Nitrogen,<span>The atmosphere is composed of ~78% nitrogen and ~21% oxygen, with small amounts of other gases. The bulk composition of the earth by weight is mostly, iron, oxygen, silicon and magnesium, in that order, with all the other elements making up only about 5% of the earth's weight.</span>
The answer is similarity
Hope help!
Photosynthesis uses sunlight energy to make glucose (energy stores). A by-product of photosynthesis is oxygen. plants use water and sunlight to grow and they produce oxygen. Animals eat plants, use oxygen and breathe out carbon dioxide. Since the space station is in the shadow of the earth, the plants are unable to complete the process of photosynthesis and the carbon dioxide that is being produced by the humans cannot be utilized by the plants due to no sunlight. Therefore the carbon dioxide is going to continue to build up as the energy storage molecules are being depleted and not replenished.