All living organisms are classified into five kingdoms, from small bacteria to human beings. This classification has some fundamental bases established by the scientist Robert Whittaker and who has contributed enormously to the study of the beings that live on Earth.
Whittaker's Five Kingdoms
Robert Whittaker was a leading plant ecologist in the United States. He focused on the area of analysis of plant communities. She was the first person to propose that all living things be classified into five kingdoms. Whittaker relied on two fundamental characteristicsto classify him:
- Classification of living beings according to their nutritionn: depending on whether the organism feeds through photosynthesis, by absorption or by intake. Photosynthesis is the mechanism that plants have to take carbon from the air and produce energy. Absorption is the feeding method of, for example, bacteria. And intake is the action of taking in nutrients through the mouth.
- Classification of living beings according to their level of cellular organization: we find prokaryotic organisms, unicellular eukaryotes and multicellular eukaryotes. Prokaryotes are unicellular organisms, that is, formed by a single cell and are characterized by not having a nucleus inside, their genetic material is found floating inside the cell. Eukaryotic organisms can be unicellular or multicellular beings (made up of many cells), their main characteristic is that their genetic material is found in a structure called the nucleus, inside the cell or cells.
Joining the characteristics that make up the two previous classifications, Whittaker classified all living beings into five kingdoms: Monera, Protoctista, Fungi, Plantae and Animalia.
1. Kingdom Monera
Kingdom Monera includes single-celled prokaryotic organisms. Most feed by absorption, but some photosynthesize like cyanobacteria.
Within the kingdom Monera we find two sub-kingdoms, that of archaebacteria which are microbes that live in extreme environments, for example places with high temperatures very high, such as the hot water chimneys that exist on the ocean floor. And the subkingdom of eubacteria We can find eubacteria in almost any environment on the planet, they play important roles in life on Earth and some cause diseases.
two. Kingdom Protoctista or Protista
This kingdom includes organisms single-celled eukaryotes and some multicellular organismssimple. There are three main subkingdoms of protists:
- Algae: unicellular or multicellular aquatic organisms that carry out photosynthesis. They range in size from microscopic species such as micromonas to giant organisms reaching 60 meters in length.
- Protozoa: Primarily single-celled, motile, absorptive-feeding organisms (such as amoebae) that are represented in almost all types of habitats and include some pathogenic parasites of humans and domestic animals.
- Protist Fungi: Protists that 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.
3. Fungi kingdom
The Fungi kingdom is made up of multicellular eukaryotic organisms, they feed through absorption. They are mostly decomposers, they secrete digestive enzymes and absorb small organic molecules released by the enzymes. All fungi and mushrooms are found in this kingdom.
4. Plantae Kingdom
This kingdom includes the multicellular eukaryotic organisms that carry out photosynthesis. Through this mechanism, plants produce their own food, by capturing carbon dioxide and water. Plants do not have a solid skeleton, so each of their cells has a wall that keeps them firm.
They also have sexual organs that are also multicellular and form embryos during their life cycles. The organisms that we can find in this kingdom are, for example, mosses, ferns and flowering plants.
5. Animalia Kingdom
This kingdom is made up of multicellular eukaryotic organisms They feed by eating, taking in food and digesting it in specialized cavities within the body, such as the digestive system of vertebrates. None of the organisms in this kingdom have a cell wall, as occurs with plants.
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 the planet belong to this group, from sea sponges to dogs or humans.
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