Human Impact on Ecosystems 471 Correctionkey=B DO NOT EDIT--Changes Mustbemadethrough “File Info” 472

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CHAPTER Big methods are necessary to protect Earth’s natural resources. environmental quality andbiodiversity, so conservation ONL t 16.4 16.2 16.5 16.3 Online Bi 16.1 Unit 5:Ecol ■■ ■■ ■■ ■■ ■■ ■■ 16 Caffeine and SeedGermination Contamination ofGroundwater Water Quality Testing Open QuickLab Acid Rain I I N dea

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Effects ofAcidRainonSeeds

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Q What happened to this forest? This once lush hillside has been destroyed by acid rain. Emissions from a nearby steel plant release chemical compounds that change the natural pH of rain, forming acid rain. Not only does acid rain damage leaves and branches, but because it lowers soil pH, it can damage plant root systems and kill useful microorganisms that release nutrients from dead organic material.

READING Toolbox This reading tool can help you learn the material in the following pages.

USING LANGUAGE Your Turn Finding Examples Concrete examples often help Use what you have learned about examples to answer the clarify new information. Certain words and phrases can following questions. help you recognize examples. These words include for 1. Find the examples in the following sentence: The example, such as, like, and including. Burmese python feeds on small animals such as rats, birds, raccoons, and even dogs. 2. Find the examples in the introductory paragraph of this reading tool.

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ecological footprint ecological resource renewable nonrenewable resource VOCABULARY impact ecosystem stability how environmental change can bases that are limited; 12Fdescribe dependent onchangingresource long-term survival ofspeciesis external factors; 12Drecognize that and communities respond to analyze ho F Unit 5:Ecol igure

Population (billions) 10 0 8 6 4 2 1015 5015 902150 1950 1750 1550 1350 1150 11 1.1 w organisms, populations, B 16.1

Projected Actual ogy investigate and W orld Source: United Nations, World Population 11b, 12 Prospects, Population Reference Bureau P opul Year d Resources Human Population Growth andNatural , 12 a f t ion E E energy andnutrient cycles ofEarth. overuse ofresources andtheproduction ofwaste can cause disruptions inthe ofEarth’sa part cycles. Everything we eat, anduse comes drink, from Butthe Earth. sources replenished by thehydrologic cycle. We donot justuse Earth’s cycles, we are plants that dependonEarth’s nutrientcycles. Thewater you drinkcomes from water else inourhomesandcities.Your cotton T-shirt andthispaperpage came from to power ourtelevisions, radios, streetlights, automobiles, airplanes—and everything Humans dependuponEarth’s nutrientandenergy cycles. We harness Earth’s energy Connect to Your World Ke arth arth’s human population continues to continues grow. population arth’s human

y maximum population sizethat an environment can consistently support. capacity for humans capacity that refers carrying Recall on Earth? to the How many support? people can Earth In other words, what is carrying the MAIN ID MAIN MAIN ID C

onc Effective management ofEarth’s resources helpmeettheneedsoffuture. will The growing humanpopulation exerts pressure onEarth’s natural resources. Earth’s humanpopulation continues to grow. ’s resources increases. e p E E t A AS

Earth cannotEarth support an infinite number of people. number of people can that support, Earth some limit must exist— 50 billion people? Although we do not know of limit afixed to the future, support Earth 10billion will people, 20billion, or even than 7billion hasmany exceeded earlier predictions. In the size has changed over time. Today’s human population of more around 1billion. The graph in capacity.carrying In Malthus’s lifetime, world the population was tions are they when describing concept the of an ecosystem’s could support. Today, scientists his use observations and predic human population was growing faster than Earth’s resources Malthus wrote acontroversial essay inwhich he claimed that the over time. In late the 1700s,ayoung economist named Thomas predictionsOur of Earth’s human capacity have carrying changed E As thehumanpopulation gr arth’s Capacity Carrying 12D, 12F 12D,

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placed at same the rate at a which it is called is used technologies are other to forms use developed of energy. of limited this unless ahead decades resource inthe crises to lead energy will million barrels day, per and world oil continues use to The rise. growing use form.they In human 2006,the population was using oil at arate of about 77 example, wind energy—captured by wind turbines such shown as those in figure nonrenewable carbon substances we today use as oil and and are Oil coal. coal years, natural processes transformed organisms dead into concentrated the and are use. Oil energy coal result the of natural processes. millions Over of Two resources, oil and currently coal, support majority the of our country’s have allowed for continued human population growth. gas, or construction ifall had done to be by hand? Technological advances no medicines? How many support people could Earth without or electricity portation to move and food materials around What globe? the ifthere were homes and to human take waste out of homes? What ifthere were no trans have human lives changed with help the of plumbing to bring fresh water into antiseptics have lowered infant mortality and spread the of diseases. 1000births. In 2002,onlyevery 7infants 1000births. Antibiotics per died and dropped steadily over last the 70years. In 1940,more than 40infants for died tion growth. For example, infant mortality rates United inthe States have human and animal power. Medical advances have contributed also to popula made possible production the of much more than produced could food be by people than Malthus could ever have imagined. Motorized farm equipment, capacity has greatly of Earth increased. agriculture, transportation, advances, medical and sanitation, carrying the ronment changes. As humans have environment their modified through capacity that of carrying the Recall an environment can change as envi the T if renewable resources are not carefully, used can become nonrenewable. they are replenished faster are than are they they used, considered renewable. But regrowth and reproduction, are they renewable. As long resources as these and up, animals, used can be but could last they indefinitely because through upused by humans. resources, Other such that as those come from plants MAIN ID MAIN echnology and Human Population Human and echnology E Not a For am Tec art 1.2

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FIGURE 1.3 surrounding ecosystem. sustains theneedsof such aslakes, rivers, andaquifers cycling ofwater from resources back to Earth’s surface. This through Earth’s atmosphere and hydrologic cycle moves water Ecology, you learned how the In thechapter Principles of H island’s ancientinhabitants. eerie reminder ofthefate ofthe lands Unit 5:Ecol ydrologic CONN capes ofEaster Island are an E

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T O C ycl e help meet the needs of the future. ofthe needs the meet help E no Analyze ffective of management

generated 1ton of garbage each year? almost 1ton year. per What would happen ifeach of Earth’s 7billion humans million tons of garbage. That is about 4.2pounds day, per person, or per any year, Each other on country Earth. United the States generates about 230 Today, United the States more uses resources and produces more waste than renewable and nonrenewable resources become increasingly will important. aquifers faster than it is replaced. United States with fresh water. Groundwater being is also foundwater in sources that supply tens of millions of people across the down forests the for lumber and for building boats. The trees were cut down stone monuments for whichisland the is now famous. The inhabitants cut The humanspecies. colony grewquickly over next the 1000years, building the 400 CEand 700CE,it was thickly forested on rich soil, with many bird careless of use resources. When humans first landed on Easter Island between for future generations. The responsible of use Earth’s resources can help to maintain resources these Management of Earth’s resources current both affects and future generations. its s MAIN ID MAIN nrenewable resource. nrenewable The s As Ea waterDrinking is arenewable resource, but pollution and overuse threaten upply. Pesticides, industrial waste, and other contaminants have been

E xplain how a renewable resource such as water could become a become could water as such resource how arenewable xplain tory oftory Easter Island is acautionary of caused tale destruction by rth’s human population continues to grow, management the of E A

