Nitrogen makes up 78% of the atmosphere it is also an essential nutrient for all
Nitrogen fixation - Most organisms can’t use atmospheric oxygen, but certain
bacteria transfer it into other compounds like ammonia (NH4). Ammonia can then
be used as a source of nitrogen for other organisms. Lightning also fixes a small
amount of nitrogen.
Assimilation - Nitrogen that is fixed can then be used by plants where it is then
transferred to animals who eat the plants.
Nitrification - Is the process of turning ammonia into nitrates or nitrites. It is
carried out by b acteria.
Denitrification - Other bacteria take organic nitrogen and nitrates and turn it
back into gaseous nitrogen.
Effects of Excess Nitrogen
The burning of fossil fuels and the use of
manufactured fertilizers increase nitrogen on
land in the atmosphere and in oceans.
Ammonia (NH3) in the atmosphere has tripled
from human activity. This has led to water and
air pollution and in some cases acid rain.
Nitrogen Cycle Video
The process by which one natural community
changes into another over a time scale of
years to centuries is called succession.
Succession represents a natural transition
from r- K-selected species.
Referring to colonization of a newly exposed
landform, such as sand dunes or lava flows
after a volcanic eruption.
Describing the return of an area to its natural
vegetation following a disturbance such as fire,
treefall, or forest harvesting.
Change driven by the inhabitants of an
ecosystem, such as forests re-growing on
abandoned agricultural fields.
Change driven by new external geophysical
conditions such as rising average temperatures
resulting from global climate change.
Key Terms (Continued) Maribeth Villanueva
Adaptation- make (something) suitable for a
new use or purpose; modify.
Adaptive trait- a trait with a current functional
role in the life history of an organism that is
maintained and evolved by means of natural
Age structure- A population pyramid, also
called an age pyramid or age picture diagram,
is a graphical illustration that shows the
distribution of various age groups in a
population, which forms the shape of a pyramid
when the population is growing
Age distributions- the distributions of age in a
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