B8 - Nitrogen Cycles

nitrogen fixation

conversion of N2 gas into NO3- (nitrate) ions. done by N-fixers(bacteria, cyanobacteria)

nitrogen reduction

reduction of No3- (nitrate) into NH3 (ammonium). done by a second set of micro-organisms.

nitrogen assimilation

incorporation of NH3 into organic molecules by plant. usually occurs in roots and soil.

how does dead bacteria and cyanobacteria help supply N to plants

bacteria and cyanobacteria help supply nitrogen to plants during nitrogen fixation

What are the 3 sources of nitrogen in plants.

1) Originally gets into the bio-system through N-fixers and N-reducers.

2) After plant decomposes, it gets into soil solution, and is taken up by the nearest root and cycled back into living organisms.

3) Certain environments and special association.

What is the selection pressure for the evolution of plant carnivory?

No soil in bogs and swamps, so plants there capture reduced N by catching animals.

What is the selection pressure for the evolution of “ant plants”

Some angiosperms and ferns supplement their N from fecal matter and dead bodies of ants.

Describe ways in which foresters manage nutrients

Harvesting intensity, N-fixing plants, Alter pH, air pollution, fertilization

biogeochemical cycle

movement and storage. pathways by which a chemical substance moves through abiotic and biotic components of Earth.

NITROGEN CYCLE

Nitrogen enters the world from atmosphere through N-fixing bacteria. Nitrogen and nitrogenous waste from animals is processed back into gaseous nitrogen by soil. Supplies terrestrial food webs.

CARBON CYCLE

Carbon enters living world from atmosphere via photosynthesis. Becomes incorporated in plants and biotic interactions. Organic Carbon is processed back into gaseous CO2 by soil bacteria and fungi during decomposition.

PHOSPHORUS CYCLE

Phosphorus enters living world through weathering rock. Phosphate gets taken up by plants, gets into animals and decomposers. Decomposers return phosphate to soil and solution.