The Collaborative International Dictionary of English v.0.48:

Biogeography \Bi`o*ge*og"ra*phy\, n. [Gr. bi`os life + E.
   geography.]
   The branch of biology which deals with the geographical
   distribution of animals and plants. It includes both
   zo["o]geography and phytogeography. -- Bi`o*ge`o*graph"ic,
   a. -- Bi`o*ge`o*graph"ic*al*ly, adv.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

biogeography
    n 1: dealing with the geographical distribution of animals and
         plants