Question

Blind sac body plan is shown by
A. Roundworms
B. Annelids
C. Coelenterates
D. Arthropods

Answer 1

Hint:- Blind sac body type is when the organism has only one opening for the ingestion and egestion of food and waste materials. Such a type of digestive system is primitive and is known as an incomplete digestive system. The animals having this type of digestive system have the tissue level of organisms.

Complete answer:
The blind sac body plan is seen in the coelenterates. This body plan has a single opening for taking in food and expelling out the waste products. The coelenterates have tissue levels of the body organization. They have a large gastrovascular cavity that performs the function of the small intestine in them. This cavity helps in the digestion of food as well as helps in circulation. Their body is usually cylindrical. They have radial or bilateral symmetry present on them. They are diploblastic. Their mouth opening is surrounded by the tentacles which have nematocysts present on them. Their mode of nutrition is mostly holozoic. The digestion in them is both intracellular and extracellular. They usually remain attached to the substratum of the ocean bed. They attach themselves to the rocks or the floor of the ocean. They reproduce both by the means of asexual and sexual reproduction. They possess polymorphism in their life cycle.
So, the correct answer is option C. Coelenterates.

Note:- The coelenterates are also known as the cnidarians. Their body has a single aperture present which acts as a mouth and anus. This opening is guarded by the tentacles present which help them in catching the prey and feeding onto them. The tentacles release a venom that paralysis their prey making it easy for them to feed onto them.