Introduction
Taxonomy (tacks-AHN-uh-mee) is the study of classification. It is a science of grouping organisms according to their presumed natural relationships. The problem with classification is that it is man-made. Many different schemes exist. For our purposes we will use 5 Kingdom system. More details on the characteristcs and members of various taxonomic groups (phylums, classes, orders, etc.) can be found in the units on microbiology, botany, and zoology.
• Taxonomy Table --- Very good introduction . Grouping methods and history. http://library.advanced.org/11771/english/hi/biology/taxonomy.shtml
• Nuts and Bolts of Taxonomy --- Excellent introduction. Great detail. Links. Contains instructions for a lab exercise. Search engine. --- http://jrscience.wcp.muohio.edu/lab/TaxonomyLab.html Advanced
• Schools of Taxonomy --- A comparison of taxonomic schools of thought. Class notes, advanced. Hypertext links.--- http://www.crl.com/~sarima/dinosaurs/philosophy/
• Taxonomic Glossary --- Advanced --- http://www.crl.com/~sarima/dinosaurs/philosophy/
• Taxonomy and Systematics --- Links. http://taxonomy.zoology.gla.ac.uk/
Historical Background
Aristotle was the first known individual to classify living things. He had two major groups... plants and animals. He further subdivided each of these groups. Plants were seperated based on there size (structure)... herbs, shrubs, and trees. Animals were grouped according towhere they lived...land, sea, or air.
Carolus Linnaeus (1707-1778) was a Swedish naturalist. He is considered the "Father of Taxonomy" because he developed the system by which we name organisms today. [Sometimes referred to as Carl von Linne']
Antoine Laurent de Jussieu (1707-1836) a French contemporary of Linneaus who established the major subdivisions of the plant kingdom.
Georges Leoplod Cuvier (1769-1832) the Frenchman who established major "embranchments", now known as phyla, for the animal kingdom.
Ernst Haeckel (1834-1919) German who introduced the monera kingdom.
Herbert F. Copeland (1902-1968) an American who reclassified all the microorganisms, championed the Kingdom protistica for all the nucleated microorganisms.
Robert H. Whitaker (1924-1980) the American who founded the five kingdom system by elevating the fungi to kingdom statis.
Why scientific names?
Why do scientists use such big names for organisms? Part of the answer are the problems caused by common names? Many organisms have common names based on visible characteristics like color (bluebird) or where they live. Which of the following are true fish with backbones?
Answer -- None, with the exception of the the first two organisms, each example belongs to a different phyum (See the table above). What they share in common is their habitat (where they live). None of them are "true fish" although each lives in water.
Another problem with common names is that an organism might have more than one common name. The buttonwood tree, plane tree and sycamore are all common names for Plantanus occidentalis.
Consider the next question. What do the following animals, cougar, mountain lion, panther, and puma have in common?
Answer: Everything. These are all regional names used in the United States, for the same animal.
Different languages also caused common name problems. Gatto, chat, and katze all refer to Felis domistica , the house cat, in Spanish, French and German respectively. Early on scientists recognized different languages as a communication barrier. This problem was over come by learning to read and write Latin. It followed that Latin would be the logical language fornaming organisms.
It was Carl Linneaus who developed a method for both classifying and naming organisms. He arranged organisms in groups based on common structural features. The last two groups, known as the genus and species were used to name the organism. The genus and species became known as the scientific name. None of the millions of species of organisms on the earth have the same scientific name. The system which uses "two names" is called binomial nomenclature (bie-NOE-mee-UINOE-mum-CLAY-chur).
Binomial Nomenclature
• A scientific name of an organim consists of a "last" name known as the genus and a "first" name called the species.
• This system is called binomial nomenclature, "two names" and was developed by the Swedish naturalist, Carl Linnaeus.
• The language generally used in classification is Latin but ancient Greek terms are also used. Latin is a classical language but, more importantly it is a dead language that is not subject to change.
• When writing a scientific name the first letter of the Genus name is always capitalized. The species name is entirely in lower case letters.
• The scientific name (and Genus namewhen written alone) are by convention expressed in italics. In older references they maybe printed in boldface. When written longhand scientific names are always underlined.
◦ Felis leo
◦ Homo sapeins
◦ Acer rubrum
• No two species have the same scientific name although they may share a common genus. The genus name shows a very close relationship.
◦ Felis domestica .....house cat
◦ Felis leo ............. lion
◦ Felis onca ........... jaguar
◦ Felis pardalis ....... ocelot
◦ Felis concolor ...... mountain lion
Naming an organism (Develop worksheet)
The binomial name of a species is its scientific name. Scientific names are generally chosen to describe an organism, its range, or to honor a person. Species names are generally selected as adjectives to describe the organism. Consider the following examples:
Ficus elastica - rubber plant
Elephus maximus - elephant
Pinus ponderosa - Ponderosa pine
Classification groups or taxa
The term taxonomy is derived from the Latin word taxa (singular = taxon) which means catagories. Its literal translation is the study of catagories. The basic taxa were developed by Carl Linnaeus. The largest of the taxa are the kingdoms. The number of species included in each of the decending taxa becomes less while the number of classifications within that taxon increases.
Listed in order the basic taxa are --- Kingdom, Phylum, Class, Order, Family, Genus, and Species. One trick to learning the order of the taxa is to memorize the following sentence where the first letter in each word represents the first letter of the taxa.
