Unit 3 Science (Glencoe Red 2002)

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Unit 3 Science (Glencoe Red 2002)

  1. 1. UNIT 3 Life and the Environment How Are Beverages & Wildlife Connected?212
  2. 2. I n ancient times,people transported beverages in clay jars and animal skins.Around 100 BC, hand-blown glass bottles began to be used to hold liquids.In 1903, the invention of theautomatic glass bottle-blowing machine made it possible to mass-produce bottles.They wereused for everything from milk to soda.Consumers returned the empty bottles to berefilled.In 1929, companies began experimenting with cans for bever-ages.Cans were stackable,non-breakable,and fast cooling—andconsumers didn’t have to return them.The plastic six-pack yokecame along with the popular use of cans for beverages.Thisdevice bound cans together for easy carrying.Unfortu-nately,the yokes bound more than cans.Millions of yokesfound their way into the environment where theyentangled thousands of birds,fish, and marine animals.Today,animals are still being harmed—in some casesthey are killed—by plastic six-pack yokes. SCIENCE CONNECTION REDUCE, REUSE, RECYCLE Look at the packaging on the things you eat, your crafts or hobbies, or the products used in your home. Work with a partner to design a more eco-friendly package for one of these products. Make a drawing of your new packaging and write a paragraph telling why your package is environmentally friendly. Share your drawings and paragraphs with your school or community through a bulletin board.
  3. 3. 8 Interactions of Living ThingsH ow do Alaskan brown bears and salmon interact? The relationship between thesetwo species is clear to see. However,the Alaskan brown bear also dependson every species of insect and fishthat the salmon eats, and many non-living parts of the environment, too.In this chapter, you will learn how allliving things depend on the living andnonliving factors in the environmentfor survival.What do you think?Science Journal Look at the picturebelow with a classmate. Discuss whatyou think this might be. Here’s a hint:This species and salmon interact. Writeyour answer or best guess in yourScience Journal.214
  4. 4. EXPLORE I magine that you are in a crowded elevator. Every- one jostles and bumps each other. The temperature ACTIVITY increases and ordinary noises seem louder. What a relief you feel when the doors open and you step out. Like people in an elevator, plants and animals in an area interact. How does the amount of space available to each organism affect its interaction with other organisms? Measure space MXXX-??P 1. Use a meterstick to measure theDescription length and width of the classroom. 2. Multiply the length by the width to find the area of the room in square meters. 3. Count the number of individuals in your class. Divide the area of the classroom by the number of individuals. In your Science Journal, record how much space each person has. Observe Write a prediction in your Science Journal about what might happen if the number of students in your classroom doubled. FOLDABLES Reading &Study & Study Making a Cause and Effect Study Fold Make this Foldable to Skills help you understand the cause and effect relationship of biotic and abiotic things. 1. Place a sheet of paper in front of you so the long side is at the top. Biotic Fold the paper in half from the left side to the right side. Fold top to bottom and crease. Then unfold. 2. Through the top thickness of paper, cut along the middle fold line to form two tabs as shown. Label the tabs Biotic, which means Abiotic living, and Abiotic, which means nonliving, as shown. 3. Before you read the chapter, list examples of biotic and abiotic things around you on the tabs. As you read, write about each under the tabs. 215
  5. 5. SECTION The Environment Ecology All organisms, from the smallest bacteria to a blue whale,s Identify biotic and abiotic factors interact with their environment. Ecology is the study of the in an ecosystem. interactions among organisms and their environment. Ecolo-s Describe the different levels of gists, such as the one in Figure 1, are scientists who study these biological organization. relationships. Ecologists divide the environmental factors thats Explain how ecology and the envi- ronment are related. influence organisms into two groups. Abiotic (ay bi AH tihk) factors are the nonliving parts of the environment. Living orVocabulary once-living organisms in the environment are called bioticecology communityabiotic factor ecosystem (bi AH tihk) factors.biotic factor biospherepopulation Why is a rotting log considered a biotic factor in the environment?Abiotic and biotic factors interact tomake up your ecosystem. The quality Abiotic Factorsof your ecosystem can affect your In a forest environment, birds, insects, and other livinghealth. Your actions can affect the things depend on one another for food and shelter. They alsohealth of the ecosystem. depend on the abiotic factors that surround them, such as water, sunlight, temperature, air, and soil. All of these factors and oth- ers are important in determining which organisms are able to live in a particular environment.Figure 1Ecologists study biotic and abiotic factors inan environment and the relationships amongthem. Many times, ecologists must travel tospecific environments to examine the organ-isms that live there.216 CHAPTER 8 Interactions of Living Things
  6. 6. 100 97% The seas and oceans are homeWorld‘s Water Supply (%) 80 to thousands of different species. 60 40 This stream is a freshwater 20 environment. It is home to many species of plants 3% and animals. 