v The synthetic theory is a
modern theory of Evolution. It explains about the origin of new species and the
v The arrival of modern
synthetic theory was due to the lack of concrete idea on Evolution. Previously,
the Lamarckian concept was objected and the Darwinism didn’t provide proper
explanation on origin and pattern inheritance among the organisms. Hence in order
to find a solution Modern Synthetic Theory was proposed.
v It combines the work of
Darwin and Mendel. The scientists who have contributed to the development of
theory were T. Dobzhansky, Ernst Mayr, Huxley, Simpson, G.L. Stebbins, R.A. Fisher,
J.B.S. Haldane, Sewall Wright, etc. The major concepts of Evolution according
to modern synthetic theory were
Ø Genetic variation
Ø Natural selection
v Genetic Variation is the
raw material for Evolution. It is the variation in the genes among the organisms.
A group of closely related organisms interbreeding among themselves will form
the Genetic population. According to hardy Weinberg, the gene frequency will
not change when the population is large, random mating, absence of mutation and
migration. The genetic variation in a population is influenced by the following
Ø Mutation-sudden change in
the genes. As a result of mutation new characters will be obtained.
aberrations-the change in the chromosome.
results in the production of new traits which is not present in the parents.
between different gene populations resulting in the production of hybrids.
Ø Migration-Movement of
organism resulting in gene flow.
Ø Genetic Drift-The slow
change in the genetic frequency of an organism.
v Natural Selection-The
nature selects the organism which is having the desirable characters. The
organisms will try to adapt themselves according to the environment. The
organism which is successful will be able mate and pass on its characters to
the next generation.
v Heredity-the passing of
characters from parents to offspring. It acts as a major Evolutionary force.
v Isolation-The separation
of the organisms by means of geographical or reproductive barriers. The isolated
organism will evolve into a different species as a result of evolution for a
longer period of time. After a few course of time, they will become new
species. Thus, isolation helps in the formation of new species. Geographic
Isolation results in allopatric speciation. Reproductive isolation results in
Thus, the modern synthetic theory
plays an important role in tracing the Evolutionary process.