( therefore ( , ( ( ( two ( sexually ( reproducing organisms ) ) ) ( of ( the ( same species ) ) ) ) ( ( ( can generally ) ( ( ( mate and ) produce ) ( ( ( fertile and ) viable ) offspring ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB therefore)) (, ,) (NP (NP (CD two) (RB sexually) (JJ reproducing) (NNS organisms)) (PP (IN of) (NP (DT the) (JJ same) (NN species)))) (VP (MD can) (ADVP (RB generally)) (VP (VB mate) (CC and) (VB produce) (NP (ADJP (JJ fertile) (CC and) (JJ viable)) (NN offspring)))) (. .)))
therefore, two sexually reproducing organisms of the same species can generally mate and produce fertile and viable offspring.
(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)) (. .)))