Question

The subkingdom parazoa consists of
A. Radially symmetrical sponges, jellyfishes and their relatives.
B. Only animals that do not feed by ingestion.
C. Animals with protostome-type development.
D. Animals lacking tissues and organs.

Answer 1

Parazoa is the animal subkingdom that includes organisms of the phylum porifera and parazoa. Example: Sponges. The three main types of sponges are glass sponges, calcareous sponges and demosponges.

Complete answer:
The subkingdom parazoa consists of ‘animals’ lacking tissues and organs. Cell is the basic structural and functional unit of life. Cell forms the base level of organization. On the basis of the number of cells, animals are categorized as unicellular organisms and multicellular organisms.

(a) Unicellular organisms: These are single celled organisms. Example: Amoeba. A single cell performs all the functions.
(b) Multicellular organisms: The organisms that possess more than one cell are called multicellular organisms. Example: mammals, plants etc. These cells combine to form tissue. Tissues organize to form organs. Organs combine to form an organ system which forms the body of an organism i.e. the organisms that are made up of many cells. The structure is less specialized. It is less evolved as compared to metazoan. It includes sponges. Sponges belong to phylum porifera. Porifera is named as the basis of the pore-bearing structure these animals possess. The organisms belonging to this phylum do not possess tissue. These organisms are radially symmetrical. Example: Sponges but jellyfish belong to the phylum cnidaria. Cnidaria is also known by the name coelenterata.

Therefore, the correct answer is option (D) Animals lacking tissues and organs.

Note: There are numerous structures present on the body surface of sponge’s called ostia. Osculum is the opening present at the other end. Sponges possessing their body will have made up of pinawderm, morphyl and choanoderm asconoid sponges are simplest sponges.