Question

Mammals are divided into three groups based on how and where their young develop before birth. Name the three groups and specify which of the three groups has the greatest number of living species.

A) Monotremes, marsupials, placentals
B) Prototherians, metatherians, eutherians
C) Oviparous, viviparous, ovoviviparous
D) Altricial, precocial, semi-precocial

Answer 1

Mammals are divided into monotremes, marsupials, and placental mammals (eutherians), with eutherians or placental mammals being the largest and most widespread group.

Step-by-step explanation:

Mammals are divided into three groups based on their reproductive strategies:

• Monotremes
• Marsupials
• Placental mammals (Eutherians)

Monotremes, like the platypus and echidnas, lay eggs and are the most primitive group. Marsupials, such as kangaroos and koalas, give birth to undeveloped young that complete their growth in a pouch. The largest group, by far, is the placental mammals, which includes species like humans, whales, and elephants. These mammals carry their developing young in the uterus, nourished through a complex placenta.

There are about 4,000 species of placental mammals, making eutherians the group with the greatest number of living species. They have been incredibly successful and are found worldwide, with diverse adaptations for almost every environment.