| Classification System | Kingdoms Included | Description | Basis of Classification |
|---|---|---|---|
| Very Early Classification | – | Non-scientific. | Was done instinctively not using criteria that were scientific but borne out of a need to use organisms for our own use – for food, shelter and clothing. |
| First Early Scientific Classification | 1. Plantae 2. Animalia |
Aristotle was the earliest to attempt a more scientific basis for classification. | Aristotle used simple morphological characters to classify plants into trees, shrubs and herbsAristotle divided animals on the basis of presence or absence of red blood. They are divided into two groups: (A) Anaima –Animals without red blood e.g. Sponges, Molluscs, Insects etc. (B) Enaima – Animals with red blood e.g. Fishes, Amphibia, Reptiles Birds, Mammals. |
| 2-Kingdom System | 1. Plantae 2. Animalia |
Proposed by Linnaeus. Divides all living organisms into plants and animals. | Based on basic structural and functional differences: plants are autotrophic and immobile, while animals are heterotrophic and mobile. |
| 3-Kingdom System | 1. Plantae 2. Animalia 3. Protista |
Proposed by Haeckel. Introduced Protista to include all unicellular organisms. | Based on cellular organization: Protista includes all unicellular organisms, while Plantae and Animalia include multicellular organisms. |
| 4-Kingdom System | 1. Plantae 2. Animalia 3. Protista 4. Monera |
Proposed by Copeland. Separated Monera (prokaryotes) from Protista (eukaryotes). | Based on cellular structure: Monera includes all prokaryotic organisms, while Protista includes unicellular eukaryotes. |
| 5-Kingdom System | 1. Plantae 2. Animalia 3. Protista 4. Monera 5. Fungi |
Proposed by Whittaker. Introduced Fungi as a separate kingdom due to its distinct characteristics. | Based on mode of nutrition and cellular organization: Fungi are distinct due to their absorptive heterotrophic nutrition, separate from Plantae and Animalia. |
Classification of Living Organisms
The classification of living organisms has evolved significantly over time, reflecting our growing understanding of biological diversity. Here’s a summary of the various systems:
1. 2-Kingdom System
- Kingdoms Included: Plantae and Animalia
- Description: Proposed by Linnaeus, this system was the earliest and simplest classification, dividing all life into two categories: plants and animals.
- Basis of Classification: Based on basic structural and functional differences: plants are autotrophic and immobile, while animals are heterotrophic and mobile.
2. 3-Kingdom System
- Kingdoms Included: Plantae, Animalia, and Protista
- Description: Haeckel introduced Protista to account for all unicellular organisms, providing a more nuanced classification.
- Basis of Classification: Based on cellular organization: Protista includes all unicellular eukaryotic organisms, while Plantae and Animalia include multicellular organisms.
3. 4-Kingdom System
- Kingdoms Included: Plantae, Animalia, Protista, and Monera
- Description: Proposed by Copeland, this system separated prokaryotes (Monera) from eukaryotes (Protista), refining the distinction among microorganisms.
- Basis of Classification: Based on cellular structure: Monera includes all prokaryotic organisms, while Protista includes unicellular eukaryotes.
4. 5-Kingdom System
- Kingdoms Included: Plantae, Animalia, Protista, Monera, and Fungi
- Description: Whittaker introduced Fungi as a separate kingdom due to their unique characteristics, especially their mode of nutrition through absorption, highlighting the complexity of life forms.
- Basis of Classification: Based on mode of nutrition and cellular organization: Fungi are distinct due to their absorptive heterotrophic nutrition, separate from Plantae and Animalia.
This progression in classification systems illustrates the expanding knowledge in biology and the continuous effort to categorize life in a meaningful way.