People living in equatorial countries have a darker skin tone than others. what would be the reason for this change in skin tone

Why does the skin of your finger shrink when you wash clothes for a long time?

What must be true for natural selection to heppen

Which phrase is the best summary of the model shown? a. the transfer of the sun's energy through trophic levels b. a series of aerobic and anaerobic reactions c. a transformation of light energy into chemical energy d. the breakdown of food molecules