# 1.2 Investigating Populations

what does investigating populations of organisms involve
Looking at the abundance and distribution of species in a particular area.
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Name two sampling techniques
1) Random sampling (using frame quadrats or point quadrats) 2) Systematic sampling along transects
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What three factors should you consider when using quadrats?
1) the size of a quadrat to use 2) the number of sample quadrats to record within the study area 3) the position of each quadrat with in the study area
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Why is the size of the quadrat you use important?
It depends on the size of the plants or animal being counted and ow they are distrubuted with in the area. Larger species = larger quadrat.
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Why is the number of sampling quadrats to record with important?
Because the larger number of quadrats used the more reliable the results will be.
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Why is the postion of each quadrat with in the study area important?
to produce statistically significant results as a technique know as random sampling must be used.
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why is random sampling important?
To reduce bias and produce statistically significant results.
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How would you do random sampling?
you could divide a field into a grid and using a random number generator select coordinates.
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Why is doing repeats important?
So you get a more reliable estimate for the whole area.
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What is frequency in terms of measuring the sizes of species?
the likelihood of a particular species occuring in a quadrat.
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What is percentage cover in terms of measuring the sizes of species?
the estimate of the area within a quadrat that a particular plant species covers. It is useful when the species is so abundant its difficult to count.
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What is a line transect?
A string or tape that stretches across the ground in a straight line. Any organism over which the line passes is recorded.
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What technique could be used when measuring the abundance of more mobile organisms?
Mark-release-recapture.
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Explain the mark-release-recapture technique
1) capture a sample using a appropriate technique and count them. 2)mark them in a harmless way ( eg paint or remvoing fur) 3) release back into habitat 4)wait, then take 2nd sample from same pop. 5)count how many of 2nd sample is marked.
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What are the 4 assumptions in which the accuracy of this method relies on ?
1) marked sample has had enough free time and oppotunity to mix back with pop. 2)marking hasnt afffected chance of survival 3) changes to pop. size like births/death/migration are small during period of study. 4) lable is not lost or rubbed off
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## Other cards in this set

### Card 2

#### Front

Name two sampling techniques

#### Back

1) Random sampling (using frame quadrats or point quadrats) 2) Systematic sampling along transects

### Card 3

#### Front

What three factors should you consider when using quadrats?

### Card 4

#### Front

Why is the size of the quadrat you use important?

### Card 5

#### Front

Why is the number of sampling quadrats to record with important?