The Five Kingdom Classification

Robert Harding Whittaker was an American plant ecologist from the 1950s to the 1970s. He was the first to propose The kingdom classification of the world’s biota into the Animalia, Plantae, Fungi, Protista, and Monera in 1969. He also proposed the Whittaker Biome Classification, which categorized biome types upon two abiotic factors: temperature and precipitation.

R.H. Whittaker initially proposed the five-kingdom classification in 1969. This classification was based on specific characteristics, such as the means of nourishment, the arrangement of the thallus, the structure of the cells, the evolutionary relationships, and the reproductive process. This particular classification system recognizes five different kingdoms:

Classification Definition

The arrangement of collecting organisms into groups or sub-group based on similarities and changes is called classification. It provides an easy way to investigate many types of organisms or their life forms in an extremely simple way.

Kingdom Monera

Bacteria are placed in the “Kingdom Monera” category within the Five kingdom classification system.

Characteristics of Monerans

They have essential characteristics such as the following:

• Bacteria can be found in any environment and are quite small in size.
• They are prokaryotic and have a cell wall to protect themselves.
• Amino acids and polysaccharides support the formation of the cell wall.
• Both heterotrophic and autotrophic metabolic processes can be found in bacteria.
• Both parasitic and saprophytic lifestyles are possible for heterotrophic bacteria. 
• Chemosynthetic and photosynthesis are both possible metabolic pathways for autotrophic bacteria.
• Bacteria, Cyanobacteria, and Mycoplasma are Examples of Kingdom Monera.

Monerans Types

Bacteria are separated into four distinct categories according to their morphology, which is as follows:

• Coccus also referred to as cocci, are bacteria that have a spherical shape.
• Bacillus, also called bacilli, refers to a rod-shaped genus of bacteria.
• Some bacteria are called vibrio (plural: Vibrium) and have the shape of a comma.
• Spirillum, also called spirilla, is the plural form of this genus of spiral-shaped bacteria.
• Archaebacteria and Eubacteria were once classified within the genus Monera but have recently been separated.

Kingdom Protista

character of Protista

• They are organisms that are both unicellular and eukaryotic in structure.
• Several of them move around through cilia or flagella.
• Cells must fuse to produce zygotes during the process of sexual reproduction.
• Diatoms, Protozoans like Amoeba, and Paramecium are Some examples of kingdom Protista.

Kingdom Fungi

Characteristics of the Fungal Kingdom

Kingdom Plantae

Features of Kingdom Plantae

• All eukaryotic organisms that include chloroplasts are categorized within the Plantae kingdom.
• The nature majority of them are autotrophic, but some are heterotrophic.
• The majority of the cell wall is made up of cellulose.
• The lifecycle of a plant can be split into two separate stages. 
• These phases follow one another in an alternating fashion. 
• The haploid gametophytic phase and the sporophytic phase are diploid. The duration of the diploid and haploid phases differ from one group of plants to another due to their genetic diversity. This phenomenon is referred to as the Alternation of Generation.
• Spirogyra, Ferns, Pines, and Mango Plant are some examples of kingdom Plantae.

Kingdom Animalia

The character of Kingdom Animalia

• This kingdom is assigned to all multicellular eukaryotic organisms that consume heterotrophic food sources and do not possess a cell wall.
• The animals’ ability to eat directly or indirectly depends on the plants. Their mode of nutrition is the holozoic. Ingestion of food is the first step in the holozoic nutrition process, followed by the utilization of an internal cavity for the digestion of food.
• Many animals can show locomotion.
• They have a sexual mode of reproduction.
• There are several different phyla and classes that make up the Animal Kingdom.
  Porifera, Coelenterata, Arthropoda, Echinodermata, Chordata, and other taxonomic divisions are examples of phyla. The Hydra, Starfish, Earthworms, Monkeys, and Birds are just a Few Examples.

Advantages of Whittaker’s Five Kingdom

• The first and most significant benefit of this five-kingdom classification is that it separates the prokaryotes into their kingdom, which is named monera. Because of genetic, cellular, reproductive, and physiological differences, prokaryotes can be distinguished from eukaryotic organisms.
• The fungus is placed in its independent kingdom within Whittaker’s Five Kingdom classification system, which further differentiates them from plants. The fungi’s biochemical, physiological, and structural organization are all completely distinct.
• This categorization places unicellular eukaryotic organisms in the kingdom Protista; we are better able to discriminate between the various types of these organisms.
• The five-kingdom classification is based on different levels of organization and nutrition that developed very early on and became established in subsequent groups still alive today.
• Compared to the two-kingdom classification, the plant and animal kingdoms of the five-kingdom classification are more similar to one another than in the two-kingdom classification.
• Whittaker’s Five Kingdom classification reveals evolutionary links even among primitive organisms.

Limitations or Objections to the Five Kingdom System of Classification

• Some scientists in the scientific community think that protozoa and algae do not fit in the same kingdom.
• Protozoa are categorized as a subkingdom of the Animal Kingdom in a number of different taxonomic systems.
• In this classification system, it is not possible to distinguish between unicellular and multicellular organisms in the case of algae.
• Because each group has so many diverse individuals, it might be challenging to keep them all together. For Example, the Kingdom Monera and Protista include both species with and without cell walls. Cellular and filamentous organisms, photosynthetic and nonphotosynthetic.
• This kingdom does not include the virus.
• Archaebacteria are distinguished from other bacteria by their distinctive differences in form, composition, and physiology.
• Mycoplasma is very distinct from bacteria, despite the fact that they have been classified in the same group as bacteria.
• In this particular classification scheme, symbiotic relationships are not considered. For Example, lichens are organisms produced when fungi and algae work together in a mutually beneficial relationship.

Frequently Asked Questions about The Five Kingdom Classification System