11b, 12D, 12F 12D, 11b, figure Easter Island with was no left trees, as shown in faster could than grow they back. Eventually, use haduse negative long could not maintained be into future, the and its for future generations. sources in such away available be that will they sustainable of use resources means using re to short their meet tainable. In other words, islanders the trees used crashed and Easter the Islanders disappeared. gone, Easter the Island human population Without and food islandfishing. resources nearly lost. Without boats, there was no offshore habitat for island’s the animal populations was shelter or boats, richwashed soil the away, and The E 1.3. aster Islanders’ of use trees was unsus Without trees, there for was no wood E art h’s resources will - te rm needs. But needs. rm resource this - te rm effects. In effects. contrast,rm extra cted from

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and amount the and toxicity of waste produced. include amount the of resource and efficiency use, footprint dependson anumber of factors. These ecological footprint. water, shelter, energy, and wastean is called to producesary and maintain enoughand food Theeach amount person on Earth. of land neces depends on how much land to support is needed humanthe population. Earth’s capacity carrying waythe resources are threatens used welfare the of Humans natural need resources tobut survive, E future generations, dependson sustainable management of Earth’s resources. and how much for reserved humans welfare, Our to drink? and welfare the of much for other How uses? much fresh water for should used be crop irrigation maintained toneeds be for agriculture, how much for living space, and how production should individuals and populations allowed? be How much land resource and use waste production? If so, how much resource and use waste more important as we move into future. the Should we have to regulate rules decisions. Waste production and management is an issue that become will nations have alot more “feet.” tion. Individuals United inthe States may have alarge footprint, but other have populations that are more than three sizeof times the U.S. the popula indevelopinguals nations is growing, and nations such as Chinaand India and is one of largest the world. inthe But footprint ecological the of individ footprintecological covers an area larger than (9.7hectares) fields 24football footprints.ecological The average U.S. citizen’s tion of waste, and therefore sizeof inthe their lations of use intheir resources vary and produc

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(hectares per person) 475 CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info” Unit 476 FIGURE warming global effect greenhouse rain acid particulate smog pollution VOCABULARY the United States. growing problem inmanyareas of and industrial processes. Smogisa duced by automobile emissions ofLo city ecosystem stability environmental change can impact factors and12Fdescribe how communities respond to external how organisms, populations, and

5: 11Binvestigate andanalyze

2.1 Ecology s Angeles islargely pro- 16.2

The hazyfog over the 11 b , 12 f Air Quality P how from doesairpollution fossil fuelsaffect thebiosphere? pollute Earth’s biosphere. Withoutthisenergy ourlives would bevery different, but humans burnthese fuelsin theform ofgas andoil,we are creating compounds that This energy was absorbed by ancientorganisms andstored intheirbiomass. Today, as ride inacar, you are beingtransported by energy that originally came from thesun. Fossil fuelsare ofmodernsociety. part animportant Consider that every timeyou Your to World Connect Ke ollutants accumulate air. the in

y soil. Pollution can form the take of microscopic air or particles, waste products anydescribes undesirable factor, or pollutant, that is to added air, the water, or addition of materials these to environment the pollution. is called Many of cannot them integrated be into normal ecosystem functions. The yearcycles. Each humans add synthetic chemicals and materials to Earth. the biosphere.the actions Our have direct and on indirect effects Earth’s natural Although it is sometimes to easy forget, humans are an important of part M MAI C

ai o Air pollution ischangingEarth’sAir pollution biosphere. Pollutants accumulate intheair. n I n n N c ID d ept e E a AS

can disrupt of function the ecosystems. immediate or delayed, but may effects these add up over and time down kitchen the of The effects pollutants sink. harmful can be from factories and sewers, or household chemicals that are poured Smog and Ozone and Smog haze of matter smog, shown called in compounds released through process this can combine to form a produced by burning fossil fuels such as gas and oil. Chemical The most common air pollution comes from waste the products P of smog, including particulatematter and ground-level ozone. produced by fossil emissions. fuel There are components several air pollution caused by interaction the of sunlight with pollutants problems. and inhaled particulates can can cause be many of types health atmosphere for weeks before to settle ground. the they Fine processes. Once air, inthe some particulates may stay inthe fuel, 1–10microns insize, that are produced by many industrial Fossil fuel emissions affect the biosphere. the affect emissions fuel Fossil articulates 11B, 12F

are microscopic bits of dust, and metal, unburned figure 2.1. figure

Smog P is a type ofis atype ollution

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The second component of smog is ground-level ozone. In the presence

of sunlight, two types of chemicals react to produce ground-level ozone (O3). Nitrogen oxides are produced during fossil fuel combustion, and these chemicals give smog a yellowish color. Ozone is formed when nitrogen

dioxide (NO2) reacts with oxygen (O2) present in the atmosphere. In this

reaction, one oxygen from an NO2 molecule is transferred to an O2 molecule,

forming ozone (O3). The ozone produced by reactions of nitrogen oxide and oxygen tends to stay close to the ground, where it can be harmful to human health and ecosystem functions. Although ozone is harmful to organisms, it also plays an important, protective role in the Earth’s upper atmosphere. High concentrations of ozone in the stratosphere, also known as the ozonosphere or ozone layer, act as a shield protecting Earth’s biosphere against harmful ultraviolet rays found in sunlight. Acid Rain The chemicals produced by the VISUAL VOCAB burning of fossil fuels become part Acid rain is a type of precipitation of the ecosystem and can change produced when pollutants in the the products of natural cycles. For water cycle cause rain pH to drop below normal levels. example, nitrogen oxides and sulfur oxides from fossil fuel emissions can Acid rain Normal rain pH 4.6 pH 5.6 lead to the formation of acid rain. CONNECT TO Acid rain is a type of precipitation H+ ions pH produced when pollutants in the Recall from the chapter water cycle cause rain pH to drop Chemistry of Life that pH is a below normal levels. measure of the concentration of H+ ions in a solution. The During the water cycle, rain falls through Earth’s atmosphere and interacts concentrations of H+ ions in acid with carbon dioxide molecules. As it falls, water molecules react with carbon rain are very high, giving the rain dioxide molecules to form a weak carbonic acid, which then breaks apart, a lower pH level. leaving lone hydrogen ions. This is normal. All rain that falls is slightly acidic, with a pH around 5.6. When pollutants such as nitrogen oxides and sulfur oxides become a part of the water cycle, acid rain is the result. Reactions FIGURE 2.2 The wide growth rings of this tree indicate a healthy between these chemicals and the oxygen and water normally present in the environment. The smaller growth atmosphere create sulfuric and nitric acids that can cause pH levels to fall rings illustrate how acid rain below 5.6. directly impacts plant growth. Acid rain falls in many areas of the United States and has a major effect on ecosystems. By decreasing pH levels in lakes and streams, acid rain threatens water supplies and species habitat. Acid rain can cause a decline in growth rates, as shown in figure 2.2. It can also cause leaves and bark to break down more quickly and make trees more vulnerable to disease and weather. Synthesize As the human population continues to increase and use more fossil fuels, why might acid rain become a bigger problem? ©Adam Hart-Davis/Photo Inc. Researchers,

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Main Idea 11B, 12F Air pollution is changing Earth’s biosphere. Earth’s atmosphere naturally includes molecules of carbon dioxide that play an important part in keeping the biosphere at a temperature that can support life. The levels of atmospheric carbon dioxide rise and fall over time as a normal part of the climate cycles of Earth. Collections of data World Temperature Change from arctic ice cores allow scientists to look deep into Earth’s atmospheric history. They have discovered that 300 Temperature 10 cycles of rising and falling carbon dioxide levels follow

