By far the largest region of your brain is the forebrain (derived from the developmental prosencephalon), which contains the entire cerebrum and several structures directly nestled within it - the thalamus, hypothalamus, the pineal gland and the limbic system.
Well for one photosynthesis gives out oxygen. This makes all animals able to live. So in that way it helps us and the world around us. Without photosynthesis we also could not eat food. No animals could live and no plants ould live. VERY IMPORTANT!