Essential idea: Species are named and classified using an internationally agreed system. By Chris Paine https ://bioknowledgy.weebly.com/ http://www.tokresource.org/tok_classes/biobiobio/biomenu/classification/ index.htm The Swedish botanist Carolus Linnaeus originally invented the binomial system to help him consistently name plants he identified. 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
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Essential idea: Species are named and classified using an internationally agreed system.
The Swedish botanist Carolus Linnaeus originally invented the binomial system to help him consistently name plants he identified. 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.U1 The binomial system of names for species is universal among biologists and has been
agreed and developed at a series of congresses.
The 21st International Congress of Zoology (ICZ)
http://iszscon2012.haifa.ac.il/
http://www.ibc2017.cn/index.html
• Carl Linnaeus orginally 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.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.Recent work
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.
5.3.U4 All organisms are classified into three domains.
Archaea Bacteria (Eubacteria) Eukaryota
Examples are often, but always, extremophiles:• Sulfolobus sp. grow in volcanic
springs with optimal growth occurring at pH 2-3 and temperatures of 75-80 °C
• Halobacterium sp. (lives in water with high salt concentrations)
• Staphylococcus aureus (above)can cause skin infections and respiratory disease
• Cyanobacteria sp. Arephotosynthetic
• 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:
http://en.wikipedia.org/wiki/Three-domain_system
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.A3 Recognition features of porifera, cnidaria, platylhelmintha, annelida, mollusca, arthropoda
and chordata.
Symmetry Segmentation Digestive tract Other features
porifera(sponges)
None None No mouth or anus • Porous• attached to rocks• Filter feeder
cnidaria(corals, jellyfish)
Radial None Mouth but no anus • Stinging cells• Tentacles
platylhelmintha(flatworms)
Bilateral None Mouth but no anus • Flattened body
annelida
(earthworms,
leeches)
Bilateral Very segmented
Mouth and anus • bristles often present
Mollusca
(oyster, snails,
octopus)
Bilateral Non-visible segmentation
Mouth and anus • Most have shell made of CaCO3
Arthropoda
(ant, scorpion,
crab)
Bilateral Segmented Mouth and anus • Exoskeleton• jointed appendages
Chordata
(fish, birds,
mammals)
Bilateral Segmented Mouth and anus • notochord• hollow dorsal nerve cord• (some have ) pharyngeal slits
A summary of key features that can be used to distinguish between animal phyla
5.3.S1 Construction of dichotomous keys for use in identifying specimens.
5.3.S1 Construction of dichotomous keys for use in identifying specimens.
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
.
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.
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.
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 rainforest”
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.