( ( A amphibian ) ( ( reproduces sexually ) . ) )
(ROOT (S (NP (DT A) (NN amphibian)) (VP (VBZ reproduces) (ADVP (RB sexually))) (. .)))
A amphibian          reproduces sexually.
(ROOT (S (NP (NNS Vertebrates)) (VP (VB reproduce) (ADVP (RB sexually))) (. .)))