Convection is heat transfer by the mass movement of molecules from one place to another (Giancoli). Convection occurs because hot fluids rise. This is because when a fluid is heated, in most cases, its volume increases. Thus, its density decreases, and it experiences a buoyant force propelling it upwards. [/hide]
Next question: During photosynthesis, cells combine "disorderly" compounds (CO2 and H2O) into "orderly" glucose molecules. Is this a violation of the second law of thermodynamics?
It is not because you can decrease entropy in a certain system while taking heat from another source which will cause entropy of its own. The sun generates light through fusion creating huge amounts of entropy meaning that the total entropy of the UNIVERSE is still increasing, therefore following the second law.