It's something to do with the fact that having sickle cell anaemia reduces the chances of contracting malaria, obviously a very common disease in Africa. I'm not quite sure what the link is but hopefully this helps a little bit?
Answer: Erosion is the process by which natural forces move weathered rock and soil from one place to another. Gravity, running water, glaciers, waves, and wind all cause erosion. Deposition begins when erosion stops; the moving particles fall out of the water or wind and settle on a new surface.
In the winter its color changes to more resemble their <em>winter</em> surroundings, so they are more white, enabling them to blend in better with their white surroundings. In summer, its color changes to more resemble its <u><em /></u><em>summer</em> surroundings, so they are more brown like the rocks and ground around them.
A.Nitrogen
B.Humus
c.Manure
hope this helps
