( There ( ( have ( ( been ( ( five ( major extinctions ) ) ( of ( ( life forms ) ( on ( the earth ) ) ) ) ) ) ( since ( life ( ( arose over ) ( ( ( a billion ) years ) ago ) ) ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBP have) (VP (VBN been) (NP (NP (CD five) (JJ major) (NNS extinctions)) (PP (IN of) (NP (NP (NN life) (NNS forms)) (PP (IN on) (NP (DT the) (NN earth)))))) (SBAR (IN since) (S (NP (NN life)) (VP (VBD arose) (PRT (RP over)) (ADVP (NP (QP (DT a) (CD billion)) (NNS years)) (RB ago))))))) (. .)))
There have been five major extinctions of life forms on the earth since life arose over a billion years ago.
(ROOT (S (NP (EX There)) (VP (VBP have) (VP (VBN been) (NP (CD five) (JJ major) (JJ massive) (NNS extinctions)) (SBAR (IN since) (S (NP (NN life)) (VP (VBD began) (PP (IN on) (NP (NN earth)))))))) (. .)))