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Section 1 in Objectives Describe how energy is transferred from the Ecosystems to producers and then to consumers.

Organisms need energy to survive, grow, and reproduce. Different organisms Describe one way in which get energy from different sources, but the ultimate source of energy for almost all consumers depend on producers. organisms on Earth is the sun. Identify two types of consumers.

Explain how energy transfer in a Life Depends on the Sun is more complex than Energy from the sun enters an when organisms use sunlight energy transfer in a . to make sugar in a process called . During photosynthesis, , , and some bacteria capture light energy from the sun and Explain why an energy pyramid use it to convert and water into sugar and , as is a representation of trophic shown in Figure 1.1. The result of photosynthesis is the production of levels. sugar molecules known as . Carbohydrates are energy- rich molecules that organisms use to move, grow, and reproduce. As organisms consume other plants or , energy is transfered from Key Terms one to another. photosynthesis producer Plants, such as sunflowers, produce carbohydrates in their leaves. When an eats a , or the fruit or seeds of a plant, some energy is transferred from the plant to the animal. When animals are consumed by other organisms, energy is again transferred. food chain Figure 1.1 food web Photosynthesis During photosynthesis, plants use light energy from the sun to make carbohydrates. The chloroplasts in the leaves and stems of these sunflowers contain a green chemical called chlorophyll. Chloro­phyll absorbs the light energy needed for photosynthesis.

solar energy ©SPL/Photo Researchers, Inc. ©SPL/Photo Researchers,

Chapter 5: How Ecosystems Work 117 printcode=a DO NOT EDIT--Changes mustbemadethrough “File info” 118 use energyfromhydrogen sulfide to make their own food. bacteria thatliveinsidethemtosurvive. The bacteria(right) Deep- Ecosystem consumers get energy from thesun? consumers getenergy Relate Figure 1.2 Figure 1.3 Transfer ofEnergy energy byeatingotherorganisms. Animals suchastherabbitandcoyotegettheir clover shownabovegetenergyfromthesun. depend onthesunforenergy. Plantslikethe Che How doproducersand How c Unit 2: k f o r Understanding

Almost allorganisms

These tubewormsdependon the sun by eating producers orotherconsumers. light energy directly from thesun. Consumers energy indirectly get from feeders. Producers, such asplants, most algae, bacteria, andsome absorb eating otherorganisms. Consumers are called also , orother- energy from thesun. The clover isa rabbit andthecoyote are Producersits ownfood. are called also , orself-feeders. The As shown the rabbit, oftheenergy istransferred some from therabbit to thecoyote. hydrates produced intheplant through photosynthesis. Ifacoyote eats arabbitWhen eats aclover plant, therabbit energy from gets thecarbo- From Producers toConsumers Figure 1.2 deep-ocean communities exist in total darkness, where where darkness, total in exist communities deep-ocean floor. These ocean the in vents thermal near living barnacles and , crabs, clams, worms, of communities large found have scientists But life. much find to expect not might you sunlight, no is there where ocean the of depths the In An Exception:Deep-OceanEcosystems organisms and thus support a thriving ecosystem. thriving a support thus and organisms called process a in sulfide chemical the from obtained energy using carbohydrates produce bacteria -metabolizing These vents. thermal the from escapes that water hot the in present is sulfide Hydrogen food. own their make to sulfide hydrogen use bacteria These pictured in in pictured those as such bacteria, from comes source Another die. organisms as above from down drifts that matter organic from comes energy of source One energy? their get organisms these do where occur. So cannot photosynthesis , theclover, rabbit, andcoyote ultimately their get Figure 1.3 Figure consumers . The bacteria are eaten by other other by eaten are bacteria The . , that live in some of these organisms. organisms. these of some in live that , producer , organisms that theirenergy by get , anorganism that makes underwater ­underwater

(cl) ©BIOS; (tl) ©Comstock/Getty Images; (tr) ©Comstock/Getty Images; (c) ©William Leaman/Alamy Images; (bc) ©SPL/Photo Researchers, Inc.; (bl) ©Ron & Valerie Taylor/Bruce Coleman, Inc./Photoshot Connect to MATH

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What Eats What Connect to MATH Organisms can be classified by the source of their energy, as shown in A Meal Fit for a Grizzly Bear Figure 1.4. Consumers that eat only plants are called . Rabbits Grizzly bears are that can are herbivores as are cows, sheep, deer, grasshoppers,­ and many other eat up to 15 percent of their body animals. Consumers, such as lions and hawks, that eat only other ani- weight per day when eating salmon mals are called . You already know that humans are consum- and up to 33 percent of their body ers, but what kind of consumers are we? Because humans can eat both weight when eating fruits and other plants and animals, we are called omnivores. Bears, pigs, and cock- . How many pounds of roaches are other examples of omnivores. salmon can a 200 lb grizzly bear eat Consumers that get their food by breaking down organic matter from in one day? How many pounds of dead organisms and are called . Some bacteria and fungi fruits and other vegetation can the are decomposers. The decomposers allow the nutrients in the rotting same bear eat in one day? material to return to the , water, and air.

figure 1.4 What Eats What in an Ecosystem

Energy source Examples

Producer makes its own food using light energy grasses, , cactuses, flowering plants, , algae, and (photosynthesis) or chemical sources some bacteria (chemosynthesis) Consumer gets energy by eating producers or other consumers mice, starfish, elephants, turtles, humans, and ants Types of Consumers in an Ecosystem

Energy source Examples

Herbivore producers cows, sheep, deer, and grasshoppers other consumers lions, hawks, snakes, spiders, sharks, and whales both producers and consumers bears, pigs, gorillas, rats, raccoons, cockroaches, some insects, and humans Decomposer breaks down organic matter from dead organisms fungi and bacteria

Consumers Bears, such as this grizzly bear, are omnivores. Grizzly bears eat other consumers, such as salmon, but they also eat various plants. ©Roberta Olenick/All Canada Photos/Alamy Images

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Cellular Respiration: Burning the Fuel So far, you have learned how organisms get energy. But how do they use HMDScience.com the energy they get? To understand the process, use yourself as an example. Photosynthesis and Cellular Suppose you have just eaten a large meal. The food you ate contains a lot Respiration of energy. Your body gets the energy out of the food by using the oxygen you breathe to break down the food. By breaking down the food, your body obtains the energy stored in the food. The process of breaking down carbohydrates to yield energy is called cellular respiration, which occurs inside the cells of organisms. This process is different from breathing, another form of respiration. During cellular respiration, cells absorb oxygen and use it to release energy from food. As you can see in Figure 1.5, the chemical equation for cellular respi- ration is essentially the reverse of the equation for photosynthesis. During cellular respiration, sugar molecules are broken down in the presence of oxygen, yielding energy. Water and carbon dioxide are waste products. Figure 1.5

Cellular Respiration Through cellular respiration, cells use sugar and oxygen to produce carbon dioxide, water, and energy.

