To understand the different adaptations of mammals, one must go back to their origins.
It is very likely that the appearance of mammals on Earth occurred at the beginning of the Mesozoic era. At this time there was a group of reptiles that had mammalian characteristics; They were very frequent from the Permian to Triassic period and are known as the group of Therapsids.
Over time, they gave rise to different evolutionary branches in which typical mammalian features appeared at the same time that they intermingled with reptilians. This happened about 180 million years ago, in the late Triassic, at which time they declined, leaving a line of descendants that would not re-emerge until after 100 million years, during which the great reptiles predominated on Earth. The first fossils definitively corresponding to a mammal were found in rocks of the Jurassic .
During this period there were already five different orders of mammals. One was made up of small, rodent-like mammals, which had dental characteristics typical of these animals, but became extinct during the Eocene.
A second order consisted of small, carnivorous mammals, with three-cusp molars, which also became extinct before the end of the Eocene. The third group consisted of mammals the size of a rat or a mole; They had an insectivorous diet and we can almost certainly identify them as the ancestors of today’s mammals. After the disappearance of the great reptiles at the end of the secondary era, this evolutionary line was developed successfully during the tertiary era, which is known for this reason as it was of the mammals.
There are no fossil remains representing the monotremes. The first fossils of marsupials and placental mammals were found in rocks dating from the Cretaceous period. It appears that marsupials were unsuccessful in competition with placentates and, in the early Eocene, were represented only by the family of opossums (or opossums) in North America, by several families in South America, and by many others in Australia. The earliest surviving fossils of placentae were found in western North America and western Europe; This group appears to have originated in the late Cretaceous period and, as the fossil record indicates, later spread rapidly throughout the Tertiary era to form the current group of mammals. Insectivores,
Features that allow mammals to successfully inhabit all habitats.
Mammals have evolved to exploit a wide variety of ecological niches, developing numerous adaptations. This has resulted in a multitude of anatomical, physiological, and behavioral differences that allow them to adapt efficiently to diverse functions and lifestyles.
The great adaptability of the individuals that make up the mammalian class has led them to inhabit all the ecosystems of the planet, thus becoming one of the dominant groups on Earth.
In many cases, species that are geographically and phylogenetically very distant from each other have adopted similar morphological structures, physiological functions, and behavioral skills. This phenomenon is known as convergent evolution.
1. Lung breathing.
In many cases, with the adaptation to the terrestrial environment, the mammals abandoned the cutaneous respiration of the amphibians and perfected the pulmonary respiration of the reptiles, generating an efficient respiratory system adapted to the requirements of this type of habitat.
This respiratory apparatus presents alveolar structures that allow the blood to be oxygenated very well, which has allowed them to be homeotherms. In addition, in the case of aquatic mammals, it allows them to remain submerged for long periods of time since the oxygenation surface of the blood (hematosis) is greater than that of other animals.
2. Viviparous reproduction.
As a consequence of leaving the water, mammals have internal fertilization, so that zygotes implant and develop in the uterus. The placenta provides food and oxygen to the embryo, also making it possible to excrete waste substances. For its part, amnion contains amniotic fluid, protecting the fetus from external shocks, among other functions.
These adaptations allow the young to develop inside the female, thus protecting them from the external environment. In addition, the fact that the females provide food to the young (milk), allowed greater freedom of movement and with it a greater survival capacity.
Living on land implies being more subject to thermal variations so that mammals developed fur to protect themselves from inclement weather as well as to help maintain the internal temperature, thus being able to withstand both cold and heat.
In many mammals, in addition to hair, a dense layer of fatty tissue appears under the skin, providing additional thermal protection.
4. Homeothermic capacity:
Mammals have different mechanisms to maintain their temperature within certain limits regardless of the outside temperature. To do this they consume a large amount of energy by increasing the metabolic rate to produce heat (hence the importance of the respiratory system) and lower the metabolic rate when the environment is warm.
Thanks to the self-sufficiency of heat, some homeotherms can survive in very adverse cold conditions and when the ambient temperature is high, the thermoregulation mechanism of the homeotherms goes down to save energy.
In addition there are other adaptations related to extreme environments such as special sweat glands, more effective kidney structures, hibernation and estivation (also related to food availability)
Many mammals have a vision suitable for low light levels, which is important when developing night activities as well as conquering new ecological niches.
In addition to vision, other sensory organs such as hearing and smell develop that allow them to adapt better to these habitats.
6. Adaptations of the skeleton.
The skull loses mass, maintains resistance and simplifies structures while allowing muscle development and effectiveness.
