CLASSIFICATION

DIVERSITY OF LIFE

Taxonomy

• Branch of biology that names groups of organisms according to their characteristics and evolutionary history

History of Taxonomy• Aristotle (385-322 BC) classified

organisms into two main groups and then subclassified them into three categories

I. PlantsI. HerbsII. ShrubsIII. Trees

II. AnimalsI. LandII. Sea III. Air

Why is that method inadequate in classifying organims?

Linnaeus System of Classification

• Developed by Carlos Linnaeus (Sweedish Naturalist) (1707-1778)

• Grouped Organisms by:– Hierarchal Classification– Used morphology

(Physical Appearance)

Evolutionary pattern

Hierarchal Classification

Kingdom

Phylum

Class

Order

Family

Genus

SpeciesPneumonic Device:

Kings Play Cards Often For Great Splendor

Address Analogy

Your NameRm A303

200 Horace Mann AveRed Lion, PA

USALabel the parts of an address as they would relate to the

following classifications:Kingdom, Phylum, Class, Order,

Family, Genus, Species

Why is this method more accurate than Aristotle’s method?

Binomial Nomenclature• Two word system to identify the species

Homo sapien or Homo sapien

Four requirements of Binomial Nomenclature

1. Always Latinized 2. Genus always capitalized; species identifier

never capitalized3. Written in italics or underlined4. Always need both words

Genus name Species Identifier

Species Named By:

• Description: Homo sapien = wise human

Chaos chaos = amoeba

• Honor person: Linaea borialis = flower species native of Canada

• Geographic Range:Lynx canadensis

Sytematics and phylogeny• Systematics: method of organizing

diversity of living things in context of their natural relationship

• Phylogeny: Evolutionary history of species or taxonomic group

• Phylogenic Tree: A diagram that displays the evolutionary history and relatedness of a group of organisms

Phylogenic Tree

Morphological ComparisonBrine Shrimp

Frog

Human

Sea Urchin

Tapeworm

Embryological Comparison

Sea Urchin

Brine Shrimp

Frog

Human

Tapeworm

Molecular Comparison

Sea Urchin

Tapeworm Brine Shrimp

Frog Human

Sea Urchin X 165 135 117 117

Tapeworm 165 X 187 180 179

Brine Shrimp

135 187 X 159 157

Frog 117 180 159 X 44

Human 117 179 157 44 X

# of DNA nitrogen base sequence differences in a segment of DNA

Lines of evidence used in systematics

• Fossil record– Provides basic framework and order– Lack of consistent records= inadequate method

• Morphology– Physical features used to determine relatedness

• More homologous traits= more related

• Analogous features can make this inadequate

Embryological development

• Uses pattern of development to determine relatedness

• Similar organisms tend to share more developmental similarities than adult morphology

• Disadvantage: environmental influences and the inability to see development lead to inaccuracies

Molecular evidence • Compare subcellular molecules like DNA,

RNA, proteins to determine relatedness– Examples:

• # Amino acid differences

• Karyotype

• DNA & RNA sequence= less difference= more related

– Most accurate method b/c dealing with genetics