Changes

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"a group of [[organisms]], with similar morphological, physiological, biochemical and behavioural features, which can interbreed to produce fertile offspring, and are reproductively isolated from other species." - Jones M. & Gregory J., Biology 2, 2001, Cambridge University Press, ISBN 0-521-79714-4<ref>Biology 2, Jones M. & Gregory J., 2001, Cambridge University Press, ISBN 0-521-79714-4</ref>

"a group of [[organism]]s, with similar morphological, physiological, biochemical and behavioural features, which can interbreed to produce fertile offspring, and are reproductively isolated from other species." - Jones M. & Gregory J., Biology 2, 2001, Cambridge University Press, ISBN 0-521-79714-4<ref>Biology 2, Jones M. & Gregory J., 2001, Cambridge University Press, ISBN 0-521-79714-4</ref>

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:how the body functions

:how the body functions

;biochemical features

;biochemical features

:sequence of [[bases]] in [[DNA]]

:sequence of [[base]]s in [[DNA]]

:sequence of [[amino acids]] in [[proteins]]

:sequence of [[amino acid]]s in [[protein]]s

For example, all donkeys look alike, have similar physiology and biochemistry and the same genome.  Donkeys can successfully interbreed with other donkeys to produce more fertile donkeys.  Donkeys can interbreed with a similar species; horses.  However, the offspring (called mules) are infertile and cannot reproduce with each other.  Therefore donkeys and horses are separate species.

For example, all donkeys look alike, have similar physiology and biochemistry and the same genome.  Donkeys can successfully interbreed with other donkeys to produce more fertile donkeys.  Donkeys can interbreed with a similar species; horses.  However, the offspring (called mules) are infertile and cannot reproduce with each other.  Therefore donkeys and horses are separate species.