A secondary palate is formed, the middle ear is modified, and tooth specialization occurs. The mandible is made up of a single bone (the dental).
The extremities stop articulating on both sides of the trunk to do so below, increasing mobility.
7. Physiological improvement.
The conquest of new habitats or ecological niches required an increase in the physiological efficiency of mammals, so that the nervous system, circulatory, respiratory, and digestive systems were perfected, so that in addition to adapting to the environment, they also made better use of the resources.
Examples of mammals adaptations
Throughout the ages, mammals have developed numerous adaptations that have allowed them to evolve successfully in certain environments or environments . The adaptations of mammals are related to their morphology, which is habituated to the environment of their area of ??origin. One of the most important adaptations is the one related to its locomotion , this is how we have mammals:
Plantigrades: they are slow-moving mammals, for this reason they rest on the ground with the entire sole of their foot, as is the case with bears .
– Digitigrades: its march is fast thanks to the exclusive support of the fingers on the terrestrial area in which they transit, this locomotion is characteristic of cats and dogs .
– Ungulígrados: as in the previous case they support themselves with their fingers, but in these animals walking is more extreme, since they do it only with the tips of their fingers, so they acquire greater speed, for example, deer , deer, horses, etc. In all, the hoof that protects their phalanges stands out; Depending on the number of hooves, they are classified into artiodactyls (they have an even number) and perissodactyls (they have an odd number of hooves).
Mammals with adaptations to jumping: The most prominent are the lagomorphs , their long hind limbs enable them to run and make great jumps.
– Flying: animals capable of flight, their adaptations are different from that of the birds themselves .
Aquatic: mammals trained to live in aquatic environments, both in fresh and salt water.
Bats they are the only mammals with the ability to fly. Apart from their wing-modified hands, they have developed other adaptations, for example, a very sophisticated ear, or the fact of presenting, micro-helicopters, an improved ultrasound detection system.
Thanks to the lengthening of the forearm and also of his fingers, with the exception of the thumb, in addition to the presence of patagio, they have been able to adapt with powers for sustained flight.
Aquatic mammal adaptations
The adaptability of mammals that live inside the waters is amazing, as is the case of whales porpoises, manatee , dugong and dolphins . Its fish-shaped shapes and forelimbs turned into fins represent an extraordinary evolutionary conversion.
Also important are the sirenios with forelimbs converted oars, unlike cetaceans , joints present in the fins are mobile, also surprised developing snout and adapted for rooting in the marine environment.
Seals, sea lions, walrus, hippopotamus, platypus, otters, beavers and nutria, unlike the previous ones, can stay a long time on dry land, especially when the breeding season arrives. Their hydrodynamic bodies and fin-shaped forelimbs represent morphological adaptations to aquatic life, in addition to being able to move on dry land thanks to the preservation of their hindlimbs.
There are other mammals with aquatic customs, such as the otter or the extraordinary platypus , have developed interdigital membranes to swim nimbly in the water.
They are animals that inhabit wooded areas with abundant vegetation; In order to move between trees and undergrowth, they have developed special adaptations: long tails, prehensile tails as a fifth hand, some opposable fingers to hold on to the branches. The number of these mammals is very large, some are well known, for example, the sloth , the koala , the primates or the curious gliders, the latter have developed a membrane between the body and legs that enables it to glide, jumping comfortably between tree and tree , as is the case with the gliders.
Many mammals live in grassland habitats, among their adaptations the body adapted to the race, very sophisticated among predatory animals, the long legs of ungulates, or those that live in community and in which a great development of the sensory organs prevails. as a means of communication, not forgetting those who live in burrows, many with good qualities for digging galleries. The number of species is large by way of example, some species of small rodents , prairie dogs, even lions stand out .
Mammals of arctic zones
Adapted to survive in environments where low temperatures or extreme cold prevail, these animals have undergone special adaptations such as the musky ox and its bushy coat; coat changes consistent with weather stations, for example polar bears , arctic fox , variable hare ; the mane of the Arctic caribou , its own horns also present in female specimens or its ultraviolet vision, very useful to see better among the white snow.
It is surprising that there are animals that live in areas of extreme heat. Normally during the day they remain sheltered between weeds and burrows, their rather nocturnal habits helps them avoid high temperatures during daytime. Their bodies also undergo adaptations, mainly so that they can remain hydrated in the face of the low humidity in desert areas, a characteristic example is the camel and its powers to remain without drinking or eating for many days thanks to the storage of fat in its hump, they rarely sweat, so they retain good powers to retain fluid for a long time.