Estimating population sizes

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Created by
skye

Cards (10)

  • one way to estimate the population size of an animal species is capture-recapture
  • the animals are caught, marked then released. it is important that substance used to mark them is not toxic and that it doesn't make the animal more visible to predator. its also important that the animals have time to redistribute evenly within the population. the same method of capture is sued a few days later. the numbers of marked and unmarked animals caught the traps are recorded
  • population size= number in the first sample * number in the second sample/number in second sample previously marked
  • when using capture- recapture data, you have to make assumptions including:
    • there is no deaths, or movement of animals in other habitats
    • the sampling methods used each time are identical
    • the marking has not affected the survival rate of the animals
    • the marking hasn't washed off
    • the animals have redistributed evenly
  • Dichotomous keys use questions to which there are only two answers
  • they can be presented as a table of questions, or as a branching tree of questions
  • identification keys are useful when you are carrying out sampling as they help you to correctly identify the organisms that you find
  • Quadrats are placed on the ground to look at the plants or slow-moving animals within them.
  • when looking at plants in a quadrat , the following sampling can be used:
    • number of individual species- the total number of individuals of one species is recorded
    • species richness- the number of different plant or animal species is recorded but no the number of individuals within a species
    • percentage cover- the percentage of the quadrat area that is coved by one species
  • random sampling using quadrats involves the placing of quadrats at random coordinates. regardless of weather you are investigating the number of individual species, the diversity of species of the percentage cover in different areas, you would use random sampling. this removes at bias and ensures that the data is more representative