Search results
Results from the WOW.Com Content Network
Humans are synapsids, as well. Most mammals are viviparous and give birth to live young rather than laying eggs with the exception being the monotremes. Triassic and Jurassic ancestors of living mammals, along with their close relatives, had high metabolic rates. This meant consuming food (generally thought to be insects) in much greater quantity.
Birds figure throughout human culture. About 120 to 130 species have become extinct due to human activity since the 17th century, and hundreds more before then. Human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry.
Reptiles are generally considered less intelligent than mammals and birds. [31] The size of their brain relative to their body is much less than that of mammals, the encephalization quotient being about one tenth of that of mammals, [ 125 ] though larger reptiles can show more complex brain development.
Non-crocodilian reptiles have 3-chambered hearts, which are less efficient because they let the two flows mix and thus send some de-oxygenated blood out to the body instead of to the lungs. Modern crocodilians' hearts are 4-chambered, but are smaller relative to body size and run at lower pressure than those of modern birds and mammals.
While reptiles and amphibians can be quite similar externally, the French zoologist Pierre André Latreille recognized the large physiological differences at the beginning of the 19th century and split the herptiles into two classes, giving the four familiar classes of tetrapods: amphibians, reptiles, birds and mammals. [30]
Class Reptilia (reptiles, paraphyletic) Class Aves (birds) Class Mammalia (mammals) In addition to these, there are two classes of extinct armoured fishes, Placodermi and Acanthodii, both paraphyletic. Other ways of classifying the vertebrates have been devised, particularly with emphasis on the phylogeny of early amphibians and reptiles.
In anapsids, the ancestral condition, there are none; in synapsids (mammals and their extinct relatives) there is one; and in diapsids (including birds, crocodilians, squamates, and tuataras), there are two. Turtles have secondarily lost their fenestrae, and were traditionally classified as anapsids because of this.
The neomammalian brain consists of the cerebral neocortex, which is found in higher mammals, especially in the human brain, and is not found in birds or reptiles. The neomammalian brains structure is of great complexity, [3] and has evolved over time allowing humans to reach the top of the food chain.