Answer:
Dust bowl resulted from extreme drying and loosening of the soil that resulted in soil erosion by wind. Thus, it can be related that poor agricultural practices like over plowing , over grazing and leaving the land barren are human activities that must have contributed to the dust bowl.
Explanation:
- Dust bowl is referred to a period in early twentieth century when the the American and Canadian prairies faced severe dust storms.
- These dust storms resulted from severe drought and failure of practices to prevent soil erosion.
- Several people and livestock died as a result of choking.
- Over plowing, removal of top soil and  small grasses exposed the soil to eroding winds and caused the dust storms.
 
        
             
        
        
        
1 = Blizzard 
2 = Tornado
3 = Thunderstorm
4 = Hurricane
5 = Hailstorm
        
             
        
        
        
Explanation:
Natural selection is the mechanism that is responsible for the evolution of organisms.  
In the given case, the Freshwater shrimp has been introduced to a pond in which the two species with variations are introduced.  
The <em>C. cantonensis </em>is brighter in color whereas the <em>C. multidentata</em> is mottled drab in color. The predator fish can feed easily on the species which is brighter therefore <em>C. cantonensis</em> is more susceptible. The mottled drab species is not easily predated by the species.  
The 30 % offsprings of <em>C. cantonensis</em> can survive till the reproductive age  whereas 75% of C. multidentata. This shows that natural selection has acted on the color of the shrimp species selected against the predator fish species.
The species with mottled drab color is the result of the differential reproductive rate.
 
        
             
        
        
        
Personally, I think since all the changes in the world are affecting the natural environment adaptive traits are important so that they can help maximize its reproductive success so its species can survive.