Distribution of Organisms and Sampling Tecniques

Using Quadrats to study the distribution of organi

Place a quadrat on the ground at a random point within the first sample area- put measuring tapes along the 2 sides and choose random coordinates using a random number generator
Count all the organisms within the quadrat
Repeat these steps as many times as you can in one area
Work out the mean number of organisms per quadrat within the first sample area
Repeat the steps in the second sample area
Compare the 2 means
Because the coordinates are chosen at random, you will make sure that there is no bias by the investigator
Ensures the results are valid, as they are reliable (repeatable+ reproducible) + answer the original question

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Choose the start and the end position of the transect, which should be placed across the steam
Determine the direction+ length of the transect
Mark out a line in the sample area using a tape measure
Place quadrats along the line either next to each other or at intervals
Count the number of organisms in each quadrat
Perform parallel transects to ensure the results are reliable- repeatable+ reproducible, as the sample size increases- more representitive of the whole population
Calculate the mean of the number of organisms in the quadrats parallel to each other
Compare the results of sample areas

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Reliability- making sure the results are repeatable and reproducible (other people using different equipment should get the same results)
Large sample size- representative of the whole population
Random samples- not biased- results shouldn't be taken in one spot
Validity- reliable and answer the original question
Control the variables
Accuracy- results that are close to the true answer
Precision- results that are really close to the mean

Resolution- the smallest change a measurement instrument can detect
Zero error- if a systematic error is caused by using equipment that isn't calibrated properly
Systematic error- the same error is made every time

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