Aristotle’s classification
- Aristotle was the earliest to attempt a more scientific basis for classification of organisms.
- He classified plants into trees, shrubs & herbs and animals into two groups, those which had red blood and those that did not.
Two-kingdom classification
- In Linnaeus' time Two Kingdom classification (Kingdom
Plantae & Kingdom Animalia) was developed.
Drawbacks of 2-kingdom classification
Prokaryotes (Bacteria, cyanobacteria) and eukaryotes
(fungi, mosses, ferns, gymnosperms and angiosperms) were included under ‘Plants’. It is based on the presence
of cell wall. But prokaryotes and eukaryotes are widely differed in other characteristics.
It included the unicellular and the multicellular organisms in same group. E.g. Chlamydomonas and Spirogyra were placed under algae.
It did not differentiate between the heterotrophic fungi and the autotrophic green plants. Fungi have chitinous cell wall while the green plants have cellulosic cell wall.
Five Kingdom Classification
- It is proposed by R.H. Whittaker (1969).
- It includes Monera, Protista, Fungi, Plantae & Animalia.
- This classification is based on cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships.
Characteristics of the five kingdoms
Characters
Monera
Cell type
Prokaryotic
Non-cellular
Cell wall
(polysaccharide + amino acid)
Nuclear membrane Absent
Protista
Eukaryotic
Body organisation
Cellular
Cellular
Mode of nutrition
Autotrophic
(photosynthetic & chemosynthetic) and heterotrophic (saprophyte/parasite)
Autotrophic
(photosynthetic)
and heterotrophic
Present in some
Present
Five kingdoms
Fungi
Eukaryotic
Plantae
Eukaryotic
Animalia
Eukaryotic
Present (without cellulose) Present
(cellulose)
Absent
Present
Multicellular,
loose tissue
Present
Heterotrophic
(saprophytic or parasitic) Tissue/organ