Download Chapter 18 Classifcation - Morgan Park High School

Chapter 18: Classification and Taxonomy
Linnaeus and Beyond
Why Classify?
• Biologists have identified and named about 1.5
million species and they estimate that anywhere
between 2 and 100 million additional species
have yet to be discovered
• To study the diversity of life, biologists use a
classification system to name organisms and
group them in a logical manner.
• Taxonomy: discipline where scientists classify
organisms and assign each organism a
universally accepted name.
Assigning Scientific Names
• Carl Linnaeus (1700s)
• Scientific names are assigned based on Linnaeus’ two
part naming system called binomial nomenclature. Each
name includes the Genus and species names. Scientific
names are either written in italics or underlined.
• Rules for creating a scientific name:
– 1. No other species may possess the same name.
– 2. The name must be derived from Latin and in some cases
ancient Greek.
– 3. Provide a descriptor of the organism.
– 4. The name must include the genus name.
• Organisms that share important characteristics are
classified together and organized into groups called taxa
(taxon=singular).
Linnaeus’s System of Classification
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There are 7 taxa:
Kingdom (the largest and most general group)
Phylum
Class
Order
Family
Genus
Species (the smallest and most specific group)
The only taxon that has a clear biological identity is
species. A species share a common gene pool and are
actually or potentially interbreeding natural populations
which are reproductively isolated from other such
groups.
Modern Evolutionary Classification
• Linnaeus’s system of classification had limitations and
problems. Despite being able to classify thousands of
species into taxa, it did little to account for the effect of
evolution.
• Evolutionary classification was developed to show the
common characteristics between organisms and how
they developed over time.
• Taxonomists today do not solely classify bases on
anatomical similarities. Instead they look at evolutionary
closeness and genetic similarities. Taxonomists look at
nucleotide sequences of DNA and RNA on amino acid
sequences of the proteins
• Evolutionary classification is diagrammed in a chart
called a cladogram.
A Basic Cladogram
Cladogram of Life
Cladogram Vocabulary
• Taxon- Level of organization.
• Roots- The dots. They represent where a
trait begins.
• Branchs- The lines. They represent a
common thread between organisms.
• Terminal Node- Where a Branch ends.
• Internal Node- Where a Branch begins.
• Outgroup- A group that is removed from
the common root.
How to Interpret Advanced
Cladograms…
 Time
Cladogram Type I
Cladogram Type II