98 Chapter 4

1 FOCUSObjectives4.3.1 Explain what microclimates

are.4.3.2 Identify the characteristics of

major land biomes.

Vocabulary PreviewHave students recall the definition ofclimate they learned earlier. Writemicroclimate on the board, and drawa box around the prefix micro-. Ask avolunteer to find the meaning of theprefix in a dictionary. Micro- means“small”; thus the term microclimateliterally means “small climate”—a climate that exists over a small area.

Reading StrategyEncourage students to create a tablefor recording the characteristics ofeach biome. Suggest that theyinclude the following columns: Nameof Biome, Temperature, Precipitation,Soil Type, Dominant Plants, DominantAnimals, and a final column labeledOther Characteristics in which torecord any information that does notfit in the previous columns.

2 INSTRUCT

Biomes and Climate Use Community ResourcesTake students on a tour of the schoolgrounds or immediate neighborhoodto look for microclimates. Examplesmight include a south-facingembankment along a roadway; thesunny south side and shaded northside of a building; and the shaded,damp environment beneath a groupof trees. Encourage students to checkeach microclimate periodically andnote any changes—for example,spring flowers blooming along abuilding’s south side.

Ecologists group Earth’s diverse environments into biomes.

A is a complex of terrestrial communities that covers

a large area and is characterized by certain soil and climate

conditions and particular assemblages of plants and animals.

Can all kinds of organisms live in every biome? No. Species

vary in their adaptations to different conditions. An adaptation

is an inherited characteristic that increases an organism’s

ability to survive and reproduce.

The leaves of the saguaro cactus, for example, are reduced to

spines to minimize water loss, and its stems store water during

dry spells. Its shallow, wide-spreading roots absorb water

rapidly. Desert rodents, such as kangaroo rats, have adaptations

in their kidneys that help conserve water, and they extract

water from food. Many rain forest plants, such as certain

anthuriums, have long, thin leaves whose pointed tips help shed

excess water. Some rain forest animals, such as certain tree

frogs, spend their life in trees—their tadpoles grow in water

pockets in leaf bases of plants such as bromeliads.

These sorts of variations in plants and animals help different

species survive under different conditions in different biomes.

Plants and animals also exhibit variations in or

ability to survive and reproduce under conditions that differ

from their optimal conditions. Plants and animals of the Arizona

desert, for example, can tolerate temperatures that range from

blisteringly hot to below freezing. Some rain forest plants and

animals, by comparison, die quickly if the temperature drops

below freezing or rises above 34°C for long. Either too much or

too little of any environmental factor can make it difficult for an

organism to survive. A saguaro would rot and die in a rain forest

as surely as an anthurium or rain forest tree frog

would shrivel and die in the desert!

Biomes and ClimateBecause each species is adapted to certain conditions,

the climate of a region is an important factor in deter-

mining which organisms can survive there. Even

within a biome, precise conditions of temperature

and precipitation can vary over small distances. The

climate in a small area that differs from the climate

around it is called a For example,

certain streets in San Francisco are often blanketed

in fog while the sun shines brightly just a few blocks

away. Two main components of climate—temperature

and precipitation—can be summarized in a graph

called a climate diagram, as shown in Figure 4–10.

microclimate.

tolerance,

biome

4–3 Biomes

Key Concept• What are the unique

characteristics of the world’smajor biomes?

Vocabularybiome • tolerancemicroclimate • canopyunderstory • deciduousconiferous • humustaiga • permafrost

Reading Strategy: Using Visuals Before youread, preview Figure 4–11.Write down the names of thedifferent biomes. As you read,examine the photographs andlist the main characteristics ofeach biome.

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� Figure 4–10 Climate diagramsshow the average temperature andprecipitation at a given locationduring each month of the year. Inthis graph, and the others to follow,temperature is plotted as a red line.Precipitation is shown as verticalpurple bars. InterpretingGraphics What is the approximateaverage temperature and precipita-tion in New Orleans during the monthof July?

