We study the classification and evolution of bifurcation curves of positive solutions of the one-dimensional Dirichlet-Neumann problem with a specific cubic nonlinearity given by u (x) + λ(−εu 3 + u 2 + u + 1) = 0, 0 < x < 1, u(0) = 0, u (1) = −c < 0, where 1/10 ≤ ε ≤ 1/5. It is interesting to find that the evolution of bifurcation curves is not completely identical with that for the one-dimensional perturbed Gelfand equations, even though it is the same for these two problems with zero Dirichlet boundary conditions. In fact, we prove that there exist a positive number ε * (≈ 0.178) and three nonnegative numbers c 0 (ε) < c 1 (ε) < c 2 (ε) defined on [1/10, 1/5] with c 0 = 0 if 1/10 < ε ≤ ε * and c 0 > 0 if ε * < ε ≤ 1/5, such that, on the (λ, u ∞)-plane, (i) when 0 < c ≤ c 0 (ε) and c ≥ c 2 (ε), the bifurcation curve is strictly increasing; (ii) when c 0 (ε) < c < c 1 (ε), the bifurcation curve is S-shaped; (iii) when c 1 (ε) ≤ c < c 2 (ε), the bifurcation curve is ⊂-shaped.