CASESTUDY DDT in an Aquatic Food Chain In the 1950s and 1960s, something strange was happening in the estuaries near Long Island Sound, near New York and Connecticut. Birds of prey, such as ospreys and eagles, that fed on fish in the estuaries had high concentrations of the pesticide DDT in their bodies. But when the water in the estuaries was tested, it had low concentrations of DDT. What accounted for the high levels of DDT in the birds? Poisons that dissolve in fat, such as DDT, can become more concentrated as they move up a food chain in a process called biological magnification. When the pesticide enters the water, algae and bacteria take in the poison. When fish eat the algae and bacteria, the poison dissolves into the fat of the fish rather than diffusing back into the water. Most of the poison remains in an animal’s body once is eaten. Each time a bird feeds on a fish, the bird accumulates more DDT in its fatty tissues. In some estuaries on Long Island Sound, DDT concentrations in fatty tissues of organisms were magnified almost 10 million times from the bottom to the top of the food chain. A high concentration of DDT decreases the thickness and the strength of eggshells of many Large concentrations of DDT may kill an organism, weaken its birds of prey. immune system, cause deformities, or impair its ability to reproduce. ©Harry Engels/Photo Researchers, Inc. ©Harry Engels/Photo Researchers,

120 Unit 2: Ecology Connect to CHEMISTRY

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You use a part of the energy you obtain through cellular respiration Connect to CHEMISTRY to carry out your daily activities. Every time you walk, breathe, sleep, Chemical Equations think, or play a sport, you use energy. The energy you obtain is also used A chemical equation is a shorthand to make more body tissues and to fight diseases so that you grow and stay description of a chemical reaction healthy. Excess energy you obtain is stored as fat or sugar. All living things using chemical formulas and symbols. use cellular respiration to get the energy they need from food molecules. The starting materials in a reaction are Even organisms that make their own food through photosynthesis use called reactants, and the substances cellular respiration to obtain energy from the carbohydrates they pro- formed from a reaction are called duce. products. The number of atoms of each element in the reactants equals the number of atoms of those Energy Transfer elements in the products to make a Each time one organism eats another organism, a transfer of energy balanced equation. occurs. In order to understand and manage ecosystems, environmental scientists must be able to trace the flow of energy through ecosystems. They also need to know how much energy flows to different parts of the ecosystem. By knowing how energy flows within an ecosystem and how much enery different species use, scientists can find out how organisms depend on one another to survive.

CASESTUDY

Poisons such as DDT have the greatest affect on organisms at the top of food chains. For example, the osprey shown here would have a greater concentration of DDT in its body than the perch it’s about to eat.

Critical Thinking DDT can also weaken the shells of bird eggs. When eggs in large quantities to eliminate mosquitoes that carry the break too soon, bird embryos die. There­fore, the effects disease malaria. of these chemicals cause a huge drop in the population of carnivorous bird species. Critical Thinking The U.S. government recognized DDT as an 1. Analyzing Processes DDT does not dissolve environmental contaminant and in 1972 banned its readily in water. If it did, how would the sale except in emergencies. The aquatic food chains accumulation of the pesticide in organisms be immediately started to recover, and the populations of affected? ospreys and eagles started to grow. 2. Evaluate Even though DDT is harmful to Food chains are still not free of DDT. DDT is still legal in the environment, why is it still used in some some countries where, for example, it is sometimes used countries? ©Fritz Polking/Bruce Coleman, Inc./Photoshot Coleman, Polking/Bruce ©Fritz

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Figure 1.6 Food Chains and Food Webs A food chain is the path in which energy is transferred from one organism Food Chain Energy is transferred from one organism to another in a food to the next as each organism eats another organism. Figure 1.6 shows a chain. Algae are the producers in this typical food chain in an ocean ecosystem. Algae are eaten by krill, which ocean food chain. are eaten by fish, such as the Antarctic toothfish. These fish, in turn, are eaten by leopard seals, which are eaten by killer whales. In natural ecosystems, energy does not flow in simple chains. Most organisms eat more than one kind of food, and many species are eaten by more than one predator. A food web, such as the one shown in Figure 1.7, is a better depiction of energy flow in ecosystems. A food web includes more organisms and shows the feeding relationships between organisms that are possible in an ecosystem. Killer whale Trophic Levels Each step through which energy is transferred in a food chain is known as a trophic level. In Figure 1.6, the algae are in the bottom trophic level Leopard seal (trophic level 1), the krill are in the next level (trophic level 2), and so on. Each time energy is transferred from one organism to another, less energy is available to organisms at the next trophic level. Some of the energy is lost as heat. Organisms use much of the remaining energy to carry out life

Antarctic tooth sh functions, such as cellular respiration and moving.

Figure 1.7 Krill Food Web This food web shows how the largest organisms depend on the smallest organisms in an ocean ecosystem. Killer whale

Crabeater seal Algae Elephant seal

Leopard seal Antarctic tooth sh

Adélie Squid penguin

Krill

Small animals Algae and one-celled organisms

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Because organisms require energy for all of their Figure 1.8 life functions, only about 10 percent of the energy from one trophic level is stored in the bodies of organisms at Energy Pyramid This energy pyramid shows how energy is lost from one trophic level to the next. The grass at the bottom level the next level. This 10 percent that is stored is all that stores 1,000 times more energy than the hawk at the top level. is available to the next trophic level when one organism consumes another organism. Tertiary consumers

Energy Pyramids

One way to visualize the loss of energy from one Secondary trophic level to the next is to draw an energy pyra- consumers mid like the one shown in Figure 1.8. Each level in Primary the energy pyramid represents one trophic level. consumers Producers form the base of the pyramid, the low- est trophic level, which contains the most energy. Herbivores make up the second level. Carnivores Energy lost that feed on herbivores form the next level, and Producers carnivores that feed on other carnivores make up the top level. The higher the trophic level the less stored energy there is to be passed on.