Section 4–3

SECTION RESOURCES

Print:

• Teaching Resources, Lesson Plan 4–3,Adapted Section Summary 4–3, AdaptedWorksheets 4–3, Section Summary 4–3,Worksheets 4–3, Section Review 4–3

• Reading and Study Workbook A, Section4–3

• Adapted Reading and Study Workbook B,Section 4–3

• Issues and Decision Making, Issues andDecisions 46

• Investigations in Forensics, Investigation 2

Technology:

• iText, Section 4–3• Transparencies Plus, Section 4–3

Tim

eSaver

0086_0112_bi_c07_te 3/7/06 9:53 PM Page 98

Build Science SkillsInterpreting Tables and GraphsTo ensure that students understandthe format of a climate diagram, askquestions about Figure 4–10, such asthe following: In which month doesNew Orleans have the least precipi-tation? (October) The mostprecipitation? (July) What generaltrend do you see in the averagemonthly temperatures throughoutthe year? (Temperatures are lowest inwinter, rise through the spring, arehighest in summer, and declinethrough the fall and early winter.)

The Major BiomesUse VisualsFigure 4–11 Direct students’ atten-tion to the map and ask: Whichbiomes are found in the UnitedStates, not including Alaska andHawaii? (Temperate grassland, desert,temperate woodland and shrubland,northwestern coniferous forest andtemperate forest) Which biomes arefound in Alaska? (Temperate forest,boreal forest, and tundra)

Build Science SkillsInferring Direct students to lookback at Figure 4–2 on page 88 andcompare it with Figure 4–11 on thispage. Ask: Why do you think scien-tists classify land biomes into 10categories when there are onlythree major climate zones onEarth? (Conditions vary somewhatwithin each climate zone, so severalbiomes may occur in some climatezones.)

Ecosystems and Communities 99

The Major BiomesEcologists recognize at least ten different biomes. The

world’s major biomes include tropical rain forest, tropi-

cal dry forest, tropical savanna, desert, temperate grass-

land, temperate woodland and shrubland, temperate

forest, northwestern coniferous forest, boreal forest, and

tundra. Each of these biomes is defined by a unique set of

abiotic factors—particularly climate—and a characteris-

tic assemblage of plants and animals. The distribution of

major biomes is shown in Figure 4–11, and some of their most

important characteristics are summarized over the next five

pages.

There is often ecological variation within a biome.

Sometimes, this variation is due to changes in microclimate

caused by differences in exposure or elevation above sea level.

Other times, variation may be related to geological factors such

as local soil conditions or the presence of rock outcroppings.

Note also that although boundaries between biomes on this map

appear to be sharp, there are often transitional areas in which

one biome’s plants and animals become less common, whereas

organisms of the adjacent biome become more common. These

variations in distribution often can be related to the ranges of

tolerances of plants and animals for different environmental

factors. As you look at Figure 4–11 and the following pages, see

if you can relate the characteristics and locations of biomes to

the patterns of global winds and ocean currents in Figure 4–3.

� Figure 4–11 This map showsthe locations of the world’s majorbiomes. Other parts of Earth’ssurface are classified as mountains or ice caps. Each biome has acharacteristic climate and com-munity of organisms. Thesecharacteristics are shown on thepages that follow.

30°N

60°N

30°S

60°S

0° Equator

0 3000 Kilometers

0 3000 Miles

1500

1500

Tropical rain forest

Tropical dry forest

Tropical savanna

Temperate grassland

Desert

Temperate woodlandand shrubland

Temperate forest

Northwesternconiferous forestBoreal forest(Taiga)

Tundra

Mountains andice caps

For: Earth’s Biomes activityVisit: PHSchool.comWeb Code: cbp-2043

Answer to . . . Figure 4–10 During the month ofJuly in New Orleans, the average tem-perature is 25°C and the averageprecipitation is 200 mm.

