Classification

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Classification Diversity

• Biology 112

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Because there are so many known species, a system
of classification is needed for 3 reasons

• a. Organize species into groups and discuss them
• b. Identify new organisms
• c. Show relationships between organisms

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Taxonomy

• The science of classifying organisms

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Classification of Organisms
Kingdom
Phylum / Division
Class
Order
Family
Genus
Species
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The Binomial system

• Developed by Carolus Linnaeus
• Each organism is given a two part name using
  Latin as a standard language providing a uniform
  means of communication for all people. This
  avoids the confusion caused by organisms with
  different common names in different areas

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• The format is Genus species or G. species. e.g.,
  Castor canadensis
• Genus name is capitalized and may be abbreviated
  by the first initial. Species name is not
  capitalized and cannot be used alone. e.g., C.
  canadensis.

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• The 2 part name gives clues about relationships
  between organisms. For instance, Ursus
  americanus, U. horribilis, U. arctos, and U.
  maritimus are all related.

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• Names were based largely on physical appearances
  but modern taxonomists use genetic information,
  molecular biology, and phylogeny (historical
  evolution) as other criteria for classifying.

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• The work of Charles Darwin introduced the idea of
  considering evolutionary history

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The taxonomic hierarchy

• The binomial classification system is hierarchal.
  The levels of organization are kingdom, phylum,
  class, order, family, genus, species. In plants,
  fungi and algae phyla also called divisions. Each
  of these levels is called a taxon.

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Classification of Organisms
Kingdom
Phylum / Division
Class
Order
Family
Genus
Species
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• Note that the genus and species name are
  italicized because they are Latin. When
  handwriting, underline the words. Other levels
  are capitalized but no special print features are
  used

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What is a species?

• Capable of reproducing with one another
• Individuals of one species may appear quite
  dissimilar
• Offspring may appear different from one another

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• Individuals from different species do not
  generally reproduce with one another
• Estimates on the number of species range from 2
  and 100 million species on the planet although
  about 1.4 million species are currently named and
  described. Note that this is for eukaryotic
  species only. It is much more difficult to
  estimate the number of prokaryotic species.

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Kingdom System

• Originally there were only two kingdoms
  recognized animals and plants
• Later, these two were divided into five animals,
  plants, fungi, protists, and bacteria. Each
  kingdom evolved from different single-celled
  ancestors

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Most people now recognize 5 or 6 kingdoms

• Monera (Archaebacteria Eubacteria)
• Protists
• Fungi
• Animals
• Plants

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Phylogenetic Tree
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Prokaryotic or Eukaryotic

• Monera are prokaryotic
• Protists, Fungi, Plantae, Animalia are all
  Eukaryotic

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• There are greater differences between prokaryotes
  and eukaryotes than between plants and animals.

• Also, there is greater diversity between the two
  prokaryotic groups than among all eukaryotic
  groups.

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Evolution of Kingdoms

• Bacteria first appeared over 3 billion years ago
  and were the only organisms on Earth for about 2
  billion years
• Fungi, plants and animals are well-defined
  evolutionary groups, each having arisen from
  different unicellular ancestors

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Animalia - Chordata - Agnatha

• northern hemisphere parasitic species
  Ichthyomyzon unicuspis. The individual on the
  left is a male who was very near to spawning. The
  individual on the right is a female that was
  spawning when caught. Their total body lengths
  are approximately 18cm for the female and
  slightly larger for the male as he isn't spawning
  yet, around 22 cm.

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What do we know?

• What is taxonomy? Why is it important?
• What is meant by the term binomial nomenclature?
• What is a phylogenetic tree?

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Viruses - where do they fit?

• Viruses are not included in any of the six
  kingdoms
• Viruses are tiny structures and are called
  particles rather than cells. There is
  considerable debate as to whether they are alive
  or not

Influenza Virus
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• Herpes Zoster Virus (shingles)

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• They consist of a protein shell containing some
  genetic material with no organelles, no membrane
  of their own, and they do not divide
• They use the host organelles to reproduce

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What do we know?

• Why is a virus considered to occupy a position
  between living and nonliving matter?
• What is a bacteriophage?
• Why is it difficult to establish the phylogeny of
  viruses?