Taxonomic Keys: Types, Merits, Demerits
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Questions and Answers

What is the primary purpose of a taxonomic key?

  • To identify unknown species based on observed features (correct)
  • To confuse the user with contradictory statements
  • To provide only one choice to the user
  • To list all possible characteristics of a specimen
  • In a taxonomic key, what is a 'couplet'?

  • A contradictory statement leading to rejection
  • A set of choices at each branching point (correct)
  • A summary of all the characteristics of a specimen
  • A term used to describe large and small features
  • What differentiates a dichotomous key from a polytomous key?

  • The rejection of one choice in polytomous keys
  • The use of large and small measurements in dichotomous keys
  • The presence of multiple choices at each branching point in polytomous keys (correct)
  • The use of seasonal characteristics in dichotomous keys
  • Which of the following is a constructive feature of taxonomic keys?

    <p>Utilizing constant characteristics rather than variable ones</p> Signup and view all the answers

    Why should proper measurements be used in taxonomic keys instead of terms like 'large' and 'small'?

    <p>To ensure accuracy and avoid ambiguity in identification</p> Signup and view all the answers

    What are the two types of taxonomic keys mentioned in the text?

    <p>Dichotomous and Poly clave keys</p> Signup and view all the answers

    Who is credited with probably first publishing dichotomous keys in 1778?

    <p>Jean Baptiste-Lamarck</p> Signup and view all the answers

    In dichotomous keys, contrasting characters are chosen to do what with the full set of possible species?

    <p>Divide them into smaller and smaller groups</p> Signup and view all the answers

    What is the purpose of providing both choices side-by-side in bracketed keys?

    <p>To make it easier to see relationships</p> Signup and view all the answers

    What is one of the advantages mentioned for using dichotomous keys?

    <p>Faster to use</p> Signup and view all the answers

    Study Notes

    Taxonomic Keys

    • A taxonomic key is a device used for identifying unknown species, consisting of a series of contrasting statements to make comparisons and identifications.

    Constructive Features of Taxonomic Keys

    • Constant characteristics should be used instead of variable ones.
    • Proper measurements should be used instead of relative terms like "large" and "small".
    • Characteristics available to the user should be prioritized over seasonal or field-specific characteristics.
    • Positive choices should be made, using "is" instead of "is not".
    • Choices should start with the same word, and different pairs should start with different words.
    • Descriptive terms should be preceded by the name of the part to which they apply.

    Types of Taxonomic Keys

    • There are two main types of taxonomic keys: dichotomous and polyclave (multiple access or synoptic).

    Dichotomous Keys

    • Dichotomous keys offer two alternative choices at each branching point.
    • Jean Baptiste-Lamarck first published a dichotomous key in 1778.
    • Contrasting characters are chosen to divide the full set of possible species into smaller groups.
    • Each choice eliminates a number of species, narrowing the range of possible species until a single species is identified.

    Organization of Dichotomous Keys

    • Couplets can be organized numerically or alphabetically, and can be presented together or grouped by relationships.

    Types of Dichotomous Keys

    • There are two types of dichotomous keys: indented keys (or yoked keys) and bracketed keys.
    • Indented keys have equal distances from the left margin, with labelled choices (e.g., 1 and 1' or la and lb).
    • Bracketed keys present both choices side-by-side, with numbered (or lettered) choices and previous couplets for reference.

    Advantages and Disadvantages of Dichotomous Keys

    • Advantages include: similar specimens are grouped together, it's harder to get lost, they are faster to use, and it's easier to retrace steps.
    • Disadvantages include: the key may not include all potential variations in the species, it may rely on features not present in that season, and it may be difficult to use at times.

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    Description

    Explore the different types of taxonomic keys, including their advantages and disadvantages. Understand how keys are constructed and used for identifying unknown species through a series of contrasting statements. Learn about the decision-making process involved in the identification of specimens.

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