Classification Systems

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Classification Systems

• In general, classification is a method for
  organizing information. We tend to classify
  things spontaneously. As an example after seeing
  enough examples of tables, we form a
  classification in which any given object is
  either a table or a non-table. Given a new object
  we do remarkably well at deciding whether it is a
  table. Although there is little scientific value
  in this particular classification, it illustrates
  their omnipresence.

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• ARISTOTLE (384-322 BC) is often called the father
  of biological classification. His classification
  scheme referred to common groups, such as birds,
  fishes, whales, and bats, and he recognized the
  need for groups and group names in the study of
  the animal kingdom. But his system was based on
  the knowledge that was available in his day. 
  John RAY (1627-1705) used anatomical differences
  as the prime rule for classification, bringing
  out both the alikeness and differences between
  groups--for example, lungs or gills. This is
  still a preferred method for identification of
  organisms.

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Classifications Group Similar Things Together

• In general, classifications similar things are
  grouped together. This definition is by
  definition vague there are many reasonable ways
  of defining similarity, and hence many different
  classifications for the same things. In the
  example of tables, we considered the relationship
  (similarity) of objects to an abstract definition
  of table. This definition was based on a
  potential function of the object. In choosing to
  classify by "tableness", we assign less
  importance to other properties - color, hardness,
  age, etc. - that can vary without altering the
  utility of the object as a table.

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• The intended use of a classification is an
  integral part of deciding what properties it
  should be based upon. Here are some other
  classifications that you have encountered the
  books in a library - often the library will use a
  dewey decimal system to make it easy to find
  specific books and titles.  A visit to a large
  library will clearly demonstrate a need for such
  a system and a hardware store (organized by
  purpose of use - painting, hardware, lumber,
  seasonal, etc...).

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Classifications are often arranged in a Hierarchy

• A key property of classifications is that they
  can be nested within one another, creating an
  hierarchy. Thus, any group within a
  classification can be split in still greater
  detail. For example, objects that have been
  classified as Tables might be subdivided into
  Kitchen tables, Picnic Tables, Desks, etc.
  Similarly, listings in a telephone directory are
  first classified by the Community, and then
  within each of these categories they are further
  classified alphabetically.

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• There is no limit to the depth of a hierarchical
  classification. Most only have a few levels, but
  there are some that go quite far. When
  alphabetical order is considered carefully, it is
  seen that the first level of classification deals
  only with the first letter of each word. Then all
  words starting with the same first letter (for
  example "c") are categorized by their second
  letter, adding a second level to the alphabetical
  classification. This process continues one letter
  at a time until all words have been
  distinguished.

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Why Do We Classify Organisms?

• Biologists group organisms to represent
  similarities and proposed relationships.
• Classification systems change with expanding
  knowledge about new and well-known organisms.

Tacitus bellus
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Classification and Phylogeny

• Binomial Nomenclature
• Hierarchical Classification
• Systematics Evolutionary Classification

Populus tremuloides Quaking Aspen
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Binomial Nomenclature

• Carolus von Linnaeus
• Two-word naming system
• Genus
• Noun, Capitalized, Underlined or Italicized
• Species
• Descriptive, Lower Case, Underlined or Italicized

Carolus von Linnaeus(1707-1778) Swedish
scientist who laid foundation for modern taxonomy
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Biological Classification and the Linnaean
System.

• Linnaeus defined the biological classification
  system that we still use for plants and animals,
  and, with relatively minor modifications, for
  fungi and microorganisms. It is a hierarchical
  system that starts with a few categories at the
  highest level, and further subdivides them at
  each lower level.
• In the Linnaean system, to uniquely name a
  species it is necessary to supply both the genus
  and species. In the case of animals, Linnaean
  classifications often reflect our natural sense
  of similarity.

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• Think about a Polar Bear.  Develop a mental image
  of it. How would you describe it to someone who
  has never seen one? Take a moment to consider
  carefully . . .

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• Very likely your mental image was a visual one
  like the picture. Humans primarily emphasize
  traits that we can see as our primary source of
  information is our sense of sight. However, there
  is no reason that a polar bearor any other
  organism could not be described in terms of
  touch, smell, and/or sound as well. Think about
  an polar bear again but this time in terms of
  non-visual traits . . .

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• Not surprisingly, biologists also classify
  organisms into different categories mostly by
  judging degrees of apparent similarity and
  difference that they can see. The assumption is
  that the greater the degree of similarity, the
  closer they are related in a biological sense.