CO2 8 Temperature variation (°C) known patterns of periodic warming and cooling. 6 The relationship between changes in global average 4 temperatures and carbon dioxide levels is shown in 2 FIGURE 2.3. We know that high levels of carbon dioxide 200 0 are typical of Earth’s warmer periods, while low levels -2 are associated with cool climates, eventually leading to -4 concentration (ppm) concentration 2 -6 periods of extreme cold called ice ages. CO -8 100 -10 The Greenhouse Effect 400 300 200 100 0 Earth gets nearly all of its energy from the wavelengths Thousands of years ago of both visible and invisible light emitted by the sun. Source: Petit, J.R., et al., Nature 387:359. When the sun’s waves reach Earth, some are absorbed by Earth’s atmosphere, but many of these rays pass FIGURE 2.3 Scientists have through the atmosphere and reach Earth’s surface. Some of this energy is found that changes in Earth’s absorbed by Earth’s surface, but it is later reradiated as invisible infrared temperature correspond with fluctuations in global carbon radiation—energy in the form of heat. After being reradiated from Earth’s dioxide levels. surface, this energy could travel away from Earth, be lost into space, and leave an extremely cold Earth that could never sustain life. But Earth is not cold and does have life. So what keeps Earth’s temperature from dropping to extreme freezing conditions? To answer this question, think about the greenhouses that scientists and gardeners use to grow plants. Greenhouses use glass that allows light and radiation from sunlight to pass through and provide energy for plant growth. The glass also prevents infrared radiation from escaping. This infrared radiation keeps the inside of the greenhouse warm. This same phenomenon occurs in a car, causing the inside to warm when the windows are closed. In the same way that greenhouse glass creates an environment for plants to grow, the chemical composition of Earth’s atmosphere plays an important role in maintaining an environment that is suitable for life. Earth’s atmosphere contains gases called greenhouse gases that act as insulators and slow the loss of heat through the atmosphere. Water vapor, carbon dioxide, and methane are three of the most common greenhouse gases found in the atmosphere. Greenhouse gases absorb wavelengths of infrared radiation. This process is called the greenhouse effect and is illustrated in figure 2.4. The greenhouse effect occurs when carbon dioxide, water, and methane molecules absorb energy reradiated by Earth’s surface and slow the release of this energy from Earth’s atmosphere.

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FIGURE 2.4 Greenhouse Effect

Water vapor, carbon dioxide, and methane can be found all through Earth’s atmosphere. These greenhouse gases act as a blanket that slows the release of energy and helps to keep Earth at a temperature that can support life. 3 Greenhouse gases in the atmosphere Short, high-energy carbon dioxide (CO2) 1 absorb many of the wavelengths of light longer wavelengths of emitted from the sun infrared radiation. penetrate Earth’s atmosphere. methane (CH4) water (H2O)

2 Energy from the sun is absorbed by Earth and reradiated as infrared radiation, or heat. 4 The molecules rerelease infrared radiation, which is absorbed again by other molecules, Earth’s surface, or is lost in outer space.

Global Warming

As automobile use and industry have grown, so have the Global Temperature And Carbon levels of carbon dioxide and other greenhouse gases in the Dioxide Levels Over Time atmosphere. This graph shows average global temperature 370 0.60

changes (blue) against atmospheric carbon dioxide levels Temperature Temperature variation (°C) (green) measured at Mauna Loa Observatory in Hawaii. 360 CO2 0.45 350 0.30 340 0.15 330 0.00

concentration (ppm) concentration 320 2

CO 310 -0.15 300 -0.30 1960 1970 1980 1990 Year Source: University of California, Scripps Institute of Oceanography/ Hadley Centre for Climate Prediction and Research

CRITICAL How would an increase in atmospheric greenhouse gases contribute to an VIEWING increase in average global temperatures? 12F (bl) ©Dennis MacDonald/Alamy Images; (background) Baden/zefa/Corbis ©G.

479 CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info” Unit 480 ice boundary in 1979 Summer Arctic Sea Global Warming Carbon Dioxideand ONLINE GO North PoleNorth by about20percent. summer ice pack around the temperatures have decreased 20 ye FIGURE 16.2 3. 2. 1. Re

ars, increasing global

increase Earth’s global temperature. dioxide in theatmosphere could Explain how abuil keep warm? Earth How doesthe Name anddescribe two w which 5: vi HMDScience.com 2.5

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Over thepast affectspollution ecosystems. 11B, 12F Formative Assessment n g greenhouse effect

M d-up ofcarbon N ai orth orth n I n P ays in ole d e as Connect sphere, and change planet the that home. we call by year the 2100,achange that could have dramatic on effects Earth’s bio- temperatures could increase on anywhere Earth from 1.1to 6.4°C(2to 11.5°F) future of climate change isbut uncertain, scientists predict that average process, or may of they beginning the arapid be climate global change. The weather global affect patterns. changes These may of part aslow be warming

just afew of threats the that may caused by be climate change. As shown in strongerincreased flooding, tropical storms, and loss the of biodiversity, are already threatening ecosystems around world. the disasters, Ecological such as biosphere.global What do know they is that shows evidence climate change is agree that we must steps take to slow process. the on how much human this impact is influencing warming the trend, but most emission of greenhouse over gases past the 100years. Scientists may disagree doubt that growth the of and of industry use automobiles has increased the greenhouse such gases as carbon dioxide, water, and methane. There is no figure 2.5, figure Scie 12F

How might climate change affect seasonal temperature changes? changes? temperature seasonal affect change climate How might ntists do not know how atmospheric these changes the affect will 5. 4. C

the polar the icepack is melting at arapid pace, which may eventually trophic structure oftheecosystem. falling inaforest could disrupt the Connect P Earth’s surface. functions of greenhouse gases at redict t ical 11B, 12F

Describe how t Nam hi n e two important ki n temperature are result the of increased levels of evidence, scientists can infer that changes the in is known as sands of years, not over 100years. temperature over generally occur tens of thou- ofpart Earth’s climate cycle. But major changes in temperatureGlobal fluctuations are anormal years. What is causing intemperature? rise this most dramatic change over occurring past the 50 temperature with 0.74°C(1.3°F), the has risen past the 100years,Over average the global Climate Change g acid rain The t rend of increasing temperatures global global warming. GO ONLINE GO 6. F ood

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T’ g azin ! A m Video Inquiry BIOLOGY Carbon Dioxide and Killer Kitties Human Effects on a Food Global Warming Analyze What happens when house cats go Web Apply a human- carbon dioxide levels on wild? Find out how they can disrupt induced change to a food Earth over time. the balance of an ecosystem, and learn web and see how the about how we can fix the problem. change ripples through the system.

online biology 481 HMDScience.com DO NOT EDIT--Changes must be made through “File info” CorrectionKey=B

16.3 Water Quality

11B, 12C, 12D, Key Concept pollution of Earth’s freshwater supply threatens 12F habitat and health. VOCABULARY MAIN IDEAS indicator species Water pollution affects ecosystems. biomagnification Biomagnification causes accumulation of toxins in the food chain.

