Question

Which of the following statements comparing symmetry in sessile and swimming animals is most probable?

- Radial symmetry occurs most frequently in animals that catch their prey by rapid swimming.

- Bilaterally symmetric animals can be streamlined for swimming, but radially symmetric animals cannot.

- Bilateral symmetry allowed animals to evolve nerves.

- Radial symmetry is more advantageous for active swimming than is bilateral symmetry.

Answer 1

Radially symmetrical is suitable for all those animals that either does not move or largely dependent on the water current system. The body plan of such animals does not evolutionary supported for habitat change, search and chase for food, mate or run away from predators. Hence, the statement 'Radial symmetry occurs most frequently in animals that catch their prey by rapid swimming' is not appropriate. On the contrary, the statement ' Bilaterally symmetric animals can be streamlined for swimming, but radially symmetric animals cannot' is correct and appropriate for this comparison.
This is true that 'Bilateral symmetry allowed animals to evolve nerves', however, similar comparable description for sessile animals is missing in the statement. Swimming velocity is largely regulated by limbic assistance, which is only possible if the animal is bilaterally symmetrical and not appropriate for the animals with radial symmetry. Hence, the statement 'Radial symmetry is more advantageous for active swimming than is bilateral symmetry' is not true.
Depending upon all the stated comparison 'Bilaterally symmetric animals can be streamlined for swimming, but radially symmetric animals cannot.'- is the most suitable and proper statement while comparing the symmetry in sessile and swimming animals.