In biology, some groups of organisms are exclusively unicellular which means all organisms of the group are made of one cell, some are exclusively multicellular which means all organism are made of two or more cells and in some cases in a group there can be both single-celled and multicellular organisms which occur in both algae and fungi. Indeed, in these two groups, there are unicellular organisms as Chlorella (algae) or yeast (fungus) that contain only one cell and multicellular organisms such as Kelp (algae) or regular mushrooms (fungus) that are both multicellular. On the other hand, protozoa only contain unicellular organisms. This means the groups that contain single-celled and multicellular organisms are algae and fungi.
