Question

In insect eggs, cleavage is?
A. Equal holoblastic
B. Unequal holoblastic
C. Meroblastic superficial
D. Meroblastic discoidal

Answer 1

Hint:In insects the yolk is concentrated within the center with the nucleus during a net-like structure thus they need centrolecithal eggs. In insects, the cleavage is partial or incomplete. The cytokinesis doesn't happen and thus leads to a polynuclear sort of ovum.

Complete answer:This is the rapid cellular division that results in a multicellular embryo. To 'cleave' means to slice or split something, so, it is sensible that cleavage is the splitting of cells. A meroblastic cleavage wherein mitosis occurs without cytokinesis, leading to many nuclei, which migrate to the periphery of a centrolecithal egg. In this sort of cleavage wherein, a layer of cells is produced a few central masses of yolk (as in many arthropod eggs) is understood as superficial. During this type, the cleavage furrows are restricted to the active cytoplasm found either within the animal pole (macrolecithal egg) or superficially surrounding the egg (centrolecithal egg).
Meroblastic cleavage could also be of two types:
(a) Discoidal cleavage — Since the macrolecithal eggs contain many yolks, the cytoplasm is restricted to the narrow region within the animal pole. Hence, cleavage furrows are often formed only in 3 the disc-like animal pole region. Such cleavage is called discoidal meroblastic cleavage. E.g., birds and reptiles. (b) Superficial cleavage — In centrolecithal eggs, the cleavage is restricted to the peripheral cytoplasm of the egg. E.g.: insects.
So, the proper answer could also be C. Meroblastic superficial.

Note: It is important to note that apparently there are several cleavage patterns. However, all cleavages follow a standard procedure. The cleavages are governed by certain basic principles or laws.