1. Introduction to Classification

2. I. Introduction What is taxonomy? 
The branch of biology that groups organisms based on common characteristics.
Why do scientists classify? Over 1.5 million species have been identified. Biologists classify to organize and study these organisms.

3. I. Classification Systems
A. Aristotle (almost 2000 years ago)  grouped organisms into two groups:
Plants
Animals
Grouped based on the differences in stems
Ex. woody vs. herbaceous
Grouped based on general habitat
Ex. land, air, or water dwellers

4.  Was Aristotle’s grouping system adequate? 
Problems with the system…

5. I. Classification Systems
Carolus Linnaeus (mid 1700’s) 
grouped organisms into seven levels ranging from general to specific:
Kingdom
Phylum
Class
Order
Family
Genus
Species

6. Acronyms…

7. Example:
Human Being =
Kingdom:
Phylum:
Class:
Order:
Family:
Genus:
Species:
Animalia
Chordata
Mammalia
Primate
Hominidae
Homo
Sapiens

8. Some more examples…

9. **Scientific name must be either underlined or italicized!**
I. Classification Systems
Binomial Nomenclature 
The scientifc name of an organism, consists of two parts…genus & species.
**Scientific name must be either underlined or italicized!**
Examples:
Ursus horriblis =
Felis domesticus =
Canis familiaris =

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11. Heterotrophic Autotrophic III. Alternate Forms of Classification:
Organisms that rely on outside sources for nutrients (anything that has to eat!)
Organisms that can make their own food through photosynthesis (plants).

12. Prokaryotic Eukaryotic
Simple cells that lack a true nucleus and membrane-bound organelles
ex. bacteria
More complex cells with a true nucleus
and membrane bound organelles
ex. plants, animals

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14. Dichotomous Keys
A. Definition  a chart consisting of a series of paired, opposite statements that help scientists to classify organisms.

15. Some practice…what is it?
Head
Abdomen
Some practice…what is it?
A pseudoscorpion!
TAXONOMIC KEY
Step 1
1a. Has 8 legs ………………………………………………………….. Step 2
1b. Has more than 8 legs Step 3
Step 2
2a. Has one oval-shaped body ……………………………………Step 4
2b. Has two body regions Step 5
Step 3
3a. Has one pair of legs on each body segment …………… Centipede
3b. Has two pairs of legs on each body segment Millipede
Step 4
4a. Is less than 2 millimeter long …………………………………. Mite
4b. Is more than 1 millimeter long Tick
Step 5
5a. Has clawlike pincers ………………………………………….. Step 6
5b. Has no clawlike pincers Spider
Step 6
6a. Has a long tail with a stinger………………………………….. Scorpion
6b. Has no tail or stinger Pseudoscorpion

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