Page 7 - 11-Bio-7 The Kingdom protista

7. The Kingdom Protista (or protoctista) eLearn.Punjab

Parasitic flagellates cause diseases. For example
Trypanosoma is a human parasite causing African sleeping
sickness. It is transmitted by the bite of infected tsetse fly
( Fig. 7.3 b)

Choanoflagellates are sessile marine or freshwater
flagellates which are attached by a stalk and their single
flagellum is surrounded by a delicate collar. They are of
special interest because of their striking resemblance to
collar cells in sponges (Fig. 7.4).

Fig. 7.4 A colonial choanoflagellate

(c) Ciliates

Ciliates are unicellular organisms with a flexible outer covering called a pellicle that gives them
a definite but changeable shape. In Paramecium, the surface of the cell is covered with several
thousand fine, short, hair-like structures called cilia. The cilia beat in such a precisely coordinated
fashion that the organism can go forward, can also go back and turn around.

Some ciliates are sessile and remain attached to a rock or other surface. Their cilia set up water
currents that draw food towards them. Most ciliates ingest bacteria or other tiny protists.

Animation 7.5: Ciliates V: 1.1
Source and Credit: microscopy-uk

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