Darwin’s Theory of Natural Selection

Darwin’s theory of Natural selection still holds ground but was modified with progress in genetics and developed into the Modern synthetic theory which is regarded as the most valid theory of evolution.

Darwin’s Theory of Natural Selection

He suggested that all kind of organisms are related through ancestry and a mechanism for evolution and named it natural selection.

According to Darwin, organisms produce more offspring than can survive. Because environmental resources are limited there ensues struggle for existence. Organisms with advantageous variations are protected and allowed to reproduce while the disadvantageous variants are eliminated from nature. This is what was termed natural selection by Darwin.

According to Darwin when the environment changes, new adaptations get selected in nature and after many generations sufficient characteristics will have been changed so as to alter the species into a new one (origin of species).

Darwin talked about variation but did not know about the sources of variation. With progress in genetics the sources of variation were discovered and Darwin’s original theory of Natural Selection modified. This new theory was termed Neo-Darwinism or Modern Synthetic Theory.

Modern Scientific Theory of Evolution

According to this theory:

  1. The unit of evolution is population which has its own gene pool. Gene pool is the group of all different genes of a population.
  2. Heritable genetic changes appear in the individuals of a population. These heritable changes or variations occur due to small mutations in the genes or in the chromosomes and their recombinations.
  3. Natural selection selects the variations which helps in adapting to the environment.
  4. A change in the genetic constitution of a population selected by natural selection is responsible for evolution of a new species, since through interaction of variation and Natural Selection more offsprings with favourable genetic changes are born. This is called differential reproduction.
  5. Once evolved, Reproductive Isolation helps in keeping species distinct.