DARWIN’S THEORY AND MODERN THEORIES OF ORGANIC EVOLUTION

Charles Darwin, a British biologist, in 1859 propounded a theory of organic evolution by Natural Selection leading to the origin of species.

His theory of natural selection is as follows:

1) Overproduction: All living organisms produce more offspring than can survive.

 

2) Struggle for existence: Due to overproduction of offspring, there is a constant struggle (competition) for existence among the offspring.

 

3) Offspring show variations: No two individuals are exactly the same.

 

4) Adaptive characteristics: Some of the offspring are well adapted (fitted) to survive the competition than others.

 

5) Inheritance of adaptive characteristics: The well adapted ones (or the fittest) will transmit such variations to their offspring. Those with poor adaptations will die off.

 

6) Development of new species: An accumulation of favourable variations will in a long time lead to a divergence (spread) from the original stock resulting in the formation of new species.

 

Modern theories of organic evolution

The theory of organic evolution as stated by Darwin has been modified. The modern theories are now based on genetics, ecology, cytology, palaeontology, physiology, anatomy and embryology.