Classifying Today.09.ClassificationNotes#3
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  • Classification and Phylogeny Classification systems attempt to solve the problem of providing meaningful groupings of organisms. The Swedish scientist, Carolus von Linnaeus, is credited with introducing binomial nomenclature and hierarchical classification as an organized way of naming and describing organisms and their relationships to one another. Binomial nomenclature refers to the use of a two-part name for each species (one name designating genus and one designating species). Linnaeus described a hierarchical classification system using seven taxonomic categories, or taxa (Kingdom, Phylum, Class, Order, Family, Genus, Species). Beginning with species, each category becomes progressively more comprehensive. For example, while the leopard, tiger and domestic cat all belong to different genera, they are grouped together in the same family. Taxonomy is the science of classification. When taxonomic systems include hypothesized evolutionary relationships among groups, the field generally is referred to as systematics. Systematics can be thought of as the study of biological diversity and how that diversity evolved. In a sense, Charles Darwin introduced systematics in his revolutionary work, The Origin of Species . He wrote, “The natural system is founded on descent with modification; that the characters which naturalists consider as showing true affinity between any two or more species, are those which have been inherited from a common parent, and, in so far, all true classification is genealogical” (Darwin, 1859). References Campbell, Neil E. and Reece, Jane B. 2002. Biology, Sixth Edition . Benjamin Cummings. Darwin C. 1859. The Origin of the Species . London, England: Pengin Books. Image Reference:
  • Binomial Nomenclature Early naturalists identified plants and animals by observable structural similarities and referred to organisms using long complicated phrases. This was known as the “polynomial system.” In this system, a plant might be described by phrases of 12 or more words. It is not surprising that polynomial names could become very complex and were often misinterpreted when translated from one language to another. In the 1700s, Carolus von Linnaeus, sometimes referred to as the Father of Classification, described a binomial system, which was published in his early work, System Naturae (1735). Although he created the two-word system as a short-cut for users of this work, the system was rapidly adopted as a manageable way of naming species. In the binomial nomenclature system, genus and species —just two names—replace the long string of words used in the polynomial system. The meaning of words can differ from language to language and from country to country. For example, in Great Britain, the word “buzzard” refers to an organism Americans call a hawk. For this reason, scientific names are written in Latin to maintain a uniform system of naming across all languages. In the binomial system, genus is always a noun, underlined (or italicized), and capitalized; species is a descriptive term, underlined (or italicized), and not capitalized. Some examples of binomial names include: Quercus rubra (red oak), Panthera pardus (leopard), or Homo sapiens (human). References: Johnson, George B. and Raven, Peter H. 2004. Biology, Principles and Explorations . Holt, Rinehart, and Winston. Linne, Carl von. System Naturae . 1735. Nieuwkoop:De Graaf. Image reference:
  • Hierarchical Classification Carolus von Linnaeus created a hierarchical classification system using seven taxonomic categories, or taxa (Kingdom, Phylum, Class, Order, Family, Genus, Species). These categories are based on shared physical characteristics, or phenotypes, within each group. Beginning with kingdom, each successive level of classification becomes more and more specific. Organisms within the same order have more in common with one another than organisms within the same class. For example, all species of bears are mammals, but not all mammals are bears. A useful pneumonic tool to help students remember the hierarchical classification system is: “ K ing P hillip C ame O ver F or G reen S oup,” with the first letter of each word representing each category, beginning with kingdom and ending with species. References: Campbell, Neil E. and Reece, Jane B. 2002. Biology, Sixth Ed . Benjamin Cummings.
  • Taxonomic Diagrams Sometimes, biologists group organisms into categories that represent common ancestries, not just physical similarities. Early naturalists used physical characteristics and later, fossil data, attempting to represent evolutionary relationships among organisms. Today, modern classification systems use fossil data, physical characteristics and DNA/RNA information to draw increasingly more accurate branching diagrams. Phylogenetic trees, or phylogenies, represent hypothesized evolutionary relationships among organisms and may include extinct as well as modern species. Cladograms are based only on characteristics observable in existing species. The branching patterns in a cladogram are defined by the presence of unique, evolving innovations (derived characteristics) shared by all members of the group. References Campbell, Neil E. and Reece, Jane B. 2002. Biology, Sixth Edition . Benjamin Cummings. Judd, W.S., Campbell, C.S., Kellogg, E.S., Stevens, P.F., Monoghue, M.J. 2002. Plant Systematics: A Phylogenetic Approach, Second Edition . Sinauer Assoicates, Inc. Image References: Buffalo (Jack Dykinga), Alligator (USDA), Turkey (Scott Bauer) From USDA Agricultural Research Service Turtle, Snake Art Explosion, Volume 2 Clip Art
  • Dichotomous Keys of Identify Organisms Identification is the process of finding the named group to which an organism belongs. Dichotomous keys are useful tools to help identify different organisms and usually are found in field guides. Identification in the field is based on features that are observable to the eye; therefore, it is important to remember that a key is an identification tool and is not synonymous with phylogenetic diagrams, which communicate hypothesized evolutionary history. Dichotomous keys are constructed of contrasting pairs of statements. To use a dichotomous key, begin with the first pair of statements and follow the directions at the end of each statement until you reach the name of the organism you are trying to identify. With each new organism, always start at the beginning of the key (1a and 1b). The ability to use dichotomous keys is an important skill and should be incorporated into instruction throughout the year. It is important to note that when constructing a dichotomous key, each pair of contrasting descriptions must deal with the same characteristic. For example the margin of the leaf might be used for the first pair of descriptors, and the shape of the leaf might be used for another pair. An incorrect pair of statements might be: 1a) Is the leaf heart shaped? 1b) Are the edges lobed? References: Campbell, Neil E. and Reece, Jane B. 2002. Biology, Sixth Ed . Benjamin Cummings.