How Energy Loss Affects an Ecosystem The decreased amount of energy at each trophic level affects the organiza-

tion of an ecosystem. First, because so much energy is lost at each level, HMDScience.com there are fewer organisms at the higher trophic levels. For example, zebras and other herbivores vastly outnumber lions and other predators on the Ecosystems and Energy Pyramids African savanna. In this example, there simply are not enough herbivores to support more carnivores. EV_CNLESE904016_669a Second, the loss of energy between trophic levels limits the number of trophic levels in an ecosystem. Ecosystems rarely have more than four or five trophic levels because the eco­system does not have enough energy left to support higher levels. For example, a lion typically needs up to 250 km2 of land to hunt for food. Killer whales may have to move across hundreds or thousands of kilometers during their . The organisms that feed on organisms at the top trophic level are usually small, such as parasitic worms and fleas that require a very small amount of energy.

Section 1 Formative Assessment

Reviewing Main Ideas Critical Thinking 1. Describe how energy is transferred from one 5. Interpreting Graphics Explain the feeding organism to another. relationships of the crabeater seal in Figure 1.7. 2. Describe the role of producers in an ecosystem. 6. Inferring Relationships Could more people be supported by 20 acres of land if they ate 3. Explain the difference between an only plants instead of both plants and animals? and an omnivore. Explain your answer. 4. Compare energy transfer in a food chain to energy transfer in a food web.

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Section 2 Objectives The Cycling of Matter Describe the short-term and long-term process of the . Everything is made of matter. Matter is anything that has mass and takes up space. Organisms need both energy and matter to live, grow, and reproduce. Energy and Identify one way that humans matter are constantly moving through ecosystems. The law of conservation of are affecting the carbon cycle. energy states that energy cannot be created or destroyed. Energy changes forms. For example, producers change light energy to chemical energy in sugars. The List the three stages of the law of conservation of matter states that matter cannot be created or destroyed. nitrogen cycle. Instead, matter moves through the environment in different forms. Ecosystems do not have clear boundaries, so some energy and matter can leave them. In this Describe the role that nitrogen- section, you will read about three cycles by which matter and energy are reused— fixing bacteria play in the the carbon cycle, the nitrogen cycle, and the phosphorus cycle. nitrogen cycle.

Explain how the excess use of The Carbon Cycle fertilizer can affect the nitrogen Carbon is an essential component of , fats, and carbohydrates, and phosphorus cycles. which make up all organisms. The carbon cycle is a process by which carbon is cycled between the atmosphere, land, water, and organisms. Key Terms As shown in Figure 2.1, carbon enters a short-term cycle in an ecosystem when producers, such as plants, convert carbon dioxide in the atmo- carbon cycle sphere into carbohydrates during photosynthesis. When consumers eat nitrogen-fixing bacteria producers, the consumers obtain carbon from the carbohydrates. As nitrogen cycle the consumers break down food during ­cellular respiration, some of the phosphorus cycle carbon is released back into the atmosphere as carbon dioxide. Producers also release carbon dioxide during cellular respiration. Some carbon enters a long-term cycle. For example, carbon may be converted into carbonates, which make up the hard parts of bones and shells. Bones and shells do not break down easily. So, over millions of years, carbonate deposits have produced huge formations of limestone rocks. Limestone is one of the largest carbon sinks, or carbon reservoirs, on Earth.

Figure 2.1 The Carbon Cycle Atmospheric carbon dioxide, CO2

RESPIRATION COMBUSTION RESPIRATION PHOTOSYNTHESIS

EROSION Natural gas

CO2 dissolved in water Plant and animal Coal Oil remains Limestone Marine remains Natural gas Oil

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QUICKLAB Some carbohydrates in organisms are converted into fats, oils, and QUICKLAB other molecules that store energy. The carbon in these molecules may be released into the soil or air after an organism dies. These molecules can Make Every Breath Count form deposits of coal, oil, and natural gas underground. The deposits are Procedure 1. Pour 100 mL of water from a known as fossil fuels. Fossil fuels are made up of carbon compounds from graduated cylinder into a 250 the bodies of organisms that died millions of years ago. mL beaker. Add several drops of bromthymol blue to the beaker of How Humans Affect the Carbon Cycle water. Make sure you add enough to make the solution a dark blue When we burn fossil fuels, carbon is released into the atmosphere as color. carbon dioxide. Cars, factories, and power plants rely on fossil fuels to 2. Exhale through a straw into the operate. In the year 2009, vehicles, such as the truck in Figure 2.2, were the solution until the solution turns source of just over one-third of all carbon dioxide emitted in the United yellow. (CAUTION: Be sure not to States. Each year, about 8.4 billion metric tons of carbon dioxide are re- inhale or ingest the solution.) leased into the atmosphere by the burning, or combustion, of fossil fuels 3. Pour the yellow solution into a and the natural burning of wood in forest fires. About half of this carbon large test tube that contains a dioxide remains in the atmosphere. As a result, the amount of carbon sprig of Elodea. dioxide in the atmosphere has steadily increased. 4. Stopper the test tube, and place it Increased levels of carbon dioxide in the atmosphere are the ma- in a sunny location. jor contributor to climate change. Carbon dioxide is a greenhouse gas. 5. Observe the solution in the test Greenhouse gases, including water vapor and other gases absorb and re- tube after 15 minutes. radiate infrared energy, warming Earth. Plants absorb some of the carbon Analysis dioxide, but scientists estimate that, each year, over a billion metric tons 1. What do you think happened to the of carbon dioxide dissolves into the ocean, a . The increase in carbon dioxide that you exhaled carbon dioxide can lower the pH, which can impact marine organisms. into the solution? 2. What effect do plants, such as the Elodea, have on the Figure 2.2 carbon cycle? Carbon Emissions This truck releases carbon into the atmosphere when it burns fuel to operate.

