Two Kingdom System of Classification
Later, Linnaeus classified all living organisms into two kingdoms — Plantae and Animalia. The criteria for clssification used by him include cell wall, locomotion, mode of nutrition, response to external stimuli and contractile vacuole.
| Features | Kingdom Plantae | Kingdom Animalia |
| 1. Cell Wall
2. Locomotion 3. Mode of Nutrition 4. Responsive to external stimulus 5. Contractile system 6. Organisms |
Present
Absent Do not eat Slow Absent Bacteria, algae, fungi, bryophytes, pteridophytes, gymnosperms, angiosperms |
Absent
Present Eat Fast Present Protozoa, vertebrates, invertibrates |
This two kingdom classification system does not distinguish between —
(i) Unicellular and multicellular organisms,
(ii) Eukaryotes and prokaryotes
(iii) Photosynthetic (green algae) and non – photosynthetic (fungi) organisms.
These are few organisms like Chlamydomonas, Euglena and the slime moulds which share the characteristics of both animals and plants. Since there are many organisms that do not fall naturally into either plant or animal kingdom, it was proposed that a new kingdom is to be established to accommodate such organisms.