( ( ( ( ( ( Animals ( with ( ( one copy ) ( of ( the ( mutant gene ) ) ) ) ) ) ( are ( physiologically normal ) ) ) , ) but ) ( ( when ( ( two ( such animals ) ) ( are mated ) ) ) ( , ( ( some ( of ( ( the embryos-embryos ) ( with ( ( two copies ) ( of ( the mutant ) ) ) ) ) ) ) ( gene-die ( in ( the womb ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (NNS Animals)) (PP (IN with) (NP (NP (CD one) (NN copy)) (PP (IN of) (NP (DT the) (JJ mutant) (NN gene)))))) (VP (VBP are) (ADJP (RB physiologically) (JJ normal)))) (, ,) (CC but) (S (SBAR (WHADVP (WRB when)) (S (NP (CD two) (JJ such) (NNS animals)) (VP (VBP are) (VP (VBN mated))))) (, ,) (NP (NP (DT some)) (PP (IN of) (NP (NP (DT the) (NNS embryos-embryos)) (PP (IN with) (NP (NP (CD two) (NNS copies)) (PP (IN of) (NP (DT the) (JJ mutant)))))))) (VP (VBP gene-die) (PP (IN in) (NP (DT the) (NN womb))))) (. .)))
Animals with one copy of the mutant gene are physiologically normal, but when two such animals are mated, some of the embryos-embryos with two copies of the mutant gene-die in the womb.
(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.