The Whittaker classification divides living beings into the kingdoms Monera, Protista, Mycota (Fungi), the kingdom Metaphyta (Plantae) and the kingdom Metazoa (Animals).
In 1969, Robert H. Whittaker proposed a classification of organisms in five kingdoms. Such classification has survived to this day. However, some modifications have been made to make it more accurate.
The 5 kingdoms of nature
He Monera kingdom is composed of primitive, microscopic and unicellular organisms. These organisms are made up of prokaryotic cells.
Some examples are bacteria and archeobacteria. Currently this kingdom has been divided into two groups: the kingdom Archaebacteria and the kingdom Eubacteria.
He protist kingdom is composed of unicellular eukaryotic organisms. Includes unicellular algae and protozoa like amoebae.
He Mycota kingdom is formed by organisms that create networks called mycelium. These organisms can be saprophytes, parasites or symbionts. At present, this group is known by the name of Fungi kingdom.
He Metaphyta kingdom comprises multicellular eukaryotic organisms. These organisms are autotrophs, since they synthesize their own food through the photosynthesis . Today, this kingdom is called Plantae.
Finally, the Metazoa kingdom is composed of multicellular eukaryotic organisms. Unlike the previous group, these individuals are not able to produce their own food, so they are heterotrophs. Currently, this is the kingdom Animalia.
The Five Kingdoms of Whittaker
In 1957, Robert Whittaker began to develop his classification system. At first, he organized individuals into a three-kingdom system, which challenged the traditional plant-animal dichotomy.
This classification was based on the trophic levels of nature. In this way, Whittaker grouped the organisms into producers (plants), consumers (animals) and decomposers (fungi and bacteria).
Shortly thereafter, he added two more kingdoms, completing the system that is currently known.
This pentapartite system attracted the attention of biologists and other scientists because it took into account the fundamental properties of living beings : cell structures, number of cells, mode of feeding and way of life.
Monera Kingdom
The kingdom Monera was the last kingdom that Whittaker proposed. In this group all prokaryotic unicellular organisms (with cells without nuclei) were grouped.
The creation of this kingdom was justified by the differences between eukaryotic and prokaryotic organisms.
protist kingdom
In the Protista kingdom, Whittaker grouped all unicellular eukaryotic organisms. He recognized that the organisms of this kingdom resembled the organisms of the three higher realms.
However, he justified his decision by pointing out that the difference between unicellular and multicellular was significant enough for the unicellular to form a separate realm.
Within the Protista kingdom, Whittaker included a subgroup in which the bacteria were found.
Kingdom Mycota
For Whittaker, the Mycota kingdom was composed of multicellular eukaryotic organisms.
Before Whittaker, the organisms of the Mycota kingdom were classified as plants. However, the cell of these organisms lacks chloroplasts and chlorophyll, so they are unable to produce food.
In contrast, these are heterotrophic and are fed by absorbing substances in a state of decomposition or other organic matter present in the soil.
The members of this kingdom according to Whittaker were yeasts, molds and fungi.
Kingdom Metaphyta
In the Metaphyta kingdom, Whittaker grouped eukaryotic organisms, with cell walls and chloroplasts in their cells. The fact of having chloroplasts makes these individuals autotrophs (producers).
Gymnosperms, bryophytes and ferns were the first individuals to be part of this group.
Subsequently, it included red and brown algae in this kingdom. He justified this decision by stating that algae played the same role in marine ecosystems as plants in terrestrial ecosystems. For Whittaker, algae were"functional plants".
Metazoa Kingdom
In the Metazoa kingdom, it included eukaryotic organisms with cells without cell walls and lacking chloroplasts. Since they do not present chloroplasts, these organisms are heterotrophs (consumers).
Whittaker classified sponges, invertebrates and vertebrates under this group.
Ranking points in Whittaker's ranking
1 - The classification of Whittaker groups the organisms taking into account scientific criteria, derived from the observation of the different characteristics of these.
2-The Whittaker classification system takes into account:
- The complexity of the cellular structures: if they are eukaryotic organisms (with the genetic information contained in defined nucleus) or of prokaryotic organisms (without nucleus, the genetic information is dispersed in the cytoplasm of the cell).
- The complexity of organisms: whether they are unicellular individuals (formed by a single cell) or multicellular individuals (formed by two or more cells).
- Nutrition mode: if they are autotrophic or heterotrophic.
- Way of life (trophic levels): if they are producers (like plants), consumers (like animals) or decomposers (like fungi).
3 - The separation of organisms according to the system of organization of the same makes it widely accepted in the scientific world:
- Prokaryotes form part of an independent kingdom, since they are so primitive that they do not resemble the individuals of the other realms.
- The unicellular eukaryotic organisms are grouped in the Protista kingdom, eliminating the complications that generate the similarities these and the plants and the animals.
- Fungi are not as primitive as the organisms of the Protista kingdom. Nor do they produce their own food like plants. For this reason, it is justified that there is a separate kingdom for these individuals.
- Plants are able to produce their own food through photosynthesis.
- Animals feed on other organisms, so they are heterotrophs.
Problems with Whittaker's classification
1-The primitive forms of life are not organized properly:
- The Monera kingdom and the Protista kingdom include heterogeneous forms of life.
- In these two kingdoms are found both autotrophic and heterotrophic organisms, organisms with and without cell wall.
2-This system does not propose a suitable classification for viruses or molds.
References
- Five Kingdom Classification Proposed by R. H. Whittaker. Retrieved on September 5, 2017, from biologyexams4u.com
- Hagen, Joel (2012). Five Kingdoms, More or Less: Robert Whittaker and the Broad Classification of Organisms. Retrieved on September 5, 2017, from academic.oup.com
- Robert Whittaker. Retrieved on September 5, 2017, from wikipedia.org
- Five Kingdoms Classification. Retrieved on September 5, 2017, from biology.tutorvista.com
- Classification of Living Organism: Whittaker classification. Retrieved on September 5, 2017, from web-formulas.com
- Margulis (1971). Whittaker's Fice Kingdoms of Organisms. Retrieved on September 5, 2017, from jstor.org
- Biological Classification. Retrieved on September 5, 2017, from ncert.nic.in