chapter+13+resources

13.1 http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookpopecol.html

13.2 http://sciencebitz.com/?page_id=23

13.3 http://www.bcgrasslands.org/grasslands/ecosystemprocesses.htm

13.4 http://www.vtaide.com/png/foodchains.htm

13.5 http://cnx.org/content/m16470/latest/