Question

A colonial protozoan having choanocyte like flagellate cells that form a connecting link between protozoa and Porifera is
A. Protoflagellate
B. Amoebospongia
C. Proterospongia
D. Phanerospongia

Answer 1

Hint: The living animals which possess the characteristics of two different groups of animals are known as connecting links. Protozoa is a group of single-celled eukaryotes, either free-living or parasitic, which feed on organic matter such as other microorganisms or organic tissues and debris. Phylum Porifera are the lowest multicellular animals belonging to the kingdom Animalia.

Complete answer:
Proterospongia is a genus of single-celled aquatic organisms that form colonies. It belongs to the choanoflagellate class. The choanoflagellates are free-living aquatic organisms that range from unicellular to colonial species and resemble choanocytes, the flagellated collar cells of sponges. Proterospongia falls between Protozoa and Porifera since many collared and amoeboid cells live in a common matrix as in sponges. The collar usually is made of microvilli that surround the single flagellum and serves as a filter for catching particles caught in the vortex created by the flagellum. The arrangement of organelles in Proterospongia appears consistent with other choanoflagellates and is characterized by an anterior dictyosome under the flagellar base, a central nucleus, peripheral mitochondria, and a posterior food vacuole.
So, the answer is C, i.e., Proterospongia

Note: As a colony-forming choanoflagellate, Proterospongia is of interest to scientists studying the mechanisms of intercellular signaling and adhesion present before animals appeared. Proterospongia species are distinguished by colony morphology, which varies from simple chains of cells to striking astral assemblages.