Question

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

a.)Bilateral symmetry allowed animals to evolve nerves.
b.)Radial symmetry is more advantageous for active swimming than is bilateral symmetry.
c.)Bilaterally symmetric animals can be streamlined for swimming, but radially symmetric animals cannot.
d.)Radial symmetry occurs most frequently in animals that catch their prey by rapid swimming.

Answer 1

The correct answer is: c.)Bilaterally symmetric animals can be streamlined for swimming, but radially symmetric animals cannot.

In radial symmetry the body can be divided by several cutting planes that produce roughly identical pieces. Organisms with such symmetry are usually cylinder, with no left or right sides only top and a bottom surface. Radial symmetric organisms are symmetrical about an axis that goes from the center of the oral (top) surface, to the center of the opposite (bottom) end. It is suitable for sessile animals or slow moving animals.

In bilateral symmetry one plane can divide an organism into roughly mirror image halves (the right and left halves). One of the advantages of the organisms with bilateral symmetry is the streamlining of the body.