The cost of growth

As one of the trees in our apartment grows, the leaves on the topmost branches grow broader, seemingly at the expense of the lower leaves, turning yellow and falling off. I cannot decide whether it is unfair, or just the way of things. Are the lower yellow leaves happy to support the tree as a whole? Sacrificing their own lives for the leaves on the topmost branches, which reach for the light that is necessary to sustain the whole tree. Or do they shake their fists at the upper class of leaves? Angry to have their own lives cut short, even if it is for the good of the whole tree.