Question

What principal type of selection increases the amount of genetic variation within a population? Name two that decrease genetic diversity & explain why.

Answer 1

In the struggle for existence only those members survive which posses useful variations means nature selects fit individuals. This is called Natural Selection. Fitness is the end result of the ability to adapt and get selected by nature.

Bsed upon different organism - environment relationship. Following different kinds of natural selection have been recognised.

• Stabilising selection
• Directional selection
• Disruptive selection

These natural selections either decrease shift or increase the genetic variance of a population.

Diversifying or disruptive selection increases genetic variance when natural selection selects for two or more extreme phenotypes that each have specific advantages. In this extreme values for a trait are favored over intermediate values.

While stabilising and directional selection decrease the genetic diversity. Because:

Stabilising selection is a type of selection in which genetic diversity decreases as the population stabilizes on a particular trait value.

Directional selection is a mode of natural selection in which a single phenotype is favoured , causing the allele frequency to continuously shift in one direction which ultimatlely leads to decrease in genetic diversity.