( ( A ( facultative anaerobe ) ) ( ( is ( ( an organism ) ( that ( ( ( makes ATP ) ( by ( aerobic respiration ) ) ) ( if ( oxygen ( ( ( ( is present ) , ) but ) ( is ( capable ( of ( ( switching ( to ( ( ( fermentation or ) anaerobic ) respiration ) ) ) ( if ( oxygen ( is absent ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (JJ facultative) (NN anaerobe)) (VP (VBZ is) (NP (NP (DT an) (NN organism)) (SBAR (WHNP (WDT that)) (S (VP (VBZ makes) (NP (NNP ATP)) (PP (IN by) (NP (JJ aerobic) (NN respiration))) (SBAR (IN if) (S (NP (NN oxygen)) (VP (VP (VBZ is) (ADJP (JJ present))) (, ,) (CC but) (VP (VBZ is) (ADJP (JJ capable) (PP (IN of) (S (VP (VBG switching) (PP (TO to) (NP (ADJP (JJ fermentation) (CC or) (JJ anaerobic)) (NN respiration))) (SBAR (IN if) (S (NP (NN oxygen)) (VP (VBZ is) (ADJP (JJ absent)))))))))))))))))) (. .)))
A facultative anaerobe is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent.
(ROOT (S (NP (NNP Fermentation)) (VP (VBZ is) (NP (NP (DT the) (NN process)) (PP (IN of) (S (VP (VBG making) (NP (NN atp)) (PP (IN without) (NP (NN oxygen)))))))) (. .)))