why is the relative size of the yolk sac in a mammal egg much smaller than that found in an amniotic egg?
Why is the relative size of the yolk sac in a mammal egg much smaller than that found in an amniotic egg?
Cevap: The relative size of the yolk sac in a mammal egg is smaller compared to that found in an amniotic egg due to evolutionary adaptations and differences in reproductive strategies.
Mammals are viviparous, which means they give birth to live young. In viviparous animals, the embryo develops within the mother’s body and receives nourishment directly from the mother through a placenta. The placenta provides nutrients and oxygen to the developing embryo, making the yolk sac in mammal eggs less essential for nourishment.
On the other hand, amniotic eggs are found in reptiles, birds, and some egg-laying mammals. These animals are oviparous, meaning they lay eggs externally. Amniotic eggs have a larger yolk sac because they need to provide enough nutrients and energy for the developing embryo during the incubation period. The yolk sac contains proteins, fats, and other nutrients that are necessary for the growth and development of the embryo.
The difference in the relative size of the yolk sac can also be attributed to the different reproductive strategies of mammals and egg-laying animals. Mammals invest more resources in nurturing their young internally, while egg-laying animals rely on providing ample nutrients in the egg itself. This difference in reproductive strategies results in the smaller yolk sac size in mammal eggs compared to amniotic eggs.
Overall, the relative size of the yolk sac in a mammal egg is smaller because mammals have evolved alternative mechanisms, such as the placenta, to provide nutrients to the developing embryo.