Use the Following to Answer Questions

Multiple Choice

Use the following to answer questions :
Refer to the graphs below showing data from the studies of David Tilman and colleagues on the effect of species diversity on net primary productivity in prairie ecosystems.
-Based on the data in the two graphs,how can the effects of species richness and number of functional groups (niches) on NPP best be described?

A) Increased number of niches,which is tied to increased species richness,has a major effect on increasing NPP.
B) Increased species richness has less effect on increasing NPP than increased number of niches does.
C) Increased number of niches is responsible for the total effect of increased species diversity on NPP.
D) Increased species richness is responsible for the total effect of increased species diversity on NPP.
E) Increased number of niches and increased species richness independently increase NPP.