critical thinking Relate Explain how the carbon emission from this truck enters and exits producers, such as the trees shown in this photo. ©Ted Spiegel/Corbis ©Ted

Chapter 5 125 printcode=a DO NOT EDIT--Changes mustbemadethrough “File info” 126 live insidethenodulesofsomeplants. bacteria, shownmagnifiedatthetopright, plant arecallednodules. Nitrogen-fixing swellings ontherootsofthissoybean Nitrogen-Fixing Bacteria Figure 2.3 Figure 2.4 The Nitrogen Cycle Ecology Unit 2:

The The Nitrogen Cycle bacteria are ofthe bacteria part acrucial these bacteria to supply bacteria nitrogen.these Asshown in called .into form auseful Allotherorganisms upon depend composers are essential to the nitrogen cycle because they break down down break they because cycle nitrogen the to essential are composers de These bacteria. of help the with soil the to released is things living atmosphere to the from cycles that nitrogen the of Some things. living and atmosphere the between moves nitrogen cycle, nitrogen the In Decomposers andthe Nitrogen Cycle bacteria, called altered,be orfixed, before organisms of canafewspecies it. use Only However, most organisms cannot atmospheric nitrogen. use It must new cells. Nitrogen makes up78percent ofthegases intheatmosphere. All organisms nitrogen need to build proteins, which are to build used oxide to form nitratesoxide to form that enter thesoil. nitrogen to form molecules oxide. Rainwater nitrogen combines with breaks nitrogen apart intheair, molecules which recombine oxygen with nitrogen enters through thesoil fixation by lightning. Energy inlightning theatmosphere, between trogen iscycled andorganisms. soil, Some animals, ofwhich are both sources ofusable nitrogen. nitrogenget from Animals thesoil. nitrogen get by eating plants orother Plantsthe soil. that donothave nitrogen-fixing intheirroots bacteria isreleasedbacteria nitrogen-fixing into live Some in bacteria thesoil. containing compounds such asnitrates. The excess nitrogen fixed by the sugarsThe use bacteria provided by thelegumes to produce nitrogen- roots ofplants include beans, called legumes. Legumes peas, andclover. Nitrogen-fixing bacteria, shownin nitrogen-fixing bacteria nitrogen cycle, Figure 2.4 can fixatmospheric nitrogen aprocess inwhich ni- Figure 2.3 , live onthe innodules , nitrogen-fixing -

(inset) ©Garry DeLong/Photo Researchers, Inc.; (bl) ©G.R. Roberts Photo Library ECOFACT

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wastes, such as urine, dung, leaves, and decaying plants and animals and return the nitrogen from these wastes to the soil. If decomposers did ECOFACT not exist, much of the nitrogen in ecosystems would be stored forever in Minerals in Your Mouth wastes, corpses, and other parts of organisms. After decomposers return Phosphorus is the 11th most the nitrogen to the soil, bacteria transform a small amount of the nitro- abundant element in the Earth’s crust gen into nitrogen gas, which then returns to the atmosphere. So, most and occurs naturally as phosphate of the nitrogen that enters an ecosystem stays within the ecosystem. It in the mineral apatite. Apatite can cycles between organisms and the soil, and is constantly reused. exist in igneous, metamorphic, and sedimentary rocks as well as in your teeth and bones. The Phosphorus Cycle The element phosphorus is part of many molecules that make up the cells of living organisms. For example, phosphorus is needed to form bones and teeth in animals. Plants get the phosphorus they need from soil and water, while animals get their phosphorus by eating plants or other animals that have eaten plants. The phosphorus cycle is the movement of phosphorus from the environment to organisms and then back to the environment. This cycle does not include the atmosphere because phosphorus rarely occurs as a gas. Phosphorus enters soil and water in many ways, as shown in Figure 2.5. When rocks erode by weathering, some phosphorus dissolves as phosphate in soil, water, and groundwater. Plants absorb phosphates in the soil through their roots. Phosphorus also leeches into soil and water when phosphate is excreted in waste from organisms and when organisms die and decompose. Some phosphorus also washes off the land and ends up in bodies of water. Many phosphates are not soluble in water, so they sink to the bottom of water bodies, and accumulate as sediment. Over many thousands of years, the sediments become rock.

Figure 2.5 The Phosphorus Cycle Weathering of phosphate from Rain rocks

Fertilizer containing phosphate

Runoff

Phosphate in water Decomposition of Leaching plants and animals Rocks

Phosphate in soil

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Figure 2.6

Fertilizers and Algal Blooms More than 30 percent of fertilizer may flow with runoff from farmland into nearby waterways. Large amounts of fertilizer in water can cause an excessive growth of algae (right).

Fertilizers and the Nitrogen and Phosphorus Cycles People often apply fertilizers to stimulate and maximize plant growth. Fertilizers contain both nitrogen and phosphorus. If excessive amounts of fertilizer are used, the fertilizer can enter terrestrial and aquatic ecosystems through runoff. Excess nitrogen and phosphorus in an or nearby waterway can cause rapid and overabundant growth of algae, which results in an algal bloom. An algal bloom, as shown in Figure 2.6, is a dense, visible patch of algae that occurs near the surface of water. Algal blooms, along with other plants and the bacteria that break down dead algae, can deplete an aquatic ecosystem of important nutrients such as oxygen. Fish and other aquatic organisms need oxygen to survive. Humans add so much nitrogen to the environment, that we have Check for Understanding doubled the amount of fixed nitrogen entering ecosystems on land. This Recognize How do algal blooms harm can lead to long-term problems in soil fertility because other nutrients aquatic ecosystems? are lost. Plants that are adapted to low nitrogen levels no longer thrive. (l) ©Nigel Cattlin/Photo Researchers, Inc.; (r) ©G.R. Roberts Photo Library Inc.; (r) ©G.R. (l) ©Nigel Cattlin/Photo Researchers,

Section 2 Formative Assessment

Reviewing Main Ideas Critical Thinking 1. Describe the two processes of the carbon 5. Making Comparisons Write a short cycle. paragraph that describes the importance of bacteria in the carbon, nitrogen, and 2. Describe how the burning of fossil fuels affects phosphorus cycles. What role do bacteria the carbon cycle. play in each cycle? 3. Explain how the excessive use of fertilizer 6. Applying Ideas What is one way that a person affects the nitrogen cycle and the phosphorus can help to reduce the level of carbon dioxide cycle. in the atmosphere? Can you think of more than 4. Explain why the phosphorus cycle occurs one way? more slowly than both the carbon cycle and the nitrogen cycle.

