Human Ear - How do ears help with balancing? Human Eyes - Why do we have two eyes instead of one? Osmosis - Why is grass killed if salt is sprinkled on it? Photosynthesis - Why is the upper surface of a leaf more green and shiny than the lower surface? Respiration - Why is it not good to sleep under a tree at night? Turgor Pressure - Why does a Touch Me Not plant close? Stomata - Why do water lilies have stomata on the upper side of their leaves? Respiration in Plants - Why should we not overwater potted plants? Transpiration - Why do cacti have spines? Nervous System - Why don't we feel pain when we cut our hair?