Question

In which of the following animal cleavages, divisions are restricted to a small part of the cytoplasm and nucleus in the animal pole of egg?
A. Cockroach
B. Frog
C. Chick
D. Rabbit

Answer 1

Animal cleavage is defined as the process during which the animal cells undergo rapid cell division leading to the formation of a multicellular embryo.

Complete Answer:
- Animal cleavage is of different types which are- holoblastic, meroblastic, determinate and indeterminate. In determinate cleavage the fate of the cells is determined during the early stages of embryo development.
- In indeterminate cleavage the fate of the cell is not decided and each cell is capable of giving rise to the entire organism. Meroblastic cleave is the partial division of the fertilized cell whereas holoblastic cleave is the complete division of the fertilized cell.
- Cockroaches are known to undergo determinate cleavage where it develops into a nymph and finally an adult cockroach. The cleavage in frogs is holoblastic similar to echinoderms, cleavage is initiated at the animal pole where the nucleus as well as most of the cytoplasm is located.
- Cleavage in chicks are mostly meroblastic and also known as discoidal as it is restricted to the blastodisc, which is a small circular structure present on the yolk of the egg which restricts the division to a small part of the nucleus and cytoplasm of the egg. The cleavage in rabbits is holoblastic and also nearly symmetrical.

So the correct option is C) Chick.

Note: Animal cleavage is a very important step not only in the development of an embryo but also helps to partition the embryo into various developmental regions.