Evolution is a gradual change in inherited characters of organisms over a successive generation and thereby generating variations at each level of biological organization. Darwinism explains the process of evolution by means of natural selection which in turn refers to the unequal ability of individuals to survive and reproduce based on suitability of their inherited characters to prevailing environmental conditions. Lamarkism explains evolution as an inheritance of acquired characters under influence of needs as posed as changing environmental conditions. Thus, the correct answer is option B.