Taxonomy - the science of classifying

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 (see 18-7 p. 452)

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.