Comprehension: Prior KnowledgeBeginning Have the students locate theirnative country on the biome map in Figure4–11. Ask the students to use the key to identi-fy the biome of their native country and thebiome of their current home in the UnitedStates. Point out the names of the biomes inthe figure’s key, and read the names out loudto model correct pronunciation.

Intermediate Pair ESL students with Englishproficient students to prepare two lists. One listshould contain words or phrases that describethe biome, climate, and common organisms oftheir native country. The other list should con-tain words or phrases that describe the biome,climate, and common organisms of their cur-rent home in the United States. Have thestudents add examples to their list by usingpictures from newspapers and magazines.

SUPPORT FOR ENGLISH LANGUAGE LEARNERS

For: Earth’s Biomes activityVisit: PHSchool.comWeb Code: cbe-2043Students compare and contrastthe temperatures and rainfalllevels of the different biomes.

0086_0112_bi_c07_te 3/7/06 9:53 PM Page 99

100 Chapter 4

Build Science SkillsComparing and ContrastingGuide students through the wealthof information on pages 100–104 byhaving them focus on a single factorat a time across all the biomes. Forexample, first have students comparethe biomes’ temperature ranges andsequence them from lowest to high-est. (Tundra, boreal forest, temperateforest, northwestern coniferous forest,temperate grassland, temperate wood-land and shrubland, desert, tropicalsavanna, tropical rain forest, tropicaldry forest) Then, have students com-pare the biomes’ precipitation andsequence those amounts from lowestto highest. (Desert and tundra, borealforest, temperate woodland and shrub-land, temperate grassland, temperateforest, tropical savanna, tropical dryforest, northwestern coniferous forest,tropical rain forest) Next, have stu-dents compare the types of plantsthat are dominant in each biomeand, finally, the dominant animals.Discuss any biome features or organ-isms that are unfamiliar to students.Encourage students to share any per-sonal experiences they have had withdifferent land biomes.

Address MisconceptionsSome students may have the miscon-ception that all areas in tropicalregions receive a great amount ofrainfall all the time. Explain that it istrue that many areas have abundantrainfall because of frequent thunder-storms caused by local heating of theair. Currents in the atmosphere, how-ever, are extremely complex, and insome regions wind patterns result inmuch less precipitation than is foundin regions with tropical rain forests.The result is that the tropics containdry forests, savannas, and evendeserts.

Golden LionTamarin

Toucan

Tropical Rain ForestTropical rain forests are home to morespecies than all other biomes combined.The leafy tops of tall trees—extendingfrom 50 to 80 meters above the forestfloor—form a dense covering called a

In the shade below the canopy,a second layer of shorter trees and vinesforms an Organic matter thatfalls to the forest floor quickly decomposes,and the nutrients are recycled.

� Abiotic factors: hot and wetyear-round; thin, nutrient-poor soils

� Dominant plants: broad-leavedevergreen trees; ferns; large woodyvines and climbing plants; orchids andbromeliads

� Dominant wildlife: herbivoressuch as sloths, tapirs, and capybaras;predators such as jaguars; anteaters;monkeys; birds such as toucans,parrots, and parakeets; insects such asbutterflies, ants, and beetles; piranhasand other freshwater fishes; reptilessuch as caymans, boa constrictors, andanacondas

� Geographic distribution: partsof South and Central America, South-east Asia, parts of Africa, southernIndia, and northeastern Australia

understory.

canopy.

� Abiotic factors: generally warmyear-round; alternating wet and dryseasons; rich soils subject to erosion

� Dominant plants: tall, deciduoustrees that form a dense canopy duringthe wet season; drought-tolerantorchids and bromeliads; aloes andother succulents

� Dominant wildlife: tigers;monkeys; herbivores such as elephants,Indian rhinoceroses, hog deer; birdssuch as great pied hornbills, piedharriers, and spot-billed pelicans;insects such as termites; reptiles suchas snakes and monitor lizards

� Geographic distribution: partsof Africa, South and CentralAmerica, Mexico, India, Australia,and tropical islands

Tropical dry forests grow in places whererainfall is highly seasonal rather than year-round. During the dry season, nearly all thetrees drop their leaves to conserve water. Atree that sheds its leaves during a particularseason each year is called deciduous.

