Question

Radial cleavage is found in
A. Tunicates
B. Protozoan
C. Coelenterates
D. Annelids

Answer 1

The organisms are having asymmetry which divides them into equal or unequal parts in a particular plane/axis. They are specified under the categories of radial, bilateral or asymmetrical. This cleavage can be helpful for them in adapting to the environment they live in. Their movement depends on this to a very large extent.

Complete answer:
Radial cleavage is the holoblastic cleavage. It is featured by the arrangement of the blastomeres directly over the lower tier resulting in the radial symmetry. It is a feature of deuterostomes. This radial symmetry moves around the pole to pole axis of the embryo making a 90-degree angle.

Option A - Tunicates: Tunicates have bilateral symmetry. They are the chordates. They form the marine invertebrate animals.

Option B - Protozoans: They will have radial, bilateral and asymmetrical cleavage. Some of the organisms have any one type of symmetry. They are primitive characters.

Option C - Coelenterates: They have a characteristic feature of the radial symmetry or cleavage having the blastomeres arranged in the radial form.

Option D - Annelids: they have bilateral symmetry/cleavage with segmentation and presence of coelom. They are triploblastic and have parapodia for movement.

Hence, the correct answer is option (C).

Note: The coelenterates are aquatic mostly. They have radially symmetrical bodies lacking the cavity called coelom. They have a hypostome that is the only opening with tentacles around it. They help them to capture and sense the prey. They have coelenterates to breathe, this is their internal cavity to exchange the gases.