Taxonomy - the science of classifying organisms

Common Names

spider monkey	sea monkey	sea horse
gray wolf	Firefly	Crayfish
mud puppy	horned toad	Ringworm
black bear	Jellyfish

*Common names can be confusing and names can vary by region.

Why Classify?

About 1.5 million species named
2-100 million species yet to be discovered

Taxonomy =science of classifying organisms
--groups similar organisms together
--assigns each a name

Naming Organisms:
Organisms have common & scientific name -all organisms have only 1 scientific name
-usually Latin or Greek
-developed by Carolus Linnaeus

The scientific name is always italicized or underlined. Genus is capitalized. Species is not. Scientific names can be abbreviated by using the capital letter of the genus and a period: Example.P. leo (lion) Members of the same genus are closely related.  Only members of the same species can interbreed (under natural conditions) Some hybrids do occur under unnatural conditions: Ligers are crosses between tigers and lions.

This two-word naming system is called 

Binomial Nomenclature

-written in italics (or underlined)
-1st word is Capitalized --Genus
-2nd word is lowercase ---species

Examples: Felis concolor, Ursus arctos, Homo sapiens,Panthera leo , Panthera tigris 

Linneaus - devised the current system of classification, which uses the following schema

Kingdom
	Phylum/Division
		Class
			Order
				Family
					Genus
						Species

	Human	Cougar	Tiger	Pintail Duck
Kingdom	Animalia	Animalia	Animalia	Animalia
Phylum/Division	Chordata	Chordata	Chordata	Chordata
Class	Mammalia	Mammalia	Mammalia	Aves
Order	Primate	Carnivora	Carnivora	Anseriformes
Family	Homindae	Felidae	Felidae	Anatidae
Genus	Homo	Felis	Panthera	Anas
Species	sapiens	concolor	tigris	Acuta

18-2 Modern Evolutionary Classification

• Linnaeus grouped species mainly on visible similarities & differences
• Today, taxonomists group organisms into categories that represent lines of evolutionary descent (phylogeny)
• Evolutionary relationships among a group of organisms can be shown on a cladogram 

Similarities in DNA and RNA

• DNA & RNA is similar across all life forms
• Genes of many organisms show important similarities at the molecular level
• DNA shows evolutionary relationships & helps classify organisms

The Six Kingdoms and Domains

	number of Cells	Energy	cell type	Examples
archaebacteria	Unicellular	some autotrophic, most chemotrophic	Prokaryote	"extremophiles"
Eubacteria	Unicellular	autotrophic and heterotrophic	Prokaryote	bacteria, E. coli
Fungae	most multicellular	Heterotrophic	Eukaryote	mushrooms, yeast
Plantae	Multicellular	Autotrophic	Eukaryote	trees, grass
Animalia	Multicellular	Heterotrophic	Eukaryote	humans, insects, worms
Protista	most unicellular	heterotrophic or autotrophic	Eukaryote	ameba, paramecium, algae

Chart Used in Class

Using Dichotomous Keys

A dichotomous key is a written set of choices that leads to the name of an organism. Scientists use these to identify unknown organisms.

Consider the following animals. They are all related, but each is a separate species. Use the dichotomous key below to determine the species of each.

1.	Has green colored body ......go to 2
	Has purple colored body ..... go to 4
2.	Has 4 legs .....go to 3
	Has 8 legs .......... Deerus octagis
3.	Has a tail ........ Deerus pestis
	Does not have a tail ..... Deerus magnus
4.	Has a pointy hump ...... Deerus humpis
	Does not have a pointy hump.....go to 5
5.	Has ears .........Deerus purplinis
	Does not have ears ......Deerus deafus

Answers:

A. Deerus magnus
B. Deerus pestis
C. Deerus octagis
D. Deerus purplinis
E. Deerus deafus
F. Deerus humpis

*note that all of these organisms are in the same genus.