Viviparity in Animals
We do it. But so do aphids, and even some snakes!
So what IS viviparity? What do we have in common with tiny plant-sucking aphids?
As you know, the vast majority of mammals give birth to young that has developed inside the mother’s body, unlike birds and most reptiles and most insects, which lay eggs. However, there are several notable exceptions within these groups. You probably have heard of snakes that bear live young. And there IS a rare third category called ovo-viviparity, which is an odd combination of the two methods of producing young, basically where the young develop inside the parent but there is no placenta or umbilical cord or any other actual connection for nourishment and disposal of wastes.
What are the benefits of viviparity?
In a nutshell, the advantages of oviparity lie with the mother — less resources expended — and the benefits of viviparity lie mainly with the offspring, which get a more secure beginning in life in MOST cases. Of course, the benefits continue if the mother actually protects, and even feeds the young after it is born. Think of a baby sea turtle running for its life to make it to the water which is STILL a source of great danger. Compare to that a mother snake of one of the species that gives birth to live young, particularly if she guards them for a time. Still, it is typically the case that MORE offspring can be produced when deposited inside eggs, leaving the mother to go on with no further disadvantage on her part. She can hunt and hide and go about her life, and she does not have the extra bulk and calorie drain from carrying young inside her — even if she were to stick around and guard the eggs. Truly viviparous motherhood is a noble sacrifice — go thank your mother! 😀
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