Cell Thery
unicellular organisms

Cell Thery -Most of these debates involved the nature of cellular regeneration, and the idea of cells as a fundamental unit of life. Cell theory was eventually formulated in 11838.All living organisms are composed of one or more cells.The cell is the most basic unit of life. All cells arise from pre-existing, living cells.

Multicellular-like plants, fungi, animals and brown algae—  a single cell and generate a multi-celled organisms.

Unicellular organisms- is an organism that consists of only one cell unlike a Multicellular organisms  that consists of multiple cells. But a unicellular is consistent of only one cell.