In addition, g represents the "time gap" between birth and adulthood. The larger g is, the faster the children will replenish the adult population. The effect of this is to squeeze the graph closer together in the horizontal direction.
The variable n, as it is increased, squeezes the graph together in the vertical direction. The y population will be dying off faster.
Note that g does not affect the a-coordinate of the equilibrium, though it affects the width of the graph in the a-direction, and that n does not affect the y-coordinate of the equilibrium, though it affects the height of the graph in the y-direction.