The kingdoms of nature are a level of classification of living beings, according to their line of evolution. Currently there are seven kingdoms of living beings:
- Kingdom Animalia (animals)
- Kingdom Plantae (plants)
- Kingdom Fungi (mushrooms)
- Kingdom Protozoa (protozoans)
- Chromista Kingdom (chromists)
- Kingdom Archaea (archaea)
- Kingdom Bacteria (bacteria)
This classification was proposed in 2015 by a group of researchers, under the direction of Michael Ruggiero.
7 Kingdoms Of Nature:
In this new system, two new categories appear: the chromists (which were dispersed among protozoans, algae and plants) and the archaea (which belonged to the kingdom monera).
Protozoans, which previously made up the kingdom Protista, now become the kingdom Protozoa. Bacteria have their own kingdom, which in the 1969 classification was named Monera.
Below, we present each kingdom with its characteristics and examples of the organisms that make it up.
1. Kingdom Animalia (animals)
The kingdom Animalia or kingdom of animals is made up of multicellular organisms, made up of cells with a nucleus. These are complex living beings, with specialized tissues and organs to perform different functions.
Animals can roughly be divided into two large groups, according to the presence or absence of a central column or vertebral column. Vertebrates , such as fish, frogs , reptiles, birds and mammals, have a spine and a skull. Invertebrates , such as insects, mollusks, and worms, lack an internal framework .
Examples of organisms from the animal kingdom are the southern right whale ( Eubalaena australis ), the sea turtle ( Chelonioidea sp. ), the flag macaw ( Ara macao ), the lion ( Panthera leo ) and the human being ( Homo sapiens ), among others. .
Characteristics of the animal kingdom
- They are eukaryotes : organisms in the animal kingdom are made up of eukaryotic cells, a type of cell that has an internal structure composed of a membrane called the nucleus. The genetic information of the species is stored in the nucleus.
- They are multicellular : even the simplest animals are composed of multiple cells, with different characteristics and functions.
- Cells do not have a cell wall : animal cells, unlike fungi and plants, do not have a cell wall, a protective structure that is located outside the cell membrane.
- They depend on other living beings for their nutrition : that is, they are heterotrophs. Animals must consume other living things, such as plants, fungi, and other animals, in order to obtain the materials and energy they need to live.
- They digest their food in an internal cavity : Most animals have to ingest their food to digest it internally. In the case of humans, this takes place in the digestive system.
- They reproduce sexually : animals produce specialized cells called gametes, which fuse to generate a new individual in the species.
- They move by contraction of fibers : organisms in the animal kingdom move by specialized cells that can contract and relax. In mammals these cells form muscles.
2. Kingdom Plantae (plants)
The kingdom Plantae or plant kingdom is composed of multicellular organisms, made up of cells with a defined nucleus (eukaryotic), where the genetic material is stored. Plants are capable of producing complex organic molecules from simple compounds, using the energy of sunlight, through the process of photosynthesis.
Examples of organisms in the kingdom Plantae are the moon orchid ( Phalaenopsis amabilis), the redwood ( Sequoia sempervirens ), the pine ( Pinus ), the lemon tree ( Citrus x limon ), and the tea tree ( Camellia sinensis ).
Characteristics of the plant kingdom
- They are eukaryotes : like animals, plants are made up of cells that have a nucleus where the genetic material is found.
- They are multicellular : a plant is an organism made up of multiple cells, which are responsible for various functions, such as root cells and leaf cells.
- The cells are protected by a cell wall : the plant cell has on the outside a structure made of cellulose, called the cell wall. This wall becomes stronger in the bark of trees, thanks to lignin.
- They are self-sufficient : they carry out photosynthesis, a process by which organic compounds are produced from carbon dioxide and sunlight. That is why plants are autotrophic organisms.
- They do not move : plants grow fixed to a substrate, in the case of terrestrial plants, or floating in the case of some aquatic plants.
