Question

The distinguishing feature of animals in phylum Annelida is

• A. round cross section
• B. absence of coelom
• C. dorsoventrally flat
• D. metameric segmentation

Answer 1

The correct option is D metameric segmentation

Phylum Annelida consists of earthworms, leeches, etc. Their bodies are divided into segments both internally and externally. This is known as metamerism and is particularly seen in this phylum. Hence, metamerism is the phenomenon of having a linear series of body segments fundamentally similar in structure. For example, excretory organs (nephridia) are repeated serially in the segments.

Round cross section is a peculiar feature of animals in phylum Aschelminthes.
Absence of coelom is seen in organisms of phylum Porifera, Coelenterata, Cnidaria and Aschelminthes.
Dorsoventrally flat structure, i.e. body is flat from both surfaces lower and upper surfaces, is a peculiar feature of organisms belonging to phylum Platyhelminthes. For example, Taenia.