When many people think of animals, they only think of mammals, yet Class Mammalia is only one class in Subphylum Vertebrata, which is only one subphylum within Phylum Chordata.
Mammals are only a minuscule piece of the picture.
Animals live practically everywhere on this Earth. Insects, alone, inhabit nearly all possible environments on Earth with exception of deep in the ocean, yet their close relatives, the crustaceans have representatives that live there. Many other animals in many phyla live in the ocean and in just about every terrestrial habitat. From this point, if the young resemble the adults, it is said that the embryo grows into young, which grow into adults. Caterpillars and tadpoles are larvae , which have different food, habitat, and appearance than the corresponding adults.