Kind (biology)

the term kind or species (of lat. species, the kind) is a fundamental category of biological systematics. A generally accepted definition of the term of the kind did not succeed so far, on the contrary different kind concepts, those which can be overlapped, exist butidentical classifications do not lead. The concepts today common in biology follow the Primat of the “masterhistorical relationship”: Thus the term designates frequently a group of organism, those by transmission so many unmistakable morphologic and/or. physiological characteristics together have thatthey on the basis this combination of characteristics in relation to every other group of organisms than definably apply. After another view those individuals and their direct descendants belong to a kind, which with one another reproduce themselves in natural way under generation of fruitful descendants.A third view limits the kind term on individuals, who divide an ecological niche.

To the technical language of the natural scientists the term kind was already taken up, when still of the Konstanz of the kinds were convinced their representative; there God everyoneKind in a separate office for creation produced, can differentiate one each kind in principle and clearly from another kind. Under the influence of the evolution teachings and the associated conviction that there must be transitions between the kinds, the established becameIt maintains kind term, at the price that none of the today usual definitions covers all well-known ways of life.

Beginning 21. Century were described between 1,5 and 1.75 million kinds, whereby is to be assumed it itself with these only around a fractionall existing kinds acts. Estimations assume that, which is clearly higher the total number of all kinds of the earth. The most extreme acceptance reach thereby up to 117.7 million kinds, most frequently however estimations between 13 and 20 million kinds are stated.

Table of contents

morphologic (typologisches) kind concept

kinds are groups of organisms, which can be differentiated concerning a set of quantifiable morphologic characteristics clearly from each other.
A population is added to that kind, their description of typecorrespond to at least 75 per cent of the individuals.

One due to this concept defined kind is called Morphospezies.

Hauptprobleme of this concept:

Example paleontology: A find of fossils of two individuals inthe same find layer, thus practically at the same time living, differ strongly from each other:

  • They can be assigned now two different kinds, if one the opinion is that they deviate strongly enough from a morphologic type. In addition, they can the same kindit is assigned if one the opinion is that in this kind also a larger range of variation, which includes the finds with can be accepted.
  • In addition, the differences can on a clear Sexualdimorphismus (differences in the feature of the males and females)within a kind to lead back its.

These problems will with increasing number of the finds and thus knowledge of the actual range of variation smaller, can however not completely be eliminated.

With rezenten organisms also ethologische, anatomical leave themselves apart from the morphologic characteristics, physiological, biochemical and molecular characteristics for the regulation consult. Within wide ranges, as for instance in the microbiology or with the Nematoden morphologic kind demarcations fail to a large extent.

chronological kind concept

also this concept predominantly finds in the paleontology application andin the long run only one extension of the morphologic kind concept is around the factor time:

A kind is characterized by a sequence temporally of sequential populations, whose individuals lie within a certain morphologic range of variation.

This concept is well applicable if practically completeFind sequences are present.

population-genetic kind concept

a kind (bio species) consists of at least one population, whose gene pool is generativ isolated against populations of other kinds. The details exchange between the populations is by reproduction isolation (reproduktive isolation, see biological evolution) prevented
member of a kind fruitful descendants are morphologic or physiologically only in individual characteristics distinguishable can produce apart from sex-specific characteristics and under natural conditions.
Ernst Mayr 1969: A kind is a reproduktive community from populations (reproduktiv isolates fromother one), which takes a special niche in nature.

Examples:

  • Horse and donkeys are crossable, have however no fruitful descendants, belong thereby to different kinds.
  • Lion and tigers are crossable (so-called „hybrid cats “: Liger and Tigon) and haveperhaps fruitful descendants, live however in different circulation areas, let themselves morphologically from each other be defined and belonged thereby to different kinds.

