Nitrogen Cycle

Nitrogen Cycle
Nitrogen is a component of
amino acids, proteins, and
nucleic acids and often limits
plant nutrient. Through the
cycle, various forms of
nitrogen are formed such as
ammonium, nitrate, and
nitrite. Plants use ammonium
and nitrate, and various
bacteria use nitrite. Animals
can only use organic forms
of nitrogen.
Pesticides in the soil effects
nitrification. Some herbicides
temporarily interrupt nitrification. In
other experiments, chemicals such
as BHC (benzene hexachloride),
aldrin, lindane, heptachlor, and
DDD prevent nitrogen-fixing
bacteria from forming the
necessary root nodules of
legumes. Such changes in the soil
could alter metabolic activity and
affect productivity. This means that
harmful organisms that were once
in check could rise to pest status.
Phosphorus Cycle
• Organisms need
phosphorus as a
constituent of nucleic
acids, phospholipids,
and ATP and other
molecules. Plants use
phosphate to
synthesize organic
Biological Magnification
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Biological Magnification is a process
when certain substances like pesticides,
move higher up in the food chain and
work their into bodies of water where
they are consumed by aquatic organisms
such as fish, which are then eaten by a
larger organisms. As the chemical
substances move up the food chain they
become more concentrated in tissues
and internal organs.
In Silent Spring, Rachel Carson describes
different scenarios in which the humans
want to get rid of another organism
(usually an insect) that is causing an
inconvenience. Since the ‘pest’ isn’t
always the one hurt it still has the toxic
chemicals inside it, causing anything that
eats it to be poisoned. What then
happens is it usually goes into the
humans and we end up hurting
Water Cycle
Carbon Cycle
Nitrogen Cycle
Phosphorus Cycle
AP* Edition Biology Seventh Edition
-Neil A.Campbell and Jane B. Reece