( It ( ( 's ( a ( growing population ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ 's) (NP (DT a) (VBG growing) (NN population))) (. .)))
It's a growing population.
(ROOT (S (SBAR (IN As) (S (NP (DT the) (NN population)) (VP (VBZ grows)))) (, ,) (NP (NP (NN competition)) (PP (IN for) (NP (NN food)))) (VP (VBZ grows)) (. .)))