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Summary
• Biogeochemical cycles
exchange of important nutri-
ents between the abiotic and
biotic parts of an ecosystem.
• The carbon and oxygen cycles
are closely intertwined.
• Nitrogen gas is limited in its
ability to enter biotic portions
of the environment.
• Phosphorus and carbon have
short-term and long-term
cycles.
Demonstrate Understanding
1.
Name
four important biogeochemical processes that
cycle matter.
2.
Analyze
the role of photosynthesis and cellular respi-
ration in the carbon cycle.
3.
Identify
the living and nonliving parts of the nitrogen
cycle.
4.
Compare and contrast
the role of plants in the carbon
and nitrogen cycles.
5.
Describe
how phosphorus moves through the biotic
and abiotic parts of an ecosystem.
Explain Your Thinking
6.
Describe
the flow of energy and matter through a food
web that begins with algae at the lowest level.
Check Your Progress
Figure 23
Increased amounts of nitrogen and phosphorus
that enter the environment from mining, sewage, or
fertilizers can cause algae overgrowth like that seen in this
pond.
Phosphorus moves from the short-term cycle to the long-term cycle through
precipitation and sedimentation to form rocks. Phosphorus that settles into sediment
in aqueous environments is transferred to the land by geological changes and uplift.
Phosphorus that undergoes sedimentation does not become available to land organisms
again until weathering or erosion of rocks that contain phosphorus slowly adds
phosphorus to the soil.
Human activities, such as phosphate mining, sewage treatment, and fertilizer
production, increase the amount of phosphate cycling through the environment. Too
much phosphate can result in algae overgrowth, called algae blooms, like that shown in
Figure 23
, and upset the balance of an ecosystem. Algae blooms can occur in freshwater
or marine ecosystems.
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Module 2 • Principles of Ecology