  Many natural populations are well modelled through time-inhomogeneous
stochastic processes. Such processes have been analysed in the physical
sciences using a method based on Lie algebras, but this methodology is not
widely used for models with ecological, medical and social applications. This
paper presents the Lie algebraic method, and applies it to three biologically
well motivated examples. The result of this is a solution form that is often
highly computationally advantageous.
