The origin and evolution of life has long been debated, and natural selection and gene drift are considered to be the primary mechanisms of evolution. Natural selection is the process by which individuals with traits that favor survival and reproduction gradually increase, while gene drift is the phenomenon by which the proportions of traits change due to chance factors. Through these mechanisms, evolution leads to biological changes such as adaptation, symbiosis, and speciation.
The question of the origin of life has been debated for a long time, and to this day, there are many different theories. The most commonly accepted theory is the mechanism proposed by Charles Darwin in the 17th century under the name “Theory of Evolution”. Although the theory has been modified and refined over the centuries, it is still considered to be the founder of evolution because he was the first to describe the core processes. So, what is evolution? Evolution is the process by which a group of organisms undergoes gradual changes through interactions within the group or with their environment, eventually resulting in changes in the characteristics of the group and the emergence of new species. In this article, we’ll cover the main mechanisms that drive evolution: natural selection and gene flow, as well as co-evolution, symbiosis, and speciation.
There are many different opinions on how evolution works. The two main ones are natural selection and gene immobilization. Natural selection, a theory popularized by Charles Darwin in his book The Origin of Species, is the interaction of a group of organisms with their environment. It is a mechanism by which individuals with traits that favor their survival or reproduction in a given environment survive and reproduce more, so that those individuals gradually become a larger part of the population and lead to the creation of new species. To explain this more concretely, just as not all humans look the same, biological populations have a variety of characteristics due to mutations. Individuals within a population compete for survival and reproduction, and those with favorable traits have an easier time surviving and reproducing. The number of individuals with favorable traits naturally increases in the next generation, and as this change accumulates, the unfavorable traits are eliminated and the favorable traits are passed on.
To illustrate this, let’s look at traits that favor survival and reproduction. A classic example of natural selection on traits that favor survival is the grayling moth, which was native to England during the industrialization of the 19th century. As industrialization made the air more polluted, the white moth became more visible to predators and nearly disappeared from cities. In rural areas, however, white moth populations were still high. An example of natural selection for traits that favor reproduction is the plumage of peacocks. The colorful plumage of male peacocks has no survival advantage and is rather heavy, making it inconvenient for them to live. Nevertheless, because females prefer colorful plumage, males have developed more colorful plumage, which is a classic example of sexual selection that increases reproductive success.
Gene floating, on the other hand, is caused by reproductive processes and other circumstances within a population rather than competition. This can be analogized to an experiment with marbles in an empty jar. If you have a jar containing white and black marbles, randomly select marbles from the first jar and repeat the process with the same color marbles in a second jar, the proportion of marbles in the second jar may be different from the first. This illustrates that even in real-world biological populations, the proportions of alleles can change due to reproduction or other factors. An extreme example of genetic immobility is the elephant seal, of which only 20 remain due to hunting in the 19th century. Because the genetic traits of the 20 surviving animals were so similar, the genetic diversity among them remains very low, even though the population has since increased significantly. In contrast to competition in natural selection, gene floating is a phenomenon in which the proportions of traits vary due to chance or external factors during reproduction.
The consequences of evolution include adaptation, symbiosis, and speciation. Adaptation is the change in a population to suit a specific environment, such as bacteria becoming resistant to antibiotics. Another example of adaptation is the concept of homologous organelles. Homologous organs are structurally similar organs that have different appearances and roles, showing that they have the same evolutionary origin. Examples include the human hand and the wings of bats. Vestigial organs are also a form of adaptation: organs that were once necessary but are no longer used. The human tailbone is an example of this.
Symbiosis is a relationship in which two groups of organisms mutually benefit. The relationship between ants and aphids is a prime example. The ants protect the aphids, and the aphids provide sugars for the ants, and vice versa.
Speciation is the separation of one species from another through evolution. There are four main ways speciation can occur. First, there is ectopic speciation, where geographically isolated populations evolve into different species over time. Second, there is migratory speciation, which occurs when parts of a population migrate to different regions. Third, there is physiological speciation, which is caused by differences in reproductive systems, and finally, there is proximate speciation, which is caused by differences in the rate of adaptation to environmental changes.
In conclusion, natural selection and gene drift are important mechanisms that drive evolution, resulting in phenomena such as adaptation, symbiosis, and speciation. Evolution is not just a past event, but an ongoing phenomenon, and its study is important not only for understanding the biological past, but also for predicting the future.
