Question

What of the following are correct statements/s?
(a) Obelia shows alternation of polyp and medusa form in their life cycle
(b) Mesoglea is always seen between mesoderm and endoderm
(c) Hydra has the simplest form of nervous system in the form of nerve net
(d) Digestion in Hydra is first extracellular and then intracellular

• A. a & b
• B. a, c & d
• C. a, b & c
• D. all of these

Answer 1

Answer: (B)

a, c & d

Correct answer is B.

Obelia is a Cnidarian marine hydrozoan, which have both polyp and medusa stages in alternating form.

The mesoglea is a gelatinous layer found between the external (ectoderm) and internal (endoderm) cellular layers of a cnidarian (eg, sponge).

Hydra is a non-bilaterian organism with the simplest form of nervous system. it has a diffuse nerve net which is spread throughout its body.

In Hydra, the food is entered through the mouth (extracellular digestion), and reaches the hollow cavity or the gut, where the enzymes are released by special cells in the endodermis to digest and break the food particles into further smaller particles (intracellular).