Monera: The Mysterious Life Forms part 2 #neet #tips #tricks

Monera: The Mysterious Life Forms part 2 #neet #tips #tricks
BIOLOGICAL CLASSIFICATION 13
Though the bacterial structure is very simple, they are very complex
in behaviour. Compared to many other organisms, bacteria as a group
show the most extensive metabolic diversity. Some of the bacteria are
autotrophic, i.e., they synthesise their own food from inorganic substrates.
They may be photosynthetic autotrophic or chemosynthetic autotrophic.
The vast majority of bacteria are heterotrophs, i.e., they depend on other
organisms or on dead organic matter for food.
2.1.1 Archaebacteria
These bacteria are special since they live in some of the most harsh habitats
such as extreme salty areas (halophiles), hot springs (thermoacidophiles)
and marshy areas (methanogens). Archaebacteria differ from other bacteria
in having a different cell wall structure and this feature is responsible for
their survival in extreme conditions. Methanogens are present in the gut
of several ruminant animals such as cows and buffaloes and they are
responsible for the production of methane (biogas) from the dung of these
animals.
Figure 2.2 A filamentous blue-green
algae – Nostoc
2.1.2 Eubacteria
There are thousands of different eubacteria or ‘true
bacteria’. They are characterised by the presence of a
rigid cell wall, and if motile, a flagellum. The
cyanobacteria (also referred to as blue-green algae)
have chlorophyll a similar to green plants and are
photosynthetic autotrophs (Figure 2.2). The
cyanobacteria are unicellular, colonial or filamentous,
freshwater/marine or terrestrial algae. The colonies
are generally surrounded by gelatinous sheath. They
often form blooms in polluted water bodies. Some of
these organisms can fix atmospheric nitrogen in
specialised cells called heterocysts, e.g., Nostoc and
Anabaena. Chemosynthetic autotrophic bacteria
oxidise various inorganic substances such as
nitrates, nitrites and ammonia and use the released
energy for their ATP production. They play a great role
in recycling nutrients like nitrogen, phosphorous,
iron and sulphur.
Heterotrophic bacteria are most abundant in
nature. The majority are important decomposers.
Many of them have a significant impact on human
affairs. They are helpful in making curd from milk,
production of antibiotics, fixing nitrogen in legum
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