2.1: Taxonomy and Phylogeny
- Page ID
- 2624
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Taxonomy vs. phylogeny?
- Taxonomy is the science/study of classification.
- Phylogeny is the science/study of evolutionary relationships between organisms.
Modern taxonomy is based on phylogeny.
- Nucleic acid sequencing (of DNA and/or RNA) is used to establish evolutionary relationships between organisms.
- Taxonomic levels for cellular organisms from most inclusive to least inclusive:
Domain, Kingdom, Phylum, Class, Order, Family, Genus, specific epithet (genus + specific epithet= unique species name)
Binomial nomenclature and naming cellular organisms
- cellular=made of cells
- All cellular organisms have a “scientific name”
- the scientific name consists of a genus name (Capitalized) and a specific epithet (lower case)
- together this 2-part name is the “species” name.
- This system of naming was developed by Carolus Linnaeus and is called the “binomial nomenclature” (“two term name”)
| Common name | Scientific name |
|---|---|
| humans | Homo sapiens |
| bacterium in gut | Escherichia coli |
-Note in the examples, Homo and Escherichia are the genus names, sapiens and coli are the specific epithets. Also note the convention of making the scientific name/species name appear different from surrounding text; this is usually accomplished by using italics or underlining. Also note that the genus name can be abbreviated by using the first letter only.
- Homo sapiens =H. sapiens
- Escherichia coli = E. coli
Sizes of microbial pathogens
“microbial” =so small, requires microscope to visualize. metric units used in microbiology:
- mm=millimeter=10-3 meter (one thousandth meter)
- µm = micrometer 10-6 meter (one millionth meter)
- nm=nanometer=10-9 meter (one trillionth meter)
resolution limit of human eye ~ 100 micrometers µm = ~ 0.1 mm
- bacteria ~ 1µm (µm = 10-6 meter)
- viruses 30-300 nm (nm=10-9 meter )