Here we have simply stated out facts about mammals, then the distinctive characteristics of mammals and at last we have done the most common type of classification of mammals. Mammals are warm blooded air-breathing vertebrate animals that are categorized by their hair, three middle ear bones and the mother nursing their young ones with milk.
Mammals have the following distinctive characteristics that put them in the class of mammals:
Mammals have backbone and spines i.e. they are vertebrates.
Mammals have hair or fur on their bodies.
Mammals are warm blooded animals.
Mammals give birth to their young ones.
Mammals mother nurse their young with their own milk.
Mammals have lungs and need air to breathe.
Mammals that live on land have usually four legs and have ears that stick out of their bodies.
It would be correct to say that mammals are a group of animals with backbones, whose bodies are insulated by hair, which nurse their infants with milk and which share a unique jaw articulation. This, however, fails to convey how these shared characteristics underpin the evolution of a group with amazingly intricate adaptations, thrilling behavior and highly complex societies. Humans also belong to mammals which mean that the study of mammals allows us to know much about ourselves. In order to understand the term ‘Mammal’ we need to understand the complex range of form and function in them; and also the extent of individual flexibility which they demonstrate through their behavior.
The Kitti’s hog-nosed bat is the smallest mammal weighing no more than 1.5 g (0.05 oz), while the largest mammal in the world is blue whale weighing 100 times as much as a bat; the wolves are known to travel 1,000 sq. km (400 sq. mi); the Naked mole rat do not leave one burrow; the female Virginia opossums litters up to 27 babies; orangutan gives birth to one live baby. None of the aspects of these diverse lives of mammals is random. On the other hand, each individual mammal tries to expand its skill and fitness as compared to their other counterparts, to leave viable offspring.
Mammals are actually a class organized into 4,070 species; which are further sub-classified into 135 families, 1,000 genera, 18 orders, and 2 subclasses. While studying these subclasses, we come to know several mammals that were parted some 200-million years ago. These primitive mammals include egg-laying Prototheria (platypus and echidnas being the only survivors) along with live-bearing theria.
One of the characteristics of mammals is that the individuals belonging to the same species will behave differently. Therefore, we can say that the population of Spotted Hyenas living in one region may live their whole lives in 50-strong, steady clans, while in another place a fleeting connection of a few days makes up the most lasting adult relationships.
It’s not the skeleton that derives the two fundamental traits of mammals rather it’s the outside boundary to their bodies—the skin that springs the mammalian features. Skin glands (along with mammary glands) and hair are the two most important features which oozes sweat, sebaceous glands and milk. However, these attributes are linked to the endothermy, a state whose upshots affect every facet of mammalian life.
Several animals have their internal body temperature maintained within by the oxidation of food inside the body itself. These are known as endothermic animals. Certain animals keep constant body temperature while the temperature of others differs. The thermostat (in the brain) regulates the temperature. In modifying their body temperature impartial of the atmosphere, all the mammals (and birds) tend to unshackle from the alternative, ectothermic state usual of all other animals and embracing body temperatures rising and falling with the outside temperature. Having said that, ectothermic and endothermic animals are often referred to as cold and warm-blooded respectively which is not quite right.
A lizard, for instance, gains a heat from an external source (Sun), it can have a higher body temperature as compared to that of a so-called warm-blooded animals; however, when the air temperature falls the lizard’s body temperature also drops down, plummeting the ectotherm to an unavoidable lethargy. On the contrary, the internal processes of the endothermic mammal work independently of the external environment.
Mammals have different body temperatures—such as:
Several mammals are known to reduce the endothermy costs by giving up homoeothermy; they do not maintain a steady internal temperature. This is why the metabolic costs of hibernating mammals drop down while they are torpid; similar is the case with inactive bats. The body temperature of echidnas varies in between 25 – 37o C (77 – 99o F). The temperature control is primary so much so that they die of heat apoplexy in environments of 37o C (99o F). Bats cannot, however, uphold homoeothermy while at rest, due to the fact they have a huge area for the heat loss in their wings but they are surely capable to enable their temperature to fall. While they awake bats are cold so much so that they have to undergo physical jerks to restore their body temperature before take-off.
