Five forces of evolution
Evolution means changes in gene or allele frequencies within a population over generations and these changes lead to different genetic makeup of species.
Five forces of evolution includes:
1. Natural Selection
2. Genetic Drift
4. Gene Flow.
5. Non-Random Mating
1. Natural selection
Evolution which is due to natural selection depends on fitness of individuals within a population. Individuals who are more fit will have more survival rate in given environment than other members of the population. As they are better to survive and thus will reproduce more offsprings as compared to other members of the population.
Giraffes with longer necks get more food during a drought as compared to shorter neck giraffes. The taller giraffes produce offsprings and this tall characteristics gene is passed on over generations and short neck giraffes died because of scarcity of food during drought.
2. Genetic drift
Evolution because of genetic drift is chance events due to sampling error. It randomly select alleles to pass on to next generations.
Black eyes mother and blue eyes father may have children with black or blue eyes. If black eyes is the dominant allele then chances of children having black eyes is more.
It is defined as “error” during copying of DNA. All mutations do not leads to evolution and it depends on amount of DNA and the type of cell affected by mutation. Mutations can be harmful or beneficial.
Beneficial mutation: resistance to malaria
In humans, evolutionary change is the mutation in hemoglobin. Mutated hemoglobin such as HbS makes red blood cells sickle-shaped or curved-shape. If there is mutation in one copy then it leads to resistance to malaria. But with two copies, it leads to illness called as sickle-cell anemia.
4. Gene flow
It is defined as flow or movement of genes out or in of a population.
A dark skin man moves to another place where people have light skin. The offsprings reproduced show evidence of flow of gene as some children are born with dark skin.
5. Non-random mating
It is defined as selection of mates and genes that are best are passed on over generations.
Females from one organisms do not mate with male from different organisms. Their chouce of mating depends on physical traits or their behavior.
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