( She ( ( ( ( walked ( her fingers ) ) ( up ( ( ( my backbone ) , ) ( one vertebra ) ) ) ) ( at ( a time ) ) ) . ) )
(ROOT (S (NP (PRP She)) (VP (VBD walked) (NP (PRP$ her) (NNS fingers)) (PP (IN up) (NP (NP (PRP$ my) (NN backbone)) (, ,) (NP (CD one) (NN vertebra)))) (PP (IN at) (NP (DT a) (NN time)))) (. .)))
She walked her fingers up my backbone, one vertebra at a time.
(ROOT (S (NP (NNP Vertebrata)) (VP (VBP are) (VP (VBN characterized) (PP (IN by) (NP (NP (DT the) (NN presence)) (PP (IN of) (NP (NN backbone))))))) (. .)))
Vertebrata are characterized by the presence of backbone.