Problem:

  • Quibbling one would know earlier generations of a kind, which with the rezenten generations no more cannot cross, afterbelonging regard to the wording of this kind definition as to another kind. An actual time barrier between populations existing at the same time exists for example between the spring form and the autumn form land small cards - of the butterfly. They differ coloured strongly, come into unserm climatic area notmore reproduktiv in contact, can be crossed however in the laboratory fruitfully and applied therefore officially than a common kind.
  • Kinds, which increase only ungeschlechtlich, are not seized by the definition. They are called Agamospezies. To it all Prokaryoten belongs, some Protisten, some mushrooms, some plants like the banana) as well as some animals (determined Echsen and other vertebrate animals). (See also for this Genet.)
  • Orchideen to be able partially even over generic borders away fruitfully to cross. These form neverthelessThe hybrid quantitative exception, while the different morphologically described Orchideenarten remains distinguishable and type-pure populations to form.
  • Individuals, those in a population not to reproduce can become (for example female workers with ants or bees) apparently not seized. They have howeveras can be prove common parents with the fruitful individuals and belong therefore free of doubts to the kind population.

Phylogeneti (evolutionary) kind concept

this kind concept includes the biological also.

A kind is (monophyletische) a descending community from one to many populations in a certainTime interval.
A kind begins all individuals of this kind after
  1. a kind splitting and ends if, without leaving descendants, becomes extinct or
  2. if from this kind from kind splitting two new kinds result.

Eine Artspaltung ist gekennzeichnet durch die (natürliche) reproduktive Isolation vonPartial populations, which is caused by geographical, morphologic, genetic or ecological barriers.

Phylogeneti Anagenese is the change of a kind in the period between two kind splitting, thus during its existence.

Fossils can also here only due to morphologic characteristics of a kind assigned, this effected however on the basis of a relationship analysis, the equipment of phylogenetischen systematics and not due to an allocation to an abstract type or structural drawing.

In phylogenetischen trees usually the family relations determined on the basis one or several genes become betweendifferent kinds represented.

only few morphologic distinguishers

show and exhibit physiological definition with bacteria bacteria practically no recombination barriers . Therefore the metabolism is consulted as distinction criterion of trunks. On the basis biochemical characteristics as for instance the Sustanz of the cell wallone differentiates between the higher Bakterientaxa.

One tests their ability at bacterial pure cultures for their “kind regulation” to certain biochemical achievements, for instance the ability to the dismantling more intended “substrates” e.g. rare kinds of sugar. This ability is very simply recognizable, if the conversion product one inCulture medium course-set color indicator umfärben can. By inoculation of a bacteria pure culture into a set of culture kulturgläsern with nutritive solutions, which only in each case a certain substrate contained (“selective media”), one gets a so-called. “Multicolored row”, from whose color changes according to a table the type of bacteria are determinedcan.

As the further characteristic for the kind regulation at bacteria also the optimal growth temperature is used, which conclusions it permits whether it concerns a bacterium out of the body of Warmblütern or around a kind out of the open land. Legally one standardizedtherefore for the drinking water investigation a parallel investigation with Bebrütungstemperaturen of 20°C and 36°C for the so-called.Gesamtkeimzahl.

Recently bacteria trunks are identified or differentiated also on the basis the DNA sequences. In this way different are (! in 1 ml soil up to 100000)Bakteriengenome determined its, which were interpreted as different kinds. This is not to confound with the mentioned Gesamtkeimzahl, which lies in the same order of magnitude, but only “few” kinds covers itself, with a certain culture method by the educationfrom colonies show.

These distinction criteria are purely pragmatic. On which level of the distinction one differentiates trunks here from kinds or kinds, is a thing of the convention. None of the kind concepts discussed above supplies sufficient criteria for a kind definition of bacteria.Or in order to say it with Ernst Mayr: “Bacteria do not have kinds” (see under “quotations”)

further concepts for definition a kind

coherence

the coherence (lat. cohaerere, are connected), the co-operation of a descending community, are to explain,why differently kinds, which are obviously not generativ from each other isolated and overlap in their circulation areas, remain stable and not into a kind to merge. These kinds are adapted by a sentence at Erbmerkmalen in each case to their circulation area, and form inthe equiphase zones fruitful hybrids out. Stabilizing selection however the larger variability resulted from hybridizing. Genetic bases can be specific combinations of genes ( for example gene coupling).

