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66 COMMUNITIES AND BIOMES

Communities and Biomes

What You’ll Learn■ You will identify factors that

limit the existence of speciesto certain areas.

■ You will describe how andwhy different communitiesform.

■ You will compare and con-trast biomes of planet Earth.

Why It’s ImportantLife is found in communitiesmade of different species. Tounderstand life on Earth, it isimportant to understand theinteractions and growth ofcommunities.

Make a list of new vocabularywords from the chapter. Readthe list, looking for words thatare familiar. Then go back tothe text to see how the wordsare used.

To find out more about com-munities and biomes, visit theGlencoe Science Web site.science.glencoe.com

READING BIOLOGYREADING BIOLOGY

3ChapterChapter

This forest is a communityof life. The inset photoshows the same area 50years ago. Plants and ani-mals return to an area instages. Because communi-ties depend on the climateand other abiotic factors,different regions of theworld have different biomes.

BIOLOGY

http://science.glencoe.com

Section

Living in theCommunity

Look closely at a green lawn. Atfirst glance, you might think there isonly one species of plant, a grass.However, with closer examinationyou will find other organisms, such asinsects, worms, weeds, and otherspecies of grasses. Recall that com-munities are interacting populationsof different species. How do speciesinteract in your lawn?

Have you ever wondered whyplants, animals, and other organismslive where they do? Why do lichensgrow on bare rock but not on richsoil? Why do polar bears, such as

shown in Figure 3.1, live onlyin cold, snowy polar regions?How do catfish manage to livein waters that are too warm fortrout to survive? Abiotic andbiotic factors interact andresult in conditions that aresuitable for life for some organ-isms and unsuitable for otherorganisms.

3.1 COMMUNITIES 67

Most organisms are adapted tomaintain homeostasis in theirnative environments. A cactus

can live in the desert, but it still needswater to survive. Its cells and tissues canabsorb and store large amounts of water.Chipmunks can survive cold winters inthe forest by going into hibernation.

But what if the ecosystem changes?What happens when a flashflood sends torrents ofwater through thedesert? What hap-pens when a forestfire destroys hun-dreds of acres oftrees?

SECTION PREVIEW

ObjectivesExplain how limitingfactors and ranges oftolerance affect distri-bution of organisms.Sequence the stages ofecological succession.

Vocabularylimiting factorsuccessionprimary successionclimax community secondary succession

3.1 Communities

Mount St. Helensbefore the eruptionin 1980 (inset) andMount St. Helensafter the eruption(above).

Figure 3.1 Polar bears live near the north pole.Their white fur makes them hard to distinguish from the surroundingice and snow, enabling them tostalk the seals and walruses thatserve as their primary food.

Limiting factorsEnvironmental factors that affect

an organism’s ability to survive in itsenvironment, such as food availabil-ity, predators, and temperature, arelimiting factors. A limiting factor isany biotic or abiotic factor thatrestricts the existence, numbers,reproduction, or distribution oforganisms. The timberline in Figure3.2 illustrates how limiting factorsaffect the plant life of an ecosystem.At high elevations, temperatures aretoo low, winds too strong, and thesoil too thin to support the growth oflarge trees. Vegetation is limited tosmall, shallow-rooted plants, mosses,ferns, and lichens.

Factors that limit one populationin a community may also have anindirect effect on another population.For example, a lack of water couldlimit the growth of grass in a grass-land, reducing the number of seedsproduced. The population of micedependent on those seeds for food

will also be reduced. What abouthawks that feed on mice? Their num-bers may be reduced, too, as a resultof a decrease in their food supply.

Ranges of toleranceFarmers will tell you that corn

plants need two to three months ofsunny weather and a steady supply ofwater to produce a good yield. Corngrown in the shade or during a longdry period may survive, but probablywon’t produce much of a crop. Theability of an organism to withstandfluctuations in biotic and abioticenvironmental factors is known astolerance. Figure 3.3 illustrates howthe size of a population variesaccording to its tolerance for envi-ronmental change.

Some species can tolerate condi-tions that another species cannot. Forexample, catfish can live in warmwater with low amounts of dissolvedoxygen, which other fish species,such as bass or trout, could not toler-ate. The bass or trout would have toswim to cooler water with more dis-solved oxygen to avoid exceedingtheir range of tolerance.

Succession: Changes over Time

If grass were no longer cut on alawn, what would it look like in oneyear, five years, and 20 years?Ecologists can accurately predict thechanges that take place. The grassgets taller; weeds start to grow. Thearea resembles a meadow. Later,bushes grow, trees appear and differ-ent animals enter the area to live. The bushes and trees change theenvironment; less light reaches theground. The grass slowly disappears.Thirty years later, the area is a forest.Ecologists refer to the orderly, nat-ural changes and species replacements


Figure 3.2 The timberline is theupper limit of treegrowth on thismountainside.

Looking at LichensLichens have thereputation forbeing a pioneerspecies when itcomes to succes-sion. They ofteninhabit rocky areasand start the processof soil formation. Howis it possible for lichens togrow on a rock?

Procedure! Examine the lichen samples

provided by your teacher. Notetheir color, shape, and texture.

@ Use a microscope to examine aprepared slide of a stained section ofa lichen. Use low-power magnification and then change to high power as needed.

# Observe the dark bodies that are cells containing chloro-plasts. Notice that lichens are composed of an alga and afungus. Diagram what you see.

Analysis1. Describe the general appearance of a whole lichen and of

the lichen under a microscope.2. How does a lichen illustrate mutualism?3. Explain how mutualism explains why lichens are able to

survive on rocks.

MiniLab 3-1MiniLab 3-1that take place in the communities of an ecosystem as succession (sukSESH un).

Succession occurs in stages; differ-ent species at different stages createconditions that are suitable for someorganisms and unsuitable for others.Succession is often difficult toobserve. It can take decades, or evencenturies, for one type of communityto completely succeed another.Observe the effects of succession inthe BioLab at the end of this chapter.

Primary successionLava flowing from the mouth of a

volcano is so hot it destroys every-thing in its path, but when it cools itforms new land. An avalancheexposes rock and creates ledges andgullies even as it buries the areasbelow. The colonization of new siteslike these by communities of organ-isms is called primary succession.The first species in an area are calledpioneer species. An example of a pio-neer species is a lichen. Examinelichens more closely in the MiniLabon this page.

