Billy Bush, age 10, of St. Catharines, Ont., Canada, for his question:
HOW CAN AN AMEBA CATCH HIS FOOD?
The ameba is a mini blob of jelly, too small for human eyes to see. He has no definite shape, no permanent legs or other parts. Yet, like all animals, he needs food. And, believe it or not, this little critter that seems so helpless is really a very successful hunter. Actually, his jellified body is just right for catching the scraps of floating food on which he feeds.
Your body has zillions of living cells, each performing its own special duties. The ameba's body is just one single living cell, which performs all the duties needed to keep him alive. Basically it is a mini blob of cytoplasm, that miraculous substance that carries on life in all living cells. Inside the cell is a tiny nucleus that governs all the activities. The whole cell is held together by a thin, pliable skin.
The ameba lives in a watery world, populated by bacteria and a vast variety of even smaller living things. These are included on his menu and to catch them he must go hunting. He can travel in any direction and he gets from here to there by changing his shape. He advances by poking forth a finger called a pseudopod, which means a false foot. Then the rest of his pliable body flows into the foot and, lo, the ameba has moved a step forward.
When he senses a morsel of food, he pokes forth two of his pseudopods and folds them around to engulf it. The victim is captured and surrounded by the ameba's jellyfied cell. Inside his body, it becomes a small wad called a food vacuole.
The food vacuole becomes a temporary stomach and the nourishment is soon digested. The wad of waste material is edged to the side and soon passes out of the ameba's body. Meantime the little hunter has used and reused his pseudopods to capture and engulf another and another meal. And inside his cell, several food vacuoles are in various stages of digestion.
The single cell ameba is one of nature's small miracles. But he saves his cleverest trick for when time comes to multiply. This he does by dividing his clever little body into two equal parts. The original ameba becomes a brand new pair of identical twins. Since no parents are left to grow old and die, the amazing ameba may have the secret of immortality.