According to Darwin's theory of evolution, new species evolved as a result of natural selection.
Explanation:
Darwin proposed that speciation could readily occur through the prolonged action of Natural selection.
Natural selection allows the 'survival of the fittest' i.e. a more fit organism will have a better chance of survival than the less fit one.
The result of Natural selection could be positive,negative or balancing.
Evolutionary process in which the genetic changes confer a higher fitness to increase frequency of the organism over time in population is called positive selection.
Evolutionary process in which genetic changes decreases the organism's fitness resulting in its disappearance from the population is called Negative selection.
It may happen that a mutation benefits hetero-zygotes but not homo-zygotes and alleles maintain a intermediate frequency in population.This evolutionary process is called balancing selection.
