When talking about the evolution of animals, we must take into account that it depends directly on the ecosystem in which the species live and their physical and anatomical characteristics. This evolution is very important since, thanks to it, the variety of species is increasing as well as their adaptation.
What is biological evolution and what is its origin?
The first thing we must be clear about before talking about evolution and origin of animals, is what biological evolution is as such. One of the most surprising and important scientific studies that scientists have managed to do is that of biological evolution.
Evolution as such is the process by which living organisms go through a modification or change over time and generations. This type of process, which almost all the species on the planet have gone through, is a really complex process, since the ancestor of a species can also be the ancestor of many other species that, at present, do not share many physical characteristics. or anatomical.
A clear example of this is the first known bird in history, the Archeopteryx, which comes from more than 150 million years ago, this bird may perhaps be the ancestor of the 10.000 species of birds that we all know today although it may not be so.
At present, and thanks to the technology that allows the use of molecular techniques, paleontological studies and phylogenetic analyses, it is currently at our disposal to be able to know and understand how the evolution that living beings have had to throughout the passage of time and the history they have lived within our planet.
There are many who always wonder what is the evolution of animals and what are the factors that are taken into account for the analysis of these evolutions. To answer these concerns, we have to delve into the great work of literature "The Origin of Species" by Charles Darwin, which, within his "Theory of the Evolution of Species" told us about the way in which animals they have undergone anatomical and behavioral modifications in order to be able to adapt to the environment in which they find themselves.
In the same way, we talk about how these same species have had to learn to be strong and compete in order to survive, this is how they begin to comply with "the laws of natural selection and the survival of the best adapted ”.
Charles Darwin and his Theory of the Evolution of the species
Charles Darwin was one of the most important scientists in the nineteenth century. He was the one who created the famous work, "The Origin of Species" that was published in 1859 and which caused great controversy and fury among readers, scientists and those who were curious about this topic.
Within this magnificent work, Darwin developed what we know as the theory of evolution, which he had previously published himself together with Alfred Russes Wallace in 1858.
In his book it was shown how all the species that existed were related, in addition to that, he also talked about how the geographical distributions in which these species were found, gave a clear reflection of the relationship they had.
Within the same book, it was also explained the kinship that existed between the fossil organisms that were found at that time, with the current animals, and that, in addition to this, all living forms were linked in one way or another, these thanks to the only “tree of life”.
It was in this way that Darwin proposed his own model of the origin and evolution of animals through natural selection, also known as "the survival of the fittest", which was based on the ecological studies that he managed to do himself and the experiences he obtained after breeding various animal species.
genes and heredity
Something that Darwin was clear about is that evolution could not take place if there is no inheritance. During his life, Charles did not know what we now know as modern genetics, however, during the course of the XNUMXth century, it became quite clear to everyone that the genetic code he was so painstakingly searching for lay within the Chromosomes that were found in the nucleus of the vast majority of cells that living beings possess.
Human cells have between 20.000 and 25.000 genes, each of which contains instructions in the form of codes that form the specific characteristics of each person. These same codes can be found mostly within the molecules of our DNA, these, in turn, are comprised of four chemical bases that are arranged in pairs. Each of our genes is encoded within a unique sequence of base pairs.
The evolution of aquatic animals to land animals
If we want to begin to know about what the history of the evolution of species has been, we must first learn about the origin of the Earth as such, it had its beginnings within the oceans. There were a large number of animals that were perfectly adapted to marine ecosystems, since, if life, was found within the oceans that made up the primitive planet, which was almost completely different from the planet we all know now.
Knowing this, we can affirm that, while the planet began to undergo changes and modifications, the animals were also forced to adapt and develop new modifications for themselves, to be able to become species that had the capacity to survive in the greatest part of the environments that existed at that time.
Thanks to the above, it is that the beginning of the evolutionary processes of animals that were aquatic to become terrestrial animals was achieved. These animals had to go through changes, little by little, they had to change their anatomy so that it adapted to the oxygenic atmosphere, as well as, they had to learn to be able to move on the ground, this process began with them first crawling and then begin with learning to fly or walk on all fours, although over time some even learned to move on two legs.
Evolution of vertebrate animals
When we talk about vertebrate animals, we talk about fish, reptiles, mammals, birds and amphibians, which have always shared several characteristics of their anatomy since they have a common evolutionary origin, which is the basis of what they are now. . When observing the development of the embryos of these 5 types of animals, we can see that they all have a very similar process and are quite similar.
