In order to "invest" in later stages to get more energy per glucose molecule. It could also be because that is how it is done, it wouldn't be as efficient unless these stages were performed.
hope this helps!
Answer:
cell
tissue
organ
system
human organism
Explanation:
unicellular organisms only have one cell since two or more cells form a tissue their level of organization is restricted to cell
cell
two or more cells form a tissue
two or more tissue forms an organ
two or more organs form a system which must work in coordination for efficiency
two or more systems make up a human organism
