Describe Modern synthetic theory of Evolution.

Explanation

1. The present concept of evolution is a modified form of Darwin.s theory of natural selection and often called Neo-Darwinism. According to tit only genetic variations (mutations) are inherited and not all variations as held by Drawin.
2. The synthetic theory of evolution is the result of the work of a number of scientists namely T. Dobzhansky, R.A. Fisher, J.B.S. Haldane, Swell Wright and Emst Mayu. It includes the following fractors -
(A) Genetic Variation in Population.
It is the population that evolves and not its individual members. The individual.s role in the evolutionary process is to pass its genetic variation to its offsprings. Evolution occurs through the accumulation of genetic variations in population over long periods of time. The change in genes occur in the following ways -
(i) Mutation. Sudden change in the genetic material is called mutation. It is due to gene mitation and chromosomal aberration.
(ii) Genetic Drift. This term refers to the elimination of genies of certain traits when a section of population migrates or dies of natural calamity. It changes the gene frequency of the remaining population.
(iii) Migration. Migration of individuals from one population to another is also a factor for evolution. (iv) Non-random Mating. It also contributes to the genetic variation.
(v) Gene Recombination. Genetic variation also arises by crossing over of chromosomes, independent assortment of chromosomes during meiosis and random coming together of maternal and parental chromosomes at fertilization.
(vi) Hybridization. It is a method of mixing the genes of two population.
(B) Natural Selection.
It is differential reproduction which means some members of a population have traits (genes) that enable thein to grow up and reproduce at higher rate and leave more surviving offspring in the next generation than others. If differential reproduction continues for many generations, genes of the individuals which produce more offspring will become predominant in the gene pool (total gene context of a whole species) of the population.
(C ) Reproductive Isolation.
The population with different genotype appearing in them must be isolated so that differences may accumulate to form a new species.