Classification

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Classification

• Why do you think scientists like to put organisms
  into groups, like mammals or insects?

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What is Classification?

• Classification is the arrangement of organisms
  into orderly groups based on their similarities
• Classification is also known as taxonomy
• Taxonomists are scientists that identify name
  organisms
• Taxonomists classify organisms into groups called
  taxon

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Why Classify?

• Scientists have classified about 2 million
  species
• However, there are many more organisms than we
  have found.
• Estimates usually range from 3-10 million, but go
  as high as 50 million
• That shows Earth has a tremendous amount of
  biodiversity(variety of organisms)
• This is only 1-5 of all organisms that have ever
  lived!!!!!

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Why Classify?

• Accurately uniformly names organisms
• Prevents misnomers such as starfish jellyfish
  that aren't really fish
• Uses same language (Latin or some Greek) for all
  names

Sea horse??
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Confusion in Using Different Languages for Names
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Latin Names are Understood by all Taxonomists
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Early Taxonomists

• 2000 years ago, Aristotle was the first
  taxonomist
• Aristotle divided organisms into plants animals
• He subdivided them by their habitat ---land, sea,
  or air dwellers

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Carolus Linnaeus 1707 1778

• 18th century taxonomist
• Classified organisms by their structure
• Developed naming system still used today

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Carolus Linnaeus

• Called the Father of Taxonomy
• Developed the modern system of naming known as
  binomial nomenclature
• Two-word naming system

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Binomial nomenclature

• Genus species
• Latin or Greek
• Capitalize genus, but NOT species
• Underline when writing
• Italicized in print

• American Robin

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Binomial nomenclature

• The International Code for Binomial Nomenclature
  contains the rules for naming organisms
• All names must be approved by International
  Naming Congresses (International Zoological
  Congress)
• This prevents duplicated names
• Organisms are often named using descriptive
  words, like habitat or a physical characteristic
  OR sometimes using the person whom discovered
  them

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Levels of Classification

• The levels of classification are a hierarchy of
  groups (taxa) from broadest (domain) to most
  specific (species)

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Levels of Classification

• Domain
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

• Sometimes subspecies is added to the bottom of
  the list
• Subspecies are the same species, but they live in
  different areas

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• King
• Phillip
• Came
• Over
• For
• Good
• Soup!

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Systematics

• Systematics is a science whose goal is to
  classify organisms in terms of their natural
  relationships
• Phylogenetics is a type of systematics

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Phylogenetics

• The analysis of the evolutionary or ancestral
  relationships among taxa.
• Classification is based on evolutionary
  relationships
• Found by studying RNA, DNA, amino acids,
  homologous structures, and embryos
• These relationships are often shown in a
  cladogram

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Cladistics

• Cladisticsis a type of phylogenetics
• A cladogram is a type of phylogenetic diagram

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Cladistics

• Cladogram-A diagram showing how organisms are
  related based on shared, derived characteristics
  such as feathers, hair, or scales
• Shared characters are features that ALL members
  of a group have in common.
• For example, all organisms in the Domain Eukarya
  domain have true nuclei
• Derived characters are features that evolved only
  in the group under consideration.
• Feathers for example, are believed to have
  evolved only in the birds, not from a common
  ancestor that they have with reptiles.

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Cladistics

• Cladograms are organized into clades, which is an
  ancestor and all of its descendants.
• Cladograms are not only based on physical
  features, they are also based on biomolecular
  similarities (like DNA, chromosomes and proteins)
• Outgroups-have no shared characteristics with the
  other organisms in the diagram and are only
  distantly related

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Cladogram

• Feathers are a derived characteristic in the
  birds
• Hagfish are the outgroup
• Jaws are a shared characteristic between all
  organisms except the hagfish

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Cladogram

• Hair is a derived characteristic in leopards (on
  this cladogram, only leopards have hair)
• NOTE-hair is a shared characteristic in the
  previous cladogram, so these characteristics can
  change based on the cladogram
• Character tables may help you make cladograms

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Dichotomous Keys

• Used to identify organisms
• "Dichotomous" means "divided into two parts".
• Characteristics given in pairs
• Read both characteristics and either go to
  another set of characteristics OR identify the
  organism

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Dichotomous Keys

• Always read both choices, even if the first seems
  to be the logical one at first.
• Be sure you understand the meaning of the terms
  involved. Do Not Guess.
• When measurements are given, use a calibrated
  scale. Do Not Guess.
• Since living things are always somewhat variable,
  do not base your conclusion on a single
  observation. Study several specimens to be sure
  your specimen is typical.
• If the choice is not clear, for whatever reason,
  try both divisions. If you end up with two
  possible answers, read descriptions of the two
  choices to help you decide

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Dichotomous Keys

• 1. a. Bean round..Garbanzo bean
• b. Bean elliptical or oblong..Go to 2
• 2. a. Bean whiteWhite northern
• b. Bean has dark pigmentsGo to 3
• 3. a. Bean solid in color.Go to 4
• b. Bean is spotted...Pinto bean
• 4. a. Bean black........Black bean
• b. Bean reddish-brown.Kidney bean

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Making Dichotomous Keys

• Eliminate an organism in every step (one part
  leads to a name, the other part leads to another
  step)
• Use measurements rather than terms like "large"
  and "small".
• Try to make the choice a positive one -something
  "is" instead of "is not".

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Making Dichotomous Keys - Continued

• If possible, start both choices of a pair with
  the same word.
• If possible, start different pairs of choices
  with different words.
• Precede the descriptive terms with the name of
  the part to which they apply.(like legs are red
  instead of red legs)

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DICHOTOMOUS KEY ASSIGNMENT

• You will be creating your own dichotomous key
• The subjects of the key will be all the people in
  your row of desks
• Criteria must be high school appropriate and
  non-insulting
• Everyone should have between 7 10 people