Diversity In Living Organisms — Science STD 9 — Question

1. Triploblastic, bilaterally symmetrical and metamerically segmented animals.
2. Body segments are grouped into two regions-cephalothorax (head and thorax together) and abdomen, or three regions-head, thorax and abdomen. Anterior part of body forms a distinct head, bearing sense organs and brain.
3. Exoskeleton of cuticle, containing protein, lipid, chitin and often calcium carbonate is secreted by underlying epidermis and shed (moulted) at intervals.
4. Alimentary canal is complete, mouth and anus lie at opposite ends of the body.

Example: Palaemon (prawn) and Peripatus.