QVprep Biology Lessons

Systems of classification, Two kingdoms classification, Three kingdoms classification, Four kingdoms classification, Five kingdoms classification



Two kingdoms classification: The classification of living things into animals and plants is an old system of classification. Aristotle classified animal species in his work The History of Animals, and his student Theophrastus wrote a parallel work on plants called ‘Historia Plantarum’ (The History of Plants). Carl Linnaeus who laid the foundations for modern biological nomenclature distinguished two kingdoms of living things: Animals and Plants. He divided each kingdom into classes, which were later grouped as later grouped into phyla for animals and divisions for plants.

Three kingdoms classification: Microorganisms were virtually unknown until the pioneer work and compilation of observations of microbes in different sources by Anton van Leeuwenhoek, considered the father of microscopy. In the year 1866, Ernst Haeckel proposed a third kingdom of life. The third kingdom includes organisms that were unicellular and referred to as Protista.

Four kingdoms classification: More advances in microscopy, and particularly the invention of electron microscopy led to the identification of unicellular as well as multicellular microbes. More importantly, it distinguished prokaryotes without a well-defined nucleus from eukaryotes which had a well-defined nucleus which contained the hereditary material. In 1938, Herbert F. Copeland proposed a four-kingdom classification, combining the two prokaryotic groups, bacteria and blue-green algae, into a separate Kingdom Monera. In the 1960s Stanier and van Niel proposed the creation of a rank above kingdom, a Superkingdom or empire, also called a domain.

Five kingdoms classification: It was Robert Whittaker who recognized the need for a separate, additional kingdom for the Fungi. The resulting five-kingdom system, proposed in 1969 by Whittaker, has become a popular standard and is also the basis for more recent multi-kingdom systems. This system of classification is mainly based on differences in nutrition; A) Kingdom Plantae consisted mostly of multicellular autotrophs B) Kingdom Animalia consisted of multicellular heterotrophs C) Kingdom Fungi consisted of multicellular saprotrophs D) The remaining two kingdoms, Protista and Monera, included unicellular and simple cellular colonies.