Tropical Dry Forest

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What’s soil got to do with it?Soil is a mixture of rock, mineral ions, andorganic matter. Each land biome tends to havea characteristic soil type. The top layer of soil intropical rain forest biomes is acidic, with light-colored humus. The subsoil consists of iron and

aluminum compounds mixed with clay. The soilin desert biomes is dry, brown to reddish brownwith variable accumulations of clay, calcium car-bonate, and soluble salts. A humus-mineralmixture exists in a thin layer of topsoil.

BACKGROUND

4–3 (continued)

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Build Science SkillsCommunicating Divide the classinto 10 groups, and assign a differentbiome to each group. Tell studentsthat each group is to serve as the“class experts” on its assigned biome.Let each group’s members divideresponsibilities among themselveshowever they wish. For example, onestudent could handle abiotic factors,another student the dominant plants,and a third student the dominantanimals. Encourage groups to doresearch to gain additional informa-tion about the biomes. Provide anopportunity for each group to pres-ent its biome to the class, shareadditional information they havegathered, and answer other students’questions.

Address MisconceptionsMost students—in fact, most peoplein general—think that all deserts arehot as well as dry. Emphasize that it isthe amount of precipitation, not thetemperature range, that distinguishesthe desert from other biomes.Encourage students to find out aboutcold deserts, including the high-altitude deserts of Mongolia andChina and the Great Basin in thewestern United States.

Ecosystems and Communities 101

All deserts are dry—in fact, a desert biomeis defined as having annual precipitationof less than 25 centimeters. Beyond that,deserts vary greatly, depending onelevation and latitude. Many undergoextreme temperature changes during thecourse of a day, alternating between hotand cold. The organisms in this biomecan tolerate the extreme conditions.

� Abiotic factors: low precipitation;variable temperatures; soils rich inminerals but poor in organic material

� Dominant plants: cacti and othersucculents; creosote bush and otherplants with short growth cycles

� Dominant wildlife: predators suchas mountain lions, gray foxes, andbobcats; herbivores such as mule deer,pronghorn antelopes, desert bighornsheep, and kangaroo rats; bats; birdssuch as owls, hawks, and roadrunners;insects such as ants, beetles, butterflies,flies, and wasps; reptiles such astortoises, rattlesnakes, and lizards

� Geographic distribution: Africa,Asia, the Middle East, United States,Mexico, South America, and Australia

Receiving more seasonal rainfall thandeserts but less than tropical dry forests,tropical savannas, or grasslands, arecharacterized by a cover of grasses.Savannas are spotted with isolated treesand small groves of trees and shrubs.Compact soils, fairly frequent fires, andthe action of large animals such asrhinoceroses prevent some savanna areasfrom turning into dry forest.

� Abiotic factors: warm tempera-tures; seasonal rainfall; compact soil;frequent fires set by lightning

� Dominant plants: tall, perennialgrasses; sometimes drought-tolerantand fire-resistant trees or shrubs

� Dominant wildlife: predatorssuch as lions, leopards, cheetahs,hyenas, and jackals; aardvarks;herbivores such as elephants, giraffes,antelopes, and zebras; baboons; birdssuch as eagles, ostriches, weaverbirds, and storks; insects such astermites

� Geographic distribution: largeparts of eastern Africa, southern Brazil,and northern Australia

Desert

Tropical Savanna

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Convergent evolutionPlants and animals that appear to be quite similaroften are found in similar environments but inwidely separated parts of the world. For example,a member of the cactus family that grows indeserts of the southwestern United States is simi-lar in appearance to a member of the spurge

family that grows in the deserts of southwesternAfrica. It would seem that these plants haveevolved from a common ancestor, but this is notthe case. The two species evolved from plantsthat are not related. This phenomenon of similaryet unrelated species occurring in different partsof the world is known as convergent evolution.

