LOGY

• Dichotomous key


  A tool that scientists use to help them identify unknown organisms from a pool of known organisms by answering a series of paired yes-or-no questions
• Types of dichotomous keys


  • Branched
  • Numbered
• Branched dichotomous key


  1. Given a question, follow a no or yes path which may lead to an identification or to another question

  2. Continue following the path until you get to an actual identification
• Numbered dichotomous key


  1. Have pairs of statements

  2. If the organism has a certain trait, go to another statement

  3. If the organism does not have that trait, it is actually given an identification
• Steps to make a numbered dichotomous key


  1. Figure out how many organisms you have and subtract 1 to get the number of paired statements needed

  2. Set up the paired statements with 'has' or 'does not have' for each

  3. List the traits of the organisms that can be used to differentiate them

  4. Choose one broad trait to separate the organisms into two groups

  5. Continue choosing traits and filling in the paired statements until all organisms are identified

  6. Check the key and get it peer reviewed
• Good traits to use in a dichotomous key are physical features, objective facts, specific details, and traits that are true most or all of the time
• Bad traits to use in a dichotomous key are location, behavior, classification, and subjective descriptions
• Organisms used to create a dichotomous key


  • Rusty millipede
  • Bumblebee millipede
  • Eastern lubber grasshopper
  • Asian lady beetle
  • Carolina tiger beetle
• The dichotomous key created in the example successfully identified the unknown organisms
• Dichotomous key


  A tool used in classification to identify organisms by asking a series of yes/no questions that divide the organisms into two groups at each step
• How to construct a simple dichotomous key


  1. Pick one feature to focus on that separates the organisms into two groups

  2. Further split each of the two new groups one at a time, focusing on a new feature each time

  3. Continue splitting the groups until each organism is uniquely identified
• Dichotomous keys are an important part of biology classification, which is putting things into groups so we can identify them and know things about them
• The word 'dichotomous' literally means dividing something into two
• Steps in constructing a written dichotomous key


  1. Write yes/no questions at each step

  2. Provide instructions on which question to go to next based on the answer
• Dichotomous key


  • Allows you to identify an unknown organism by answering a series of questions
  • Splits the organisms into two groups at each step based on their features
• Dichotomous keys can be presented as a visual tree diagram or as a written set of questions and instructions
• Annotations can be used on a tree diagram dichotomous key to provide the question details