Division and Classification Essay (Reptiles)

Division and Classification Essay Animals that breath air and have scales on the exterior of their body are referred to as reptiles. Reptiles have been dated back to have been on the earth for the past 315 million years, though not all species are extant in modern times. All reptiles are ectotherm, which means they are “cold-blooded” animals (whereas most mammals are warm-blooded). All reptiles are also tetrapods, which mean they have four limbs (or they have descended from four-limbed ancestors). In general most reptiles are oviparous (egg-laying), with the exception of some viper and constrictor snakes that give live birth. In regards to size, reptiles can be anywhere from a tiny 0.6 inch gecko all the way up to a 20 foot crocodile weighing in at 2,200 pounds. With the exception of Antarctica reptiles inhabit every area of the earth. Reptiles are recognized as being classified into four separate domains (categories) which are, Crocodilia, Sphenodontia, Squamata, and Testudines (Wikipedia, Reptiles). The domain Crocodilia contains the family’s alligator, caimen, crocodile, and gharial. There are twenty-three species contained in this domain, and they are the closest living relatives to birds. This order had been in existence for the past 84 million years since the dawn of the Cretaceous period. The crocodilian species ranges in size from a four to five- foot Cuvier’s Dwarf Caimen, all the way up to the twenty-foot Saltwater Crocodile (which is actually the largest out of all extant reptiles). Species within this domain have an average life span of seventy to one hundred years. Crocodilians are the only domain of reptiles that have a four-chamber heart, the usual in all other reptiles being either a three of five chambered hear. It is common for only warm-blooded animals (such as mammals and birds) to have a four chambered heart. But since Crocodilians ancestors were warm blooded it is believed they kept this extra valve to help shunt oxygen depleted blood to