chapter 8: ecosystems - ocala-chcocala-chc.wikispaces.com/file/view/ch08.pdf1 how ecosystems change...

Ecosystems

sections

1 How Ecosystems Change

2 BiomesLab Studying a Land Ecosystem

3 Aquatic EcosystemsLab Exploring Wetlands

Virtual Lab What are the different types of land environments?

The Benefits of WildfiresEcosystems are places where organisms,including humans, interact with each otherand with their physical environment. Insome ecosystems, wildfires are an essentialpart of the physical environment. Organismsin these ecosystems are well adapted to thechanges that fire brings, and can benefit from wildfires.

What traits might plants on thisburning hillside have that enable them to survive?Science Journal

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Sunshine State Standards—SC.D.1: The student recognizes that processes in the lithosphere,atmosphere, hydrosphere, and biosphere interact to shape the Earth; SC.D.2: understands theneed for protection of the natural systems on Earth; SC.G.2: understands the consequences ofusing limited natural resources; SC.H.2.

William Campbell/CORBIS SygmaWilliam Campbell/CORBIS Sygma

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Primary and SecondarySuccession Make the followingFoldable to help you illustrate

the main ideas about succession.

Fold a vertical sheet of paper in half from top to bottom.

Fold in half from side to side with the fold at the top.

Unfold the paper once. Cut only the fold of the top flap to make two tabs.

Turn the paper vertically and labelon the front tabs

as shown.

Illustrate and Label As you read the chapter,define terms and collect information under theappropriate tabs.

STEP 4

STEP 3

STEP 2

STEP 1

1. Complete a safety worksheet.

2. Examine a healthy houseplant in your classroom or home.

3. Describe the environmental conditions found in your classroom or home. For example, is the air humid or dry? Is theroom warm or cool? Does the temperaturestay about the same, or change during the day?

4. Using observations from step 1 and descriptions from step 2, hypothesize about the natural environment of the plants in your classroom or home.

5. Think Critically In your Science Journal,record the observations that led to yourhypothesis. How would you design anexperiment to test your hypothesis?

What environment dohouseplants need?The plants growing in your classroom orhome may not look like the same types ofplants that you find growing outside. Manyindoor plants don’t grow well outside in mostNorth American climates. Do the lab below todetermine what type of environment mosthouseplants thrive in.

Start-Up Activities

Preview this chapter’s contentand activities at fl6.msscience.com

primary succession

climax community

secondary succession

climax community

--InquiryInquiry

LA.A.1.3.4

William Campbell/CORBIS SygmaWilliam Campbell/CORBIS Sygma

http://fl6.msscience.com

Ecological Succession What would happen if the lawn at your home were never

cut? The grass would get longer, as in Figure 1, and soon itwould look like a meadow. Later, larger plants would grow fromseeds brought to the area by animals or wind. Then, trees mightsprout. In fact, in 20 years or less you wouldn’t be able to tell thatthe land was once a mowed lawn. An ecologist can tell you whattype of ecosystem your lawn would become. If it would becomea forest, they can tell you how long it would take and predict thetype of trees that would grow there. Succession refers to the pat-tern of gradual changes that occur in the types of species thatlive in an area. Succession occurs differently in different placesaround the world.

Primary Succession As lava flows from the mouth of a volcano, it is so hot that it destroys everything in its path. Whenit cools, lava forms new land composed of rock. It is hard toimagine that this land eventually could become a forest or grass-land someday.

The process of succession that begins in a place previouslywithout plants is called primary succession. It starts with thearrival of living things such as lichens (LI kunz). These livingthings, called pioneer species, are the first to inhabit an area.They survive drought, extreme heat and cold, and other harshconditions and often start the soil-building process.

■ Explain how ecosystems changeover time.

■ Describe how new communitiesbegin in areas without life.

■ Compare pioneer species and climax communities.

Understanding ecosystems and yourrole in them can help you manageyour impact on them and predictthe changes that may happen in the future.

How Ecosystems Change

Figure 1 This once-mowedcemetery is now full of longgrasses and wildflowers due tosecondary succession.

226 CHAPTER 8 Ecosystems

Benchmarks—SC.D.1.3.4 Annually Assessed (p. 227): The student knows the ways in which plantsand animals reshape the landscape; SC.H.2.3.1 (p. 226): The student recognizes that patterns existwithin and across systems.

Also covers: SC.G.1.3.2 (p. 228)

Review Vocabularyecosystem: community of

living organisms interacting with each other and their physical environment

New Vocabulary

• succession

• pioneer species

• climax community

FCAT Vocabulary

Darrell Gulin/CORBIS

SECTION 1 How Ecosystems Change 227

New Soil During primary succession, soil begins to form aslichens and the forces of weather and erosion help break downrocks into smaller pieces. When lichens die, they decay, addingsmall amounts of organic matter to the rock. Plants such asmosses and ferns can grow in this new soil. Eventually, theseplants die, adding more organic material. The soil layer thickens,and grasses, wildflowers, and other plants begin to take over.When these plants die, they add more nutrients to the soil. Thisbuildup is enough to support the growth of shrubs and trees. Allthe while, insects, small birds, and mammals have begun tomove in. What was once bare rock now supports a variety of life,as shown in Figure 2.

Secondary Succession What happens when a fire, such asthe one in Figure 3, disturbs a forest or when a building is torndown in a city? After a forest fire, not much seems to be leftexcept dead trees and ash-covered soil. After the rubble of a build-ing is removed, all that remains is bare soil. However, these placesdo not remain lifeless for long. The soil already contains the seedsof weeds, grasses, and trees. More seeds are carried to the area bywind and birds. Other wildlife may move in. Succession thatbegins in a place that already has soil and was once the home ofliving organisms is called secondary succession. Because soilalready is present, secondary succession occurs faster and has dif-ferent pioneer species than primary succession does.

Which type of succession usually starts without soil?

Figure 2 This exposed coral inthe Florida Keys has undergoneprimary succession.Describe how new soil forms.

Topic: EutrophicationVisit fl6.msscience.com for Web links to information abouteutrophication (yoo truh fih KAYshun)—secondary succession inan aquatic ecosystem.

Activity Using the informationthat you find, illustrate or describein your Science Journal this processfor a small freshwater lake.

Annually AssessedBenchmark Check

SC.D.1.3.4 How do plants,lichens, and other organic matterchange the landscape?

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David Muench/CORBIS


VISUALIZING SECONDARY SUCCESSION


Figure 3

In the summer of 1988, wind-driven flames likethose shown in the background photo sweptthrough Yellowstone National Park, scorching

nearly a million acres. The Yellowstone fire was one of the largest forest fires in United States history. Theimages on this page show secondary succession—the process of ecological regeneration—triggered by the fire.