FACTS AND FIGURES

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102 Chapter 4

Build Science SkillsComparing and ContrastingHave students refer back to thebiome map in Figure 4–11 on page99. Ask: Which biome makes up thelargest portion of the continentalUnited States? (Temperate grassland)Then, direct students to review theclimate diagrams and text descrip-tions of the temperate grasslandbiome on this page and the tropicalsavanna biome on page 101. Ask:What is the major similaritybetween these two biomes? (Thedominant plants are grasses.) Whatare the major differences in thetwo biomes’ climate? (The savannagets more rainfall and has a greaterrange between the highest and lowestamounts. Savanna temperatures arehigher but less variable than temperategrassland temperatures.)

Make ConnectionsEarth Science Ask students: What isthe difference in the soils of tem-perate grassland and temperatewoodland and shrubland?(Temperate grassland has fertile soils,whereas temperate woodland andshrubland has nutrient-poor soils.)Have students compare the climatediagrams for the two biomes. Explainthat soil is a combination of mineraland organic matter, and climate isperhaps the most influential factor insoil formation. Temperature and pre-cipitation determine the kind ofweathering, which determines thecharacteristics of the minerals thatmake up the soil. In addition, climatealso is the main factor in the growthof vegetation and the abundance ofmicroorganisms in the soil, both ofwhich affect the soil’s characteristics.Point out that just as the soils helpdetermine the kind of vegetationfound in a biome, the vegetation inturn contributes to how rich the soilsare, since it’s primarily the vegetationof an area that contributes the organ-ic material in a rich soil.

Temperate Grassland

Temperate Woodlandand Shrubland

Characterized by a rich mix of grasses andunderlaid by some of the world’s mostfertile soils, temperate grasslands—such asplains and prairies—once covered vastareas of the midwestern and central UnitedStates. Since the development of the steelplow, however, most have been convertedto agricultural fields. Periodic fires andheavy grazing by large herbivores maintainthe characteristic plant community.

� Abiotic factors: warm to hot sum-mers; cold winters; moderate, seasonalprecipitation; fertile soils; occasional fires

� Dominant plants: lush, perennialgrasses and herbs; most are resistantto drought, fire, and cold

� Dominant wildlife: predators suchas coyotes and badgers—historicallyincluded wolves and grizzly bears;herbivores such as mule deer, pronghornantelopes, rabbits, prairie dogs, andintroduced cattle—historically includedbison; birds such as hawks, owls,bobwhites, prairie chickens, mountainplovers; reptiles such as snakes; insectssuch as ants and grasshoppers

� Geographic distribution:central Asia, North America, Australia,central Europe, and upland plateaus ofSouth America

This biome is characterized by a semiaridclimate and a mix of shrub communitiesand open woodlands. In the open wood-lands, large areas of grasses and wildflowerssuch as poppies are interspersed with oaktrees. Communities that are dominated byshrubs are also known as chaparral. Thegrowth of dense, low plants that containflammable oils makes fires a constant threat.

� Abiotic factors: hot, dry sum-mers; cool, moist winters; thin,nutrient-poor soils; periodic fires

� Dominant plants: woodyevergreen shrubs with small, leatheryleaves; fragrant, oily herbs that growduring winter and die in summer

� Dominant wildlife: predatorssuch as coyotes, foxes, bobcats, andmountain lions; herbivores such asblacktailed deer, rabbits, and squirrels;birds such as hawks, California quails,warblers and other songbirds; reptilessuch as lizards and snakes; butterflies

� Geographic distribution:western coasts of North and SouthAmerica, areas around the Mediter-ranean Sea, South Africa, and Australia

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More on soilThe topsoil of temperate grassland biomes tendsto be dark, alkaline, and rich in humus. This top-soil layer extends downward for more than ameter. Because topsoil formed on grasslands is

often very fertile, most of the world’s crops aregrown on grassland soils. The subsoil consists ofclay and calcium compounds. Soil in the borealforest biomes is often quite acidic.

