Guide to learning about Population biology / ecology / dynamics for a non-Biologist
There are three seminal works that will give you an excellent grounding in the study of dynamical systems in population biology. 

The first details the foundations of population genetics:

Crow, James F., and Motoo Kimura. An introduction to population genetics theory. (1970).

The second deals with population ecology:

Maynard-Smith, John. Models in ecology. CUP Archive, 1978.

Finally, the field of evolutionary game theory has recently embraced a dynamical systems approach to studying populations under the guise of a new theoretical framework known simply as evolutionary dynamics:

Nowak, Martin A. Evolutionary dynamics. Harvard University Press, 2006.

I would probably read these in reverse order. The introduction to Maynard Smith's book has a nice discussion about some of the interrelations between population genetics and population ecology. Most of the original work was done by Fisher, but you don't want to read his stuff - it's famously inaccessible. 

It is probably worth me telling you that a lot of mathematical biologists don't actually use dynamical systems approaches in their work. Instead, they favour optimisation models. A balanced discussion about the benefits of this approach, and some of the limitations of the dynamical systems approach can be found in these papers: 

Smith, J. Maynard. "Optimization theory in evolution." Annual Review of Ecology and Systematics 9 (1978): 31-56.

Parker, Geoffrey A., and J. Maynard Smith. "Optimality theory in evolutionary biology." Nature 348.6296 (1990): 27-33.

As it happens, my soon to be submitted doctoral thesis is on dynamical systems in biology. Hopefully one day I will be able to add my own book to this list :)