Fertilization and Early Embryonic Development

Free Response

What do you think would happen if multiple sperm fused with one egg?


Multiple sperm can fuse with the egg, resulting in polyspermy. The resulting embryo is not genetically viable and dies within a few days.

Why do mammalian eggs have a small concentration of yolk, while bird and reptile eggs have a large concentration of yolk?


Mammalian eggs do not need a lot of yolk because the developing fetus obtains nutrients from the mother. Other species, in which the fetus develops outside of the mother’s body, such as occurs with birds, require a lot of yolk in the egg to nourish the embryo during development.