Introduction to Classification

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Introduction to Classification
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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.

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I. Classification Systems
A. Aristotle (almost 2000 years ago) ?
grouped organisms into two groups
Grouped based on general habitat Ex. land, air,
or water dwellers
Grouped based on the differences in stems Ex.
woody vs. herbaceous
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? Was Aristotles grouping system adequate? ?

• Problems with the system

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I. Classification Systems

• Carolus Linnaeus (mid 1700s) ?
• grouped organisms into seven levels ranging from
  general to specific

Kingdom Phylum Class Order Family Genus Species
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Acronyms
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Example Human Being
Kingdom Phylum Class Order
Family Genus Species
Animalia Chordata Mammalia Primate Hominidae Homo
Sapiens
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Some more examples
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I. Classification Systems

• Binomial Nomenclature ?
• The scientifc name of an organism, consists of
  two partsgenus species.

Scientific name must be either underlined or
italicized!
Examples Ursus horriblis Felis domesticus
Canis familiaris
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III. Alternate Forms of Classification
Heterotrophic
Autotrophic
Organisms that rely on outside sources for
nutrients (anything that has to eat!)
Organisms that can make their own food through
photosynthesis (plants).
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Prokaryotic
Eukaryotic
More complex cells with a true nucleus
and membrane- bound organelles ex. plants,
animals
Simple cells that lack a true nucleus and
membrane-bound organelles ex. bacteria
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• Dichotomous Keys
• A. Definition ? a chart consisting of a series
  of paired, opposite statements that help
  scientists to classify organisms.

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Some practicewhat 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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