11B investigate and Connect to Your World analyze how organisms, populations, and communities respond to When you swallow a pill, your body only uses a part of the medicine in the pill and external factors; 12C analyze the gets rid of the rest as waste, which is flushed away. Scientists have detected traces of flow of matter and energy through trophic levels using various models, many prescription drugs in freshwater supplies. Several fish species that live in fresh including food chains, food webs, waters have been exposed to the female hormone estrogen. Some of the male fish and ecological pyramids; 12D recognize that long-term have begun showing female characteristics. These “gender-bending” fish are only one survival of species is dependent on effect of water pollution. What other pollutants can be found in our water? changing resource bases that are limited; 12F describe how environmental change can impact ecosystem stability. MAIN IDEA 11B, 12D, 12F Water pollution affects ecosystems. Biology VIDEO C Pollution can have a major impact on water ecosystems. Chemical contami- LIP nants, raw sewage, trash, and other waste products are only a few pollutants HMDScience.com that make their way into rivers, lakes, and aquifers all over the world. GO ONLINE Runoff from farms and cities may contain toxic chemicals and debris that Human Impact, Water can disrupt the chemical balance of freshwater lakes and streams and put entire Pollution freshwater ecosystems at risk. For example, detergents and fertilizers used in fields can affect a lake ecosystem by stimulating plant and algae overgrowth. A buildup FIGURE 3.1 A buildup of algae in of algae, such as the one shown in figure 3.1, can drastically lower the levels of lakes such as this one is the direct result of pollution. Eventually, the dissolved oxygen, leading to the dying off of fish populations. A lack of oxygen can process of eutrophication will lead also keep detritivores from breaking down waste materials. Over time, lakes and to the disappearance of the lake. ponds slowly begin to fill in through a process called eutrophication. One way in which scientists can determine the health of an ecosystem is through the study of natural indicator species. An indicator species, also known as a bioindicator, is a species that provides a sign, or indication, of the quality of the ecosystem’s environmental conditions. The gender-bending fish discussed above is an example of an aquatic indicator species. Frogs are sometimes considered an indicator species for water quality. Because the skin of tadpoles and adults is water-permeable, they come into direct contact with pollutants that can cause deformities such as extra arms and legs, as well as body tu- mors. Terrestrial ecosystems have indicator species as well, but the environmental impacts on these species are shown in different ways. Aquatic indicator species show the direct effects

of pollution. ©Chris Howes/Wild Places Photography/Alamy Images

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The Forster’s tern, a bird species native to coastal regions FIGURE 3.2 Biomagnification of the United States, has provided scientists with clues about pollution in the San Francisco Bay. This indicator species The movement of fat-soluble pollutants occupies a niche at the top of this ecosystem’s food web. An through a food chain results in higher important part of the tern’s diet is fish it catches in the San concentrations in the top consumer. Francisco Bay. By studying the tissues of dead tern chicks, herring gull eggs scientists are finding large amounts of chemical contaminants 124 ppm such as mercury and PCBs, or polychlorinated biphenyls. These chemicals can harm developing eggs and can cause problems in the nervous system of adult birds. The high levels of these pollutants found in birds could lead to a decrease in the tern population and disrupt the balance lake trout of this aquatic ecosystem. 4.83 ppm Apply If the population of an indicator species is increasing, what might you infer about the conditions of the ecosystem? 11B

11B, 12C, 12F MAIN IDEA smelt Biomagnification causes accumulation 1.04 ppm of toxins in the food chain. The high death rates in young Forster’s terns are due to high levels of toxic compounds found in the parents. How did these zooplankton chemicals get into the adult birds? 0.123 ppm Some pollutants are water-soluble, which means that they dissolve in water and will exit an organism through its wastes. Other pollutants are fat-soluble and stay in the body fat of an organism. Fat-soluble pollutants can also move from one phytoplankton organism to another in a process known as biomagnification. 0.025 ppm In biomagnification, a pollutant moves up the food chain as predators eat prey, accumulating in higher concentrations in ppm = parts per million the bodies of predators. Scientists measure pollutants in parts Connect Are humans likely affected by per million (ppm). The illustration in FIGURE 3.2 shows how biomagnification? If so, what foods might biomagnification moves small traces of a pollutant to higher be dangerous? 11B concentrations further up the food chain. After a pesticide is sprayed onto fields, large amounts of the chemical CONNECT TO are washed into ponds and lakes, where phytoplankton pick up the chemical Energy Pyramid from their environment. The phytoplankton contain very small concentra- In the chapter Principles of tions of the chemical, but when zooplankton feed on phytoplankton, they are Ecology, you learned how energy also eating the chemical. Because the zooplankton eat many phytoplankton, is lost as it moves up through trophic levels. In comparison, the higher levels of the chemical build up in the zooplankton. Secondary consum process of biomagnification ers such as small fish eat zooplankton and collect larger concentrations in increases toxic material as it their own body fat. Larger fish eat the chemical-laden fish, and the amount moves up the trophic structure. of the chemical in their fat builds up as they eat more and more. The increase in contamination is dramatic and causes the tertiary consumer at the top of the food chain, often a large predator such as an eagle or hawk, to receive the most concentrated dose of the pollutant.

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QUICK LAB modeling Modeling Biomagnification In this lab, you will model biomagnification. Small cups represent smelt, a fish that feeds on zooplankton. Medium-sized cups represent trout, which feed on smelt. The large cup represents an eagle, which feeds on trout. Problem How are contaminants magnified up the food chain? Materials Procedure • 4 small paper cups 1. Label the cups as smelt, trout, and eagle according to size. Punch holes in the • 2 medium paper cups bottom of each cup with the pencil. Cover the holes with masking tape. • 1 large paper cup 2. Fill each of the cups halfway with salt. Add 4 beads to each small cup. • marker • sharpened pencil 3. Hold each of the small cups over the beaker and remove the tape. Allow the salt • 10 cm masking tape to flow through the holes into the beaker. • 400 mL salt 4. Pour the remaining contents of two small cups into one medium cup. Pour the • 16 beads contents of the other two small cups into the second medium cup. Repeat step 3 • 500-mL beaker with the medium-sized cups. 5. Pour the remaining contents of both of the medium cups into the large cup.

Analyze and Conclude 1. Analyze What do the beads represent in this model of biomagnification? 2. Evaluate Why is the following statement true: “Carnivores at the top of the food chain tend to be most affected by pollutants released into the environment”?

Biomagnification has the most serious effect on species near the top of the food chain. For example, the beluga whale is a top predator that lives in cold Biology ocean waters and feeds on a wide variety of fish species. Studies of a beluga HMDScience.com whale population in eastern Canada have shown such extreme levels of toxic GO ONLINE chemicals that some whale carcasses have been treated as hazardous waste. Human Effects on a Food Web As top level consumers, humans can also be affected by biomagnification. Scientists have recently found small amounts of PCBs in the blood of newborn babies. Exposure to fat-soluble toxins such as PCBs during pregnancy and nursing can be dangerous to the developing fetus, and may also affect growth and development in young children. Compare Why would tertiary consumers have higher concentrations of toxins than primary consumers? 11B, 12F ©age fotostock/SuperStock

Self-check Online HMDScience.com 16.3 Formative Assessment GO ONLINE Reviewing Main Ideas Critical thinking CONNECT TO 1. What does an indicator species tell 3. Compare How are the concepts of Energy Pyramid us about the health of an ecosystem? carrying capacity and indicator 5. How does the 2. How do PCBs affect bird populations species related? biomagnification “pyramid” through biomagnification? 4. Synthesize Would a buffalo or a compare with the energy 11B mountain lion be more affected by pyramid? 12C biomagnification? Why? 12C

