Question

Which one is raw material for evolutionary change?
A. Reshuffling of gene combinations
B. Variability of gene pool
C. Unrestricted gene flow
D. Balancing selection

Answer 1

Hint: Genetic variation is a crucial force in evolution because it allows activity to extend or decrease frequency of alleles already within the population. Genetic variation is advantageous to a population because it enables some individuals to adapt to the environment while maintaining the survival of the population.

Complete Answer:
Gene flow, also called gene migration, the introduction of genetic material (by interbreeding) from one population of a species to a different, thereby changing the composition of the gene pool of the receiving population. The introduction of recent alleles through gene flow increases variability within the population and makes possible new combinations of traits. In humans gene flow usually comes about through the particular migration of human populations, either voluntary or forced.

Genetic variation could be a measure of the genetic differences that exist within a population. The genetic variation of a complete species is usually called genetic diversity. Genetic variations are the differences in DNA segments or genes between individuals and every variation of a gene is called an allele. For instance, a population with many alternative alleles at one chromosome locus encompasses a high amount of genetic variation.

Genetic variation is caused by:
• Mutation
• Random mating between organisms
• Random fertilization
• Crossing over or recombination

The last three of those factors reshuffle alleles within a population, giving offspring combinations which differ from their parents and from others.

Evolution and Adaptation to the Environment: Variation allows some individuals within a population to adapt to the changing environment. As natural processes act directly only on phenotypes, more genetic variation within a population usually enables more phenotypic variation. Some new alleles increase an organism’s ability to survive and reproduce, which ensures survival of allele within the population. Other new alleles could also be immediately detrimental and organisms carrying these new mutations die out. Genetic variation is advantageous because it enables some individuals and, therefore, a population, to survive despite a changing environment.

Geographic Variation: Some species display geographic variation moreover as variation within a population. Geographic variation, within the genetic makeup of various populations, occurs when populations are geographically separated by environmental barriers or after they are under selection pressures from a special environment. One example of geographic variation are: graded changes during a character down a geographic axis.

Therefore, the correct option is B, variability of gene pool.

Note: Sources of Genetic Variation: Gene duplication, mutation, or other processes can produce new genes and alleles and increase genetic variation. New genetic variations are created within generations hence a population with rapid reproduction rates have high genetic variation. However, existing genes are often arranged in new ways from chromosomal organic process and recombination in reproduction. Overall, the most sources of genetic variation are the formation of recent alleles, the altering of gene number or position, rapid reproduction, and amphimixis.