( Zygotes ( ( are ( produced ( by ( ( ( fertilization ( between ( ( ( ( ( two ( haploid cells ) ) , ) ( the ovum ) ) and ) ( the ( sperm cells ) ) ) ) ) , ) ( which ( make ( a ( diploid cell ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Zygotes)) (VP (VBP are) (VP (VBN produced) (PP (IN by) (NP (NP (NN fertilization)) (PP (IN between) (NP (NP (CD two) (JJ haploid) (NNS cells)) (, ,) (NP (DT the) (NN ovum)) (CC and) (NP (DT the) (NN sperm) (NNS cells)))) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBP make) (NP (DT a) (JJ diploid) (NN cell))))))))) (. .)))
Zygotes are produced by fertilization between two haploid            cells, the ovum and the sperm cells, which make a diploid cell.
(ROOT (S (SBAR (IN While) (S (NP (NNS spermatogenesis)) (VP (VBZ produces) (NP (CD four) (JJ haploid) (NN sperm) (NNS cells))))) (, ,) (NP (NNS oogenesis)) (VP (VBZ produces) (NP (CD one) (JJ mature) (NN ovum))) (. .)))