0 Salt water FreshwaterWater All living organisms need water to survive. The bodies Figure 2of most organisms are 50 percent to 95 percent water. Water is an Salt water accounts for 97 per-important part of the cytoplasm in cells and the fluid that sur- cent of the water on Earth. It isrounds cells. Respiration, photosynthesis, digestion, and other found in the seas and oceans.important life processes can only occur in the presence of water. Only three percent of Earth’s More than 95 percent of Earth’s surface water is found in the water is freshwater.oceans. The saltwater environment in the oceans is home to avast number of species. Freshwater environments, like the one inFigure 2, also support thousands of types of organisms.Light and Temperature The abiotic factors of light andtemperature also affect the environment. The availability of sun- Figure 3light is a major factor in determining where green plants and Flowers that grow on the forestother photosynthetic organisms live, as shown in Figure 3. By floor, such as these bluebells,the process of photosynthesis, energy from the Sun is changed grow during the spring wheninto chemical energy that is used for life processes. Most green they receive the most sunlight.algae live near the water’s surface where sun-light can penetrate. On the other hand, littlesunlight reaches the forest floor, so very fewplants grow close to the forest floor. The temperature of a region also deter-mines which plants and animals can livethere. Some areas of the world have a fairlyconsistent temperature year round, but otherareas have seasons during which tempera-tures vary. Water environments throughoutthe world also have widely varied tempera-tures. Plant and animal species are found inthe freezing cold Arctic, in the extremely hotwater near ocean vents, and at almost everytemperature in between. SECTION 1 The Environment 217
  7. 7. Figure 4Air pollution can come frommany different sources. Airquality in an area affects thehealth and survival of the speciesthat live there. Air Although you can’t see the air that surrounds you, it has an impact on the lives of most species. Air is composed of a mix- ture of gases including nitrogen, oxygen, and carbon dioxide. When soil that receives little Most plants and animals depend on the gases in air for respira- rain is damaged, a desert tion. The atmosphere is the layer of gases and airborne particles can form. This process is called desertification. Use that surrounds Earth. Polluted air, like the air in Figure 4, can reference materials to find cause the species in an area to change, move, or die off. where desertification is Clouds and weather occur in the bottom 8 km to 16 km of occurring in the United the atmosphere. All species are affected by the weather in the area States. Record your findings where they live. The ozone layer is 20 km to 50 km above Earth’s in your Science Journal. surface and protects organisms from harmful radiation from the Sun. Air pressure, which is the weight of air pressing down on Earth, changes depending on altitude. Higher altitudes have less air pressure. Few organisms live at extreme air pressures.Figure 5 How does air pollution affect the species in anSoil provides a home for many area?species of animals. Soil From one enviroment to another, soil, as shown in Figure 5, can vary greatly. Soil type is determined by the amounts of sand, silt, and clay it contains. Various kinds of soil contain different amounts of nutrients, minerals, and moisture. Dif- ferent plants need different kinds of soil. Because the types of plants in an area help determine which other organisms can survive in that area, soil affects every organism in an environment. Biotic Factors Abiotic factors do not provide everything an organism needs for survival. Organisms depend on other organisms for food, shelter, protection, and reproduction. How organisms interact with one another and with abiotic factors can be described in an organized way.218 CHAPTER 8 Interactions of Living Things
  8. 8. Levels of Organization The living world is highly organ-ized. Atoms are arranged into molecules, which in turn areorganized into cells. Cells form tissues, tissues form organs, andorgans form organ systems. Together, organ systems form Figure 6organisms. Biotic and abiotic factors also can be arranged into The living world is organizedlevels of biological organization, as shown in Figure 6. in levels. Organism An organism is one individual from a population. Population All of the indi- viduals of one species that live in the same area at the same time make up a population. Community The populations of different species that interact in some way are called a community. Ecosystem All of the communities in an area and the abiotic factors that affect them make up an ecosystem. Biome A biome is a large region with plants and animals well adapted to the soil and climate of the region. Biosphere The level of biological organization that is made up of all the ecosystems on Earth is the biosphere. SECTION 1 The Environment 219
  9. 9. Populations All the members of one species that live together make up a population. For example, all of the catfish living in a lake at the same time make up a population. Part of a popula- tion of penguins is shown in Figure 7. Members of a population compete for food, water, mates, and space. The resources of the environment and the ways the organisms use these resources determine how large a population can become. Communities Most populations of organisms do not live alone. They live and interact with populations of other types of organisms. Groups of populations that interact with each other in a given area form a community. For example, a population ofFigure 7 penguins and all of the species that they interact with form aMembers of a penguin popula- community. Populations of organisms in a community dependtion compete for resources. on each other for food, shelter, and other needs. Ecosystem In addition to interactions among populations, ecologists also study interactions among populations and their physical surroundings. An ecosystem like the one in Figure 8A is made up of a biotic community and the abiotic factors that affect it. Examples of ecosystems include coral reefs, forests, and ponds. You will learn more about the interactions that occur in Research Visit the ecosystems later in this chapter. Glencoe Science Web site at science.glencoe.com Biomes Scientists divide Earth into different regions called for more information about biomes. A biome (BI ohm) is a large region with plant and ani- Earth’s biomes. Make a poster mal groups that are well adapted to the soil and climate of the to communicate to your class region. Many different ecosystems are found in a biome. Exam- what you learn. ples of biomes include mountains, as shown in Figure 8B, tropi- cal rain forests, and tundra.Figure 8Biomes contain manydifferent ecosystems. This mountaintopecosystem is part of the mountain biome.220 CHAPTER 8 Interactions of Living Things
