ABSTRACT
Vertebrates (which belong to the subphylum Vertebrata and phylum Chordata) have been in existence from late Cambrian about 500 million years ago. They represent a small group that comprises about 2% and over 40 thousand species of the widely distributed animals on Earth. One is quite familiar with vertebrates as they are relatively agile and large in size and human beings are vertebrates and interact with quite a number of them in their daily lives. The generally larger size of vertebrates in comparison to invertebrates is as a result of evolution of a versatile support system, mainly the skeletal system.
