Question

Write a brief account on population genetics and its evolution.

 

Answer 1

Population Genetics and Evolution:

• Thus, population genetics has provided great support to the idea of organic evolution.
• Various aspects of evolution can be reviewed in terms of population genetics as follows:

Speciation:

• The process of formation of new species is called speciation Two genetically divergent populations can form new species only when they become geographically isolated from each other.
• If a large population is fragmented into two or more units which are geographically isolated from one another, each independent unit
  follows different evolutionary paths for following reasons:

1. Each isolated unit of a population may has its own type of mutation which provides raw materials for organic diversity.
2. The mutations and gene combinations which appear in different isolated population units will have different adaptive values a the new environments. 3. The organisms which originally colonize a certain geographical area and form an isolated population may not be representative of the group from which they came so that different gene frequencies exist from beginning.
4. The size of the new population may become quite small at time so that a genetic "bottle neck" is formed, from which all subsequent organisms will arise.
5. During the period of small population size, the gene frequencies will fluctuate in unpredictable directions. The fluctuationin gene frequency is called Genetic drift.

Stratification:

• When the genetic equilibrium of a natural population is dis- turbed by pressure of evolution many factors such as mutation, selection, migration, and isolation, the natural population is divided into many sub-populations.
• Each sub-population has different gene frequencies. Such population which consists of two or more sub-populations with different gene frequencies is said to be strati- fied.
• For example, the Indian population is a stratified population because it of various sub-populations, such as dravadians and aryans, etc.
  
  Population genetics has provided great help to human genetics in understanding the inheritance of various human traits in a given population. It has also helped in better understanding of organic evolution, especially evolution of man.

Population Genetics:

It is the study of genetic variation within and among populations and the evolutionary factors that explain this variation.

                                        OR

It is a field of biology which studies the genetic composition of biological populations and the changes in genetic composition which result from the operation of various factors such asnatural selection.