<span>They have very stable outer electron shells</span>
        
             
        
        
        
For a fish to be buoyant, or float, it must displace less water or the same amount of water as its own body mass. ... Many fish use swim bladders to help them with quick depth changes. These bladders fill with air to help fish rise or release air so fish can sink, often in conjunction with forward movement.
 
        
                    
             
        
        
        
Answer:
Explanation:increasing the stimulation up to the maximal stimulus
 
        
             
        
        
        
Answer: Volcanic materials ultimately break down and weather to form some of the most fertile soils on Earth, cultivation of which has produced abundant food and fostered civilizations. The internal heat associated with young volcanic systems has been harnessed to produce geothermal energy
Explanation:
 
        
             
        
        
        
Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce.