We explain what Darwin's theory is, how it explains the origin of species and natural selection. Also, who was Charles Darwin.
What is Darwin's theory?
Darwin's theory is the set of scientific formulations proposed and developed by the British naturalist Charles Darwin (1809-1882).
Like Lamarck, Darwin thought that species are not fixed and immutable orders of life, but rather that they change gradually over time.
This theory, also known as darwinismexplains the origin of species diversity and postulates a mechanism of biological evolution known as natural selection.
Natural selection is a process that occurs as a result of the interaction of two factors: environmental conditions and the presence of organisms with different hereditary characteristics.
According to Darwin's theory, organisms can be modified over time because the environment in which they live selects advantageous hereditary characteristics.
Darwin's theory remains valid despite some inaccuracies and lack of knowledge characteristic of the time.
Darwin and natural selection
From his observations of the fossil record, Darwin was convinced that complex organisms came from simpler life forms which lived in the past and were modified over time.
Darwin proposed that the way this happened was through the action of natural selection. According to this mechanism, the natural environment fosters conditions that mean that, within the same species, some individuals can survive and reproduce better than others, because were born with hereditary characteristics advantageous for that environment.
As those individuals are more successful at reproducing, their offspring also inherit the advantageous trait. Thus, over several generations, one species can transform into another.
How does natural selection work?
According to Darwinism, environmental conditions (for example, greater or lesser availability of food, the presence or absence of predators) mean that, within the same population, some individuals may adapt better than others for having been born with some characteristic that is an advantage.
It is said that the organisms that make up a population have variability, because they are not all the same, they present slight differences.
For example, in a population of gazelles, some are faster than others, and this quality allows them to flee predators faster. Therefore, fast gazelles have a better chance of surviving and leaving offspring.
If this characteristic is hereditary, the descendants of the fastest gazelles will inherit that quality. They, at the same time, will be in better conditions than others to survive and leave offspring.
Little by little, generation after generation, the number of fast gazelles will increase, while the proportion of slow gazelles will disappear. It is said, then, that The environment exerts selection pressure on heritable characteristics.
In this case, the presence of gazelle predators is functioning as a selection agent, because it is the environmental condition that ends up separating the slow gazelles and, consequently, the fast ones are “selected” to give continuity to the species.
The origin of variability according to Darwin
For Darwin, the origin of variability between individuals was random. There was no particular reason why organisms of the same species had some differences from each other (i.e., were not identical).
He considered that the fact that there are variants between individuals of the same species (gazelles that are faster than others, birds with longer or shorter beaks) It was purely due to chance.
This idea differs from what Lamarck's Theory proposes, according to which organisms made some type of directed effort to obtain particular characteristics.
In summary, according to Darwin's theory, species change over time because the environment in which they live functions as a selecting agent for heterogeneous characteristics that occur among individuals of the same species. This phenomenon is called natural selection.
Importance of Darwin's theory
Darwinism was a revolutionary scientific contribution that laid the foundations for practically all of contemporary biology. Furthermore, it affected other sciences and even fields of humanistic knowledge.
Its precepts were embraced by social scientists at the beginning of the 20th century. For example, it originated social darwinisma doctrine that aspired to think about the functioning of societies in terms of natural selection, a central idea in the emergence of European fascism in the 20th century.
Who was Charles Darwin?
Charles Robert Darwin was born in Shrewsbury, England, in 1809. He was the son of a wealthy doctor and businessman, and was raised in the precepts of the Anglican church and free thought.
From a very young age Darwin showed talents for natural history and a passion for collecting biological specimens. In 1831 he embarked on the HMS Beagle to map the American South, as part of Robert FitzRoy's exploration. This trip was key in Darwin's life.
The numerous observations, drawings and conclusions he obtained from the coasts of the Azores, Cape Verde, Brazil, Uruguay, Argentina, Chile, Peru and Ecuador, as well as later from Australia, Cocos Island and South Africa gave him a fundamental perspective of the vast and diverse of life. Thus he obtained the keys to formulate his scientific theories.
The following years were dedicated entirely to the development of his work and the publication of numerous manuscripts, despite the fact that in the last 22 years of his life he suffered major heart conditions.
He finally died in Kent, England, on April 19, 1882, and received a state funeral at Westminster Abbey.
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References
- Curtis H., Barnes N., Massarini A., Schnerck A., BIOLOGY. 7th Edition. Panamericana Medical Editorial (2008).
- Audesirk T., Audesirk G., Bruce E., BIOLOGY 3: Evolution and ecology. 6th edition. Pearson education (2003).
- Bombara N., Godoy E., et al. BIOLOGY 2: Origin, evolution and continuity of biological systems. 1st edition. Santillana (2018)
