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Chapter 17 Biomes and Ecosystems

Land BiomesKey Concept The kinds of plants and animals thatlive in a biome are determined by the local climate.

Why are some organisms common in some areas and notin other areas? Each biome has organisms that are adapted tothe conditions in the biome, such as climate. Organisms arealso adapted to using the nonliving and living resources intheir biome. Therefore, there are many kinds of organisms ineach biome. Each organism in a biome can be categorized as aproducer, a consumer, or a decomposer.

DesertsVery dry, and often very hot biomes are called deserts,deserts, such

as the Mojave Desert in California. Many plants and animalsare found only in deserts, and have special adaptations to livein a desert. For example, some plants have widespread roots justunder the surface to take up water during a storm. Plants alsooften grow far apart, reducing the competition for water.

In order to survive in a desert, some animals are active onlyat night, when it is cooler. Some animals, such as the fringe-toed lizard, bury themselves in the loose sands. Doing so helpsthese animals escape the heat and avoid predators. Fringe-toedlizards are omnivores that eat insects and parts of plants. Des-ert tortoises are herbivores that eat flowers or leaves and storewater in a large bladder under their shells. Figure 1 shows howsome plants and animals live in the desert.

Name one adaptation that allows desert plantsto survive with little water. 6.5.e

What You Will Learn• Abiotic factors, such as soil, water,

and climate, affect the organismsin land biomes.

• Organisms can be categorizedby their role in an environment.

• Different kinds of organisms canhave similar ecological roles inevery biome.

Why It MattersOrganisms that thrive in a biome areadapted to the climate of the biome.

Vocabulary• desert • grassland• chaparral • tundra

Graphic Organizer In your ScienceJournal, make a Comparison Tablethat compares the characteristics ofdifferent land biomes.

Huge ears helpjack rabbits get ridof body heat.

Some fl owering plantsbloom, bear seeds, anddie within a few weeksafter a heavy rain.

Kangaroo rats do notneed to drink. Theyrecycle water from thefoods that they eat.

Cactuses storewater in theirstems and roots.

Figure 1 The residents ofthe desert biome have specialadaptations to survive in a dryclimate.

Desert

• Average Yearly Rainfallless than 25 cm (10 in.)

• Average TemperaturesSummer: 38ºC (100ºF)Winter: 7ºC (45ºF)

Section 2 Land Biomes 585

ChaparralA biome that has a fairly dry climate but receives only

a little more rainfall than a desert does is called a chaparral.chaparral.In chaparral biomes, summers are warm and dry and wintersare mild and wet. Chaparral can be found in California andaround the Mediterranean Sea.

Chaparral is characterized by low-lying, broad-leaved ever-green shrubs and small trees that grow in dense patches, asshown in Figure 2. Evergreen plants are plants that keep theirleaves all year round. Common chaparral plants include man-zanita, scrub oak, and herbs. These plants have leathery leavesthat help store water. During natural fires, chaparral shrubsand trees are destroyed. After a fire, the chaparral shrubs growback more quickly than trees do. Therefore, natural fires pre-vent the trees from competing with the chaparral shrubs forresources such as sunlight, water, and nutrients. Natural firesare an abiotic factor that help maintain the chaparral.

Animals in the chaparral are also adapted to living in thisbiome. Quail, lizards, chipmunks, and mule deer are usuallygray and brown, which allow them to blend into their sur-roundings and hide from predators. Mule deer are herbivoresthat eat grasses and shrubs. Quails, lizards, and chipmunks areomnivores that eat insects and parts of plants. Bobcats, grayfoxes, and coyotes are carnivores that prey on many of theseorganisms. Coyotes also prey on bobcats and gray foxes.

Identify the ecological role of a shrub from thechaparral and a cactus from the desert. 6.5.c, 6.5.d

6.5.c Students know populations of organisms canbe categorized by the functions they serve in anecosystem.6.5.d Students know different kinds of organismsmay play similar ecological roles in similar biomes.6.5.e Students know the number and types oforganisms an ecosystem can support dependson the resources available and on abiotic factors,such as quantities of light and water, a range oftemperatures, and soil composition.

desertdesert (DEZ uhrt) a region that haslittle or no plant life, long periodswithout rain, and extreme tempera-tures; usually found in hot climates

chaparralchaparral (SHAP uh RAL) a type ofvegetation that includes broad-leavedevergreen shrubs and that is locatedin areas with hot, dry summers andmild, wet winters

Figure 2 Plants of the chaparralare adapted to recovering quicklyafter a natural fire.