Katie Peels California Oranges For Grandma's Supper To understand how the classification system works study the following comparison. Finding a species is like mailing a letter from overseas.
*Botantists use the term division in place of phylum.
Sub and super groupings
Sometimes taxonomists will create sub (under) or super (above) groupings during their classification. Check out the following example:
• Phylum (FIlum)
• Subphylum - a group smaller than a phylum but larger than a class.
• Superclass - a group larger that a class but smaller than a phylum.
• Class
Subspecies, varieties, and strains.
• Subspecies (ssp.) refer to organisms of the same species that have notable morphological differences often due to geographic isolation. (Sometimes the term race is used used in describing a subspecies.)
• Varieties (var.) refer to organisms of the same species that have notable morphological differences NOT due to geographic isolation. Examples include any organisms that are breed for certain characteristics like dogs and cats.
• Strains refer to biochemically dissimilar groups usually in reference to microorganisms. The strain is often represented by letters or numbers. Example... S. marcescens, D1
While questions arise regarding the placement of an organism into a taxon, the scientific name of that organism never changes.
Basis for classification
All of the following have been used as a basis for classifying organisms.
• Morphorological similarities - a comparison of structures.
◦ Homologous structures
◦ Analogous structures
• Cellular organization - a comparison of cells and their organelles.
• Biochemical similarities -- a comparison of products made or use by an organism. Particulary cytochrome c.
• Genetic similarities - a comparison of amino acids, proteins, and nucleic acids. (Quagga)
• Chromosome similarites - a comparison of the number of chromosomes and their shapes.
• Embryological similarites - a comparison of the amount of time before differentiation in embryos.
Quagga, extinct since 1883. Identified as a species of zebra not horse based on mitochondrial DNA from preserved muscle tissue. (See Vol 54 #6).
Systematics (Expressing relationships)
Biosystematics is the study of reproductive compatibility and gene flow to infer evolutionary relationships.
Dichotomous Key - a written set of choices that leads to the identification of an organism.
Phylogeny - infers the evolutionary history of a species. It is derived from the Greek terms phylo meaning tribe, race or clan and geny meaning being born. The development of a phylogenetic tree (family tree) is a visual model of inferred evolutionary relationships amongs organisms. The closer an organism is to another on a branch the more closely they are related. The tips of the branches represent newly evolved species which can be traced backward into the trunk which represent older species from which new ones evolve.
• Taxonomy - systematics --- http://www.ucmp.berkeley.edu/subway/phylogen.html
• Tree of Life Homepage --- http://phylogeny.arizona.edu./tree/phylogeny.html
• "Ontogeny recipulates phylogeny"
• What is Phylogeny? --- http://phylogeny.arizona.edu/tree/home.pages/whatisphylogeny.html
• Phylogenic Web Sites --- Links to databases, software and more. --- http://loco.biology.unr.edu/archives/rasa/list of sites.html
• Plant and Animal Phylogeny --- Links to museums, hypertext college exercise. --- http://www.utm.edu/~rirwin/phylolab.htm#AnimPhylog
• Concept and Meaning of Species --- http://hyperion.advanced.org/19926/text/tour/13.htm
• Species: Definition and Origins --- http://wcb.ucr.edu/wcb/schools/CNAS/biol/wwalton/1/modules/page46.html
Online resources
• Coelomate Evolution --- http://www.utm.edu/~rirwin/coelomate2.htm
• Protostomes vs Deutrostomes --- http://ithaca.edu/hs/bio/courses/principles/Prot-Deut.html
Kingdoms
The kingdom problem.
The very first classification attempts began as far back as Aristotle. In his system there were two major groups, kingdoms if you will, ... plants and animals. With the development of the microscope, smaller life forms were discovered. Because some of these organisms didn't fit well into either the plant or animal group a third kingdom was added called the protista. A fourth kingdom was created based on plants that had lost their ability to make their own food. This kingdom was called the fungi. Herbert F. Copland championed the four kingdom scheme in 1956.
The presence of unicellular forms that lacked a "true nucleus", and other membraned organelles, caused taxonomists to propose a fifth kingdom which they named monera. The five kingdom system approach was advanced by R.H.Whittaker in 1959. It has remained relatived unchanged since that time. However; today the terms protoctista and prokaryotae are often substituted for protista and monera respectively.
The most recent scheme includes six kingdoms. The prokaryotes have been split into eubacteria (true) bacteria and archeobacteria (ancient).
Another Taxon
In the 1960's Carl P. Woese proposed another taxon larger than a kingdom. He called it a domain. Organisms were placed in one of three domains based on nucleic acid studies.
Online resources
• Biologist Whose Heresy Redraws the Earth's Tree of Life --- http://leahi.kcc.hawaii.edu/~johnb/micro/m130/readings/margulis.html
• Classification: 3, 5 Kingdom --- http://www.cat.cc.md.us/~gkaiser/lecguide/unit1/index.html
• Classification and Biological Diversity --- http://gened.emc.maricopa.edu/bio/BIO181/BIOBK/BioBookDivers class.html
• Taxonomy: Five kingdoms of Life I --- http://wwwmc.nhmccd.cc.tx.us/eelc/learning resource center/taxonomy.html
• Taxonomy: Five kingdoms II --- links --- http://wwwp.wfu.edu/~dimock/webhome
Comparison of the Five Kingdom System
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