http://msnucleus.org/membership/html/k-6/lc/organ/2/lco2_2a.html
The vertebrates refer to the phylum called CHORDATA. Members of this phylum are our common everyday animals. All mammals, birds, amphibians, reptiles, and fish belong to this group. There are over 45,000 species throughout the world. Vertebrates have a backbone, a nervous system, and a gill slit during some stage of their life cycle. In land-dwelling vertebrates, these slits are present only in the embryo.
Mammals have distinct characteristics including: controlled body temperature, highly developed jaws, a coat or hairy skin covering, highly developed internal organs, and mammalian glands. Most important is their mode of reproduction and the way in which the young are fed on the mother's milk.
Birds are warm blooded and have a constant body temperature (with some exceptions). Birds have succeeded in conquering the air by having a very light skeleton. The beak and eyes are highly developed. They have feathers and produce eggs.
Reptiles are mainly terrestrial, but there are many living partly in the aquatic environment. The body is covered with scales or patches of horny, sometimes bony skin. Limbs are usually short or absent, feet show many variations in form. Most reptiles are oviparous, meaning that they produce external eggs. Representatives of reptiles include lizards and snakes.
Amphibians are aquatic are four limbed. The most common characteristic is an exposed, water permeable skin, rich in glands which secrete mucus, which is sometimes poisonous. Amphibians lay small round eggs protected by a gelatinous mass. Some species go through a larval stage that metamorphoses into a juvenile, for example, a tadpole changes into a frog.
There are two major types of fish, one group called the bony fishes and the other cartilaginous fishes. All fishes live in water and have external fertilization (with some exceptions). Cartilaginous fish include sharks, rays, and lampreys. Bony include most of your present day fishes like tuna, salmon, and goldfishes.
