introduction to classification. a. what is taxonomy ? the branch of biology that groups organisms...
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Introduction to Classification
A. What is taxonomy? The branch of biology that groups organisms based on common characteristics.
I. Introduction
B. Why do scientists classify? Over 1.5 million species have been identified. Biologists classify to organize and study these organisms.
Animals
A. Aristotle (almost 2000 years ago) grouped organisms into
two groups:
Grouped based on general habitat
Ex. land, air, or water dwellers
Plants
I. Classification Systems
Grouped based on the differences in stems
Ex. woody vs. herbaceous
Was Aristotle’s grouping system adequate?
Problems with the system…
B. Carolus Linnaeus (mid 1700’s) grouped organisms into seven levels ranging from general to specific:
I. Classification Systems
Kingdom
Phylum
Class
Order
Family
Genus
Species
Acronyms…
Example:
Human Being =
Kingdom:
Phylum:
Class:
Order:
Family:
Genus:
Species:
Animalia
Chordata
Mammalia
Primate
Hominidae
Homo
Sapiens
Some more examples…
C. Binomial Nomenclature The scientifc name of an organism, consists of two parts…genus & species.
I. Classification Systems
**Scientific name must be either underlined or italicized!**
Examples:
Ursus horriblis =
Felis domesticus =
Canis familiaris =
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Organisms that rely on outside sources for nutrients (anything that has to eat!)
Organisms that can make their own food through photosynthesis (plants).
III. Alternate Forms of Classification:
Heterotrophic Autotrophic
More complex cells with a true nucleus
and membrane- bound
organellesex. plants, animals
Simple cells that lack a true nucleus and membrane-bound organellesex. bacteria
Prokaryotic
Eukaryotic
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IV. Dichotomous Keys
A. Definition a chart consisting of a series of paired, opposite statements that help scientists to classify organisms.
Head
Abdomen
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
Some practice…what is it?
A pseudoscorpion!
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