These texts are available from the college book store. You should be able to get second hand books online. Try searching on AddALL or Campusi for prices at various online stores. Make sure you search with the correct ISBN number and for the correct edition.

Mathematical Models in Biology: An Introduction
by Elizabeth Spencer Allman
ISBN: 0521525861
Publisher: Cambridge Univ Pr
Publish Date: 11th December 2003
Evolutionary Dynamics: Exploring the Equations of Life
Martin A. Nowak
ISBN: 9780674023383
Publisher (Edition): Belknap Press (September 29, 2006)