There are about 30 million species of animals on our planet. Animals are classified on the basis of their similarities and differences. Animals are divided into six basic groups. These six groups help us in understanding the basic classification of animals. But the most basic criteria by which animals are classified are that whether they posses backbone or not. There are two main groups of animals.

Vertebrates
The animals having skeletons inside their bodies are called vertebrates. Homo Sapiens (read we) are also included in this group of classification. History of vertebrates on earth is very old. The very first type of vertebrates lack jaws. Examples are hagfish and lampreys. Vertebrates with jaws appear in animal’s generation around 100 million years before. Human beings have a long biological. Social and cultural bound with vertebrates. Man kept using horse as a mean of transportation. Beside that some other vertebrates like birds, casts and dogs are domesticated by human being. Pigeons were also used in past as a way of communication. The vertebrates possess the resemblance with the chordates but some of their characteristics make them unique. In vertebrates there is present a set of cells called neural crest cells. Basically these cells are responsible for developing characteristics which make vertebrates different from others.

Some examples of vertebrates are humans, dogs, birds, cats, crocodile etc.

Invertebrates
Animals that lack internal skeletal system is called Invertebrates.98% of the animals on earth are invertebrates. Invertebrates have the quality to survive in verity of environment. They can survive at hot and unbearable temperature. And they can also be found at unbearable temperature of polar region. Invertebrates are found in different shapes and colors. The production rate of invertebrate is fast as compare to vertebrates. That’s why Invertebrates are used in science as model organism. Invertebrates possess one cluster of hog genes. And this characteristic of invertebrates differentiates them from vertebrates. Invertebrates are found in different shapes and color. For good understating about invertebrates scientist have divide them in eight groups i-e Arthropods, Sponges, Cnidarians, Segmented worms, Flat worms, Round worms, Mollusks, Echinoderms. Some invertebrates possess hard shells these shell are basically for their protection.

Examples of Invertebrates include sponges, jellyfish, sea anemones, tapeworms, liver flukes, snails, oysters, octopuses, earthworms, leeches, crabs, spiders, ticks, scorpions, centipedes, lobsters, prawns, flies, lice, cicadas, beetles, weevils, moths, starfish and sea urchins.