( ( These animals ) ( ( ( ( ( have ( the advantage ) ) ( that ( ( their ( developing embryos ) ) ( can ( be ( seen ( by researchers ) ) ) ) ) ) ) , ) ( so ( that ( ( mutations ( induced ( in ( the embryos ) ) ) ) ( can ( be ( observed ( to ( determine ( how ( they ( affect ( normal development ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT These) (NNS animals)) (VP (VBP have) (NP (DT the) (NN advantage)) (SBAR (IN that) (S (NP (PRP$ their) (VBG developing) (NNS embryos)) (VP (MD can) (VP (VB be) (VP (VBN seen) (PP (IN by) (NP (NNS researchers)))))))) (, ,) (SBAR (RB so) (IN that) (S (NP (NP (NNS mutations)) (VP (VBN induced) (PP (IN in) (NP (DT the) (NNS embryos))))) (VP (MD can) (VP (VB be) (ADJP (JJ observed) (S (VP (TO to) (VP (VB determine) (SBAR (WHADVP (WRB how)) (S (NP (PRP they)) (VP (VBP affect) (NP (JJ normal) (NN development)))))))))))))) (. .)))
These animals have the advantage that their developing embryos can be seen by researchers , so that mutations induced in the embryos can be observed to determine how they affect normal development.
(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.