BACKGROUND

4–3 (continued)

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Build Science SkillsApplying Concepts Point out thatthe temperate forest biome in north-eastern regions of North America andAsia is noted for its striking colored fallfoliage. If students do not live in anarea that experiences this seasonalchange, urge them to collect photo-graphs of fall foliage. Also suggest thatthey obtain booklets and other touristguides that describe the best timesand locations for foliage viewing atdifferent latitudes within the biome.

Build Science SkillsClassifying Collect photographs ofvarious types of animals that arecharacteristic of each major landbiome. Number the photographs,and display them in random order.Working individually or in pairs, stu-dents should try to determine thebiome(s) in which each animal mightlive. In a follow-up class discussion,let students compare their choicesand explain their reasoning.

Ecosystems and Communities 103

Mild, moist air from the Pacific Oceanprovides abundant rainfall to this biome.The forest is made up of a variety ofconifers, ranging from giant redwoodsalong the coast of northern California tospruce, fir, and hemlock farther north.Moss often covers tree trunks and theforest floor. Flowering trees and shrubssuch as dogwood and rhododendron arealso abundant. Because of its lush vegeta-tion, the northwestern coniferous forest issometimes called a “temperate rain forest.”

� Abiotic factors: mild tempera-tures; abundant precipitation duringfall, winter, and spring; relatively cool,dry summer; rocky, acidic soils

� Dominant plants: Douglas fir, Sitkaspruce, western hemlock, redwood

� Dominant wildlife: bears; largeherbivores such as elk and deer;beavers; predators such as owls, bob-cats, and members of the weasel family

� Geographic distribution:Pacific coast of northwestern UnitedStates and Canada, from northernCalifornia to Alaska

Temperate forests contain a mixture ofdeciduous and coniferous (koh-NIF-ur-us)trees. trees, or conifers,produce seed-bearing cones, and mosthave leaves shaped like needles. Theseforests have cold winters that halt plantgrowth for several months. In autumn, the deciduous trees shed their leaves. Inthe spring, small plants burst out of theground and flower. Soils of temperateforests are often rich in (HYOO-mus), a material formed from decayingleaves and other organic matter thatmakes soil fertile.

� Abiotic factors: cold to moderatewinters; warm summers; year-roundprecipitation; fertile soils

� Dominant plants: broadleafdeciduous trees; some conifers;flowering shrubs; herbs; a ground layer of mosses and ferns

� Dominant wildlife: Deer; blackbears; bobcats; nut and acorn feederssuch as squirrels; omnivores such asraccoons and skunks; numeroussongbirds; turkeys

� Geographic distribution: easternUnited States; southeastern Canada;most of Europe; and parts of Japan,China, and Australia

humus

Coniferous

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Temperate Forest

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Layers of plant growthIn a temperate forest, there may be up to fivelayers of plant growth. The tallest trees make upthe canopy layer; often this layer consists of onlyone or two dominant species. Under the canopyis a layer of shorter trees called the understory.

Below the understory is a shrub layer made up ofshort, branching, woody plants. An herb layerconsisting of grasses, ferns, and annual wildflow-ers grows close to the ground. Finally, there is theground layer, which consists of mosses, fungi,and leaf litter.

FACTS AND FIGURES

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104 Chapter 4

Build Science SkillsDrawing Conclusions Focus stu-dents’ attention on the climatediagram for the tundra biome. Ask:In terms of precipitation through-out the year, which other biomedoes the tundra most resemble?(The desert biome) Have students lookback at the biome map on page 99.Ask: Why does the tundra biomehave the lowest temperatures of allthe biomes? (The tundra is the far-thest north of all biomes, so it receivesthe sun’s rays at the lowest angles andfor the shortest periods of time.)