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CorrectionKey=A DO NOT EDIT--Changes must be made through “File info” info” “File through be made must EDIT--Changes DO NOT CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info” Unit 486 due to habitat destruction. in danger ofbecoming extinct this Knuckles leaf nestingfrog, are the SriLankanrain f FIGURE 4.1 FIGURE species introduced fragmentation habitat VOCABULARY ecosystem stability. environmental change can impact limited; 12Fdescribe how changing resource bases that are survival ofspeciesisdependenton 12D recognize that long-term organisms indifferent ecosystems; variations andadaptations of external factors; 12Bcompare and communities respond to analyze how organisms, populations,

5: 11Binvestigate and

Ecology 16.4

Rare frog speciesof 12F 11B, 12B, 12D, orests, suchas Threats to Biodiversity th of th P planet uniqueandmaintainsofecosystems. thestability think ofthediversity we experience each day. Thediversity makes ofEarth our you, every lunchisthesame day, and everyone listens to music.We thesame rarely one typeofflower, andonetype ofcar. Atschool all ofyour friendslook exactly like and interesting sights,you see only onetypeofeverything. There isonetypeoftree, Imagine yourself taking awalk down your favorite street. Butinstead ofbrightcolors Your to World Connect Ke reserving biodiversity is important to future the biodiversityreserving important is

y front, scientists inmany continue fields to get inspiration from nature. For ofhalf prescribed medicines are derived from plants. technological On the Biodiversity species. all affecting is foundation the of much of our world. ecosystem’s biodiversity have will aripple through entire effect the ecosystem, assortment of that species are found inany ecosystem. inan Adecrease ensures future the of Earth. world. The value of biodiversity is not just measured indollars. Biodiversity pollution problem are animal affecting and plant populations around the a population and threaten biodiversity. The loss of habitat and growing the changes.these Many times, human actions alter ecosystems inways that harm Ecosystems are constantly changing, and populations are always adjusting to reatens biodiversity. reatens MAI MAI C

o Man Bio Introduced speciescan disrupt stable relationships inanecosystem. Loss ofhabitat eliminates species. Preserving biodiversity to isimportant thefuture ofthebiosphere. N n N e biosphere. ID c diversity is diverse the world of living things—the array wide and ID y medical andy medical technological advancements come from nature. Nearly ep E E t A AS

The impact of a growing human population population human growing a of impact The for coating anew for implants. medical example, an adhesive from amussel as pattern the is beingused it more for difficult ecosystem the to handle future change. loss of biodiversity can reduce an ecosystem’s stability and make give little information other than where were they discovered. A is specimens afew dead inamuseum species extinct that can itgoes extinct, is gone forever. In many that all cases, remains of The l 11B, 12D, 12F oss of biodiversity has long-term When effects. aspecies

For example, as the nation of Sri Lanka has modernized, the natural CONNECT TO resources of the island have become increasingly depleted. Ninety-five percent Carbon Cycle of the island’s rain forests have been lost, and with them more than 19 differ- Rain forests around the world ent frog species have gone extinct. In addition, numerous other species, such play an integral role in Earth’s as the rare frog species shown in figure 4.1, are endangered. The loss of even a carbon cycle, storing large single species can harm the overall stability of an ecosystem. amounts of carbon in their structures. Biodiversity is highest in the rain forest biomes of the world, and these are the areas that are most threatened. Currently, about 1 percent of this biome is lost each year to logging or to clearing for agricultural use. Preserving the rain forests of the world will do a great deal to protect and preserve the biodiversity of our planet. Connect Why is biodiversity highest in tropical rain forests?

MAIN IDEA 11B, 12D, 12F Biology IDEO Loss of habitat eliminates species. V CLIP One way to protect species is to monitor and manage their numbers, and to HMDScience.com ensure they have adequate habitat for survival. Governments and organiza- GO ONLINE tions around the world are developing programs to protect species that are Loss of Biodiversity threatened by overhunting, overcollecting, and habitat loss. As the human population moves into what was formerly wilderness, people are moving into the territory of many species of wildlife. In many parts of the world, the loss of habitat can put species in danger of becoming extinct. Historically, for example, wetland habitats were viewed as breeding grounds FIGURE 4.2 By providing a safe for disease and as “wasted land.” Between the 1780s and the 1980s, more than way to cross barriers such as roads and highways, land bridges such as 53 percent of wetland habitat in the United States was eliminated. This de- this one in Canada allow animals struction displaced large numbers of wildlife and disrupted migration patterns to move safely from one part of for many species of water birds. their habitat to the next. Efforts to ensure adequate habitat must take into account the life history of the organism, including mating habits and migration patterns. Ecologists have become particularly worried about habitat fragmentation. Habitat fragmentation occurs when a barrier forms that prevents an organism from accessing its entire home range. Often, habitat fragmentation is caused by the building of roadways or the harvesting of forests. Bears, deer, raccoons, and opossums are just a few of the animals that find their home ranges fragmented as urban sprawl increases. To try to fix this growing problem, some states are building underpasses and overpasses so that wildlife can avoid busy roadways. Corridors such as the one shown in FIGURE 4.2 help to maintain continuous tracts of habitat for those species that move between different areas. Connect Why is wetland habitat important for migrating birds? 11B ©Joel Sartore

Chapter 16: Human Impact on Ecosystems 487 DO NOT EDIT--Changes must be made through “File info” CorrectionKey=A

MAIN IDEA 11B, 12B, 12D, 12F Introduced species can disrupt stable relationships in an ecosystem. Introduced species have a direct impact on the biodiversity and natural flow of energy in an ecosystem. An introduced species is any organism that was brought to an ecosystem as the result of human actions. Introduced species can pose a great threat to the stability of an ecosystem if they prey on or crowd out native species. In some instances, introduced species can cause economic damage. Just as native species interact with one another and their habitat, nonnative or introduced species are active and sometimes disruptive in their new ecosystems. Invasive species FIGURE 4.3 Mice plagues in Aus- are successful in environments under many circumstances. If an environment tralia and China can cost farmers has a niche that the invasive species can exploit, or if the invasive species is a millions of dollars in lost crops. better competitor in a particular niche, native species may be pushed out. Invasive species are also successful if there is a lack of predators to keep the population stable.

Web Effect on Native Species The Florida Everglades is a dynamic ecosystem where unique plants and ani- HMDScience.com mals have evolved for tens of thousands of years. The climate is similar to that of GO ONLINE a tropical jungle, and the Everglades can support a great diversity of organisms. Invasive Species One species that has been introduced to this region originally came from the tropical jungles of Southeastern Asia. The Burmese python, shown in figure 4.4, came to the United States as a pet species. Growing more than 6 meters (20 ft) in length, this massive snake can be difficult to care for. Irresponsible owners have released many of the snakes back into the wild. A large number of Burmese pythons have been captured and removed from Everglades National Park, and officials say that there is a good chance that a breeding population is present. As a constrictor species, the Burmese python feeds on small animals such as rats, birds, raccoons, and even dogs. Threats to endangered bird species in the park worry officials. As the python population begins to grow, endangered species protected in the Everglades could be affected.

