Question

Reptile and bird eggs are
(a) Macrolecithal
(b) Oligolecithal
(c) Mesolecithal
(d) Alecithal

Answer 1

Reptiles and birds are amniotic animals. Process of fertilization in all amniotes takes place inside the mother’s womb but in case of reptiles and bird formation of embryos take place outside the body that's why their eggs have a covering of shell. Inside the egg developing embryo gets nutrition from the yolk present inside the shell.

Complete answer:
In reptiles and birds, an egg's maximum amount of yolk is present to provide protection to the developing embryo, due to the presence of the high amount of yolk these eggs are called as macrolecithal or polylecithal. After laying the egg, the mother provides heat to the embryo which is also called incubation. Incubation helps in the development of an embryo. Macrolecithal eggs are also present in shark and bony fishes.

Additional Information: Oligolecithal eggs have a small amount of yolk. These eggs are present in the echinoderm, the echinoderm show external fertilization in water. Shedding of egg in water is also known as spawning, spawning takes place throughout the year, and in some cases, it takes 2 to 3 months. After fertilization larvae of echinoderm form, the size of larvae depends on the amount of yolk. In rare cases, eggs of echinoderm consist of a high amount of yolk and this egg after fertilization forms mature echinoderm without the formation of larvae.
Mesolecithal eggs have an intermediate amount of yolk concentrated on one side, it is present in Petromyzon and amphibians. Most species of amphibians show external fertilization in water and after fertilization larvae form which remains in water till maturation, after maturation it comes out of water.
Alecithal means the absence of yolk, human eggs are alecithal because, after fertilization, the formation of zygotes takes place. The human egg does not need yolk because the protection of the embryo and transmission of nutrients takes place inside the mother worm. Internal protection in the human female womb is provided by the amnion and chorion.
So, the correct answer is ‘Macrolecithal’.

Note: As reptiles and birds both consist of mesolecithal eggs but their eggs differ in shape and size, also birds have eggs with hard shells but reptiles have soft-shelled eggs except in crocodiles and turtles.