( ( ( ( ( ( All ( of ( the ( organisms present ) ) ) ) ( ( are commonly ) ( ( found ( in ( the ( photic zone ) ) ) ) ( because ( they ( need ( abundant oxygen ) ) ) ) ) ) ) , ) and ) ( many ( may ( have ( had ( photosynthetic zooxanthellae ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (DT All)) (PP (IN of) (NP (DT the) (NNS organisms) (NN present)))) (VP (VBP are) (ADVP (RB commonly)) (VP (VBN found) (PP (IN in) (NP (DT the) (JJ photic) (NN zone))) (SBAR (IN because) (S (NP (PRP they)) (VP (VBP need) (NP (JJ abundant) (NN oxygen)))))))) (, ,) (CC and) (S (NP (DT many)) (VP (MD may) (VP (VB have) (VP (VBN had) (NP (JJ photosynthetic) (NN zooxanthellae)))))) (. .)))
All of the organisms present are commonly found in the photic zone because they need abundant oxygen, and many may have had photosynthetic zooxanthellae.
(ROOT (S (PP (IN On) (NP (DT a) (JJ global) (NN scale))) (, ,) (NP (NP (NNS plants)) (CC and) (NP (JJ other) (JJ photosynthetic) (NNS organisms))) (VP (VBP have) (VP (VBN generated) (NP (NP (DT all)) (PP (IN of) (NP (NP (DT the) (NN oxygen)) (PP (IN in) (NP (DT the) (NN air)))))))) (. .)))
On a global scale, plants and other photosynthetic organisms have generated all of the oxygen in the air.