Changes

A '''species''' is a group of living beings or organisms having sufficient genetic similarity to be able to interbreed and produce fertile offspring.<ref>A group of organisms belong to the same biological species if they are capable of interbreeding to produce fertile offspring. [http://www.biochem.northwestern.edu/holmgren/Glossary/Definitions/Def-S/species.html Holgrem Lab], Northwestern University, Illinois </ref>

A '''species''' is a group of living beings or organisms having sufficient genetic similarity to be able to produce fertile offspring.<ref>A group of organisms belong to the same biological species if they are capable of producing fertile offspring. [http://www.biochem.northwestern.edu/holmgren/Glossary/Definitions/Def-S/species.html Holgrem Lab], Northwestern University, Illinois </ref>

For example, a [[tiger]] and a [[clam]] are different species, because they cannot mate. A [[German Shepherd]] and a [[Beagle]] can mate, because they are different breeds within one species.

For example, a [[tiger]] and a [[clam]] are different species, because they cannot produce offspring. A [[German Shepherd]] and a [[Beagle]] can produce offspring, because they are different breeds within one species.

However, the definition of "species" has changed over time and is sometimes problematic.

However, the definition of "species" has changed over time and is sometimes problematic.