( theory ( that ( ( ( eukaryotic organelles ) ( such ( as mitochondria ) ) ) ( evolved ( from ( ( ancient ( , ( free-living prokaryotes ) ) ) ( that ( invaded ( primitive ( eukaryotic cells ) ) ) ) ) ) ) ) ) )
(ROOT (FRAG (NP (NN theory)) (SBAR (IN that) (S (NP (NP (JJ eukaryotic) (NNS organelles)) (PP (JJ such) (IN as) (NP (NN mitochondria)))) (VP (VBD evolved) (PP (IN from) (NP (NP (JJ ancient) (, ,) (JJ free-living) (NNS prokaryotes)) (SBAR (WHNP (WDT that)) (S (VP (VBD invaded) (NP (JJ primitive) (JJ eukaryotic) (NNS cells))))))))))))
theory that eukaryotic organelles such as mitochondria evolved from ancient, free-living prokaryotes that invaded primitive eukaryotic cells
(ROOT (S (NP (NNS Prokaryotes)) (VP (VBD were) (NP (NP (DT the) (JJ first) (NN living) (NNS things)) (SBAR (S (VP (TO to) (VP (VB evolve) (PP (IN on) (NP (NN earth))))))))) (. .)))