These vertebrates belong to Class Mammalia and they are commonly called mammals. The name was derived from the Latin word “Mamma” which means breast. They have mammary glands that secrete milk when she is feeding her young. Mammals have 5000 species with 19 groups called orders.
A mammal is an animal that gives birth and raises its young on milk. They are covered with hair, fur and most of them have specialized teeth that allows them to cut and chew food. Mammals have a highly developed nervous system showing high intelligence compared to other vertebrates -- vertebrates are animals with backbones.
Mammals include most of the animals in Kingdom Animalia and some of these are: elephants, cats, dogs, whales, elephants and also human beings who dominate the earth now. Mammals evolved from a group of reptiles known as “Therapsids”. The earliest mammals were recorded and have lived over 200 million years ago. These mammals are only 5 centimeters long and spent most of their time in trees.
Life of Mammals
The life span of a mammal varies depending on their size. Most of small mammals with pointed nose survive for less than a year because of exhausting themselves for too many activities. While horses can live about 20 years, 50 years for chimpanzees, 60 years for elephants and over 110 years of human who has the longest life span of any mammals.
Mammals have thrived to some of the most extreme habitats. Some are warm-blooded or endothermic animals that can maintain their body temperature even in a narrow range despite of the drastic changes in the environment. Some mammals who have adapted to extremely cold habitats are polar bears who can survive on Arctic, Ice, Arctic foxes can even sleep in open snowwith temperature as low as –68° C (-90° F). While kangaroo, rats and camels can live in a very hot place such as deserts.
Types of Mammals
1. Monotremes – Monotremes are the most primitive mammals and the only mammals which lay eggs. They make up the smallest subclass of mammals with only three species that can only be found in Australia, New Guinea and Tasmania. Monotreme’s reproductive and excretory systems share a single body opening that lay eggs. This is a characteristic of a unique mammal. Platypus belongs to Order Monotremata. An example of these are:
- Duck-billed platypus – females lay two or three eggs and incubates them in a waterside burrow
- Echidnas – females lay a single egg and incubates in a pouch formed by two folds of skin on her abdomen
Once the eggs of Monotremes hatch, they feed their young on milk by lapping it up from a special milk patch on the underside of the mother.
2. Marsupials – This is the second subclass of mammals which contains 250 species. They give birth to live their young, but they are born in a much undeveloped state and continue their development in a pouch on the abdomen of a mother. They feed their young on milk that is supplied bythe mother’s nipples. Some of these are:
3. Placentals – This is the subclass of mammals that includes about 4300 species, making it the largest subclass. Not like marsupials, young placental mammal’s needs to stay more in their mother’s womb. They are nourished by a spongy organ called placenta that absorbs nutrient from the blood of the mother and transfers it to its young inside the body of the mother.
- Felines whales
There are varied habitats that mammals can live. On lands, some mammals like mole-rats dig burrows astheir refuge and shelter to raise their young while some live beneath the soil’s surface on plant roots. They dig through their spade-like paws and teeth that is alsoused as a defensive mechanism for it is highly sensitive to vibrations.
This is the most productive habitats for mammals and some of these are grasslands and farms. They feed on grasses and plants. Some of these grazing mammals are:
- Ruminants (Buffaloes and antelope)
Mammals that lived in the forest are well concealed, rarely band together for their safety and almost nocturnal. Nocturnal animals that are much more active at night. Some of these animals live on the tree top for protection and safety from predators and wild animals that are much larger to them. Some of these are:
Some forest mammals are ground-based dwellers such as bears, deer’s and wild pigs.
Tundra and Deserts
Some mammals can live in extreme habitats, these mammals have the capability in overcoming the hostile conditions for them to survive and perpetuate. One of these mammals that are equipped with the skill to adapt to hot temperatures like deserts is:
A camel can survive in arid places with limited water and can withstand the extreme heat. But some mammals that need more water will dry up in this type of habitat.
Freshwater and Saltwater
Some marine mammals have adapted to live in freshwater like:
- River dolphins
But most of the aquatic mammals live in saltwater specifically in the ocean. Some have the capability of living in very cold water, but most of them live where there is abundant food especially on water with low temperature. Some of the mammals that live in the oceans are: