KEY CONCEPT Ecology is the study of the relationships among organisms and their environment.

1. 13.1 Ecologists Study Relationships KEY CONCEPT Ecology is the study of the relationships among organisms and their environment.

2. 13.1 Ecologists Study Relationships Ecologists study environments at different levels of organization. • Ecology is the study of the interactions among living things, and between living things and their surroundings.

3. 13.1 Ecologists Study Relationships Organism Organism • An organism is an individual living thing, such as an alligator.

4. 13.1 Ecologists Study Relationships Population Population Organism Organism • A population is a group of the same species that lives in one area.

5. 13.1 Ecologists Study Relationships Community Community Population Population Organism Organism • A community is a group of different species that live together in one area.

6. 13.1 Ecologists Study Relationships Ecosystem Ecosystem Community Community Population Population Organism Organism • An ecosystem includes all of the organisms as well as the climate, soil, water, rocks and other nonliving things in a given area.

7. 13.1 Ecologists Study Relationships Biome Ecosystem Ecosystem Community Community Population Population Organism Organism • A biome is a major regional or global community of organisms characterized by the climate conditions and plant communities that thrive there.

8. 13.1 Ecologists Study Relationships Ecological research methods include observation, experimentation, and modeling. • Observation is the act of carefully watching something over time. • Observations of populations can be done by visual surveys. • Direct surveys for easy to spot species employ binoculars or scopes. • Indirect surveys are used for species that are difficult to track and include looking for other signs of their presence.

9. 13.1 Ecologists Study Relationships • Lab experiments give researchers more control. • Lab experiments are not reflective of the complex interactions in nature. • Experiments are performed in the lab or in the field. • Field experiments give a more accurate picture of natural interactions. • Field experiments may not help determine actual cause and effect.

10. 13.1 Ecologists Study Relationships Ecologists use data transmitted by GPS receivers worn by elephants to develop computer models of the animal’s movements. • Computer and mathematical models can be used to describe and model nature. • Modeling allows scientists to learn about organisms or ecosystems in ways that would not be possible in a natural or lab setting.

11. 13.2 Biotic & Abiotic Factors KEY CONCEPT Every ecosystem includes both living and nonliving factors.

12. 13.2 Biotic & Abiotic Factors plants An ecosystem includes both biotic and abiotic factors. • Biotic factors are living things. • plants • animals • fungi • bacteria

13. 13.2 Biotic & Abiotic Factors sunlight moisture • moisture • temperature • wind • sunlight • soil • Abiotic factors are nonliving things.

14. 13.2 Biotic & Abiotic Factors Changing one factor in an ecosystem can affect many other factors. • Biodiversity is the assortment, or variety, of living things in an ecosystem. • Rain forests have more biodiversity than other locations in the world, but are threatened by human activities.

15. 13.2 Biotic & Abiotic Factors keystone • A keystone species is a species that has an unusually large effect on its ecosystem.

16. 13.2 Biotic & Abiotic Factors creation of wetland ecosystem increased waterfowl Population keystone species increased fish population nesting sites for birds • Keystone species form and maintain a complex web of life.

17. 13.3 Energy in Ecosystems KEY CONCEPT Life in an ecosystem requires a source of energy.

18. 13.3 Energy in Ecosystems Producers provide energy for other organisms in an ecosystem. • Producers get their energy from non-living resources. • Producers are also called autotrophs because they make their own food.

19. 13.3 Energy in Ecosystems Producers provide energy for other organisms in an ecosystem. • Consumers are organisms that get their energy by eating other living or once-living resources. • Consumers are also called heterotrophs because they feed off of different things.

20. 13.3 Energy in Ecosystems carbon dioxide + water + hydrogen sulfide + oxygen sugar + sulfuric acid Almost all producers obtain energy from sunlight. • Photosynthesis in most producers uses sunlight as an energy source. • Chemosynthesis in prokaryote producers uses chemicals as an energy source.

21. 13.4 Food chains & food webs KEY CONCEPT Food chains and food webs model the flow of energy in an ecosystem.

22. 13.4 Food chains & food webs GRAMA GRASS DESERT COTTONTAIL HARRIS’S HAWK A food chain is a model that shows a sequence of feeding relationships. • A food chain links species by their feeding relationships. • A food chain follows the connection between one producer and a single chain of consumers within an ecosystem.

23. 13.4 Food chains & food webs carnivore decomposer • Herbivores eat only plants. • Carnivores eat only animals. • Omnivores eat both plants and animals. • Detritivores eat dead organic matter. • Decomposers are detritivores that break down organic matter into simpler compounds. • Consumers are not all alike.

