The correct option is A
Charles Darwin is the father of evolution. He believed that evolution is a gradual process and new species evolve by natural selection.
Natural selection is a process in which heritable variations enabling better survival are enabled to reproduce and leave a greater number of offspring.
But Darwin’s theory had some shortcomings which were addressed by certain scientists like Dobzhansky, Fisher, Ernst Mayr, Stebbins, Haldane and Wright. They proposed the modern synthetic theory of evolution.
The modern synthetic theory of evolution or Neo-Darwinism, is an improvement of Darwin’s theory of natural selection. It is a combination of ideas from Darwin's theory of natural selection, mutation theory and Mendel’s principles of heredity. It states that genetic variations (mutations) occurring in the germ cells are inherited, not all variations as stated by Darwin.
According to this concept, formation of a new species (speciation) is the result of the following factors:
- Variations in the gene pool of a population are introduced by mutations, genetic recombination, change in chromosome number or structure, hybridisation or migration, etc.
- Only variations in the genome of germinal or reproductive cells of an organism can be passed onto the future generation.
- Natural selection of genetic variations allows individuals with advantageous variations to survive, reach maturity and reproduce to contribute genes in the gene pool (differential reproduction).
- Isolation or separation of a segment of a population from the rest helps to accumulate specific variations in a group of individuals of a population or in different populations of a species.
- The gene pool of an isolated population gradually changes and fails to interbreed with the parent population. Thus, a new species is formed.
Thus, only statement II is correct while statements I, III and IV are incorrect.