( ( For ecosystems ) ( , ( ( ( the ( major source ) ) ( of energy ) ) ( ( is ( ( sunlight , ) ( which ( ( passes ( from organism ) ) ( to ( organism ( in ( food webs ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN For) (NP (NNS ecosystems))) (, ,) (NP (NP (DT the) (JJ major) (NN source)) (PP (IN of) (NP (NN energy)))) (VP (VBZ is) (NP (NP (NN sunlight)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ passes) (PP (IN from) (NP (NN organism))) (PP (TO to) (NP (NP (NN organism)) (PP (IN in) (NP (NN food) (NNS webs)))))))))) (. .)))
For ecosystems, the major source of energy is sunlight, which passes from organism to organism in food webs.
(ROOT (S (NP (NNP Sunlight)) (VP (VBZ is) (NP (NP (DT the) (JJ main) (NN source)) (PP (IN of) (NP (NP (NN energy)) (PP (IN for) (NP (NP (DT all)) (PP (IN of) (NP (NP (DT the) (NNS organisms)) (PP (IN in) (NP (JJS most) (NN food) (NNS chains))))))))))) (. .)))
Sunlight is the main source of energy for all of the organisms in most food chains.