FIGURE 4.4 Introduced species such as the Burmese python are growing in numbers in places like the Florida Everglades. (t) ©CSIRO (b) ©John Mitchell/Photo Inc. Researchers,

488 Unit 5: Ecology DO NOT EDIT--Changes must be made through “File info” CorrectionKey=A

Introduced animals are not the only problem. Plant species such as kudzu, another native of southeastern Asia, are invasive in the United States and are choking out native species of plants across the southeastern United States. The kudzu plant, shown in figure 4.5, was introduced in 1876 as an ornamental tropical houseplant enjoyed for its fragrant flowers and large leaves. It was planted as field cover to prevent soil loss from erosion, but it rapidly began to spread out of the fields. Cur- rently, kudzu is a classified as a problematic weed species in much of the eastern United States. Kudzu is a hardy plant, at home in virtually any soil, and it can grow up to 18 meters (60 ft) in a single growing season. This growth rate makes it FIGURE 4.5 After a few months difficult to control. Very few plant species can survive in an environment of being left in a single place, this once kudzu is introduced. By blanketing trees and shrubs with its large leaves, car has become covered with kudzu deprives other plants of the sunlight they need to survive. The plant is kudzu. Fast-growing kudzu can destroy natural habitats in just a resistant to most types of herbicides and can live for many years. few years. Economic Damage T’ ing! Invasive species can have a major impact on humans as well as ecosystems. A maz The common house mouse is an introduced species to the Australian conti- Video Inquiry nent. During the late 1700s, mice came from Europe as stowaways on British HMDScience.com cargo ships. Today, mice are considered a major pest species in Australia and GO ONLINE have caused widespread economic damage. Every four or five years, mice Killer Kitties populations increase exponentially. Seasons of heavy rainfall lead to bumper crops of corn and grain, causing a dramatic rise in mouse populations and leading to huge numbers of mice moving from one food source to another. It was estimated that during the 1993–1994 season, the mouse population in Australia cost farmers about $65 million in lost revenue. Mice continue to be a problem throughout the region. Predict How might a species of carnivorous fish introduced into a lake have a negative impact on the lake ecosystem? 12F ©Cameron Marlow Self-check Online HMDScience.com 16.4 Formative Assessment GO ONLINE Reviewing Main Ideas Critical thinking CONNECT TO 1. Give two reasons why biodiversity is 4. Analyze How could continued Population Growth important to humans. habitat fragmentation reduce 6. Using your knowledge of 2. How does habitat fragmentation biodiversity? 11B, 12F populations, describe what affect migrating bird populations? 5. Connect How might the introduc- will eventually happen to 11B, 12F tion of a mouse predator help with mouse populations in Australia as they run out 3. What types of damage can the mouse problem in Australia? of food. 12D, 12F introduced species cause? What problems might it cause? 12B, 12F 11B, 12F

Chapter 16: Human Impact on Ecosystems 489 CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info” Unit 490 FIGURE 5.1 FIGURE species umbrella development sustainable VOCABULARY impact ecosystem stability how environmental change can bases that are limited; 12Fdescribe dependent onchangingresource long-term survival ofspeciesis external factors; 12Drecognize that and communities respond to analyze ho demand for building materials. wood to thegrowing support provide anabundantsupply of in Chinagro

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investigate and w quickly andcan Forests ofbamboo 11b, 12 d Conservation , 12 f re present and future generations. future present and developmentSustainable manages resources for biosphere andto protect itfrom degradation. further Since then,avariety ofmeasures have beenputinto place, both to restore Earth’s public uproar andhelpedlead to abanontheuse ofDDT intheUnited States. which described how thepesticideDDT was affecting wildlife, brought abouta set inmotion for thecreation ofthemodernenvironmental movement. Thebook, When Rachel Carson’s bookSilent Springwas publishedin1962, thewheelswere Your to World Connect Ke

store ecosystems. store y for building supplies. Today, withawareness raised the of forest ecosystem removing entire forest ecosystems, lumber companies agrowing serve need clear cutting.called By cutting down large areas of sections wooded and for example, old growth forests are beinglost at afast rate due to amethod changes of inmethods harvesting natural resources. In industry, timber the Concerns aboutmethods. condition the of environment the have to led current needs without hurting future generations. is a practice in which natural resources are used and managed in a way that meets way of thinking is known as sustainable development. population, it is important future the to secure of Earth’s the ecosystems. This To ensure can that continue Earth to support, or sustain, agrowing human MAI MAI C

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range extends as far west as Texas and as far northas Virginia. alongOcean coast the of southeastern the United States. Their West Indian manatee. aquatic These mammals, shown in protected. be also other will Such species with the is case the figure umbrella species The benefit. ecosystemthe listed an is often also species called placed on alist of endangered many species, other within species its environment. When within asingle an species ecosystem is near extinction by establishing protection for organism the and for example, is to designed protect individual that species are habitats.their The Endangered Species Act United inthe States, Laws written to protect help individual also species to protect tofisheries sustainable: make industry the marine and environments. coastal Anumber of techniques adopted can be by no for fish future. the In addition, unsustainable fishing techniques damage is hurting actually industry itself. Without to fish reproduce now, be there will removing reproducing the individuals from population, the fishing the represent healthy, the reproducing age groups of population. fish the By hardy once as they were. One reason for is this that that fish the are caught has depletedOverfishing populations fish worldwide. Fish stocks are not as strategy accordingly to protect them. soil, water, and of and wildlife affected area the be change will harvest their choosing where and to when trees, harvest foresters must consider how the makes sure there is only minimal impact to forest the ecosystem. When clear-cutting forests. This practice encourages rapid regrowth of trees, and safety, companies several are choosing trees to rather cut selected than Harvest • Fishing • Rotation • Fishing • MAI struction have an effect on humans? humans? on have effect an struction Glo numbers innearby locations. replenish populations within that area, which may to lead greater fish prevent important ecologically organisms from beingkilled. banning fishing certain gear could help avoid and damaging floor sea the and often unintentionally catches and other possibly Reviewing species. totime recover numbers their following aharvest. very slowlyvery allows more them to time recover populations. their N

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tems can from benefit efforts to save from asingle species extinction. naturalthe habitat for manatees protected. is also As aresult, entire ecosys- restoring damaged areas, and limiting boating, marine the ecosystem that is resource must protected. be also By protecting waterways from pollution, manateesbecause rely on as main their source, seagrass food areas rich inthis endangered scientists species, must consider many factors. For example, velop policies to protect habitat. their When developing recovery plans for an promote state, local, survival, their and federal agencies are working to de- and feweris difficult, than 3000manatees remain United inthe States. To deaths due to collisions with powerboats. Today, situation the for manatees extinction, grewfrom 791pairs to almost 6500pairs in2000. Species Act was signed, breeding pairs ofonce eagle, bald the indanger of number of waterways that are safe today. Since Endangered the 1973,when against pollution and an increased public awareness have helped to double the safe for swimming. Since Water Clean the Act in1972,regulations was signed 36 percent of lakes the and waterways United inthe States were considered It regulates emissions from industrial factories and automobiles. In 1970,only intosigned law in1970,has helped to increase air quality across nation. the Species Act have had amajor impact on environment. the The Air Clean Act, States. Laws such asAir Clean the Act, Water Clean Act, and Endangered ment of policies and regulations to protect environment the across United the Environmental Policy Act in1970.Its creation paved way the for develop- the The Environmental Protection Agency was created of as part National the P future of our planet. resources public of Earth, actions are helping to and preserve protect the direct threatsthe our planet is facing. To prevent loss of further valuable the estimatedbeen over to be ayear. $30trillion on Earth’s it, total the value of services the natural ecosystems provide has sible for humans to manufacture. If we were to put ahuman economic value and regulation the of water provide essential resources that are almost impos- our planetvalue of provides services the is priceless. The cycling of nutrients livingAll things, including humans, share and its Earth resources, and the re e endangered grizzly bear of western western of bear grizzly e endangered MAI rotecting sulted from avariety of factors including loss of habitat, overhunting, and Clima The manatee was placedon endangered the list species in1967.Its listing

