Biological species.
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<lI> Similarity between different species.
The  eastern  meadowlark  and  western  meadowlark  are similar in
appearance,  but  are  distinct  biological  species because their
<A ClAsS=WWW Href="http://www.biophile.org/songs/Aves/00PlayMe.cgi?IX=59" oNClick="popurlt('http://www.biophile.org/songs/Aves/00PlayMe.cgi?IX=59');txtcolor('species_1','gray');return false;" Id=species_1 ClAsS=WWW>songs</A>   and  other  behaviors  are  different  enough  to  prevent
interbreeding in the wild.
<lI> Diversity within a species.
Though  diverse  in  appearance,  all  humans  belong  to a single
biological  species  (Homo  sapiens),  defined  by our capacity to
interbreed and produce fertile offspring.
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   Some  species  are  able to interbreed, but if the hybrid offspring is
   <A ClAsS=MIZ Href="../../..//med/liger.html" oNClick="popurlts('../../..//med/liger.html',717,625);txtcolor('species3','gray');return false;" Id=species3 ClAsS=MIZ>sterile,</A>  the  parental  species  are  considered  separate biological
   species.
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