Chaparral

• Average Yearly Rainfall25 to 43 cm (10 to 17 in.)

• Average TemperaturesSummer: 22ºC (71.6ºF)Winter: 17.8ºC (64ºF)

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GrasslandsA grasslandgrassland is a biome in which the vegetation is mainly

grasses, small flowering plants, and few trees. Grasslands arefound on every continent except Antarctica. Grasslands canbe divided into two main groups: temperate grasslands, suchas prairies, and tropical grasslands, such as savannas.

PrairiesIn temperate grasslands, such as prairies, the summers are

warm, and the winters are very cold. Prairie soils are rich innutrients because of thousands of years of decomposition. Fires,drought, and grazing prevent the growth of trees and shrubs.Prairies support small seed-eating animals, including prairiedogs and mice. Prairie dogs and mice use camouflage and bur-rows to hide from predators, such as the coyote. Large herbi-vores, such as the North American bison, shown in Figure 3, alsolive in prairies.

SavannasA tropical grassland that has seasonal rains and scattered

clumps of trees is called a savanna. Savannas are found in Africa,India, and South America. During the dry season, savannagrasses dry out and turn yellow. But the grasses’ roots survivefor many months without water. The African savanna is hometo many large herbivores, such as elephants, giraffes, zebras,and wildebeests. Lions and leopards prey on these herbivores.Scavengers, such as hyenas, will eat anything that predatorsleave uneaten. Some of these animals are shown in Figure 4.

Name an animal from the savanna that plays thesame ecological role as the North American bison. 6.5.c, 6.5.d

Chapter 17

Figure 3 Bison areherbivores that once roamedNorth American prairies ingreat herds.

Figure 4 In the Africansavanna, lions and leopardshunt zebras and wildebeests.

Local EcosystemsWith a family member, explorethe ecosystems around yourhome. What kinds of plantsand animals live in your area?In your Science Journal, writea paragraph describing theplants and animals in theecosystems near your home.

Prairie

• Average Yearly Rainfall25 to 75 cm (10 to 29.5 in.)

• Average TemperaturesSummer: 30ºC (86ºF)Winter: 0ºC (32ºF)

Savanna

• Average Yearly Rainfall150 cm (59 in.)

• Average TemperaturesDry season: 34ºC (93ºF)Wet season: 16ºC (61ºF)

Section 2 Land Biomes 587

TundraImagine a place on Earth that is too cold for trees to grow.

A tundratundra is a biome that has very cold temperatures and littlerainfall. Tundras can be found near the North and South Poles.In a tundra, the layer of soil beneath the surface soil staysfrozen year-round. This layer is called permafrost. Permafrostis made up of gravel and some finer materials.

During the short, cool summers, only the surface soil thaws.The surface soil is too shallow for deep-rooted plants to live.So, shallow-rooted plants, such as grasses and small shrubs, arecommon. Mosses and lichens (LIE kuhnz) grow beneath theseplants. These plants, mosses, and lichens grow in clumps andlow to the ground to resist the winds and the cold.

Animals of the tundra also have adaptations for living inthis biome. Some animals, such as bears, hibernate in the win-ter, when food is hard to find, and the cold weather is harsh.Other animals, such as the caribou shown in Figure 5, migrateover large distances to find food. Many animals in the tundraalso have extra layers of fat to keep them warm through thewinter. During summer, the soil above the permafrost becomesmuddy from melting ice and snow. Insects, such as mosquitoes,lay eggs in the mud. Birds that prey on these insects are car-nivores. Other carnivores, such as wolves, prey on herbivores,including musk oxen and caribou.

How are the ecological roles of a lion in a savannaand a wolf in a tundra similar? 6.5.c, 6.5.d

grasslandgrassland (GRAS LAND) a region thatis dominated by grasses, that hasfew woody shrubs and trees, that hasfertile soils, and that receives moder-ate amounts of seasonal rainfall

tundratundra (TUHN druh) a treeless plainfound in the Arctic, in the Antarctic,or on the tops of mountains that ischaracterized by very low winter tem-peratures and short, cool summers

Figure 5 During winters inthe tundra, caribou migrate tograzing grounds that have amore plentiful supply of food.

