Broadly, Scientists have grouped animals into two classes :

• Vertebrates (animals with backbones)

• Invertebratres (animals without backbones)

Every animal of the world belongs to one of them.

Vertebrates

The five most well known classes of vertebrates are mammals, birds, fish, reptiles, amphibians. They are all part of the phylum chordate.

Mammals

People are mammals. So are dogs, cats, horses, duckbill platypuses, kangaroos, dolphins and whales. If an animal drinks milk when it is a baby and has hair on its body, it belongs to the mammal class. Dog , Coyote , Polar Bear , Elephant , Giraffe , Camel , Dolphin , Vampire Bats , Horse , Fox

Birds

Birds are animals that have feathers and that are born out of hard-shelled eggs. Some people think that what makes an animal a bird is its wings. Bats have wings. Flies have wings. Bats and flies are not birds. The truth is that it is the feathers who makes an animal a bird and not wings. All birds have feathers and birds are the only animals that do. The feathers on a bird's wings and tail overlap. Because they overlap, the feathers catch and hold the air. This helps the bird to fly, steer itself and land.Crow , Peafowl , Birds , Duck , Owl , Pigeon , Flamingo , Woodpecker , Ostrich , Sparrow , Chicken

Fish

Fish are vertebrates that live in water and have gills, scales and fins on their body. There are a lot of different fish and many of them look very odd indeed. There are blind fish, fish with noses like elphants, fish that shoot down passing bugs with a stream of water and even fish that crawl onto land and hop about! Fishes

Reptiles

Reptiles are a class of animal with scaly skin. They are cold blooded and are born on land. Snakes, lizards, crocodiles, alligators and turtles all belong to the reptile class. Reptiles , Crocodile , Chameleon , Tortoise , Turtle

Amphibians

Amphibians are born in the water. When they are born, they breath with gills like a fish. But when they grow up, they develop lungs and can live on land. Frog

Invertebrates

There are also a lot of animals without backbones. These are called invertebrates and are part of the phylum arthropoda (arthropods). Two of the most commonly known classes in this phylum are arachnids (spiders) and insects.

Arthropods

Arthropods is a huge phylum of animals -- it includes eleven animal classes: Merostomata, Pycnogonida, Arachnida, Remipedia, Cephalocarida, Branchiopoda, Maxillopoda, Malacostraca, Chilopoda, Diplopoda, and Insecta. 

Any animals that have more than four, jointed legs are arthropods. Insects, spiders and crustaceans all belong to this class of animals. Insects , Spider , Grasshoppers , Praying Mantis , Dragonfly , Butterfly , Bees

Some more classes of Animals

Cannibals

A cannibal is an animal that feeds on others of its own species. This is not an animal unnatural characteristics: around 140 different species show cannibalistic tendencies under various conditions. Cannibalism is most common among lower vertebrates and invertebrates often due to a predatory animal mistaking one of its own kind for prey. But it also occurs among birds and mammals, especially when food is scarce.

In sexual cannibalism as recorded for example for the female red-back spider, black widow spider, praying mantis, and scorpion the female eats the male after mating (though the frequency of this is often overstated).

The more common form of cannibalism is size structured cannibalism, in which large individuals consume smaller ones. Such size structured cannibalism has commonly been observed in the wild for a variety of taxa, including octopus, bats, toads, fish, monitor lizards, red-backed salamanders and several stream salamanders, crocodiles, spiders, crustaceans, birds (crows, barred owls), mammals, and a vast number of insects, such as dragonflies, diving beetles, back swimmers, water striders, flour beetles, caddisflies and many more.

Carnivores

A carnivore meaning 'meat eater' is an animal with a diet consisting mainly of meat, whether it comes from animals living or dead (scavenging). Some animals are considered carnivores even if their diets contain very little meat but involve preying on other animals Animals that subsist on a diet consisting only of meat are referred to as obligate carnivores. Plants that capture and digest insects are called carnivorous plants. Similarly fungi that capture microscopic animals are often called carnivorous fungi.

Cat , Tiger , Cheetah , Lion , Brown Bears , Penguin , Sharks , Snake

Herbivores

A herbivore is any organism that normally consumes only autotrophs such as plants, algae and photosynthesizing bacteria.

Gorilla , Orangutan , Monkey , Panda , Hippopotamus , Rhinocerose , Kangaroo

Omnivores

Omnivores are the animals who eat and digest both animals and plants. They are primary and high level consumers. Humans are omnivorous as they take vegetables and meat. It include fish, humans, domestic dog, pig, bear, rodents, Opossums, Raccoons, Foxes, Rails, Rhea, Most gulls, Chickens, Crows, Domestic pigeons. Squirrel , Chimpanzee , Pig

Detritivores

Detritivores (also known as saprophages, detrivores or detritus feeders) are organisms that recycle detritus (decomposing organic material), returning it into the food chain. Earthworms are a well-known example of detritus feeders, eating rotting plant leaves and other debris. Groups of detritivorous animals include: millipedes, woodlice, dung beetles, dung flies and burying beetles.

Scavengers

The word scavenger, in zoology, refers to animals that consume already dead organic life-forms. Scavengers are useful to the ecosystem by feeding on and therefore breaking down dead animal and plant remains. The remains that are left behind by the scavengers are then used even further by decomposers. Well known scavengers include vultures, burying beetles, blowflies, and raccoons. Many large carnivores that hunt regularly--such as hyenas and lions--will scavenge if given the chance.