Mammals are a class of animals that have managed to diversify by all means (land, sea and air) thanks to the many adaptations they have acquired throughout evolution. In addition to land representatives (typical of mammals), there are some mammals capable of flying , such as bats, and of living in the aquatic environment, the so-called marine mammals , such as dolphins and whales.
Mammals and their origin
The term mammal comes from the Latin ‘ mamma ‘, which in Castilian means teat or breast, and the suffix ‘ fero ‘, whose meaning refers to carrying or carrying it. Thus, the meaning of the word mammal refers to ‘that carries breasts’, that is, it identifies those animals that in their first days of life feed on mother’s milk through mammary glands .
Mammals are a group of animals more evolved than other groups. Its origin is located about 245 million years ago . Back then, they still didn’t look like they do today, but were small insectivorous animals that descended from therapsid reptiles of the Triassic period. After the disappearance of the dinosaurs, during the Cretaceous period, mammals began to evolve and occupy their ecological niches. For this reason, mammals are considered to have a common ancestor, that is, it is a monophyletic group.
Among the general characteristics of terrestrial mammals , which are what differentiate them from other groups of animals, the following stand out:
- They have a synapsid skull (skull with a hole behind the orbits of the eyes) with a head that remains attached to the trunk through the neck. They also have a spinal column as the central axis of the body.
- Brain volume greater than other groups of animals, that is, a brain larger than that of other types of living beings. This trait allows them to acquire greater psychic abilities and incredible learning faculties.
- Presence of waists on their extremities , which allow them to lift the body off the ground.
- Presence of a mouth composed of lips and teeth . In certain cases, such as platypus, the teeth only appear during the juvenile period.
- Body covered with hair , although in some cases the hair is little or no hair and the skin acts as insulation.
- Presence of glands with specific functions in the deep layers of the skin. Among these are the mammary glands (they produce milk to feed the young), sweat glands (they facilitate the cooling of the body and develop excretory functions), odoriferous glands (they transmit signals) or sebaceous glands (they provide protection to the hair).
- Presence of four limbs that allow them to stand , on all fours or on two legs, and move in the terrestrial environment.
- Ability to maintain a constant body temperature thanks to their diet and regardless of the ambient temperature (homeothermic animals).
- Breathing through lungs . Thanks to the diaphragm and its contraction movements, the air gets into the lungs.
- Presence of a heart made up of four chambers (two atria and two ventricles) and a double, closed and complete circulatory system.
- Most mammals have auditory appendages or ears or pinna , even mobile in many species.
How Mammalian Animals Reproduce
Regarding their reproduction, terrestrial mammals present another distinctive characteristic, such as viviparous reproduction . In this type of reproduction, the embryo develops inside the mother’s womb and the individuals have internal reproduction , that is, the ovule produced by the female is fertilized thanks to a copulatory organ in the males. There are some exceptions to the viviparous reproduction of mammals, one of them is the monotremes (platypuses and echidnas), which lay eggs , although once hatched the young feed on milk through the mother’s mammary glands.
The order of Marsupials is intermediate between viviparous and Monotreme mammals, since the young are born prematurely and cling to their parent’s nipple, inside an abdominal pouch or pouch (absent in some species).
Feeding of mammalian animals
Finally, to finish talking about the general characteristics of mammalian animals , we want to inform you about their diet.
The diet of terrestrial mammals is highly varied between species, and can be carnivorous, herbivorous, omnivorous, or even insectivorous. The ability to have different types of diet is proof of its greater evolution compared to other groups. Also, depending on your eating habits, your digestive system undergoes different adaptations.