Question

Platyhelminthes is the first phylum to show

• A. bilateral symmetry
• B. organ level of organisation
• C. triploblastic development
• D. all the above

Answer 1

The correct option is D all the above

Platyhelminthes exhibit bilateral symmetry as their body can be divided into two identical halves in a single plane. They have an organ level of organization where the tissues are modified to form well-defined organs that perform specific functions. Platyhelminthes exhibit a triploblastic level of organization with three germ layers - the outermost ectoderm layer, the innermost endoderm layer, and the middle mesoderm layer.

Coelenterata and Ctenophora show tissue level of organization and are diploblastic organisms that are radially symmetrical.
Poriferans, on the other hand, are asymmetrical and display a cellular level of organization.