( ( Coral reefs ) ( ( ar ( created ( by ( ( ( tiny organisms ) ( -- ( ( coral polyps ) -- ) ) ) ( that ( ( produce ( calcium ( carbonate ( ( -LRB- ( limestone -RRB- ) ) structures ) ) ) ) ( as ( their exoskeleton ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Coral) (NNS reefs)) (VP (VBP ar) (ADJP (VBN created) (PP (IN by) (NP (NP (JJ tiny) (NNS organisms)) (PRN (: --) (NP (CD coral) (NNS polyps)) (: --)) (SBAR (WHNP (WDT that)) (S (VP (VBP produce) (NP (NN calcium) (NN carbonate) (PRN (-LRB- -LRB-) (NP (NN limestone)) (-RRB- -RRB-)) (NNS structures)) (PP (IN as) (NP (PRP$ their) (NN exoskeleton)))))))))) (. .)))
Coral reefs ar created by tiny organisms -- coral polyps -- that produce calcium carbonate (limestone) structures as their exoskeleton.
(ROOT (S (NP (NNS Corals)) (VP (VBP build) (NP (NP (JJ hard) (NNS exoskeletons)) (SBAR (WHNP (WDT that)) (S (VP (VBP grow) (S (VP (TO to) (VP (VB become) (NP (NN coral) (NNS reefs)))))))))) (. .)))