  10. 10. 80° Arctic Ocean Ice Tundra Arctic Circle Arctic Circle Taiga 60° Grassland ASIA NORTH Temperate Atlantic EUROPE Forests AMERICA Ocean Pacific Tropical Ocean Rainforest 30° Tropic of Cancer Chaparral Pacific Savanna Ocean AFRICA Desert Equator Equator 0° Mountain SOUTH Atlantic Indian AMERICA Ocean Tropic of Capricorn Ocean 30° AUSTRALIA Antarctic Ocean 60° Antarctic CircleThe Biosphere Where do all of Earth’s organisms live? Living Figure 9things can be found 11,000 m below the surface of the ocean This map shows some of theand on mountains as high as 9,000 m. The part of Earth that major biomes of the world. Whatsupports life is the biosphere (BI uh sfihr). The biosphere biome do you live in?includes the top part of Earth’s crust, all the waters that coverEarth’s surface, the surrounding atmosphere and all biomes, asshown in Figure 9. The biosphere seems huge, but it is only asmall part of Earth. If you used an apple as a model of Earth, thethickness of Earth’s biosphere could be compared to the thick-ness of the apple’s skin. Section Assessment 1. What is the difference between an abiotic factor and a biotic factor? Give five exam- 6. Recording Observations Each person lives in ples of each that are in your ecosystem. a population as part of a community. Describe 2. Contrast a population and a community. your population and community. For more 3. What is an ecosystem? help, refer to the Science Skill Handbook. 4. How are the terms ecology and environment 7. Using a Database Use a database to research related? biomes. Find the name of the biome that best 5. Think Critically Explain how biotic factors describes where you live. For more help, refer change in an ecosystem that has flooded. to the Technology Skill Handbook. SECTION 1 The Environment 221
  11. 11. Delicately Balanced Ecosystems E ach year you might visit the same park, but notice little change. However, ecosystems are delicately balanced, and small changes can upset this balance. In this activity, you will observe how small amounts of fertilizer can disrupt an ecosystem. What You’ll Investigate How do manufactured fertilizers affect pond systems? 5. Cover each jar with plastic wrap and secure it Materials with a rubber band. Use your pencil to punch large glass jars of rubber bands (4) three small holes through the plastic wrap. equal size (4) pond water 6. Place all jars in a well-lit area. clear plastic wrap triple beam balance stalks of Elodea (8) weighing paper 7. Make daily observations of the jars for three *another aquatic plant spoon weeks. Record your observations in your garden fertilzer metric ruler Science Journal. *houseplant fertilizer *Alternate materials 8. At the end of the three-week period, remove the Elodea stalks. Measure and record the Goals length of each in your Science Journal. s Observe the effects of manufactured fertilizer on water plants. s Predict the effects of fertilizers on pond Conclude and Apply and stream ecosystems. 1. List the control and variables you used in this experiment. Safety Precautions 2. Compare the growth of Elodea in each jar. 3. Predict what might happen to jar A if you added 5 g of fertilizer to it each week. Procedure 1. Working in a group, label four jars A, B, C, and D. 2. Measure eight Elodea stalks to be certain Compare your results with the results of other that they are all about equal in length. students. Research how fertilizer runoff 3. Fill the jars with pond water and place two from farms and lawns has affected aquatic stalks of Elodea in each jar. ecosystems in your area. For more help, 4. Add 5 g of fertilizer to jar B, 10 g to jar C, refer to the Science Skill Handbook. and 30 g to jar D. Put no fertilizer in jar A.222 CHAPTER 8 Interactions of Living Things
  12. 12. SECTION Interactions Among Living OrganismsCharacteristics of Populations You, the person sitting next to you, everyone in your class,and every other organism on Earth is a member of a specific s Identify the characteristics thatpopulation. Populations can be described by their characteristics describe populations.such as spacing and density. s Examine the different types of relationships that occur among populations in a community.Population Size The number of individuals in the popula- s Determine the habitat and nichetion is the population’s size, as shown in Figure 10. Population of a species in a community.size can be difficult to measure. If a population is small and Vocabularymade up of organisms that do not move, the size can be deter- population density nichemined by counting the individuals. Usually individuals are too limiting factor habitatwidespread or move around too much to be counted. The pop- symbiosisulation size then is estimated. The number of organisms of onespecies in a small section is counted and this value is used toestimate the population of the larger area. You must interact with other Suppose you spent several months observing a population of organisms to survive.field mice that live in a pasture. You probably would observechanges in the size of the population. Older mice die. Mice areborn. Some are eaten by predators, and some mice wander awayto new nests. The size of a population is always changing. Therate of change in population sizevaries from population to popula- World population: 1950–2050 (projected)tion. In contrast to a mouse popula- 10tion, the number of pine trees in a 9 Human population (billions)mature forest changes slowly, but a 8forest fire could reduce the pine tree 7population quickly. 6 5 4 3 2Figure 10 1The size of the human population is 0 1960 1980 2000 2020 2040increasing each year. By the year 2050, Yearthe human population is projected to bemore than 9 billion. Source: U.S. Census Bureau, International Data Base 5-10-00. SECTION 2 Interactions Among Living Organisms 223
