Answer:
12% I think this is right answer v
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Answer:
If the two magnets have their two N poles pointing up then when they are side by side they will repel each other but when they are head-to-tail they will attract. 
Explanation:
so a positive and a negative will attract
 
        
                    
             
        
        
        
Seed plants became more versatile and able to live in various climates and areas which others could not, letting seed plants to reproduce much more rapidly 
        
             
        
        
        
I belive they are to grow, repair, and reproduce. 
 
        
             
        
        
        
Striated muscles contain repeating sarcomeres of overlapping arrays of long, thin actin and thicker myosin filaments. Myosin filaments contains the myosin heads, which are enzymes that can bind to actin, split and make use of the energy from ATP. When muscle contraction starts, myosin heads bind to actin, change their configuration on actin, liberating the products of ATP hydrolysis and causing slide of the actin and myosin filaments. The action of the proteins troponin and  tropomyosin on the actin filaments regulates vertebrae striated muscle contraction. The release of calcium ions from the sarcoplasmic reticulum is triggered by the nervous stimulation which causes depolarization of muscle membrane. Calcium ions bind to troponin and thus cause or allow the tropomyosin strands on the actin filament to move so that the part of the actin surface where myosin heads need to bind is uncovered. Contraction then occurs and only stops when the sarcoplasmic reticulum pumps calcium out of the muscle interior.
So basically, what triggers the uncovering of the myosin binding site on actin is the calcium ions binding to troponin and changing configuration.