HAECKEL THREE KINGDOM CLASSIFICATION
· In 1866, the
German investigator Ernst Haeckel proposed a Three Kingdom System of
Classification based on morphological complexities and tissue system, the
division of labor, and mode of nutrition.
· Three kingdom
classification system was put forward by Haeckel in order to overcome the
objections and limitations of the Two Kingdom Classification.
· Unicellular
animals, algae and fungi were separated from other organisms on the basis of
lack of tissue differentiation.
·
The new
group was called the kingdom Protista.
· Organisms
lacking morphological complexities, tissue system, the division of labor, and
enjoying the diversified type of modes of nutrition were segregated and put
under the kingdom Protista.
·
Haeckel’s Three
Kingdoms were Animalia, Plantae and Protista.
a)
Kingdom Animalia includes Multicellular animals (Metazoan)
b)
Kingdom Plantae includes Multicellular plants (Metaphyta)
c)
Kingdom Protista
includes the Protozoa, Fungi, Bacteria, Algae and Slime molds.
·
Later Fungi and
multicellular Algae were taken out from the group.
· According to Three
Kingdom Classification, all known microorganisms came to be recognized as Protists;
neither plants nor animals.
Merits of Three Kingdom
Classification
·
Recognition of
the importance of the microorganisms in the living world.
·
More characters
were taken into consideration to classify the living beings.
Demerits of Three Kingdom
Classification
· Haeckel’s
system was not widely accepted and microorganisms continued to be classified as
plants (for example, bacteria and fungi) or animals (for example, protozoa).
·
Nucleated
(Eukaryotes) and Anucleated (Prokaryotes) organisms kept together in protists.
·
Heterotrophic
bacteria and fungi placed along with autotrophic algae.
· Viruses have not been included in this system of classification as it shows characters of both living and non- living things.
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