Question

Members of which phylum are deuterostomes?

• A. Mollusca
• B. Echinodermata
• C. Arthropoda
• D. Annelida

Answer 1

The correct option is B Echinodermata

Animals are classified into protostomes and deuterostomes based on whether the mouth develops first or the anus.

In Protostomes, the mouth develops first from the blastopore. Blastopore is the opening of the archenteron, which is formed during the gastrula stage. Anus develops later. As the mouth is formed first, these animals are called protostomes. ‘Proto’ means first and ‘stoma’ means mouth. Protostomes include annelids, arthropods and molluscs.

In deuterostomes, blastopore develops into anus and the mouth is formed later. As the mouth is formed as a secondary opening, these animals are called deuterostomes. ‘Deutero’ means secondary and ‘stoma’ means mouth. Deuterostomes include echinoderms, hemichordates and chordates.