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.
The action of spectrum of photosynthesis in plants roughly corresponds to the absorption spectrum of the pigment chlorophyll, but not exactly. 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.