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What Are the Taxonomic Kingdoms?

Linnaeus was the first person to develop a system of classifying the life on Earth. There were only two categories in this first system: plants and animals. It was only with the invention of the microscope that smaller organisms were discovered, as well as subtle differences in individual cells. This meant that further categories needed to be devised, as well as a method of placing organisms in the correct kingdom. This depends on the cell type of an organism, its ability to produce food and the number of cells in its body.

Monera
- This kingdom is made up of single-celled organisms such as bacteria and blue-green algae. The organisms in this category are made up of simple, or prokaryotic, cells, which have no recognizable structure within the cell membrane. Increasingly, this kingdom is being divided into two separate kingdoms, Eubacteria and Archaebacteria. This is due to single-celled organisms being found in some of the harshest and most inhospitable environments on the planet, such as boiling water and thermal vents, with no oxygen or highly acidic surroundings. These Archaebacteria have a slightly different chemical composition to Eubacteria.
Protista
- The Protista kingdom consists of single-celled organisms that are eukaryotic, or complex. This means that the cell has different sections, or organelles, inside it, which all have a different purpose. They also have a distinct nucleus. This kingdom is incredibly diverse and includes various types of algae.
Fungi
- Fungi are multi-celled organisms made up of many complex cells. This group used to be included within the plant kingdom until it was realized that fungi cannot make their own food like plants can; they absorb food from decaying plants in the soil. Organisms included in this category are mushrooms, mildews, yeasts and molds.
Plantae
- To qualify as a member of the plant kingdom, an organism must be made of many specialized complex cells. It is only able to move if blown by the wind; it has no physical way of moving by itself. Members of the plant kingdom also make their own food by means of photosynthesis. As the second largest kingdom, it includes over 250,000 species, including mosses, ferns, flowering plants and trees. Without the plant kingdom, there would be no other life on Earth.
Animalia
- The animal kingdom is by far the biggest kingdom, with more than 1.3 million known species. These organisms are made of many complex cells, and cannot produce their own food. They are known as heterotrophs, meaning they are organisms that need to eat other organisms in order to survive. Animals are also able to move by themselves. This kingdom includes organisms that live in the most diverse environments: insects, fish, amphibians, reptiles, birds and mammals.

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