The Swedish botanist Carolus Linnaeus originally invented the binomial system to help him consistently name plants he identified. He detailed this naming system in his book Systema Naturae. The system was eventually adopted by other scientists and remains to the accepted naming system for species. Though species may have many common names to avoid confusion scientists always use the scientific/binomial name. 5.3 Classification of biodiversity 5.3 Essential idea: Species are named and classified using an internationally agreed system. 5.3.U2 When species are discovered they are given scientific names using the binomial system. 5.3.U1 The binomial system of names for species is universal among biologists and has been agreed and developed at a series of congresses. The 22 nd International Congress of Zoology (ICZ) Carl Linnaeus originally published Systema Natura in 1758 in which he gave binomials for all species known at that time. The IBC of Vienna in 1905 voted to accept his naming convention. Since then both the IBC and ICZ have been the bodies that oversee the international efforts to maintain consistent naming conventions and use of taxon. Periodically the congresses meet to discuss issues affecting classification. 5.3.U2 When species are discovered they are given scientific names using the binomial system. Which of the following are true of these elephants? 5.3.U2 When species are discovered they are given scientific names using the binomial system. Which of the following are true of these elephants? 5.3.U7 Taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species. Historically classification systems have been revised repeatedly based on emerging evidence. Recent evidence from genetic studies of ribosomal RNA has shown that "prokaryotes" are far more diverse than anyone had suspected. Previously in the second half of the 20th century all living organisms were classified into five kingdoms. This included prokaryotes being placed in one kingdom and eukaryotes were split-up into the remaining four kingdoms. ribosomal RNA is found in all organisms and evolves slowly so is a good way to track evolution over long time periods. 5.3.U4 All organisms are classified into three domains.The Prokaryotae are now divided into two domains, the Bacteria and the Archaea No one of these groups is ancestral to the others, and each shares certain features with the others as well as having unique characteristics of its own. Bacteria and the Archaea are as different from each other as either is from the Eukaryota, the third domain. Revision of the classification system lead to a new level of taxon called domains. n.b. viruses are not classified as living organisms in the same way that eukaryotes, archaeans, and bacteria are. They are however of considerable biological importance. 5.3.U4 All organisms are classified into three domains. ArchaeaBacteria (Eubacteria)Eukaryota Examples are often, but not always, extremophiles: Sulfolobus sp. grow in volcanic springs with optimal growth occurring at pH 2-3 and temperatures of C Halobacterium sp. (lives in water with high salt concentrations) Staphylococcus aureus (above) can cause skin infections and respiratory disease Cyanobacteria sp. Are photosynthetic Rhizobium sp. live symbiotically with plants and fix nitrogen Includes several kingdoms including fungi, animals and plants. Examples range from algae to Humans. No nuclear membrane RNA and biochemistry distinct from bacteria No nuclear membrane Nuclear membrane Features and examples of each domain: 5.3.U3 Taxonomists classify species using a hierarchy of taxa. 5.3.U5 The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, genus and species. Not all domains use the same taxa the example above is for Eukaryotes 5.3.U5 The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, genus and species. Do Kings Play Chess On Fine Grain Sand? 5.3.A1 Classification of one plant and one animal species from domain to species level. Learn a mnemonic, one animal example and one plant example: DomainDoDoEukaryota KingdomKingsAnimaliaPlantae PhylumPlayChordataSpermatophyta ClassChessMammaliaEudicotyledons OrderOnOnPrimatesMagnoliidae FamilyFineHominidaeRanunculales GenusGrainHomoRanunculus SpeciesSand?SapiensAcris Human Meadow Buttercup 5.3.S1 Construction of dichotomous keys for use in identifying specimens. Dichotomous keys are used by scientists to establish which taxa a species belongs to. A dichotomous key consists of a numbered series of pairs of descriptions. One of these should clearly match the species and the other should clearly be wrong. The features that the designer of the key chooses to use in the descriptions should therefore be reliable and easily visible. Each of the pair of descriptions lead either to another of the numbered pairs of descriptions in the key, or to an identification. 5.3.S1 Construction of dichotomous keys for use in identifying specimens. 5.3.U6 In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species. Natural classification groups together species that share a common ancestor from which they evolved. This is called the Darwinian principle of common descent It is expected that members of a group share important attributes or 'homologous traits that are inherited from common ancestors. For example Lions share more traits with Jaguars than with Clouded Leopards. 5.3.U6 In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species.. Grouping together birds, bats and bees because they fly would be an artificial classification as they do not share a common ancestor and evolved the ability to fly independently. Natural classification is not straightforward as convergent evolution can make distantly related organisms appear similar and adaptive radiation can make similar organisms appear very different from each other. Plants and fungi were once classified together because they both possessed shared characteristics such as cell walls. It is now known that this is an artificial grouping as their cell walls have a different molecular biology and they evolved separately. 5.3.U8 Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group. If a new species of Ant is discovered then scientists would predict that the species should possess amongst other characteristics six jointed legs, a head, thorax, abdomen, elbowed antennae, antibiotic secretory glands. If the species does not match the expected set of characteristics this brings into question either the classification of the species or of Ants as a family. Natural classification is very helpful when dealing with new species: New species of legless amphibian discovered in remote Cambodian rainforestof-legless-amphibian-found-in-cambodia/ Dichotomous keys can be used to help identify the species. The keys can place a specimen with the most closely related species, genus, family or phyla using natural classification. To what level of classification a specimen can be placed depends on how unique it is.