Within weeks, grasses and other plantswere beginning to grow in the burned areas.Ecological succession was underway.

Many burned areas in the park openednew plots for stands of trees. This pictureshows young lodgepole pines in August1999. The forest habitat of America’s oldest national park is being restoredgradually through secondary succession.

After the fire, burned timber and blackenedsoil seemed to be all that remained. However,the fire didn’t destroy the seeds that were pro-tected under the soil.

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(l)Kevin R. Morris/CORBIS, (tr br)Jeff Henry, (bkgd.)Craig Fujii/Seattle Times

SECTION 1 How Ecosystems Change 229

Self Check1. Compare primary and secondary succession.

2. Describe adaptations of pioneer species.

3. Infer the kind of succession that will take place on anabandoned, unpaved country road.

4. Think Critically Show the sequence of events in pri-mary succession. Include the term climax community.

SummaryEcological Succession

• Succession is the natural, gradual changesover time of species in a community.

• Primary succession occurs in areas that previ-ously were without soil or plants.

• Secondary succession occurs in areas wheresoil has been disturbed.

• Climax communities have reached an endstage of succession and are stable.

• Climax communities have less diversity thancommunities in mid-succession.

Climax Communities A community of plants that is rela-tively stable and undisturbed and has reached an end stage ofsuccession is called a climax community. The beech-maple for-est shown in Figure 4 is an example of a community that hasreached the end of succession. New trees grow when larger, oldertrees die. The individual trees change, but the species remainstable. There are fewer changes of species in a climax commu-nity over time, as long as the community isn’t disturbed by wild-fire, avalanche, or human activities.

Primary succession begins in areas with no previous vegeta-tion. It can take hundreds or even thousands of years to developinto a climax community. Secondary succession is usually ashorter process, but it still can take a century or more.

Figure 4 This beech-maple forest is an example of a climaxcommunity.

5. Solve One-Step Equations A tombstone etched with1802 as the date of death has a lichen on it that is 6 cm in diameter. If the lichen began growing in 1802, calculate its average yearly rate of growth. MA.D.2.3.1

More Section Review fl6.msscience.com

SC.G.1.3.2

Rod Planck/Photo Researchers



Factors That Affect BiomesDoes a desert in Arizona have anything in common with

a desert in Africa? Both have heat, little rain, poor soil, water-conserving plants with thorns, and lizards. Even widelyseparated regions of the world can have similar biomes becausethey have similar climates. Climate is the average weatherpattern in an area over a long period of time. The two mostimportant climatic factors that affect life in an area are temper-ature and precipitation.

Major Biomes Large geographic areas that have similar climates and eco-

systems are called biomes (BI ohmz). Seven common typesof land biomes are mapped in Figure 5. Areas with similar cli-mates produce similar climax communities. Tropical rain forestsare climax communities found near the equator, where temper-atures are warm and rainfall is plentiful. Coniferous forests growwhere winter temperatures are cold and rainfall is moderate.

■ Explain how climate influencesland environments.

■ Identify seven biomes of Earth.■ Describe the adaptations of

organisms found in each biome.

Resources that you need to surviveare found in a variety of biomes.

Biomes

Figure 5 The land portion of Earth can be divided into seven biomes.

Benchmarks—SC.D.2.3.2 Annually Assessed (p. 237): The student knows the positive and negativeconsequences of human action on the Earth’s systems.

Also covers: SC.G.2.3.2 (p. 237), SC.G.2.3.4 Annually Assessed (p. 237), SC.H.1.3.1 (p. 238), SC.H.1.3.4(p. 238), SC.H.1.3.7 Annually Assessed (p. 238), SC.H.2.3.1 (p. 238)

Review Vocabularyclimate: the average weatherconditions of an area over manyyears

New Vocabulary

• biome • temperate rain

• tundra forest

• taiga • tropical rain

• temperate forestdeciduous • desertforest • grassland

NORTHAMERICA

SOUTHAMERICA

AFRICA

EUROPEA S I A

AUSTRALIA

Equator

Tropic of Capricorn

Antarctic Circle

Tropic of Cancer

Arctic Circle

DesertGrasslandTropical rain forestTemperate rain forestTemperate deciduous forest

TaigaTundra

fl6.msscience.com


SECTION 2 Biomes 231

Tundra At latitudes just south of the north poleor at high elevations, a biome can be found thatreceives little precipitation but is covered with icemost of the year. The tundra is a cold, dry, treelessregion, sometimes called a cold desert. Precipitationaverages less than 25 cm per year. Winters in theArctic can be six to nine months long. For some ofthese months, the Sun never appears above thehorizon and it is dark 24 hours a day. The averagedaily temperature is about –12°C. For a few daysduring the short, cold summer, the Sun is alwaysvisible. Only the top portion of soil thaws in thesummer. Below the thawed surface is a layer of per-manently frozen soil called permafrost, shown inFigure 6. Alpine tundra, found above the treelineon high mountains, have similar climates. Tundrasoil has few nutrients because the cold tempera-tures slow the process of decomposition.

Tundra Life Tundra plants are adapted to drought and cold.They include mosses, grasses, and small shrubs, as seen in Figure 7. Many lichens grow on the tundra. During the summer,mosquitoes, blackflies, and other biting insects fill the air.Migratory birds such as ducks, geese, shorebirds, and songbirdsnest on the Arctic tundra during the summer. Other inhabitantsinclude hawks, snowy owls, and willow grouse. Mice, voles, lem-mings, arctic hares, caribou, reindeer, and musk oxen also arefound there.

People are concerned about overgrazing by animals on thetundra. Fences, roads, and pipelines have disrupted the migra-tory routes of some animals and forced them to stay in a limitedarea. Because the growing season is so short, plants and othervegetation can take decades to recover from damage.

Figure 6 This permafrost inAlaska is covered by soil thatfreezes in the winter and thaws in the summer. Infer what types of problems this might cause for people living in this area.

Figure 7 Lichens, mosses,grasses, and small shrubs thrive onthe tundra. Ptarmigan also live onthe tundra. In winter, their feath-ers turn white. Extra feathers ontheir feet keep them warm andprevent them from sinking into the snow.Tundra

Ptarmigan

(t)Steve McCutcheon/Visuals Unlimited, (bl)Pat O'Hara/DRK Photo, (br)Erwin & Peggy Bauer/Tom Stack & Assoc.


