1.6.2

Dichotomous Keys

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Dichotomous Keys

Dichotomous keys help us classify organisms based on a series of observations of easily identifiable characteristics.

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Making dichotomous keys

  • Dichotomous keys are used to help classify organisms in an easy and effective way.
  • Observations about the organisms are made about easily identifiable characteristics.
  • These observations are made into questions.
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The basis of dichotomous keys

  • Di means two, so each questions has two parts (yes or no).
  • Dichotomous keys can be a series of questions or a branching tree question set.
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Examples of organisms in a dichotomous key

  • Firstly, imagine the various organisms you may find on the seashore.
  • Examples include:
    • Bladder wrack Seaweed
    • Herring Gull
    • Shore Crab
    • Sea Lettuce seaweed
    • Anemone
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An example dichotomous key (1)

  • (1) Does it have wings?
    • Yes – Herring Gull
    • No – Question 2
  • (2) Is it stuck to a rock?
    • Yes- Anemone
    • No – Question 3
  • (3) Is it bright green?
    • Yes – Sea lettuce seaweed
    • No – Question 4
  • (4) Does it have legs?
    • Yes – Shore crab
  • No – Bladder wrack seaweed
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An example dichotomous key (1)

  • (3) Is it bright green?
    • Yes – Sea lettuce seaweed
    • No – Question 4
  • (4) Does it have legs?
    • Yes – Shore crab
  • No – Bladder wrack seaweed

Jump to other topics

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.5Plants & Photosynthesis

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.2Chemical Reactions

2.3Atoms, Elements, Compounds

2.4The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.7Energetics

2.8Properties of Materials

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.5Matter

3.6Space Physics

4Thinking Scientifically

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