. tropical rain forest.d. savanna.

16. The two main factors that determine whereorganisms live area. soil type and precipitation.b. temperature and precipitation.c. altitude and precipitation.d. temperature and latitude.

17. Which of the following biomes containslarge trees?a. savannab. temperate rain forestc. chaparrald. desert

18. The most common types of plants in thetaiga biome area. deciduous trees.b. short shrubs.c. coniferous trees.d. grasses.

C H A P T E R 6

Concept Maps Remembering words and under-standing concepts are easier when information isorganized in a way that you recognize. For exam-ple, you can use key terms and key concepts tocreate a concept map that links them together ina pattern you will understand and remember.

STUDY TIP

hes08_ch06_174-177_HCR 8/18/06 11:12 AM Page 175

Savanna

Temperate grasslandTemperate forest Desert

Temperate

Tropical

Subarctic

Arctic

Taiga

Tundra

Tropical rain forest Desert

DryWet

HotD

ecre

asin

g te

mpe

ratu

re

Cold

Decreasing moisture

ReviewSShort Answer19. Unlike the jungles you see in movies, the

floor of an undisturbed tropical rain forestusually has little vegetation. Explain why itlacks vegetation.

20. What is the relationship between root sys-tems and erosion in a grassland ecosystem?

21. How might a mountain affect where particu-lar types of biomes are located?

22. Well-preserved mammoths have been foundburied in the tundra. Explain why the tundrapreserves animal remains well.

23. How does deforestation contribute to achange in climate and increase the chance offloods in a biome?

Interpreting GraphicsUse the diagram below to answer questions24–26.24. Why are tall trees found in the taiga but not

in the tundra?25. As moisture decreases, what happens to the

amount of vegetation in an area?26. What does the diagram tell you about the

temperature of and precipitation in temper-ate grasslands?

Concept Mapping27. Use the following terms to create a concept

map: threats to an ecosystem, erosion, over-grazing, logging, grasslands, rain forests,tundra, deserts, oil extraction, and irrigation.

Critical Thinking28. Comparing Processes American prairies and

Asian steppes contain different plant speciesbut are dominated by grasses. Write a shortparagraph that explains why the two grass-lands contain different species but the sametypes of plants.

29. Classifying Information Read the descrip-tion of tropical rain forests in this chapter,and list two factors that are responsible forthe biodiversity of this biome. Describe tworeasons for the decline of tropical rainforests.

30. Analyzing Relationships If you took a popu-lation of squirrels from the southeasternUnited States and introduced them into aCentral American rain forest, they wouldprobably not survive. Why do you think thesquirrels would not survive even though theyare naturally adapted to life in a forest?

31. Making Inferences How might prairie firesset from natural and human causes haveaffected the evolution of fire resistance inprairie grasses?

Cross-Disciplinary Connection32. Geography Use a world map to find loca-

tions of the various biomes. Then, make aposter that contains photos or illustrationsof plants and animals native to each biome.

Portfolio Project33. Food Webs in Your Biome Do a special proj-

ect on the ecosystems in your biome. Use fieldguides to find out what plants and animalslive in your biome. Then, draw a food webthat shows how organisms in each ecosystemcould be related.

READING SKILLS

WRITING SKILLS

C H A P T E R 6

176 Chapter 6 Review

?

? ?

hes08_ch06_174-177_HCR 8/18/06 11:12 AM Page 176

Chapter 6 Review 177

Read the passage below, and then answerthe questions that follow.

The Tropics and other regions of high biodi-versity include some of the economically poor-est countries on Earth. These countries aretrying to use their natural resources to buildtheir economies and to raise the standard ofliving for their citizens. Several conservationstrategies offer ways for developing countriesto benefit economically from preserving theirbiodiversity.

For example, in a debt-for-nature swap,richer countries or private conservationorganizations pay some of the debts of adeveloping country. In exchange, the devel-oping country agrees to take steps to protectits biodiversity, such as setting up a preserveor launching an education program for itscitizens. Another idea to help local peoplemake money from intact ecosystems is to setup a national park to attract tourists. Peoplewho want to see the ecosystem and itsunique organisms will pay money for natureguides, food, and lodging. This idea is calledecotourism.

1. The main objective of both a debt-for-nature swap and ecotourism isa. economic gain.b. education of citizens. c. preservation of biodiversity.d. Both (a) and (c)

2. According to the passage, which of thefollowing statements is true?a. Regions of high biodiversity are not

worth saving.b. Intact ecosystems are ecosystems that

are most developed.c. A debt-for-nature swap is an example

of international compromise.d. Launching education programs for citi-

zens does not help protect ecosystems.

MATH SKILLS

Use the table below to answer quesions 34–35.

