Organisms are the biotic parts of an ecosystem.
        
             
        
        
        
Fossils are the remains or impression of the dead animals and plants that lived in the past.
        
                    
             
        
        
        
Answer:
PS:Can I be brainliest.
Have a nice day
Explanation:
Each molecule has a characteristic size and shape that determines its function in the living cell. The shapes of molecules are determined by the positions of the atoms' orbitals. When an atom forms covalent bonds, the orbitals in its valence shell are rearranged.
 
        
                    
             
        
        
        
I think the answer is D. Circulatory  because this system helps to get the absorbed nutrients throughout the whole body