Five-Kingdom System of Biological Classification

Proposed in 1969  by Robert Whitaker :

1. Kingdom Procaryotae (Monera):

Oldest  known cells. Lived over 3.5 billion years ago. Lack a nucleus and membrane bound organelles. The other four kingdoms are eucaryotes. Have  a true nucleus and membrane bound organelles.

2. Kingdom Protista:

Mostly unicellular, lack tissue organization. Most have flagella during life.

3. Kingdom Fungi:

May be unicellular (yeasts) or multicellular (molds). Many are saprotrophs.

4. Kingdom Plantae:

Multicellular, photosynthetic.

5. kingdom Animalia

Multicellular, heterotrophs that ingest food through a mouth or oral cavity.