( Mutations ( ( are ( ( essential ( for evolution ) ) ( to occur ) ) ) . ) )
(ROOT (S (NP (NNS Mutations)) (VP (VBP are) (ADJP (JJ essential) (PP (IN for) (NP (NN evolution))) (S (VP (TO to) (VP (VB occur)))))) (. .)))
Mutations are essential for evolution to  occur.
(ROOT (S (NP (NNP Mutation)) (VP (VBZ is) (ADJP (JJ essential) (PP (IN in) (NP (NP (NN order)) (PP (IN for) (NP (NN evolution)))))) (S (VP (TO to) (VP (VB occur) (SBAR (IN because) (S (NP (PRP it)) (VP (VBZ increases) (S (NP (NP (JJ genetic) (NN variation)) (CC and) (NP (NP (DT the) (NN potential)) (PP (IN for) (NP (NNS individuals))))) (VP (TO to) (VP (VB differ))))))))))) (. .)))