34. Making Calculations What percentage oftropical rain forest is being destroyed eachyear in country A? in country D?

35. Interpreting Statistics According to thetable, which country’s tropical rain forestwill be completely destroyed first? Whichcountry’s rain forest will be completelydestroyed last?

WRITING SKILLS

36. Communicating Main Ideas Describe theimportance of conserving the biomes of theworld. What can you do to help conserve theworld’s biomes?

37. Writing From Research Choose one biomeand research the threats that exist against it.Write a short essay that describes the threatsand any actions that are being taken to helpsave the biome.

Amount of Tropical Rainforest

Amount ofAmount of annualtropical rain deforestation

Country forest (km2) (km2/y)

A 1,800,000 50,000

B 55,000 3,300

C 22,000 6,000

D 530,000 12,000

E 80,000 700

READING SKILLS

hes08_ch06_174-177_HCR 7/27/06 1:06 PM Page 177

C H A P T E R 6 Standardized Test PrepUnderstanding ConceptsDirections (1–4): For each question, write on aseparate sheet of paper the letter of the correctanswer.

1 Which of the following describes a biome?A. all the areas on Earth that are life-

supportingB. weather conditions in an area for a

specific time periodC. a region characterized by specific climate

and organism communitiesD. an area where the animal population

interacts with its abiotic environment

2 What type of forest has the greatest biodiversity?F. taiga forestG. temperate deciduous forestH. temperate rain forestI. tropical rain forest

3 What is the diversity of the species in anarea dependent on?A. plant lifeB. rainfallC. sunlightD. temperature

4 What are the main factors that determineweather?F. altitude, latitude, precipitation,

temperatureG. altitude, latitude, precipitation,

vegetationH. air currents, altitude, temperature,

vegetationI. air currents, precipitation, temperature,

vegetation

Directions (5–6): For each question, write a shortresponse.

5 A temperate grassland is a biome that isdominated by grasses and that has very fewtrees. How are temperate grasslands threat-ened by overgrazing?

6 Compare and contrast the tundra anddesert biomes.

Reading SkillsDirections (7–8): Read the passage below. Thenanswer the questions.

When rain falls on a forest, much of the rainis absorbed by plant roots and transpired intothe air as water vapor. The water vapor forms rain clouds. Much of the water in the cloudswill fall as rain somewhere downwind fromthe forest. Clearing the trees results in defor-estation, which can change the climate.

Deforestation led to the disastrous floodingof the Yangtze River in China in 1998. More than 2,000 people died in the floods,and at least 13 million people had to leavetheir homes. It is estimated that 85 percent of the forest in the Yangtze River basin hasbeen cut down. So the millions of tons ofwater these trees once absorbed now flowsfreely down the river and spreads across thefields into towns during the seasonal monsoonrains.

7 How could future flooding on the YangtzeRiver be avoided?A. replanting cropsB. rebuilding homesC. replanting treesD. rebuilding walls

8 Examine the climate change produced bydeforestation.

Directions (9): Read the passage below. Thenanswer the question.

Tropical rain forests are located in a beltaround the Earth near the equator. The climateis ideal for a wide variety of plants and ani-mals. In tropical rain forests, different types ofplants grow in different layers. The main lay-ers above the forest floor are, in order fromtop to bottom, the emergent layer, the canopy,and the understory.

9 Which layer of a tropical rain forestreceives the least sunlight, and why?

178 Chapter 6 Standardized Test Prep

hes08_ch06_178-179_STP 8/18/06 11:38 AM Page 178

TestWhen several ques-tions refer to the samegraph, table or map,answer the questionsyou are most sure of first.

Chapter 6 Standardized Test Prep 179

Interpreting GraphicsDirections (10–13): For each question below, record the correct answer ona separate sheet of paper.

Different scientists classify biomes in different ways. The map below showsone way to classify the biomes in Africa. Use this map to answer questions10 through 13.

Biomes of Africa

0 What can be inferred about the biomes of Africa?F. Africa has a large concentration of tropical rain forests.G. Africa has a limited number of plant and animal communities.H. Africa has all types of plant life because of the many diverse

biomes.I. Africa has large desert areas that get less than 25.0 cm of precipita-

tion a year.

q Which biome covers the most surface area in Africa?A. desert C. MediterraneanB. highland D. steppe

w According to the map, which of the following determines the characteristics of a biome?F. geographic borders H. longitudeG. latitude I. the Indian ocean

e What geographic features are near 10°N, 40°E?A. mountains C. riversB. plains D. volcanoes

