Evolutionary Synthesis Sanjay Kumar P Assistant Professor Department

Evolutionary Synthesis Sanjay Kumar P Assistant Professor Department of Biotechnology Hindusthan College of Arts and Science S

Maturation of Neo Darwinism into Modern Synthesis S During the later half of 19 th and early 20 th century many important ideas have been forwarded for explaining the inheritance of variation from one generation to other. S Rediscovery of Mendel’s laws by Correns, de-Vries and Tschermak in 1900 made it clear.

S The factors given to the offspring by the parents do not mix but are segregated S If more than one pair of contrasting characters are considered in the same cross, the factors responsible for these are inherited independently. S Mutation theory of evolution by Hugo de Vries states that new species arise by sudden change called mutation rather than by gradual process

S Wagner suggested the role of geographic or spatial isolation in the formation of every species, race or tribe. S Certain population geneticists realized that the actual physical struggle between animals for survival is much less important as an evolutionary force than Darwin believed. S Evolution of any given kind of Organism occurs over many generations during which individuals born and die, but the population has continuity S Thus the unit of evolution is recognized not the individual but rather a population of individuals.

S A population of a similar individuals living within a circumscribed area and interbreeding termed as a deme or a genetic population S The next larger unit of population in nature is the species composed of a series of inter-grading demes.

Relative Frequency of Genes S It remains constant from one generation to the next if the population is large. S If there is no selection for or against any specific gene or allele ie, If mating occurs random. S If no mutation occurs S If there is no migration of individuals into or out of the population

S Hrady Weinberg principle says the gene frequency is maintained in a population S A population undergoing evolution have its gene pool changing from one generation to the other S Gene pool is the sum total of allelic genes in a population

Alterations in gene pool S May occur due to Mutation S By hybridization S By natural selection

Modern Synthetic Theory S Modern understandings in cytology, population genetics, genetics etc. proposed a modern theory of Evolutionary synthesis.

Mutation S Alteration in the chemistry of Gene which results in change in its phenotype is called point mutation or gene mutation

Variation S Reshuffling of genes causes genetic variations during sexual reproduction.

Heredity S The transmission of characteristics or variations from parent to offspring

Natural selection S Natural selection brings about evolutionary change by favoring differential population of genes. S Natural selection does not produce genetic change, but once genetic change has occurred it acts to encourage some genes over others.

Isolation