Video Transcript
Name the subclass of Mammalia that is being described. These are mammals that often give birth to immature young that must be kept in their mothers’ pouches for weeks after birth.
A wide range of animals belong to class Mammalia, ranging from tiny mice to humans, kangaroos, and even huge whales. To distinguish between these animals, class Mammalia can be further split into subclasses based on how they give birth and the way that their embryos or young develop. To help answer this question, let’s take a look at some of these subclasses in more detail.
The subclass Eutheria is the largest of these subclasses and includes humans. Mammals belonging to this subclass allow their young to develop in the uterus and provide nutrients for the young through a placenta, until it is developed enough to be born.
Metatheria mammals, on the other hand, only allow their young to develop in the uterus for a short amount of time. Mammals in this subclass give birth to immature young that then complete their development in a specialized pouch on the mother, for example, like kangaroos. So, they give birth to live young rather than laying eggs. But these young develop outside of the mother’s uterus.
The final group is the prototherians, which, unlike other mammals, lay eggs and incubate them until they are ready to hatch. Prototherians are not very common, but you might have heard of the duck-billed platypus, which is an example of an organism belonging to this subclass.
So, if we look back at the question, the subclass of mammals that often give birth to immature young that must be kept in their mothers’ pouches for weeks after birth is the subclass Metatheria.
