( ( Ounce ( for ounce ) ) ( , ( ( ( birds ' ) hearts ) ( ( ( ( are ( three times ) ) ( the size ) ) ( of ( those ( in mammals ) ) ) ) . ) ) ) )
(ROOT (S (PP (ADVP (RB Ounce)) (IN for) (NP (NN ounce))) (, ,) (NP (NP (NNS birds) (POS ')) (NNS hearts)) (VP (VBP are) (NP (CD three) (NNS times)) (NP (DT the) (NN size)) (PP (IN of) (NP (NP (DT those)) (PP (IN in) (NP (NNS mammals)))))) (. .)))
Ounce for ounce, birds' hearts are three times the size of those in mammals.
(ROOT (S (PP (IN Like) (NP (NP (DT all) (NNS tetrapods)) (PP (IN except) (NP (NNS birds) (CC and) (NNS mammals))))) (, ,) (NP (NNS frogs)) (VP (VBP possess) (NP (NP (DT a) (NN heart)) (PP (IN with) (NP (CD three) (NNS chambers))))) (. .)))