Question

Isolecithal eggs are found in
a. Birds
b. Frogs
c. Insects
d. Mammals

Answer 1

Distribution of the yolk in the cytoplasm to ovum of mammals, amidases, lepisosteidae, petromyzontidae and other vertebrates refer as a term isolecithal. Some of the yolk settles to the bottom of the egg during cellular development and produces uneven distribution of yolky hemisphere. Two hemisphere cells present in the isolecithal.

Complete answer:
The very less amount of yolk present in the microlecithal egg that is present in the mammals. This type of cell is present in the egg of marsupials, eutherian and amphioxus in mammals. At the point where the animal hatches the egg are the organic vessels that contain zygotes in which the embryo develops until it can survive its own.

Mammals, chimpanzees, monkey and cow fertilization and embryo development occurred inside the individual even human body also part of that and known as the type of viviparous. Embryo development inside the parent body eventually leads to birth among the animals called viviparity. And the process of oviparity is entirely opposite to the viviparity. Hemotrophic, histotrophic, ovoviviparity, placental and viviparity are the five modes that help to result in live birth.

Hence, the correct answer is option (D).

Note: Rotational holoblastic, radial holoblastic, bilateral holoblastic and spiral holoblastic cleavage occurred in the absence of a large concentration of the yolk in the isolecithal cells. During the process of cytokinesis holoblastic cleavage planes pass through the isolecithal zygotes. Because of the small amount of yolk present in the isolecithal cells need immediate implementation on to the wall of uterine to receive nutrients.