Classification

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Classification

• - Chapter 17

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Why do we need to classify?

• Classifying things into groups helps us to see
  relationships and understand the world around us.
• Classification is one way that humans simplify
  life in a complex world
• The science of classification is called taxonomy
  or systematics.

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History of Taxonomy

• There are records of human attempts to classify
  organisms as far back as we can trace records.
• Ancient Chinese organized into groups such as
  fabulous ones, or ones that resemble flies
  from a distance
• Aristotle was the first to classify according to
  structural similarities. He had two groups
  Plants and Animals
• Today we tend to use evolutionary relationships
  to classify organisms

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History, cont

• There is no one perfect system of classification.
  The system we use today was developed by Carolus
  Linnaeus (1707-1778)
• Linnaeus was a Swedish botanist who was
  extraordinarily good at collecting, naming, and
  classifying organisms, especially plants.
• Linnaeus published his classification system in a
  book called
• Systema Naturae

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Development of Kingdoms

• Kingdoms are the largest divisions in taxonomy
• Aristotle -4th century B.C.- Two kingdoms-
• Plants and Animals
• Ernest Haeckel (1894) 3 kingdoms
• Plants, Animals, and Protista
• Herbert Copeland (1956) 4 kingdoms-
• Plants, Animals, Protista, and Bacteria

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• Robert Whittaker(1959) 5 kingdoms- Plants,
  Animals, Protista, Monera, and Fungi
• Carl Woese (1977) 6 kingdoms- Plants, Animals,
  Eubacteria, Archebacteria, Protista, and Fungi.
  This was the first system that used evolution and
  molecular genetics
• Woese also developed the Domain classification in
  1990. This was a major overhaul of the
  classification system. The three domain system
  is based on molecular biology and groups all
  organisms into three domains
• Bacteria, Archaea, and Eukarya

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Linnaeus System

• Linnaeus developed a two word naming system for
  organisms called binomial nomenclature.
• The scientific name of an organism is usually
  based on Latin or Greek and consists of two names
  Ex Homo sapien Ursus arctos
• The first name is the genus and is always
  capitalized and the second name is the species.
  The scientific name of an organism is typically
  italicized.

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Linnaeus developed seven taxonomic categories.
In order from the largest to the smallest they
are The more taxonomic categories a
species has in common, the more closely related
We currently use Eight categories with the
addition of domains in the 1990s. The Three
domains are Bacteria, Archaea, and Eukarya
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Evolutionary Classification

• Darwins theory of evolution changed how
  scientists looked at classification. Traditional
  Linnean classification did not take into account
  evolutionary trends.
• Today scientists use cladograms to show the
  evolutionary relationships among different
  organisms.

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Cladograms
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How do we classify?

• Scientists often use dichotomous keys to classify
  organisms.
• A dichotomous key is a forced choice system that
  gives you two choices as you move through a
  description of the characteristics of the organism

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Six Kingdom System
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KINGDOMS OF LIVING THINGSIN THE LINNAEAN
CLASSIFICION SYSTEM 

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Modern Evolutionary Classification

• Molecular clocks use DNA comparisons to estimate
  the length of time that two species have been
  evolving independently.
• This relies on the rate that neutral mutations
  accumulate in the DNA of different species

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Kingdoms and Domains

• Using new tools available today, scientists have
  expanded upon Linnaeuss system of
  classification.
• The 6 kingdom system of classification includes
  the kingdoms Eubacteria, Archaebacteria,
  Protista, Fungi, Plantae, and Animalia

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• Today, most scientists are now recognizing
  molecular evidence that requires the addition of
  a category even larger than kingdom the domain
• Domains
• Archaea
• Bacteria
• Eukarya

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