Evolution - Classification 9 and 16 July 2012

Why do we need to classify organisms?

·    It is easier to compare similarities between organisms

·    It is easier to compare differences between organisms

·    We can find certain organisms easily by using their characteristics

·    Accurately and uniformly names organisms

·    Prevents misnomers such as starfish and jellyfish that aren’t really fish

·    Uses same language (Latin or some Greek) for all names

So what is classification?

·    Classification is the arrangement of organisms into orderly groups based on their similarities.

·    Classification is also known as taxonomy.

·    Taxonomists are scientists that identify and name organisms.

Biodiversity

·    There are 13 billion know species of organisms

·    This is only 5% of the organisms that ever lived!

·    New organisms are still being found and identified

Standardized Naming

·    Binominal nomenclature used

·    Genus species

·    Latin or Greek

·    Italicized in print (eg. Turdus migratorius)

·    Capitalize genus, but NOT species.

·    Underline the genus and species name separately when writing (eg. Turdus migratorius)

Turdus migratorius

(image taken from: http://www.allaboutbirds.org/guide/American_Robin/id)

Classification Groups

·    Taxon (taxa – plural) is a category into which related organisms are placed

·    There is a hierarchy of groups (taxa) from broadest to most specific.

·    Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Domains

·     Broadest, most inclusive taxon

·     Three domains

·     Archaea and Eubacteria are unincellular prokaryotes (no nucleus or membrane-bound organelles)

·     Eukarya are more complex and have a nucleus and membrane-bound organelles

Taxons

·      Most genera contain a number of similar species, with the exception of Homo that only contains modern humans

·      Each successive classification category or taxon contains more different types of organisms than the preceding category.

Example of Classification of Humans

Classification Category	Characteristics
Domain Eukarya	Cells with nuclei
Kingdom Animalia	Mulitcellualr motile, ingestion of food
Phylum Chordata	Dorsal supporting rod and nerve cord
Class Mammalia	Hair, mammary glands
Order Primates	Adapted to climb trees
Family Hominidae	Adapted to walk erect
Genus Homo	Large brain, too use
Species Homo sapiens	Body proportions of modern humans