Download Objective 8: TSWBAT describe the cycling of

Objective 8: TSWBAT
describe the cycling of
chemical elements in
ecosystems.
The cycling of chemical elements in
ecosystems
• Life on earth depends on the recycling of essential
chemical elements
• Atoms present in the complex molecules of an
organism at its time of death are returned as simpler
compounds to the atmosphere, water, or soil by the
actions of decomposers
• This decomposition replenished the pools of
inorganic nutrients that plants and other autotrophs
use to build new organic matter
• These circuits are also called biogeochemical cycles.
• There are two general categories of biogeochemical
cycles
• Carbon, oxygen, sulfur and nitrogen occur in the
atmosphere and cycles of these elements is essentially
global
• The carbon and oxygen atoms a plant acquires from
the air as CO2 may have been released into the
atmosphere by the respiration of a plant or animal in
some distant place.
• Phosphorus, potassium, calcium and the traces element
generally cycle on a more localized scale, at least over
the short term
• Soil is the main abiotic reservoir of these elements
and recycled in the same general vicinity usually.
• Most nutrients accumulate in four reservoirs,
defined by 2 characteristics.
• Does it contain organic or inorganic material?
• Are the material directly available for use by organisms?
• One compartment of organic material is composed
of the living organism themselves and detritus
• These nutrients are available to other organisms when
consumers feed and detritivores consume nonliving
organic matter
• The other organic compartment includes
“fossilized” deposits of once-living organisms from
which nutrients cannot be assimilated directly
• In one compartment of inorganic material nutrients
are available for use by organisms
• This would include matter that is dissolved in water or
present in soil or air
• Organisms assimilate these materials and return them
through the fairly rapid processes of cellular respiration,
excretion and decomposition
• In the other compartment of inorganic material,
nutrients are not available
• The nutrients are tied up in rocks
• Although organisms cannot directly use these, they
slowly become available through weathering and
erosion.
• Similarly, the unavailable organic nutrients move
into the compartment of available inorganic
nutrients through erosion or when fossil fuels are
burned
The Water Cycle
The Nitrogen Cycle
The Carbon Cycle
The Phosphorus Cycle
Biogeochemical Cycles