( ( ( ( ( Human activities ) , ) ( such ( as ( ( ( overhunting ( a species ) ) or ) ( destroying ( its habitat ) ) ) ) ) ) , ) ( ( have ( ( ( caused ( ( the extinction ) ( of ( ( ( ( some species ) , ) ( such ( as ( the ( passenger pigeon ) ) ) ) ) , ) ) ) ) and ) ( ( threatened ( many others ) ) ( -LRB- ( ( see ( endangered species ) ) -RRB- ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Human) (NNS activities)) (, ,) (PP (JJ such) (IN as) (S (VP (VP (VBG overhunting) (NP (DT a) (NN species))) (CC or) (VP (VBG destroying) (NP (PRP$ its) (NN habitat)))))) (, ,)) (VP (VBP have) (VP (VP (VBN caused) (NP (NP (DT the) (NN extinction)) (PP (IN of) (NP (NP (DT some) (NN species)) (, ,) (PP (JJ such) (IN as) (NP (DT the) (NN passenger) (NN pigeon))) (, ,))))) (CC and) (VP (VBN threatened) (NP (JJ many) (NNS others)) (PRN (-LRB- -LRB-) (S (VP (VB see) (NP (VBN endangered) (NNS species)))) (-RRB- -RRB-))))) (. .)))
Human activities, such as overhunting a species or destroying its habitat, have caused the extinction of some species, such as the passenger pigeon , and threatened many others (see endangered species ).
(ROOT (S (NP (NNP Human) (NNP overpopulation)) (VP (VBZ is) (VP (VP (VBG crowding) (PRT (RP out)) (NP (JJ other) (NNS species))) (CC and) (VP (VBG making) (S (NP (NP (PDT all) (DT the) (JJ other) (NNS causes)) (PP (IN of) (NP (NN extinction)))) (ADJP (RBR worse)))))) (. .)))