Robert system which consists of Monera, Algae, Fungi,

Robert H. Whittaker proposed the
Five kingdom classification system which consists of Monera, Algae, Fungi,
Plantae and Animalia in 1957. He has utilized a few criteria to classify his
groupings, which is type of nutrition, type of organism and level of cell

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In 1969 Whittaker published a
revision of his four-kingdom system to expand it to five kingdoms, now
including a separate bacterial kingdom named Monera in recognition of the
fundamental division of life as “prokaryotic” versus “eukaryotic” (as Copeland
did, but expressed as “anucleate” and “nucleate”) 45. This distinction was
first conceived by French protozoologist Edouard Chatton (1883–1947) in 1925 in
an article entitled “Pansporella perplexa: Amoebien a Spores Protégées Parasite
des Daphnies. Réflexions sur la Biologie et la Phylogenie des Protozoaires”,
(Ann Sci Nat Sér X (Zool), 8:5–84, cited by Ragan 35) and again in 1938 in
his own bound works entitled Titres et Travaux Scientifiques 7, 26, 34, 35,
41. Whittaker noted that this concept was now more evident due to the writings
of microbiologist Roger Y. Stanier in 1962 and 1963 41, 42 and that this
evolutionary divergence in cellular structure had to be accounted for by the
recognition of Kingdom Monera 45. Otherwise, Whittaker’s reasoning remained
the same for retaining the other four kingdoms in this Five Kingdom system. He
reasserted his ecological model as well as the belief that inclusion of multicellular
organisms into Kingdom Protista would make the Five Kingdom system an
evolutionarily unnatural, heterogeneous grouping 45. The central
characteristic of Protista: unicellularity, remained




diagnostic of the group, the
same as Haeckel’s Protista was known at the turn of the century. In 1968, just
prior to Whittaker’s publication of his fivekingdom classification, biologist
Lynn Margulis at Boston University proposed a four-kingdom system based upon
the model of Copeland, who was at the time the only researcher to offer a
detailed taxonomic work that recognized the biological discontinuity between
prokaryotic and eukaryotic organisms 23. Differing from Copeland’s
Protoctista, Margulis’ Kingdom Protoctista included the green algae, which she did
not consider plants; this change was considered in light of the theory of
bacterial endosymbioses in the evolution of the Protoctista 23. Increasing
evidence of genetic and ultrastructural nature of mitochondria and plastids
showed these eukaryotic cell organelles having independent bacterial genomes,
and consequently plants and animals themselves were regarded by Margulis as
evidencing a polyphyletic nature, evolving from protoctist ancestors 23.
After Whittaker’s publication of his five-kingdom concept, Margulis
incorporated the phylogenetics of her system with the five-kingdom system and
accepted the kingdom name of Protista instead of Protoctista 24. However,
Margulis’ Kingdom Protista differed from Whittaker’s in that hers contained all
algae (green, brown, red), limiting Kingdom Plantae to the botanical phylum
Embryophyta 24. These modifications were in direct consideration of
endosymbiotic evidence that “protozoans and nucleate algae represent a large
group of organisms with flagellated heterotrophic eukaryote ancestors” 24.
Margulis further viewed the Protista as a heterogeneous grouping of unicellular
and multicellular eukaryotes representing “polyphyletic evolutionary
‘experiments’ leading toward the ultimate establishment of mitosis and regular
meiosis” 24. Relying more upon morphological and ultrastructural comparisons
within the Protista, Margulis departed from Whittaker’s nutritional and
unicellular morphological criteria of the Protista, and led her to accept the
kingdom name Protoctista from Copeland. Plants became defined as the group of
organisms that develop from a multicellular embryo retained in maternal tissue,
then, animals develop from a multicellular blastular stage, fungi as organisms
that develop from spores and lack flagella (today termed as undulipodia) at any
stage of life history. Protoctista were eukaryotic organisms either unicellular
or multicellular that are not plants, animals or fungi 46. Margulis also
introduced the term “protoctist” to refer to an individual organism of the
Protoctista, whether unicellular or multicellular 46. Defining the
Protoctista by exclusion was the extension of sharply defining, or limiting,
the characteristics of organisms in kingdoms Plantae, Animalia, and Fungi. The
fact remained, however, that as a grouping the organisms of Protoctista had
more in common with each other than to the larger plants, animals, or fungi.
Increased research combining genetic (16S rRNA comparisons), biochemical, and
ultrastructural observations of protoctists has evidenced the


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