  13. 13. Figure 11Population density can be shown C A N A D Aon a map. This map uses differ-ent colors to show varying densi- Pacific Oceanties of a population of northernbobwhite birds. U N I T E D S T A T E S Average Count per km2 <1 1–3 Atlantic 4–10 Ocean 11–30 31–100 > 100 Research Visit the Glencoe Science Web site at science.glencoe.com Population Density At the beginning of this chapter, when for recent news about the size you figured out how much space is available to each student in of the human population. your classroom, you were measuring another population char- Communicate to your class acteristic. The number of individuals in a population that what you learn. occupy a definite area is called population density. For example, if 100 mice live in an area of one square kilometer, the popula- tion density is 100 mice per square kilometer. When more indi- viduals live in a given amount of space, as seen in Figure 11, the population is more dense.Figure 12In some populations, such as Population Spacing Another characteristic of populationscreosote bushes in the desert, is spacing, or how the organisms are arranged in a given area.individuals usually are spaced They can be evenly spaced, randomly spaced, or clumpeduniformly throughout the area. together. If organisms have a fairly consistent distance between them, as shown in Figure 12, they are evenly spaced. In random spacing, each organism’s location is inde- pendent of the locations of other organisms in the population. Random spac- ing of plants usually results when wind or birds dis- perse seeds. Clumped spac- ing occurs when resources such as food or living space are clumped. Clumping results when animals gather in herds, flocks, or other groupings.224 CHAPTER 8 Interactions of Living Things
  14. 14. Limiting Factors Populations cannot continue togrow larger forever. All ecosystems have a limitedamount of food, water, living space, mates, nestingsites, and other resources. A limiting factor, as shownin Figure 13, is any biotic or abiotic factor that limitsthe number of individuals in a population. A limitingfactor also can affect other populations in the com-munity indirectly. For example, a drought mightreduce the number of seed-producing plants in a for-est clearing. Fewer plants means that food canbecome a limiting factor for deer that eat the plantsand for a songbird population that feeds on the seedsof these plants. Food also could become a limitingfactor for hawks that feed on the songbirds. What is an example of a limiting factor? Figure 13 These antelope and zebra popu- Competition is the struggle among organisms to obtain the lations live in the grasslands ofresources they need to survive and reproduce, as shown in Africa. What limiting factors mightFigure 14. As population density increases, so does competition affect the plant and animal popu-among individuals for the resources in their environment. lations shown here?Carrying Capacity Suppose a population increases in sizeyear after year. At some point, food, nesting space, or otherresources become so scarce that some individuals are not able tosurvive or reproduce. When this happens, the environment hasreached its carrying capacity. Carrying capacity is the largestnumber of individuals of a species that an environment cansupport and maintain for a long period of time. If a populationgets bigger than the carrying capacity of the environment, someindividuals are left without adequate resources. They will die or What insect populations live inbe forced to move elsewhere. your area? To find out more about insects, see the Insect Field Guide at the back of the book. Figure 14 During dry summers, the popula- tions of animals at existing watering holes increase because some watering holes have dried up. This creates competition for water, a valuable resource. SECTION 2 Interactions Among Living Organisms 225
  15. 15. Biotic Potential What would happen if a population’s envi- ronment had no limiting factors? The size of the population would continue to increase. The maximum rate at which a pop- ulation increases when plenty of food and water are available, the weather is ideal, and no diseases or enemies exist, is its biotic potential. Most populations never reach their biotic potential, or they do so for only a short period of time. Eventually, the carry-Observing Symbiosis ing capacity of the environment is reached and the populationProcedure stops increasing.1. Carefully wash and examine the roots of a legume plant and a nonlegume plant. Symbiosis and Other Interactions2. Use a magnifying glass to In ecosystems, many species of organisms have close rela- examine the roots of the tionships that are needed for their survival. Symbiosis (sihm legume plant. bee OH sus) is any close interaction between two or more differ-Analysis ent species. Symbiotic relationships can be identified by the type1. What differences do you of interaction between organisms. A symbiotic relationship that observe in the roots of the benefits both species is called mutualism. Figure 15 shows one two plants?2. Bacteria and legume plants example of mutualism. help one another thrive. Commensalism is a form of symbiosis that benefits one What type of symbiotic rela- organism without affecting the other organism. For example, a tionship is this? species of flatworms benefits by living in the gills of horseshoe crabs, eating scraps of the horseshoe crab’s meals. The horseshoe crab is unaffected by the flatworms. Parasitism is a symbiotic relationship between two species in which one species benefits and the other species is harmed. Some species of mistletoe are parasites because their roots grow into a tree’s tissue and take nutrients from the tree. What are some examples of symbiosis? The yucca depends on theFigure 15 moth to pollinate its flowers.The partnership between thedesert yucca plant and the yuccamoth is an example of mutualism. The moth depends on the yucca for protected place to lay its eggs and a source of food for its larvae.226 CHAPTER 8 Interactions of Living Things
  16. 16. Predation One way that populationsize is regulated is by predation (prih DAYshun). Predation is the act of one organ-ism hunting, killing, and feeding onanother organism. Owls are predators ofmice, as shown in Figure 16. Mice aretheir prey. Predators are biotic factors thatlimit the size of the prey population.Availability of prey is a biotic factor thatcan limit the size of the predator popula-tion. Because predators are more likely tocapture old, ill, or young prey, thestrongest individuals in the prey popula-tion are the ones that manage to repro-duce. This improves the prey populationover several generations.Habitats and Niches In a commu-nity, every species plays a particular role.For example, some are producers andsome are consumers. Each also has a par-ticular place to live. The role, or job, of an organism in the Figure 16ecosystem is called its niche (NICH). What a species eats, how it Owls use their keen senses ofgets its food, and how it interacts with other organisms are all sight and hearing to hunt forparts of its niche. The place where an organism lives is called its mice in the dark.habitat. For example, an earthworm’s habitat is soil. An earth-worm’s niche includes loosening, aerating, and enriching thesoil. Section Assessment 1. Name three characteristics of populations. 