General purpose of this lecture is to present on Natural Selection Model. It is a tutorial based lecture. Natural selection is a key mechanism of evolution, and over time changes the frequency of many traits within a population. It is the gradual, non-random, process by which biological traits become either more or less common in a population as a function of differential survival and reproduction of their bearers. Here briefly focus on what did the individuals in our population compete for in the struggle to survive and which individuals were naturally selected.