Classification of Vertebrates

Classification of Vertebrates

1. There are 5 types of vertebrates

   • Mammals
     • Mammals are warm-blooded (endothermic) vertebrates that differ in many ways from members of other vertebrate classes. Mammals have hair on their skin, three bones in the middle ear, a four-chambered heart, and a region of the brain called a neocortex that is involved in higher neurological functions such as spatial reasoning, conscious thought, and, in some species (ours), language. There are roughly 5,400 species of mammals including our species, Homo sapiens
   • Fish
     • Fishes constitute the non-tetrapod vertebrates, meaning that they do not have four legs or limbs, although they generally have two pairs of fins and several unpaired fins that allow them to move efficiently through water. They are almost all entirely aquatic, although there are a few species that can survive out of the water for short periods of time. There are approximately 28,000 fish species subdivided into five different classes.
   • Amphibians
     • Amphibians are cold-blooded (ectothermic) vertebrate tetrapods that generally respire air as adults but usually require an aquatic (freshwater) environment for reproduction. The term tetrapod, as mentioned earlier, refers to four-legged/limbed animals that generally have two pairs of limbs: one pair on the anterior, or front, end of the animal and one pair on the posterior, or tail, end of the animal. Other vertebrate tetrapods include reptiles, birds, and mammals. There are roughly 6,000 existing amphibian species.
   • Reptiles
     • Reptiles are also cold-blooded (ectothermic) vertebrate tetrapods, but they differ from amphibians in a number of important ways. Unlike amphibians, reptiles are amniotes that are not dependent on water in order to reproduce. Amniotes lay eggs that are surrounded by an extensive amniotic membrane to facilitate gas exchange and waste processing in a terrestrial environment. There are approximately 8,000 species of reptiles living today that occupy all continents on Earth except Antarctica.
   • Birds
     • Birds are warm-blooded (endothermic), egg-laying vertebrate tetrapods. They are characterized by the presence of feathers and wings. Almost all birds are capable of flight. The few species that are not, such as ostriches and penguins, evolved from flying ancestor species but lost the capability over the course of their evolution. There are approximately 10,000 existing species of birds that live in nearly all habitats on Earth. This is the largest number of species of any of the tetrapod classes.