Amoeba

The amoeba is a tiny, one-celled organism. You need a microscope to see most amoebas - the largest are only about 1 mm across. Amoebas live in fresh water, in salt water, in wet soil, and in animals (including people). There are many different types of amoebas. The name amoeba comes from the Greek word amoibe, which means change. (Amoeba is sometimes spelled ameba.)

Anatomy: An amoeba consists of a single blobby cell surrounded by a porous cell membrane. The amoeba "breathes" using this membrane - oxygen gas from the water passes in to the amoeba through the cell membrane and carbon dioxide gas leaves through it. A complex, jelly-like series of folded membranes called cytoplasm fills most of the cell. A large, disk-shaped nucleus within the amoeba controls the growth and reproduction of the amoeba.

Reproduction: Amoebas reproduce asexually by binary fission. A parent cell divides (the nucleus also divides in a process called fission) and produces two smaller copies of itself.