Animals can be divided broadly into vertebrates and invertebrates.
Vertebrates have a backbone or spine (vertebral column). They include:
1. Fish: a limbless cold - blooded vertebrate animal with gills and fins and living wholly in water.
2. Amphibians: a cold - blooded vertebrate animal. Comprises the frogs, toads, newts, and salamanders.
3. Reptiles: a cold - blooded vertebrate of a class that includes snakes, lizards, crocodiles, turtles, and tortoises. They are distinguished by having a dry scaly skin, and typically laying soft - shelled eggs on land.
4. Birds: a warm - blooded egg - laying vertebrate distinguished by the possession of feathers, wings, and a beak and (typically) by being able to fly.
5. Mammals: a warm - blooded vertebrate animal of a class that is distinguished by the possession of hair or fur, the secretion of milk by females for the nourishment of the young, and (typically) the birth of live young.
The remaining animals are the invertebrates, which lack a backbone. These include:
1. Molluscs (clams, oysters, octopuses, squid, snails)
2. Arthropods (millipedes, centipedes, insects, spiders, scorpions, crabs, lobsters, shrimp)
3. Annelids (earthworms, leeches)
4. Cnidarians (jellyfish, sea anemones, corals)
5. Sponges