Animals / Wildlife - By Category

Amphibians
Amphibians are a group of vertebrates that includes salamanders, newts, caecilians, frogs and toads. There are between 5,000 and 6,000 species of amphibians alive today. The first amphibians arose about 370 million years ago during the Devonian Period. The articles listed below provide information about the characteristics, classification and evolution of amphibians.

Birds
Birds are a group of vertebrates that includes about 30 groups such as albatrosses, gamebirds, herons, hummingbirds, owls, parrots, penguins, perching birds, woodpeckers and many others. There are between 9,000 and 10,000 species of birds alive today. The first birds evolved from reptiles during the Mesazoic Era about 150 million years ago. The articles listed below provide information about the characteristics, classification and evolution of birds.

Fishes
Fishes are a diverse group of vertebrates and represent an informal collection of animals, not a true taxanomic class. For the purposes of this website, we recognize four groups of fishes including hagfish, lampreys, cartilaginous fishes and bony fishes. There are more than 24,000 species of fishes alive today. The articles listed below provide information about the characteristics, classification and evolution of fishes.

Invertebrates
Invertebrates are a diverse group of animals that includes over 30 phyla. Invertebrates do not have a backbone, nor a bony skeleton. This large group of animals includes sponges, cnidarians, flatworms, roundworms, segmented worms, molluscs, echinoderms, and arthropods. About 97 percent of all known species are invertebrates. The articles listed below provide information about the characteristics, classification and evolution of invertebrates.

Mammals
Mammals are a group of vertebrates that includes about 21 groups such as anteaters, bats, carnivores, cetaceans, elephants, marsupials, primates, rodents and many others. There are about 5,400 species of mammals alive today. Mammals first appeared about 200 million years ago during the Jurassic Period. The articles listed below provide information about the characteristics, classification and evolution of mammals.

Reptiles
Reptiles are a group of vertebrates that includes crocodilians, lizards, snakes and turtles. There are about 8,000 species of reptiles alive today. Early reptiles diverged from other amniotes between 320 and 310 million years ago during the late Carboniferous Period. The articles listed below provide information about the characteristics, classification and evolution of reptiles.

Zoology Basics
Zoology is the study of animals and involves research in many aspects of animal life such as behavior, diet, evolution, classification, and distribution.

Zoology Glossary
The science of zoology has a language of its own with thousands of terms that are rarely used by non-experts. This collection of definitions and word lists should help as you try to understand the vast language that has developed for the study of animals.