In this system, four kingdoms consist of Eukaryotic organisms. The two most familiar kingdoms are Animalia and plantae, contain only organisms that are multi-cellular during most of their life cycle. The kingdom fungi contain multi-cellular forms and single celled yeasts. The large number of unicellular eukaryotes are arbitrarily grouped into a single kingdom called Protista. This kingdom includes the algae all of which are unicellular during important parts of their life cycle, and the protoza. The other kingdom, kingdom monera consists of prokaryotic organisms.

The five-kingdoms scheme of classification is based on the following criteria:

• The complexity of cell structure Prokaryote or Eukaryote
• The complexity of organism’s body…… Unicellular or multicellular
• The mode of nutrition ..... Autotrophic or heterotrophic

The four classification schemes are:

1. Two kingdom system – Plantae and Animalia
2. Three kigdom system – Protista, Plantae and Animalia
3. Four kingdom system – Monera, Protista, Plantae and Animalia
4. Five kingdom system – Monera, Protista, Fungi, Plantae and Animalia