Because they have no competitors in any echological niche
        
                    
             
        
        
        
I'm having trouble on this too :(
        
             
        
        
        
The answer to this question is true
        
             
        
        
        
In terms of macromolecules, needed and utilized by organisms to carry out essential metabolic chemical reactions and for maintaining structure would be Lipids. 
Lipid based molecules or Fats tend to store the most energy, as breaking chemical bonds connecting fatty acid chains of long hydrocarbons releases quite a bit of energy.
        
             
        
        
        
Answer:
C.  Oxygen concentration decreases as altitude increases
Explanation:
Higher altitudes have lower levels of oxygen and decreased air pressure.