( Biodiversity ( ( is ( expressed ( as ( ( the number ) ( of ( species ( per ( unit area ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Biodiversity)) (VP (VBZ is) (VP (VBN expressed) (PP (IN as) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (NNS species)) (PP (IN per) (NP (NN unit) (NN area))))))))) (. .)))
Biodiversity is expressed as the number of species per unit area.
(ROOT (S (NP (NNP Biodiversity)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (NP (DT the) (NN measurement)) (PP (IN of) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN variation)) (PP (IN of) (NP (NP (NNS species)) (PP (IN in) (NP (DT a) (VBN given) (NN area))))))))))))) (. .)))
Biodiversity is the term for the measurement of the amount of variation of species in a given area.