2. Describe how limiting factors can affect 6. Drawing Conclusions Explain how sound the organisms in a population. could be used to relate the size of the cricket 3. Explain the difference between a habitat population in one field to the cricket population and a niche. in another field. For more help, refer to the 4. Describe and give an example of two Science Skill Handbook. symbiotic relationships that occur among 7. Solving One-Step Equations A 15-m2 populations in a community. wooded area has the following: 30 ferns, 150 5. Think Critically A parasite can obtain grass plants, and 6 oak trees. What is the popula- food only from its host. Most parasites tion density per m2 of each species? For more weaken but do not kill their hosts. Why? help, refer to the Math Skill Handbook. SECTION 2 Interactions Among Living Organisms 227
  17. 17. SECTION Matter and Energy Energy Flow Through Ecosystems Life on Earth is not simply a collection of independents Explain the difference between a organisms. Even organisms that seem to spend most of their food chain and a food web. time alone interact with other members of their species. Theys Describe how energy flows also interact with members of other species. Most of the interac- through ecosystems. tions among members of different species occur when ones Examine how materials such as water, carbon, and nitrogen are organism feeds on another. Food contains nutrients and energy used repeatedly. needed for survival. When one organism is food for another organism, some of the energy in the first organism (the food) isVocabulary transferred to the second organism (the eater).food chain water cyclefood web Producers are organisms that take in and use energy from the Sun or some other source to produce food. Some use the Sun’s energy for photosynthesis to produce carbohydrates. ForYou are dependent upon the recy- example, plants, algae, and some one-celled, photosyntheticcling of matter and the transfer of organisms are producers. Consumers are organisms that take inenergy for survival. energy when they feed on producers or other consumers. The transfer of energy does not end there. When organisms die, other organisms called decomposers, as shown in Figure 17, take in energy as they break down the remains of organisms. This movement of energy through a community can be dia-Figure 17 grammed as a food chain or a food web.These mushrooms are decom-posers.They obtain needed Food Chains A food chain, as shown in Figure 18, is aenergy for life when they break model, a simple way of showing how energy, in the form ofdown organic material. food, passes from one organism to another. When drawing a food chain, arrows between organisms indicate the direction of energy transfer. An example of a pond food chain follows. small water plants → insects → bluegill → bass Food chains usually have three or four links. This is because the available energy decreases from one link to the next link. At each transfer of energy, a portion of the energy is lost as heat due to the activities of the organisms. In a food chain, the amount of energy left for the last link is only a small portion of the energy in the first link.228
  18. 18. VISUALIZING A FOOD CHAINFigure 18 E The last link in many food chains isI n nature, energy in food passes from one organism a top carnivore, an animal that feeds on to another in a sequence other animals, including other carnivores.known as a food chain. All living This great horned owl is a top carnivore.things are linked in food chains,and there are millions of differ-ent chains in the world. Eachchain is made up of organisms D The fourth linkin a community. The photo- of this food chain isgraphs here show a food a garter snake, whichchain in a North American feeds on toads.meadow community. A The first link inany food chain is aproducer—in thiscase, grass. Grassgets its energyfrom sunlight. B The second link of a food chain is usually an herbivore like this grasshopper. Herbivores are animals that feed only on producers. C The third link of this food chain is a carnivore, an animal that feeds on other animals. This wood- house toad feeds on grasshoppers. SECTION 3 Matter and Energy 229
  19. 19. Food Webs Food chains are too simple to describe the many interactions among organisms in an ecosystem. A food web is a series of overlapping food chains that exist in an ecosystem. A food web provides a more complete model of the way energy moves through an ecosystem. They also are more accurate mod- els because food webs show how many organisms are part of more than one food chain in an ecosystem. Humans are a part of many different food webs. Most peo- ple eat foods from several different levels of a food chain. Every time you eat a hamburger, an apple, or a tuna fish sandwich, you have become a link in a food web. Can you picture the steps in the food web that led to the food in your lunch? Problem-Solving ActivityHow do changes in Antarctic food websaffect populations? he food webs in the icy Antarctic Ocean How would changes in any of these popula-T are based on phytoplankton, which aremicroscopic algae that float near the water’s tions affect the other populations?surface. The algae are eaten by tiny, shrimp- Identifying the Problemlike krill, which are consumed by baleen Worldwide, the hunting of baleen whaleswhales, squid, and fish. Toothed whales, has been illegal since 1986. It is hoped thatseals, and penguins eat the fish and squid. the baleen whale population will increase. How will an increase in the whale popula- tion affect this food web? Solving the Problem 1. Populations of seals, penguins, and krill- eating fish increased in size as popula- tions of baleen whales declined. Explain why this occurred. 2. What might happen if the number of baleen whales increases but the amount of krill does not?230 CHAPTER 8 Interactions of Living Things
