Search results
Results from the WOW.Com Content Network
A mammal (from Latin mamma 'breast') [1] is a vertebrate animal of the class Mammalia (/ m ə ˈ m eɪ l i. ə /).Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle ear bones.
Molecular studies by molecular systematists, based on DNA analysis, in the early 21st century have revealed new relationships among mammal families. Classification systems based on molecular studies reveal three major groups or lineages of placental mammals, Afrotheria, Xenarthra, and Boreoeutheria. which diverged from early common ancestors in the Cretaceous.
Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles and birds , from which their ancestors diverged in the Carboniferous Period over 300 million years ago.
In zoology, mammalogy is the study of mammals – a class of vertebrates with characteristics such as homeothermic metabolism, fur, four-chambered hearts, and complex nervous systems. [1] Mammalogy has also been known as mastology , theriology , and therology .
[3] The mammary glands of mammals are specialized to produce milk, a liquid used by newborns as their primary source of nutrition. The monotremes branched early from other mammals and do not have the teats seen in most mammals, but they do have mammary glands. The young lick the milk from a mammary patch on the mother's belly.
Marsupials have the typical characteristics of mammals—e.g., mammary glands, three middle ear bones, (and ears that usually have tragi, [3] varying in hearing thresholds [4]) and true hair. [5] There are, however, striking differences as well as a number of anatomical features that separate them from eutherians .
All mammals have some hair on their skin, even marine mammals like whales, dolphins, and porpoises that appear to be hairless. The skin interfaces with the environment and is the first line of defense from external factors. For example, the skin plays a key role in protecting the body against pathogens [3] and excessive water loss. [4]
Placental mammals (infraclass Placentalia / p l æ s ə n ˈ t eɪ l i ə /) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished from monotremes and marsupials in that the fetus is carried in the ...