( ( ( ( ( ( An ( ectothermic animal ) ) ( is ( one ( who ( ( can not ) ( regulate ( its ( own ( body temperature ) ) ) ) ) ) ) ) ) , ) so ) ( ( its ( body temperature ) ) ( fluctuates ( according ( to ( its surroundings ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT An) (JJ ectothermic) (NN animal)) (VP (VBZ is) (NP (NP (CD one)) (SBAR (WHNP (WP who)) (S (VP (MD can) (RB not) (VP (VB regulate) (NP (PRP$ its) (JJ own) (NN body) (NN temperature))))))))) (, ,) (IN so) (S (NP (PRP$ its) (NN body) (NN temperature)) (VP (VBZ fluctuates) (PP (VBG according) (PP (TO to) (NP (PRP$ its) (NNS surroundings)))))) (. .)))
An ectothermic animal is one who cannot regulate its own body temperature, so its body temperature fluctuates according to its surroundings.
(ROOT (S (NP (NNP Ectothermic)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (NP (NNS animals)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (RB not) (VP (VB raise) (NP (PRP$ their) (NN body) (NN temperature)) (PP (IN on) (NP (PRP$ their) (JJ own))))))))))) (. .)))