Question

If you cut planaria vertically, you will get two equal halves. What does this indicate?

• A. The organism is asymmetrical.
• B. The organism is radially symmetrical.
• C. The organism is bilaterally symmetrical.
• D. None of the above

Answer 1

The correct option is C The organism is bilaterally symmetrical.

$\bullet$ Bilateral symmetry: If an organism is cut through the central axis of any one plane of its body, the resulting halves would be identical. E.g., Planaria, liverfluke, etc.
$\bullet$ Radial symmetry: When an organism is cut through the central axis at any plane, both the halves will show the same design. Eg., Hydra, starfish.
$\bullet$ Asymmetry: Organisms will not show symmetry. E.g., Euplectella, sycon, sponges, etc.