Organisms which exhibit autotrophic nutrition are
called Autotrophs. These organisms are able to synthesise their nutrients from
simple inorganic compounds.
They require minerals, water and carbon dioxide for
their growth. They are capable of converting carbon dioxide into various
complex organic compounds.
However, they require energy for this purpose.
Depending on how they obtain the energy for converting carbon dioxide to
organic compounds, there are two types of autotrophs – photoautotroph and chemoautotroph.
PHOTOAUTOTROPHIC ORGANISMS:
Several bacteria(such as green bacteria, purple
bacteria and cyanobacterial) can use light as a source of energy and synthesise
complex organic molecules.
Similarly, All the algae and higher plants use light
as source of energy. These autotrophic organisms are called photoautotrophic
organisms
(photo=light.)
These organisms have special pigments is their body
to trap the light energy which drives other reactions.
CHAEMOAUTOTROPHIC ORGANISMS:
Second group of autotrophs are chemoautotrophs.
These organisms obtain energy by oxidizing simple inorganic compounds.
Such as hydrogen, iron containing compounds,
sulphur, hydrogen sulphide, ammonia, nitrite, and other nitrogen containingcompounds. However, all these organisms require carbon dioxide as a source of
carbon atoms.
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