Question

Which one of the following is exclusively marine?

• A. Mollusca
• B. Echinodermata
• C. Aschelminthes
• D. Coelenterate

Answer 1

The correct option is B

Echinodermata

The correct option is B.

Explanation of the correct option :

1. Echinodermata is a phylum of organisms containing spiny skinned bodies and are exclusively marine animals.
2. Echinodermata consists of a water vascular system in which water enters through madreporite (a perforated plate).
3. The functions of the water vascular system are locomotion, respiration, sensory, and excretion.
4. Excretory organs are not present. For e.g. Starfish, Holothuria (sea cucumber), etc.

Explanation of the incorrect option :

Option A:

1. Mollusca is the second largest phylum of the animal kingdom. They have soft bodies covered with a hard shell.
2. They can be terrestrial, marine, or freshwater, for example, octopus and snails.

Option C:

1. Aschelminthes are also called roundworms as their cross-sections are round in shape.
2. They can be aquatic or terrestrial, free-living, or parasitic, for example, Ascaris.

Option D:

1. Coelenterates are aquatic animals that can be either non-motile or free-swimming.
2. They got the name due to the presence of specialized cells called cnidoblasts or cnidocytes on their body, for example, Hydra and jellyfish.

Final answer: Echinodermata is exclusively marine animals.