Classifying a specimen needs a step-by-step study of its body plan and features. Biologists carefully observe both external and internal characteristics before placing it into a phylum.

Steps for Classification

1. Body symmetry – Is it asymmetrical, radial, or bilateral?

2. Germ layers – Check if it is diploblastic (2 layers) or triploblastic (3 layers).

3. Body cavity (coelom) – Find out whether it is acoelomate, pseudocoelomate, or coelomate.

4. Segmentation – Look for repeated body segments (as in Annelids).

5. Digestive system – Whether incomplete (one opening) or complete (two openings).

6. Skeleton/support – Endoskeleton, exoskeleton, or absent.

7. Other features – Nervous system, circulatory system, and reproduction.