Please distinguish between monotremes, marsupials, and placental mammals.

A monotreme is
a mammal that lays eggs. This means that they do not give birth to live young. They also keep
the eggs inside for a longer period of time to provide nutrients to the egg. An example of a
monotreme is a platypus or echidna.

A marsupial is a mammal that has a pouch
in which to carry their young. Marsupials generally give birth earlier that placental mammals.
They have very strong limbs because they have to climb to the mothers nipples to feed. An
example of a marsupial is the koala and kangaroo.

A placental mammal is a
mammal that is nourished in the mother's uterus and born developed. This is a very diverse group
and consists of whales, cats, dogs, and humans, just to name a few.