Other Land AreasMake ConnectionsEarth Science Display a large worldmap that shows Earth’s major moun-tain ranges. Have students locate thecolor-coded mountain areas on thebiome map in Figure 4–11, page 99,and then find those areas on thelarge map and list the names of themountain ranges. Separate groupscould investigate each range’s char-acteristics—the heights of its tallestpeaks, the temperature ranges anddominant organisms at various eleva-tions, and other data. Encouragestudents to also search out interest-ing facts about the ranges, such asthe 1998 discovery of mummifiedchildren on high Andean peaks ortales of the elusive Yeti (“abominablesnowman”) high in the Himalayas.Let groups share their findings in oralreports, illustrated displays, or three-dimensional models.

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Tundra

The tundra is characterized by a layer of permanently frozen subsoil.During the short, cool summer, the groundthaws to a depth of a few centimeters andbecomes soggy and wet. In winter, thetopsoil freezes again. This cycle of thawingand freezing, which rips and crushes plantroots, is one reason that tundra plants aresmall and stunted. Cold temperatures,high winds, the short growing season, andhumus-poor soils also limit plant height.

� Abiotic factors: strong winds; lowprecipitation; short and soggysummers; long, cold, and dark winters;poorly developed soils; permafrost

� Dominant plants: ground-huggingplants such as mosses, lichens, sedges,and short grasses

� Dominant wildlife: a few residentbirds and mammals that can with-stand the harsh conditions; migratorywaterfowl, shore birds, musk ox, Arcticfoxes, and caribou; lemmings andother small rodents

� Geographic distribution:northern North America, Asia, andEurope

permafrost,

SnowyOwl

Caribou

Lynx

Moose

Boreal Forest

Along the northern edge of the temperatezone are dense evergreen forests ofconiferous trees. These biomes are calledboreal forests, or (TY-guh). Wintersare bitterly cold, but summers are mildand long enough to allow the ground tothaw. The word boreal comes from theGreek word for “north,” reflecting thefact that boreal forests occur mostly in theNorthern Hemisphere.

� Abiotic factors: long, coldwinters; short, mild summers; moder-ate precipitation; high humidity;acidic, nutrient-poor soils

� Dominant plants: needleleafconiferous trees such as spruce and fir;some broadleaf deciduous trees; small,berry-bearing shrubs

� Dominant wildlife: predatorssuch as lynxes and timber wolves andmembers of the weasel family; smallherbivorous mammals; moose andother large herbivores; beavers;songbirds and migratory birds

� Geographic distribution: NorthAmerica, Asia, and northern Europe

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Oases in the tundraAs an example of the tundra’s extreme dryness: Inthe Arctic regions north of mainland Canada, lessthan 15 cm of precipitation falls annually—aboutthe same amount as falls in the desert regions ofArizona. Such dryness, coupled with intense cold,makes the tundra a barren place. Yet, like the

oases in deserts, there are areas where livingthings can survive and even thrive. Some of theseareas are sheltered valleys that are protected frombitterly cold winds. Other areas are meadowswith an abundant water supply that can supportlarge numbers of animals.

FACTS AND FIGURES

4–3 (continued)

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3 ASSESSEvaluate UnderstandingBriefly describe characteristics of vari-ous biomes, and call on students atrandom to identify each one. Forexample, if you say, “High tempera-tures that do not vary muchthroughout the year,” studentsshould identify the biome as a tropi-cal rain forest or a tropical savanna.Base your descriptions on the infor-mation presented on pages 100–104of the student text.

