1. Size of quadrat // 2.Number of quadrats // 3. Position of quadrat (Overall more quadrat's = More reliable results)
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Random sampling method
1. Avoids bias - Lay out two long measuring tapes at right angles, along to sides of the study area. Obtain a series of coordinates using random no. generated by a computer. Place the quadrat at the intersection of the pair of coordinates & record
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To obtain reliable sample results... (3)
1. Large sample size - more representative of community as a whole 2. Calculate a mean of samples 3. Many quadrats used
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Advantage and disadvantage of frequency measurements
Adv . Gives a brief idea of distribution and what species are present. Disad. Doesn't provide info on density or detailed distribution
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Advantage and disadvantage of percentage cover
Adv. Useful when the species is abundant and difficult to count. Also quicker that counting individual plants. Disad. Less helpful when organisms occur in overlapping layers
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Mark - release - recapture method (Investigates mobile populations)
A known number of individuals are caught and marked in some way. They are them released back into community and given sufficient time to distribute themselves evenly among population. After a given no. of individuals r collected randomly. Marked reco
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Calculation to estimate population size
no. in sample 1 X no. in sample 2 / no. marked recaptured.
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What will the effect on the final population size be, if the mark made individuals more liable to preditation
The population will appear larger. Because there will be proportionally fewer marked individuals in the 2nd sample
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Other cards in this set
Card 2
Front
What is a Community?
Back
All the populations of different species living and interacting in a particular place at the same time.
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