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CHAPTER display theeffects ofpollution. Concept Map 16.2 16.1 16 Unit 5:Ecol Key Con READING READING h smog and

acid rain warming. uting to rapid climate change, increasing global increased fossil fuelemissions appear to becontrib- the release ofenergy from Earth’s atmosphere. But dioxide, methane,andother greenhouse gases slow rain, whichboth threaten Earth’s ecosystems. Carbon processes are causing anincrease insmogandacid water, andsoil. Fossil fuelemissions from industrial is theaddition ofundesirable factors to theair, Fossil fuelemissions affect thebiosphere. Pollution footprint to sustainable levels. environments helpto will reduce ourecological needs ofourpopulation withtheresources ofour on renewable resources suchaswater. Balancing the nonrenewable resources suchasfossil fuelsaswell as technology. Butalarge population putspressure on has grown tremendously dueto advancements in Earth’s resources increases. Thehumanpopulation As thehumanpopulation grows, thedemandfor Air Quality Natural Resources leads to leads uman Popul ogy c S

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T and usingupresources. effect onecosystems by pushingoutnative species diversity. Nonnative speciescan have anegative aredestruction threatening bio- Habitat fragmentation and helps keep ecosystems stable. sity. Thebiodiversity ofaregion population threatens biodiver- The impact ofagrowing human systems, astoxins accumulate at thetop offood chains. biomagnification isathreat to both humansandeco- effects onanecosystem. ofpollution Theprocess of and health. Indicator specieshelpusunderstand the Pollution ofEarth’s freshwater supply threatens habitat species andthepositive ofgovernment support development. Inaddition, theprotection ofumbrella future generations, we needto plan for sustainable ecosystems. Conservation methodscan helpprotect andrestore Water Quality Conservation the sunare hreats to Biodiversity Human population growth threatens

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CHAPTER 16 G N I D A E R

D will bestsummarizethedefinition. will For each vocabulary term below, draw acartoon that

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w Cartoons introduced species global w ecologic indicat of theterm umbrella species? of theword umbrella relate to theecological meaning which means “shadow.” How doestheeveryday meaning The word greenhouse eff smog, acid r smog, the meaning oftheterm. Explain how themeanings oftheword make parts up comes from aLatin word meaning “great” or“large.” bio-, whichmeans “life,” andtheword magnify,which The term biomagnific which means “bel The word sustain comes from theLatin words sub-, renew sustainable development. hold.” Explain how these meanings relate to theterm

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States? use reflected intheecological footprint oftheUnited more waste thananyother country. How isthisresource The United Sta population growth? carbon dioxide impact thegreenhouse effect? atmosphere. How could theincrease inatmospheric earlier pr Earth’s humancarrying capacity hasexceeded many the bear belongs. grizzly bear may affect thelarger ecosystem to which umbrel AmericanThe North grizzly bear isconsidered an eco In what ways can anintroduced speciesimpact an preda How could theextinctionofasingle species,suchasa Explain. plankton-eating fish,oralarge fishthat eats smaller fish? toxins through biomagnification: plankton, asmall Which organism ismo mat Since the1970s, humanactivity hasreleased approxi- are theeff What are themajorcauses ofsmogandacid rain? What system ithascolonized? ely tons 150billion ofcarbon dioxide into the tory bird, affect anentire ecosystem? HMDScience.com Interact 12F la species.Explain how theprotection ofthe edictions. Howedictions. hastechnology affected human ects ofeachects typeofpollution?

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biomagnific indicator species introduc habitat fragmentation umbrel sustainable development i ve Review

IDEAS Chapter 16: HumanImpact onEcosystems Chapter 16: st likely to have accumulated la species 11B, 12D ed species ation 11B, 12F 11B, 12F 12F

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Critical Thinking 19. Analyze Assuming all other factors are the same, the Analyzing Data Identify Discrete and more meat in a person’s diet, the larger that person’s Continuous Data ecological footprint. Why might this be the case? 12F This circle graph shows the components of the ecological footprint for a resident of a North American city. Use 20. Connect Nationwide, automobiles are the major source the graph to answer the next two questions. of carbon monoxide, carbon dioxide, nitrogen oxides, particulate matter, and cancer-causing toxins. What can Ecological Footprint of a you do to decrease your fossil fuel use? North American City 21. Evaluate An ecological footprint is a measure of the 5.62% impact of the resources we use on the environment. Housing Explain how buying a carton of milk relates to your ecological footprint. 12F 20.93% Transportation 17.7% Food 22. Infer Frogs are commonly used as an indicator species in aquatic habitats. Could a large predator such as a bear Products/services or an eagle be used as an indicator species? Explain. 23.89% 31.86% Waste 23. Synthesize Explain how a predator insect species, introduced to help control insect pests, could become a threat to an ecosystem. 11B, 12F Interpreting Visuals Use the simple food web outlined below to answer the next three questions. 27. Apply Does the circle graph show discrete or continuous data? Explain. Otter Fox 28. Analyze In order of biggest to smallest impact, list the components of human activity that make up the average Tadpole Fish Turtle Duck ecological footprint, according to this graph.

Blue Jay Crayfish Making Connections Butterfly Minnow Cattail 29. Write a Scenario Imagine that successful efforts in sustainable development have made global resource use and waste production fully sustainable by the year 2099. Algae Write a few paragraphs that describe what a sustainable world might look like in 2099. Include information about 24. Apply Which of these organisms is likely to be most resource use, waste production, pollution, biodiversity, affected by biomagnification of toxins? Explain your and conservation. answer. 12C 30. Connect Look again at the damaged forest ecosystem 25. Predict This food web includes both aquatic and on the chapter opener. The emissions produced in this terrestrial organisms. Imagine that a new road separates region have led to the rapid decline in the biodiversity the aquatic environment from the nearby terrestrial of this area. How might this decline affect the resources environment. Do you think the turtle or the duck would of local animal populations? 11B, 12D, 12F be more affected by this habitat fragmentation? Explain. 12C

26. Predict Imagine that an introduced species results in the local extermination of crayfish. How might this change affect the larger ecosystem? 11B, 12F

496 Unit 5: Ecology Biology End-of-Course Exam Practice

Record your answers on a separate piece of paper. 11B MULTIPLE CHOICE 3 Which situation would most efficiently decrease the size of a field mouse population? 11b A decreased death rates and emigration 1 B decreased birth rates and immigration C increased death rates and immigration 100 150 Fox Lake 150 200 D increased death rates and emigration 50

150 THINK THROUGH THE QUESTION As you look at the answer choices, think carefully 100 about how each factor—birth rates, death rates, Bear Lake immigration, and emigration—affect population size. 50

The topographic map above shows the 9B, 12E watersheds, or regions that drain into Fox Lake 4 CO2 is important in our atmosphere because it is and Bear Lake. The watershed boundary, shown required for photosynthesis and it traps some with a dashed line, determines which lake water heat, keeping Earth warm. However, scientists will flow into. According to the map above, this speculate that excessive CO2 production is a boundary follows — problem because it — A the highest elevation points between the lakes A leads to higher global temperatures B the lowest elevation points between the lakes B disrupts the natural cycling of other greenhouse gases C a river that likely flows between the lakes C adds too much CO to the oceans D a path exactly halfway between the two lakes 2 D leads to uncontrolled photosynthesis

11B, 12A, 12F 11B, 12C 5 The nonnative zebra mussel was first found in a 2 lake near Detroit in 1988. By 1989, it had mammals colonized all Great Lakes waterways. Which f ish scenario is most likely true regarding the amphibians introduction of this species? A Native fish naturally eat zebra mussels. invertebrates B The higher biodiversity leads to healthier lakes. C They compete with native mussels for food terrestrial plants aquatic plants and other resources. D Native mussel populations are growing rapidly. A farmer sprays his crops with pesticide. The runoff enters a nearby lake. Based on the food web above, in which of the following organisms would the pesticide concentration be the highest? A cattail B largemouth bass C water striders D river otters

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UNIT 5: ecology 3D, 11B, 12F ZINE at HMDSCIENCE.COM BIOINternet MAGAZINE

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CNN As global temperatures rise and BBC arctic ice melts, polar bears are losing important hunting grounds.

