Light energy is initially converted into chemical energy in he form of two compounds: NADPH, a source of energized electrons and ATP, the versatile energy currency that the light reactions produce no sugar, that happens in the second stage of photosynthesis, the Calvin cycle.
Life needs energy, water, heat and nutrients. Reduce the availability of one or more of those things and biodiversity generally decreases.
Tropical forests tend to be more diverse than polar ice caps. However, arctic seas tend to be more biologically interesting than the middle of the Sahara. I bet this is what your homework is looking for but it's important to remember there are counterexamples.
A lot of people did. Including me.
