Mammals: characteristics, classification, summary

You mammalsare vertebrate animals from Chordata phylum, known mainly for having hair and mammary glands. The presence of a differentiated diaphragm and teeth are also typical characteristics of mammals.

At the moment, more than 5,300 species are known, among which the human species is included. These species are quite distinct from each other, being possible to find, for example, terrestrial and aquatic species. Because they live in different environments, we can also observe different forms of locomotion, like the swimming of whales, the flying of bats and the ability of certain squirrels to glide.

With regard to food, these animals are also very different., existing species:

• carnivores,

• herbivores,

• omnivorous.

Mammals have a complete digestive system, closed, double and complete circulation, pulmonary breathing, excretory system composed of two kidneys and a developed nervous system.

Read too: Blue whale – representative of aquatic mammals

General characteristics of mammals

Mammals constitute a very diverse class (Mammalia class)

of vertebrate animals that includes beings with the most diverse characteristics and life habits. They are animals that live in practically all environments, and there is no parasitic species.

• Unique characteristics of mammals

Some features are unique to this class, such as:

• presence of hair,

• mammary glands,

• diaphragm,

• teeth differentiated.

Bats are mammals that have the ability to fly.

You by the of mammals, which can cover all or only part of the body, are extremely important to maintain body temperature. These animals are endothermics, and the presence of thermal insulation is important for temperature conservation.

Heat retention is also guaranteed due to the presence of a fat layer located just under the skin. In addition, the presence of sweat glands, in some representatives, it helps in this function, because when the temperature is very high, they eliminate sweat, which helps to cool the body.

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Mammals also have mammary glands, who are responsible for producing milk, which serves as food for their puppies. This is one of the most striking features and responsible for the name given to this class. O milk is provided by all females to their offspring, ensuring that they receive a nutritious and fundamental food for their development. Milk contains:

• fats,

• carbohydrates,

• proteins,

• mineral salts,

• vitamins.

Mammals breastfeed their young with milk.

The teeth of these animals are differentiated and each is responsible for a certain function. There are teeth, for example, adapted for cutting and tearing (incisors and canines) and for crushing or grinding (premolars and molars) food. Depending on the diet adopted by the animal, these types of teeth can be more or less developed. Herbivores, for example, usually do not have canines, and these teeth are quite developed in carnivorous animals.

Another important feature of mammals is the presence of a muscle that divides the chest and abdomen called the diaphragm. The lifting and lowering movements of this muscle are essential for lung ventilation. THE breathing of all representatives is pulmonary, including aquatic species (whales and dolphins).

Whales are animals that live in the aquatic environment, however, like other mammals, they have lung respiration.

See too: What are the types of animal breathing?

• Physiological characteristics of mammals

O digestive system of mammals is complete. In platypus and echidnas, it starts in the beak and ends in the cloaca, unlike other species, where it starts in the mouth and ends in the anus.

The cardiovascular system of mammals has a heart with four cavities (two atria and two ventricles), just like in birds. THE circulation is closed, since blood flows exclusively inside blood vessels (arteries, arterioles, veins, venules and capillaries), and pair, since it has two circuits (the pulmonary and the systemic circuit), which means that the blood passes through the heart twice. The movement of these animals is complete, for blood rich in carbon dioxide does not mix with blood rich in oxygen.

In mammals, the excretion occurs thanks to the presence of two kidneys, that guarantee the filtration of blood and the formation of urine. After the urine is formed, it moves towards the ureters, which will lead to the bladder, where the urine is stored until it is released. Urine is expelled to the outside through the urethra. In mammals, the main excretion product is urea.

The nervous system of mammals is also noteworthy, and these animals are endowed with a quite developed brain, when compared to other vertebrates of equivalent size. As in other vertebrates, the mammalian nervous system is divided into:

• system nograssy çinput (SNC): formed by the brain and spinal cord;

• system nograssy Pspherical (SNP): formed by the nerves and ganglia.

Mammals have a complex sensory system, being possible to observe the presence of the following senses:

• eyesight,

• hearing,

• smell,

• tact,

• taste.

In dolphins and bats, it is also possible to verify the ability to detect barriers and objects in environments, during their locomotion, through the call echolocation, which is based on the emission of ultrasonic waves by these animals and the subsequent analysis of the generated echo.

mammal reproduction

mammals are animals dioic, that is, they have separate sexes. The fertilization in these animals is internal, it's the development is straightforward, therefore, a larval stage is not observed during its development. Most are viviparous, but there are oviparous representatives, which is the case of monotremes.

classification of mammals

It is customary to divide this class into two subclasses: Prototheria and Theria. The Theria subclass is divided into two infraclasses: Metatheria (marsupials) and Eutheria (placental). There is still the Allotheria class, however, all its representatives are extinct.

Subclass representatives prototheria(monotremes)characterized by laying eggs, common occurrence in reptiles. Another characteristic of these animals are the breasts without nipple. Platypus and echidnas, animals restricted to Australia and New Guinea are examples of monotremes.

Platypus are mammals that lay eggs.

You marsupials (Metathery) they are animals that have an extremely interesting feature with regard to embryonic development. The offspring of these mammals they are not born fully formed, ending its development inside a bag called a marsupium. You kangaroos and possums are part of this infraclass.

Kangaroos are marsupial mammals.

You placental (Eutheria) represent the vast majority of mammals. Among the representatives, we can mention the man, dog, elephant, Bunny, giraffe, whale, among others. Its main feature is the fact that embryonic development takes place inside the uterus of the mother. Feeding and gas exchange take place through the placenta. Unlike marsupials, they are born fully formed, and the gestation of eutheriums is longer.

Also access: Ectopic pregnancy - pregnancy that occurs outside the uterine cavity

Summary about mammals

• The presence of hair, mammary glands, diaphragm and differentiated teeth are unique characteristics of mammals.

• Mammals are endothermic animals.

• Mammals have a complete digestive system.

• Mammals have closed, double and complete circulation. The cardiovascular system has a four-chambered heart.

• The mammalian excretory system is composed of two pairs of kidneys.

• Mammals have lung respiration.

• Mammals have a well-developed nervous system that can be divided into central nervous system and peripheral nervous system.

• Mammals are dioecious, have internal fertilization and direct development.

• Mammals can be divided into three groups: marsupials, monotremes and placentals.

By Vanessa Sardinha dos Santos
Biology teacher