Question

Why do echinoderms posses radial symmetry in embroynic stage but transform to bilateral symmetry in adult?

Answer 1

Echinoderms posses bilateral symmetry in embroynic stageand radial symmetry in adult.
The larvae of echinoderms have bilateral symmetry but this is lost during metamorphosis when their bodies are reorganized and develop the characteristic radial symmetry of the echinoderm.
Echinoderm larvae are ciliated, free-swimming organisms that organize in bilateral symmetry which makes them look like embryonic chordates. Later, the left side of the body grows at the expense of the right side, which is eventually absorbed. The left side then grows in a pentaradially symmetric fashion, in which the body is arranged in five parts around a central axis.