Answer
Mammals.
give birth to their young and feed them with milk
have hair on at least part of their body
have four legs with toes ending in claws, nails, or hooves (whales and dolphins are exceptions)
breathe with lungs
are warm-blooded
Birds.
lay eggs with a hard shell
are covered with feathers
have a beak
have two legs
have two wings and most can fly (ostriches and penguins are exceptions)
have hollow bones
are warm-blooded
Reptiles.
lay eggs with leathery shells or give birth to fully-formed young
breathe with lungs
are covered with scales
have no legs or four legs with clawed toes
are cold-blooded
Amphibians.
lay eggs, usually in a jelly-like mass in water
breathe with lungs, gills, and/or their skin
have smooth skin without coverings
have four legs without claws or nails on toes
are cold-blooded
Insects.
have three body parts: head, thorax, and abdomen
have a single pair of antennae on the head
have three pairs of legs originating from the thorax
often have wings and can fly
Fish.
lay eggs without shells in water
breathe with gills
are covered with scales or smooth leathery skin
have fins but no legs or toes
are cold-blooded