Taiga South of the tundra—betweenlatitudes 50°N and 60°N and stretch-ing across North America, northernEurope, and Asia—is the world’slargest biome. The taiga (TI guh),shown in Figure 8, is a cold, forestregion dominated by cone-bearingevergreen trees. Although the winter islong and cold, the taiga is warmer andwetter than the tundra. Precipitation ismostly snow and averages 35 cm to100 cm each year.

Most soils of the taiga thaw com-pletely during the summer, making itpossible for trees to grow. However,

permafrost is present in the extreme north-ern regions of the taiga. The forests of thetaiga might be so dense that little sunlightpenetrates the trees to reach the forest floor.However, some lichens and mosses do growon the forest floor. Moose, lynx, shrews,bears, and foxes are some of the animals thatlive in the taiga.

Temperate Deciduous Forest Temperate regions usuallyhave four distinct seasons each year. Annual precipitation rangesfrom about 75 cm to 150 cm and is distributed throughout theyear. Temperatures range from below freezing during the winterto 30°C or more during the warmest days of summer. Most ofFlorida is in the temperate deciduous biome, with an averagerainfall between 120 cm to 150 cm. The average temperaturerange is 15°C to 29°C.

Figure 8 The taigais dominated by cone-bearingtrees. The lynx, a mammal adaptedto life in the taiga, has broad,heavily furred feet that act likesnowshoes to prevent it from sinking in the snow.Infer why “snowshoe feet” areimportant for a lynx.

Figure 9 White-taileddeer are one of manyspecies that you can find in a deciduous forest. Inautumn, the leaves ondeciduous trees changecolor and fall to the ground.

(tl)Peter Ziminski/Visuals Unlimited, (c)Leonard Rue III/Visuals Unlimited, (bl)C.C. Lockwood/DRK Photo, (br)Larry Ulrich/DRK Photo


Temperate Forest Life Many ever-green trees grow in the temperate regionsof the world. However, most of thetemperate forests in Europe and NorthAmerica are dominated by climax com-munities of deciduous trees, which losetheir leaves every autumn. These forests,like the one in Figure 9, are called temperate deciduous forests. In theUnited States, most of them are locatedeast of the Mississippi River.

A unique aspect of organisms in a tem-perate deciduous biome is that they haveadaptations that allow them to withstandenvironmental seasonal changes. Each sea-son has a different range of temperaturesand amounts of precipitation. The loss ofleaves by trees is one adaptation. In winterthere is not enough sunlight and water fordeciduous trees to make their own food.The leaves drop and trees use storedenergy. Some plants go dormant in coldweather. Extra fur grows on some mam-mals, which insulates them in cold weather.This fur is shed in hot weather. Some ani-mals become inactive during cold weather,and some become inactive in hot weather.

Temperate Rain Forest New Zealand,southern Chile, and the Pacific Northwestof the United States are some of the placeswhere temperate rain forests, shown in Figure 10, are found. Theaverage temperature of a temperate rain forest ranges from 9°C to12°C. Precipitation ranges from 200 cm to 400 cm per year.

Trees with needlelike leaves dominate these forests, includ-ing the Douglas fir, western red cedar, and spruce. Many grow togreat heights. Animals of the temperate rain forest include theblack bear, cougar, bobcat, northern spotted owl, and marbledmurrelet. Many species of amphibians also inhabit the temper-ate rain forest, including salamanders.

The logging industry in the Northwest provides jobs formany people. However, it also removes large parts of the tem-perate rain forest and destroys the habitat of many organisms.Many logging companies now are required to replant trees toreplace the ones they cut down. Also, some rain forest areas areprotected as national parks and forests.

Figure 10 In the Olympic rainforest in Washington State, mossesand lichens blanket the groundand hang from the trees. Wetareas are perfect habitats foramphibians like the Pacific giantsalamander above.

(t)Fritz Polking/Visuals Unlimited, (b)William Grenfell/Visuals Unlimited


Tropical Rain Forest Warm temperatures, wet weather, andlush plant growth are found in tropical rain forests. Theseforests are warm because they are near the equator. The averagetemperature, about 25°C, doesn’t vary much between night andday. Most tropical rain forests receive at least 200 cm of rainannually. Some receive as much as 600 cm of rain each year.

Tropical rain forests, like the one in Figure 11, are home toan astonishing variety of organisms. They are one of the mostbiologically diverse places in the world. For example, one tree ina South American rain forest might contain more species of antsthan exist in all of the British Isles.

Tropical Rain Forest Life Different animals and plants livein different parts of the rain forest. Scientists divide the rain for-est into zones based on the types of plants and animals that livethere, just as a library separates books about different topics ontoseparate shelves. The zones include: forest floor, understory,canopy, and emergents, as shown in Figure 12. These zones oftenblend together, but their existence provide different habitats formany diverse organisms to live in the tropical rain forest.

What are the four zones of a tropical rain forest?

Although tropical rain forests support a huge variety oforganisms, the soil of the rain forest contains few nutrients.Over the years, nutrients have been washed out of the soil byrain. On the forest floor, decomposers immediately break downorganic matter, making nutrients available to the plants again.

Figure 11 Tropical rain forestsare lush environments that containsuch a large variety of species thatmany have not been discovered.

Modeling RainForest LeavesProcedure1. Draw an oval leaf about

10 cm long on a piece ofposter board. Cut it out.

2. Draw a second leaf thesame size but make oneend pointed. This is calleda drip tip. Cut this leaf out.

3. Hold your hands palm-sideup over a sink and havesomeone lay a leaf on eachone. Point the drip tipaway from you. Tilt yourhands down but do notallow the leaves to fall off.

4. Have someone gently spraywater on the leaves andobserve what happens.

Analysis1. From which leaf does

water drain faster?2. Infer why it is an

advantage for a leaf to getrid of water quickly in a rain forest.

Lynn M. Stone/DRK PhotoLynn M. Stone/DRK Photo

Human Impact Farmers that live in tropical areas clear theland to farm and to sell the valuable wood. After a few years, thecrops use up the nutrients in the soil, and the farmers must clearmore land. As a result, tropical rain forest habitats are beingdestroyed. Through education, people are realizing the valueand potential value of preserving the species of the rain forest.In some areas, logging is prohibited. In other areas, farmers aretaught new methods of farming so they do not have to clear rainforest lands continually.

Canopy The canopy includesthe upper parts of the trees.It's full of life—insects, birds,reptiles, and mammals.

Emergents These giant trees are much higher than the average canopy tree. Birds, such as the macaw, and insects are found here.

Understory This dark, cool environmentis under the canopy leaves but above theground. Many insects, reptiles, andamphibians live in the understory.

Forest Floor The forest floor ishome to many insects and thelargest mammals in the rainforest generally live here.

