Question

Paragastric cavity is related to
A. Sponge
B. Coelenterata
C. Nematoda
D. All of the above

Answer 1

Hint: It is a cavity in which the radial canals enter and opens outwards through the cloaca. It does most of the work by a single opening. Thus making it a less complex organism. As higher animals would require a closed circulatory system.

Complete solution : What is a paragastric cavity? From the word gastric we can estimate that paragastric is a cavity (hollow space) near the stomach opening out through cloaca.
We have a kingdom Animalia which has some phylum. Some of them are Porifera, Nematoda, cnidaria etc
Now let us learn the key features of the phyla in the options.

Option A: Sponge: Sponges are the members of the phylum Porifers. They have a lot of pores and openings on their skin. They are the simplest organisms. The water can pass through their body to filter out all the excretions and filter the blood through the cloaca.
Option B: Coelenterata: They belong to the phylum Cnidaria. They have a single hollow body cavity called coelenteron which is used to capture the prey.
Option C: Nematoda: They are the non-segmented worms. They lack true coelom (cavity). The respiratory process occurs through the general body surface.
The enlisted features show that only the sponges fall in the category which has the cavities for performing most of the work. As cnidaria perform only prey catching tasks by the cavity.
> So, the correct answer is option A) Sponge.

Note: Cloaca is the orifice that is the only way to the digestive, urinary, reproductive and excretion tracts. It is a feature of vertebrate animals. Some of the examples of sponges are Demosponge, Calcareous sponge. Some coelenterates are moon jelly, barrel jellyfish. Ascaridida, Enoplea are some of the nematodes.