After some time, primary succes-sion slows down, and, after manychanges in species composition, the

3.1 COMMUNITIES 69

Limits of Tolerance

Popu

latio

n

High

Organismsinfrequent

Organismsinfrequent

Organismsabsent

Zone ofphysiological

stress

Zone ofphysiological

stress

Zone ofintolerance

Zone ofintolerance

Organismsabsent

LowRange of tolerance

Greatest numberof organisms

Optimum range

Figure 3.3 The limits of an organ-ism’s tolerance arereached when theorganism receives toomuch or too little ofsome environmentalfactor. Organismsbecome fewer as con-ditions move towardeither extreme of therange of tolerance.

A lichen,note thealga andfungus inthe close-up below.

Magnification: 700�

Observing

How do you distinguish between primary and secondarysuccession? Succession is the series of gradual changes thatoccur in an ecosystem. Ecologists recognize two types of suc-cession—primary and secondary. The events occurring duringthese two processes can be represented by a graph.

AnalysisExamine the graph. The two lines marked A and B repre-

sent primary and secondary succession. Note, however, thatneither line is identified for you.

Thinking Critically1. Which line best represents primary succession? Explain.2. Which line best represents secondary succession? Explain.3. Which label, C or D, might best represent a climax com-

munity? Pioneer organisms? Explain.4. What does the sudden drop of line C represent?

Problem-Solving Lab 3-1Problem-Solving Lab 3-1 Interpreting ScientificIllustrations

community becomes fairly stable. Astable, mature community that under-goes little or no change in species iscalled a climax community. Primarysuccession of bare rock into a climaxcommunity is illustrated in Figure 3.4.

As pioneer organisms die, theirdecaying bodies cling to the bits ofrock accumulating in cracks andcrevices, initiating the first patches ofsoil. The presence of soil makes itpossible for weedy plants, small ferns,and insects to become established.The soil builds up, and seeds borneby the wind blow into these largerpatches of soil and begin to grow.

Over time, as the community oforganisms changes and develops,additional habitats emerge, newspecies move in, and old species dis-appear. Eventually, the area becomesa forest of vines, trees, and shrubsinhabited by birds and other forest-dwelling animals.

Secondary successionWhat happens when a natural dis-

aster such as a forest fire or hurricanedestroys a community? What hap-pens when farmers abandon a field orwhen a building is demolished in a

70

Figure 3.4 The first organisms tocolonize a new, rockysite are hardy pioneerspecies such as lichens.Larger plants eventuallyreplace the pioneerspecies.

BB

CC

DD

AA

BBSpec

ies d

iver

sity

Time

Primary and Secondary Succession

Beeches and maples

Pines

Ferns, shrubs,and grasses

Mosses

Lichens

3.1 COMMUNITIES 71

Figure 3.5 After YellowstoneNational Park’s forestfire of 1988, the pio-neer species werewildflowers.

Section AssessmentSection AssessmentUnderstanding Main Ideas1. Give an example of a limiting factor for a pine

tree.2. Some species of fishes can survive in both fresh-

and salt water. What does this say about theirrange of tolerance?

3. Give an example of secondary succession. Includeplants and animals in your example.

4. Give an abiotic factor, and explain how it couldbe a limiting factor for a coyote population.

Thinking Critically5. Explain how the growth of one population

can bring about the disappearance of anotherpopulation during succession.

6. Making and Using Graphs Using the following data, graph the limits of tolerance for temperature for carp. The first number in each pair is temperature in degrees Celsius;the second number is the number of carp surviving at that temperature: 0, 0; 10, 5; 20, 25; 30, 34; 40, 27; 50, 2; 60, 0. For more help, refer to Organizing Information in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

city and nothing is built on the site?Secondary succession refers to thesequence of community changes thattakes place after a community is dis-rupted by natural disasters or humanactions.

During secondary succession, as inprimary succession, the community oforganisms inhabiting an area gradu-ally changes. Secondary succession,however, occurs in areas that previ-ously contained life, and on land thatcontains soil. Therefore, the pioneerspecies involved in secondary succes-sion are different from those in pri-mary succession, but the same climaxcommunity will be reached in areaswith a similar climate. Because soilalready exists, secondary successionusually takes less time than primarysuccession to reach a climax commu-nity. Learn more about the differ-ences between primary and secondarysuccession in the Problem-Solving Lab.

In 1988, a forest fire burned out ofcontrol in Yellowstone NationalPark. Thousands of acres of trees,shrubs, and grasses were burned. Asyou can see in Figure 3.5, the firehas given biologists an excellentopportunity to study secondary suc-cession in a community. They have

been able to observe and comparesecondary succession in areas thatsuffered damage of different levels ofseverity. Annual wildflowers were thefirst plants to grow back. Previously,the shade of the trees inhibited wild-flower growth. Within three years,perennial wildflowers, grasses, ferns,and pine seedlings began to replacethe annuals. Once the pine seedlingsgrow above the shade cast by thegrasses and perennials, the trees willgrow more quickly, and eventually amature forest of lodge pole pines, thesame community that was destroyed,will once again develop.

Section


Aquatic Biomes: Life in the Water

Ecosystems that have similar kindsof climax communities can begrouped into a broader category oforganization called a biome. Abiome is a large group of ecosystemsthat share the same type of climaxcommunity. Biomes located on landare called terrestrial biomes; thoselocated in oceans, lakes, streams,ponds, or other bodies of water arecalled aquatic biomes.

As a human who lives on land, youmay tend to think of Earth as a pri-marily terrestrial planet. But onelook at a globe, a world map, or aphotograph of Earth taken fromspace tells you there is an aquaticworld, too; approximately 75 percent

of Earth’s surface is covered withwater. Most of that water is salty.Oceans, seas, and even some inlandlakes contain salt water. Freshwater isconfined to rivers, streams, ponds,and most lakes. Saltwater and fresh-water environments have similarities,but they also have important differ-ences. As a result, aquatic biomes areseparated into marine biomes andfreshwater biomes.

Marine biomesIf you’ve watched TV programs

about ocean life, you may have got-ten the impression that the oceansare mostly full of great white sharks,whales, and other large animals.However, different parts of the oceandiffer in physical factors and in theorganisms found there. The oceans

Climate, a combination of temperature,sunlight, prevailing winds, and precipitation, is an important factor

in determining which climax community willdevelop at any spot on Earth. Soil type is alsoimportant. Many regions of the world sharesimilar soil and climate characteristics and, as a result, also share similar types of climax communities. Although the species of organisms living in each desert ecosystem may vary, all are adapted for life in an environment with dry weather and poor soil.

SECTION PREVIEW

ObjectivesCompare and contrastthe photic and aphoticzones of marine biomes.Identify the major limiting factors affecting distribution of terrestrial biomes.Distinguish amongbiomes.