Figure 12 Tropical rain forestscontain abundant and diverseorganisms.


SC.D.2.3.2 Name a positive anda negative impact of humanaction in a tropical rainforest.

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Desert The driest biome on Earth is the desert. Desertsreceive less than 25 cm of rain each year and support little plantlife. Some desert areas receive no rain for years. When rain doescome, it quickly drains away. Any water that remains on theground evaporates rapidly.

Most deserts, like the one in Figure 13, are covered with athin, sandy, or gravelly soil that contains little organic matter.Due to the lack of water, desert plants are spaced far apart andmuch of the ground is bare. Barren, windblown sand dunes arecharacteristics of the driest deserts.

Why is much of a desert bare ground?

Desert Life Desert plants are adapted for survival in theextreme dryness and hot and cold temperatures of this biome.Most desert plants are able to store water. Cactus plants areprobably the most familiar desert plants of the western hemi-sphere. Desert animals also have adaptations that help them sur-vive the extreme conditions. Some, like the kangaroo rat, neverneed to drink water. They get all the moisture they need fromthe breakdown of food during digestion. Most animals areactive only during the night, late afternoon, or early morningwhen temperatures are less extreme. Few large animals arefound in the desert.

In order to provide water for desert cities, rivers and streamshave been diverted. When this happens, wildlife tends to movecloser to cities in their search for food and water. Educationabout desert environments has led to an awareness of the impact of human activities. As a result, large areas of desert havebeen set aside as national parks and wilderness areas to protectdesert habitats.

Figure 13 Desert plants, likethese in the Sonoran Desert, areadapted for survival in the extremeconditions of the desert biome. Thegiant hairy scorpion found in somedeserts has a venomous sting.

Desertification When veg-etation is removed from soilin areas that receive littlerain, the dry, unprotectedsurface can be blown away.If the soil remains bare, adesert might form. Thisprocess is called desertifi-cation. Look on a biomemap and hypothesize aboutwhich areas of the UnitedStates are most likely tobecome deserts.

236 CHAPTER 8 Ecosystems(l)Joe McDonald/DRK Photo, (r)Steve Solum/Bruce Coleman, Inc.


Grasslands Temperate and tropical regions thatreceive between 25 cm and 75 cm of precipitation eachyear and are dominated by climax communities ofgrasses are called grasslands. Most grasslands have a dry season, when little or no rain falls. This lack of moisture prevents the development of forests.Grasslands are found in many places around the world,and they have a variety of names. The prairies andplains of North America, the steppes of Asia, the savan-nas of Africa shown in Figure 14, and the pampas ofSouth America are types of grasslands.

Grasslands Life The most noticeable animals in grasslandbiomes are usually mammals that graze on the stems, leaves, andseeds of grass plants. Kangaroos graze in the grasslands ofAustralia. In Africa, communities of animals such as wilde-beests, impalas, and zebras thrive in the savannas.

Grasslands are perfect for growing many crops such aswheat, rye, oats, barley, and corn. Grasslands also are used toraise cattle and sheep. However, overgrazing can result in thedeath of grasses and the loss of valuable topsoil from erosion.Most farmers and ranchers take precautions to prevent the lossof valuable habitats and soil.

Figure 14 Animals such aszebras and wildebeests areadapted to life on the savannas in Africa.

SummaryMajor Biomes

• Tundra, sometimes called a cold desert, can be divided into two types: arctic andalpine.

• Taiga is the world’s largest biome. It is a coldforest region with long winters.

• Temperate regions have either a deciduousforest biome or a rain forest biome.

• Tropical rain forests are one of the most bio-logically diverse biomes.

• Humans have a huge impact on tropical rainforests.

• The driest biome is the desert. Desert organ-isms are adapted for extreme dryness andtemperatures.

• Grasslands provide food for wildlife, livestock,and humans.

Self Check1. Determine which two biomes are the driest.

2. Compare and contrast tundra organisms and desertorganisms.

3. Identify the biggest climatic difference between a tem-perate rain forest and a tropical rain forest.

4. Explain why the soil of tropical rain forests makes poorfarmland.

5. Think Critically If you climb a mountain in Arizona, youmight reach an area where the trees resemble the taigatrees in northern Canada. Why would a taiga forestexist in Arizona? SC.G.2.3.2

SC.G.2.3.2

SC.G.2.3.2

SC.G.2.3.2

6. Record Observations Animals have adaptations thathelp them survive in their environments. Make a list ofanimals that live in your area, and record the physical or behavioral adaptations that help them survive.

More Section Review fl6.msscience.comKevin Schafer


An ecological study includes observation andanalysis of organisms and the physical featuresof the environment.

Real-World ProblemHow do you study an ecosystem?

Goals■ Observe biotic factors and abiotic factors of

an ecosystem.■ Analyze the relationships among organisms

and their environments.

Materialsgraph paper field guidesbinoculars notebookthermometer compasspencil tape measuremagnifying lens

Safety PrecautionsComplete a safety worksheet before you begin.

Procedure1. Choose a portion of an ecosystem and deter-

mine the boundaries of your study area.

2. Using a tape measure and graph paper,make a map of your area. Determine thescale; for example, one square of graphpaper equals one square centimeter or onesquare meter of land. Determine north.

3. Observe the organisms in your study area.Use field guides to identify them. Use amagnifying lens to study small organismsand binoculars to study animals you can’tget near. Look for evidence (such as tracksor feathers) of organisms you do not see.

4. Record your observations in a table.

5. Measure and record the air temperature.

6. Visit your study area many times and at dif-ferent times of day for one week. At eachvisit, make the same measurements andrecord all observations. Note how the livingand nonliving parts of the ecosystem interact.

Conclude and Apply1. Predict what might happen if one or more

abiotic factors were changed suddenly.

2. Infer what might happen if one or morepopulations of plants or animals wereremoved from the area.

3. Infer how a new population of organismsmight affect your ecosystem.

4. Identify possible sources of error in your data.

Study1ng a Land Ecosystem


Environmental ObservationsDate

Time of day

Temperature

Organismsobserved

Comments

Make a classroom display of all datarecorded. Compare and contrast yourresults with those of your classmates andinvestigate differences further. For morehelp, refer to the Science Skill Handbook.

Benchmark—SC.G.2.3.2: The student knows that all biotic and abiotic factors areinterrelated and that if one factor is changed or removed, it impacts the availability ofother resources within the system; SC.H.1.3.1; SC.H.1.3.4; SC.H.1.3.7; SC.H.2.3.1

--InquiryInquiry

Do not write in this book.

