Organ systems are made up of tissues which are made up of cells.
Hopefully that helps and if u need a brief explanation about that just text me.
Explanation:
When you make the cross. You get
HH HH Hh Hh.
So the genotypic ratio - 2:2 which is also 1:1.
The phenotypic ratio - 4. Since Hh and HH are horned organisms. So they only differ in their genotypic make up.
Yes. Indirectly, through plants. Without plants using photosynthesis, and therefore, creating oxygen, we wouldn't have enough breathable air.
I think its acid fermentation, but I could be wrong. My class studied this a while ago.