Final answer:
Humans and most other animals that give birth to live young are classified as mammals. Mammals are predominantly viviparous, with marsupials and placental mammals giving birth to young that develop either in a pouch or the uterus.
Step-by-step explanation:
Animals such as humans that usually give birth to live young are called mammals. While there are a few mammals that lay eggs, called monotremes, such as the platypus and the echidna, the vast majority of mammals are viviparous, meaning they give birth to live offspring. Within mammals, there are marsupials, like kangaroos and koalas, which give birth to underdeveloped young that complete their development in a pouch, and placental mammals, like humans, where the embryo develops in the uterus and receives nutrients through the placenta.
Therian mammals, which encompass both marsupials and placental mammals, all have viviparous reproduction, giving birth to a more developed embryo or infant rather than laying eggs. This process involves the female's reproductive system, which includes a uterus and vagina.