( ( This ( ( allows selection ) ( to ( act ( upon ( the traits ) ) ) ) ) ) ( ( these polymorphisms ) ( produce . ) ) )
(ROOT (S (S (NP (DT This)) (VP (VBZ allows) (NP (NN selection)) (S (VP (TO to) (VP (VB act) (PP (IN upon) (NP (DT the) (NNS traits)))))))) (NP (DT these) (NNS polymorphisms)) (VP (VBP produce)) (. .)))
This allows selection to act upon the traits these polymorphisms produce.
(ROOT (S (NP (JJ Natural) (NN selection)) (VP (VBZ is) (NP (NP (DT the) (NN process)) (SBAR (WHNP (WDT that)) (S (VP (VBZ allows) (NP (NNS organisms)) (PP (IN with) (NP (JJR better) (NNS traits) (S (VP (TO to) (VP (VB survive) (CC and) (VB produce))))))))))) (. .)))