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Mammals (formally Mammalia) are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Mammals are divided into three main infraclass taxa depending how they are born. These taxa 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 millimeter (1- to 1.5-inch) Bumblebee Bat to the 33-meter (108-foot) 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, porcupines, beavers, capybaras, and other 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. According to cladistics, mammals are a sub-group of synapsids. Although they were preceded by many diverse groups of non-mammalian synapsids (sometimes misleadingly referred to as mammal-like reptiles), the first true mammals appeared in the Triassic period. Modern mammalian orders appeared in the Palaeocene and Eocene epochs of the Palaeogene period. From Wikipedia under the
GNU Free Documentation License What percentage of mammals give birth to their offspring head first? Q. I heard that most mammals give birth like that but giraffes are obviously mammals, because well, they don't lay eggs and they aren't platypuses. But then I thought about it and if a giraffe gave birth head first then, considering how tall it is, the baby would die... If most mammals gave birth head first then how could they have evolved into giving birth head last. And if they had originally been giving birth head first wouldn't all giraffes be extinct??? Asked by Walter - Tue Nov 18 23:16:30 2008 - - 4 Answers - 0 Comments A. most mammal give birth head first (yes giraffes are mammals, they also are not echidnas (another species of monotreme), although there are other species which give birth to live young and are not mammals, most sharks and some snakes for example, the eggs hatch inside the mother who then gives birth to the babies) giraffes do give birth head first, the baby drops on its head. it falls about five feet but it is all bendy and just is fine. in fact the drop may shock it into getting up and starting to feed. if giving birth head first was a major issue for a mammal (like dolphins), it would not take long for the frequency of breach births to increase in the population (especially as they already occur, so the species would not be waiting… [cont.] Answered by fray - Tue Nov 18 23:21:47 2008 How are mammals and primates different from each other? Q. I know that mammals and primates are warm-blooded, have body hair, have complex brains for thinking, and have mammary glands producing milk to feed their newborns. Human beings are both mammals and primates. So are gorillas, monkeys, and lemurs. Asked by caltam84 - Sat Mar 14 03:04:18 2009 - - 3 Answers - 0 Comments A. One is a subset of the other. All primates are mammals, but not all mammals are primates. That is really the only comparison that can be made, as you have already noted the distinguishing characteristics of mammals. Answered by lithiumdeuteride - Sat Mar 14 03:15:44 2009 Where can I find images and information on Ice Age mammals?
Q. Hi everyone! I'm doing a science project on Ice Age mammals and I need information and images of the mammals that lived in that era. I did some googling and couldn't find anything useful. Most of the links that came up were about the CG movies by Disney and most of the other sites had only images of their skeletons! I want information about their height, weight, etc. If you know of a site then please post it here! Thank you in advance! Asked by devvveo - Mon Jan 1 04:06:01 2007 - - 4 Answers - 0 Comments A. here are some for you Answered by hanumistee - Fri Jan 5 03:11:57 2007 From Yahoo Answer Search: "Mammals"
 news.google.com Mail Tribune Of the sick and dead bats tested in Oregon during the last 10 years, about 9.5 percent have had rabies. Any mammal in Oregon can be infected with rabies ... Warning issued about rabies after deaths of animals Mail Tribune all 3 news articles » news.google.com Berkeley Daily Planet It's interesting that even small birds tend to live longer than small mammals . Hummingbirds have to eat constantly to keep their metabolic fires stoked. ... news.google.com UPI.com The farmers depend on alpacas, small domesticated mammals related to camels and llamas, for both wool and meat. The farmers' survival depends on their ... and more » From Google News Search: "Mammals"  paranormal.com.au 307px x 475px | 58.00kB [source page] Seperate Prison Port > 19 Oct 2006 09 03 67k 0funny10 jpg 19 Oct 2006 08 02 62k news mammals main jpg 19 Oct 2006 08 52 58k Light Anomoly jpg 19 Oct 2006 08 48 58k  aquarticles.com 122px x 177px | 8.10kB [source page] of the seats were empty I found the stadium a little too large for comfort The performers seemed like mere dots in the distance The zoom on my camera makes them appear closer Behind the dolphin stadium is the Marine Mammals exhibit where the sea lions and dolphins could be seen up close From Yahoo Image Search: "Mammals"  wolf21m.blogspot.com wolf21m Sun, 24 Jan 2010 23:58:00 GM Here I will highlight many of the other mid-sized . mammals. that we saw on our trip. I am sure that there are many other species hidden away in my photo archive and in my brain that didn't make it into this post. ...  animalsworlds.com Animal World Sat, 23 Jan 2010 04:53:00 GM Animals worlds helps you to gain knowledge about animals, reptiles, fish, birds, etc. people who love to know to more about the wild zone can get lot of information in animals worlds. It provides information through photo gallery, ...  thebeaveronline.co.uk Louisa Mon, 11 Jan 2010 15:45:10 GM Among the big herbivorous domestic . mammals. , five are of global importance: the sheep; the goat; the cow; the pig; and the horse. How much of history can be explained by the fact that wild ancestors of these 'Major Five' lived only on ... From Google Blog Search: "Mammals" |
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