Question

Microlecithal eggs are found in

• A. Reptilia and Aves
• B. Amphibia, Aves and Reptilia
• C. Reptilia, Aves and Chiroptera
• D. Eutheria

Answer 1

Answer: (D)

Eutheria

Eutheria includes the placental mammals. Placental mammals are characterized by the development of a placenta. The egg of these animals has very little (microlecithal eggs) or no yolk. The egg of reptiles and birds is rich in the yolk. The placenta in eutherians forms from both embryonic membranes and the maternal uterine wall. The blood vessels of the embryo come very close to the blood vessels of the mother, so materials can be exchanged by diffusion. The placenta allows the young to remain within the mother's body until embryonic development is complete.

So, the correct answer is option D.