Vocabularybiome photic zoneaphotic zoneestuary intertidal zoneplankton tundra permafrost taigadesert grasslandtemperate foresttropical rain forest

3.2 Biomes

Cardon cactus(above) and kangaroo rat (inset)

contain the largest amount of bio-mass, or living material, of any biomeon Earth, but most of this biomass ismade up of extremely small, oftenmicroscopic, organisms that humansusually don’t see.

One of the ways ecologists studymarine biomes is to separate theminto shallow, sunlit zones and deeper,unlighted zones. The portion of themarine biome that is shallow enoughfor sunlight to penetrate is called thephotic zone. Shallow marine envi-ronments exist along the coastlines ofall landmasses on Earth. Thesecoastal ecosystems include rockyshores, sandy beaches, and mudflats,and all are part of the photic zone.Deeper water that never receivessunlight makes up the aphotic zone.The aphotic zone includes the deep-est, least explored areas of the ocean.

A mixing of watersIf you were to follow the course of

any river, you would eventually reacha sea or ocean. Wherever rivers joinoceans, freshwater mixes with salt

water. In many such places, an estu-ary is formed. An estuary (ES chuhwer ee) is a coastal body of water,partially surrounded by land, inwhich freshwater and saltwater mix.It may extend many miles inland.The salinity in an estuary rangesbetween that of seawater and that of freshwater, and depends on howmuch freshwater the river brings intothe estuary. Salinity in the estuaryalso changes with the tide. Because of these changes in salinity, a widerange of organisms can live in estu-aries. Estuaries may contain saltmarsh ecosystems, which are domi-nated by salt-tolerant grasses, asillustrated in Figure 3.6. Theseplants often grow so thick that theirstems and roots form a tangled matthat traps food material and providesadditional habitat for small organ-isms. These small organisms attract awide range of predators, includingcranes and other birds. The decay of dead organisms proceeds quickly,recycling nutrients through the foodweb.

3.2 BIOMES 73

Figure 3.6 Because estuariesprovide an abundantsupply of food andshelter, many fishes,clams, and othercommercially impor-tant organisms livethere while young.Many of them venture out of theestuary and into the ocean once theyreach adulthood.

OriginWORDWORD

photicFrom the Greekword phos, meaning“light.” The marinephotic zone receiveslight from the sun.

aphoticFrom the Greekwords a, meaning“without,” and phos,meaning “light.”The aphotic zonedoesn’t receive light.

What information can be learned from studying a graph?Tide pools are depressions along rocky coasts that are covered by ocean waters during high tide. However, when oceans retreat during low tide, these tide pools are stranded and become temporarily cut off from ocean waters.

AnalysisThe graph shows results from tests of water samples

taken in a tide pool and in the surrounding ocean. A scientistmeasured oxygen levels in ppm (parts per million). Both theocean and tide pool have the same producer present, a greenalgae called Cladophora.

Thinking Critically1. What can you tell about how the experiment was done

using only the x- and y-axis information?2. What can you tell about how the experiment was done

from studying the graph?3. What can’t you tell about the experiment from the data

provided?4. What specific information was learned as a result of the

experiment?

Problem-Solving Lab 3-2Problem-Solving Lab 3-2 AnalyzingInformation

The effects of the tidesTwice a day, the gravitational pull

of the sun and moon causes the riseand fall of ocean tides. The portion ofthe shoreline that lies between thehigh and low tide lines is called theintertidal zone. The size of this zonedepends upon the slope of the landand the height of the tide. Intertidalecosystems have high levels of sun-light, nutrients, and oxygen, but pro-ductivity may be limited by wavescrashing against the shore. Intertidalzones differ in rockiness and waveaction. Figure 3.7 shows examples ofdifferent types of intertidal zones. Ifthe shore is rocky, waves constantlythreaten to wash organisms intodeeper water. Snails, sea stars, andother intertidal animals of the rockyshore have body parts that act as suc-tion cups for holding onto the wave-beaten rocks. Other animals, such asmussels and barnacles, secrete astrong glue that helps them remainanchored. If the shore is sandy, waveaction keeps the bottom in constantmotion. Most of the clams, worms,snails, crabs, and other organisms thatlive along sandy shores survive byburrowing into the sand.


Figure 3.7 Waves crashing against a rocky shore area constant threat to life in the intertidalzone (a). Wave action churns the bottomof a sandy shore (b).

Diss

olve

d ox

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(ppm

)

Noon

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6.0

5.5

5.0

4.5

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6:00 pm

6:00 am

Midnight

Tide pool

Ocean

Oxygen Levels

a

b

Looking at Marine Plankton Planktonis the term used to define the micro-scopic life forms present in anaquatic environment. Plankton con-sists mainly of protists and animallarvae.

Procedure! Use a medicine dropper to obtain

a small sample of marine plankton. @ Prepare a wet mount of the material.

CAUTION: Handle microscope slidesand coverslips carefully.

# Observe under low-power magnification of the microscope. $ Look for a variety of organisms and diagram several

different types.

Analysis1. Describe the appearance of specific planktonic organisms.

Draw what you see.2. Are both autotrophs and heterotrophs present? How can

you distinguish them?3. Why are plankton important in food chains?

MiniLab 3-2MiniLab 3-2

Tide pools, pools of water left whenthe water recedes at low tide, canlandlock the organisms that live in theintertidal zone until the next hightide. These areas vary greatly in nutri-ent and oxygen levels from the nearbyocean. Compare and contrast oxygencontent between tide pools and theocean in the Problem-Solving Lab.

In the lightAs you move away from the inter-

tidal zone and into deeper water, theocean bottom is less and less affectedby waves or tides. Many organismslive in this shallow-water region thatsurrounds most continents andislands. Nutrients washed from theland by rainfall contribute to theabundant life and high productivityof this region of the photic zone.

The photic zone of the marinebiome also includes the vast expanseof open ocean that covers most ofEarth’s surface. Most of the organ-isms that live in the marine biome areplankton. Plankton, shown in Figure 3.8, are small organisms thatlive in the waters of the photic zone.Examine plankton more closely inthe MiniLab shown here. Planktoninclude autotrophs, such as diatoms,and heterotrophs, such as juvenilestages of many marine animals.

In the darkImagine a darkness blacker than

night and pressure so intense it exertshundreds of pounds of weight onevery square centimeter of yourbody’s surface. Does this sound like ahospitable place to live? Almost 90percent of the ocean is more than akilometer deep. In some places, itmay extend kilometers below thesunlit surface. Even though the ani-mals living there are very far belowthe photic zone where planktonabound, many of them still depend

on plankton for food, either directlyor indirectly by eating organisms thatfeed directly on plankton. Fishes liv-ing in the deep areas of the ocean areadapted to a life of darkness and ascarcity of food. What adaptationsmight help these organisms survivein this environment?