  20. 20. Ecological Pyramids Most of the energy in the biospherecomes from the Sun. Producers take in and transform only asmall part of the energy that reaches Earth’s surface. When anherbivore eats a plant, some of the energy in the plant passes tothe herbivore. However, most of it is given off into the atmo-sphere as heat. The same thing happens when a carnivore eats aherbivore. An ecological pyramid models the number of organ-isms at each level of a food chain. The bottom of an ecological Certain bacteria take in energy through a processpyramid represents the producers of an ecosystem. The rest of called chemosynthesis. Inthe levels represent successive consumers. chemosynthesis, the bac- teria produce food using What is an ecological pyramid? the energy in chemical compounds. In your Science Journal predictEnergy Pyramid The flow of energy from grass to the hawk where these bacteriain Figure 19 can be illustrated by an energy pyramid. An energy are found.pyramid compares the energy available at each level of the foodchain in an ecosystem. Just as most food chains have three orfour links, a pyramid of energy usually has three or four levels.Only about ten percent of the energy at each level of the pyra-mid is available to the next level. By the time the top level isreached, the amount of energy available is greatly reduced. Figure 19 An energy pyramid illustrates that available energy decreases at each successive feeding step. Why doesn’t an energy pyramid have more levels? SECTION 3 Matter and Energy 231
  21. 21. The Cycles of Matter The energy available as food is constantly renewed by plants using sunlight. However, think about the matter that makes up the bodies of living organisms. The law of conservation of massModeling the states that matter on Earth is never lost or gained. It is used overWater Cycle and over again. In other words, it is recycled. The carbon atomsProcedure in your body might have been on Earth since the planet formed1. With a marker, make a line billions of years ago. They have been recycled billions of times. halfway up on a plastic cup. Many important materials that make up your body cycle Fill the cup to the mark with through the environment. Some of these materials are water, water. carbon, and nitrogen.2. Cover the top with plastic wrap and secure it with a rubber band or tape. Water Cycle Water molecules on3. Put the cup in direct sun- Earth constantly rise into the atmo- light. Observe the cup for sphere, fall to Earth, and soak into three days. Record your the ground or flow into rivers and oceans. The water cycle observations. involves the processes of evaporation, condensation, and precip-4. Remove the plastic wrap itation. and observe the cup for Heat from the Sun causes water on Earth’s surface to evapo- seven more days. rate, or change from a liquid to a gas, and rise into the atmo-Analysis sphere as water vapor. As the water vapor rises, it encounters1. What parts of the water cycle did you observe colder and colder air and the molecules of water vapor slow during this activity? down. Eventually, the water vapor changes back into tiny2. How did the water level in droplets of water. It condenses, or changes from a gas to a liquid. the cup change after the These water droplets clump together to form clouds. When the plastic wrap was removed? droplets become large and heavy enough, they fall back to Earth as rain or other precipitation. This process is illustrated in Figure 20. Condensation Precipitation Transpiration Evaporation RunoffFigure 20A water molecule that falls asrain can follow several pathsthrough the water cycle.How many of these paths canyou identify in this diagram?232
  22. 22. Other Cycles in Plants remove carbon After the carbonNature What do dioxide from the air is returned to theyou have in common and use it to make atmosphere, thewith all organisms? All carbohydrates. cycle begins again.organisms containcarbon. Earth’s atmo-sphere contains about0.03 percent carbon inthe form of carbondioxide gas. Themovement of carbonthrough Earth’s bio-sphere is called thecarbon cycle, as shownin Figure 21. The carbohydrates are Nitrogen is an ele- eaten and used by The carbon from other organisms. the carbohydratesment used by organ- is returned to theisms to make proteins atmosphereand nucleic acids. The nitrogen through respiration,cycle begins with the transfer of combustion, andnitrogen from the atmosphere to decay.producers then to consumers. Thenitrogen then moves back to the atmosphere or directly into Figure 21producers again. Carbon can follow several differ- Phosphorus, sulfur, and other elements needed by living ent paths through the carbon cycle. Some carbon is stored inorganisms also are used and returned to the environment. Just Earth’s biomass.as you recycle aluminum, glass, and paper products, the materi-als that organisms need to live are recycled continuously in thebiosphere. Section Assessment 1. Compare a food chain and a food web. 2. What are the differences among producers, 6. Classifying Look at the food chain in Figure consumers, and decomposers? 18. Classify each organism as a producer or a 3. What is an energy pyramid? consumer. For more help, refer to the Science 4. How does carbon flow through eco- Skill Handbook. systems? 7. Communicating In your Science Journal, 5. Think Critically Use your knowledge of write a short essay about how the water cycle, food chains and the energy pyramid to carbon cycle, and nitrogen cycle are important explain why fewer lions than gazelles live to living organisms. For more help, refer to the on the African plains. Science Skill Handbook. SECTION 3 Matter and Energy 233
  23. 23. Identifying a Limiting Factor O rganisms depend upon many biotic and abiotic factors in their environment to survive. When these factors are limited or are not available, it can affect an organism’s survival. By experimenting with some of these limiting factors, you will see how organisms depend on all parts of their environment. Recognize the Problem How do abiotic factors such as light, water, and temperature affect the germination of seeds? Form a Hypothesis Based on what you have learned about limiting factors, make a hypothesis about how one specific abiotic factor might affect the germination of a bean seed. Be sure to consider factors that you can change easily. Safety Precautions Goals s Observe the effects of an abiotic factor on the germination and Wash hands after handling soil growth of bean seedlings. and seeds. s Design an experiment that demon- strates whether or not a specific abiotic factor limits the germination of bean seeds. Possible Materials bean seeds small planting containers soil water label trowel *spoon aluminum foil sunny window *other light source refrigerator or oven *Alternate materials234