Tundra

• Average Yearly Rainfall30 to 50 cm (12 to 20 in.)

• Average TemperaturesSummer: 12ºC (54ºF)Winter: –26ºC (–15ºF)

Chapter 17 Biomes and Ecosystems588

ForestsForest biomes receive plenty of rain, and the temperatures

are not extreme. As in every biome, the kind of forest biome that develops depends on the climate of the biome. Three for-est biomes are coniferous (koh NIF uhr uhs) forests, temperate deciduous (dee SIJ oo uhs) forests, and tropical rain forests.

Coniferous ForestsMost of the trees in a coniferous forest are called conifers.

Conifers produce seeds in cones. Conifers also have special needle-shaped leaves covered in a thick, waxy coating. These characteristics prevent water loss and protect the needles from cold damage. Most conifers are evergreens because they keep many of their leaves year-round. Because decomposition is slow, the ground beneath large conifers is often covered by a thick layer of needles. Also, very little light reaches the ground, so few large plants grow beneath conifers.

Figure 6 shows a coniferous forest and some of the animals that live there. Squirrels and insects live in coniferous forests. Birds, such as finches, chickadees, and jays, are also common in these forests. Like squirrels, these birds are omnivores because they eat plants, seeds, and insects. Herbivores, such as porcu-pines, elk, and moose, also live in coniferous forests.

Herbivores that live in the coniferous forest include deer, moose, porcupines, and squirrels.

A coniferous forest is home to many insects and to birds that eat those insects.

Figure 6 Many animals that live in a coniferous forest survive the harsh winters by hibernating or migrating to a warmer climate for the winter.

These conifer leaves are adapted to conserve water.

Coniferous Forest

• Average Yearly Rainfall35 to 75 cm (14 to 29.5 in.)

• Average TemperaturesSummer: 14ºC (57ºF)Winter: –10ºC (14ºF)

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Temperate Deciduous ForestsHave you seen leaves change color in the fall? Have you

seen trees lose all of their leaves? If so, you have seen decidu-ous trees, such as oaks and maples. The word deciduous comesfrom a Latin word that means “to fall off.” Some deciduoustrees shed their leaves to save water during the winter or duringthe dry season. Other deciduous trees shed their leaves becausethe leaves are damaged by the cold. Leaves and other materialsdecompose on the forest floor and keep the soil fertile. Fertilesoils and the sunlight that reaches the forest floor allow forthe growth of small trees and shrubs.

Animals use different layers of the forest. For example, blackbears and rabbits live on the forest floor. Black bears are omni-vores that eat nuts, berries, and animals, such as rabbits. Rab-bits are herbivores that feed on plants. Squirrels feed on nuts.Squirrels move between the forest floor and the tree tops orforest canopy. Birds, such as woodpeckers, nest in the canopy.Woodpeckers that feed on only insects are carnivores. Figure 7shows some of the animals that live in this biome.

Why can more plants grow on the floors of decidu-ous forests than on the floors of coniferous forests? 6.5.e

Ferns and mosses arescattered across theforest fl oor. Floweringplants often bloom inearly spring, before thetrees grow new leaves.

In forests, plant growthhappens in layers. Theleafy tops of the treesreach high above theforest fl oor, where theleaves can get sunlight.

Woody shrubscatch the light thatfi lters through thetrees.

Figure 7 In a temperatedeciduous forest, mammals, birds,and reptiles thrive on the manyleaves, seeds, nuts, and insects.

Hibernation and WeightBlack bears enter a lighthibernation during the cold-est parts of the year. While inhibernation, black bears havelower body temperaturesand heart rates. They are alsoinactive and must live offtheir store of fat. A black bearweighs 92 kgs before hiber-nation. After hibernation, thebear is 30% lighter. Calcu-late the bear’s new weight.Record your work in yourScience Journal.

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Temperate Deciduous Forest

• Average Yearly Rainfall75 to 125 cm (29.5 to 49 in.)

