A phyloGENETIC tree is not the same thing as a taxonomic tree, which is what Cal described. rRNA and molecular studies are used in phylogenetics to determine relations between species.
1 As the light intensity increases, the rate of photosynthesis increases. 2  However, the rate will not increase beyond a certain level of light intensity. 3  At high light intensities the rate becomes constant, even with further increases in light intensity, there are no increases in the rate.
Light with a wavelength of 500 nm (blue-green light) can stimulate photosynthesis even though blue-green light is not absorbed by chlorophyll. This lead to the discovery of carotenoids, which absorb blue-green light and transfer the energy of their excited electrons to chlorophyll.