Distribution of Organisms

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How to use Quadrat to study distribution

  • Place a 1m squared quadrat onto the ground at a random point wthin the first sample area. Divide the area into a grid and use a random number generator to pick the coordinates
  • Count all the organisms within the quadrat.
  • repeat steps above as many times as you can.
  • Work out the mean number of organisms within the first sampl area
  • Repeat steps 1-4 in the second sample area
  • Finally compare the two means

 

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How to use a transect

  • Mark out a line in the area you want to study using a tape measure
  • Collect data along the line
  • Do this by just counting all the organisms youre interested in that touch the line
  • Or collect data by using quadrats. Theses can be placed next to each other along th line or at intervasl for exapmle every 2m
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Reliability & Validility

Make sure results are repeatable and reproducible

To make results more reliable:

  • Take a large sample size. Bigger samples are more representative of the whole population
  • use random samples randomly put down ormark out your quadrat/transect If all samles are in one spot and everywhere is different the results won't be reproducible

Validity

Must be reliabe and anser original question- need to control all the vriables.

Contol variables => know whether there is a difference in distribuion is caused by an environmental factor or not

Dont control variables=> wont know if a correlation has bee found because of chance the environmental factor  or because of a different variable- study will not give valid data

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