( Young ( ( ( ( are altricial ) , ) ( which ( means ( they ( ( are ( blind ( , ( ( featherless and ) helpless ) ) ) ) ( at birth ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Young)) (VP (VBP are) (ADJP (JJ altricial)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ means) (SBAR (S (NP (PRP they)) (VP (VBP are) (ADJP (JJ blind) (, ,) (JJ featherless) (CC and) (JJ helpless)) (PP (IN at) (NP (NN birth)))))))))) (. .)))
Young are altricial, which means they are blind, featherless and helpless at birth.
(ROOT (S (NP (JJ Altricial) (NNS organisms)) (VP (VP (VBP are) (ADJP (JJ helpless) (PP (IN at) (NP (NN birth))))) (CC and) (VP (VBP require) (NP (NP (NNS lots)) (PP (IN of) (NP (NN help)))) (PP (IN from) (NP (PRP$ their) (NNS parents))))) (. .)))