Which of the following options does correctly represent the characteristic features of phylum Annelida?
A
Triploblastic, unsegmented body and bilaterally symmetrical
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B
Triploblastic, segmented body and bilaterally symmetrical
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C
Triploblastic, flattened body and acoelomate condition
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D
Diploblastic, mostly marine and radially symmetrical
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Solution
The correct option is B 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.