Unit 8 Classification

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Unit 8 Classification

• Chapter 18

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Why classify?

• 1.5 billion known species exist in the world
• To study the diversity of life
• To name organisms
• To group them in a logical manner
• Taxonomy process of classifying organisms

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Assigning Scientific Names

• Binomial Nomenclature
• Created by Charles Linnaeus
• Two word naming system
• Written in italics
• First word capitalized, second lower case
• First word genus, second species

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Classification according to Linnaeus

• System uses 7 categories (taxons)
• Largest to smallest Kingdom, phylum, class,
  order, family, genus, species
• Grouped according to similarities

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Flowchart
Section 18-1
Linnaeuss System of Classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Figure 18-5 Classification of Ursus arctos
Section 18-1
Abert squirrel
Grizzly bear
Black bear
Giant panda
Coral snake
Red fox
Sea star
KINGDOM Animalia
PHYLUM Chordata
CLASS Mammalia
ORDER Carnivora
FAMILY Ursidae
GENUS Ursus
SPECIES Ursus arctos
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Modern Evolutionary Classification

• Previous system was largely based on anatomy and
  created some problems
• Change brought by Darwins findings
• Scientist now group according to similarities and
  lines of evolutionary descent

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Evolutionary Classification

• Group organisms in categories based on lines of
  descent, not just physical similarities
• Cladistic analysis identifies and considers new
  characteristics (derived characters) that have
  arise as lineages evolve
• Cladogram diagram showing evolutionary
  relationships among organisms
• Diagram of evolutionary tree

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Section 18-2
Traditional Classification Versus Cladogram
Appendages
Conical Shells
Crustaceans
Gastropod
Crab
Barnacle
Limpet
Crab
Limpet
Barnacle
Molted exoskeleton
Segmentation
Tiny free-swimming larva
CLASSIFICATION BASED ON VISIBLE SIMILARITIES
CLADOGRAM
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Classification based on DNA

• Many organisms share important similarities on
  the molecular level (DNA)
• Organisms grouped in categories of similar
  genetic makeup
• Molecular clocks DNA comparisons are used to
  estimate the length of time two organisms have
  been evolving independently