ReteachMake overhead transparencies of theclimate diagrams for each of the landbiomes. Project the diagrams in anyorder. For each diagram, call on onestudent to summarize the diagram’sinformation about temperature andprecipitation (for example, “High tem-peratures and heavy rainfallyear-round”), and call on a secondstudent to identify the biome.

Ecosystems and Communities 105

Other Land Areas Some areas of land on Earth do not fall neatly

into the major biome categories described on the

previous pages. These areas include mountain

ranges and polar ice caps.

Mountain Ranges Mountain ranges can be

found on all continents. On mountains like the

one in Figure 4–12, the abiotic and biotic condi-

tions vary with elevation. As you move up from

base to summit, temperatures become colder and

precipitation increases. Therefore, the types of

plants and animals also change. If you were to

climb the Rocky Mountains in Colorado, for

example, you would begin in a grassland. Then,

you would pass through an open woodland of

pines. Next, you would hike through a forest of

spruce and other conifers. Near the summit, you

would reach open areas of wildflowers and

stunted vegetation resembling tundra. In the

Canadian Rockies, ice fields occur at the peaks

of some ranges.

Polar Ice Caps The icy polar regions that

border the tundra are cold year-round. Outside of

the ice and snow, plants and algae are few but do

include mosses and lichens. In the north polar

region, the Arctic Ocean is covered with sea ice,

and a thick ice cap covers most of Greenland.

Polar bears, seals, insects, and mites are the

dominant animals. In the south polar region, the

continent of Antarctica is covered by a layer of ice

that is nearly 5 kilometers thick in some places.

There, the dominant wildlife includes penguins

and marine mammals.

� Figure 4–12 Washington’s Mount Rainier towersabove the tree line. Applying Concepts Based onwhat you have seen in the previous pages, which biomelies at the base of this mountain?

NSTA

For: Links on biomesVisit: www.SciLinks.orgWeb Code: cbn-2043

1. Key Concept List themajor biomes, and give onecharacteristic feature of each.

2. How are biomes classified?

3. What are the two types of tropicalforest? How do they differ?

4. How might a mountain rangeaffect the types of plants andanimals found in an area?

5. Critical Thinking InferringWhat characteristics would youexpect tundra animals to have?

6. Critical Thinking Comparingand Contrasting Choose twovery different biomes. From eachbiome, select a plant and ananimal that are dominant.Compare how these plants’adaptations are suited to theirbiomes. Compare how theseanimals’ adaptations are suited totheir biomes.

4–3 Section AssessmentInterdependence inNature Choose one of thebiomes discussed in this sec-tion. Then, depict the biomein a piece of artwork. Includethe biome’s characteristicplant and animal life in yourart. Add labels to identify theorganisms, and write a captiondescribing the content of theartwork.

Answer to . . .

Figure 4–12 Boreal forest

NSTA

Download a worksheet on biomes for students to com-plete, and find additional teachersupport from NSTA SciLinks.

If your class subscribes to theiText, use it to review the KeyConcepts in Section 4–3.

4–3 Section Assessment1. Students should list the major biomes along

with one characteristic of each.2. By their climate, which is determined by

precipitation and temperature, and by thecommunity of organisms that live there

3. Tropical rain forests have higher tempera-tures and more rainfall annually than dotropical dry forests.

4. Animals and plants found in mountainranges must be adapted to the generally

cooler, wetter conditions that are foundthere.

5. Sample answer: Tundra animals need to bewell insulated with thick coats of fur/hair orlayers of feathers.

6. Answers may vary. Students might select anyplants and animals mentioned in the profilesof the 10 biomes. In their comparisons, theyshould discuss specific adaptations of theorganisms.

This activity can be completedindividually or in small groups.Provide students with a variety ofmaterials to choose from, includ-ing basic art supplies, modelingclay, pasta shapes, pipe cleaners,fabric, and construction paper.You might also encourage stu-dents to bring materials fromhome, or you might coordinatethis activity with an art class atyour school. Encourage studentsto be creative but accurate indepicting the biomes.

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