Question

The body plan in which the alimentary canal has a single opening is known as
A) Cell aggregate body plan
B) Blind sac body plan
C) Tube within tube plan
D) All of the above

Answer 1

Hint: There is a digestive cavity and a single opening in this category of body plan which works both as a mouth and an anus. However, the digestive system is found mostly incomplete. Example of this body plan is found in Phylum Cnidaria.

Complete Answer:
- There are 3 types of animal body plans. These are cell aggregate body plan, blind sac body plan and tube within tube plan.
- The body consists of a cluster of cells in a cell aggregate body plan which are not organized into tissues or organs. It is found in sponges.
- The body has a single cavity in a blind sac plan which functions as digestive tract and coelom. The alimentary canal has a single opening as both mouth for ingestion and anus for egestion. It shows tissue grade body organisation. The cells are organised into tissues. It is found in coelenterates.
- In a tube within a tube body plan, the digestive tract is continuous and has two openings, a mouth for ingestion and anus for egestion. The body plan is termed as the tube within a tube due to the presence of the digestive canal inside the body cavity. It is found in the earthworm.

Hence, The option B: Blind sac body plan is the correct answer.

Note: The alimentary canal has a single opening called blind sac body plan. There is a digestive cavity and a single opening in this category of body plan which works both as a mouth and an anus.