Careers Climate Change— Bio Bytes Changing the Planet Polar bears are on the move. The area of Opinion Poll arctic sea ice on which these carnivores Strange Biology hunt seals has declined 34 percent as worldwide temperatures rise. As this ice is lost, polar bears must swim as far as 100 kilometers (about 60 mi) to find their prey. Some of these polar bears cannot make it, and they drown. Now polar bears must compete with grizzly bears. If climate change is changing the shape of one of Earth’s coldest regions, how will it affect the rest of our planet? (tr) Van ©Thomas Sant/Photo Inc. Nilsen/Photo Researchers, Inc.; Researchers, (bl) ©Tom

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Ecosystems at Risk 12F In the 20th century, the average global temperature TECHNOLOGY rose by 0.6ºC (1ºF). The difference may seem small,

but it is an average for the entire globe. Near the

poles, the effects of climate change are more dramat- Deep Sea Sediment Coring

ic. Since 1949, average annual temperatures in Alaska Analyzing ocean floor sediments can provide scientists

have risen 1.8ºC (3ºF)—enough to lengthen the with data about how plants and animals were affected during past climate changes. The process of collecting summer melting season for sea ice and glaciers. From deep sea sediments is expensive and time-consuming, but 1979 to 2007, Arctic sea ice retreated enough to the results of this research give scientists a look at what expose an additional one million square miles of life in the oceans was like millions of years ago. open water—the equivalent of six Californias. To study these ancient organisms, scientists need sediment samples that are hundreds of meters long. To Good and Bad News? 11B, 12F obtain these, they must use drills similar to the drills used In the rest of the world, the impact of climate change by the oil and gas industry. Taking these samples requires on Earth’s species may be mixed. Many animal many hours and can be dangerous if the seas are rough or species, such as birds and butterflies, can move to full of ice. Once scientists have obtained the cores, they cooler areas as the climate warms. But insects and first split the core in half lengthwise. One half is sampled microorganisms that cause infectious diseases, such for fossils of ancient organisms. This is the “working half.” The other half, the “archive half,” is saved and stored away as malaria and yellow fever, are also spreading toward so that future scientists who may develop other questions the poles. Some plant species cannot move as quickly can have access to this difficult-to-obtain material. as the climate is expected to change, and may become By carefully dissecting the working half of the sample, extinct. scientists discover microscopic fossils of marine animals. Researchers are also finding that changing tem- Scientists know that these ancient animals were very peratures can affect animals in surprising ways. The sensitive to slight changes in temperature and chemistry. sex of some reptiles, for example, is partially deter- These microfossils can tell scientists how Earth’s climate mined by the temperature of the developing egg. A has changed over millions of years. consistent warming trend could cause some reptiles Read More >> at HMDScience.com to become extinct by creating entire generations that are all the same sex. Migratory birds and marine mammals also face challenges. For example, birds These “working half” cores that wait until their normal migration time to fly will be carefully dissected and analyzed to better understand north in the spring may arrive too late, missing the Earth’s changing climate. best weeks for laying eggs and catching the insects they need to raise their young. In addition, some researchers have predicted that the productivity of phytoplankton, the algae on which ocean food webs are based, may decline in some areas. A change of this sort could cause a domino effect in marine food webs. If phytoplankton levels decline, fish will have less food and will be less numerous. If fish are less numerous, marine mammals and birds will have less to eat too. In addition, studies show that this increase in global temperatures is linked to a four percent increase in ocean humidity and a six to eight percent increase in rainfall, leading to stronger hurricanes. ©AP/Wide World World Photos/ ©AP/Wide Katsumi Kasahara

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UNIT 5 BioZine CAREERS

Oceanographer in Action Ruth Curry TITLE Oceanographer, Woods Hole Oceanographic Institution

EDUCATION B.S., Geology, Brown University

For Ruth Curry, spending time on the ocean waves has Computer modeling programs such as this one work to pre- nothing to do with surfing or vacationing. She spends dict the effects of climate change by simulating different temperature increases. her time studying the ocean currents that affect our lives each day. Ruth Curry is an oceanographer at the But the news may not be all bad. Some of the same Woods Hole Oceanographic Institute, an organization research shows that the same factors that increase the of scientists who research and study how the ocean affects the global environment. strength of a hurricane also make it less likely that the hurricane will ever make landfall. The retreat of Curry’s research focuses on the North Atlantic Arctic sea ice may someday make it possible to open circulation and the currents that carry warm waters from tropical regions northward. As these warm waters a shipping lane through the Arctic Ocean. reach higher latitudes, they release heat that warms the Scientists theorize that climate change has been air above them and warms the climate of western accelerated by increased levels of carbon dioxide in Europe. As warm water cools, its density increases and the atmosphere. Many plants, including crops such as it sinks to the bottom of the ocean. There it begins a cotton, soybeans, wheat, and rice, can benefit from southward journey back to the tropics. This conveyor

the increase in CO2. They can absorb the CO2 and belt of water plays an important role in maintaining yield more at harvest time as a result. On the other Earth’s climate. Normally, the salinity, or saltiness, of hand, in warmer weather crops may also be more at ocean water stays about the same. But changes in risk from insect pests and from severe storms or global temperatures are melting large sheets of ice in droughts. Greenland, which is introducing large amounts of fresh water into the ocean. This fresh water is diluting the ocean water, making it less salty. A decrease in salinity Unanswered Questions 3D, 12F makes ocean waters less dense and prevents them Scientists have little doubt that Earth’s climate is from sinking to the bottom of the ocean. Eventually, changing. It is impossible to predict exactly how any the melting of ice sheets in Greenland could cause the ecosystem will be affected by climate change. How- North Atlantic currents to slow and eventually stop, ever, biologists and climatologists are collecting data leading to dramatic changes in the Northern about processes, including solar radiation, precipita- Hemisphere’s climate. tion, evaporation, the transfer of heat by winds and Read More >> at HMDScience.com by ocean currents, and the ways in which plants affect climate. They interpret this information using • How have global climate changes affected Earth’s computer models and try to answer questions about ecosystems in the past? how climate change will affect Earth. • Is there a way to preserve biodiversity on mountain • Could climate change alter certain ocean currents, tops and polar areas where animals and plants have changing Earth’s temperatures further? no cooler places to migrate to?

• How quickly might the polar ice caps melt? Read More >> at HMDScience.com (tl) ©Peter Essick/Aurora/Getty Images;Kleindinst/Woods Hole (tr) Oceanographic ©Tom Institution

500 Unit 5: Ecology