( ( Thermoregulation The ) ( ( means ( by ( which ( ( an animal ) ( maintains ( its ( body temperature ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Thermoregulation) (NNP The)) (VP (VBZ means) (PP (IN by) (SBAR (WHNP (WDT which)) (S (NP (DT an) (NN animal)) (VP (VBZ maintains) (NP (PRP$ its) (NN body) (NN temperature))))))) (. .)))
Thermoregulation The means by which an animal maintains its body temperature.
(ROOT (S (NP (NNP Thermoregulation)) (VP (VBZ is) (NP (NP (DT the) (NN process)) (SBAR (WHNP (WHADVP (WRB when)) (NNS animals)) (S (VP (VBP maintain) (NP (DT an) (JJ internal) (NN temperature))))))) (. .)))