( ( ( The activity ) ( of ( a ( death instinct ) ) ) ) ( ( can ( be ( determined ( ( ( at ( ( ( the level ) ( of ( individual cells ) ) ) ( which ( have ( a ( ( genetically predetermined ) ( life span ) ) ) ) ) ) ) ( but not ) ) ( at ( ( the level ) ( of ( the ( whole organism ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN activity)) (PP (IN of) (NP (DT a) (NN death) (NN instinct)))) (VP (MD can) (VP (VB be) (VP (VBN determined) (PP (PP (IN at) (NP (NP (DT the) (NN level)) (PP (IN of) (NP (JJ individual) (NNS cells))) (SBAR (WHNP (WDT which)) (S (VP (VBP have) (NP (DT a) (ADJP (RB genetically) (JJ predetermined)) (NN life) (NN span))))))) (CONJP (CC but) (RB not)) (PP (IN at) (NP (NP (DT the) (NN level)) (PP (IN of) (NP (DT the) (JJ whole) (NN organism))))))))) (. .)))
The activity of a death instinct can be determined at the level of individual cells which have a genetically predetermined life span but not at the level of the whole organism.
(ROOT (S (NP (DT A) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN cell)) (VP (VBZ is) (NP (NP (DT the) (JJS lowest) (NN level)) (PP (IN of) (NP (NN organism))) (SBAR (WHNP (WDT that)) (S (VP (MD can) (VP (VB perform) (NP (NP (DT all) (NNS activities)) (VP (VBN required) (PP (IN for) (NP (NN life))))))))))) (. .)))