Water is where they most often lay their eggs. Moist environments are preferred by most amphibians. Reptiles can be lizards, snakes, crocodilians, turtles or tuataras. Reptile eggs and skins are good at holding water inside. Birds can be flightless like the ostrich or the penguin, or flight-full, like the eagle, but thy all have feathers which help them to keep a steady body temperature.
Birds lay eggs and most bird parents look after their young.
Mammals can be marsupials like the opossum, monotremes, like the platypus, or placentals, like the chimpanzee. Fur is their trademark and it helps mammals to keep their body temperature steady. Mammals are known for looking after their young and for providing them with milk from special glands.