( ( ( The iris ) ( controls ( ( the amount ) ( of ( light ( ( entering ( into ( the eye ) ) ) ( by ( ( making ( the opening ) ) ( at ( the center ) ) ) ) ) ) ) ) ) ) ( , ( ( called ( ( ( the pupil ) , ) ( either ( ( larger or ) smaller ) ) ) ) . ) ) )
(ROOT (SINV (S (NP (DT The) (NNS iris)) (VP (VBZ controls) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN light)) (VP (VBG entering) (PP (IN into) (NP (DT the) (NN eye))) (PP (IN by) (S (VP (VBG making) (NP (DT the) (NN opening)) (PP (IN at) (NP (DT the) (NN center)))))))))))) (, ,) (VP (VBD called)) (NP (NP (DT the) (NN pupil)) (, ,) (NP (NP (DT either)) (ADJP (JJR larger) (CC or) (JJR smaller)))) (. .)))
The iris controls the amount of light entering into the eye by making the opening at the center, called the pupil, either larger or smaller.
(ROOT (S (NP (DT The) (NN pupil)) (VP (VBZ is) (NP (NP (DT the) (NN name)) (PP (IN of) (NP (NP (DT the) (JJ black) (NN opening)) (PP (IN in) (NP (NP (DT the) (NN eye)) (SBAR (WHNP (WDT that)) (S (VP (VBZ lets) (SBAR (S (NP (NN light)) (VP (VBP enter))))))))))))) (. .)))