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©Hans Reinhard/Bruce Coleman, Inc./Photoshot establishing themselvesinagivenregion. Ecological Succession environmental changecalledecologicalsuccession. cover theconcrete ofademolishedcitybuilding.Theseare allexamplesofan wild­ the forest floor. Thesunlightallowsdormantornewseedstogerminate,andsoon been ashallowlakethousandyearsago.Adeadtree fallsandletssunlightreach Ecosystems are constantlychanging.Aforest hundreds ofyearsoldmayhave Change How Ecosystems Figure 3.1 life, such asonrocks orsand . This ofsuccession type iscalled . and earthquakes canand earthquakes regrow succession. through secondary by humans oranimals, orby natural processes such asstorms, floods, Forexisted. example, ecosystems that have disturbed ordisrupted been secondary succession primary succession Ecological succession American beech trees, beech American shown in continuewill to happen, but eventually acommunity canstable. become communities may stop changing oftime. forlong periods Small changes it harder fortheprevious community toIfgiven survive. enough time, hundreds orthousands ofyears. Each newcommunity that makes arises inacommunity. orallofthespecies Ecologicalsome succession may take flowers andshrubscovertheforest floor. Mosses,shrubs,andsmall trees Succession can inareas occur that previously didnotsupport .

A more ofsuccession, commontype called American beechtreesareastablecommunityspecies, isagradual process ofchange andreplacement of , occursinareas where anecosystem has previously Figure 3.1, are found aspecies inastable different from primary succession? different fromprimary Compare old-field succession. Explain whathappensduring succession. contribute toprimary Describehow succession. contributes toecological Explain how apioneerspecies succession. List two types ofecological succession secondary succession primary ecological succession Key Terms Che Section 3 c

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Figure 3.2 Primary Succession Primary succession can occur on new islands created by volcanic Pioneer Species Over a long period of time, eruptions, in areas exposed when a glacier retreats, or on any lichens can break down rock into soil. other surface that has not previously supported life. Primary succession is much slower than secondary succession because primary succession begins where there is no soil. It can take several hundred to several thousand years to produce fertile soil naturally. Imagine that a glacier melts and exposes an area of bare rock. The first species to colonize the bare rock will most likely be bacteria and lichens, which can live without soil. A species that colonizes an uninhabited area and begins the process of ecological succession are called pioneer species. Lichens, shown in Figure 3.2, are important pioneer species in primary succession. They are the colorful, flaky patches that you see on trees and rocks. A is a producer that is actually composed of two different species, a and green algae or cyanobacteria. The algae or the cyanobacteria photosynthesize, while the fungus absorbs nutrients from rocks and holds water. Together, they begin to break down the rock.

CASESTUDY Communities Maintained by Fire

Fires set by lightning or human activities occasionally sweep through large areas. Burned areas undergo Fireweed is one type of plant that colonizes secondary succession. In the forests of the Rocky Moun­ land after the land has been burned by fire. tains, for example, burned areas are rapidly colonized by fireweed, which clothes the slopes with purple flowers. In some places, fire determines the nature of the climax Longleaf pines have a strange growth pattern. When community. In the United States, eco­logical communities they are young, they have long needles that reach down that are maintained by fire include the chaparral of to the ground. The trees remain only about a half of a California, the temperate grassland of the Midwest, and meter high for many years, while they store nutrients. If a many southern and western pine forests. fire occurs, it sweeps through the tops of the tall trees that Plants native to these communities are adapted to living survived the last fire. The young longleaf pines near the with fire. A wildfire that is not unusually hot may not harm ground may escape the fire. Then, the young pines use fire-adapted pine trees, but it can kill deciduous trees— their stored food to grow very rapidly. A young pine can those trees that lose their leaves in winter. Seeds of some grow as much as 2 m each year. Soon the young pines are species will not germinate until exposed to temperatures tall enough so that a fire near the ground would not harm of several hundred degrees. When a fire sweeps through a them. forest, the fire kills plants on the ground and stimulates the If regular fires are prevented in a fire-adapted

seeds to germinate. community, deciduous trees may invade the area. These (b) ©Radius Images/Alamy Images; (t) ©Imagebroker/Alamy Images

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As the growth of the lichen breaks down the rock, water Figure 3.3 may freeze and thaw in cracks, which further breaks up the rock. Soil slowly accumulates as dust particles in the air are Primary Succession in Urban Areas Plants trapped in cracks in the rock. that grow through cracks in city sidewalks can also be described as pioneers of primary succession. Dead remains of lichens and bacteria add to the soil in the cracks. Mosses may increase in number and break up the rock even more. When the mosses die, they decay and add nutri- ents to the growing pile of soil. Thus, fertile soil forms from the broken rock, decayed organisms, water, and air. Primary succession can also be seen in any city street, as shown in Figure 3.3. Mosses, lichens, and weeds can establish them- selves in cracks in a sidewalk or building. As well, fungi and mosses can invade a roof that needs repair. Even a big city, such as New York City, would eventually turn into a cement- filled woodland if it were not constantly maintained.

CASESTUDY These young lodgepole pine trees have started growing after a devastating forest fire.

trees form a thick barrier near the ground. In addition, their dead leaves and branches pile up on the ground and form extra fuel for fires. When a fire does occur, it is hotter This firefighter is helping to maintain a and more severe than usual. The fire destroys not only the Criticalcontrolled Thinking fire in South Dakota. deciduous trees but also the pines. It may end up as a devastating wildfire. Although it may seem odd, frequent burning is essential Critical Thinking to preserve many plant communities and the animals that 1. Understanding Processes Explain how depend on them. This is the reason the U.S. National Park a longleaf pine might be more likely to Service adopted the policy of letting fires in national parks survive a forest fire than a deciduous tree, burn if they do not endanger human life or property. such as a maple or oak tree. This policy caused a public outcry when fires burned 2. Understanding Concepts Why must Yellowstone National Park in 1988, because people did not controlled fires be set in some ecosystems? understand the ecology of fire-adapted communities. The What are the advantages? What are the fires later became an opportunity for visitors to learn about disadvantages?

