In this blog post, we will look at how natural selection and gene drift cause evolution and, as a result, induce adaptation and speciation.
The question of the origin of life has been a topic of debate for a long time, and various opinions are still being presented today. The most commonly accepted theory is the mechanism proposed by Charles Darwin in the 17th century under the name “Theory of Evolution.” Of course, many parts have been modified and supplemented over the past few hundred years, and there are some differences from the theory that was first proposed, but Charles Darwin is still considered the founder of the theory of evolution because he was the first to propose the core process. So, what is the definition of evolution? Evolution is the process by which a group of organisms undergoes gradual changes through interactions within the group or with the surrounding environment, eventually changing the characteristics of the group and resulting in the appearance of a new species. In this article, we will discuss natural selection and gene drift, which are the representative mechanisms that cause evolution, as well as co-evolution, symbiosis, and speciation that appear as a result of evolution.
There are various opinions on how evolution occurs. The most representative of these are natural selection and gene drift. First, natural selection is a theory widely known through Charles Darwin’s book “On the Origin of Species,” and it occurs through the interaction between a group of living organisms and their surrounding environment. This is a mechanism in which individuals with traits that are advantageous for surviving or reproducing in a given environment survive and reproduce more, and as a result, those individuals with those traits gradually account for a large proportion of the population and lead to the birth of a new species. To explain this in more detail, if we take a human population as an example, just as not all humans are the same, biological populations also have various traits due to mutations and other factors. Individuals within a group compete for survival and reproduction, and individuals with advantageous traits in this competition survive and reproduce more easily. Therefore, in the next generation, the number of individuals with advantageous traits naturally increases, and as this change accumulates, unfavorable traits are eliminated and only advantageous traits continue to be passed on.
Let’s take a look at examples of traits that are beneficial for survival and reproduction. A prime example of natural selection based on traits that are beneficial for survival is the grey-backed moth that inhabited England during the industrialization of the 19th century. As industrialization caused the air to become cloudy, white moths became more visible to predators and almost disappeared from the city. On the other hand, the white moth population was still high in rural areas. An example of natural selection based on characteristics that are favorable for reproduction is the peacock’s feathers. The colorful feathers of male peacocks not only do not provide any particular advantage for survival, but are also heavy and cause inconvenience in daily life. Nevertheless, because female peacocks prefer flashy feathers, male peacocks have become more flashy, which is a typical example of sexual selection that increases the success rate of reproduction.
On the other hand, genetic drift occurs due to the reproduction process and other situations within the group rather than competition. This can be compared to an experiment in which a bead is placed in an empty bottle. Suppose there are two jars containing white and black marbles. If you randomly select a marble from the first jar and put the same color marble in the second jar, the ratio of the marbles in the second jar may be different from the first jar. This explains that the ratio of the alleles can change due to the reproduction process or other factors in the actual population of organisms. The extreme example of genetic drift is the 20 elephants left in the world due to hunting in the 19th century. Since the genetic characteristics of the 20 surviving elephants were very similar, the genetic diversity among them remains very low, even though the population has increased significantly since then. Unlike competition in natural selection, genetic drift is a phenomenon in which the ratio of traits varies depending on chance or external factors in the reproduction process.
The results of evolution include adaptation, symbiosis, and speciation. Adaptation is a change in a group to suit a specific environment, an example of which is bacteria that are resistant to antibiotics. The concept of homologous organs is also evidence of adaptation. Homologous organs are structurally similar organs that have different appearances and roles, but they show that they have the same evolutionary origin. The human hand and bat wings are representative examples. 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 benefit from each other. The relationship between ants and aphids is a typical example. Ants protect aphids, and aphids provide ants with sugar, helping each other.
Speciation is a phenomenon in which one species is separated into another species through evolution. Speciation is divided into four categories. First, there is isolating speciation, in which geographically isolated groups evolve into different species over a long period of time. Second, there is mobile speciation, which occurs when part of a group migrates to another area. Third, there is physiological speciation, which occurs due to differences in reproductive organs. Finally, there is microevolutionary speciation, which occurs due to differences in the rate of adaptation to environmental changes.
In conclusion, natural selection and gene drift are important mechanisms that cause evolution, and as a result, phenomena such as adaptation, symbiosis, and speciation occur. Evolution is not only a phenomenon that occurred in the past, but also continues to occur today, and research on it plays an important role in predicting the future, not just in understanding the biological past.
