( ( During ( sexual reproduction ) ) ( , ( ( a sperm ) ( ( fertilizes ( ( an ( egg ( ( cell or ) ovum ) ) ) ( to ( form ( a zygote ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN During) (NP (JJ sexual) (NN reproduction))) (, ,) (NP (DT a) (NN sperm)) (VP (VBZ fertilizes) (S (NP (DT an) (NN egg) (NN cell) (CC or) (NN ovum)) (VP (TO to) (VP (VB form) (NP (DT a) (NN zygote)))))) (. .)))
During sexual reproduction, a sperm fertilizes an egg cell or ovum to form a zygote .
(ROOT (S (NP (NP (JJ Sexual) (NN reproduction)) (, ,) (PP (IN in) (NP (NN general))) (, ,)) (VP (VBZ relies) (PP (IN on) (NP (NP (NNS sets)) (PP (IN of) (NP (NP (NNS cells)) (SBAR (WHNP (WDT that)) (S (VP (VBP are) (NP (NP (NNS precursors)) (PP (IN for) (NP (NNS eggs) (CC and) (NN sperm)))))))))))) (. .)))