(t) ©Norman Owen Tomalin/Bruce Coleman, Inc./Photoshot; (br) ©B.G. Wilson Fire/Alamy Images; (bl) ©Ken M. Johns/Photo Researchers, Inc. Johns/Photo Researchers, Images; (bl) ©Ken M. Wilson Fire/Alamy Inc./Photoshot; (br) ©B.G. Coleman, Tomalin/Bruce (t) ©Norman Owen the changes in an ecosystem after a fire.

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Figure 3.4 Secondary Succession This illustration shows what an abandoned farm area might look like during old-field succession, a type of secondary succession.

critical thinking Infer Why do you think young oak trees begin to appear around year 20?

Secondary Succession When a community is partially or completely destroyed by a natural or a human-caused disaster, another community eventually takes its place. For example, when fire destroys a forest, new communities begin to grow in place of the old ones. Pioneer species colonize the area first and, over time, more stable species become established. A climax community is a final and stable community. Even though a climax community continues to change in small ways, this type of community may remain the same through time if it is not disturbed.

Old-field Succession When farmland is abandoned a type of secondary succession called old-field succession occurs. When a field is no longer cultivated, pioneer species such as grasses and weeds quickly grow and cover the abandoned land. The grasses and weeds produce many seeds to cover large areas. Over time, taller plants grow in the area and shade the ground, keeping FieldStudy light from the shorter plants. The long roots of the taller plants also ab- Go to Appendix B to find the field study sorb most of the water in the soil. The pioneer plants soon die from lack Investigating Succession. of sun­­light and water. As succession continues, growing trees deprive the taller plants of light and water. Finally, slower-growing trees, such as oaks, hickories, beeches, and maples, take over the area and block sunlight to the smaller trees. As shown in Figure 3.4, the area can eventually establish a climax community dominated by a mature oak forest. The field in Figure 3.5 was once used as farm land, but has since been abandoned.

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©Stephen Collins/Photo Researchers, Inc. Figure 3.5 Old-Field Succession seasons. Itisslowlybecomingforestedland. burn unless thefires are athreat to human lifeorproperty. cleared theland. Therefore, foresters allow sometimes natural fires to fires onthevegetation feed that because they sprouts after afire has and newtrees flourish. onoccasional animaldepend also Some species After afire, heavy growth ofsmall plants near theground often occurs nutrients succession these to uses grow.nutrients Secondary to thesoil. fires that burn out ofcontrol. Fire isimportant inhelping forests return contribute to major that and deadwood tions ofbrush wouldotherwise to theintense heatexposed ofafire. Minor forest fires remove accumula- such as theJack pine, can releasehave only after they theirseeds been communities,some intheCase Study. asdiscussed oftrees, species Some Fires caused by lightning are anatural succession in cause ofsecondary Fire andSecondarySuccession 4. 3. 2. 1. Section 3 ReviewingMainIdeas your answer. paragraph­succession. ashort Write to explain Describe damaging inthelong run. Explain theprocessduring ofecological succession. Describe Compare why putting out forest fires may be the role lichens play inprimary what role plays species apioneer primary and secondary succession. andsecondary primary Formative Assessment

This fieldwasonceplowed, buthassincebeenabandonedforoneormoregrowing 6. 5. CriticalThinking abandoned farm areas?abandoned farm How are different? they thatsimilar species to thepioneer colonize Analyzing Relationships your answer.Explain succession? orsecondary process primary years, alake amaple becomes forest. Is this Analyzing Processes How EcosystemsWork Chapter 5: beneficial toaforestcommunity. Identify Resources Protecting Natural Che

HMDScience.com c List two ways that firecan be List twowaysthat k f Over a period of1,000 aperiod Over o How are lichens r Understanding 133 DO NOT EDIT--Changes must be made through “File info” printcode=a

Maps in Action Tracking Bats and Insects in Texas

These images of bat and insect concentration in Central Texas were created using Doppler radar on the evening of May 19, 2002. Doppler radar can track the movement of objects in the air by bouncing electromagnetic energy off of them.

Map Skills Doppler radar can track the movment of objects in the air by bouncing electromagnetic energy off of them. Use these Doppler radar images from May 19, 2002 of bats and insects in Central Texas to answer the questions below.

1. Analyzing Data At what time was the bat and insect 4. Inferring Relationships Bracken Cave is home to concentration the lowest? At what time was the bat 20 million bats that eat millions of pounds of insects and insect concentration the highest? nightly. Approximately how far is Bracken Cave from the city of San Antonio? If the bat population in the 2. Interpreting Graphics Use the concentration key to cave drastically decreased, what effect would this determine which area of Central Texas has the highest decrease have on the people living in San Antonio? concentration of bats and insects at 8:14 p.m. 5. Predicting Patterns These Doppler radar images 3. Analyzing Data Approximately how many kilometers of bats and insects were taken in the beginning of the wide is the concentration of bats and insects at summer season. How might these four images look in 7:27 p.m.? at 8:14 p.m.? the month of December?

