( ( ( ( ( ( Because ( ( of ( the way ) ) ( ( the eggs ) develop ) ) ) ( , ( ( parthenogenetic embryos ) ( have ( ( only ( one type ) ) ( of ( sex chromosome ) ) ) ) ) ) ) , ) and ) ( ( of ( the ( two possibilities ) ) ) ( ( only ( ZZ embryos ) ) ( can survive ) ) ) ) . )
(ROOT (S (S (SBAR (IN Because) (S (PP (IN of) (NP (DT the) (NN way))) (NP (DT the) (NNS eggs)) (VP (VBP develop)))) (, ,) (NP (JJ parthenogenetic) (NNS embryos)) (VP (VBP have) (NP (NP (RB only) (CD one) (NN type)) (PP (IN of) (NP (NN sex) (NN chromosome)))))) (, ,) (CC and) (S (PP (IN of) (NP (DT the) (CD two) (NNS possibilities))) (NP (JJ only) (NNP ZZ) (NNS embryos)) (VP (MD can) (VP (VB survive)))) (. .)))
Because of the way the eggs develop, parthenogenetic embryos have only one type of sex chromosome, and of the two possibilities only ZZ embryos can survive.
(ROOT (S (NP (NP (NNS Invertebrates)) (-LRB- -LRB-) (CC and) (NP (JJR higher) (NNS animals)) (-RRB- -RRB-)) (VP (MD can) (ADVP (RB also)) (VP (VB be) (VP (VBN placed) (PP (IN in) (NP (NP (CD one)) (PP (IN of) (NP (CD two) (NNS groups))))) (PP (VBN based) (PP (IN on) (SBAR (WHADVP (WRB how)) (S (NP (PRP they)) (VP (VBP develop) (PP (IN as) (NP (NNS embryos))))))))))) (. .)))
Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as embryos.