Question

Megalecithal eggs are found in
A. Reptiles and birds
B. Tunicates, amphibians and monotremes
C. Annelida, echinoderm and coelenterates
D. Sponges, reptiles and monotremes.

Answer 1

Hint: As the name suggests ‘mega' which means ‘large' the egg which contains a large amount of yolk is called Megalecithalegg. It is also called as macrolecithal, polylecithal. This type of yolk is mostly observed in egg laying mammals. The yolk in the egg plays a crucial role in providing the nutrition and helps in the gas exchange hence the mammals with Megalecithal egg get huge and complete nutrition and support for the development from the large mass of yolk inside the egg.

Complete answer:
Reptiles and birds are egg laying mammals with large amounts of yolk then other mammals. The egg of the reptiles and birds has very less cytoplasm as the egg is occupied by a large amount of yolk while the nucleus is seen inside the egg to undergo metabolism for the development of the egg. This type of egg is called as Megalecithal egg
Tunicates contains very small amount of yolk inside the egg with well distributed cytoplasm and this types is known as microlecithal eggs, amphibians contains moderate amount of yolk hence we called as mesolecithal egg and also we call monotremes as in the term of Megalecithal eggs.
So, this entire option B only has one Megalecithal egg organism hence it is not correct.
Annelids, echinoderm, coelenterates. The eggs of these organisms are very small without yolk Hence, option c is wrong.
Sponges reproduce through budding and gemmules which mean there is no egg. Reptiles and monotremes are egg laying mammals with Megalecithal eggs
So, option D is not considered as it contains sponges.
So, the correct answer is “Option A”.

Note:
On the basis of the distribution of the amount of yolk inside the egg there are four types of eggs. Alecithal which means the yolk is absent, Megalecithal types are with very less yolk. The mesolecithal egg contains moderate yolk whereas the egg with large amount of yolk is called Megalecithal