Question

Eggs of placental mammals are:
A. Homolecithal
B. Acleithral
C. Microlecithal
D. Mesolecithal

Answer 1

Hint:-One of the three extant sectors of the class of animals Mammalia is called as
Placentalia. The other two are Monotremata and Marsupialia. The other mammals in that the fetus
the origins of the placentals, thus, we can say that they are partly distinguished from them. They are
carried in the uterus of its mother to a comparatively in the late stage of development.

Complete answer:-
The egg which has a negligible amount of yolk or no yolk is called Acleithral egg. Normally, the yolk is the one that provides the necessary nutrition for the development of the embryo. Thus, it is an important part of the egg in organisms that are oviparous. On the other hand, the developing embryo normally remains connected to the maternal parent of the unborn child. Thus, the eggs of placental mammals are Acleithral.
The homolecithal eggs are also called isolecithal eggs. In such types of eggs, there is the presence
of a little amount of yolk which is made to distribute uniformly among all the ooplasm. We can say
that such a condition is observed in the only animals whose egg contains very little amount of yolk.
The microlecithal eggs can be described as simple eggs with a little amount of yolk. The isolecithal
eggs are the medium-sized eggs with some yolk. Also, the acrolectal eggs are the large eggs with a
largely concentrated yolk.
Thus, we can say that the isolecithal eggs have comparatively more yolk than the Microlecithal eggs.
However, the yolk is strenuous in only one part of the egg (which is called as the vegetal pole), with
the cell nucleus and most of the cytoplasm in the other (which is called the animal pole).
Thus, the answer is Acleithral.

Note:- We can say that the egg of human beings can obtain nutrition from the mother by the means of the placenta. So, in human beings, the egg has a negligible amount of yolk and is Acleithral. However, we can say that the cell cleavage of mesorectal eggs is irregular and chiefly focused on the cytoplasm rich animal pole. Some of the organisms which have homolecithal eggs or isolecithal eggs are echinoderms, Amphioxus, and mammals.