SECTION 3 Aquatic Ecosystems 239

Freshwater EcosystemsIn a land environment, temperature and precipitation are

the most important factors that determine which species cansurvive. In aquatic environments, water temperature, theamount of sunlight present, and the amounts of dissolved oxy-gen and salt in the water are important. Earth’s freshwaterecosystems include flowing water such as rivers and streams andstanding water such as lakes, ponds, and wetlands.

Rivers and Streams Flowing freshwater environments vary from small, gurgling brooks to large, slow-moving rivers.Currents can quickly wash loose particles downstream, leaving a rocky or gravelly bottom. As the water tumbles and splashes,as shown in Figure 15, air from the atmosphere mixes in.Naturally fast-flowing streams usually have clearer water andhigher oxygen content than slow-flowing streams.

Most nutrients that support life in flowing-water ecosystemsare washed into the water from land. In areas where the watermovement slows, such as in the pools of streams or in largerivers, debris settles to the bottom. These environments tend tohave higher nutrient levels and more plant growth. They containorganisms that are not as well adapted to swiftly flowing water,such as freshwater mussels, minnows, and leeches.

Aquatic Ecosystems

■ Compare flowing freshwater andstanding freshwater ecosystems.

■ Identify and describe importantsaltwater ecosystems.

■ Identify problems that affectaquatic ecosystems.

All of the life processes in your bodydepend on water.

Figure 15 Streams like this oneare high in oxygen because of theswift, tumbling water. Determine where most nutrientsin streams come from.

Benchmarks—SC.D.2.3.1 (pp. 240, 241): The student understands that the quality of life is relevant topersonal experience; SC.D.2.3.2 Annually Assessed (pp. 240, 241): knows the positive and negativeconsequences of human action on the Earth’s systems; SC.G.2.3.3 (pp. 240, 241)

Also covers: SC.G.2.3.2 (pp. 240, 241), SC.G.2.3.4 Annually Assessed (pp. 240, 241), SC.H.1.3.4 AnnuallyAssessed (pp. 246–247), SC.H.1.3.5 Annually Assessed (pp. 240, 246–247), SC.H.1.3.6 (p. 244), SC.H.3.3.4(p. 248)

Review Vocabularyaquatic: growing or living inwater

New Vocabulary

• wetland • intertidal zone

• coral reef • estuary

W. Banaszewski/Visuals Unlimited


Figure 16 Lake Okeechobee isthe second largest natural lake inthe continental United States. It is730 square miles and holds morethan a trillion gallons of water.

Modeling RiverPollutionProcedure1. Complete a safety

worksheet.2. Fill several small aquari-

ums (or other clear con-tainers with water. Placeaquarium plants in thecontainers.

3. Have students put “pollu-tants” (such as salt, cook-ing oil, soap, etc) in thecontainers and observewhat takes place over thenext few weeks. One con-tainer should have no pollutants.

Analysis1. What might be the result

if you used stronger pollutants?

2. Identify the types of pollu-tion in streams and rivers.What is the source of thispollution?

3. List some steps that youcan take to limit the pollu-tion getting to waterways.

SC.D.2.3.1SC.G.2.3.4 Human Impact People use rivers and streams for many activ-

ities. Once regarded as a free place to dump sewage and otherpollutants, many people now recognize the damage this causes.Treating sewage and restricting pollutants have led to animprovement in the water quality in some rivers.

Lakes and Ponds When a low place in the land fills withrainwater, snowmelt, or water from an overflowing stream, a lakeor pond might form. Pond or lake water hardly moves. It containsmore plants than flowing-water environments contain.

Lakes are larger and deeper than ponds. Plants and micro-scopic organisms called plankton grow in the shallow, sunlitareas of a lake. Life at the shorelines and near the surface is verysimilar to that found in ponds. Colder temperatures and lowerlight levels in deep lake waters limit the types of organisms thatlive there. Figure 16 shows Lake Okeechobee, located in southcentral Florida. It is home to many organisms, including herons,egrets, bass, bluegill, white mussel, and red maple and baldcypress trees. A relatively shallow lake, its average depth is ninefeet, but reaches 17 feet deep. At its deepest areas there are fewplants or algae growing.

A pond is a small, shallow body of water. Because ponds areshallow, they are filled with animal and plant life. Sunlight usu-ally penetrates to the bottom. The warm, sunlit water promotesthe growth of plants and algae. In fact, many ponds are filledalmost completely with plant material, so the only clear, openwater is at the center. Because of the lush growth in pond envi-ronments, they tend to be high in nutrients.

CORBIS


Water Pollution Human activities can harm freshwater environments. Fertilizer-filled runoff from farms and lawns, aswell as sewage dumped into the water, can lead to excessivegrowth of algae and plants in lakes and ponds. The growth anddecay of these organisms reduces the oxygen level in the water,which makes it difficult for some organisms to survive. To pre-vent problems, sewage is treated before it is released. People also are being educated about problems associated with pollut-ing lakes and ponds. Fines and penalties are issued to peoplecaught polluting waterways. These controls have led to therecovery of many freshwater ecosystems.

Wetlands As the name suggests, wetlands, shown in Figure 17, are regions that are wet for all or most of a year. Theyare found in regions that lie between landmasses and water.Other names for wetlands include swamps, bogs, and fens. Somepeople refer to wetlands as biological supermarkets. They arefertile ecosystems, but only plants that are adapted to water-logged soil survive there. Wetland animals include beavers,muskrats, alligators, and the threatened bog turtle. Many migra-tory bird populations use wetlands as breeding grounds.

Where are wetlands found?

Wetlands once were considered to be useless, disease-riddenplaces. Many were drained and destroyed to make roads, farm-land, shopping centers, and housing developments. Onlyrecently have people begun to understand the importance ofwetlands. Products that come from wetlands, including fish,shellfish, cranberries, and plants, are valuable resources. Nowmany developers are restoring wetlands, and in most statesaccess to land through wetlands is prohibited.

Figure 17 Life in the FloridaEverglades was threatened due topollution, drought, and draining ofthe water. Conservation efforts arebeing made in an attempt to pre-serve this ecosystem.


SC.G.2.3.4 How are humanactivities altering wetlands ecosys-tems? Why is this harmful?

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James R. Fisher/DRK Photo


Saltwater EcosystemsAbout 95 percent of the water on the surface of Earth con-

tains high concentrations of various salts. The amount of dis-solved salts in water is called salinity. The average ocean salinityis about 35 g of salts per 1,000 g of water. Saltwater ecosystemsinclude oceans, seas, a few inland lakes such as the Great SaltLake in Utah, coastal inlets, and estuaries.

