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Darwin and Wallace's Surprising Theory: What Exactly Is Natural Selection?
In the mid-19th century, the ideas of Darwin and Wallace, two British naturalists, illuminated the scientific world like lightning. They proposed the concepts of evolution and natural selection in an attempt to explain why life adapts to its environment. This theory is not just about the change of species, but also a profound insight into how life evolves and thrives in competition.
Evolution is the change in the heritable characteristics of biological populations in successive generations. When evolutionary processes such as natural selection and genetic drift act on genetic variation, certain characteristics will become more and more common or rare from generation to generation.
The cornerstone of natural selection
Several important concepts of how natural selection works. First, there are variations in the population that affect the morphology, physiology, and behavior of organisms; second, certain characteristics can affect the ability to survive and reproduce, leading to so-called "fitness differences"; and finally, these characteristics can be passed from one generation to the next. generation.
According to the theory of natural selection, traits that adapt to the environment become more common over time. For example, if insects of a certain color are less vulnerable to predators in an environment, genes for that color are more likely to be passed on to future generations.
The process of natural selection often exploits the principle of "surplus offspring" - that is, often more offspring are produced than are actually viable, thus creating competition.
Sources of variation in evolution
One of the basic elements of evolution is the presence of genetic variation within a population. These variations arise from genetic mutations, genetic recombination during sexual reproduction, and gene flow between populations. Although the vast majority of the genome is very similar among all individuals of the same species, small differences in genetic variation can lead to significant phenotypic differences.
The role of genetic mutations
Gene mutations are changes in the DNA sequence in an organism's genome, which are the fundamental source of genetic variation in all organisms. These mutations can alter the gene's product, prevent the gene from functioning properly, or have no effect at all. While most mutations are neutral, some can confer adaptive advantages that influence an organism's evolutionary history.
Gender and genetic recombination
For organisms that reproduce asexually, genes are co-inherited because they cannot mix with genes from other organisms. However, the offspring of sexed reproduction are a random mixture of the parents' chromosomes, through independent random assignment. This not only enhances the likelihood of genetic variation but also increases the rate of evolution.
Although sexual reproduction has a certain cost, in biological evolution, the genetic diversity it brings may be crucial to the adaptation to environmental changes.
Gene flow and evolution
Gene flow is the exchange of genes between different populations, which may be a source of new variation. The movement of individuals, such as mice between inland and coastal populations, can introduce new genes and contribute to the formation of new species. In microorganisms, the more common method of gene flow is horizontal gene transfer, which will further promote the expansion of genetic diversity.
Inspiration from epigenetics
In addition to genetic mutations, there are some genetic changes that cannot be explained solely by changes in DNA sequence. Epigenetics studies mechanisms such as DNA methylation and gene silencing, which in some cases can also lead to heritable trait changes. This suggests that the process of evolution may be more complex than we thought.
The driving force of evolution
From a neo-Darwinian perspective, evolution occurs through changes in the frequencies of different genes. These changes can be caused by natural selection, genetic drift, and mutational bias. The force of natural selection works by causing individuals with adaptive traits to reproduce, making those traits more likely to appear in subsequent generations.
The evolution of living things is a long and complex process. The theories of Darwin and Wallace not only explained the adaptability of species, but also suggested the interactions between species and the diversity of ecosystems.
So when considering how our species survives and thrives in this world, we have to ask: What can we learn in this ongoing process of evolution?
