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2.3 Measuring Biotic Components

Learn how to estimate animal populations using the Lincoln Index and plant populations via Quadrat Estimation. Discover the principles, assumptions, and methods for calculating population density and diversity.

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2.3 Measuring Biotic Components

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  1. 2.3 Measuring Biotic Components

  2. Estimating Populations of Animals • Lincoln index (capture-mark-release-recapture) n1 x n2 N = m • N = Total number of population • n1 = Number of animals first (mark all of them) • n2= Number of animals captured in second sample • m= Number of marked animals in second sample Ex. 40 mice were caught, marked (tail tattoo) and released. Later, 10 mice were recaptured, 4 of which had tattoo marks.

  3. Lincoln Index

  4. Lincoln Index Assumptions • The marked animals are not affected (neither in behavior nor life expectancy). • The marked animals are completely mixed in the population. • The probability of capturing a marked animal is the same as that of capturing any member of the population. • Sampling time intervals must be small in relation to the total time of experiment of organisms life span. • The population is closed (no immigration and emigration) • No births or deaths in the period between sampling.

  5. Estimating Populations of Plants • Quadrat Estimation • Population Density- The number of plants within the given area of the quadrat (m2) • Percentage Coverage- How much of the area of a quadrat is covered by plants? • Frequency- How often does a plant occur in each quadrat? • Acacia senegalensis was present in 47 of 92 quadrats, for a frequency of 51%

  6. Calculate Population Density What is the population density of species x ? What is the population density of species w? What is the population density of species Z? Quadrat 1= 0.5m2

  7. Calculate Percentage Coverage What is the percentage of plant coverage in this quadrat? Quadrat 1= 0.5m2

  8. Percentage Frequency Quadrat 1 What is the frequency of species X? What about species V? Quadrat 2 Quadrat 3

  9. Other Methods of Estimation(Plants) • Sampling – Take a sample from one area and assume the organisms are evenly spread out through the area. • Biomass (dry weight) of living tissue • We use dry weight because water is non-living and needs to be excluded • Ex. 10 ferns were found in a 100m2 area. How many ferns would be in 1000m2 field in the same ecosystem?

  10. What is diversity? • Diversity is the variety of life • Diversity is a combination of two components • Abundance: The number individuals of each species present in a sample • Richness: The total number of different species in a sample

  11. How Can We Know Diversity? Use the Simpsons diversity index below

  12. Example Data Calculations

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