7) Why is it that many life forms complement one another to achieve their goal? For example, a plant processes carbon dioxide through photosynthesis, which expels oxygen into the air for humans and other species to use.
Contrary to popular belief, humans and animals do
not need plants and trees for their oxygen. The oxygen we breathe today was formed millions of years ago.
While it is true that during the day plants produce oxygen and consume carbondioxide, the opposite happens at night: they produce CO2 and consume oxygen like we do. Furthermore, when a plant or tree dies, it (usually) rots away. The bacteria use oxygen in that process too. All in all, in its life a plant or tree consumes about as much oxygen as it produces.