The correct answer would be the last one: "evolved from past organisms." This theory basically just states that all living organisms evolved from a single common ancestor. Hope this helped! :)
        
                    
             
        
        
        
Answer:
they have lower levels of the neurotransmitter serotonin
 
        
             
        
        
        
Answer:
if gametes were diploid, the number of chromosomes would multiply every generation. To avoid this complexity, gametes posses half the number of chromosomes as somatic cells.
i hope this helped
Explanation:
 
        
             
        
        
        
Answer:
a. RNA does not base pair and therefore cannot be replicated.