The level at which a common range is determined by taxonomy
classificationOrder element(taxonomic category) isBiotaxonomyDetermine the level of common scope.modernBiological classificationSeven necessary orders are adopted: Kingdom, Phylum, Class, Order, Family, Genus and Species.
classification systemyesOrder systemIt usually includes 7 main levels: species, genus, family, order, class, phylum and kingdom.Species (species) are the basic units. Related species belong to genera, related genera belong to families, families belong to orders, orders belong to classes, classes belong to phyla, and phyla belong to boundaries.With the development of research, the classification level is increasing, and secondary units can be added up and down the unit, such as the total class (superclass)Subclass, sub programsuperorder(hypermesh)Suborder, sub itemGeneral Section(super science)subfamilywait.In addition, new units can be added, such as unit, group, tribe, group, etc., of which the most permanent is tribe, between subfamily and genus.Usually subspecies are classified, and only subspecies units are set for animals.
Species are basicOrder element；Similar, withCommon originSpecies, aggregated into genera;A similar genus of common origin grouped into families.To create a genus, you mustMode speciesBased onType genus；Both genera and familiesmorphologyandecologyThe uniqueness of.The order above is the most stable, and there is little doubt about their common range.[1]
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The animals living on the earth have been described and named about 1.5 million species, and more than 10000 new species are recorded every year.To study such a large number of animal species, we mustapplied scienceOfclassification method First, distinguish, identify and name the animals, and summarize them into appropriateClassification order(i.e. classification grade), establish a classification system.So that we can identify species and clarify thegenetic relationshipAnd the systematic development of the animal kingdom.
Classification order
Taxonomy uses different grades to classify animals step by step according to the morphological similarities and differences between species and the closeness of evolutionary relations.In the animal classification system, the most basic order is species.Species isobjective existenceAnd occupies a certain space, including one with similar origin, basically similar in morphology and physiology, and male and female mating can produce offspring that are similar to their parentsAnimal populationThe general name of.Species are separated from each other in reproduction, that is, species cannot mate and reproduce, and even if they can mate and reproduce, their offspring are sterile.For example, if a horse and a donkey cross to produce a mule, the mule cannot have offspring, so the horse and the donkey are two different species.Therefore, species have relatively stable and clear boundaries and can be distinguished from other species.Species are also evolutionary. In the process of development and evolution, there are many intraspecific individualsvariationWhen the variation increases to the characteristics of breakthrough species, new species may be formed.
In the classification system, the higher order of the species is the genus.Genus is a collection of species with common characteristics.The following genera form families, families form orders, orders form classes, and finally classes form phylum and phylum form boundary.Therefore, in the classification system, from large to small, there are several important classification levels: kingdom, phylum, class, order, family, genus and species.Subphyla, subclass, suborder, subfamilySubgenusAnd subspecies;On the basis of all levels, general classes, general orders, general families, etc. are established.[2]
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Classification orderinsectThe ownership of, including the classification location andPhylogenyThey all have clear concepts.withstriped rice borerFor example:
"Sub" can be set from boundary to species, such asYamen（Subphylum）、SuborderSuborder, subfamily, etc.Sometimes "Super" can be added to orders and families, such as Superorder and Superfamily.Between subfamily and genus, sometimes at Tribe level.In sometaxonomyIn his works, he once used the rank of "Cohort", some of which were between classes and orders, and some were between suborders and superfamily.
The boundary of biology and the position of animals in it
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Biological boundary
The substances in nature are divided into biological andAbioticTwo categories.The former has metabolismSelf replicationReproductionGrowth and development、genetic variation、InductivityAnd adaptability, etcLife phenomenon。Therefore,Biological worldAlso called Vivicum.There are many kinds of creatures in various forms, about 2 million of which have been identified.As time goes by, the newly discovered species will increase year by year. Some people (R.C. Brusca et al., 1990) estimated that there are about 20 million to 50 million species to be discovered and named.In order to research and use suchRich and colorfulIn the biological world, people classify it into several different kingdoms.[3]
With the development of science, the demarcation of biology is deepening.In the Linnai era, creatures were mainly distinguished by the characteristics that could be observed with the naked eye. Carl von Linn é (1735) explicitly proposed the animal kingdom (Anim á lia) andFlora(Plantae)Two bound systemThis system was still adopted by most textbooks until the 1950s.After the microscope was widely used, manyUnicellular organismBoth animal and plant characteristics (such asEuglenaEtc.), thisIntermediate typeThe organism of is the evidence of evolution, but it is a difficult problem of classification. Therefore, J. Hogg (1860) and E.H. Haeckel (1866) willProtozoa(including bacteriaalgae, fungi andprotozoan）Set up another boundary and proposeprotista(Protesta), plant kingdom, animal kingdomTriple bound systemThis view did not become popular until the 1960s and was adopted by some textbooks.[3]