3.2 BIOMES 75

Figure 3.8 Plankton forms thebase of all aquaticfood chains, but notall organisms that eatplankton are small.Baleen whales andwhale sharks, someof the largest organ-isms that have everlived, consume vastamounts of plankton.

Marine plankton

Comparing and Contrasting



Freshwater biomesHave you ever gone swimming or

boating in a lake or pond? If so, youmay have noticed different kinds ofplants, such as cattails and sedges,growing around the shoreline andeven into the water, as shown inFigure 3.9. The shallow water inwhich these plants grow serves ashome for tadpoles, aquatic insects,turtles that bask on fallen tree trunks,and worms and crayfishes that bur-row into the muddy bottom. Insectlarvae, whirligig beetles, dragonflies,and fishes such as minnows, bluegill,and carp also live here.

If you have ever jumped into a deeplake on a warm summer day, you prob-ably got a cold surprise the instantyou entered the water. Although thesummer sun heats the lake’s surface,the water a few feet below the surfaceremains cold because cold water isdenser than warm water. If you wereto dive all the way to the bottom ofthe lake, you would discover morelayers of increasingly cold water asyou descended. These temperaturevariations within a lake are an abioticfactor that limits the kinds of organ-isms that can survive in deep lakes.

Another abiotic factor that limitslife in deep lakes is light. Not enough

sunlight penetrates to the bottom tosupport photosynthesis, so fewaquatic plants or algae grow. As aresult, population density is lower indeeper waters. Decay takes place atthe bottom of a lake. As dead organ-isms drift to the bottom, bacteriabreak them down and recycle thenutrients they contain.

Terrestrial BiomesImagine that you are setting off on

an expedition beginning at the northpole and traveling south to the equa-tor, as Figure 3.10 shows. Whatkinds of environmental changes doyou notice? The weather getswarmer, of course. You also see agradual change in the kinds of plantsthat cover the ground. At the snow-and ice-covered polar cap, tempera-tures are always freezing and noplants exist. A little farther south,where temperatures sometimes riseabove freezing but the soil neverthaws, you might see soggy groundwith just a few small cushions of low-growing lichens and plants.

As you continue on your journey,temperatures rise a little and youenter forests of coniferous trees.Farther south are grasslands and


Figure 3.9 The shallow waters in which these plantsgrow are highly pro-ductive and includefishes, algae, protists,insect larvae, tad-poles, and crayfishes.As you move fromthe margins of a lakeor pond toward thecenter, you find concentric bands of different speciesof plants.

Arctic zone60° N

Tropic of Cancer30° NTropical zone

Temperate zone

deserts, with higher summertimetemperatures and little rain, anddeciduous forests, with more rain andlower temperatures than the grass-lands and deserts. Finally, as youapproach the equator, you may findyourself surrounded by the lushgrowth of a tropical forest, where itrains almost every day.

As you move south from the northpole, you find yourself travelingthrough one biome after another.The graph in Figure 3.11 shows howtwo abiotic factors—temperature andprecipitation—influence the kind ofclimax community that develops in aparticular part of the world. Smalldifferences in temperature or precipi-tation can create many different cli-max communities, ecosystems, andbiomes. Look at the distribution ofthe six most common terrestrial bio-mes in Focus On Biomes.

77

Annual Precipitation vs. Temperature for Various Biomes

Ann

ual p

reci

pita

tion

(cm

)

Average temperature (°C)

400

300

200

100

-10 0 10 20 30

Tropicalrain

forest

Tropicalseasonal

forestTemperate forest

Thorn forest Savanna

Thorn scrub

Desert

Taiga

Tundra

Temperaterain forest

WoodlandGrassland

Shrubland

Figure 3.11 If you know the average annual temperature and rate ofprecipitation of a particular area, you should be able todetermine the climax community that will develop.

Figure 3.10 Many different terrestial biomes are encountered as you travel southward from the north pole to the equator.

A biome is a large group ofecosystems that share thesame type of mature climaxcommunity undergoing little orno succession. When you thinkof a biome, you may imaginelions on an African grassland or monkeys in the rain forest.But ecologists look at climaxcommunities of plants ratherthan animals. Because plantsdon’t migrate, they are a betterindicator of the long-term characteristics of a biome.

BiomesFOCUS ON

DESERT

GRASSLAND

TAIGA

SALTWATER

WATER LILY

78

1 THINKING CRITICALLY Which biome do you think would recovermost slowly from destruction arising from natural events or human causes?Explain.

2 COMPARING AND CONTRASTING Think about the general pattern of biome types that exists from the equator to the poles. Do you think you would find a similar pattern if you climbed from the foot of a very high mountain to its peak? Explain.

EXPANDING Your View

TUNDRA

TROPICAL RAIN FOREST

BIOMES Earth’s surface is marvelously diverse.Millions of species find a home here. But their distribution is not random.As the world map shows,Earth’s biomes exhibita definite pattern.

In general, three factors—latitude, altitude, precipi-tation—determine which

biome dominates a terrestrial loca-tion. A rainy, low-lying area near the Equator will have a tropical rainforest as climax vegetation. A fewkilometers away on a mountainside,ecologists may find plants typical ofa biome thousands of kilometers tothe north or south.

Look at the world map. Notice thatEarth is more than two-thirds water.This water is mostly oceans, whichmake up the saltwater biome.Freshwater from precipitationmakes up the other major waterbiome on land.

TEMPERATE FOREST

Life on the tundraAs you begin traveling south from

the north pole, you reach the first oftwo biomes that circle the pole. Thisfirst area is the tundra (TUN druh), atreeless land with long summer daysand short periods of winter sunlight.

Because temperatures in the tundranever rise above freezing for long,only the topmost layer of soil thawsduring the summer. Underneath thistopsoil is a layer of permanentlyfrozen ground called permafrost.Some areas of permafrost haveremained frozen for so long that thefrozen bodies of animals that havebeen extinct for thousands of years,

such as the elephantlike mammoth,are sometimes found there.

In most areas of the tundra, thetopsoil is so thin it can support onlyshallow-rooted grasses and othersmall plants. The soil is also lacking innutrients. The process of decay is soslow due to the cold temperatures thatnutrients are not recycled quickly.

Summer days on the tundra maybe long, but the growing season isshort. Because all food chains dependon the producers of the community,the short growing season is a limitingfactor for life in this biome. Forexample, typical flowering tundraplants, Figure 3.12, are grasses,dwarf shrubs, and cushion plants.These organisms live a long time andare resistant to drought and cold.

