1. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Organisms and Their Environment Ecology is the study of how organisms interact with their environments. The environment includes abiotic (nonliving) and biotic (living) components. We study ecology at many levels, including the individual, population, community, and ecosystem.

2. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Prairie dogs living in Nebraska represent: A.A species B.A population C.A community Organisms and Their Environment CHECK YOUR NEIGHBOR

3. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Prairie dogs living in Nebraska represent: A.A species B.A population C.A community Organisms and Their Environment CHECK YOUR ANSWER

4. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Species Interactions Food chains and food webs describe which species eat which other species. These feeding levels—called trophic levels—include producers and consumers.

5. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Species Interactions Other types of species interactions include: Competition—species compete when their niches overlap. Symbiosis—species may live in close association with one another. A symbiotic relationship may involve parasitism, commensalism, or mutualism.

6. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Kinds of Ecosystems There are terrestrial and aquatic ecosystems. Terrestrial ecosystems are called biomes.biomes

7. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Energy Flow in Ecosystems All organisms need energy in order to grow, reproduce, and perform the activities necessary for survival. The amount of organic matter in an ecosystem is its biomass. The rate at which an ecosystem’s producers build biomass is the ecosystem’s primary productivity.

8. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Energy Flow in Ecosystems On average, only about 10 percent of the energy at one trophic level becomes available to the next level. The other 90 percent is: Uneaten organisms Heat lost to the environment Feces Maintenance

9. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Integrated Science: Energy Leaks Where Trophic Levels Meet Moving energy from one trophic level to another involves a long series of chemical reactions. Because every chemical reaction involves some energy loss to the environment, we see why so much energy leaks from one trophic level to the next.

10. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Kinds of Ecosystems There are eight biomes on Earth: Tropical forests Temperate forests Coniferous forests Tundra Savannas Temperate grasslands Chaparral Deserts

11. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Kinds of Ecosystems Aquatic ecosystems include freshwater and saltwater environments as well as estuaries where freshwater and saltwater meet.

12. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Kinds of Ecosystems All lakes and ponds can be divided into three zones: The littoral zone—close to the water surface and to shore, relatively warm because of its exposure to sunlight. The limnetic zone—close to the water surface but far from shore, occupied largely by plankton, organisms that float in the water rather than swim actively. The profundal zone—deep water habitats in ponds and lakes. Most organisms in the profundal zone consume organic debris that drifts down from above.

13. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Kinds of Ecosystems Species that live in the flowing waters of rivers and streams usually have adaptations that allow them to keep from being washed away: hooks, suckers, strong swimming ability. Algae often occupy the base of the food chain in river and stream habitats.

14. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Kinds of Ecosystems Estuaries are habitats where freshwater rivers join oceans. Estuarine plants, such as certain seaweeds, marsh grasses, and mangroves, have adaptations that allow them to deal with changing salinity conditions.

15. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Integrated Science: Materials Cycling Many substances on Earth travel through a continuous cycle from living organisms to the abiotic environment and back—these are biogeochemical cycles. Three of these cycles involve water, carbon, and nitrogen.

16. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Integrated Science: Materials Cycling The water cycle: Water evaporates from the oceans into the atmosphere. Water is moved around the atmosphere by winds. Water precipitates as rain or snow over ocean or land. Water moves into the biotic world when it is absorbed or swallowed by organisms. Some of this water then passes up the food chain. The rest is returned to the abiotic environment in a variety of ways, including through animal respiration, perspiration, excretion, and elimination, and evaporation from plant tissue.

17. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Integrated Science: Materials Cycling The carbon cycle: Most of the inorganic carbon on earth exists as carbon dioxide and is found either in the atmosphere or dissolved in ocean waters. Plants and other producers convert carbon dioxide to glucose during photosynthesis. Carbon is returned to the environment by living organisms as carbon dioxide, a product of cellular respiration. Because atmospheric carbon dioxide traps heat on the planet, this has resulted in global warming.

18. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Integrated Science: Materials Cycling The nitrogen cycle: Nitrogen is found primarily as nitrogen gas, the dominant component of the Earth’s atmosphere. In order for living organisms to make use of nitrogen, it has to be converted into usable form. Living organisms rely on bacteria to accomplish this transformation. Nitrogen is converted to ammonium by nitrogen-fixing bacteria in soil, and then to nitrates by nitrifying bacteria. Nitrogen returns to the abiotic environment when it is converted back to nitrogen gas by denitrifying bacteria.