  • 1. TEXTBOOK: From Bacteria to Plants Chapter One: Living Things Section 3 “Classifying Organisms.” Pg. 28-37
  • 2. Classifying Organisms
    • Why do Scientists Classify?
    There are 2.5 million kinds of organisms on Earth. (including plants, animals and bacteria)
  • 3. Classification
    • — the process of grouping things based on their similarities.
  • 4. We classify
    • foods “dairy, meat, poultry, fruit, vegetables.”
    We classify music “rap, r&b, pop, country”
  • 5. Early Classification Systems
  • 6. Aristotle—
    • came up with the idea to use observations to classify animals by appearance, behavior, movement Fly      Swim      Walk, crawl run
  • 7. Classification and Phylogeny
    • Binomial Nomenclature
    • Hierarchical Classification
    • Systematics: Evolutionary Classification
    Populus tremuloides Quaking Aspen
  • 8.
    • Carolus von Linnaeus
    • Two-word naming system
      • Genus
        • Noun, Capitalized, Underlined or Italicized
      • Species
        • Descriptive, Lower Case, Underlined or Italicized
    Binomial Nomenclature Carolus von Linnaeus (1707-1778) Swedish scientist who laid foundation for modern taxonomy
  • 9. The Classification System of Linnaeus
    • Used observations as the basis of his system.
  • 10. Binomial nomenclature
    • each organism was given a two part name. Made of a genus and species name that identifies a certain organism.
  • 11. Genus
    • first part of name. A classification grouping that contains similar, closely related organisms.
  • 12. Species
    • 2 nd part of name. A group of similar organisms that can mate and produce fertile offspring in nature.
  • 13. Latin
    • genus and species names are in Latin language. This was the language all scientists communicated in.
  • 14. Italics and Capitalization
    • the complete scientific name is written in italics . The genus name is capitalized while the species name begins with a small letter. Example: Felis domesticus —house cat/ domestic cat
  • 15. Organisms
    • are grouped by their shared characteristics. First put in a broad group and then moved into more specific groups
  • 16. Hierarchical Classification
    • Taxonomic categories
    • 7 Levels of Classification
      • Kingdom K ing
      • Phylum P hilip
      • Class C ame
      • Order O ver
      • Family F or
      • Genus G reen
      • Species S oup
  • 17.
    • The more classification levels that two animals share, the more characteristics they have in common.
  • 18. Evolution and Classification
    • Charles Darwin published a theory about how species change over time.
  • 19.
    • It is proven that species can change over time (adaptations).
    • Ex. Humans get taller,
    • Ex. Bird’s beak gets more pointed.
  • 20.
    • It is not proven that organisms can change into other species,
  • 21. ex. A monkey into a person
  • 22. Evolution
    • the process by which species gradually change over time.
  • 23. Classification Today
    • Theory is that species are similar because they share a common ancestor.
  • 24.
    • Species with similar evolutionary histories are classified more closely together. i.      Get information about how species used to be from fossils
  • 25.  
  • 26.  
  • 27. Compare body structures and chemical makeup to fossils.
    • c. Compare body structures to other organisms
    • d. Compare early development of different organisms.
  • 28.
    • Ex. Humans and rabbits go through similar stages in their development before birth.
    This means they may share evolutionary history.
  • 29.
    • Primarily rely on info about the chemical makeup of cells to determine evolutionary history. The more closely related the 2 species, the more similar the chemicals that make up their cells are.
    chemical makeup of cells
  • 30. Using the Classification System
    • Taxonomic Key—a series of paired statements that describe the physical characteristics of different organisms.
  • 31. Taxonomic Diagrams Mammals Turtles Lizards and Snakes Crocodiles Birds Mammals Turtles Lizards and Snakes Crocodiles Birds Cladogram Phylogenetic Tree
  • 32. MONEY TAXONOMIC KEY 1 A. Metal....................................................go to 2 1 B. Paper....................................................go to 5 2 A. Brown (copper)........................................penny 2 B. Silver....................................................go to 3 3 A. Smooth edge...........................................nickel. 3 B. Ridges around the edge...............................go to 4 4 A. Torch on back..........................................dime 4 B. Eagle on back...........................................quarter 5 A. Number 1 in the corners...............................$1 bill 5 B. Number 2 in the corners...............................$2 bill Now, try to make your own taxonomic key (similar to the money taxonomic key). Make your key separate out each of the 5 kingdoms. Remember to use pairs of contrasting statements. Possible Answer (your answer may vary)                       
  • 33. 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.
  • 34. Identifying a leaf
      • 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
  • 35. Identifying an insect