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Department
African Studies
Course
AFSA02
Professor
A
Semester
Summer

Description
Chapter 56 – Ecosystems and Global Ecology (only 56.2, 56.4 and 56.5!!!) How Does Energy Flow Through The Global Ecosystem?  all energy utilized by organisms come from the sun  fossil fuels is based on reserves of captured solar energy locked up in the remains of organisms that lived a million years ago  energy enters ecosystems by way of plants and other photosynthetic organisms  Gross primary product – rate at which energy is incorporated into the bodies of photosynthetic organisms  Gross primary production – accumulated energy  Primary producers use some of the accumulated energy for their own metabolism and the rest is stored in their bodies or used for growth and reproduction  Net primary production – energy available to organisms that eat primary producers  gross primary production – the energy expended by the primary producers during their metabolism  Only the energy of an organism’s net production is available to other organisms that consume it  geographic distribution of the energy assimilated by primary producers reflects the distribution of land masses, temperature and moisture on Earth  close to equator at sea level, temperatures are high throughout the year and water supply is adequate for growth  in low and mid-latitude deserts where plant growth is limited by lack of moisture, primary production is also low  in high latitudes where moisture is available, primary production is still low because it is cold for much of the year  production in aquatic systems is limited by light, nutrients and temperature  human activities decreases net global primary productivity (ie. Converting forest to grasslands and urban developments) and some increase it (ie. Intensify agriculture)  humans appropriate about 20% of the average annual net primary production ■ urban areas consume 300x the NPP they generate What Services Do Ecosystems Provide?  Many benefits are irreplaceable or the technology necessary to replace them are very expensive ■ potable fresh water can be provided by desalinating seawater but only at a great cost  rapidly expanding human population has modified Earth's ecosystems to increase their ability to provide some of the goods and services it needs ■ these modifications have contributed to human well-being and economic development  short-term increases in some ecosystem goods have come at the cost of the long-term degradation of others ■ efforts to increase wood and fiber have decreased the ability for some ecosystems to provide clean water, regulate flooding and support biodiversity ■ the spread of agriculture into into marginal lands has increased soil
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