( ( Reproductive isolation ) ( ( ( is ( ( a collection ) ( of ( mechanisms ( , ( behaviors ( , ( and ( physiological processes ) ) ) ) ) ) ) ) ) ( ( ( ( that ( ( ( prevent ( ( the members ) ( of ( ( two ( different species ) ) ( that cross ) ) ) ) ) or ) ( mate ( from ( producing offspring ) ) ) ) ) , ) or ) ( which ( ensure ( that ( ( ( any offspring ) ( that ( may ( be produced ) ) ) ) ( ( is not ) fertile ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Reproductive) (NN isolation)) (VP (VBZ is) (NP (NP (DT a) (NN collection)) (PP (IN of) (NP (NNS mechanisms) (, ,) (NNS behaviors) (, ,) (CC and) (NN physiological) (NNS processes)))) (SBAR (SBAR (WHNP (WDT that)) (S (VP (VP (VB prevent) (NP (NP (DT the) (NNS members)) (PP (IN of) (NP (NP (CD two) (JJ different) (NNS species)) (SBAR (WHNP (WDT that)) (S (VP (VBP cross)))))))) (CC or) (VP (VB mate) (PP (IN from) (S (VP (VBG producing) (NP (NN offspring))))))))) (, ,) (CC or) (SBAR (WHNP (WDT which)) (S (VP (VB ensure) (SBAR (IN that) (S (NP (NP (DT any) (NN offspring)) (SBAR (WHNP (WDT that)) (S (VP (MD may) (VP (VB be) (VP (VBN produced))))))) (VP (VBZ is) (RB not) (ADJP (JJ fertile)))))))))) (. .)))
Reproductive isolation is a collection of mechanisms, behaviors, and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced is not fertile.
(ROOT (S (SBAR (IN If) (S (NP (CD two) (NNS populations)) (VP (VBP do) (RB not) (VP (VB mate) (CC and) (VB produce) (NP (ADJP (JJ fertile)) (NN offspring)))))) (, ,) (NP (JJ separate) (NNS species)) (VP (VBP result)) (. .)))