Question

If the body has a single cavity with only one opening to the outside, then it is called

• A. cell aggregate body plan
• B. blind sac body plan
• C. tube-within-a-tube body plan
• D. protostomic body plan

Answer 1

The correct option is B blind sac body plan

Animals have three different body plans - cell aggregate body plan, blind sac body plan and tube-within-a-tube body plan.

The cell aggregate body plan consists of a cluster or aggregation of cells which has rudimentary differentiation but is not organized into organs. Example - sponges.

In a blind sac body plan, the body of the animal has a single cavity with one opening to the outside. Example - coelenterates and flatworms.

In tube-within-a-tube body plan the body of the animal consists of two tubes, one formed by the body wall and second formed within it by the digestive tract. Example - Ascaris.

Protostomic plan is a type of tube-within-a-tube plan where the mouth of the digestive tract develops first in the embryo and anus is formed later. Examples - roundworms, earthworm, crab and snail.