Question

Which one of the following groups of animals is bilaterally symmetrical and triploblastic ?

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

Answer 1

The correct option is D

Aschelminthes (roundworms)

The correct option is D.

Explanation for correct answer:

1. Bilateral Symmetry refers to the division of a body into two equal halves in such a way that both halves are mirror images of each other or the same on both sides of an axis.
2. Triploblastic refers to the organisms whose body is derived from three germ layers ie. Ectoderm, Endoderm and Mesoderm.
3. Examples- mollusks, flatworms, arthropods, and chordates.

Explanation for incorrect answers:

Option A

Coelenterates have the structure of radial symmetry and it is diploblastic.

Option B

Sponges are unsymmetrical or radially symmetrical and diploblastic.

Option C

Ctenophores are biradial symmetry and diploblastic.

Final Answer: Aschelminthes are bilaterally symmetrical and triploblastic.