The theory of evolution first formulated in Darwin's book is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits that allow them to better adapt to its environment, survive and have more offspring.
Ernst Mayr divided Darwin's theory into 5 unique parts.
Ernst Mayr divided Darwin's theory into 5 unique parts.Evolution as such
Along with Buffon and Lamarck, Darwin supported the ability of species to change over time.
Common Descent
Darwin felt that all of the diversity of life on earth emerged out of the evolution from one or a few common ancestors.
Gradualism
While Lamarck felt that species-wide change could take place within the span of a few generations, Darwin felt evolution was a much slower process, taking place in innumerable small steps.
Population Speciation
This portion of Darwin's theory states that within a population, change in a species occurs as the balance of hereditary characteristics shifts across that population. This differs from Lamarck's idea that each individual in the population must undergo the same change. According to Lamarck, all giraffes living under tall trees would develop long necks. According to Darwin, some would randomly be born with long necks, this hereditary trait would gradually spread throughout the population.
Natural selection
Natural selection is often called the most unique part of Darwin's theory. Competition had been thought of as a reason that a given species might succeed or go extinct, but Darwin extended the understanding to change within a species. To continue the example of giraffes: when a giraffe is born with a longer neck than its fellows, it gains an advantage because it is able to reach more food. The long-neck giraffe is therefore stronger, lives longer, and more likely to have offspring. These offspring are born with the same long neck as their parent, though some might have even longer necks.
Returning to the example in the figure, in the first generation the application of the pesticide causes the death of most of the non-resistant insects: only those resistant to the pesticide survive. These insects reproduce and maintain their resistence so that the second generation will be more resistant than the first. So we have Natural selection, speciation, gradualism and evolution in act all together.