Something that we must also know is that some of the vertebrate animals have vestigial organs, that is, they do not have a specific function. An example of this are the pelvic bones and the lower extremities that whales have and that in themselves do not have a function, at least not one that is known. This shows us that, at the origin of their species, these animals had 4 legs and were terrestrial.
There are also those with similar limbs, which have a different structure and evolutionary origin, an example of this is the wings that birds and insects have. There are also homologous limbs, which have the same structures and evolutionary origin, but have a different function. A clear example of this is the forelimbs of humans and bats.
All these explanations and examples are clear evidence of how surprising the evolution of vertebrates in general is.
Evolution of invertebrate animals
These animals are more than 500 million years old on Earth, which is when they first appeared. Some of the studies carried out on this group of animal species have managed to demonstrate how the group with the largest number of invertebrate specimens, that is, arthropods, have evolved from worms that have similarities with the marine annelids that we know today, this has allowed these animals to still preserve that curious anatomy composed of differentiated segmentations.
However, due to the great anatomical and functional diversity possessed by the large numbers of invertebrates that exist, it could be really beautiful to be able to study each one of the groups separately and not in general, in this way, it would be much easier to understand and to know how their evolutionary process and origin has been, the reason why they do not have tissues or symmetry in their bodies, as well as how they can manage to develop carapaces or shells, as snails do.
examples of animal evolution
Let's get to know a small list of some of the animals that have evolved over the years:
Dogs
La Dog evolution It started from its ancestors, the wolves, this happened through a process of adaptability to be able to survive in different territories and when they began to be domesticated. Something that happens with other domestic animals that have had to go through a very similar evolution (dogs, cats, rabbits).
Giraffes
It happened through structural changes in the neck of these animals, due to the ecosystem that surrounded them and natural selection, since the specimens that were born with much longer necks were able to more easily reach the leaves that were higher up ( in the tops of tall trees), while those with shorter necks could not have access to them. In this way, they began to transmit to future generations the necessary information so that they could pass on the 70 genes that are responsible for the fact that the neck of the Giraffes are longer than those of other animals.
Human beings
The evolution of the human being began from its common ancestor, the chimpanzee, where the adaptation of bipedalism began, an important evolution that took the human being to the top, the evolution that he was human was responsible for the emergence of the species Homo Sapiens Sapiens, what each of us humans are today.
Animal evolution in reverse
We all get used to believing that the evolution of a species means that it will gain unique characteristics that will make it better able to adapt to its environment, however, this evolutionary process also goes through a process of loss, since there are species that lose capacities or that they begin to degrade, this occurs especially when the evolutionary cost is much greater than the benefit that will be granted.
We are going to know some examples of animals that had a reverse evolution:
The Penguins
A clear example of this type of evolution are the penguins, as these birds became birds that cannot fly. Formerly, the ancestors of the penguins were birds that could take flight, however, after the disappearance of the dinosaurs, they began to lose this ability to fly.
There are records of the oldest penguin that has been known, its fossil remains date back to the fact that it existed at least 60 million years ago, the characteristics observed in its physique indicate that, at that time, these animals were already excellent swimmers and had quite wings. short, so they were unable to fly. The penguins we know today still have physical and anatomical characteristics similar to those of their ancestors. However, losing the ability to fly allowed them to better adapt to the habitat where they live, as they began to grow larger than their ancient relatives, something that has been really beneficial for the species in general.
The snakes
According to the evidence that has been collected, there is clear evidence that snakes previously had their limbs, however, there are still debates among researchers about whether snakes managed to evolve from an aquatic or terrestrial bigeye ancestor.
According to the evidence found in the fossils, the snakes were very similar to what we know today as lizards, since they also had extremities that were used to dig into the earth, in this way, they could feel the vibrations in the earth of their prey. and also hide.
The birds
There are some theories about evolution of birds, which indicate that the teeth that ancient birds possessed became smaller and smaller, thus resulting, after a period of time, in the beak that they now possess, this evolution was carried out with the aim that the weight in their heads it was much less when they were in flight. However, other studies carried out later showed that both the primitive beak that these birds had and their teeth were changing at the same time, to give as a result the toothless beak that all the birds we know now have.