24. 13.4 Food chains & food webs • Specialists are consumers that primarily eat one specific organism or a very small number of organisms. • Generalists are consumers that have a varying diet.

25. 13.4 Food chains & food webs • Primary consumers are herbivores that eat producers. • Secondary consumers are carnivores that eat herbivores. • Tertiary consumers are carnivores that eat secondary consumers. • Omnivores, such as humans that eat both plants and animals, may be listed at different trophic levels in different food chains. • Trophic levels are the nourishment levels in a food chain.

26. 13.4 Food chains & food webs A food web shows a complex network of feeding relationships. • An organism may have multiple feeding relationships in an ecosystem. • A food web emphasizes complicated feeding relationships and energy flow in an ecosystem.

27. 13.5 Cycling of Matter KEY CONCEPT Matter cycles in and out of an ecosystem.

28. 13.5 Cycling of Matter precipitation condensation transpiration evaporation surface runoff lake water storage in ocean groundwater seepage Water cycles through the environment. • The hydrologic, or water, cycle is the circular pathway of water on Earth. • Organisms all have bodies made mostly of water.

29. 13.5 Cycling of Matter Elements essential for life also cycle through ecosystems. • A biogeochemical cycle is the movement of a particular chemical through the biological and geological parts of an ecosystem. • The main processes involved in the oxygen cycle are photosynthesis and respiration.

30. 13.5 Cycling of Matter oxygen photosynthesis respiration carbon dioxide • Oxygen cycles indirectly through an ecosystem by the cycling of other nutrients.

31. 13.5 Cycling of Matter carbon dioxide in air respiration combustion photosynthesis respiration photosynthesis decomposition of organisms carbon dioxide dissolved in water fossil fuels • The carbon cycle moves carbon from the atmosphere, through the food web, and returns to the atmosphere. • Carbon is emitted by the burning of fossil fuels. • Some carbon is stored for long periods of time in areas called carbon sinks. • Carbon is the building block of life.

32. 13.5 Cycling of Matter nitrogen in atmosphere animals plant nitrates nitrogen-fixing bacteria in roots decomposers nitrifying bacteria ammonification nitrites nitrogen-fixing bacteria in soil ammonium nitrifying bacteria denitrifying bacteria • Some bacteria convert gaseous nitrogen into ammonia through a process called nitrogen fixation. • Some nitrogen-fixing bacteria live innodules on theroots of plants;others livefreely inthe soil. • The nitrogen cycle mostly takes place underground.

33. 13.5 Cycling of Matter nitrogen in atmosphere animals plant nitrates nitrogen-fixing bacteria in roots decomposers nitrifying bacteria ammonification nitrites nitrogen-fixing bacteria in soil ammonium nitrifying bacteria denitrifying bacteria • Nitrifying bacteria change the ammonium into nitrate. • Nitrogen moves through the foodweb and returnsto the soil duringdecomposition. • Ammonia released into the soil is transformed into ammonium.

34. 13.5 Cycling of Matter rain geologic uplifting weathering of phosphate from rocks runoff plants animals phosphate in soil phosphate in solution leaching sedimentation forms new rocks decomposers • Phosphate is released by the weathering of rocks. • Phosphorus moves through the food web and returns to the soil duringdecomposition. • The phosphorus cycle takes place at and below ground level. • Phosphorus leaches into groundwater from the soil and is locked in sediments. • Both mining and agriculture add phosphorus into the environment.

35. 13.6 Pyramid Models KEY CONCEPT Pyramids model the distribution of energy and matter in an ecosystem.

36. 13.6 Pyramid Models energy lost energy transferred An energy pyramid shows the distribution of energy among trophic levels. • Energy pyramids compare energy used by producers and other organisms on trophic levels. • Between each tier of an energy pyramid, up to 90 percent of the energy is lost into the atmosphere as heat. • Only 10 percent of the energy at each tier is transferred from one trophic level to the next.

37. 13.6 Pyramid Models tertiary consumers 75 g/m2 150g/m2 secondary consumers primary consumers 675g/m2 2000g/m2 2000g/m2 producers producers Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms. • Biomass is a measure of the total dry mass of organisms in a given area.

38. 13.6 Pyramid Models 5 tertiary consumers secondary consumers 5000 primary consumers 500,000 producers 5,000,000 producers 5,000,000 • A pyramid of numbers shows the numbers of individual organisms at each trophic level in an ecosystem. • A vast number of producers are required to support even a few top level consumers.