Species is understood as the basic unit of classification of living beings , that is, the bottom rung of all forms of biological taxonomy . It is a set of organisms capable of reproducing and obtaining fertile (non-hybrid) offspring, and which share its basic defining evolutionary traits.
Some 1.9 million species of living beings are currently known on our planet , distributed in the various kingdoms of life . Many of them share evolutionary origins or are evolutionarily related from some common ancestor, although the category of species is difficult to apply to primitive non-sexually reproducing organisms , given that they are precisely not reproductively homogeneous.
The biological classification gives each species its own name, written in Latin and consisting of two terms : first that of the genus and then that of the species, as in Homo sapiens , name of the human species. In this sense, when we use common terms to refer to certain forms of life, such as “dog“, “cat”, “mushroom” or “fern”, we are actually referring to a set of species that can be highly diverse among themselves.
Origin of species
The way in which these appear is known thanks to the works of Charles Darwin, mainly . His essay On the Origin of Species published in 1859 laid the foundation for what we know today as biological evolution . In that text, Darwin explained that the species of living beings came from other previous species, that is, from their ancestors, whose destinies had been determined by environmental pressure, that is, the competition to survive and reproduce against other contemporary species. . Darwin called this competition “ natural selection ”.
These come from one another earlier, going back in life to a common ancestor , and so on back to the earliest forms of life. Darwin understood all this when on his travels he found how the species on the Galapagos Islands were similar to, but at the same time different from, those on the mainland. This suggested that, geographically separated for a sufficient amount of time, the island species had adapted to their new environment, following a different evolutionary path from their mainland counterparts. And so, eventually, each variant ended up being a different species.
species and genus
In the scientific name of the species of living beings, we can see both the genus and the species, written in Latin: Homo sapiens , genus Homo (human) and species “sapiens” (wise). This is because the genus is a higher (more general, less specific) taxonomic category than the species , but lower (less general) than the family .
The genus, thus, is a lineage of species, evolutionarily related and that somehow constitute variants, it could be said that different materializations, of a general concept that encompasses them. The genres, in addition, can be divided into subgenera or infragenera, sort of genres-within-the-genre, or they can be grouped into supergenera, an intermediate link between genre and family.
It can be classified according to the kingdom of life to which the animals they describe belong. In this sense, we know (according to 2009 standards):
- Animal . Of which 1,424,153 different ones are registered.
- Plant . Of which 310,129 different ones are registered.
- Mushroom . Of which there are notes of about 120,000 different ones.
- Protist . Of which there are notes of 55,000 different ones.
- Bacteria . Of which about 10,000 different ones are known.
- Archaeal . Of which barely 500 different ones are known.
- Virus . Of which there is a record of about 3,200 different ones.
Examples of Species
- Homo neanderthaliensis. Already extinct species of the human race, which lived with modern humanity about 230,000 years ago.
- Cannis lupus. Known as the gray wolf, it is the most common species of wolf in the world, to which the common dog could genetically belong, had it not been domesticated thousands of years ago.
- Panthera tigris. It is one of the four species of tigers in the world, famous for its striped and orange hide. It is endemic to the Asian continent where it is a large jungle predator.
- Helicobacter pylori. Species of gram negative bacteria that inhabits the human gastric apparatus, being able to develop infections in the gastric mucosa.
- Rhodnius prolixus. Called chipo or pito, it is a blood-sucking insect common in the American continent , capable of transmitting Chagas disease.
- Populus alba. Known as white poplar or common poplar, it is a leafy tree with green leaves with white undersides, common in Europe and Asia , which grows up to 30 meters in height.
These are those that are native to the habitat in which they are found , that is, they do not come from migrations , nor have they been artificially introduced. However, unlike endemic species , native species can perfectly well be found in other environments, in which, logically, they will no longer be native, but rather exotic species.
For example: the marine iguana of the Galapagos Islands ( Amblyrhynchus cristatus ) is native and endemic to the islands, as they originate from there, and is found nowhere else in the world. On the other hand, the Argentine ant ( Linepithema humile ) is a species native to South America (Argentina, Paraguay, Bolivia and southern Brazil), which has been artificially introduced to all other continents except Antarctica, and there it competes with the species of ants native to these continents.
These , introduced species or foreign species are those that are not native to the place where they are found , that is, they have been artificially introduced or are the result of migrations. In this sense, they are considered the opposite of native species.
Alien species can be beneficial or harmful to the habitat that receives them , thus altering the local ecological balance, and may result in competition for native species. In the event that they are harmful, they are considered invasive species.
Human beings are responsible for many species introductions over time , either consciously (ecological engineering) or inadvertently. A clear example of this are cows ( Bos taurus ), which today are grazed all over the world but have a South Asian origin. Another is the various species of wheat ( Tricutum spp ), introduced by agriculture on all continents.
These are considered those exotic species that, once they arrive in a new habitat, proliferate and generate an alteration in the native ecosystem , displacing other species or impoverishing the ecological niche, since they come from an external biological system. These species can represent a real biological danger, not only at the biotic level but also at the economic and agricultural level, or public health , and for this reason there are international regulations regarding the control of the transit of animals, plants, seeds, etc.
An example of invasive species is represented by common rabbits ( Oryctolagus cuniculus ) introduced into Australia in the 19th century to practice hunting , and which proliferated to such a degree that they became a plague in this country, putting entire plantations in jeopardy. , since they did not have natural predators in said ecosystem .
That is, the disappearance of all the individuals that compose it. It is a process that has often occurred in the biological history of the planet, sometimes individually and other times massively, in what is known as mass extinctions, evidenced in the geological fossil record.
Extinctions can occur for various reasons : drastic changes in the ecosystem (climatic, chemical, geological, cataclysms, etc.), emergence of a new, more successful species (natural selection) or, as occurs in modern times, due to human activity: pollution , hunting or indiscriminate logging, etc.