Answer:
When calcium concentration increases during depolarization, it shifts the conformation of troponin and tropomyosin, and actin is able to associate with myosin. As calcium is taken up again by the sarcoplasmic reticulum the muscle cell relaxes.
 
        
             
        
        
        
Answer:
Biotic interacting with biotic is the answer.
Explanation:
Biotic=Alive such as plants,animal,and human.
Abiotic=Non-living
 
        
                    
             
        
        
        
Radiometric dating is a kind of technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed.