ANATOMY

Detailed explanation-1: -The cleavage remains limited in eggs of Birds, Reptiles and egg-laying mammals, to the disc-shaped area of cytoplasm, the blastodisc. The animal pole yolk is not divided. Such incomplete cleavage is known as discoidal cleavage.

Detailed explanation-2: -Cleavage involves incomplete or partial division is called as ‘Meroblastic’ in which amount of yolk is divided incompletely. So the correct option is ‘Meroblastic.

Detailed explanation-3: -Medical Definition discoidal cleavage. noun. : meroblastic cleavage in which a disk of cells is produced at the animal pole of the zygote (as in bird eggs)

Detailed explanation-4: -(a) Discoidal cleavage-Since the macrolecithal eggs contain plenty of yolk, the cytoplasm is restricted to the narrow region in the animal pole. Hence cleavage furrows can be formed only in Page 3 3 the disc-like animal pole region. Such a cleavage is called discoidal meroblastic cleavage. Eg: birds and reptiles.

Detailed explanation-5: -Monotremes, reptiles, birds, and fish with telolecithal egg cells (yolk located at one end) often exhibit discoidal cleavage. The cleavage furrows do not penetrate the yolk in discoidal cleavage. On top of the yolk, the embryo develops a disc-shaped group of cells known as a blastodisc.