Examples of Evolution

Is named biological evolution (Or simply evolution) to the process of hereditary changes in the genotype and phenotype of living beings, which occurs over successive generations and which eventually gives rise to new species, as life adapts to the environmental conditions in which it develops. Evolution consists of the continuous adaptation of living beings to their environment, which compete with each other to be the species that performs best and reproduces the most, and transmitting these adaptations to their descendants.

Evolution is a long-term process of change, which little by little transforms one species into another, as certain selective pressures (natural selection) act on life to sentence some species to extinction and others to survival. Therefore, all living beings of all kinds that exist on planet Earth come from the same common ancestor, which existed around 4.35 billion years ago, and which would have evolved in a multitude of different directions, to give way to the different realms of life that we know.

Although since Antiquity it has been suspected that the relationships of physical similarity between organisms point to a similar origin, the theory of evolution, for its part, arose in the 19th century thanks to the then recent advances in paleontology and genetics. These advances verified the suspicions of many scientists who, since the 18th century, already proposed that the species of living beings have been changing over time, and helped the British naturalist Charles Darwin (1809-1882) to propose his famous explanation on The origin of speciespublished in 1859.

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At the time, the formulation of these first scientific theories on evolution was controversial and led to a significant scientific debate. Today, however, these theories have been updated and demonstrated, thus giving way to the modern evolutionary synthesis.

examples of evolution

There is numerous evidence of biological evolution, both in current and extinct living beings:

  1. The birch butterfly (biston betularia). This species of moth, common in northern Europe, gets its name from the fact that its traditional coloration, white with brown spots, was ideal for camouflaging with the trunks of birch trees. This was the case until the Industrial Revolution broke out in England, and the soot from the factories began to darken the walls of the houses and the trunks of the trees. From then on, the white butterflies stood out and were easy targets for their predators, which meant that their populations began to dwindle. At the same time, a minority variant of the same species, whose coloration is dark instead of white, began to rebound until it became the most common, since its dark color allowed it to better camouflage itself in the new environment of the time. This is an emblematic case of natural selection in Darwinian evolution.
  2. Modern penguins (Spheniscidae). Penguins are the only flightless seabirds that exist, whose bodies instead of responding, as in other birds, to the lightness of flight, are adapted to swimming in cold waters. Thus, instead of large feathers and light bones, they have streamlined (torpedo-shaped) bodies with short, stiff wings, ideal for swimming, and small, compact feathers to keep them dry and warm. However, the arrangement of its bones shows its similarity with the rest of the birds, including evolutionary remains that serve only to fly, such as the keel sternum that joins the muscles and bones of the wings. Only in their case, the bones are denser and their size larger, as it results from their adaptation to marine life in the cold southern regions.
  3. The coelacanth (Coelacanthiformes). Coelacanths are perhaps the most famous living fossils: they are the fish biologically closest to terrestrial beings that exist in the abyssal regions of the sea, close to 500 meters deep. However, these fish emerged about 400 million years ago and were thought to be extinct. Only its fossils dating from the Carboniferous period (350 million years ago) are known, in which the fins with a bone structure can be clearly seen, precursors of the legs of the first land animals. With these fins, the coelacanth could crawl across short distances on land.
  4. The polar bear (ursus maritimus). It is one of the most popular bear species in the world and the largest terrestrial carnivorous mammal in existence today. The polar bear is characterized by its intense white fur that distinguishes it from its close species, especially the brown bear (ursus arctos), its closest relative. Today we know that the polar bear species diverged from its brown cousins ​​only about 150,000 years ago, long enough for its fur to adapt to the frozen landscape of the Arctic, where the color black would have immediately alerted prey to its presence. The closeness between these two species of bears is such that they can interbreed and have fertile offspring (the grolars), which leads to the assumption that polar bears arose from a population of brown bears that were stranded in the arctic and little by little They adapted to their environment.
  5. The flu virus (Orthomyxoviridae). The flu or influenza is a disease that circulates among human beings every year, despite the fact that our body naturally generates the necessary defenses to prevent reinfection. This is because these RNA viruses can adapt to so-called “herd immunity” by altering significant portions of their structure, through mutations. The virus adapts to survive, dodging human defenses that thereafter create new immunity and force the virus to mutate again, and so on. If the virus stopped adapting, it would find no susceptible hosts and would go extinct. Similarly, if the virus were to mutate into a lethal and dangerous variant, it would kill its hosts before it could spread effectively and massively, so the successful strains of influenza are always the most transmissible, that is, the most transmissible. less deadly.

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References

  • “Biological Evolution” on Wikipedia.
  • “Evolution” at the National Human Genome Research Institute (United States).
  • “Biological evolution” at the Autonomous University of Barcelona (Spain).
  • “Evolution (scientific theory)”in The Encyclopaedia Britannica.