Question

All of the following statements about bilateral symmetry are true, except

• A. Body can be divided into two equal halves by a single plane only
• B. The organisms that show bilateral symmetry have paired body organs that occur on the two sides of a central axis
• C. It is found in all invertebrates and few vertebrates
• D. Spider and crab show bilateral symmetry

Answer 1

Answer: (C)

Symmetry is the repetition of the parts in an animal or plant in an orderly fashion. In animal kingdom, the following main types of symmetry are observed:

1. Phylum Porifera is asymmetrical and the body cannot be divided into two halves.
2. Phyla like Coelenterata, Ctenophora and Echinodermata show radial symmetry. They body can be divided into two equal portions only when cut through their radius.
3. Phyla like Platyhelminthes, Aschelminthes, Annelida, Arthropoda, and all Chordates show bilateral symmetry.

Thus, bilateral symmetry is found in few invertebrates and all vertebrates.