LEGEND

Humid tropicalTropical savannaDesertSteppeMediterraneanMarine west coastHighland

N

W E

S

1,000 Kilometers

1,000 Miles500

500

0

0

SCALE

10°E

0°10°W

20°W

Equator

20°N

30°N

20°S

10°S

10°N

30°S 40°E

50°E

INDIANOCEAN

ATLANTICOCEAN

RED SEA

Tropic ofCancer

Tropic of Capricorn

MEDITERRANEANSEA

hes08_ch06_178-179_STP 7/27/06 1:09 PM Page 179

180 Chapter 6 Exploration Lab

Identify Your Local BiomeIn what biome do you live? Do you live in a temperate deciduousforest, a desert, or a temperate grassland, such as a prairie orsavanna? In this lab, you will explore certain characteristics ofthe biome in which you live. With the information you gather,you will be able to identify which biome it is.

Procedure1. Use a globe or atlas to determine the latitude at which you

live. Record this information.2. Consider the topography of the place where you live. Study

the contour lines on a map or surface variations on a globe.What clues do you find that might help identify your biome?For example, is your area located near a mountain or anocean? Record your findings.

3. Prepare a climatogram of your area. A climatogram is agraph that shows average monthly values for two factors:temperature and precipitation. Temperature is expressed indegrees Celsius and is plotted as a smooth curve. Precipitationvalues are given in centimeters and are plotted as a histogram.

To make a climatogram of your area, obtain monthlyaverages of precipitation and temperature for one year fromyour local TV or radio weather station. Make a data table,and record these values. Next, draw the vertical and hori-zontal axes of your climatogram in your notebook or ongraph paper. Then, show the temperature scale along thevertical axis on the right side of the graph and the precipita-tion scale along the vertical axis on the left side of thegraph. Show months of the year along the horizontal axis.Finally, plot your data.

Objectives� Collect information from interna-

tional, national, and local resourcesabout the biome in which you live.

� Performfield observations to identify thename of the biome in which you live.

Materialsbinoculars (optional)field guide to local flora and

faunaglobe or atlasgraph paper (optional)notebookpencil or penruler

USING SCIENTIFIC METHODS

Exploration Lab: FIELD ACTIVITYC H A P T E R 6

Tem

per

atur

e ( ˚C

)

–60

–40

–20

0

20

40

–50

–30

–10

10

30

MonthsDJ F M A M J J A S O N

0

10

20

30

40

50

5

15

25

35

45

Prec

ipit

atio

n (

cm)

Austin, Texas (2000)

� Climatograms The temperatureand precipitation for Austin, Texas isshown in this climatogram.

hes08_ch06_180-181_EXP 8/18/06 11:39 AM Page 180

Chapter 6 Exploration Lab 181

4. Go outside to observe the plants growing in your area. Bringa field guide, and respond to the following items in yournotebook.a. Sketch or describe as many plants that are common in

your area as you can. Use your field guide to identify each of these species.

b. Describe three or more adaptations of each plant to thelocal climate.

c. Which of the plants that you observed are native to yourarea? Which have been introduced by humans? Which ofthe introduced plants can survive on their own in localconditions? Which of the introduced plants requireextensive human care to remain alive?

d. Look for evidence that animals have left behind—footprints, nests, dens or burrows, hair or feathers,scratches, or urine markings. Sketch or describe as manydifferent animal species as possible. Identify each speciesby using your field guide.

e. Describe three or more adaptations that each animal hasdeveloped in order to survive in local climatic conditions.

Analysis1. Analyzing Data Compare your local climatogram to the

biome climatograms shown in this chapter. Which biome hasa climatogram most similar to your climatogram?

2. Analyzing Results Consider your latitude, topographicalfindings, and observations of local plants and animals.Combine this information with your climatogram, and deter-mine which biome best matches the area in which you live.

Conclusions3. Evaluating Results Does your climatogram match any of the

seven major terrestrial climatograms shown in the chapter?Explain how any differences between your biome and thebiome in the chapter that your biome most clearly matchesmight influence the adaptations of local animals and plants.

4. Applying Conclusions Organisms create features of thebiome in which they live. What features of your biome arecreated by the organisms that live there?

1. Classifying Information Name the three plant adaptationsand the three animal adaptations that you observed.Explain in detail how each of these adaptations meets theconditions of your biome.

Extension

� Biomes These two cities are locatedin two different biomes. Stamford,Vermont (top) is located in a temper-ate deciduous forest, and Tucson,Arizona (bottom) is located in a desert.

hes08_ch06_180-181_EXP 7/27/06 1:12 PM Page 181

A LITTLE PIECE OF CAJUN PRAIRIE

182 Chapter 6 Making a Difference

Cajun prairie is a distinct grassland,named for the settlers who livedthere. It once covered more than2.5 million acres of southwestLouisiana. Today, only about 100acres of Cajun prairie remain. If the work of two biologists andmany volunteers pays off, how-ever, a little piece of Cajun prairiewill always exist in Louisiana.