In the Mesozoic epoch, the cooling-climate might have led to the extinction of huge, naked, ectothermic dinosaurs. However, the entire fluctuations left adverse effects on the on the smaller dinosaurs as compared to those of bigger ones; one of the possible reasons was that the smaller reptiles have greater surface-area-to-volume ratio and thus more quick heat loss. Thanks to the evolution of lactation that allows young mammals to grow quickly and become adults under the supervision of parental care.
The mammals’ skin is embedded with the coiled sweat glands through which the watery fluid is secreted. These glands tend to evaporate when expressed onto the skin’s surface and in the process draws heat from the skin thereby cooling it. There is a variation in the abundance and distribution of sweat glands onto the mammals’ skin. Primates exhibit sweat glands while sea cows, golden moles, and whales do not have any glands whatsoever. The mammals having a few sweat glands tend to lose heat by saliva evaporation called panting.
Mammals display distinctive characteristics in relation to their backbones as well as social significance of their smells. Most mammals communicate through complex odors which is produced by the sweat glands or sebaceous. Every mammal has a unique placement of scent glands. Elephants have glands at the back of their eyes while mule deer have on their lower leg, and hyraxes have glands in the middle of the back. While these scent glands serve an important function for many mammals they also give reason to humans to hunt them. Mammals typically use scent-glands as territorial markers.
Mammals, as we know, are vertebrates that give birth to live young (viviparity) but not only do they perform this function, there is something else that makes them unique such as feeding milk to infants that are still inferior and small copies of their parents. To a large extent a young mammal continues to rely on its parents in the initial days which are indicated by the supply of its mother’s milk until it reaches the maturity age after which they contend with adults. As compared to other viviparous vertebrates, mammals are born small (the average litter is about 10% of mother’s weight), reducing the burden upon their swift mothers, but they deem to become independent of their parents very quickly, perhaps due to the development prolonged by lactation and hastened by endothermy.
The parental care is completely dietetic in the tree shrew, Tupaia, as the mother visits their juveniles only once in 48 hours merely to nurse them for few minutes. Nonetheless, specifically where the food is subtle, additional parental care relieves the transition to adulthood; indeed, since the female can store fat (and scarce materials) in anticipation of nursing and thereafter convert it to milk, she is free to spend more time with her offspring if necessary. Carnivores (e.g. African wild dogs and wolves) often drag their prey back to the habitat for regurgitating it to their offspring. Koalas are known to feed on poisonous eucalyptus leaves and makes special feces of partially digested and detoxified material on which the weanling feeds. Due to lactation, not only infants’ dependence becomes extended but also it separates young mammal from the environment; the mother overcomes short-term food shortages as she continues to lactate and if required, activates its own minerals, trace elements, and tissues to feed infants. Parental care extends the infant mammal’s training in compound adult skills.
Thanks to the evolution of lactation in mammals that leads to an ultimate increase in the sophistication of mammalian teeth. One of the strange characteristics of mammalian teeth is that they are encased in a dead shell once they are developed; they will not grow in girth. Because of lactation, the time at which teeth grow, increases; this might have been a precondition for the evolution of a compound occlusion (fitting together) of cusps of teeth in lower and upper jaws which is feature for mammalian teeth and is essential for chewing. These kinds of teeth wound have thrown out of alignment in case of a growing jaw. The process of lactation is necessary since it delays the need for teeth until the time jaw becomes fully grown up. Therefore, the mammalian jaw needs to grow faster and it certainly does. Obviously, few mammals are huge so much so that they grow in years which ultimately lead to special adjustments in their tooth eruption.
An elephant jaw, for instance, takes almost 30 years to develop fully but the upper and lower jaws are absolutely aligned since elephant’s premolars and molars break out serially, which means one tooth at a time.
Mammals are commonly classified into:
Facts about mammals