(I) Australia is home to marsupials like kangaroos and koalas. (II) The ability to generate body heat is what enables mammals to survive in so many different climates. (III) These are animals that give birth to underdeveloped young who crawl into the mother's pouch. (IV) There they develop further until they can live in the outside world. (V) The way of rearing the babies is unusual but they are fed in the usual way, on mother's milk.