What Is The 5 Kingdom System Of Classification? - Discover It Here! (2024)

All living organisms are classified into five kingdoms, from small bacteria to humans. This classification holds fundamental foundations which scientist Robert Whittaker established. They have also contributed enormously to the study of living beings on earth.

Do you want to know more about the 5 kingdom classification system? In this AnimalWised article we will explain what the 5 kingdom of living things is, as well as describe its main characteristics.

Robert Whittaker was an renowned plant ecologist from the United States. He focused specifically on ​​plant community analysis. He was the first person to propose that all living beings be classified into five kingdoms. Whittaker relied on two fundamental characteristics for this classification:

• Classification of living beings according to their diet: Living beings can be classified depending on whether this organism feeds through photosynthesis, by absorption or by intake. Photosynthesis is the mechanism that plants use to absorb carbon from the air and produce energy. Absorption is the feeding method of, for example, bacteria. And intake is the action of receiving nutrients through the mouth.

• Classification of living beings according to their level of cellular organization: You can find; prokaryotic organisms, unicellular eukaryotes and multicellular eukaryotes. Prokaryotes are unicellular organisms, which means they are formed by a single cell and are characterized by no nucleus in their interior. Their genetic material floats inside the cell. Eukaryotic organisms can be unicellular or pluricellular beings (formed by many cells), its main characteristic is that its genetic material resides in a nucleus structure, inside the cell or cells.

Uniting the characteristics that make up the two previous classifications, Whittaker classified all living beings into five kingdoms: Monera, Protista, Fungi, Plantae and Animalia.

The Monera kingdom includes unicellular prokaryotic organisms. Most feed through absorption, but some perform photosynthesis, like the bacteria cyanobacteria.

Within the Monera kingdom we find two sub-kingdoms:

1. The archaebacteria: which are microbes that live in extreme environments. For example, places with very high temperatures, such as hydrothermal vents that exist in the ocean floor.
2. The sub-kingdom of the eubacteria: We can find eubacteria in almost any environment on the planet, they play important roles in the life of Earth, some even producing diseases.

The Protista kingdom includes: unicellular eukaryotic organisms and some simple multicellular organisms. There are three main sub-kingdoms of protists:

• Algae: unicellular or pluricellular aquatic organisms that carry out photosynthesis. They vary in size from microscopic species such as micromonas to giant organisms that reach 60 meters in length.
• Protozoa: are mainly unicellular organisms,are mobile and feed by absorption (like amoebas). These are presented in almost all types of habitats and include some pathogenic parasites of humans and domestic animals.
• Protist fungi: protists absorb their food from dead organic matter. They are grouped into 2 groups, slime molds and water molds. Most mushroom-like protists use pseudopods ("false feet") to move.

The Fungi kingdom is composed of multicellular eukaryotic organisms, they feed through absorption. They are decomposer organisms which secrete digestive enzymes and absorb small organic molecules released thanks to enzymes. In this kingdom you can mostly find all kinds of mushrooms.

The Plantae kingdom includes multicellular eukaryotic organisms that perform photosynthesis. Through this mechanism, plants produce their own food, by absorbing carbon dioxide and water. Plants do not have a solid skeleton, therefore each of their cells have a wall that keeps them firm.

Plants also have sexual organs that are multicellular which form embryos during their life cycles. The organisms, include; mosses, ferns and flowering plants.

The Animalia kingdom is composed of multicellular eukaryotic organisms. They feed through ingestion. They take food and digest it through specialized cavities inside the body, such as; the digestive system of vertebrates. None of the organisms in the Animalia kingdom have a cell wall like plants do.

The main characteristic of animals is that they have the ability to move from one place to another, more or less voluntarily. All the animals on our planet belong to this group: from marine sponges to dogs or humans.

Discover everything you need to know about animals here at AnimalWised, and take a look at our articles on herbivorous dinosaurs to carnivorous animals.