Biological boundary
electron microscopeThe development of technology makes it possible for biologists to reveal bacteriablue-green algaeThe fine structure of cells, and found that it was significantly different from other organisms, so he proposedprokaryote(Prokaryote) andEukaryote(Eukaryote).H.F. Copeland (1938) established prokaryotes as another boundary and proposed four boundary systems, namelyProkaryote(Monera), Protocosta (includingUnicellular algae, simplemulticellular AlgaeMyxomycetes, fungi and protozoa), Metaphyta andMetazoanMetazoa.With the improvement and wide application of electron microscopy technology and the accumulation of biochemical knowledge, the idea of setting prokaryotes as a world has gained widespread acceptance and become a modern organismSystem classificationThe foundation of.In 1969, R.H. WhittakerCellular structureThe complexity and nutrition mode ofFive bound systemHe separated fungi from the plant kingdom and established another kingdom, namely the prokaryotic kingdomprotista、Fungal kingdom(Fungi), flora and fauna.This system was gradually widely adopted, and some textbooks were still in use until the 1990s (Xu Tu-1, 2, 3).[3]
Biological boundary
The evolutionary history of life has gone through several important stages, and the initial life is a non cellular form, that is, a non cellular stage.From non cell to cell is the second stage of biological development.The initial cells areProkaryotic cell, byProkaryoteOrganisms composed of cells are called prokaryotes (bacteria, cyanobacteria), from prokaryotes toEukaryoteIt is the third stage of biological development, and the fourth stage of biological development is from single-cell eukaryotes to multicellular eukaryotes.The five boundaries system reflectsBiological evolutionAndmulticellular organismThe three branches of the stage, namely, prokaryotes represent the primary stage of cells, protozoa represent the single-cell stage of eukaryotes (the advanced stage of cell structure), and then evolve to the eukaryotic multicellular stage, namely, plant kingdom, fungus kingdom and animal kingdom.Plants, fungi and animals represent three directions of evolution, namely autotrophicSaprophyticandHeterotrophic。[3]
Biological boundary[3]
The five boundaries system does not reflectAcellular organismPhase.Famous entomologist in ChinaChen Shixiang(1979) proposed three general boundariesSix bound system, that is, the total non cellular boundary (includingVirusesBoundary), the former nuclear total boundary (includingBacterial kingdomandCyanophyceae）, Eukaryotic kingdom (including plant kingdom, fungus kingdom and animal kingdom) (Xu Biao-1).Some scholars think it is unnecessaryprotistaThe algae and protozoa are divided into the plant kingdom and the animal kingdom, forming a relatively compact four kingdom system.Other scholars advocate expanding the kingdom of protozoa to include fungi as another four kingdom system.Since virus is a kind of non cellular organism, it is still uncertain whether it is the original type or the secondary type. Therefore, scholars still have controversy about the view that virus is included as one of the original life types.
In recent years, some scholars have proposed a six world system different from the above six worlds (such as R.C. Brusca et al., 1990), which willArchaeaAnother boundary, namely ProkaryoteBiosphere、Palaeobacteria(Archaebateria, also translated asProtobacteria, includinganaerobicMethanogenic bacteriaEtc.), protozoa, fungi, plants and animals.Another scholar (T. Ca valier Smith, 1989) proposed an eight kingdom system, which divided prokaryotes into archaeaEubacteriaEubacteria, which divides eukaryotes into two super realms: paleoeukaryote and metakaryota. The former super realm contains only one realm, namely Archezoa, while the latter super realm includes protozoa and Chromista, which includesCryptophyteCryptophyta and ChromophytaSubrealm）, plant kingdom, fungus kingdom, animal kingdom.Some scholars believe that this boundary system is more reasonable and clear.[3]
To sum up, we can see that there is no unified opinion on the biological boundary.But anyway, from 3 billion yearsancient extinct lifeOfFossil recordOr the current living conditions on the earth;From morphological comparison, physiological and biochemical examples, it reveals the evolutionary direction of organisms from prokaryotic to eukaryotic, from simple to complex, from low to high.The biological boundary shows the development process of life history.[3]
The relationship between organisms is complex, but their basic requirements for survival are nothing more than taking food to obtain energy, occupying a certain space and reproducing offspring.There are many ways for biology to solve these problems.In terms of access to nutritioncarbon dioxide、inorganic saltAnd the food needed for energy synthesisAutotroph，Green plantsandPurple bacteriumThey are autotrophs.Therefore, plants are the producers of food, and the food connection between organisms starts from this.Animals must obtain nutrition from autotrophsPhytophagousAnimals eat, and the latter isCarnivorous animalTherefore, animals belong to the heterotrophic type of predatory feeding, and are food consumers in the biological world.Fungi are decomposing and absorbing nutrients, and they are in the status of reducers.All these show that the three kingdoms of life are the most basic, and they are interrelated in terms of nutrition during evolution and developmententiretyAnd systematic, and biologicalecosystemIn coordination with each otherMaterial cycleAnd energy flow process.[3]