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• On discovering an unknown organism, researchers
  begin their classification by looking for
  features that seem to have the same function as
  those found on other species. Next it will have
  to be determed whether or not the similarities
  are due to an independent evolutionary
  development or to a common ancestor. If the
  latter is the explanation, then the two species
  are probably closely related and should be
  classified into the same or near biological
  categories.
• Homologies are physical features, of different
  organisms, that have a similar appearance or
  function because they were inherited from a
  common ancestor that also had them. For instance,
  the forelimb of a bear, the wing of a bird, and
  your arm have the same functional types of bones
  as did our shared reptilian ancestor--these are
  homologous structures. The more homologies two
  organisms possess, the more likely it is that
  they have a close genetic relationship.

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• Listing characteristics that distinguish one
  species from another has the effect of making it
  appear that the species and their distinctive
  attributes are fixed and eternal. We must always
  keep in mind that they were brought about by
  evolutionary processes that operated not only at
  some time in the past, but which also continue to
  operate today and will undoubtedly give rise to
  new forms in the future.

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• We also need to realize that most species are
  genetically diverse. When you think of an animal,
  such as the moose shown below, and describe it in
  terms of its specific traits (fur color patterns,
  Antler shape, etc.), it is natural to generalize
  and to think of all Moose that way. To do so,
  however, is to ignore the reality of variation in
  nature.

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Linnaean Nomenclature

• The standard nomenclature for species is
  attributed to Carolus LINNAEUS (1707-1778). He
  applied it consistently to plants in Species
  Plantarum (1753), and to animals in Systema
  Naturae (10th ed., 1757). Linnaeus' system was
  readily applicable to the new concept of
  evolution of Charles DARWIN, which was published
  in On the Origin of Species (1859).
• Darwin put forth the theory that organisms evolve
  by the process of natural selection. The theory
  had no immediate effect on existing
  classifications themselves, but it provided a new
  explanation and foundation for the classification
  schemes being used.  The closer together
  organisms were classified, the closer in
  evolutionary history they would be linked. This
  approach is key to modern classification schemes.

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• The Linnaean method for classification of living
  things groups organisms together based on
  presumed similarites in structures (Homologies).
  The assumption is that the more homologies the
  organisms in question share, the closer they must
  be in terms of evolutionary distance. The larger,
  more inclusive divisions of the Linnaean system
  (beyond species) are created by including
  together closely related groups of the
  immediately lower divisions. The result is a
  pyrimidal system of classification with the
  highest category consisting of all living things.
  The lowest category consists of a single species.
  Each of the categories above species can have
  numerous subcategories.

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• Linnaeus arranged classification categories as a
  series of nested groups. His sequence from
  broadest to smallest category is Kingdom,
  Phylum, Class, Order, Family, Genus, and Species.
  To remember this order you need only to remember
  the following
• King (Kingdom) Philip (Phylum) Came (Class) Over
  (Order) For (Family) Good (Genus) Soup (Species)

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• Related groups of organisms were determined by
  the many shared characteristics especially those
  having to do with maintenance, feeding, and
  digestion.
• The basic  unit in the Linnaean classification of
  living forms is the species (plural, species).
  Each species is given a unique, two part Latin
  name the name is always underlined or italicized
  in print. The name consists of the genus, which
  is a group of species more closely related to one
  another than to any other group, followed by the
  specific name, which identifies a particular
  species within a genus. The first letter of the
  genus is capitalized, while the specific name is
  in lowercase, as in Felis domesticus (House Cat)
  and Salmo salar(Atlantic Salmon). The binomial
  species name replaced the much longer
  descriptions of earlier classifications.

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• Linnaeus named groups of organisms for the
  defining characters that he noticed. For example,
  the name Mammalia to the group of animals that
  possess mammary glands and secrete milk to
  nourish their young. He also recognized that
  monkeys are most nearly like humans, and as a
  logical consequence of strictly biological
  classification, humans would be grouped not only
  in the class Mammalia but in the same
  representative division with the monkeys and
  apes.

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Hierarchical Classification

• Taxonomic categories
• Kingdom King
• Phylum Philip
• Class Came
• Order Over
• Family For
• Genus Green
• Species Soup

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Kingdoms and Domains
The three-domain system
Bacteria
Archaea
Eukarya
The six-kingdom system
Bacteria
Archaea
Protista
Plantae
Fungi
Animalia
The traditional five-kingdom system
Monera
Protista
Plantae
Fungi
Animalia
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SystematicsEvolutionary Classification of
Organisms

• Systematics is the study of the evolution of
  biological diversity, and combines data from the
  following areas.
• Fossil record
• Comparative homologies
• Cladistics
• Comparative sequencing of DNA/RNA among organisms
• Molecular clocks

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Taxonomic Diagrams
Mammals
Turtles
Lizards and Snakes
Crocodiles
Birds
Mammals
Turtles
Lizards and Snakes
Crocodiles
Birds
Cladogram
PhylogeneticTree
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Dichotomous Keys Identify Organisms

