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BIOL 4240 Field Ecology

BIOL 4240 Field Ecology. Data, data everywhere. “Modern science proceeds by conjecture and refutation, by hypothesis and test, by ideas and data, and it also proceeds by obtaining good descriptions of ecological events”. Krebs 1999 p.1. Data, data everywhere. What data should be collected?

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BIOL 4240 Field Ecology

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  1. BIOL 4240Field Ecology

  2. Data, data everywhere “Modern science proceeds by conjecture and refutation, by hypothesis and test, by ideas and data, and it also proceeds by obtaining good descriptions of ecological events”. Krebs 1999 p.1

  3. Data, data everywhere • What data should be collected? • What is useful and useless?

  4. Data, data everywhere • Krebs rules… • Not everything that CAN be measured SHOULD be measured • Find a problem and state your objectives clearly • Collect data that will achieve your objectives and make a statistician happy. • Some ecological questions are impossible to answer at the present time

  5. http://www.deepseaworld.com/attractions/lake_malawi.asp?css=1http://www.deepseaworld.com/attractions/lake_malawi.asp?css=1 http://antwrp.gsfc.nasa.gov/apod/ap971026.html http://www.lazyjames.co.uk/hotrock/malawi.html http://www.vagabonding.com/gallery_app/view_photo.php?set_albumName=malawi&id=DSC01998_lake_malawi_fish http://www.mdafederal.com/geocover/geocoverortho/gcorthoregional/africa_mosaic.jpg/view http://en.wikipedia.org/wiki/Lake_Malawi • Hierarchical review… • Biosphere • Region • Landscape • Ecosystem • Community • Population • Individual (organism)

  6. Many ecological questions involve populations… ¿What are the 3 populations that exist?

  7. Controlled vs. uncontrolled events… ¿What is the difference between spatial and temporal scales/studies?

  8. Intervention analysis… % Nest success Year

  9. Other scales of measurement… ¿What is the difference between … *Nominal *Ranking *Interval and ratio scales?

  10. Continuous OR Discrete… ¿What is the difference?

  11. Continuous-ly worrying about precision and accuracy… ¿What is the difference? ¿How does implied precision vary? SVL in mm for Idaho Giant Salamanders 73 73.4 73.47

  12. Identify the following types of data • Month when hibernation begins • Mass of salamanders • Number of salamanders > 50mm svl • Temperature of stream water

  13. ¿How many significant figures should you measure? The rule of 300 • Sokal and Rohlf’s method • Determine range of your data • Range/30 AND Range/300 • OR • Barford’s method

  14. More of Kreb’s rules • With continuous data, save time and money by deciding on the number of significant figures needed in the data BEFORE you start an experiment When conducting calculations… your answer is only as good as your weakest link. ¿What is meant by this?

  15. To Describe or to Infer that is the question… • ¿What are the limits of inference? • At least 3 problems related to inference… • Statistical populations • Confounding/hidden variables • Bias • Δ Read a sample abstract and then determine the limit of inference…

  16. More of Kreb’s rules • Never report an ecological estimate without some measure of its possible error

  17. ¿ Black and white… or shades of gray? The value of a p value… ¡Be sure you know the difference between statistical and biological significance!

  18. More of Kreb’s rules • Be skeptical about the results of statistical tests of significance. • Never confuse statistical and biological significance Evaluate the statement “Null hypotheses are irrelevant to ecologists”

  19. More of Kreb’s rules • Make a data form and enter your data into a spreadsheet/database • Garbage in, garbage out ¿What can you do to minimize “garbage”?

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