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A mammal (from Latin mamma 'breast') is a vertebrate animal of the class Mammalia (/ m ə ˈ m eɪ l i. ə /). Mammals are characterized by the presence of milk-producing mammary glands for feeding their young, a neocortex region of the brain, fur or hair.
- Marine mammal
Marine mammals are mammals that rely on marine ...
- Mammal classification
Mammals by population. Mammalia is a class of animal ...
- Portal:Mammals
The Mammals portal. A mammal (from Latin mamma ...
- Marine mammal
哺乳动物 （ 英語 ： mammals ）或 哺乳类 （ mammalians ）是 脊椎动物亚门 四足总纲 哺乳纲 （ 学名 ： Mammalia ）下属所有 动物 的统称，是 羊膜动物 两大 演化支 之一—— 合弓纲 唯一尚存的种群，分 胎盘类 （绝大多数）、 有袋类 和 单孔类 三支 亚纲 。 与属于羊膜动物另一演化支 蜥形纲 的 爬行类 和 鸟类 不同的是，哺乳类具有 新皮质 、 毛发 、三個 听小骨 和布满 外分泌 腺 的 皮肤 ， 雌性 还會用特化的 汗腺 —— 乳腺 分泌富含营养的 乳汁 （ 哺乳 ）餵養幼崽 [1] 。
- Main Characteristics
- Primarily Nocturnal
- Main Groups
- Modes of Life
- Taxonomy
- Debate on The Meaning of "Mammalia"
Reproductive cycle
Most marsupial and eutherian mammals have a reproductive cycle known as the oestrous cycle (U.S: estrous cycle). Females are sexually active in the oestrous stage, when they are 'on heat' for a few days each month. If an ovum is not fertilized, the endometrium (uteruslining) is resorbed. Oestrus cycles may occur once or twice a year, or many times a year. Each type of mammals has its own frequency. Humans and primates, are quite different. They have a menstrual cycle. In this case, females ar...
Skeleton
One diagnostic feature of mammals is the lower jaw. Unlike earlier forms, it is a single bone, the dentary. This is one feature which can be seen in fossils, or at least those which are complete enough to have the lower jaw. Another diagnostic feature is the ear ossicles. Mammals have three little bones in their inner ear. These ear ossicles are bones which were, long ago, part of the lower jaw in early proto-mammals. There are quite a number of other features in the skull and limbs, so that...
Neocortex and behaviour
Another diagnostic feature is the neocortex of the brain, which no other vertebrate has. This is involved in the kind of flexible behaviour and learning typical of mammals. Reptiles and birds have much of their behaviour controlled by "inherited behaviour chains", which roughly translates as "instincts". Almost all animals can do some learning, but mammals do far more than other vertebrates. Their behaviour is much more flexible than lizards, for example, and that is made possible by their ne...
Once, most mammals were nocturnal. Today, many (more than two-thirds) are still nocturnal. It makes a lot of sense when you realise that the daytime was ruled by dinosaurs for so long, Primates (except humans) sleep at night in trees. They are active during the daytime, and some come out onto more open ground. Baboons(and humans!) are rather specia...
All mammals feed milk to their young, and protect and look after them. The vast majority of mammal species give birth to live young, these are the placental mammals, most of which are classified as Eutheria and a small number are classified as marsupials. Marsupials are mammals with pouches to carry young in, like the kangaroo. There are only five ...
By number of species, mammals (with 5488 species), are not the most successful vertebrates. Birds, with about 10,000 species have nearly twice as many, and reptiles have just as many as birds. Fish have even more species. There are 27,000 species of fish, of which nearly 26,000 are bony fish.However, the word "fish" covers more than one class of an...
The evolutionary relationships among land vertebrates is as follows: 1. Tetrapoda (land vertebrates) 1.1. Amphibia(lay eggs in water) 1.2. Amniota (lay cleidoic eggs) 1.2.1. Sauropsida (all true 'reptiles') 1.2.2. Synapsida (all 'mammal-like amniotes') 1.2.2.1. Pelycosauria 1.2.2.2. Therapsida (in particular, the Cynodontia) 1.2.2.2.1. Mammalia(bea...
Because two quite different dates are given in the taxobox, an explanation is needed. Rowe defines mammals as "the taxon originating with the most recent common ancestor of extant (living) Monotremata and Theria". That puts the emphasis heavily on living mammals, where, as Rowe points out, the database of characters is extensive. Kemp explains the ...
哺乳動物（英語： mammals ）或哺乳類（ mammalians ）是脊椎動物亞門 四足總綱哺乳綱（學名： Mammalia ）下屬所有動物的統稱，是羊膜動物兩大演化支之一——合弓綱唯一尚存的族群，分胎盤類（絕大多數）、有袋類和單孔類三支亞綱。
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