Answer:
Niche
Explanation:
Niche refers to adaptive features of an organism, its activity pattern and consumption of resources in the system. 
Niche of an organism refers to its habitat, activity role and functional position within system. It includes the resources such as food that it obtains from the habitat for its survival. 
 
        
             
        
        
        
When there is not enough oxygen for cells to use cellular respiration<span />
        
             
        
        
        
<span><span>Chaetognaths worms </span>are the transparent worms that prey on the other plankton.
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<span>C. obtain and use energy. </span>
        
                    
             
        
        
        
A main sequence star is bigger than a neutron star,because neutron stars are remnant degenerate matter from a collapsed star,they are completely made out of Neutrons and are extremely dense,and have a diameter of only a several Kilometers.M<span>ost of them have a mass of 1.35-2 Solar masses.</span>