How Is Evolution Defined In Genetic Terms?
Evolution is a process that constitutes the change in the characteristics of a species over several generations and relies on the process of natural selection.
Natural selection in evolution is the process that supports organisms to better adapt to their environment in order to survive and produce more offspring that can withstand the environment.
Evolution in terms of genetic can be defined as the change in allele frequency in a population over time from generation after generation. It’s an occurrence due to natural selection.
When scientists try to determine whether a population is evolving genetically, they study its allele frequencies.
If they see the change in allele frequencies in a population as compared to that of the ancestral population than it is sure that the population is evolving in terms of genetics.
It’s very important to note that populations, not individuals, evolve. Natural selection operates on individual organisms, but the changes it causes in allele frequency show up in the population as a whole.
Properly Defined: Evolution In Genetic Terms
Evolution is defined as the change or better adaption in the living organism to stay in its environment as compared to that of its parents. And when this evolution is defined in terms of genetics then it is termed as “Evolution in genetical terms.”
In genetic evolution, different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth. That’s actually by natural selection which helps them to better adapt to their environment.
During evolution, the individuals in a population inherit genes from their parents that bring on the necessary changes in the living body. A population is a group of individuals of the same species that mate and produce offspring.
In reproducing organisms, typical plants and animals contain two sets of genes, one contributed by each parent. An allele is a specific form of a gene that may vary from individual to individual.
Alleles are the various version of the same gene. Various alleles are formed when genes mutate or vary a bit to adapt to the environment.
Genes are responsible for the expression of traits. Alleles are responsible for the variations in which a given trait of a gene can be expressed.
Just for example: The gene for eye color can have the allele for red eye color, green eye color, or black eye color in a population. If the allele for black eye color is expressed than the organism will have black eyes. If green eye color allele is expressed than the organisms will have green eyes, and so on.
Now during the evolution of an organism, new alleles of the same gene can be developed depending on the environmental conditions. This can lead to variations meaning that the organism will differ from their parents.
It’s when the members of a population interbreed, they share a common group of genes called a gene pool. A gene pool consists of all the genes, including all the different alleles for each gene, that are present in a population.
Researchers study gene pools by examining the numbers of different alleles they contain. And, then they determine the allele frequency in and organism to see if it’s evolving genetically.
Allele frequency refers to how common an allele is in a population. It is determined by counting how many times the allele appears in the population then dividing by the total number of copies of the gene.
Simply, allele frequency is the number of times an allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene.
For example: In the mouse population, the allele frequency of the dominant B allele (black fur) is 40% and the allele frequency of the recessive b allele (brown fur) is 60%. Now, if we see that the frequency of the B allele drops to 30% we can conclude that the population of the mouse is evolving.
What’s the need to define evolution in terms of genetic?
Natural Selection that defines evolution was proposed by Charles Darwin. During the same time, Gregor Johan Mendel proposed the theory of inheritance.
Darwin showed how organisms evolve through natural selection whereas, Mendel showed how organisms inherit characters from their parents via. genes.
Darwin was unable to show how heritable traits passes from one generation to the next. And, Mendel was unable to show how inheritance aligns with natural selection.
Darwin’s natural selection was only able to show the phenotypic changes in the evolving organisms, not genotypic. In other words, natural selection acts on an organism’s outer characteristics, not directly on its genes/alleles.
Whereas, Mendel’s Law of Inheritance and Segregation showed how the alleles of the genes express itself from generation after generation.
But, nothing was able to finely define evolution in terms of genetic diversity and terms. So, there was a huge need for a conceptual definition of genetic evolution or evolution in terms of genetic terms.
Later, during the 1900s researchers rediscovered the genetic evolution and showed that heritable traits passed from one generation to the next and are controlled by genes that are carried on chromosomes.
Researchers have learned and shown how changes in genes and chromosomes generate variations. And that, natural selection acts directly only on the phenotype, not the genotype.
With the reference of both Darwin’s Natural Selection Theory and Mendel’s Law of Inheritance and Segregation, various researchers have shown how organisms vary from generation after generation.
Later on with the better discovery of genetic materials like DNA, RNA, and with the introduction of various evolutionary/ecological concepts like mutations, populations, gene pool, and allele frequencies, researchers were able to co-relate each of such discovers and concepts and drive better to the conceptual conclusion of evolution in terms of genetic diversity.
Thus, the need to define evolution in terms of genetics was solved finally. This concept is still in its ongoing research and will find better ways of understanding in the very near future.
Role of Genetics in Evolution
1. In Genetic variations: The role of genetics in evolution can be seen during genetic variation. Genetic variation is an important force in evolution as it allows natural selection to increase or decrease the frequency of alleles already in the population.
2. Populations of organisms change over generations: Due to genetic variability that occurs usually results in changing the genetic material of a population over time. This type of genetic evolution reflects the adaptations of organisms to their changing environments resulting in altered genes, novel traits, and the formation of new species.
3. In Mutations: Mutation is actually the principal reason for any type of variability. Mutation is important as the first step of evolution because it creates a new DNA sequence for a particular gene, thus creating a new allele.
4. In Recombination: Recombination describes the mixing up of two different genes located very far from each other in homologous or non-homologous chromosomes thus creating new alleles of the same genes. Recombination can create a new DNA sequence (a new allele) for a specific gene through intragenic recombination by crossing-over.
5. Explains proper inheritance: Genetic evolution shows how the organisms develop themselves to withstand the environment over time and these lead to the formation of various alleles of the same genes. Inheritance is seen when particular genetic sequences change in a population (e.g., via. mutation) and these changes are inherited across successive generations. That’s the role of genetic evolution in inheritance.
6. Explains phylogenetic & genetic relationships: Most modern systems of classification are based on evolutionary relationships and show the present-day organisms that are both phylogenetically and evolutionary related to their ancestors. Molecular biological studies can explain such a concept of genetic evolution in the phylogenetic tree very easily. For example: 90% of human genes match with cats, Cows share 80% of their genes with humans.
7. Determines Allele Frequencies: By looking at the change in allele frequencies of an organism with that of its ancestral population we can determine if that organism has evolved genetically or not. The frequencies of all the alleles of a given gene often are graphed together as an allele frequency distribution histogram. And, together with population genetics, it helps determine and study evolutionary genetics precisely.
8. Helps understand the gene pool of a population: Gene Pool is actually the stock of different genes in an interbreeding population. The composition of a population’s gene pool can change over time through genetic evolution which may be due to mutations, natural selection, and genetic drift.
9. Helps understand the genetic drift in a population: Genetic drift is the variation in the relative frequency of different genotypes in a small population, owing to the chance of disappearance of particular genes as individuals die or do not reproduce. Due to genetic drift, the allele frequencies of a population change over generations due to sampling errors thus leading to genetic evolution.