BIOL 3010 Lecture Notes - Human Overpopulation, Ecosystem Services, Soil Retrogression And Degradation

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1 Aug 2012
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
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
Net primary production – energy available to organisms that eat primary
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
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