Amoeba is a single-celled organism that lives in water and feeds on other plants, animals, and organisms using foot-like extensions called pseudopodia to surround food particles and form a food vacuole, where digestive juices inside help break down the trapped food for the cell to absorb and use for growth, repair, and reproduction, excreting undigested waste through other vacuoles, as it follows the basic steps of nutrition like humans but lacks a mouth or anus.