Question

Which one of the following group of animals are bilaterally symmetrical and triploblastic?

• A. Sponges
• B. Coelenterates (Cnidarians)
• C. Aschelminthes (roundworms)
• D. Ctenophores

Answer 1

The correct option is C Aschelminthes (roundworms)

Aschelminthes are a group of animals that are bilaterally symmetrical and triploblastic. They are pseudocoelomates. The false coelom lies between the body wall and alimentary canal. So if a live earthworm is pricked with a needle on its outer surface without damaging the gut then only coelomic fluid will come out.

Sponges and Cnidarians are radially symmetrical and Ctenophores are biradially symmetrical.
Sponges have one germ layer, Cnidarians and Ctenophores have two germ layers.