We explain what mammals are and what their main characteristics are. In addition, the types of mammals and some examples.
What are mammals?
Mammals are known as vertebrate and warm-blooded animals belonging to the mammalia class , whose essential characteristic is that females have mammary glands that serve to generate milk with which to feed their young. About 5,486 current species of mammals are known, including the human being himself , and most of them are all viviparous, except for monotremes (such as the platypus).
Mammals date from approximately 200 million years ago , from some common ancestor derived from synapsid reptiles or mamiferoids, which emerged during the Triassic Period. But unlike reptiles , they have the ability to regulate body temperature, which may have been key in their survival of the K-Pg (Cretaceous-Paleogene) Mass Extinction Event that extinguished non-avian dinosaurs.
That of mammals is an extremely diverse and numerous group of animals, one of the most and best studied by humans among the entire animal kingdom . The morphological diversity of its member animals is such that they serve as an example from a blue whale, a giraffe and a kangaroo, to a dog, a platypus or the human being himself.
However, all species of mammals share certain minimum characteristics, such as:
- Presence of mammary glands. Located in the body of the female of the species , with which they secrete milk and breastfeed their young.
- Jaw composed of a dental bone. Instead of several bones or moving parts. In addition, the jaw articulates with the skull between the dental and squamous.
- They have an ear with three ossicles. Known as anvil, hammer and stirrup, with the exception of monotremes (which have reptilian ears).
- They have hair at almost every stage of their life. And all species have it to some extent.
- They can regulate body heat. Through sweating, tremors and other ways to preserve homeostasis without resorting to external elements.
Types of mammals
A first classification of mammals is given by distinguishing between the ways in which their young are formed, as follows:
- Monotremes Those few species of mammals whose females lay eggs after they have been fertilized. It is the oldest evolutionarily group group.
- Marsupials These species (around 300) of mammals give birth to their young after a short period of gestation, after which they must climb through the maternal skin until they enter a sack of skin known as marsupium, within which they will be protected and will have Access to the breasts. After several months, when fully trained, they will leave the marsupium to start their independent lives.
- Placental Most species of mammals belong to this category, characterized by gestating their young for several months and giving birth later when they are ready to lead an independent life. In the case of the human being, however, the young are born in a high state of defenselessness that require almost complete care during their first years of life.
Marine and terrestrial mammals
Although mammals evolved evolutionarily as a terrestrial species, and the vast majority lead a continental life, there have also been the case of certain terrestrial species that have returned to the aquatic habitat , adapting their body in the process to swimming. Thus, they have changed legs for fins, mutated the type of fur and altered the proportions of fat in your body to conserve heat, although they have not lost in the process or pulmonary respiration , breastfeeding, or other characteristic physical features.
Examples of mammals
Examples of mammals abound in everyday life and in other natural areas:
- The human being himself. As well as primates and apes in their entirety.
- Dogs and canids all. From our common pets, through wolves, jackals and hyenas.
- The felines all. From cats to lions , panthers, tigers, etc.
- The milking animals. Like sheep, cows or goats.
- Aquatic mammals Like the dolphin, the blue whale, the sea lion, the seals or the manatees.
- The great African and American ruminants. Like rhinos, giraffes, buffaloes, etc.
- The bats. Unique genus of flying mammals.