# Distribution of Organisms and Sampling Tecniques

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• Created by: Lina
• Created on: 09-04-14 13:26

## 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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## Working out population size

• Work out the mean number of organisms per m2
• Multiply the mean number of organisms per m2
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## Using Transects to study the distribution of organ

• 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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## Why would it be very consuming to just count every

• The organisms may move
• There may be too many organisms to count
• Time- consuming
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## How to improve an experiment

• 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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