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Society and the Environment ECOZine Go online for the latest environmental science at HMDScience.com news and updates on all EcoZine articles. Changing Seas

Most of the food we eat comes from agriculture and farming, but we also rely on the fishing industry. About 15% of the animal consumed in the world comes from fish and other marine and aquatic organisms. But many fish species have been overharvested. The swordfish and cod fisheries of the North Atlantic and the salmon fishery off the northwestern coast of the United States are examples of depleted fisheries. In many parts of the world, sharks are disappearing rapidly because of the demand for shark fin soup. Some fisheries now contain so few fish that harvesting them is not economical. And the size of some of the harvested fish that remain are now smaller because they don’t survive long enough to grow. Despite the challenges of catching large fish, the demand outweighs the cost. Fishing Down the Food Chain $700,000! At prices that high, it is economical to keep fishing Fish such as sharks, tuna, and cod are top carnivores in even after populations are scarce. ocean food chains and food webs. As populations of these fish Scientists are working to determine what species are most have declined, species from lower trophic levels that were at risk of overfishing and what will happen to ecosystems if once swept back into the sea have become more common overfishing continues. If the food webs of ocean ecosystems in fish markets. Organisms from lower trophic levels such as are altered too much, the commercial fishing industry will be mullet, squid, and herring, which often are used as bait, now in trouble so it makes economic sense for fishers to protect appear on restaurant menus. Also, the high prices for large the . fish have encouraged fisheries to catch these predators. In 2012, one bluefin tuna weighing almost 273 kg sold for over Creating Sustainable Fisheries

Overfishing from higher trophic levels means One aim of environmental science is to determine how commercial fishers must harvest from lower fisheries can be managed so that they are sustainable or trophic levels to meet demand . capable of supplying the same number of fish to be harvested each year. One solution is to establish “no-take” zones. These are areas of the sea where no fishing is permitted. Fish populations grow rapidly in these zones. When a population growsWhat in a “no-take Do You zone,” Think? some organisms leave the zone and become available to fishers. “No-take” zones help populations recover and allow food chains and food webs to remain intact.

What Do You Think? The next time you go to a fish market or seafood restaurant, take note of the different types of species for sale. Write down the names of the species, and try to assign each species to a trophic level. How many of the species for sale belong to lower trophic levels? How many belong to higher trophic levels? How do prices differ between the species for sale? (bl) ©Stephen Rose/Rainbow; (t) ©MIXA Co. Ltd./Getty Images (bl) ©Stephen Rose/Rainbow; (t) ©MIXA Co.

Chapter 5: How Ecosystems Work 135 printcode=a DO NOT EDIT--Changes mustbemadethrough “File info” 136 Chapter 5 Section 3 Section 2 Section 1 Ecology Unit 2: HowEcosystemsChange The CyclingofMatter Energy FlowinEcosystems Summary Objectives • • • Objectives • • • Objectives • • • the organismiseaten. contains istransferredtothenexttrophiclevelwhen anorganism that Only about10percentoftheenergy food chains, foodwebs, andtrophiclevels. through transfercanbefollowed ofenergy The paths producersorotherconsumers. by eating thesis, whileconsumersusethesun’s indirectly energy ers harnessthesun’s directlythroughphotosyn- energy Most organismsdependonthesunforenergy. Produc- is disturbedagain. take overanecosystemandremainuntilthe Climax communitiesaremadeupoforganismsthat occurs on a surface where an eco-system existed before. ­ecosystem existedbefore. succession Secondary successionoccursonasurface whereno Primary ­succession. ofchangeovertime,a pattern asecological known After adisturbance, organismsinanenvironment­ fertilizer tosoil. fuels andapplying ­ecosystem throughactivitiessuchasburningfossil Humans canaffectthecycling inan ofmaterials acycle.Each oftheseelementsfollows Carbon, nitrogen, andphosphorusareessentialforlife. processes. natural inecosystemsare recycledMaterials andreusedby follow follow Key Terms trophic level food web food chain cellular respiration decomposer consumer producer photosynthesis Key Terms climax pioneer species secondary primary ecological Key Terms phosphorus cycle nitrogen cycle nitrogen-fixing carbon cycle ­community ­succession ­succession ­succession ­bacteria

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Chapter 5 Review

Reviewing Key Terms 14. Which of the following pairs of organisms probably belong to the same trophic level? Use each of the following terms in a separate sentence. a. humans and bears 1. photosynthesis b. bears and deer 2. trophic level c. humans and cows 3. carbon cycle d. both (a) and (c) 4. nitrogen-fixing bacteria 5. decomposers 15. The energy lost between trophic levels a. can be captured only by parasitic organisms. For each pair of terms, explain how the meanings of the terms differ. b. cools the surrounding environment. 6. producer and consumer c. is used in the course of normal living. 7. primary succession and secondary succession d. evaporates in the atmosphere. 8. nitrogen cycle and phosphorus cycle 16. From producer to secondary consumer, about 9. food chain and food web what percentage of energy is lost? 10. Concept Map Use the following terms to a. 10 percent create a concept map: algae, humans, solar b. 90 percent energy, carnivores, consumers, producers, directly, herbivores, indirectly, and omnivores. c. 99 percent d. 100 percent

Reviewing Main Ideas 17. Which of the following statements about the 11. Which of the following statements is not true nitrogen cycle is not true? of consumers? a. Animals get nitrogen by eating plants or other a. They get energy indirectly from the sun. animals. b. They are also called heterotrophs. b. Plants generate nitrogen in their roots. c. They make their own food. c. Nitrogen moves back and forth between the atmosphere and living things. d. They sometimes eat other consumers. d. Decomposers break down waste to yield 12. Which of the following is correctly arranged from ammonia. the lowest trophic level to the highest trophic level? a. bacteria, frog, eagle, raccoon 18. Which of the following are most likely to be the pioneer organisms on an area of bare rock? b. algae, deer, wolf, hawk a. trees c. grass, mouse, snake, eagle b. shrubs d. grass, bass, minnow, snake c. lichens 13. Communities of bacteria have been found living d. perennial grasses thousands of feet underwater. Which of the following statements is a proper conclusion to 19. Excessive use of fertilizer that contains nitrogen draw about these bacteria? and phosphorus a. Somehow they are conducting photosynthesis. a. affects the carbon cycle. b. They are living on borrowed time. b. may cause algal blooms in waterways. c. They were somehow introduced by human c. causes soil erosion. activities. d. contributes to primary succession. d. They use an energy source other than sunlight.

