ecologist

from WordNet (r) 3.0 (2006)

ecologist
    n 1: a biologist who studies the relation between organisms and
         their environment

from The Collaborative International Dictionary of English v.0.48

ecologist \ecologist\ ([-e]*k[o^]l"[-o]*j[i^]st), n.
   a biologist who studies the relation between organisms and
   their environment.
   [WordNet 1.5]