Bud Barnes, age 14, of Milford, Utah, for his question:
What does an amoeba eat?
A single celled protozoan is infinitesimally small and naturally dines on an infinitesimally small scale. The minuscule amoeba is one of these microscopic members of the animal kingdom. Yet the small creature is a hunter, and many of the items on his diet are caught and eaten alive.
The largest of these teeming protozoa are just big enough to be seen as vague specks of matter. Average amoebas measure 100 to an inch, and many are much smaller. Each amoeba is a single cell of living protoplasm without head or limbs. Regardless of these handicaps, the capable creature makes his own living and copes with his surroundings. What's more, the microscopic amoeba is just about immortal.
His diet includes a wide variety of scraps and living things even smaller than himself. His methods of capturing and digesting his food are even more fascinating than some of the items on his diet. The amoeba is by nature a hunter who preys upon microscopic animals and plants that share his watery world. A drop of pond water teems with assorted living things, and life on this miniature scale is often a matter of eat or be eaten.
There are many protozoa much smaller than the prowling amoeba. He may capture and devour a ciliate who has just stuffed himself with a meal of paramecium. The ciliate is a mere snack sized morsel to the amoeba, and the paramecium may be no more than a normal meal to the ciliate. Other live items on the amoeba's diet include single-cell swimmers called flagellates and a wide variety of other water dwelling protozoa.
The amoeba also devours single celled members of the plant kingdom. His salads include tiny diatoms and assorted bacteria. He may also eat microscopic fragments of decaying plant and animal material that are always sifting and drifting through his watery world. A few amoebas live parasitic lives within the living cells of larger animals. One of these parasites causes a disease called amoebic dysentery in man. Most amoebas, however, live capable and independent lives in fresh or salt water or in the soil.
The word for the amoeba's body is shapeless, and his shapeless form changes from minute to minute. He extends probing fingers called pseudopods and flows along like a spreading blot of colorless ink. Each morsel of food is enfolded by two pseudopods and engulfed by the little hunter's body of soft cytoplasm. There, it is digested in a temporary stomach called a food vacuole, and the indigEStib1E crusts are left behind as the prowling amoeba flows on in search of his next morsel.
A well fed amoeba hands on life to a new generation by dividing himself. The single cell separates into a pair of identical twins, and the two amoebas carry on with renewed life. No parents or grandparents are left behind to grow old and die, and barring accidents the life of the amoeba can last indefinitely.