( ( An organ ) ( ( is ( ( a structure ) ( that ( consists ( of ( ( ( ( two or ) more ) types ) ( of ( tissues ( that ( ( work together ) ( to ( do ( the ( same job ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (NN organ)) (VP (VBZ is) (NP (NP (DT a) (NN structure)) (SBAR (WHNP (WDT that)) (S (VP (VBZ consists) (PP (IN of) (NP (NP (QP (CD two) (CC or) (JJR more)) (NNS types)) (PP (IN of) (NP (NP (NNS tissues)) (SBAR (WHNP (WDT that)) (S (VP (VBP work) (ADVP (RB together)) (S (VP (TO to) (VP (VB do) (NP (DT the) (JJ same) (NN job))))))))))))))))) (. .)))
An organ is a structure that  consists of two or more types of tissues that work together to do the same job.
(ROOT (S (NP (DT A) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN organ)) (VP (VBZ is) (NP (NP (DT a) (NN structure)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (VP (VBN composed) (PP (IN of) (NP (NP (QP (CD one) (CC or) (JJR more)) (NNS types)) (PP (IN of) (NP (NNS tissues))))))))))) (. .)))
A(n) organ is a structure that is composed of one or more types of tissues.