Let N(t) be the number of individuals in a population at time t, and let b and d be the average per capita birth rate and death rate, respectively. In a short time Δt, the nu...Let N(t) be the number of individuals in a population at time t, and let b and d be the average per capita birth rate and death rate, respectively. In a short time Δt, the number of births in the population is bΔtN, and the number of deaths is dΔtN. N(t+Δt)=N(t)+bΔtN(t)−dΔtN(t)