3. Kingdom Fungi (fungi)
They belong to the kingdom Fungi , or kingdom of fungi, unicellular or multicellular organisms, formed by eukaryotic cells, incapable of photosynthesis, which have lost the ability to phagocytose.
Fungi can form symbioses with plants and algae, from which they obtain the nutrients they need. However, they can also parasitize other organisms,
Fungi play a key role in the flow of matter in ecosystems. These degrade dead organic matter, releasing compounds that can be reused by other organisms, such as plants.
Examples of the Fungi kingdom are found in mushrooms ( Agaricus bisporus ), the molds that appear on bread and fruits, the painted or false oronja (Amanita muscaria ), the penicillin-producing fungus ( Penicillium chrysogenum), the Trichophyton fungus. rubrum (causing agent of the skin infection commonly called “athlete’s foot”) and scarlet copica ( Sarcoscypha coccinea ).
Characteristics of the mushroom kingdom
- They are eukaryotic beings : fungal cells have a nucleus where the genetic material is found.
- They can be unicellular or multicellular : within fungi there are yeasts, which are single-cell organisms that can be seen using a microscope. Other fungi are visible to the naked eye, such as molds and mushrooms.
- They depend on other beings to obtain their nutrients : fungi, unlike plants, cannot capture sunlight through photosynthesis, therefore they are heterotrophic organisms.
- They obtain their nutrients through external digestion : fungi release enzymes outside that degrade large molecules into small molecules that can enter the cell. For example, cellulase breaks down cellulose and transforms it into glucose, which is then used by the fungus for fermentation.
- They have a cell wall : this is a structure found outside the cell membrane, which prevents dehydration and maintains the shape of the cell. The fungal cell wall is composed mainly of chitosan and glucosan, polymers and amino acids and sugars.
- Its reproduction can be asexual or sexual : yeasts reproduce through budding, generating a new individual. Other fungi produce spores, specialized reproductive cells, that can easily be dispersed, either through air or water.
- They are immobile : fungi do not move, they do not have cilia or flagella that allow them to move in aqueous environments. They also do not have specialized cells that contract.
4. Kingdom Protozoa (protozoans)
The kingdom Protozoa or kingdom of protozoans is made up of unicellular eukaryotic organisms that are not classified in any of the other identified kingdoms. They can be either aerobic or anaerobic, autotrophic or heterotrophic, sexually or asexually reproducing organisms. Hence it is difficult to establish common characteristics in this kingdom.
Organisms that now belong to the kingdom Protozoa were initially classified in Whittaker’s kingdom Protista. Thanks to electron microscopy and nucleic acid sequencing techniques, differences have been recognized in some of these organisms.
Examples of protozoans are Giardia intestinalis , an intestinal parasite, and paramecia ( Paramecium sp. ), microorganisms abundant in stagnant fresh water.
Characteristics of the protozoan kingdom
- They are eukaryotes : protozoans have a defined nucleus within the cell.
- They are unicellular : each individual of a species can live independently as a single cell.
- They are heterotrophs : these organisms cannot synthesize their own nutrients, so they depend on obtaining their food from other organisms, generally bacteria and dissolved organic matter in the environment where they live. The only protozoa that can photosynthesize belongs to the Euglenophyceae, because it enslaves green algae.
- They ingest their nutrients by phagocytosis : this means that protozoans can trap their food through invaginations of the cell membrane, as is the case with amoebas.
- They can move : some protozoans can move using cilia and flagella, structures in the form of hairs or whips that help them propel themselves. Other protozoa, such as amoebas, move because their membrane produces pseudopodia, a type of false feet.
5. Kingdom Chromista (chromists)
Microalgae of the genus Pavlova sp. which are currently cataloged in the Chromista kingdom (Credits: CSIRO).
The Chromista kingdom groups eukaryotic organisms, made up of cells with a nucleus, with the capacity to carry out photosynthesis, which do not share other characteristics with the plant kingdom. The kingdom Chromista includes algae with chlorophyll c.
For a long time these organisms were considered part of the plant kingdom, fungi or the protozoan kingdom. Structural, biochemical and genetic analyzes led them to a new group with its own characteristics.