Convert Units

1. The thermometer outside your classroom reads 78°F. What is the temperature in degrees Celsius?

2. If lake water was 12°C in October and 23°C in May, what is the difference in degrees Fahrenheit? MA.B.2.3.2

MA.B.2.3.2

TEMPERATURE Organisms that live aroundhydrothermal vents in the ocean deal with tem-peratures that range from 1.7°C to 371°C. Youhave probably seen temperatures measured indegrees Celsius (°C) and degrees Fahrenheit(°F). Which one are you familiar with? If youknow the temperature in one system, you canconvert it to the other.

You have a Fahrenheit thermometer and measure the water temperature of a pond at 59°F. What is that temperature in degrees Celsius?

SolutionThis is what you know:

This is what you need tofind out:

This is the procedureyou need to use:

Check your answer:

water temperature in degrees Fahrenheit � 59°F

The water temperature in degrees Celsius.

● Solve the equation for degrees Celsius:(°C � 1.8) � 32 � °F°C � (°F � 32)/1.8

● Substitute the known value:°C = (59°F – 32)/1.8 = 15°C

● Water temperature that is 59°F is 15°C.

Substitute the Celsius temperature back into the originalequation. You should get 59.

For more practice, visit fl6.msscience.com

Math Practice

D. Foster/WHOI/Visuals Unlimited



Open Oceans Life abounds in the open ocean. Scientistsdivide the ocean into different life zones, based on the depth towhich sunlight penetrates the water. The lighted zone of theocean is the upper 200 m or so. It is the home of the planktonthat make up the foundation of the food chain in the openocean. Below about 200 m is the dark zone of the ocean.Animals living in this region feed on material that floats downfrom the lighted zone, or they feed on each other. A few organ-isms are able to produce their own food.

Coral Reefs One of the most diverse ecosystems in the worldis the coral reef. Coral reefs are formed over long periods of timefrom the calcium carbonate exoskeletons secreted by animalscalled corals. When corals die, their exoskeletons remain. Overtime, the exoskeleton deposits form reefs such as Molasses Reefoff the coast of the Florida Keys, shown in Figure 18.

Reefs do not adapt well to long-term stress. Runoff fromfields, sewage, and increased sedimentation from cleared landharm reef ecosystems. Organizations like the EnvironmentalProtection Agency have developed management plans to protectthe diversity of coral reefs. These plans treat a coral reef as a sys-tem that includes all the areas that surround the reef. Keepingthe areas around reefs healthy will result in a healthy environ-ment for the coral reef ecosystem.

Figure 18 The darker areas inthis photo are part of MolassesReef, the third largest reef in theworld, located off the coast of KeyLargo, Florida. Reefs are habitatsfor colorful fish and a large varietyof other organisms.

LA.B.2.3.4

--InquiryInquiry

Topic: Coral ReefsVisit fl6.msscience.com for Weblinks to information about coralreef ecosystems.

Activity Construct a diorama ofa coral reef. Include as many differ-ent kinds of organisms as you canfor a coral reef ecosystem.

(l)Stephen Frink/CORBIS, (r)The Image Bank/Getty Images



Seashores All of Earth’s landmasses arebordered by ocean water. The shallow

waters along the world’s coastlines contain a variety of saltwaterecosystems, all of which are influenced by the tides and by theaction of waves. The gravitational pull of the Moon, and to alesser extent, the Sun, on Earth causes the tides to rise and falleach day. The height of the tides varies according to the phasesof the Moon, the season, and the slope of the shoreline. Theintertidal zone is the portion of the shoreline that is coveredwith water at high tide and exposed to the air during low tide.Organisms that live in the intertidal zone, such as those inFigure 19, must be adapted to dramatic changes in temperature,moisture, and salinity and must be able to withstand the force ofwave action.

Estuaries Almost every river on Earth eventually flows intoan ocean. The area where a river meets an ocean and contains amixture of freshwater and salt water is called an estuary(ES chuh wer ee). Other names for estuaries include bays,lagoons, harbors, inlets, and sounds. They are located nearcoastlines and border the land. Salinity in estuaries changes withthe amount of freshwater brought in by rivers and streams, andwith the amount of salt water pushed inland by the ocean tides.

Estuaries, shown in Figure 20, are extremely fertile, pro-ductive environments because freshwater streams bring intons of nutrients washed from inland soils. Therefore, nutrientlevels in estuaries are higher than in freshwater ecosystems orother saltwater ecosystems.

Figure 19 As the tiderecedes, small pools ofseawater are leftbehind. These poolscontain a varietyof organismssuch as sea starsand periwinkles.

Sea star

Periwinkles

Environmental AuthorRachel Carson (1907–1964)was a scientist that turnedher knowledge and love of the environment intoarticles and books. After 15 years as an editor forthe U.S. Fish and WildlifeService, she resigned anddevoted her time to writ-ing. She probably is knownbest for her book SilentSpring, in which she warnedabout the long-term effectsof the misuse of pesticides.In your Science Journal,compile a list of otherauthors who write aboutenvironmental issues.

(tl)Dwight Kuhn, (tr)Glenn Oliver/Visuals Unlimited, (b)Stephen J. Krasemann/DRK Photo


Estuary Life Organisms found in estuaries include manyspecies of algae, salt-tolerant grasses, shrimp, crabs, clams, oys-ters, snails, worms, and fish. Estuaries also serve as importantnurseries for many species of ocean fish. Estuaries provide muchof the seafood consumed by humans.

Why are estuaries more fertile than otheraquatic ecosystems?

Figure 20 The Crystal River estuary is rich in resources. Fish andshrimp are harvested by commercialfishing boats. Describe what other resources can befound in estuaries.

SummaryFreshwater Ecosystems

• Temperature, light, salt, and dissolved oxygenare important factors.

• Rivers, streams, lakes, ponds, and wetlandsare freshwater ecosystems.

• Human activities, such as too much lawn fer-tilizer, can pollute aquatic ecosystems.

Saltwater Ecosystems

• About 95 percent of Earth’s water containsdissolved salts.

• Saltwater ecosystems include open oceans,coral reefs, seashores, and estuaries.

• Organisms that live on seashores have adap-tations that enable them to survive dramaticchanges in temperature, moisture, and salinity.

• Estuaries serve as nursery areas for manyspecies of ocean fish.

Self Check1. Identify the similarities and differences between a lake

and a stream.

2. Compare and contrast the dark zone of the ocean withthe forest floor of a tropical rain forest. What living ornonliving factors affect these areas?

3. Explain why fewer plants are at the bottom of deep lakes.

4. Infer what adaptations are necessary for organismsthat live in the intertidal zone.

5. Think Critically Would you expect a fast movingmountain stream or the Mississippi River to have moredissolved oxygen? Explain.