“I think that saving Cajunprairie is important because once itis gone, you cannot bring it back,”says Charles Allen, a retired profes-sor from the University of Louisi-ana and the botanist for Louisiana’sFort Polk. “There are plants andanimals there that have never beentested for uses by humans. Wecould be losing a plant that wouldcure cancer, or provide food orfiber,” he says.

Allen and biologist MalcolmVidrine, a professor of biology at Louisiana State University inEunice, have been working foralmost two decades to restoreCajun prairie.

Although Cajun prairie and the tallgrass prairies of the Mid-west both belong to the temperategrassland biome, Cajun prairie soilhas unique characteristics. It is

made of tight, heavy clays thatformed as a result of coastal flood-ing and rains. This soil, combined with frequent light-ning fires, makes it difficult for treesto grow but easy for prairie plants to flourish.

Settling on the PrairieIn the mid-1700s, many French Aca-dians, also known as Cajuns, arrivedin Louisiana from Nova Scotia,Canada. They sustained themselvesfor over 100 years by fishing, hunt-ing, and some farming. They alsosustained their environment becausetheir lifestyle caused little damage tothe prairie.

The establishment of the rail-road in the late 1800s brought newsettlers to farm the rich land. Thesesettlers brought with them new,more intensive agricultural practicesand established herds of cattle thatovergrazed the vegetation. By the early 20th century, most of the Cajun prairie had disappeared.

Today, the Cajun prairie eco-system is labelled as “imperiledglobally” by the Nature Conser-vancy, an organization dedicated to preserving natural communities.There are now fewer than 100 acresof Cajun prairie left in Louisiana. The railroad led to the near dis-appearance of the prairie, but ithas also played an important role

� Charles Allen is shown here collecting seeds from a compassplant at a Cajun prairie remnant.The leaves of the compass plantface east to catch the sun.


� Cajun prairie, preserved on this 10-acre site,once covered nearly 10 percent of Louisiana.

hes08_ch06_182-183_FEA 7/27/06 1:13 PM Page 182

Chapter 6 Making a Difference 183

What Do You Think?Are there threatened habitatsin your area? What factors do you think led to the loss of these habitats? Is it possiblefor people to settle in a habitatwithout having a negativeimpact? How were the Cajunsable to sustain themselves onthe prairie without destroyingthe habitat?

in saving the last remaining piecesof prairie. The remaining prairie ismostly in remnants of small, nar-row strips along railroad right-of-ways. Because the railroad ownedthese pieces of land, they werenever farmed.

The Eunice Cajun PrairieRestoration ProjectIn the late 1980s, Allen and Vidrinelocated as many remnant strips asthey could. They chose 10 of thestrips and studied them carefully.They found almost 500 species ofplants in the 10 strips.

The Eunice Cajun Prairie Restor-ation Project began in the summerof 1988. Its goal was to restore andpreserve a small Cajun prairie in thecity of Eunice, Louisiana.

A 10-acre site in Eunice wasmowed, and herbicide was used todestroy the nonnative vegetation.Volunteers from local elementaryand high schools collected bags of seeds from Cajun prairie plants

growing in the remnant strips. Thatwinter, controlled burns were usedto prepare the site. On a designatedplanting day, the students spreadthe seeds they had collected. Thesite was then lightly tilled. Sod wasremoved from the remnant stripsand replanted at the Eunice siteduring the next three seasons.

Restoration is an ongoing effort.Yearly controlled burns maintainthe habitat. The fires destroy shrubsand trees, but do not kill most ofthe prairie plants. Spot herbicidesare used on the more pervasive non-native species, such as the Chinesetallow tree, the most threateningnonnative species for the prairie.The seeds of this tree are easilyspread when birds eat the seedsand deposit them in droppings.

Today, nearly 300 native Cajunprairie species, including little blue-stem, Eastern gama grass, blazingstars, and hairy sunflower, have been reestablished at the site. Aswell, the rare wild coco orchid

(Eulophia ecrista) has been found at the site. This is a very positivesign because few of these orchidshave been found in the remnantstrips or in Louisiana. Much of the Eunice site is now almost com-pletely Cajun prairie.

� To maintain the habitat, volun-teers remove nonnative vegetationsuch as this vasey grass.

� Volunteers such as these students used seeds and sodgathered from remnants to create a new Cajun prairiehabitat in Eunice, Louisiana.

hes08_ch06_182-183_FEA 7/27/06 1:14 PM Page 183

hes08 ch06 152-155 s01 8/18/06 10:41 am page 152 biomes

Documents