5.5 Classification


http://www.biologyforlife.com/IB%20Biology/Units/Classification%20and%20Diversity/Classification%20and%20Diversity.htm

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= =Taxonomy - the science of classifying=
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Common Names





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
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 Five Kingdoms


number of Cells
energy
cell type
examples
Prokaryote
unicellular
some autotrophic, most chemotrophic
some heterotrophic
prokaryote
"extremophiles"
bacteria





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.

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  • Scientists use these to identify unknown organisms.
  • Scientists also use dichotomous keys to create a classification for a known organism
Consider the following animals. They are all related, but each is a separate species. Which is which? Use the dichotomous key below to determine the species of each.===
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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




Another example - in this case you classify according to known characteristics


Taxoexternal image dichotomous.gif