We explain what biological evolution is, its relationship with natural selection and what the evidence is for the Theory of Evolution.
What is biological evolution?
Biological evolution is the series of heritable changes that a population of living beings undergoes over several generations. It is the process of change and adaptation to the environment of living beings.
A species can undergo a series of significant bodily or physiological changes, which in the long run are also capable of giving rise to a completely new species.
Different species have genetic and morphological evidence that links them to common ancestors, as occurs between humans and our cousins, chimpanzees.
Our common ancestor with them (that is, the species that diversified and gave rise to both theirs and ours) is estimated to have existed about 13 million years ago.
The last common ancestor
The common ancestor of all life on our planet lived 3.8 billion years ago. It was a single-celled organism known as LUCA (Last Common Universal Ancestorthat is, Last Universal Common Ancestor).
Key points of biological evolution
Biological evolution is a concept that encompasses the following key points:
- Species change over time. All of today's species diversity originated from past species that have been modified over many years and continue to be modified.
- Today's organisms come from past life forms All organisms (including humans) are related to each other and share a common ancestor.
- One species can transform into another through the action of natural selection. Darwin's theory postulated natural selection as a mechanism of biological evolution. According to Darwin, the environment provides conditions that make some heritable characteristics more advantageous than others. When natural selection acts on organisms of the same species, it can produce a series of cumulative changes that, after sufficient time, end up giving rise to new species.
The origin of biological diversity
To understand biological evolution, it is useful to go back to the origin of life on Earth, billions of years ago.
The first forms of life competed with each other for access to food and energy . Those that were more successful in that competition (that is, they had characteristics that were advantageous to the environment) reproduced more than others.
This process of survival and transmission of heritable characteristics more adapted to the environment is called natural selection, and it was the mechanism that Charles Darwin proposed when he proposed his theory in 1859.
The best adapted organisms reproduced more and conquered new nutritional niches, while those with less advantageous characteristics reduced their proportion until, eventually, they became extinct.
This process spanned billions of years on our planet, and gave rise to what we know today as species: groups of genetically related living beings capable of reproducing among themselves.
Biological evolution according to Darwin
The idea of evolution emerged in the 19th century the result of various contributions in numerous sciences.
However, the most important and accepted theory of evolution was the one proposed by Darwin in 1859 and published in the book The origin of species. This theory is also known as darwinism.
Charles Darwin (1809-1882) was a British naturalist who, after some studies in the United Kingdom, undertook a journey that was fundamental for modern biology.
On board the HMS Beagle (commanded by Captain Fitz Roy), Darwin joined an expedition in which he was able to make numerous observations of the flora and fauna in different geographical regions.
He noticed that many species of animals from distant places were similar to each other, except for significant physical differences. They were the same animals, but with different characteristics, which changed depending on geography.
These observations encouraged him to propose a theory of evolution that would provide an explanation of the relationship that exists between species, the environment and the fossil remains of extinct species. According to Darwin's theory of evolution, all species had derived from other simpler forms of life .
What is natural selection?
Darwin's most revolutionary contribution was the idea of natural selection as the cause of biological evolution. Darwin postulated that the natural environment provides specific conditions that favor or disfavor the prevalence of certain heritable characteristics of organisms.
Currently, a synthesis of the Darwinian principles of natural selection is supported, along with those of Alfred Russel Wallace (who independently proposed a theory of evolution very similar to Darwin's in 1858).
Later, Gregor Mendel's Laws of heredity, and some other relevant scientific advances, ended up giving a modern version of biological evolution.
Evidence of biological evolution
The evidence of evolution is diverse and is found in different fields of scientific knowledge. For example, paleontology has found fossils of extinct animals but similar to some degree to the species we know today.
On the other hand, for the comparative study of the organs of the different known animals (and even humans) anatomical similarities have been discovered that point to a common biological ancestor for different species, and even vestiges of ancient forms of the species, such as remains of front leg bones in the skeleton of snakes.
Similarly, embryology has discovered similar patterns of development in the initial stages of the life of different animals, including humans, which support the idea of a common ancestor. For example, in some stages of the formation of birds and vertebrates, the embryo shows the presence of gills, which makes them related to fish.
Something similar occurs with cellular biochemistry, which has almost identical processes in different organisms, or with recent advances in the reading of human DNA, 99% of which is identical to that of chimpanzees.
References
- Curtis H., Barnes N., Massarini A., Schnerck A., BIOLOGY. 7th Edition. Panamericana Medical Editorial (2008).
- Bombara N., Godoy E., et al. BIOLOGY 2: Origin, evolution and continuity of biological systems. 1st edition. Santillana (2018)