SC.G.1.3.2

SC.G.2.3.2

6. Communicate Wetlands trap and slowly release rain,snow, and groundwater. Describe in your ScienceJournal what might happen to a town located on a floodplain if nearby wetlands are destroyed.

More Section Review fl6.msscience.com

SC.G.2.3.2

(l)David Muench/CORBIS, (r)Jerry Sarapochiello/Bruce Coleman, Inc.


Use the InternetUse the Internet

Real-World ProblemWetlands, such as the one shown below, are an important part of the environment. These fertile ecosystems support unique plants and animals that can survive only in wetland conditions. The more you understand the importance of wetlands, the more you can do to preserve and protect them. Why are wetlands an important part of the ecosystem?

Goals■ Identify wetland

regions in the UnitedStates.

■ Describe the signifi-cance of the wetlandecosystem.

■ Identify plant and ani-mal species native to awetland region.

■ Identify strategies forsupporting the preser-vation of wetlands.

Data SourceInternet LabVisit fl6.msscience.com formore information aboutwetland environmentsand for data collectedby other students.

Explorihg Wetlands


Benchmark—SC.D.2.3.2: The student knows the positive and negative consequences of human action on the Earth’s systems; SC.H.1.3.4: The student knows that accuraterecord keeping, openness, and replication are essential to maintaining an investigator’scredibility with other scientists and society; SC.H.1.3.5: The student knows that a changein one or more variables may alter the outcome of an investigation.

(t)Dwight Kuhn, (b)John Gerlach/DRK Photo


Find this lab using the link below. Post yourdata in the table provided. Review otherstudents’ data to learn about other wetlandenvironments in the United States.

Make a Plan1. Determine where some major wetlands are located in the United States.

2. Identify one wetland area to study in depth. Where is it located? Is it classifiedas a marsh, bog, or something else?

3. Explain the role this ecosystem plays in the overall ecology of the area.

4. Research information about the plants and animals that live in the wetlandenvironment you are researching.

5. Investigate what laws protect the wetland you are studying.

Follow Your Plan1. Make sure your teacher approves your plan before you start.

2. Perform the investigation.

3. Post your data at the link shown below.

Analyze Your Data1. Describe the wetland area you have researched. What region of the United

States is it located in? What other ecological factors are found in that region?

2. Outline the laws protecting the wetland you are investigating. How long havethe laws been in place?

3. List the plants and animals native to the wetland area you are researching. Arethose plants and animals found in other parts of the region or the UnitedStates? What adaptations do the plants and animals have that help them sur-vive in a wetland environment?

Conclude and Apply1. Infer Are all wetlands the same?

2. Determine what the ecological significance of the wetland area that you studied for that region of the country is.

3. Draw Conclusions Why should wetland environments be protected?

4. Summarize what people can do to support the continued preservation of wetland environments in the United States.

LAB 247

Internet Labfl6.msscience.com

Fritz Polking/Bruce Coleman, Inc.


SCIENCEANDSocietySCIENCE ISSUES

THAT AFFECTYOU!

When you wash your hands or flush thetoilet, do you think about where thewastewater goes? In most places, it

eventually ends up being processed in a tradi-tional sewage-treatment facility. But some placesare experimenting with a new method thatprocesses wastewater by creating wetlands.Wetlands are home to filtering plants, such ascattails, and sewage-eating bacteria.

In 1996, school officials at the CorralesElementary School in Albuquerque, New Mexico,faced a big problem. The old wastewater-treat-ment system had failed. Replacing it was goingto cost a lot of money. Instead of constructing anew sewage-treatment plant, school officialsdecided to create a natural wetlands system. Thewetlands system could do the job less expen-sively, while protecting the environment.

Today, this wetlands efficiently converts pol-luted water into cleaner water that’s good for theenvironment. U.S. government officials are mon-itoring this alternative sewage-treatment systemto see if it is successful. So far, so good!

Wetlands filter water through the actions ofthe plants and microorganisms that live there.When plants absorb water into their roots, somealso take up pollutants. The plants convert thepollutants to forms that are not dangerous. Atthe same time, bacteria and other microorgan-isms are filtering water as they feed. Watermoves slowly through wetlands, so the organismshave plenty of time to do their work. Wetlandsbuilt by people to filter small amounts of pollu-tants are called “constructed wetlands”. In manyplaces, constructed wetlands are better at clean-ing wastewater than sewers or septic systems.

Creating Wetlands toPurify Wastewater

1 2 3

Students enjoypure water fromthe Corraleswetlands afterit is filtered.

Water irisesthrived in thewetlands, lessthan a yearafter planting.

Pebbles were added to theCorrales wetlands to helpwith drainage.

Visit and Observe Visit a wetlands and create a field journalof your observations. Draw the plants and animals you see. Use afield guide to help identify the wildlife. If you don’t live near awetlands, use resources to research wetlands environments.

For more information, visitfl6.msscience.com

courtesy Albuquerque Public Schools


How Ecosystems Change

1. Ecological succession is the gradual changefrom one plant community to another.

2. Primary succession begins in a place whereno plants were before.

3. Secondary succession begins in a place thathas soil and was once the home of livingorganisms.

4. A climax community has reached a stablestage of ecological succession.

Biomes

1. Temperature and precipitation helpdetermine the climate of a region.

2. Large geographic areas with similar climaxcommunities are called biomes.

3. Earth’s land biomes include tundra, taiga,temperate deciduous forest, temperate rainforest, tropical rain forest, grassland, anddesert.

Aquatic Ecosystems

1. Freshwater ecosystems include streams,rivers, lakes, ponds, and wetlands.

2. Wetlands are areas that are covered withwater most of the year. They are found inregions that lie between land-masses andwater.

3. Saltwater ecosystems include estuaries, sea-shores, coral reefs, a few inland lakes, andthe deep ocean.

4. Estuaries are fertile transitional zonesbetween freshwater and saltwater environments.

CHAPTER STUDY GUIDE 249

Copy and complete this concept map about land biomes.

Tropical rainforest

Tundra

Non-forest

such as such as such as

can be can be

such as such as such as such as

Biomes

Interactive Tutor fl6.msscience.com(l)James P. Rowan/DRK Photo, (r)John Shaw/Tom Stack & Assoc.


Answer with the correct vocabulary word orwords.

1. the normal changes in the types of speciesthat live in communities

2. a group of organisms found in a stable stageof succession

3. place where deciduous trees are dominant

4. the average temperature is between 9°C and12°C

5. the most biologically diverse biomes in theworld

6. an area where freshwater meets the ocean

Choose the word or phrase that best answers the question.

