Over a millions of years of animals and plants being crushed down in the ground<span />
        
             
        
        
        
Essential amino acids are amino acids that must be supplied to one's body by their diet because they cannot be synthesized from scratch. 
        
             
        
        
        
Answer: <u>Human intellect</u>
Explanation:
Adaptability refers to one's ability to readily  react to changes in one's environment. Humans easily adapt to changes and even modify or change our environment to solve obstacles or issues. This is integral to human intellect or intelligence -we are highly adaptive, capable of execution and organizing complex tasks. 
 
        
             
        
        
        
Answer:
Disruptive Selection.
Explanation:
Disruptive selection, also known as selection diversification, explains shifts in population genetics that prefer extreme values for a trait over intermediate values. In this case, trait variation increases, and the population is split into two different classes. So, in the given case where A "U-shaped" distribution for a trait, with high frequencies of individuals who exhibit extreme values for a trait (and few individuals with medium values), is most likely to be caused by Disruptive selection.