Classification of living things

How are living things classified?

The current classification of living things includes three domains and seven kingdoms. The domains group living beings by their cellular characteristics. The kingdoms group them by their evolutionary kinship. The classification system for living beings is structured as follows:

1. Domain Eukarya, contains five kingdoms, which are:

  • Kingdom Animalia
  • Kingdom Plantae
  • Kingdom Fungi
  • Kingdom Protozoa
  • Kingdom chromist or chromist

2. Bacteria Domain, contains the bacterium kingdom.

3. Domain Archaea, contains the kingdom archaea.

Living beings are all organisms with complex structures that are born, grow, reproduce and die. Given their variety and complexity, they are classified into various taxonomic categories for study.

In many parts of the world, the Robert Whittaker classification system, which grouped living beings into five kingdoms (Monera, Fungi, Protista, Plantae and Animalae), is still used in an erroneous way. However, the correct (and current) model is that of the three domains, proposed by Carl R. Woese in 1977.

Domain Eukarya

The Dominion Eukarya It is made up of all living beings that have eukaryotic cells, which have a differentiated nucleus, protected by a membrane and with an organized cytoplasm. Some eukaryotes have mitochondria, organelles that generate energy.

The Eukarya domain is considered the most important, since the best known kingdoms derive from there: Animalia, Plantae, Fungi, Chromista Y Protozoa.

Kingdom Animalia

It is made up of all animals or multicellular organisms that develop from a zygote. They are classified into two large groups:

  • Vertebrates: have a bone structure (fish, amphibians, birds, reptiles and mammals)
  • Invertebrates: they lack vertebrae (arthropods, mollusks, porifers, cnidarians, echinoderms, flatworms, nematodes and annelids).

Kingdom Characteristics Animalia

  • Their reproduction can be sexual (like most of the organisms in this kingdom) or asexual, as is the case with porifers (sea sponges) or other organisms.
  • Their nutrition is heterotrophic, that is, they depend on other organisms to live.
  • Their metabolism is aerobic, they require oxygen to live.
  • They are symmetrical: their structure that starts from an axis and is divided into two equal parts.
  • They can move, either permanently (like humans) or temporarily, like corals, which stop moving when they reach adulthood.

Examples from the Animalia kingdom

  • The goldfish (Carassius auratus).
  • The Andean condor (Vultur gryphus).
  • The squid (Teuthida).
  • The tapeworm was lonelyTaenia solium.
  • The human beinghomo sapiens).

See also Animalia Kingdom.

Kingdom Plantae

It is made up of all plants, which are eukaryotic multicellular organisms. In turn, the kingdom Plantae has two large groups:

  • Non-vascular plants: they lack a nutrient transport system. They do not have roots, stems or leaves.
  • Vascular plants: they have a differentiated vascular tissue, and have roots, stems and leaves.

Kingdom Characteristics Plantae

  • They are autotrophic organisms, that is, they generate their own food (through photosynthesis).
  • They cannot move.
  • Their metabolism is aerobic: they breathe oxygen and expel carbon dioxide.
  • They may or may not have seeds.
  • They may or may not have flowers.

Examples of the kingdom Plantae

  • Ferns (Philicopsids).
  • The orchids (Orchidaceae).
  • The orange tree or orange tree (Citrus × sinensis).

See also Kingdom Plantae

Kingdom Fungi

To the kingdom Fungi all mushrooms, yeasts and mold belong, which are multicellular organisms that generally thrive in humid and aquatic environments. It is classified into three types:

  • Symbionts: are organisms that have a mutually beneficial relationship with other organisms.
  • Saprophytes or decomposers: they feed on the remains of other living beings in decomposition.
  • Parasites: they feed on organic matter generated by other living beings.

Kingdom Characteristics Fungi

  • They reproduce asexually, using spores.
  • They feed by pinocytosis or phagocytosis, degrading compounds into micromolecules.
  • Some organisms of the fungi kingdom are edible, such as certain types of mushrooms and champignons.

Examples from the Fungi kingdom

  • The yeast used in baking to create sourdoughs.
  • The mushroom Candida, which generates infections in the skin and mucosa of humans.

See also: Kingdom Fungi

Kingdom Protozoa (protozoa)

The protozoan kingdom includes all eukaryotic organisms that cannot be considered animals, plants or fungi.

Kingdom Characteristics protozoa

  • They are eukaryotic unicellular beings.
  • Its nutrition can be heterotrophic, autotrophic or through photosynthesis.
  • They have the ability to move.
  • Its reproduction is asexual.
  • Their metabolic process is aerobic, they require oxygen to live.
  • They do not have a cell wall, so their shape is changeable.

Examples of the Protozoa kingdom

  • Amoeba or amoeba, parasite that causes amoebiasis or amoebiasis.
  • Trypanosoma (Euglenozoa), an intracellular parasite.
  • Giardia (Metamonada), the parasite that causes the disease giardiasis.

Kingdom Chromista (chromists)

The chromist or chromist kingdom is formed by unicellular algae. This means that living beings in the chromistic kingdom cannot form tissues with each other, but they are capable of photosynthesis.

Kingdom Characteristics Chromista:

  • Its organization is unicellular.
  • Its cells are eukaryotic.
  • They can reproduce sexually or asexually.
  • Their diet can be of different types.
  • Its mobility is varied.

Examples of the Chromista kingdom

  • Brown algae, which usually live on rocky shores.
  • Diatom algae, found anywhere there is water (seas, rivers, lakes and rainforests).

It may interest you; Eukaryotic cell

Domain or superkingdom Bacteria

The Bacteria domain is made up of prokaryotic organisms, that is, organisms whose cells lack a differentiated nucleus. For now, all beings in this domain belong to the bacterium kingdom.

Bacteria Kingdom

The beings of the bacterium kingdom do not have a nucleus or organelles inside the cell.

Characteristics of the Bacteria kingdom

  • Its DNA is called a nucleoid, and it is found in the cytoplasm of its only cell.
  • They lack locomotion, some have organelles to move around and others remain immobile.
  • Their reproduction is asexual and they require the duplication of their genetic material to perpetuate themselves.
  • Bacteria are pleomophic organisms, that is, the same species can take several forms.

Examples of the Bacteria kingdom

  • The Escherichia coli, found in the human digestive tract.
  • The Idonella sakaiensis, a bacterium that has the property of degrading plastic.

Dominion or super realm Archaea

It encompasses unicellular prokaryotic organisms without a differentiated nucleus, as well as bacteria. However, they are living beings with genetic and metabolic characteristics that are closer to eukaryotic organisms, although their evolutionary path is completely different. They can be present in the water of the oceans, in different types of soil and even in the human digestive tract. The Archaea domain or superkingdom contains the Arquaea kingdom.

Kingdom Arquaea

The microorganisms of the kingdom Archaea have unique characteristics that put them somewhere between the domains Eukarya Y Bacterium.

Kingdom Characteristics Archaea

  • They have a very wide nutritional variety: they feed on hydrogen, sugars or ammonia.
  • They can use carbon or sunlight for energy.
  • They reproduce asexually, after duplicating their DNA.
  • Pathogenic archaea are not known: their form of biological interaction is not harmful to other organisms.

Examples of the Archaea kingdom

  • The Mhetanosarcin, a type of archaea that produces methane.
  • The Ignicoccus, an archaea that lives in marine hydrothermal vents.

See also

  • What are living things?
  • Kingdoms of nature
  • Prokaryotic cell

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