Amoeba

Amoeba is a genus of single-celled organisms belonging to the protista group. They have a single nucleus without a fixed shape, which changes as they move or feed. They move by extending part of the nucleus forward, a process called pseudopodia (false feet).

Most of these organisms live in fresh water that is still, such as ponds, shallow streams, and the muddy bottom of water bodies. They feed on bacteria, small algae, and debris from other organisms.

Structure of the cell

The amoeba cell has an outer membrane (cell membrane) that is flexible, cytoplasm, and a nucleus containing genetic information. It also has a special vacuole that removes excess water from the cell, called a contractile vacuole. When food is taken in, a food vacuole forms where enzymes break down the food.

How it feeds

Amoeba captures food through a process called phagocytosis: the false feet on both sides wrap around the food item until it is enclosed inside the cell. Afterwards, enzymes convert the material into something the cell can use. Undigested material is expelled on either side of the cell.

Reproduction

The normal mode of reproduction is asexual: the cell divides into two identical cells, a process called binary fission. When conditions become difficult—such as drought or unsuitable temperature—some organisms form a cyst, a hard shell in which they remain dormant until conditions improve.

Distinction from disease-causing organisms

The term 'amoeba' is often used broadly to refer to all single-celled organisms that use false feet. However, the genus Amoeba is distinct from organisms that cause human disease, such as Entamoeba histolytica, which is linked to dysentery. The genus Amoeba itself is generally not considered a cause of human disease.