Question

Which of the evolutionary forces do you think would have the biggest impact on population change?  Why? In your answer provide one example (real or hypothetical)

Answer 1

The evolution of a population is depend on various factors.evolution not occurred due to a single phenomenon lots of events accounts for a population change.Evolution concerns how species changes over the time that means evolution works was based on the inheritance of the acquired characteristics.Natural selection,genetic drift and  gene flow causes variation in the allele frequencies over time.When one or more of these forces are acting in a population, the population violates the Hardy-Weinberg assumptions, and evolution occurs.Gene mutations involve changes in the sequence of nucleotide bases leads to producing a new sequence with some more adaptation.Let us take each characteristics features in detailed,

Natural selection - Charles Darwin proposed the theory of evolution by natural selection,Darwin had formulated his theory of natural selection,better adapted organism would acquire more resources and leave more offspring. nature selects individuals with traits that allow them flourish and reproduce. This idea came to be known as survival of fittest,this leads to the adaptations of new species. Example: one of best known examples of natural selection is the color changes that occurred in certain populations of peppered moth Biston betularia , in industrial regions of Europe due to industrial melanism. Natural selection can follow four different pattern directional,stabilizing,balancing and disruptive. Given enough time disruptive selection  can lead to speciation. An classic example for balancing selection(in here two or more allele are kept in balance,it will not favor one particular allele in a population) is the heterozygote advantage involves the sickle-cell of the human -globin gene.However in areas where malaria is endemic,the heterozygote has the highest level of fitness.

Genetic drift and Gene flow- The Hardy-Weinberg equation predicts unchanging allele and genotype frequencies in a population.in a such a population evolution will not occur.If population violates from H & W equilibrium evolution takes place.Genetic drift refers to random changes in allele frequencies over time.In a small population individual fails to mate possesses a rare gene so that will not passed in to the next generation and resulting loss of genetic diversity from the population.This leads to genetic drift.Such isolated populations will lose a percentage of their original diversity time approximately at rate of 1 / 2N per generation ,where N=population size due to genetic drift population loss genetic diversity in each generation so it will lead to evolutionary changes.

Gene flow is the movement of gens in to and outside of a population, this is due to migration of individual organism that reproduce in new population or movement of gametes.With out genetic drift and natural selection gene flow will not produce any genetic diversity.If restricted gene flow leads to natural selection and drift ,it will lead to speciation and evolution.

We can conclude evolution may due to natural selection ,genetic drift and gene flow between populations.One of the important evolutionary force is natural selection leads to speciation. It will change allele frequency that is the only mechanism that promote the adaptation of organisms to their changing environmental conditions.