Classification, Evolution, 16/7/2012

Why do we need to classify organisms?


~Easier to compare similarities and differences between organisms
~Find certain organisms using their characteristics
~Accurately and uniformly name organisms
~Prevent misnomers (that is, misleading names) such as starfish and seahorse that are not really fishes or horses
~Use standard language (Greek/Latin) for all names


What is classification?


Simply said it is the arrangement of  organisms into standard groups based on similarities
It is also known as Taxonomy


Some facts on biodiversity:


There are 13 bil. known species of organisms which is 5% of all organisms ever lived. This number is growing as new organisms are still being found and identified!




Binomial Nomenclature--The current system of classifying invented by Carolus Linnaeus.

Scientific name of all organisms: Genus(start with caps) species(small letters)

Italicized in print, underlined in writing

e.g. American robin's scientific name--

(in print): Turdus Migratorius
(in writing): Turgus Migratorius

Taxon (pl. taxa) is a category into which related organisms are placed.

Hierarchy of groups (taxa) from broadest to most specific

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

3 Domains, broadest, most inclusive taxon:

Archaea and Eubacteria--Unicellular prokaryotes (no nucleus or membrane-bound organelles), Eukarya--more complex and hae a nucleus and membrane-bound organelles


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

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

Classifying Humans...

Domain Eukarya --Cells with nuclei
Kingdom Animalia --Multicellular
Phylum Chordata  --vertebrates
Class Mammalia --Hair, mammary glands
Order Primates --Adapted to climb trees
Family Hominidae --Adapted to walk erect
Genus Homo -- Large brain to use
Species Homo sapiens --characteristics of modern day man.


This is just an example. There many other ways to classify organisms even though they have the same scientific name.