Mosquitoes and other bitinginsects are some of the most commontundra animals, at least during theshort summer. The tundra is alsohome to a variety of small animals,including ratlike lemmings, weasels,arctic foxes, snowshoe hares, snowyowls, and hawks. Musk oxen, caribou,and reindeer are among the few largeanimals that inhabit this biome dur-ing the summer months. Figure 3.13shows two common tundra animals.

80

Figure 3.12 Grasses, grasslikesedges, small annuals,and reindeer moss, a type of lichen onwhich reindeer feed,are the most numer-ous producers of thetundra. The shortgrowing season may last fewer than 60 days.

Figure 3.13 Snowy owls (a) arelemming (b) preda-tors. Lemmings arethe most numerousmammals living intundra communities.Populations of thesesmall, furry animalsrise to exceedinglyhigh numbers. As thelemming populationincreases, so does thepopulation of snowyowls.

a

b

Life on the taigaJust south of the tundra lies

another biome that circles the northpole. The taiga (TI guh), also calledthe northern coniferous forest, is aland of larch, fir, hemlock, and sprucetrees, as shown in Figure 3.14.

How can you tell when you leavethe tundra and enter the taiga? Theline between any two biomes is indis-tinct, and patches of one blendalmost imperceptibly into the other.For example, if the soil in the taiga iswaterlogged, a peat swamp habitatdevelops that looks much like tundra.Taiga communities are usually some-what warmer and wetter than tundra,but the prevailing climatic conditionsare still harsh, with long, severe win-ters and short, mild summers.

In the taiga, which stretches acrossmuch of Canada, Northern Europe,and Asia, permafrost is usuallyabsent. The topsoil, which developsfrom decaying coniferous needles, isacidic and poor in minerals. Whenfire or logging disrupt the taiga com-munity, the first trees to recolonizethe land may be birch, aspen, or

other deciduous species because thenew soil conditions are within theirranges of tolerance. The abundanceof trees in the taiga provides morefood and shelter for animals than thetundra. More large species of animalsare found in the taiga as comparedwith the tundra. Figure 3.15 showssome animals of the taiga.

Figure 3.14 The dominant climaxplants of the taiga inNorth America areprimarily fir andspruce trees.

Figure 3.15 The taiga stretches across most ofCanada, Northern Europe, and Asia.

The lynx is a predator thatdepends on the snowshoe hareas its primary source of food.

AA

Caribou arelarge, herbivo-rous mammalsof the taiga,where theymay be foundduring mostof the year.

CC

During the winter, the snowshoehare grows a thick, white wintercoat that includes extra hair onits feet for warmth.

BB

81

Life in the desertThe driest biome is the desert

biome. A desert is an arid regionwith sparse to almost nonexistentplant life. Deserts usually get less than25 cm of precipitation annually. Onedesert, the Atacama Desert in Chile,is the world’s driest place. This desertreceives an annual rainfall of zero.

Vegetation in deserts varies greatly,depending on precipitation levels.Areas that receive more rainfall pro-duce a shrub community that mayinclude drought-resistant trees suchas mesquite. Less rainfall supportsscattered plant life and produces anenvironment with large areas of bare

ground. The driest deserts are drift-ing sand dunes with virtually no lifeat all. Plants have developed variousadaptations for living in arid areas, asshown in Figure 3.16. Many desertplants are annuals that germinatefrom seed and grow to maturityquickly after sporadic rainfall. Cactihave leaves reduced to spines, photo-synthetic stems, and thick waxy coat-ings that reduce water loss. Theleaves of some desert plants curl up,or even drop off altogether, to reducewater loss during extremely dryspells. Desert plants sometimes havespines, thorns, or poisons that act todiscourage herbivores.

Most desert mammals are smallherbivores that remain under coverduring the heat of the day, emergingat night to forage on plants. The kan-garoo rat is a desert herbivore thatdoes not have to drink water. Theserodents obtain all the water they needto live from the water content in theirfood. Coyotes, hawks, owls, and road-runners are carnivores that feed onthe snakes, lizards, and small mam-mals of the desert. Scorpions are anexample of a desert carnivore thatuses venom to capture prey. Two ofthe many reptiles that make the deserttheir home are shown in Figure 3.17.

Figure 3.16 Creosote bushes covermany square kilome-ters of desert in thesouthwestern UnitedStates. These plantshave yellow flowersand small leavescoated with a waxyresin that helps reducewater loss.

Figure 3.17 Lizards, tortoises, andsnakes are numerousin desert communi-ties. Desert tortoisesfeed on insects andplants (a). Venomoussnakes such as thediamondback rat-tlesnake are majorpredators of smallrodents (b).

a

b

82

Life in the grasslandIf an area receives between 25 and

75 cm of precipitation annually, agrassland usually forms. Grasslandsare large communities covered withgrasses and similar small plants.Grasslands, such as the ones shown inFigure 3.18, occur principally in cli-mates that experience a dry season,where insufficient water exists to sup-port forests. Called prairies inAustralia, Canada, and the UnitedStates, these communities are calledsteppes in Russia, savannas in Africa,and pampas in Argentina. A grasslandin the United States can be found inYellowstone National Park. Find outhow Yellowstone became our firstnational park in the LiteratureConnection at the end of this chapter.

Grasslands contain fewer than tento 15 trees per hectare, though largernumbers of trees are found nearstreams and other water sources.This biome occupies more area thanany other terrestrial biome, and it hasa higher biological diversity thandeserts, often with more than 100species per acre.

The soils of grasslands have con-siderable humus content becausemany grasses die off each winter,leaving decay byproducts to build upin the soil. Grass roots survive

3.2 BIOMES 83

through the winter, enlarging everyyear to form a continuous under-ground mat called sod.

Because they are ideal for growingcereal grains such as oats, rye, andwheat, which are different species ofgrasses, grasslands have becomeknown as the breadbaskets of theworld. Many other plant species livein this environment, includingdrought-resistant and late-summer-flowering species of wildflowers, suchas blazing stars and sunflowers.

Most grasslands are populated bylarge herds of grazing animals, suchas bison, a species of mammal nativeto the American prairies, shown inFigure 3.18. Millions of bison, com-monly known as buffalo, once rangedover the American prairie, wherethey were preyed upon by wolves,coyotes, and humans. Other impor-tant prairie animals include prairiedogs, which are seed-eating rodentsthat build underground “towns”known to stretch across mile aftermile of grassland, and the foxes andferrets that prey on them. Manyspecies of insects, birds, and reptiles,also make their homes in grasslands.

