The only thing that goes up and never
down is time or age. With time and age, many
things change including new constructions,
modification as needed to be fittest,
destruction of unfit ones and even extinction.
All these things are under evolution.
Modern synthetic theory is most
accepted theory on organic evolution
explaining evolution based genetics,
molecular biology and other modern
branches of biology.
3. MODERN SYNTHETIC THEORY
Basis provided by :- Dobzhansky (1937) in book
Genetics and origin of species.
Designated as so by :- Huxley(1942).
Final shape by :- Muller (1949), Fisher (1958),
Wright (1968), Myer (1970), Stebbins (1976).
Five Basic Processes
Gene Mutation – It is a sudden change in
gene structure or arrangement bringing
permanent phenotypic changes in individual.
Chromosomal Aberration – It is change in
structure and number of chromosomes.
4. Recombination – It is process of exchange of
fragments between non sister chromatids of
homologous chromosomes due to crossing
Natural Selection – It is selection of
individual possessing adaptive characters by
environment as the fittest to survive.
Isolation – It is mechanism of separation of
inter breeding among conspecifics.
5. Two Accessory Factors
Genetic Drift – It is the fluctuation of gene
frequencies by chance in a small population.
It tends to eliminate less frequent alleles to
Hybridisation – In breeding among two
different mating types. ( different populations
of a species, closely related species, distant