In london, peppered moths that were light colored blended in with trees of the area, and were well populated. over time, pollution caused the bark of the trees to darken, causing a shift in the number of light colored moths seen.

It depends on the surface of the levels. the rougher the surface, the greater is the frictional force. for rougher surfaces, you would need to exert greater force to move the object. the concept is that, you must overcome the frictional force in order to bring the object into motion. this is the reason why we add lubricants to the joints so they could easily move. this answer was on