• Average TemperaturesSummer: 28ºC (82ºF)Winter: 6ºC (43ºF)

Quick Lab

Tropical Rain ForestsTropical rain forest biomes are the most diverse places on

Earth. This means that tropical rain forest biomes have morekinds of plants and animals than any other biome does. Tropi-cal rain forests have warm temperatures and receive a highamount of rainfall, which supports a high diversity of plants.In turn, the plants support a high diversity of animals. Manyanimals live on the forest floor, but most animals live in thecanopy. Birds, such as the toucan shown in Figure 8, are omni-vores that eat fruits, reptiles, and other birds. Carnivores, suchas harpy eagles, eat other animals, such as howler monkeys.Howler monkeys are primarily herbivores that eat fruits, nuts,and leaves. However, howler monkeys may also eat the mag-gots found in fruits.

You may think that because of its diversity, the rain foresthas nutrient-rich soil. However, most of the nutrients in thetropical rain forest are in the plants. The soil is actually verynutrient poor and thin. Because the soil is so thin, many treesgrow above-ground roots for extra support.

Identify a consumer found in a tropical rain forest.

6.5.c, 6.5.d

Little light reaches theground. Low-growingplants in the rain forestdon’t need a lot of light.

Trees form a continuousgreen roof, or canopy,that may extend 60 mabove the forest fl oor.

Woody vines climbthe tree trunks toreach sunlight.

Figure 8 Tropical rain forestshave a greater diversity of organisms than any other biome does.

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Tropical Rain Forest

• Average Yearly Rainfallup to 400 cm (157.5 in.)

• Average TemperaturesDaytime: 34ºC (93ºF)Nighttime: 20ºC (68ºF)

What’s Your Biome?1. Measure and record

the temperature outsideyour classroom every dayfor a month.

2. Using the temperature dataand the descriptions ofthe biomes in this section,can you infer what kind ofbiome you live in? Explain.

3. What organisms live in yourbiome? Does this informa-tion help determine whichbiome you live in?

5 min/day for 30 days

6.5.e

Internet Resources

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

Summary

Review6.5.c, 6.5.d,6.5.e

• A biome is characterized by a unique plantcommunity. The plants, in turn, support uniqueanimal communities.

• Plants and animals in a biome are adapted tothe climate of the biome.

• Each organism in a biome can be categorizedinto the ecological role of a producer, a con-sumer, or a decomposer.

• Deserts are very dry and often very hot. Desertssupport plants and animals that use little water.

• Chaparral biomes are fairly dry biomes that sup-port dense patches of shrubs and trees. Animalsin the chaparral blend into their surroundings toavoid predators.

• Tundras are cold areas that have permafrostand receive very little rainfall. Tundras supportlow-growing plants and few animals.

• Grasslands are areas where grasses are the mainplants. Prairies have hot summers and coldwinters. Savannas have wet and dry seasons.

• Three forest biomes are temperate deciduousforests, coniferous forests, and tropical rainforests.

1 Use chaparral and tundra in separate sentences.

2 Write an original definition for grasslands anddesert.

3 Describing What are the major land biomesdiscussed in this section? What characteristicsdo all biomes share?

4 Identifying How are organisms categorized inland biomes? Give an example of each category.

5 Applying What is the ecological role of a leop-ard in the savanna and of a harpy eagle in therain forest?

INTERPRETING GRAPHICS Use the bar graphbelow to answer the next two questions.

LF05SEECOL01047AConiferous forest

Temperate grassland

Savanna

Desert

Tundra0

50

100

150

200

Rain

(cm

)

Biome

Rainfall on Biomes

6 Identifying Which biomes receive 50 cm ormore of rain each year?

7 Identifying Which biome receives the smallestamount of rain? Which receives the largestamount of rain?

8 Making Inferences While excavating an areain the desert, a scientist discovers the fossilsof very large trees and ferns. What might thescientist conclude about biomes in this area?

9 Analyzing Ideas Tundra receives very littlerainfall. Could a tundra accurately be called afrozen desert? Explain your answer.

0 Identifying Relationships You are lookingafter a friend’s plant. The plant needs a warmenvironment, lots of water, and very little sun-light. To which biome do you think the plantwould be best adapted? Explain your answer.

q Making Inferences You are studying an areain which the temperatures are usually moderate.However, extreme temperatures occur on oneor two days of the year. Which organisms wouldsurvive better in this area: organisms that areadapted to moderate temperatures or those thatcan tolerate extreme temperatures? Explain.

Topic: Forests; Wildfires in CaliforniaSciLinks code: HY70609; HY7C12