Prophase is the first step in mitosis and many changes occur. Chromatin fibers become coiled into chromosomes, with each chromosome having 2 chromatids joined at a centromere. The mitosis spindle, composed of microtubules and proteins, form in the cytoplasm.
This is only one part of the answer, but its important: high-altitude O2 absorbs much energy from the sun (including radioactivity), which forms the ozone layer. this process protects delicate molecules important to life - most notably dna
