Animals have distinctive characteristics that allow you to
classify them into certain groups . For example, Mammals have four
character traits that makes classification easier.
breathe air with lungs
give birth to live young
feed young with mother's milk
There are many kinds of mammals. Sometimes they are placed into
groups based on traits they have in common.
Some of the traits that are used to classify mammals into groups are: the presence of wings, trunks, and pouches.
The three main subclasses of mammals are:
Placental Mammals: The young of Placental Mammals develop inside the mother's body and are nourished by a saclike organ called a placenta. The young are well developed at birth. Most mammals , including humans are placental mammals.
Marsupials: These mammals are often referred to as "pouched mammals." Young marsupials do not develop in the mother's body. They are born tiny, hairless and blind. Soon after birth, the young move into the mother's pouch, where they receive nourishment and complete their development.
Monotremes: The most primitive in the mammal group. These
mammals lay eggs instead of giving live birth. Like other mammals
they have hair and produce milk for their young. There are only 3
species of monotremes - the Duckbilled Platypus, and 2 species of Echidna
otherwise known as "spiny anteater."
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