Biological Classification
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ÇHRÝSØPHÝTËS
Found in
fresh water
and marine
environments.
Microscopic
and float
passively in
water currents
(plankton).
Most of
them are
photosynthetic.
It includes
diatoms &
golden algae
(desmids).
They have siliceous cell walls forming two thin
overlapping shells, which fit together as in a soap
box (AIPMT 2015). The left behind cell wall deposit of
diatoms over billions of years in their habitat is known
as ‘diatomaceous earth’. (NEET-II 2016) This is used in
polishing and filtration of oils and syrups. Diatoms are
the chief ‘producers’ in the oceans.
Diatoms
DÏÑØFLÅGËLLÅTËS
Mostly marine and photosynthetic.
They appear yellow, green, brown, blue or red based
on the main pigments present in their cells.
The cell wall has stiff cellulose plates on the outer
surface.
Most of them have 2 flagella; one lies longitudinally and the other
transversely in a furrow between the wall plates.
Red dinoflagellates (E.g. Gonyaulax) undergo rapid multiplication so
that the sea appears red (red tides).
They release toxins that kill marine animals like fishes.
ËÜGLËÑØÏDS
Mainly fresh water organisms found in
stagnant water.
Instead of a cell wall, they have a protein
rich layer called pellicle. It makes their
body flexible.
Dinoflagellates
Euglena