The class mammals have over 5000 species attached to it, and they are in 26 orders (Jackson, 2012) . Humans and other lactating animals fall under these orders. Mammals do have at least three things in common that other animals do not have. They include the mammary glands that are used for the production of milk, middle ear bones and the most common is hair most mammals do have hair (Kingdon, 2013) . The ear bones are usually referred to as hammer and anvil. The hair on mammals does have several functions mostly for warmth and beauty. The milk produced by the mammary glands are usually from the female and are used to nourish newborns, this makes the female the most important aspect of the mammal (Schneider, 2012) .
However, there is new information coming from the mammal’s organisms that is the molecular-based evidence that is changing what scientists believe about some members of these groups. A good example of this evidence is the skunks, they have been recently placed with the family mephitidae , and they were traditionally thought to be of mustelidae (Jackson, 2012) . Organisms that are most advanced on this planet are the class of mammals with vertebrates; they usually have a heart that has four chambers, warm-blooded and a large brain, humans fall into this category. Mammals with backbones are referred to as chordates, and they belong to the phylum Chordate class (Jackson, 2012) .
Delegate your assignment to our experts and they will do the rest.
The mammals do exist in all continents of the world in all oceans and islands. Mammals have evolved over the centuries and leave in habitats of the planet from deserts Iceland’s and rain forests. The most remarkable of the mammals is the bat that they have the power of flight. Most mammals are considered to be partially aquatic since they live near streams lakes or any water body (Jackson, 2012) . There is a wide range of these mammals they include sea lion, muskrats, duck-billed platypus, seals among many other. Mammals like whales and dolphins are fully aquatic (Schneider, 2012) .
As much as most mammals do have hair some do not, however, they do get hair at a point during their life cycle (Jackson, 2012) . Most Mammals are either polygynous or promiscuous, polygynous means that the male has multiple female mates while promiscuous means both the female and male have several mates. Approximately 3 percent of the mammals are monogamous; this means that each male has a single female partner, in these cases, the male does to provide care to their offspring (Kingdon, 2013) .
The females in mammals are given more credit for the evolution of the species. This is because of the care they give to the offspring. Their commitment is biological since it starts even before the egg is fertilized. The female mammals do undergo a form of estrus cycle this is where the egg gets ready for fertilization (Jackson, 2012) . When the female eggs get fertilized they nurture their embryos in different ways some of the mammals do lay the eggs externally they are referred to as Prototheria, then there is the nursing iatrical young this is usually done by the marsupials this are the kangaroos where the offspring are usually in the pouch and finally the nourishing the embryos through the placenta (Kingdon, 2013) . The lifespan of mammals does range from one year to 70 years that is in the wild. Mammals like the bowhead Wales do live more than 200 years.
Mammals do eat a wide variety of foods, but the majority of mammals are carnivores, herbivores, or omnivores. The thing that threatens the mammals is the overexploitation, the destruction of their habitats and the importation of exotic species (Schneider, 2012) . Over the past five centuries at least 82 species of the mammal class have gone extinct. The union of conservation has listed approximately 1000 species that are at risk of extinction while 20 percent of them are critically endangered (Schneider, 2012) .
References
Kingdon, J., & Happold, D. (2013). Mammals of Africa . London: Bloomsbury Publishing.
Schneider, J. L. (2012). Sold into extinction: The global trade in endangered species . Santa Barbara, Calif: Praeger.
Jackson, S. M. (2012). Gliding mammals of the world . Collingwood, Vic: CSIRO Pub.
