1.

Pattern of cleavage in egg of Frog isA. MeroblasticB. Holoblastic unequalC. Holoblastic equalD. All of the above

Answer» Correct Answer - B
(B) Types of Cleavage: Type of cleavage in an egg is determined by amount and distribution of yolk.
1. Holoblastic cleavage: Cleavage of zygote is complete and divide 2 blastomores completely. This is of 2 types:
(i) Equal holoblastic cleavage:
It forms equal blastomeres. e.g.: Human, starfish
Alecithal and microlecithal egg.
(ii) Unequal holoblastic cleavage: It forms 2 unequal blastomeres. e.g.: Frog, dog fis: Mesolecithal egg.
(2) Meroblastic cleavage: In this cleavage is incomplete or partial or parietal and the division is confined to the animal pole. Yolk is not divided. It is of two types: ltbtgt (i) Discoidal cleavage: The cleavage confined only to the disc area at the animal pole. e.g.: Reptiles, birds (chick and pigeon) and egg laying mammals : Megalecithal egg.
(ii) Superficial cleavage: The cleavage is restricted to the superficial region of egg. e.g.: Insects (Arthropods), Centrolecithal eggs.


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