Rekognition

the Rekognition (close. recognition, recognition)explains the stability of a kind by a sentence of morphologic, physiological and ethologischen characteristics, which optimize the success of a mating with members of the same kind. The members of a kind can recognize reproduction partners due to certain characteristic combinations, which a high reproduction successguarantee. Reproduction isolation is regarded as secondary seeming.

kind as Taxon

the scientific name of a kind (traditionally usually latin or Greek origin) sits down after the binary nomenclature in such a way specified from the generic name (capitalized) and the specific Epition(smallwritten) together. It is usually italically set in the text or underlined alternatively. In the scientific sense the kind name becomes completely correct only then if still the authors are attached, who described the kind as the first. This rule should inscientific publications to be obeyed whenever no bibliografische reference takes place for description of kind. In the Botanik and mycology the author names are shortened usually, „for L. “stand for example for Linné.

  • Example:

Shiitake Lentinula of edodes (Berk.) Pegler M. J. Berkeley has the kindfirst, D described. Pegler has it arranged in the today valid system

historical development of the kind term

the development of the kind term is closely linked with the development of the conception of the variability of the kinds:

The beginning of the scientificClassification of the organisms is appropriate in 18. Century with Carl von Linné, who took the reproduction organs ( for example blooms) as substantial characteristics. It proceeded (consciously or unconsciously) from an idealized kind term: After the understanding of its time one placedKind a constant unit, and Linné tried to identify standard copies of each kind. He understood the naturally occurring variability as deviations or abnormalnesses.

In the process 19. Century consolidated themselves the observations that the kinds in the course of their natural history changesgo through.Charles Darwins evolution theory could explain these observations in summary. Each individual leaves the own characteristics to the descendants. Variations within populations are herein no deviations from (idealistic) a standard separate necessarily for surviving the kind. Individuals with unsuitable characteristicsby selection on the average less descendant, and its characteristics will have will not thus pass on.
Thus the common descent became the substantial characteristic of the determination of a kind.

A consequence from the theory from Darwin is that all life on earthfrom (or a group of) primitive organisms to descend must. Therefore not the fact of the common descent, but the degree of relationship is decisive for the definition of a kind.
A second consequence is that a kind only at a certain time well-definedis. In the past two populations, which are understood today as two kinds, can have been a kind. For example one assumes the polar bear itself before some 10,000 to few 100,000 years of a population living in Siberiathe brown bear split off. In the future a today's kind may split up into several.

quotations

  • „only two kind concepts, everything else are definitions, like one a kind as systematic unit, give to describe thus as Taxon, are.The two concepts are the typologische kind concept, which describes a kind as something, what clearly outwardly from other organisms differ, and the biological kind concept, which calls kinds communities of individuals, who can witness potenziell reproductionable descendants with each other.There are not other kind concepts. “ Ernst Mayr
  • „bacteria have no kinds. Netzeitung: What then? Mayr: That leave I the micro biologists. Those do not understand that yet. Archaebakterien for example exchange genes with bacteria out, bacteria and Archaebakterien under in each caseeach other anyway. Does one have to thus call all bacteria large reproduction community, thus as a kind? Bacteria do not have kinds. The first kinds, which there are, are already Eukaryonten. Why one needs a cell core, in order to be able to be a kind, knowsI also not. “ Ernst Mayr

see also

literature

  • Campbell, Neil A. (1997). Biology, spectrum academic publishing house Heidelberg, S. 476ff, ISBN 3-8274-0032-5
  • Cracraft, C. (2002). The seven greatquestions OF systematics biology: on essential foundation for conservation and the sustainable use OF biodiversity, in: Annals OF the Missouri Botanical guards, 89, 127-144.
  • Hammond, P. (1995). The current magnitude OF biodiversity, in: Per cent. Heywood and R.T. Watson(Eds.), global Biodiversity Assessment. (pp. 113-138). Cambridge, U.K: Cambridge University press.
  • Kunz, Werner (2002). What is a kind? In practice works, but defines in a diffuse way. In: Biology in our time. 1/32/2002, S. 10-19, ISSN 0045-205X
  • Mayr, Ernst (1997). That is Life - the science of the life, spectrum academic publishing house Heidelberg, ISBN 3-8274-1015-0
  • N. N. (1963). Animal Species and evolution. (German: Kind term and evolution. 1967)

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