• Dichotomous keys versus evolutionary
  classification
• Dichotomous keys contain pairs of contrasting
  descriptions.
• After each description, the key directs the user
  to another pair of descriptions or identifies the
  organism.
• Example 1. a) Is the leaf simple? Go to 2 b)
  Is the leaf compound? Go to 3
• 2. a) Are margins of the leaf jagged? Go to
  4 b) Are margins of the leaf smooth? Go to 5

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Biological Classification

• Biological classification is the arrangement of
  organisms into categories that express their
  PHYLOGENY, or line of descent, based on
  information such as structure, development,
  biochemical  functions, and evolutionary history
  of organisms. The purpose of such a
  classification is to provide a clear and
  practical way to organize and communicate
  information about organisms. Classification can
  show relationships between different ancient and
  modern groups, indicate the evolutionary pathways
  along which present-day organisms may have
  developed, and provide a basis for comparing
  experimental data about different plant and
  animal groups. Organisms included in a group
  share a common genetic heritage in their genetic
  material, and they must be more closely related
  to each other than they are to the members of
  other groups of the same rank. However,
  classifications of organisms are modified as new
  information comes forward and as a result the
  phylogeny would change.

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• Taxonomy is the theory and practice of
  classifying organisms. The first scheme for
  classifying animals into logical groupings may
  have been proposed by Aristotle more than 2,000
  years ago. Since that time, many new systems have
  been proposed none, however, has succeeded in
  fitting all plants, animals, and microorganisms
  into a single, completely satisfactory scheme.
  For example, some taxonomists classify algae with
  the protista or consider them plants. Recently,
  biotechnological techniques have enabled
  researchers to compare the DNA of various
  organisms to decipher the phylogeny of some
  organisms and helped to distinguish some closely
  related species with similar appearance.

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• Assigned activities
• Read the Following Pages from McGraw Hill Ryerson
  
• 108 - 109
• Complete the Mini Lab on Page 109 - Organizing
  Life
• Complete the Laboratory Exercise on Page 110 -
  111 Creating a Dichotomous Key

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Taxonomy

• What does this word mean?

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Definition of taxonomy

• It is the science of classification
• It deals with organizing
• Similar to the way in which you might organize
  your desk at home

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Desk

• Top drawer might have all your writing utensils,
  sharpeners, erasers, etc.
• The top side drawer might have all of your paper
  in it and perhaps some envelopes
• The next drawer down might have some drawing
  tools, e.g. compass, ruler, protractor
• What have you really done in organizing your desk
  this way?

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Organizing

• There are many ways to organize a room, a desk, a
  closet
• In the desk above, we put things together that
  were similar in there usage
• In a closet, you might organize clothes according
  to color or type of article
• Can you think of any other ways to organize
  different types of things?

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Usefulness

• Helps when dealing with large numbers of
  organisms
• Will allow you to find something easier
• Might help someone who is unfamiliar with the
  items learn them easier

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Systems

• Early

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Aristotle

• Simple
• Used 2 kingdoms
• Plant
• Animal

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Plants according to Aristotle

• Herbs
• Shrubs
• Trees

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Animals according to Aristotle

• Land-dwelling
• Air-dwelling
• Water-dwelling

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Problems

• Do you see any problems with this type of system?

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Carolus Linnaeus

• Sometimes called the Father of Modern Taxonomy
• His basis for classification was structure

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Scheme

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

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Memorizing Help

• King Phillip Came Over For General Science
• Each group gets smaller and smaller in the
  numbers of organisms it contains
• Within each group, the organisms get more similar
  as you go from Kingdom to Species

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Scientific Names (Binomial Nomenclature)

• The scientific name of an organism is composed of
  the Genus and Species names of that organism

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Lets Look at Man

• Kingdom - Animalia
• Phylum - Chordata
• Class - Mammalia
• Order - Primate
• Family - Hominidae
• Genus - Homo
• Species - Sapiens

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Man (contd)

• We are in the kingdom Animalia with all the other
  animals of the World
• We are in this species Sapiens only with
  ourselves
• Our scientific name is
• Homo sapiens
• This is the only correct way to write this name

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Species

• Two organisms are members of the same species if
  they can mate and produce fertile offspring
• Two organisms can have the same species names and
  not be in the same species
• Scientific names are reversed of ours
• Your last name is a family name usually based on
  your fathers last name
• Your first name is a given name that your parents
  pick for you

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Species (contd)

• If you discover a new organism, you are given the
  right to name that organism
• It will be in a given genus based on structure
  and other criteria (modern system)
• You assign a species name (maybe yours the state
  or country where discovered a prominent color,
  etc.)

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Modern System of Taxonomy

• Based mostly on evolution
• What organisms have evolved from what other
  organisms

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Kingdoms in Modern System

• Monera
• Protista
• Fungi
• Plantae
• Animalia