ryman, who prefers getting seed from large body of the same variety that results in decreasing the intercrossing with other varieties. Isolation is a method that acts efficiently in checking the immigration of better-adapted organisms, after an alteration in the climate. There are more chances of modification and of spreading widely on a large area then on a small area. Darwin presents his theory of Extinction as: each favored and selected form increases in number, the less favored form decreases and eventually becomes rare. As he explains "rarity is the precursor of extinction."(153) Because of the small number of the original form, there is a smaller chance of adapting, which ultimately leads to extinction. Darwin gives examples of new breeds of cattle, sheep and other animals that replace the older and substandard kind. To be precise, he presents example of ancient black cattle, which was displaced by the longhorns. Darwin gives importance to divergence of character within specie. He explains that even a slight difference in the characteristic of specie could make a gigantic difference. He presents with an example of some men in early period, which preferred fleeter horse, but the others liked bulky horses. The difference becomes greater and greater forming two sub-breeds. The favorable variation slowly becomes so different that it would be a lot different from the original. Charles Darwin has explained his theory of natural selection in a very straightforward way. He went by stating theories and giving general life examples, to help understand them better. Darwin's theory is written step-by-step giving a very good explanation of evolution....
