Sue realizes that she performs poorly on tests because she g…

Sue realizes that she performs poorly on tests because she gets so anxious that she loses confidence.  She wants to improve her test taking and for weeks before her next test she imagines sitting down to take the test while remaining calm, in control, and totally confident.  The preceding is an example of:

In one butterfly species, the colors of individuals range fr…

In one butterfly species, the colors of individuals range from white to black, with many shades of gray in between. If the butterflies in a mountain population become more and more similar in color over several generations (e.g., if most butterflies are the same shade of gray), what kind of evolutionary force is likely acting on the population?