Gene flow occurs when individuals move into or out of a population, and gene flow tends to decrease differentiation. Given these facts, what tends to occur when individuals move in and out of a population among the following options:
- By wind and rain
 - permineralization
 - The bending of a ray of light
 - Something with a head, thorax, and abdomen
 - a decrease in differentiation
 - competing for resources
 - barks and snarls
 - metabolic reaction


 

     a decrease in differentiation    