7. What are tundra and desert examples of?A) ecosystems C) habitatsB) biomes D) communities

8. What is a biome that receives less than 25 cm of rain called?A) desert C) coral reefB) tundra D) grassland

9. Where would organisms that are adapted tolive in slightly salty water be found?A) lake C) open oceanB) estuary D) intertidal zone

10. Which biome contains mostly frozen soilcalled permafrost? A) taigaB) temperate rain forestC) tundraD) temperate deciduous forest

11. A new island is formed from a volcaniceruption. Which species probably wouldbe the first to grow and survive?A) palm trees C) grassesB) lichens D) ferns

12. What would the changes in communitiesthat take place on a recently formed vol-canic island best be described as?A) primary successionB) secondary successionC) tertiary successionD) magma

13. What is the stable end stage of succession?A) pioneer speciesB) climax communityC) limiting factorD) permafrost

Use the illustration below to answer question 14.

14. Which area of the U.S. had the highestobserved fire danger on June 20, 2003? A) northeast C) northwestB) southeast D) southwest

250 CHAPTER REVIEW

biome p. 230climax community p. 229coral reef p. 243desert p. 236estuary p. 244grassland p. 237intertidal zone p. 244pioneer species p. 226

succession p. 226taiga p. 232temperate deciduous

forest p. 233temperate rain forest p. 233tropical rain forest p. 234tundra p. 231wetland p. 241

Very highExtremeWater

ModerateHigh

Low

LEGEND

Observed Fire Danger Class—June, 2003

WFAS-MAPS Graphics National Interagency Fire Center Boise, ID

Vocabulary PuzzleMaker fl6.msscience.com

SC.G.2.3.2


15. Explain In most cases, would a soil sample from a temperate deciduous forest bemore or less nutrient-rich than a soil sam-ple from a tropical rain forest?

16. Explain why some plant seeds need fire inorder to germinate. How does this givethese plants an advantage in secondarysuccession?

17. Determine A grassy meadow borders abeech-maple forest. Is one of these ecosys-tems undergoing succession? Why?

18. Infer why tundra plants are usually small.

19. Make and Use a Table Copy and complete thefollowing table about aquatic ecosystems.Include the terms: intertidal zone, lake,pond, coral reef, open ocean, river, estuary,and stream.

20. Recognize Cause and Effect Wildfires like theone in Yellowstone National Park in 1988,cause many changes to the land. Determinethe effect of a fire on an area that hasreached its climax community.

21. Oral Presentation Research a biome not inthis chapter. Find out about its climate andlocation, and which organisms live there.Present this information to your class.

CHAPTER REVIEW 251

Use the table below to answer question 22.

Rainfall Amounts

Biome Average

Precipitation/Year (cm)

Taiga 50

Temperate rain forest 200

Tropical rain forest 400

Desert 25

Temperate deciduous forest 150

Tundra 25

Aquatic Ecosystems

Saltwater Freshwater

22. Biome Precipitation How many times moreprecipitation does the tropical rain forest biomereceive than the taiga or desert?

Use the graph below to answer question 23.

23. Biome Temperatures According to the graph,which biome has the greatest and which biomehas the least variation in temperature through-out the year? Estimate the difference betweenthe two. MA.E.1.3.1SC.G.2.3.2

Average Temperature Range of Biomes

0�

10�

-10�

-20�

-30�

20�

30�

Biome

Tem

per

atu

re ra

ng

e (�

C)

Tund

ra

Taig

a

Des

ert

Gras

slan

d

Tem

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ecid

uous

fore

st

Trop

ical

rain

fore

st

Tem

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in fo

rest

SC.G.2.3.2

Chapter Review fl6.msscience.com

SC.G.2.3.2

SC.G.2.3.2

Do not write in this book.


252 FLORIDA

a What biome is found primarily near theArctic Circle?

A. grassland

B. taiga

C. temperate deciduous forest

D. tropical rain forest

s Over time the number and size of treessurrounding a small pond have increased,reducing the amount of sunlight the pondreceives. What effect will the increasedamount of shade most likely have on thepond?

F. The volume of water in the pond willdecrease.

G. The population of plants in the pondwill decrease.

H. The amount of algae growing in thepond will increase.

I. The average temperature of the waterin the pond will increase.

Equator

Tropic of Capricorn

Antarctic Circle

Tropic of Cancer

Arctic Circle

B

C

D A

d A plant called saxifrage grows near theground and can absorb heat from the groundduring summer. It is protected from harshwinter weather by a layer of snow. Based onthis information, which best explains whysaxifrage is well-adapted to the tundra?

A. The saxifrage has adapted to survive the extreme cold in the tundra.

B. The saxifrage has adapted to use thenutrient-rich soil in the tundra.

C. The saxifrage has adapted to be polli-nated by the many types of birds intundra.

D. The saxifrage has adapted to use themoderate amount of precipitation in the tundra.

f Look at the diagram below. What is mostlikely to happen next in this community?

F. The bare soil will remain lifeless formany years.

G. Lichens and erosion will slowly breakdown rocks to form new soil.

H. A variety of plants will begin to growfrom seeds already in the soil.

I. Only small plants such as mosses andferns will have enough nutrients to grow.

FloridaFloridachapter chapter

The assessed Florida Benchmark appears above each question.Record your answers on the answer sheet provided by your teacher or on a sheet of paper.

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SC.H.2.3.1

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SC.G.1.3.2

SC.G.2.3.3

FCAT PRACTICE 253FCAT Practice fl6.msscience.com

g How might grassland most likely beaffected if livestock overgraze it?

A. Erosion of topsoil will increase as thegrasses die.

B. The grasses will be replaced by a tem-perate forest.

C. The length of the dry season in thegrassland will decrease.

D. Ranchers will be able to raise moreanimals on the grassland.

h The table below shows the average yearlyrainfall in four desert cities.

Based on the information in the table,how many years would it take for Iquiqueto receive the amount of rainfall thatAgadez receives in a single year?

CityAverage Yearly Rainfall

(mm)

Agadez, Niger 143

Aleppo, Syria 329

Carson City, United States 285

Iquique, Chile 2

j Explain why primary succession takeslonger than secondary succession.

k The diagram below shows a farm and asewage plant located near a lake.

PART A Based on the diagram, describe the effects that pollutantsreleased from the farm and thesewage plant might be havingon the organisms that live inthe lake.

PART B Explain how these effects couldbe prevented.

FarmSewage

plant

READINQUIREEXPLAIN

READINQUIREEXPLAIN

Show All Your Work For “Read, Inquire, Explain” questions,show all of your work and any calculations on your answersheet.

FCAT PracticeFCAT Practice FC

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