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Chapter Review

Short Answer Critical Thinking 20. Explain the relationship between cellular 28. Comparing Functions How are producers and respiration and photosynthesis. decomposers opposites of each other? 21. Why is the number of trophic levels that can exist 29. Inferring Relationships Abandoned fields in limited? the southwestern part of the United States are 22. Why are decomposers an essential part of an often taken over by mesquite trees, which can ecosystem? grow in nutrient-poor soil. If the land is later cleared of mesquite, the soil is often found to 23. Write a short paragraph that explains why the be enriched with nitrogen and is more suitable phosphorus cycle occurs slower than the carbon for crops. What might be the reason for this and nitrogen cycles. phenomenon? 24. Describe what happens to carbon dioxide in the 30. Understanding Concepts Read the description carbon cycle. under the head “What Eats What” in this chapter, and explain why decomposers are considered to be consumers. Interpreting Graphics 31. Drawing Conclusions Suppose that a Use the diagram to answer questions 25–27. plague eliminates all the primary consumers 25. How many organisms depend on the squid as a in an ecosystem. What will most likely happen source of food? to organisms in other trophic levels in this ecosystem? 26. If the population of Adélie penguins decreased 32. Interpreting Data drastically, what effect would this have on If a lake contains 600,000 elephant seals? kg of plankton and the top consumers are a population of 40 pike, which each weigh an 27. What role do algae play in this food web? average of 15 kg, how many trophic levels does the lake contain? Make a graph or pyramid that illustrates the trophic levels. Killer whale 33. Compare and Contrast Do a special project on succession. Find areas in your community

Crabeater that have been cleared of vegetation and left seal Elephant unattended at different times in the past. Ideally, seal you should find several areas that were cleared at different times, including recently and decades ago. Photo­graph each area, and arrange the Leopard pictures to show how succession takes place in seal Antarctic tooth sh your geographic region.

Adélie Squid penguin

Krill

Small animals Algae and one-celled organisms

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Chapter Review

STUDYSKILL Analyzing Data CASESTUDY Use the data in the table below to answer questions 34–35. 38. Compare energy transfer in a food chain and a food web with the transfer of pollutants in a Percentage of Fertilizer food chain and a food web. Use per Year 39. How can a change in an ecosystem impact the biogeochemical cycles, for example the Region of the World Percentage Whycarbon It Matters cycle? North America 17 Why It Matters Asia 48 40. How does a change Africa 2 in a food web relate Europe 14 to energy flow within an ecosystem? Latin America and the 18 ­Caribbean Oceania 1

34. Making Calculations If 137.25 million metric tons of fertilizer is used worldwide per year, how many million metric tons does Asia use? 35. Graphing Data Make a bar graph that compares the percentage of fertilizer use in different regions worldwide per year. STUDYSKILL Taking Multiple-Choice Tests When you take multiple-choice tests, be sure to read all of the choices before Making Connections you pick the correct answer. Be patient, and eliminate choices 36. Communicating Main Ideas Describe that are obviously incorrect. the importance of the carbon, nitrogen, and phosphorus cycles to humans. 37. Writing from Research Research information on how countries regulate carbon dioxide emissions. Write an essay that describes the laws regulating carbon dioxide emissions and the solutions some countries have devised to decrease the amount of carbon dioxide emitted. ©A. Cosmos Blank/Photo Researchers, Inc. Cosmos Blank/Photo Researchers, ©A.

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ExplorationLab Data Analysis Factors that Influence Objectives Hypothesize how Ecosystems precipitation and altitude affect the types of vegetation Ecosystems are communities of plants, animals, and other organisms in an ecosystem. that live and interact with each other and with nonliving environmental Graph and analyze factors. The nonliving factors, or conditions, include temperature, ecosystem data to confirm or precipitation, altitude, and latitude, among others. These factors play refute your hypothesis. an important role in determining what types of vegetation can live in an ecosystem. Materials Latitude, for example, has a strong influence on an area’s temperature, colored pencils resulting in climates such as polar, tropical, and temperate. These metric ruler climates determine different natural biomes that have characteristic species of plants. However, a careful look at a map reveals that ecosystems existing at the same latitude often have different climates. Why? In this laboratory activity, you will hypothesize how other nonliving factors influence the characteristics of ecosystems within the same latitude range. Then you will analyze and graph data from different areas of the United States to test your hypotheses.

Procedure 1. Form two hypotheses—one that relates differences in ecosystem vegetation to rainfall and another that relates differences in ecosystem vegetation to altitude. Complete the following sentences to form your two hypotheses. a. Ecosystem distribution is related to precipitation; regions that receive large amounts of precipitation are wet and therefore _____. b. Ecosystem distribution is related to altitude; regions at high elevations are cold and therefore _____.

2. Look at the data table. The table lists major U.S. cities and weather stations between 36° and 41° north latitude. It also lists the altitude, average annual precipitation, and ecosystem for each location. Construct a graph with two y-axes to plot the data in the table. Plot altitude on the left-hand y-axis and annual rainfall on the right-hand y-axis. Plot distance on the x-axis. Use one of your colored pencils to connect the data points for altitude. Use another color to connect the data points for annual rainfall. You may also find it useful to label the location names on the grid above your data points. Your completed line graph will help you interpret any relation among rainfall, altitude, and biome type.

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Characteristics of Locations Across the U.s. Location Distance from Altitude above Average Biome or San Francisco sea level (feet) rainfall ecosystem (miles) (in/yr) San Francisco, CA 0 250 23 redwood forest Sacramento, CA 100 26 19 grassland Donner Pass, CA 200 7,000 69 coniferous forest Reno, NV 250 4,400 8 cool desert Salt Lake City, UT 650 4,200 16 cool desert Loveland Pass, CO 900 11,000 38 coniferous forest Denver, CO 950 5,325 12 short grass prairie Topeka, KS 1,450 925 34 tall grass prairie St. Louis, MO 1,750 567 37 broadleaf forest Cincinnati, OH 2,100 488 40 broadleaf forest Washington, D.C. 2,500 9 39 broadleaf forest

Analysis 1. Identifying Patterns Which types of ecosystems occur in areas of high and low precipitation?

2. Examining Data Is there a trend in the amount of precipitation from Denver to San Francisco or from Denver to Washington, D.C.?

3. Analyzing Results How do mountain ranges affect precipitation? Give an example that supports your answer.

Conclusions 4. Evaluating Data Which is the more important factor in determining an area’s ecosystem, the amount of precipitation or altitude? Is there an interaction between these two factors?

5. Defending Conclusions Does the data support or refute your hypotheses about the effects of precipitation and altitude on an ecosystems type?

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