 Suppose firstly that \(w_{11} \gt w_{12} \gt w_{22}\), i.e., the \(A_1 A_1\) homozygote is fitter than the \(A_1 A_2\) heterozygote, which in turn is fitter than the \(A_2 A_2\) homozygote. By inspection of equation (2), we can see that \(\Delta p\) must be positive (so long as neither \(p\) nor \(q\) is zero). So in each generation, the frequency of the \(A_1\) allele will be greater than in the previous generation, until it eventually reaches fixation. Once the \(A_1\) allele reaches fixation, i.e., \(p = 1\) and \(q = 0\), no further evolutionary change will occur, for if \(p = 1\) then \(\Delta p = 0\).  This makes good sense intuitively: since the \(A_1\) allele confers a fitness advantage on organisms that carry it, its relative frequency in the population will increase from generation to generation until it is fixed.