Mammals and their characteristics biology lesson for kids: 1st, 2nd, 3rd, 4th, 5th, 6th and 7th grades biology lesson.
Mammals are warm-blooded vertebrates (meaning they have backbones), well developed brains, lungs, and hair. They also feed their babies milk from their bodies until they get bigger, and so can eat the same kinds of foods their parents eat. Mammals include a lot of the animals that you know and see around you: dogs, cows, dolphins, and even humans are all mammals. There are three main types of mammals, and they’re grouped based on how take care of their babies: monotremes, marsupials, and placentals.
Did you know that some mammals lay eggs? It’s true. Monotremes are mammals that demonstrate how closely related mammals are reptiles, evolutionarily speaking; after all, reptiles also lay eggs. Just like reptiles, monotremes have a single hole that they lay eggs out of and get rid of feces through. Monotreme release milk directly onto their fur, which their babies then lap up. It’s not mothers alone that do this, though; males produce milk for their babies, too! The platypuses and echidnas (a spiny mammal) are two monotremes.
The next type of mammals are marsupials. They don’t lay eggs, but their babies are very small and fragile. So, what the mother marsupials do is keep their babies in pouches, feeding them milk until they get big and strong. Unlike monotremes, mother marsupials have teats, nipples that the babies latch on to, sucking up the milk they need to grow. When the babies are big enough, they leave the pouch, but they still reach inside every now and then for some milk until they don’t need milk anymore. Kangaroos, wombats, and opossums are all marsupials.
The last group of mammals are called placentals. They are called that because the fetus (baby growing inside the womb) develops a mass called a placenta as it grows inside their mother’s womb. The placenta lines the wall of the womb and allows the fetus to get lots of nutrients for a long time inside the womb, and so it can grow bigger and stronger than a marsupial can before it needs to be born. Placentals have teats, too, and when their babies are born, the mothers allow their babies to suck on the tears, feeding them milk. Placentals include humans, cats, dogs, elephants, bats, rodents, and even cetaceans.
Speaking of cetaceans, there is a whole group of mammals that spend all their lives under water. They may look like fish, but these animals, which include whales and dolphins, are mammals! They have lungs rather than gills, and have hair, even though their hairs are so small you can’t see them with the naked eye. Cetaceans are very special mammals, just like bats, the only mammals that can fly!
Mammals are certainly a fascinating and diverse group of animals.