( ( A ( food chain ) ) ( ( ( is really ) ( an ( energy chain ) ) ) . ) )
(ROOT (S (NP (DT A) (NN food) (NN chain)) (VP (VBZ is) (ADVP (RB really)) (NP (DT an) (NN energy) (NN chain))) (. .)))
A food chain is really an energy chain.
(ROOT (S (NP (NP (NN Loss)) (PP (IN of) (NP (NN energy)))) (VP (VBZ is) (NP (DT the) (NN reason)) (SBAR (IN that) (S (NP (NN food) (NN chain)) (ADVP (RB typically)) (VP (VBZ has) (NP (JJ few) (NNS levels)))))) (. .)))