Review Questions Chp Ecosystems) Key

Review Questions – Ecosystems (KEY)

1. List the principal trophic levels in an ecosystem of your choice; state the source of energy for each trophic level and give one or two examples of organisms associated with each trophic level.

The Pond Trophic level 1: Primary producers are autotrophs that can capture sunlight energy and incorporate it into organic compounds. Algae; Spirogyra, Pinnularia, Diatoma, etc Trophic level 2: Consumers are heterotrophs that feed on tissues of other organisms. Grazers: rotifers, Copepods, etc Herbivores eat plants. Some parasites, decomposers and detritivores that feed off of level 1 Trophic level 3: Carnivores; Rotaria, Spirostomum. Etc consume level 2 organisms. Parasites reside in or on living hosts and extract energy from them. Omnivores eat a variety of organisms. Decomposers are also heterotrophs and include fungi and bacteria that extract energy from the remains or products of organisms. Detritivores include small invertebrates that feed on partly decomposed particles of organic matter (detritus).

2. A(n) ___ecosystem_______ is an array of organisms and their physical environment, all interacting through a flow of energy and a cycling of materials. 3. Explain why nutrients can be completely recycled but energy cannot.

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4. Members of an ecosystem fit somewhere in a hierarchy of energy transfers (feeding relationships) called ___trophic _______ levels. [p.739] 5. Distinguish between food chains and food webs Web are interlocking food

chains. Chains are linear relationships. 6. In most cases, __energy________ that producers initially captured passes through no more than four or five trophic levels. [p.740] 7. Compare grazing food webs with detrital food webs. Present an example of each.

Grazing food webs use the energy from the first level (green plants) directly (a pasture is an example). Detrital systems rely on dead material that is not necessarily generated in that community (beach systems on Georgia barrier islands rely on the importation of dead marsh grass via the tide for energy). 8. 9. Through __systems________ modeling, crucial bits of information about different ecosystem components are identified and used to build computer models for predicting outcomes of ecosystem disturbances. [p.742] 10. Describe how DDT damages ecosystems; discuss biological magnification.

DDT is bio-accumulated and magnified through food webs so that top predators have dangerous levels of the substance in their tissues. This is a result of two things: (1) DDT does not readily decompose and (2) each step of the food chain used about 10 times the energy or biomass of the level just below it. Birds of prey have been damaged because DDT blocks proper calcium deposition in their eggs rendering them fatality weak. 11. Distinguish between primary productivity, gross primary productivity, and the net amount. Primary productivity refers to photosynthesis

(community level). GPP is the total quantity of community photosynthesis and NPP refers to what is available to the heterotrophs (some photosynthesis is required for plant consumption and accordingly, it is not available to the rest of the community. 2

12. Understand how materials and energy enter, pass through, and exit an ecosystem.

Energy (usually sunlight) enters the system through the process of photosynthesis. Some of this energy is consumed by herbivores. Most is lost as heat. This continues through 3 or 4 more levels to the top predator. Tat each level 90% of the energy available is lost as heat.

13. Ecological pyramids that are based on __biomass________ are determined by the weight of all the members of each trophic level; __energy (heat)________ pyramids reflect the energy losses at each transfer to a different trophic level. [p.743] 14. Explain what studies at Silver Springs, Florida, watershed have taught us about energy flow. 15.

This was one of the very first quantitative ecological studies of energy flow in an ecosystem. It reveled that much energy is lost at each level resulting in a “cap” of trophic levels of about 4 or 5.

16. In __biogeochemical________ cycles, the nutrient is transferred from the environment to organisms, then back to the environment—which serves as a large reservoir for it. [p.745] 17. Be able to discuss water movements through the hydrologic cycle. Refer to

PPP. lecture 18. Describe the geochemical and ecosystem phase of the phosphorus cycle Refer

to the PPP lecture. 19. 20. __Eutrophication________ is the name for nutrient enrichment of an ecosystem that is naturally low in nutrients. [p.747] 21. The carbon cycle traces carbon movement from reservoirs in the __earth________ and oceans, through organisms, then back to reservoirs. [pp.748-749] 22. Certain gases cause heat to build up in the lower atmosphere, a warming action known as the __greenhouse effect________ effect. [p.750]

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23. As to causes and effects, list the outcomes that might occur if the lower atmosphere’s temperature spikes higher by 2.5 to 10.4 degrees in this century.

Refer to the text. 24. A major element found in all proteins and nucleic acids moves in an atmospheric cycle called the __nitrogen________ cycle. [pp.752-753] 25. Define the chemical events that occur during nitrogen fixation, decomposition and ammonification, and nitrification. Refer to the PPP. 26. Be able to discuss various aspects of the human impact on the nitrogen cycle. Refer to the PPP and/or the text.

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