Biogeochemical
cycle
We know
that environment is the source of materials for all living organisms.
Environment provides bioelements which are used by organisms for their bodies
and metabolism. The materials are continuously recycled between organisms and environments.
Biogeo chemical cycle is path way from a compound entered the environment by
organism and also released from the environment.
1: carbon cycle
Carbon atom is the principle building block of many kinds of bimolecular.
Carbon is found as many graphite and diamond nature. It is also occurs as
carbon dioxide in atmosphere.
A major source of carbon for the living world is carbon dioxide present
in atmosphere and water. Fossil fuels like peat, coal, natural gas and
petroleum also contain carbon. Carbonates of earth’s crust also give rise to
carbon dioxide.
The major process that brings the carbon from atmosphere or water into
living world is photosynthesis. Producers take in carbon dioxide from
atmosphere and convert it into organic compounds. In this way, carbon becomes a
part of body of producers. The carbon enters food chains and is passed to
herbivores, carnivores and decomposers.
Carbon dioxide is released back to environment by respiration of
producers and consumers. It is also released by the decomposers of organic
wastes and death bodies of decomposers. Burning of woods and fossil fuels also
adds large amount of carbon dioxide into atmosphere.
2: nitrogen cycle
Nitrogen is an important component of many bioelements, like proteins and
nucleic acid. Atmosphere is the reservoir of free gaseous nitrogen. Living
organisms cannot pick this gaseous nitrogen directly from the atmosphere
(expect from nitrogen fixation bacteria). It has to convert into nitrates to be
utilized by plants.
A: formation of
nitrates
It is almost done by the following ways
·
Nitrogen
fixation: conversion of nitrogen into nitrates is called nitrogen fixation. It
occurs in the following ways.
1.
The
thunderstorms and lightning convert atmospheric gaseous nitrogen to oxides of
nitrogen. These oxides dissolve in water and form nitrous acid and nitric acid.
The acids in turn combine with other salts to produce nitrates. It is called
atmospheric nitrogen fixation.
2.
Some
bacteria also have the ability to transform gaseous nitrogen into nitrates. The
process is called as biological nitrogen fixation. Some of these nitrogen
fixation bacteria live as symbionts and many are free-living.
3.
Nitrogen
fixation is also done by industries. In industries nitrogen fixation hydrogen
is combined with atmospheric nitrogen under high pressure and tempreture.it
produces ammonia which is further converted into ammonium nitrates.
A: ammonification and nitrification
Ammonification
is the breakdown of the protein of dead organisms and nitrogenous wastes to
ammonia. It is done by ammonifying bacteria.
After the
formation of ammonia, it is converted into nitrates by bacteria. The nitrates
are then converted into nitrates by the other bacteria.
B: assilimatiom
The
nitrates formed by the above processes, are absorbed by plants and are utilized
for making proteins. Animals take nitrogenous compounds from plants. The
utilization of nitrates by organism is called assimilation.
C: Gentrification
It is a
biological process in which nitrates and nitrites are reduces to nitrogen gas
by denitrifying bacteria. By this process, nitrogen is returned to atmosphere.
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