Figure 3.18 Summers are hot, wintersare cold, and rainfall isoften uncertain in a grass-land (a). The prairies ofAmerica support bison aswell as many species ofbirds and insects (b).

b

a

Life in the temperate forestWhen precipitation ranges from

about 70 to 150 cm annually in thetemperate zone, temperate deciduousforests develop. Temperate forestsare dominated by broad-leaved hard-wood trees that lose their foliageannually, Figure 3.19.

When European settlers firstarrived on the east coast of NorthAmerica, they cleared away vasttracts of temperate forest for farm-land. The thin soil of the mountain-ous regions was soon depleted bycrops, and farmers abandoned theirland. Since then, secondary succes-sion has restored much of the origi-nal forest.

The soil of temperate forests usu-ally consists of a top layer that is richin humus and a deeper layer of clay.If mineral nutrients released by thedecay of the humus are not immedi-ately absorbed by the roots of the liv-ing trees, they may be washed intothe clay and lost from the food webfor many years.

The animals that live in the tem-perate deciduous forest, as shown inFigure 3.20, include familiar squir-rels, mice, rabbits, deer, and bears.Many birds, such as bluejays, live inthe forest all year long, whereas oth-ers, such as the great crested fly-catcher, migrate south to tropicalregions during the winter.

Figure 3.19 There are many typesof temperate forests,each described by thetwo or three domi-nant species of trees.Typical trees of thetemperate forestinclude birch, hickory,oak, beech, andmaple.

Figure 3.20 Black bears and deerhave always beenresidents of temper-ate forests in theUnited States. Otherabundant animals in temperate forests are squirrels andsalamanders.

84

Life in tropical rain forestsTropical rain forests, such as the

one shown in Figure 3.21, are hometo more species of organisms thanany other place on Earth. For example, one small national park inCosta Rica has more species of but-terflies than all of North America.One tree in a South American rainforest was found to contain morespecies of ants than exist in all of theBritish Isles. The huge number ofspecies in tropical rain forests hasmade their protection from humandestruction an important mission ofmany people.

As their name implies, tropicalrain forests have warm tempera-tures, wet weather, and lush plantgrowth. These forests are warmbecause they are near the equator.The average temperature is about25°C. They are moist because windpatterns drop a lot of precipitationon them. Rain forests receive at least200 cm of rain annually; some rainforests receive 600 cm.

Why do tropical rain forests con-tain so many species? The followinghypotheses have been proposed byecologists: 1. Due to their location near the

equator, tropical rain forests werenot covered with ice during thelast ice age. Thus, the communi-ties of species had more time toevolve.

2. Unlike the temperate forests—where deciduous trees drop theirleaves in autumn—the warmweather near the equator givestropical rain forest plants year-round growing conditions. Thiscreates a greater food supply intropical rain forests, which can sup-port larger numbers of organisms.

3. Tropical rain forests provide amultitude of possible habitats fordiverse organisms.

One reason for the large numberof niches is the vertical layering ofthe tropical rain forest. Just as alibrary has shelves to hold morebooks, a tropical rain forest has layersthat allow more species to exist. Howare these layers arranged? Find outby reading the Inside Story. From bot-tom to top, these layers are theground, understory, and canopy lay-ers. The layers often blend together,but their differences allow manyorganisms to find a niche.

Most of the nutrients in a tropicalrain forest are tied up in the livingmaterial. There are very few nutrientsheld in the soil. The hot humid cli-mate enables ants, termites, fungi,and other decomposers to breakdown dead plants and animals rapidly.Plants must quickly absorb these

Figure 3.21Warm temperatures,high humidity, andabundant rainfallallow the lushgrowth and greatspecies diversityfound in the tropicalrain forest.

85


A Tropical Rain Forest

The layers of a tropical rain forest provide niches for thou-sands of species. Ecologists generally consider rain forests

to have three layers. The illustration shows organisms in aCentral American tropical rain forest.

Critical Thinking How are the niches in the canopy different from those in the understory?

INSIDESSTORTORYY

INSIDE

Canopy The canopy layer, 25-45meters high, is a living roof. The treetops are exposed to rain, sunlight,and strong winds. A few giant treescalled emergents poke through thecanopy. Monkeys frequently passthrough. Birds, such as the beautifulscarlet macaw, live on the fruits andnuts of the trees.

11

Understory In the understory, theair is still, humid, and dark. Vinesand trees grow from the soil to thecanopy. Leaf cutter ants harvestleaves and bring them to theground. Plants include ferns, broad-leaved shrubs, and dwarf palms.Insects are common in the under-story. The limbs of the trees arecoated with a thick layer of mossesand other epiphytes. Birds and batsprey upon the insects. Tree frogs arecommon understory amphibians.Reptiles include chameleons andsnakes.

22

Ground The ground layer is amoist forest floor. Leaves and otherorganic materials decay quickly.Roots spread throughout the top 18inches of soil, competing for nutri-ents. Mammals living on the groundinclude rodents and cats, such as thejaguar. Ants, termites, earthworms,bacteria, and fungi live in the soiland decompose organic materials.

33

3.2 BIOMES 87

Section AssessmentSection AssessmentUnderstanding Main Ideas1. Explain why the photic and aphotic zones of

marine biomes are interdependent.2. What is the most important abiotic factor that

limits distribution of the tundra biome?3. Describe some common plants and animals from

a tropical rain forest and a grassland biome.4. Describe three changes you would observe as you

travel south from a taiga into a temperate forest.

Thinking Critically5. Shaneka and her family were planning a

trip to a foreign country. In reading before

the trip, Shaneka found that the winter was cold, the summer was hot, and most of the land was planted in fields of wheat. Infer whichbiome Shaneka’s family would visit. Explain your answer.

6. Making and Using Tables Make a table to show the climate, plant types, plant adaptations, animal types, and animal adaptations for the terrestrial biomes. For more help, refer to Organizing Informationin the Skill Handbook.

SKILL REVIEWSKILL REVIEW

nutrients before they are leachedout of the soil by the rain. Rain for-est trees have roots and mycorrhizaenear the surface that enable them toabsorb the nutrients. The shallowtree roots form a thick mat on thesurface of the soil. Roots that supporttall trees are sometimes greatlyenlarged or may form buttresses,which resemble the fins of a rocket.

Tropical rain forest habitats, suchas those of the species shown inFigure 3.22, are being destroyed byhuman activities. Rain forests are cutfor their hardwoods, such asmahogany. Farmers clear the rainforest land to grow crops. After a fewyears, the crops deplete the soil ofnutrients, and the farmers must then

move on and clear a different rain for-est area. Rain forests are also clearedto produce grasslands for cattle.