Chromists were first described in 1981. It was not until 2015 that a kingdom for these organisms was included as part of the general classification of living beings.
Examples of organisms from the kingdom chromista are Diatoms (the most common type of phytoplakton), brown algae (mostly present in the ocean), golden algae ( Chrysophyta ), common algae in fresh water, and foraminifera (microorganisms with an exoskeleton). found in salt water).
Characteristics of the chromist kingdom
- They are eukaryotic beings : like all the previous kingdoms, the kingdom of chromists includes organisms made up of eukaryotic cells with a cell nucleus.
- They present an endoplasmic reticulum chloroplast : it is a membranous structure that continues the nuclear envelope and connects with the chloroplast.
- They can be autotrophs or heterotrophs : although some species have the capacity for photosynthesis, others have lost it in their evolutionary line.
- Asexual and sexual reproduction : they divide by partition, but they can also produce gametes.
- They are mobile : they can present at least one flagellum.
- They present mastigonemas : these are species of lateral hairs that protrude from the flagellum.
- They are pigmented : algae are generally classified by their color or pigment, mainly chlorophyll c.
6. Kingdom Archaea (archaea)
This kingdom is made up of prokaryotic organisms, that is, cells without a defined nucleus, such as bacteria. Genetic studies of the ribonucleic acid of ribosomes showed that archaea were different from bacteria.
Archaea were only recognized at the end of the 20th century. Today it is recognized that these organisms are everywhere, even in the intestines of animals.
In Whittaker’s classification, archaea were part of the kingdom Monera or kingdom of bacteria. In fact, they were recognized as archaeabacteria.
Some examples of microorganisms that belong to the kingdom of archaea are Haloquadratum walsbyi (archaea with a square appearance), Halobacterium (archaea that live in environments with high concentrations of salt), ARMAN ( Archaeal Richmond Mine Acidophilic Nanoorganisms ) are archaea that live in environments acids.
Characteristics of the kingdom of archaea
- They are prokaryotic beings : archaea are cells formed by a cell membrane that surrounds the cytoplasm, where the dispersed genetic material is found. These are prokaryotic cells that do not have a nucleus.
- They are microscopic unicellular beings : archaea are extremely small, observable only with a microscope.
- They develop in extreme environments : one of the difficulties in detecting archaea is that they have the ability to develop in conditions where other forms of life cannot, such as in saline lakes, high-temperature hot springs and very acidic environments.
- They can be autotrophic or heterotrophic : some archaea can generate their energy sources, and can feed on a large number of compounds ranging from sugars to ammonia and hydrogen.
- Asexual reproduction : they reproduce by binary fission, dividing their cytoplasm to generate two new cells.
7. Kingdom Bacteria (bacteria)
Prokaryotic microorganisms belong to this kingdom. Bacteria are the most abundant organisms on the planet. Although they are usually associated with diseases, they also have a fundamental role in the balance of ecosystems, since many species are responsible for degrading the organic compounds present in the soil.
Examples of bacteria of importance to humans are Escherichia coli , (can cause infections in the intestinal tract of animals and humans); lactobacilli (found in the digestive tract of animals and humans, as well as in foods of dairy origin, such as yogurt) and Clostridium botulinum , (cause of botulism).
Characteristics of the bacteria kingdom
- They are prokaryotic organisms : bacterial cells do not have a nucleus. Its genetic material is free in the cytoplasm.
- They are unicellular : each bacteria can live independently of the others. However, under culture conditions, a bacteria can form a colony, which is a cluster of daughter bacteria.
- They have a cell wall : bacteria have an external structure that serves as protection. Depending on the composition of the cell wall, bacteria can be classified as Gram-positive, such as staphylococci, and Gram-negative, such as Escherichia coli . However, there is a type of bacteria that lacks a cell wall, called mycoplasmas.
- They can be autotrophic or heterotrophic : some bacteria can obtain their energy autonomously, through chemosynthesis or photosynthesis, or depend on external sources to survive.
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