Question

Which of the following options correctly represent the characteristic features of phylum Annelida?

• A. Triploblastic, segmented body and bilaterally symmetrical
• B. Diploblastic, mostly marine and radially symmetrical
• C. Triploblastic, unsegmented body and bilaterally symmetrical
• D. Triploblastic, flattened body and acoelomate condition

Answer 1

The correct option is A Triploblastic, segmented body and bilaterally symmetrical

Characteristic features of phylum Annelida:

• They are triploblastic as they have three germ layers (ectoderm, mesoderm and endoderm) during their embryonic development.
• They exhibit bilateral symmetry as the body of these organisms can be cut into two equal halves in only one plane i.e., the median sagittal plane.
• Body of annelids is segmented both externally and internally. The characteristic feature of this phylum is metamerism. Linear repetition of certain body parts is called metamerism.
• Annelids are coelomates as they have a body cavity between alimentary canal and body wall and it is lined by mesoderm on all sides.

Hence, option b is correct.