Fortunately, people are realizingthe importance of tropical rainforests and efforts are aimed at pro-tecting these species-rich environ-ments. In some areas, logging is nowprohibited. But in areas where peopleneed to use the land, they are beingtaught how to preserve the land theycurrently have cleared through croprotation and fertilization.

a

Figure 3.22Tropical rain forests are rich ecosystems. Sloths (a)and other mammals, as well as a multitude of birdspecies such as this black-headed cacique (c), livein the rain forest canopy. Insects, such as thisHercules beetle (b), are numerous in the understory.

b

c


Succession in a Jar

S uccession is usually described as changes seen in ecosystems followingforests destroyed by fire or in farmlands left to lie fallow. Succession,

however, can also be observed in a micro ecosystem, such as in a jar of pondwater. The type and number of organisms will change over time. The advan-tage of studying this type of succession is that it will take only weeks, not years.

INVESTIGATEINVESTIGATE

ProblemCan you observe succession

in a pond water ecosystem?

Objectives In this BioLab, you will:■ Observe changes in three

pond water environments. ■ Count the number of each

type of organism seen.■ Determine if the changes ob-

served illustrate succession.

Materialsglass jars, 3pasteurized spring water

pond water containing plant materiallabelsglass slides and cover glassesdroppersplastic wrapcooked white riceteaspoon, plasticmicroscope

Safety PrecautionsAlways wear goggles in the lab.

Skill HandbookUse the Skill Handbook if you need

additional help with this lab.

PREPARATIONPREPARATION

1. Examine the pond water sampleprovided by your teacher.

2. Fill three glass jars with equalamounts of pasteurized (steril-ized) spring water.

3. Label them A, B, and C. Addyour name and today’s date toeach label.

4. Add the following to each of yourthree jars:Jar A: Nothing elseJar B: 3 grains of cooked whiterice

Jar C: 3 grains of cooked whiterice, one teaspoon of pond sedi-ment, and a small amount of anyplant material present in thepond water.

5. Record the turbidity of each jarin the data table below. Turbiditymeans cloudiness and can best bejudged by comparing jar A to Bto C. Score turbidity on a scale of1 to 10, with 1 meaning very clearwater and 10 meaning verycloudy water.

PROCEDUREPROCEDURE

6. Gently swirl the contents of eachjar.

7. Using a different clean dropperfor each jar, remove a sample andprepare a wet mount of the liquidfrom each jar. Label each glassslide A, B, or C to avoid any mix-up. CAUTION: Handle glassslides, coverslips, and glasswarecarefully.

8. Observe each slide under lowpower. Look for autotrophic andheterotrophic organisms. Identifythese organisms by name, describetheir appearance, or make a sketchof what they look like.

3.2 BIOMES 89

A

B

C

A

B

Date Jar Turbidity

Name, description,or diagram oforganism seen

Autotroph orheterotroph?

Number seen per low-powerfield

Data Table

Going FurtherGoing Further

Experimenting Design and carry out anexperiment that tests the effect of tempera-ture on the rate at which succession occursin pond water.

To find out more about succession, visit the

Glencoe Science Web site. science.glencoe.com

1. Applying Concepts Which ofthe three jars was a control?Explain why.

2. Observing and Inferring Whatmight have been the role of thecooked rice?

3. Recognizing Cause and EffectTurbidity was a means of indirectlymeasuring the amount of bacterialgrowth in the jars. Why was therelittle, if any, turbidity in jar A?

4. Analyzing Information Describethe changes over time in thenumber and type of heterotrophs.Could these changes be describedas succession? Explain.

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

5. Observing and Inferring Wereyou able to observe a climaxecosystem during this experi-ment? Explain your answer.

9. Report the number of each typeof organism as viewed in a low-power field of view (the circle oflight seen when looking throughthe microscope under low poweris your field of view).

10. Complete the data table for yourfirst observations.

11. Cover each jar with either a lid orplastic wrap and place them in alighted area.

12. Observe the jars every three daysfor several weeks, repeating steps5-11 each time an observation ismade. Use your data table torecord your observations.

BIOLOGY


The first, and largest, national park in the world was commissioned by an act of the

United States Congress in 1872 as YellowstoneNational Park. Because of the writing and

influence of a man named John Muir, Congressalso created the National Parks System,

which includes Yellowstone, to preserve the landsthat we still enjoy today. In recognition of his contributions, Muir is often called

“The Father of our National Park System.”

Although it includes waterfalls, a high-eleva-tion lake with one hundred and ten miles of

shoreline, and one of the world’s largest volcanicexplosion craters, Yellowstone National Park isprobably most famous for its hot springs andgeysers. In fact, more boiling caldrons and spout-ing plumes of hot water and mud are found inYellowstone than in all of the rest of the world.In his book, The Yellowstone National Park, Muirprovides his readers with the following descrip-tion of the boiling basins and geysers:

Many of these pots and caldrons have beenboiling thousands of years. Pots of sulphurousmush, stringy and lumpy, and pots of broth asblack as ink, are tossed and stirred with constantcare, and thin transparent essences, too pure andfine to be called water, are kept simmering gen-tly in beautiful sinter cups and bowls that growever more beautiful the longer they are used.

Muir’s Dream As a young man Muir had avision of a “wildlands set aside by the govern-ment.” The purpose of these lands would be simplyto preserve the scenery and to educate peopleabout the natural wonders of the land. As anadult, he was an avid explorer and prolific writerwhose goals were to educate the public about thevalue of nature and the destructive effects manhad on the natural environment. Muir felt thatthe beauty of nature was as essential to the well-being of man as was food.

Over his lifetime,Muir wrote ten books andthree hundred articles popu-larizing the idea of wildernessconservation. His writings so affected the atti-tude of the public, and even presidents of theUnited States, towards preservation of our nat-ural resources that Muir has been called theUnited States’ most famous and influential naturalist and conservationist.


ConnectionLiteratureLiterature

Connection

CONNECTION TO BIOLOGYCONNECTION TO BIOLOGY

“Old Faithful” geyser (above)and boiling mud pots (inset)

The Yellowstone NationalPark by John Muir

What other authors have written material thatinfluenced public opinion about the value ofnature and preserving our natural environment?

To find out more about Yellowstone National Park,

visit the Glencoe Science Web site. science.glencoe.com

BIOLOGY


Chapter 3 AssessmentChapter 3 Assessment

SUMMARYSUMMARY

Section 3.1

Section 3.2

Main Ideas■ Communities, populations, and individual

organisms occur in areas where biotic or abioticfactors fall within their range of tolerance.Abiotic or biotic factors that define whether ornot an organism can survive are limiting factors.

