( ( Like ( ( a network ) ( of roads ) ) ) ( , ( ( ( the job ) ( of ( the ( circulatory system ) ) ) ) ( ( is ( to ( ( ( allow ( ( the transport ) ( of materials ) ) ) ( from ( one place ) ) ) ( to another ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN Like) (NP (NP (DT a) (NN network)) (PP (IN of) (NP (NNS roads))))) (, ,) (NP (NP (DT the) (NN job)) (PP (IN of) (NP (DT the) (JJ circulatory) (NN system)))) (VP (VBZ is) (S (VP (TO to) (VP (VB allow) (NP (NP (DT the) (NN transport)) (PP (IN of) (NP (NNS materials)))) (PP (IN from) (NP (CD one) (NN place))) (PP (TO to) (NP (DT another))))))) (. .)))
Like a network of roads, the job of the circulatory system is to allow the  transport of materials from one place to another.
(ROOT (S (NP (NP (DT The) (JJ main) (NN function)) (PP (IN of) (NP (DT the) (JJ circulatory) (NN system)))) (VP (VBZ is) (S (VP (TO to) (VP (VB transport) (NP (NNS materials)))))) (. .)))