( ( The ( excretory system ) ) ( ( ( controls ( ( ( the levels ) ( of ( ( water and ) salts ) ) ) ( in ( your body ) ) ) ) ( by ( removing wastes ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ excretory) (NN system)) (VP (VBZ controls) (NP (NP (DT the) (NNS levels)) (PP (IN of) (NP (NN water) (CC and) (NNS salts))) (PP (IN in) (NP (PRP$ your) (NN body)))) (PP (IN by) (S (VP (VBG removing) (NP (NNS wastes)))))) (. .)))
The excretory system controls the levels of water and salts in your  body by removing wastes.
(ROOT (S (NP (DT The) (JJ urinary) (NN system) (NN system)) (VP (VP (VBZ controls) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN water)))) (PP (IN in) (NP (DT the) (NN body)))) (CC and) (VP (VBZ removes) (NP (NNS wastes)))) (. .)))