  24. 24. Test Your HypothesisPlan1. As a group, agree upon and write out a hypothesis statement.2. Decide on a way to test your group’s hypothesis. Keep available materials in mind as you plan your procedure. List your materials.3. Design a data table in your Science Journal for recording data.4. Remember to test only one variable Do at a time and use suitable controls. 1. Make sure your teacher approves5. Read over your entire experiment your plan before you start. to make sure that all steps are in 2. Carry out the experiment according logical order. to the approved plan.6. Identify any constants, variables, 3. While the experiment is going on, and controls in your experiment. record any observations that you7. Be sure the factor that you will test make and complete the data table is measurable. in your Science Journal. Analyze Your Data1. Compare the results of this experi- 3. Graph your results in a bar graph ment with those of other groups in that compares the number of bean your class. seeds that germinated in the exper-2. Infer how the abiotic factor you imental container with the number tested affected the germination of of seeds that germinated in the bean seeds. control container. Draw Conclusions1. Identify which factor had the greatest effect on the germination of the seeds.2. Determine whether or not you Write a set of instructions that could be included could change more than one factor on a packet of this type of seeds. Describe the in this experiment and still have best conditions for seed germination. germination of seeds. ACTIVITY 235
  25. 25. marsup alnucleus organelle marsupial mantle element ibosome primate sea otter hypertension jet ici Science & Language Artsand orwa The Solace of Open Spacesno a novel by Gretel Ehrlichme d Respond to the Reading A 1 nimals give us their constant, unjaded faces and we burden them with our bodies and civilized og 1. From reading this passage, can you ordeals. We’re both humbled by and imperious with them. We’re comrades who save each other’s lives. 2ntu guess the occupation of the narrator? The horse we pulled from a boghole this morning bucked m someone off later in the day; one stock dog refuses to work 2. Describe the relation- ship between people sheep, while another brings back a calf we had overlooked. cai and animals in this passage. . . . What’s stubborn, secretive, dumb, and keen in us bumps up against those same qualities in them. . . . 3 ha 3. What words does the author use to Living with animals makes us redefine our ideas aboutppu indicate that horses are intelligent? intelligence. Horses are as mischievous as they are depend- able. Stupid enough to let us use them, they are cunningatim tim enough to catch us off guard. . . . We pay for their loyalty; They can be willful, hard to ou catch, dangerous to shoe and buck on frosty mornings. Indig turn, they’ll work themselves into a lather cutting cows, not for the praise they’ll co get but for the simpleaga ga glory of outdodging a calf or catching up with an ni errant steer. . . . he 1 Jaded means “to be weary with fatigue,” so unjaded means “not to be weary with fatigue.” enc 2 domineering or overbearing 3 intellectually smart or sharpbre ozopopoi 236 CHAPTER 8 Interactions of Living Thingsoem
  26. 26. m grat on compound d chotomous greenhoexoskeleton permafrost magma isotopes plat Informative Writing cell gym Understanding Literature Informative Writing The passage that you have just ma Linking Science read is from a work of nonfiction and is based on and facts. The passage is informative because it describes ion the real relationship between people and animals on a ranch in Wyoming. The author speaks from her own the Informative Writing Write a point of view, not from the point of view of a disinter- ested party. She uses her own experience to explain to kid short passage about an experi- ence you have had with a pet. In readers that animals and people depend on each other for survival. For example, she writes, “Living with ani- pro your writing, reflect on how you and the pet are alike and depend- mals makes us redefine our ideas about intelligence.” ign ent upon each other. Put yourself firmly in the story without over- The language puts her firmly in the story—she is not par only telling the story, but living it, too. How might this using the word I. story have been different if it had been told from the point of view of a visiting journalist? zon Science Connection Animals and ranchers are clearly mo dependent on each other. Ranchers provide nutrition and shelter for animals on the ranch and, in turn, ani- orp mals provide food and perform work for the ranchers. You might consider the relationship between horses eta etal and ranchers to be a symbiotic one. Symbiosis (sihm bee OH sus) is any close interaction among two or allo more different species. om Career Connection Large-Animal Veterinarian oge pro Dave Garza works to keep horses healthy. Dave spends about 20 acc percent of his workday in his clinic. He goes there first thing in the morning to perform surgeries and take care of horses that have been tab brought to him. The rest of the day, he drives to local farms to examine patients. Dave vaccinates horses against rabies, the flu, and nol the encephalitis virus. He gives them tetanus shots and medication to eat prevent worms. He also cares for their teeth, replaces their shoes, eath and helps them deliver their foals in the spring. tem To learn more about careers in veterinary medi- sol sola cine, visit the Glencoe Science Web site at science.glencoe.com. 237 hav SCIENCE AND LANGUAGE ARTS dim
