Question

Collar cells occur in
A. Sponge
B. Hydra
C. Sandworm
D. Starfish

Answer 1

The various types of organisms in the world are placed under some rankings and phyla according to the characters they have. Their morphology, anatomy, and functioning can make them placed in different categories. They have different types of cells performing the regular metabolisms like respiration, excretion or circulation.

Complete answer:
Collar cells are also called choanocytes. They are the specialized cells which are flagellated and form the inner body layer called choanoderm.
Their major function is to provide nutrition, they also help in respiration, excretion and circulation process. This is a defining feature of the Phylum Porifera.

Option A: Sponges: they are the primitive creatures having a single-celled body usually or a very simple body organization. They have ostia on their body. Collar cells or choanocytes are the characteristic features of the sponges.

Option B: Hydra: They are freshwater aquatic organisms belonging to the Cnidaria group. They have the regenerative capability for which they are known.

Option C: Sandworm: They belong to the Annelida phylum. They have a segmented body and can respire via their skin. They are found in the soil digging the surface.

Option D: Starfish: They are star-shaped organisms belonging to the phylum Echinodermata. They are called brittle stars. It is poisonous for the living creatures.

Hence, the correct answer is option (A).

Note: The sponges lack tissues but have cells to carry out all the basic metabolisms. Water enters through the ostia and takes out all the extra toxic material from the body. They are usually immobile. They feed on the detritus from the water.