- All living organisms can be grouped or ‘classified’ using a classification system that consists of five kingdoms. These five kingdoms are:
- The first four kingdoms in this list (the animals, plants, fungi and protoctists) can actually be grouped together, as they are all eukaryotic organisms (also known as eukaryotes)
Animals, plants, fungi and protoctists are all eukaryotes
- Eukaryotic organisms can be multicellular or single-celled and are made up of cells that contain a nucleus with a distinct membrane
An animal cell (left) and plant cell (right) as seen under a light microscope. They are both eukaryotic cells as they both have a distinct membrane-bound nucleus.
- Prokaryotic organisms (also known as prokaryotes) are in a separate kingdom and are different from eukaryotes as they are always single-celled and do not contain a nucleus (instead, the nuclear material of prokaryotic cells is found in the cytoplasm)
- Bacteria are prokaryotic organisms
- Prokaryotic cells are substantially smaller than eukaryotic cells