■ The sequential development of living communi-ties from bare rock is an example of primary suc-cession. Secondary succession occurs when com-munities are disrupted. Left undisturbed, bothprimary succession and secondary succession willeventually result in a climax community.

Vocabularyclimax community (p. 70)limiting factor (p. 68)primary succession (p. 69)secondary succession

(p. 71)succession (p. 69)

Main Ideas■ Biomes are large areas that have characteristic

climax communities. Aquatic biomes may bemarine or freshwater. Estuaries occur at theboundaries of marine and freshwater biomes.Approximately three-quarters of Earth’s surfaceis covered by aquatic biomes, and the vastmajority of these are marine communities.

■ Terrestrial biomes include tundra, taiga, desert,grassland, deciduous forest, and tropical rainforest. Two climatic factors, temperature andprecipitation, are the major limiting factors forthe formation of terrestrial biomes.

Vocabularyaphotic zone (p. 73)biome (p. 72)desert (p. 82)estuary (p. 73)grassland (p. 83)intertidal zone (p. 74) permafrost (p. 80)photic zone (p. 73)plankton (p. 75)taiga (p. 81)temperate forest (p. 84)tropical rain forest

(p. 85)tundra (p. 80)

Biomes

CHAPTER 3 ASSESSMENT 91

1. The removal of which of the followingorganisms would have the biggest impact ona marine ecosystem?a. fishes c. shrimpb. whales d. plankton

2. An undersea volcano erupts creating a newisland off the coast of South Carolina. Lifeslowly starts appearing on the island. Whatwould probably be the first species to growand survive?a. maple trees c. lichensb. finches d. grasses

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS 3. The changes in communities that take placeon a new island would best be described as________.a. primary succession c. tertiary successionb. secondary succession d. none of the above

4. Which of the following is true?a. Temperate forests have more rainfall than

tropical rain forests.b. Tropical rain forests have more species of

trees than temperate forests.c. Temperate forests are closer to the equator

than tropical rain forests.d. Tropical rain forests are younger than tem-

perate forests.

Communities


92 CHAPTER 3 ASSESSMENT

TEST–TAKING TIPTEST–TAKING TIP

Beat the Clock and Then Go BackAs you take a practice test, pace yourself to finisha few minutes early so you can go back and checkover your work. You’ll usually find a mistake ortwo. Don’t worry. It is better to make correctionsthan to hand in a test with wrong answers.

9. Locations of biomes are usually determinedby ________.a. temperature and altitudeb. temperature and precipitationc. altitude and precipitationd. soil type and temperature

10. The kangaroo rat conserves its water andobtains all its water from the food it eats. Inwhat ecosystem is the kangaroo rat mostlikely to live?a. tropical rain forest c. taigab. desert d. savanna

11. The layer of frozen soil found in the tundrais called the ________.

12. A species that first occupies and lives in anarea is called a ________ species.

13. Aquatic areas with a mix of salt water andfreshwater are called ________. They containsalt marsh ecosystems where the dominantplant life is ________.

14. Cereal grains grow best in the biome calledthe ________. These areas are called________ in the United States and ________in Africa.

15. An ecologist climbs the tallest tree in a patchof rain forest. She is probably at the ________layer.

16. Between the north pole and the taiga lies the________. In this area there are more________, a furry, ratlike animal, than anyother mammals.

17. Beech trees and maple trees dominate a for-est that has stayed the same for 100 years.The ecological term for this stable commu-nity is a ________ community.

18. The terrestrial biome with lush plant growthbut poor soil is the ________.

19. The biome shown here is most likely ________.

5. The photograph shows a forest in the UnitedStates. The annual rainfall is 300 cm and theaverage temperatureis 15°C. What type offorest is shown in the photograph?a. tropical rain forestb. coniferous forestc. temperate rain

forestd. temperate forest

6. A lack of food prevents further growth in adeer population. This is an example of a________.a. range of tolerance c. photic zoneb. limiting factor d. biome

7. Most species of ocean fishes spend theirentire life in salty water. However, somefishes, such as the flounder and salmon, travelup freshwater rivers to reproduce. Whichstatement is most likely true about thesalmon and flounder?a. They aren’t affected by physiological stress.b. They have no zones of intolerance.c. They have wider optimum ranges.d. They are pioneer species.

8. A deep sea fisherman catches an ocean fish.This fish, like others of the same species, hasno developed eyes. Its habitat is most likelythe ________.a. intertidal zone c. photic zoneb. aphotic zone d. zone of intolerance


CHAPTER 3 ASSESSMENT 93

20. A diamondback rattlesnake rattles his rattleand you back into a cactus. You are mostlikely stuck in a ________ biome.

21. How may agriculture lead to soil erosion in agrassland biome?

22. How might annual fires affect the successionof a temperate deciduous forest?

23. Compare the biodiversity of the temperateforest biome with that of a tropical rain forestbiome.

24. Forming a Hypothesis What would be thecharacteristics of a successful pioneer speciesin a secondary succession?

25. Recognizing Cause and Effect Some plantseeds need fire to germinate. Describe theniche of these organisms in secondary succes-sion.

26. Concept Mapping Complete the conceptmap by using the following vocabulary terms:biomes, desert, grassland, temperate forest,tropical rain forest, tundra.

THINKING CRITICALLYTHINKING CRITICALLY

APPLYING MAIN IDEASAPPLYING MAIN IDEAS

ASSESSING KNOWLEDGE & SKILLSASSESSING KNOWLEDGE & SKILLS

The table below shows rates of decomposi-tion for terrestrial ecosystems.

Interpreting Data Study the table andanswer the following questions. 1. Which ecosystem has the slowest rate of

decomposition? a. tundrab. taigac. tropical rain forestd. desert

2. Where would a twig decay fastest?a. tundrab. taigac. tropical rain forestd. grassland

3. Sequencing Put the ecosystems in a list from fastest to slowest rates ofdecomposition.

4. Hypothesizing Suggest two possiblereasons why there are differences inrates of decomposition between the biomes.

5. Predicting What rating do you thinkthe following aquatic ecosystems wouldhave? Why?a. estuariesb. interdidal zonec. aphotic zoned. pond

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

CD-ROM

Ecosystem Rate

Tundra

Taiga

Desert

Temperate Forest

Tropical Rain Forest

Grassland

Table 3.1 Rates of Decomposition

– –

–

–

+

+++

++

the coldestterrestrial

occupies the most area

the driest

1.

2.

3.

4.

5.

6.

lots of trees


chapter 3: communities and biomes -...

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