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Using Dichotomous Keys

Using Dichotomous Keys. Keeping track of species. Taxonomy: describing and naming an organism >1 million species named, up to 15 million more Taxonomy is not new; cultures have been naming plants and animals around them for 1000s of years It’s practical to have names. Binomial Nomenclature.

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Using Dichotomous Keys

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  1. Using Dichotomous Keys

  2. Keeping track of species Taxonomy: describing and naming an organism >1 million species named, up to 15 million more Taxonomy is not new; cultures have been naming plants and animals around them for 1000s of years It’s practical to have names

  3. Binomial Nomenclature Standard system for naming things Linnaeus described and named > 6,000 animals and >4,000 plants using Latin Scientific name does not replace, but instead further defines common name

  4. Early naming of species 1st word was a noun: Genus 2nd word was an adjective: Specific epithet Genus + specific epithet = scientific name of a species

  5. Taxonomic goals Place organisms into logical categories • system must be capable of being used for information retrieval, so anyone can properly identify any organism Place organisms into categories that show ancestor-descendant relationships

  6. Taxonomic hierarchy Kingdom (Animalia) Phylum (Chordata) Class (Mammalia) Order (Rodentia) Family (Sciuridae) Genus (Sciurus) Specific epithet (species) (carolinensis) Scientific name: Sciurus carolinensis

  7. What is a dichotomous key? • Key  tool for identification of biological specimens • Dichotomous  pairs of mutually exclusive statements • Couplet  each pair of statements • Decision tree • Important considerations • Geologic scope • Taxonomic scope • Terminology

  8. Keying out individuals: hints • Learn the terminology of the group • Learn where to look for the descriptive characteristic • generic labeled pictures help! • Know WHERE the samples were collected

  9. Keying out individuals: hints • Know the habitat type • Have measuring instruments in hand • Once you can identify key features of groups, you can skip over the early parts of the key, and jump straight to Family, for instance

  10. Plant Anatomy

  11. Leaf Anatomy

  12. Types of Leaves

  13. Leaf Arrangement

  14. Shape of Leaf Blade

  15. Leaf Venation

  16. Shape of Leaf Margin

  17. Shape of Leaf Apex

  18. Shape of Leaf Base

  19. Example • Leaves compound or simple? • Leaves needle-shaped or broad and flat? • Leaves opposite or alternate? • Shape of the leaf and veins? ACER

  20. Dichotomous Key Assignment

  21. Use key to insect orders to identify this specimen to order. Unknown 3

  22. Hint: This insect has external lateral gills on its abdomen. Use key to insect orders to identify this specimen to order.

  23. Use key to insect orders to identify this specimen to order.

  24. Unknown 4: Aquatic larva Hint: This insect has normal biting jaws. Use key to insect orders to identify this specimen to order.

  25. Use key to insect orders to identify this specimen to order. Unknown 5

  26. Woodpeckers Make a key to differentiate these woodpeckers (also see next slide).

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