Question

Collar cells occur in
(a)Sponges
(b)Hydra
(c)Sandworm
(d)Starfish

Answer 1

Hint: The organism belongs to the phylum Porifera. It is aquatic and is sessile and sedentary attached to a substratum. It is a multicellular organism with a cellular level of organization.

Complete answer:
Collar cells are found in sponges They are also called Choanocyte. This feature is unique and is present in sponges only. Choanocyte or collar cells line the spongocoel of the sponges. They contain a central flagellum surrounded by a collar of microvilli which is connected by a thin membrane. They collectively make a layer called a Choanoderm, a type of cell layer found only in sponges.

Additional Information:
 -By cooperatively beating the flagella, the collar cells filter particles out of the water and into the spongocoel and out through the osculum.
-The flagella beat regularly creates the water flow across the microvilli which filters nutrients from the water taken from the collar of the sponge. Here the phagocytosis of the food particles takes place.
-This improves both the respiration and digestion of the sponge by pulling oxygen and nutrients and allowing the expulsion of carbon dioxide and waste products.
-According to the body plan, spongocoel has a various lining, they are: on the surface of the spongocoel (asconoid sponges), radial canals in syconoid sponges, and chambers like in leuconoid sponges.

So, the correct answer is ‘Sponges’.

Note: They carry out most of the ingestion of sponge and pass the digested material into the amoebocytes for the delivery to the other cells.
Although the sponges reproduce by asexual reproduction through fragmentation choanocyte can also turn into spermatocyte and play an important role in reproduction.