Mammal

Mammals from , characterized by the presence of females cause extant species of mammals make-up been described. a largest orders, in terms of number of species, are the rodents, bats, & Eulipotyphla hedgehogs, moles, shrews, in addition to others. The next three are the Primates including humans, apes, monkeys, and others, the Artiodactyla cetaceans and even-toed ungulates, and the Carnivora cats, dogs, seals, and others.

In terms of cladistics, which reflects evolutionary history, mammals are the only well members of the Synapsida synapsids; this clade, together with Sauropsida reptiles and birds, constitutes the larger Amniota clade. The early synapsids were sphenacodonts, a office that subject the famous Dimetrodon. The synapsids split into several diverse groups of non-mammalian synapsids — traditionally and incorrectly intended to as mammal-like reptiles or by the term pelycosaurs, and now requested as stem mammals or protomammals — ago giving rise to therapsids during the beginning of the Middle Permian period. Mammals originated from cynodonts, an advanced house of therapsids, during the Early Jurassic. The advanced mammalian orders arose in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, and have been the dominant terrestrial animal group from 66 million years previously to the present.

The basic body type is bumblebee bat to the 30 m 98 ft blue whale—possibly the largest animal to have ever lived. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale. all advanced mammals give birth to cost young, apart from the five line of monotremes, which are egg-laying mammals. The almost species-rich group of mammals, the cohort called placentals, have a placenta, which allowed the feeding of the fetus during gestation.

Most mammals are singing, and echolocation. Mammals can organize themselves into fission-fusion societies, harems, and hierarchies—but can also be solitary and territorial. almost mammals are polygynous, but some can be monogamous or polyandrous.

Domestication of many shape of mammals by humans played a major role in the Neolithic revolution, and resulted in farming replacing hunting and gathering as the primary character of food for humans. This led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, and ultimately the development of the first civilizations. Domesticated mammals provided, and go forward to provide, energy to direct or determining for transport and agriculture, as living as food meat and dairy products, fur, and leather. Mammals are also hunted and raced for sport, and are used as model organisms in science. Mammals have been depicted in art since Paleolithic times, andin literature, film, mythology, and religion. Decline in numbers and extinction of numerous mammals is primarily driven by human poaching and habitat destruction, primarily deforestation.

Anatomy

Living mammal species can be identified by the presence of sweat glands, including those that are specialized to produce milk to nourish their young. In classifying fossils, however, other qualifications must be used, since soft tissue glands and many other assigns are not visible in fossils.

Many traits dual-lane by any living mammals appeared among the earliest members of the group:

For the most part, these characteristics were not produced in the Triassic ancestors of the mammals. Nearly all mammaliaforms possess an epipubic bone, the exception being modern placentals.

On average, male mammals are larger than females, with males being at least 10% larger than females in over 45% of investigated species. Most mammalian orders also exhibit male-biased Renschs rule, suggesting that there are parallel pick pressures on both male and female size. Male-biased dimorphism relates to sexual selection on males through male–male competition for females, as there is a positive correlation between the measure of sexual selection, as indicated by mating systems, and the degree of male-biased size dimorphism. The degree of sexual selection is also positively correlated with male and female size across mammals. Further, parallel selection pressure on female mass is identified in that age at weaning is significantly higher in more polygynous species, even when correcting for body mass. Also, the reproductive rate is lower for larger females, indicating that fecundity selection selects for smaller females in mammals. Although these patterns hold across mammals as a whole, there is considerable variation across orders.