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Biotic Factors

Biotic Factors. Abundance of Organisms. Learning objectives. You should be able to: Identify the different methods for catching moving animals. Describe and evaluate the Lincoln Index as a way of measuring abundance. Pitfall Traps. O rganisms? Advantages / disadvantages? Bias?.

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Biotic Factors

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  1. Biotic Factors Abundance of Organisms

  2. Learning objectives • You should be able to: • Identify the different methods for catching moving animals. • Describe and evaluate the Lincoln Index as a way of measuring abundance

  3. Pitfall Traps • Organisms? • Advantages / disadvantages? • Bias?

  4. Small Mammal Traps The Longworth live trap • Organisms? • Advantages / disadvantages? • Bias?

  5. Light Traps • Organisms? • Advantages / disadvantages? • Bias?

  6. Tullgren Funnel

  7. Lincoln Index • Capture, mark, release and recapture. • Estimates the population size of animals that move / don’t appear during the day. • At least 10% needs to be recaptured. • Based on that, what assumptions would have to be made?

  8. Lincoln Index • Assumptions include: • Mixing is complete • Marks do not disappear • Marks are not harmful nor increase predation • It is equally easy to catch every individual • There are no immigration, emigration, births or deaths between sampling

  9. Formula • n1 = number of animals first marked and released • n2 = number of animals captured in the second sample • m = number of marked animals in the second sample • N = total population

  10. Have a go at calculating some populations…

  11. Quick Quiz • Name 2 different types of animal trap and the type of animals that they capture. • This is the formula for the Lincoln Index, what do the different letters represent? • What are the advantages and disadvantages of using the Lincoln Index to calculate abundance?

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