( ( Organisms ( that ( only ( eat plants ) ) ) ) ( ( are ( known ( as herbivores ) ) ) . ) )
(ROOT (S (NP (NP (NNS Organisms)) (SBAR (WHNP (WDT that)) (S (ADVP (RB only)) (VP (VBP eat) (NP (NNS plants)))))) (VP (VBP are) (VP (VBN known) (PP (IN as) (NP (NNS herbivores))))) (. .)))
Organisms that only eat plants are known as herbivores.
(ROOT (S (NP (NNS Herbivores)) (VP (VBP are) (NP (NP (NNS heterotrophs)) (SBAR (WHNP (WDT that)) (S (VP (VBP eat) (NP (UCP (ADJP (JJ only)) (CC or) (ADVP (RB mainly))) (NNS plants))))))) (. .)))