EOC_ch07

Essential Environment: The Science behind the Stories (3rd Edition)

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Chapter 7 Testing Your Comprehension 1 Negative feedback loops are most common in nature, whereas positive loops sometimes result from human actions. When they do, they tend to move systems away from their homeostatic condition. 2 Excess nutrients in runoff from the land fertilize phytoplankton in the coastal marine ecosystem. This results in rapid growth of the phytoplankton population. Dead phytoplankton and waste products then accumulate on the bottom, where bacterial decomposition consumes most of the available oxygen, causing hypoxia. 3 An ecosystem includes both the biotic community and its abiotic environment. A community includes only the populations of living organisms in a given area. 4 Typically, energy moves through an ecosystem from its source (the sun) to plants or other photosynthetic primary producers. They are then consumed by a variety of organisms, which in turn are consumed by others. At each step, some energy is passed along to the consumer and some is lost as waste heat. Matter is also transferred up the food chain as organisms eat organisms on lower trophic levels, but matter from organisms’ waste and from dead organisms is consumed and broken down by detritivores and decomposers, returning matter to the soil so that it can be recycled through the food web. 5 Cars release significant amounts of CO 2 into the atmosphere from the combustion of oil. Photosynthesis is the process by which plants remove CO 2 from the atmosphere and store the carbon as sugar. The oceans are home to a large volume of phytoplankton which can remove CO 2 from the air by photosynthesis; CO 2 also dissolves in seawater, is incorporated into carbonate minerals, and collects as
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EOC_ch07 - Chapter 7 Testing Your Comprehension 1 Negative...

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