Robert Toepfer, age 14, of Madrid, Iowa, for his question:
How does an amoeba digest its food?
This famous midget is a microscopic protozoan, a qualified single celled member of the animal kingdom. Though small, the amoeba is always busy. Every aspect about him is fas¬cinating, especially his busy search for food. His techniques for devouring and digesting his snacks are downright astounding.
The average amoeba, with the help of 99 of his cousins, could form a row one inch long. Your intestine tubes measure many inches in length and they need the help of other organs and biological parts to carry on the work of digesting your food., The amoeba manages to devour and digest his food with the help of only one living cell. This same cell also carries on all the other necessary activities of life. His small size may seem a disadvantage, but nature has balanced his small handicaps with some very worthwhile rewards. For one thing, the amoeba may be immortal.
His miniature digestive system is one feature in a streamlined operation that includes hunting and devouring and elimination. The amoeba is nothing if not streamlined. His one and only cell is a nucleus surrounded by a blob of cytoplasm and enfolded in an elastic, tissue thin skin. He is a blob of protoplasm and he hunts by flowing. His stretchable skin pokes out a pseudopod, a false foot. When he senses that this probe is promising, the pseudopod expands and the cytoplasm and nucleus flow inside to fill it.
This gliding trick moves the entire cell from one place to another. Pseudopods poke forth from any angle, for the amoeba has no back or front or sides to suggest direc¬tions. Eventually the little hunter senses a victim. It may be a bacterium or a protozoan smaller than himself. One and then another pseudopod flows around it and the victim is engulfed. Dinner is now inside the living cell and digestion begins.
Under a microscope, the food can be seen wadded into a small package called a food vacuole. The devoured victim is not in usable form. So enzymes and other chemicals in the amoeba's jellified stuffing react with its substances. Some are changed into food elements that can be used to nourish and energize the amoeba. This simplified chemical process is somewhat similar to the more complex processes in your own digestive system. Like you, the amoeba also finds that certain substances in his dinner are useless.
When all the goodness has been extracted, the food vacuole is stuffed with a wad of useless waste material. The amoeba has a simplified method of disposing of his waste. The vacuole is nudged to the edge of the cell and moves outside, right through any spot in the amoeba's pliable skin. Meantime the amoeba has engulfed and devoured another and perhaps another victim. He is comfortably satisfied when there are several food vacuoles inside his cell, each at a different stage of digestion.
The amoeba's family life is the last word in simplification. He needs no mate, no home and no children. When his cell is well fed, it prepares to multiply. The nucleus that governs the cell doubles itself. The two copies move apart and each takes a separate half of the jelly. The amoeba multiplies by dividing into a pair of twins. No aging parents are left behind. Barring accidents, the amoeba could go on living and multiplying for ages. The streamlined, simplified midget may well be immortal.