  27. 27. Chapter 8 Study GuideSection 1 The Environment 4. The place where an1. Ecology is the study of interactions among organism lives is its organisms and their environment. habitat, and its role in the environment is its2. The nonliving features of the environment niche. How could two are abiotic factors, and the organisms in the similar species of birds environment are biotic factors. live in the same area and3. Populations and communities make up an nest in the same tree with- ecosystem. What populations and communi- out occupying the same niche? ties might be present in this ecosystem? Section 3 Matter and Energy 1. Food chains and food webs are models that describe the feeding relationships among organisms in a community. 2. At each level of a food chain, organisms lose energy as heat. Energy on Earth is renewed constantly by sunlight. 3. An ecological pyramid models the number of organisms at each level of a food chain4. The region of Earth and its atmosphere in in an ecosystem. which all organisms live is the biosphere. Why is each level of this energy pyramidSection 2 Interactions Among Living smaller thanOrganisms the one1. Characteristics that can describe popula- below it? tions include size, spacing, and density. 4. Matter on Earth is never lost or gained. It is2. Any biotic or abiotic factor that limits the used over and over again, or recycled. number of individuals in a population is a limiting factor. After You Read FOLDABLES3. A close relationship between two or more Reading &Study & Study Using your Foldable, species is a symbiotic relationship. A symbi- Skills explain the cause and otic relationship that benefits both species effect relationship is called mutualism. A relationship in which between specific abiotic and biotic organisms one species benefits and the other is un- around you. affected is called commensalism.238 CHAPTER STUDY GUIDE
  28. 28. Chapter 8 Study Guide Complete the following concept mapon the biosphere. Biosphere is made up of Biotic parts include include Air Soil Organisms Temperature together with make up make upVocabulary Words Using Vocabularya. abiotic factor i. habitat Replace the underlined words with the correctb. biosphere j. limiting factor vocabulary words.c. biotic factor k. niche 1. A(n) abiotic factor is any living thing in thed. community l. population environment.e. ecology m. population densityf. ecosystem n. symbiosis 2. A series of overlapping food chains makesg. food chain o. water cycle up a(n) nitrogen cycle.h. food web 3. The size of a population that occupies an area of definite size is its carrying capacity. 4. Where an organism lives in an ecosystem is Study Tip its niche. 5. The part of Earth that supports life is the Use tables to organize ideas. For example, put limiting factor. the levels of biological organization in a table. Tables help you review concepts quickly. 6. Any close relationship between two or more species is habitat. CHAPTER STUDY GUIDE 239
  29. 29. Chapter 8 Assessment 9. Which of the following is a biotic factor? A) animals C) sunlight Choose the word or phrase that best answers B) air D) soilthe question. 10. What are all of the individuals of one 1. Which of the following is NOT cycled in the species that live in the same area at the same biosphere? time called? A) nitrogen C) water A) community C) biosphere B) soil D) carbon B) population D) organism 2. What are coral reefs, forests, and ponds examples of? A) niches C) populations B) habitats D) ecosystems 11. What are two different populations that 3. What is made up of all populations in an might be present in a desert biome? Two area? different ecosystems? Explain. A) niche C) community 12. Why are viruses considered parasites? B) habitat D) ecosystem 13. What does carrying capacity have to do 4. What is the term for the total number of with whether or not a population reaches individuals in a population occupying a its biotic potential? certain area? 14. Why are decomposers vital to the cycling of A) clumping C) spacing matter in an ecosystem? B) size D) density 15. Write a paragraph that describes your own 5. Which of the following is an example of a habitat and niche. producer? A) wolf C) tree B) frog D) rabbit 6. Which level of the food chain has the most 16. Classifying Classify the following as the energy? result of either evaporation or condensa- A) consumer C) decomposers tion. B) herbivores D) producers a. A puddle disappears after a rainstorm. 7. What is a relationship called in which one b. Rain falls. organism is helped and the other is c. A lake becomes shallower. harmed? d. Clouds form. A) mutualism C) commensalism 17. Concept Mapping Use the following infor- B) parasitism D) consumer mation to draw a food web of organisms 8. Which of the following is a model that living in a goldenrod field. Aphids eat gold- shows the amount of energy available as it enrod sap, bees eat goldenrod nectar, beetles flows through an ecosystem? eat goldenrod pollen and goldenrod leaves, A) niche C) carrying capacity stinkbugs eat beetles, spiders eat aphids, and B) energy pyramid D) food chain assassin bugs eat bees.240 CHAPTER ASSESSMENT
  30. 30. Chapter 8 Assessment18. Making and Using Arizona Deer Graphs Use the fol- Population Test Practice lowing data to graph Year Deer Per the population den- Biologists want to estimate the total 400 sity of a deer popula- Hectares number of fish in a lake. They plan to tow tion over the years. a sampling device from one side of the 1905 5.7 Plot the number of lake to the other a single time. They dis- 1915 35.7 cuss the sampling strategies shown below. deer on the y-axis 1920 142.9 and years on the x-axis. Predict what 1925 85.7 1 3 might have hap- 1935 25.7 pened to cause the changes in the size of the population.19. Recording Observations A home aquarium contains water, an air pump, a light, algae, a goldfish, and algae-eating snails. What are 2 4 the abiotic factors in this environment?20. Comparing and Contrasting Compare and contrast the role of producers, consumers, and decomposers in an ecosystem. Use the diagrams to answer the following questions.21. Poster Use your own observations or the 1. Which strategy is likely to provide the results of library research to develop a food most accurate estimate of the number web for a nearby park, pond, or other of fish in the lake? ecosystem. Make a poster display illustrat- A) diagram 1 C) diagram 3 ing the food web. B) diagram 2 D) diagram 422. Oral Presentation Research the steps in the 2. How can the biologists improve their phosphorous cycle. Find out what role investigation? phosphorus plays in the growth of algae in F) tow the sampling device very ponds and lakes. Present your findings to quickly the class. G) tow the sampling device very slowly H) tow the sampling device more then once TECHNOLOGY J) tow the sampling device around the Go to the Glencoe Science Web site at edge of the lake science.glencoe.com or use the Glencoe Science CD-ROM for additional chapter assessment. CHAPTER ASSESSMENT 241

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