1.Five kingdom classification of life
In the year 1969, Robert H Whittaker proposed a five kingdom classification in which he suggested the creation of a new kingdom called Mycota to include exclusively the fungi, since they differ from any other group of plants in their mode of nutrition and reproduction. This five kingdom classification is in agreement with the phylogenetic relationships among organisms. Hence, it has found wide acceptance among taxonomists all over the world.
The present trend in biology is to follow the five kingdom classification proposed by R. H Whittaker in the year 1969. Whittaker classified the living organisms into five kingdoms namely.
1. Kingdom: Miners(Prokaryotic organisms)
2. Kingdom: Protests(Primitive eukaryotic unicellular organisms)
3. Kingdom: Mycota(eukaryotic, non chlorophyllous plants)
4. Kingdom: Metaphyta(advanced eukaryotic chlorophyllous plants)
5. Kingdom: Metazoa(eukaryotic, multicellular animals)
According to this classification, Monera represent the earliest group of organisms. The monera are thought to have given rise to protista from which the three other kingdoms of organisms fungi, plants, and animals evolved along separate lines. Fungi were the first to appear from protista. Later, about a billion years ago some protists must have evolved into primitive multicellular animals. Still later, probably about 350 million years ago, some protists must have evolved into higher forms of plants.
Merits and Demerits of Five Kingdom classification
The five kingdom classification has certain merits and demerits. However, it is largely the most accepted system of modern classification mainly because of the phylogenetic placing of different groups of living organisms.
2.Merits of five kingdom classification
- Separation of prokaryotes into an independent kingdom is justifiable, because they differ from all other organisms in their general organization.
- Grouping of all unicellular eukaryotes under the kingdom protista has solved many problems, particularly related to the position of organisms like Euglena.
- Elevation of group fungi to the status of a kingdom is justifiable since fungi totally differ from other primitive eukaryotes like algae and protozoans.
- The kingdoms metaphyta and metazoa are now more homogenous groups than they were in the two kingdom classification.
- The five kingdom classification gives a clear indication of cellular organization and modes of nutrition, the characters which appeared very early in the evolution of life.
3.Demerits of five kingdom classification
- The kingdom monera and protista include diverse, heterogeneous forms of life. In both the kingdoms there are photosynthetic as well as non-photosynthetic organisms.
- Both the kingdoms include organisms which have cells with cell wall as well as without cell wall.
- None of three higher kingdoms include a single ancestor of all its forms. Multicellular lines have originated from protista NS several times.
- Unicellular green algae have not been included under protista because of their resemblance to other green algae..
- Slime molds differ totally from other members of protista in their general organization.