Question

Which one of the following statements about all the four Spongilla,leech, dolphin and penguin is correct?

(a) Penguin is homiothermic, while ihe remainrng three are poikilothermic

(b) Leech is a freshwater form, while all others are marine

(c) Spongilla has special collared cells called choanocytes, not found in the remaining three

(d) All are bilaterally symmetrical

Answer 1

Correct option (c) Spongilla has special collared cells called choanocytes, not found in the remaining three

Explanation:

Spongilla belongs to phylum-Porifera, in which, choanocytes are the characteristic cells, these are absent in leech, dolphin and pengiun. These distinctive cells line the interior body walls of sponges.

These cells have a central flagellum that is surrounded by a collar of microvilli. Choanocytes are versatile cells.

Their flagella **** to create the active pumping of water through the sponge, while the collars of the choanocytes are the primary areas where nutrients are absorbed into the sponge.