The answer would be plant. There is a kingdom called plantae, where all plant-like organisms fall, which means tree is under it. Birds and humans are under another kingdom called Animalia. 
 
        
             
        
        
        
When we're eating food, the different food stuffs need to be broken down from big molecules to smaller ones. This happens through different processses which happen in our body. For this reason, the larger molecules need energy to be broken up into smaller ones and when these happens these smaller ones get then taken up in our body and used up.
        
             
        
        
        
Mitochondria. The mitochondria has a variety of different functions and is therefore essential for the cell's productivity.
Hope this helps, if not, comment below please!!!
 
        
             
        
        
        
1. A gene is section of DNA that codes for a specific trait.
2. 2,001