Answer:
B) There is an increase in the number of giraffes with long necks in areas of Africa where low-growing trees have died
Explanation:
The directional selection is one of the ways of the natural selection in which the natural selection selects or favours the most extreme trait of the species and the extreme trait show higher fitness than the normal or average trait.
In the given question, the case of Giraffe necks shows directional selection as the normal length of the neck is not favoured by the environment but the extreme trait that is long neck is favoured by the environment and the selection shifted to that level.
Thus, Option-B is the correct answer.
 
        
                    
             
        
        
        
Answer:
This is because Protons are moving down a concentration gradient.
 
        
             
        
        
        
Not really sure but I think is that rodents mate randomly but wait for someone else to answer cause I’m not 100% sure
        
             
        
        
        
Answer: AV node will takeover the function of SA node if it’s not functioning, but definitely at a slower rate than SA node. 
Explanation: