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Dichotomous Keys

Dichotomous Keys. Introduction. A dichotomous key is a tool that allows the user to determine the identity of organisms in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish.

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Dichotomous Keys

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  1. Dichotomous Keys

  2. Introduction • A dichotomous key is a tool that allows the user to determine the identity of organisms in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish. • "Dichotomous" means "divided into two parts". Therefore, dichotomous keys always give two choices in each step.

  3. 1. a. wings covered by an exoskeleton – go to step 2 b. wings freely observed – Go to step 3 2. a. body has a round shape ……….ladybug a red beetle with black spots b. body has an elongated shape ……….grasshopper a green insect that hops 3. a. wings point out from the side of the body ……….dragonfly an insect that is 10- 15 cm long and lives in marshes b. wings point to the posterior of the body ……….housefly a flying insect with red eyes and an annoying buzz

  4. Hints: Use constant characteristics rather than variable ones. (Flowers change with the seasons) Use measurements in centimeters or meters rather than terms like "large" and "small". If possible, start both choices of a pair with the same word. NOTE: Finish the dichotomous key with a description of the organism

  5. Dichotomous Key for conifers

  6. This key is not a dichotomous key

  7. Make a dichotomous key to identify 6 macroinvertebrates Stone fly larvae Leech Dobson fly larvae Riffle beetle Mayfly larvae Crane fly larvae

  8. Broad leaved versus coniferous trees

  9. Conifers have needles or scales

  10. Broad leaved examples

  11. Branching

  12. Simple and Compound leaves

  13. Simple and compound leaves

  14. Simple leaves

  15. Leaf Shapes

  16. Lobed leaves

  17. Palmately compound leaf

  18. Pinnately Compound Leaf

  19. Bipinnately Compound Leaf

  20. State if the leaf is simple, compound, needles or scales

  21. Leaf shapes

  22. Leaf margins

  23. Evaluate this key

  24. Evaluation of the key • The characteristics are not constant. Flowers bloom and seed pods are visible at different seasons • The trees are not described at the end of the key • Large and small are used instead of real measurements • Yes and no questions are used. • Therefore, this dichotomous key is not as good as it should be!

  25. Dichotomous Key Lab notes: • In pairs or alone, observe eight trees and leaves. • Collect only small samples of leaves so that you do not damage the tree. • Label your samples with your names and the type of tree. Store it in a safe place. • Measure a range of leaf sizes with a ruler. • Estimate the height of the tree. • Make a dichotomous key.

  26. Data collection, processing and presentation

  27. Personal Skills: Team work, attention to safety and ethics

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