News tagged with mammals

Related topics: protein , species , genes , cells , brain

Slowing the ageing process—it's in your genes

Imagine being able to take a drug that can reduce the rate at which you age. Research by Massey University senior lecturer in genetics Dr Austen Ganley is making this dream one step closer to reality.

Sep 05, 2013
popularity 4.5 / 5 (19) | comments 3 | with audio podcast

Why do women go through menopause?

Menstruation is a reproductive quirk that humans share with only a few other mammals. But even stranger is the fact that women stop menstruating when they have a whole third of their lives left to live.

Jun 10, 2013
popularity 4 / 5 (1) | comments 0

Scientists discover the origin of a giant synapse

Humans and most mammals can determine the spatial origin of sounds with remarkable acuity. We use this ability all the time—crossing the street; locating an invisible ringing cell phone in a cluttered bedroom. ...

May 26, 2013
popularity 5 / 5 (3) | comments 0 | with audio podcast

Mammal

Mammals (formally Mammalia) are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.

Mammals are divided into three main categories depending how they are born. These categories are, monotremes, marsupials and placentals. Except for the five species of monotremes (which lay eggs), all mammal species give birth to live young. Most mammals also possess specialized teeth, and the largest group of mammals, the placentals, use a placenta during gestation. The mammalian brain regulates endothermic and circulatory systems, including a four-chambered heart.

There are approximately 5,400 species of mammals, distributed in about 1,200 genera, 153 families, and 29 orders (though this varies by classification scheme). Mammals range in size from the 30–40-millimetre (1.2–1.6 in) Bumblebee Bat to the 33-metre (110 ft) Blue Whale.

Mammals are divided into two subclasses, the prototheria, which includes the oviparous monotremes, and the theria, which includes the placentals and live-bearing marsupials. Most mammals, including the six largest orders, belong to the placental group. The three largest orders, in descending order, are Rodentia (mice, rats, and other small, gnawing mammals), Chiroptera (bats), and Soricomorpha (shrews, moles and solenodons). The next three largest orders include the Carnivora (dogs, cats, weasels, bears, seals, and their relatives), the Cetartiodactyla (including the even-toed hoofed mammals and the whales) and the Primates to which the human species belongs. The relative size of these latter three orders differs according to the classification scheme and definitions used by various authors.

Phylogenetically, Mammalia is defined as all descendants of the most recent common ancestor of monotremes (e.g., echidnas and platypuses) and therian mammals (marsupials and placentals). This means that some extinct groups of "mammals" are not members of the crown group Mammalia, even though most of them have all the characteristics that traditionally would have classified them as mammals. These "mammals" are now usually placed in the unranked clade Mammaliaformes.

The mammalian line of descent diverged from an amniote line at the end of the Carboniferous period. One line of amniotes would lead to reptiles, while the other would lead to synapsids, including mammals. The first true mammals appeared in the Triassic period. Modern mammalian orders appeared in the Palaeocene and Eocene epochs of the Palaeogene period.

This text uses material from Wikipedia licensed under CC BY-SA