Question

Eggs of reptiles and birds are
A. Mesolecithal
B. Teleolecithal
C. Polylecithal
D. Alecithal

Answer 1

The position of the yolk and the amount present in the eggs determines the types of eggs in organisms. Inreptiles and birds, the yolk is present in a large amount.

Complete answer:
The type of eggs in which the amount of yolk is less and are small in size are called microlecithal, which is derived from the word micro (i.e., small) and lecithal (i.e., yolk). The eggs that have a large amount of yolk are called macrolecithal and the ones which have a large amount of yolk concentrated at one pole are called telolecithal eggs. The eggs without any yolk are called alecithal and polylecithal eggs have a large amount of yolk. These eggs are mainly present in reptiles and birds. The yolk provides the source of nutrients and energy for fetal development. The yolk forms the embryo and provides nourishment to it. The yolk in the mesolecithal eggs is concentrated at one pole of the egg. They have a longer fetal development phase than microlecithal eggs. Macrolecithal eggs have a large yolk size and because enough nutrients are available the egg goes through the complete fetal development stage.
Hence, the correct answer is option C.

Additional information: Based on the distribution of yolk granules in the egg’s cytoplasm, the eggs are classified into homolecithal/isolecithal, where the yolk is distributed evenly in the cytoplasm. In centrolecithal, the yolk is mainly present in the centre or interior part surrounded with cytoplasm, and in telolecithal, the yolk is in large amounts and concentrated at one pole of the egg.

Note: Microlecithal are mostly found in flatworms, roundworms, annelids, echinoderms, arthropods, and mammals. Placental mammals like humans have so little yolk that they are referred to as alecithal. Whereas, mesolecithal eggs are found in amphibians and telolecithal eggs are found in fishes.