Question

Biradial cleavage is found in
A. Sponge
B. Frog
C. Ctenophora
D. Amphioxus

Answer 1

Hint:- In the animal kingdom, various phylums are included consisting of primitive to modern animals of their respective phylums. The phylums from primitive to modern animals are- Protozoa, porifera, coelenterata, ctenophora, platyhelminthes, aschelminthes, annelida, arthropoda, mollusca, echinodermata, hemichordata and chordata. These phylums are classified on the basis of - level of body organisation, symmetry, germinal layers, body cavity, body plan, segmentation, notochord, circulatory system and embryonic development.

Complete answer:
The division of cells during embryonic developmental stages is called cleavage. Symmetry is defined as if one or more than one plane that passes through the axis of the centre of body, divides the body into two or more than two equal parts or identical right and left halves. There are three types of symmetry found according to which organisms can be classified. These are asymmetry, radial symmetry and bilateral symmetry.
When any plane that passes through the centre does not divide the body of animals into two equal halves, the symmetry is called as asymmetry. It can be seen in phylum Porifera (sponges). In sponges, during the developmental stages, the whole cell divides completely (holoblastic cleavage).
When any plane passing through the central axis of the body divides the animal into two identical halves, the symmetry is called radial symmetry. This symmetry is found in phylum coelenterata, ctenophora and adult echinodermata. In ctenophora, the cleavage seen is biradial cleavage.
During embryonic development, if the first three divisions in a cell are not at right angles to each other, the cleavage is termed as biradial cleavage. In animals such as frogs and amphioxus (chordates), the symmetry found is called bilateral symmetry in which only one plane divides the body into two identical right and left halves. Cleavage in frogs is holoblastic and in amphioxus, irregular cleavage is seen.
Thus the correct answer is option C.

Note:- Members of phylum Ctenophora are known for their beauty and delicate nature. In sunlight, their comb plates (locomotory structures) give the effect of a rainbow. They also show a phenomenon called bioluminescence (emits light). Their body is soft, transparent and jelly like. They are radially symmetrical with tissue grade of body organisation. During development, they develop only two germ layers thus called diploblastic organisms.