# Estimating Population Sizes

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What is a POPULATION?
A population is all the organisms of one species in a habitat.
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What is a COMMUNITY?
A community is the populations of different species in a habitat.
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How would you estimate population sizes by scaling up from a small sample area?
You would use a quadrat and count all organisms in the 1mx1m area. Then, multiply the number of organisms by the total area. Pretty self explanatory.
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How would you measure population sizes using the CAPTURE-RECAPTURE method?
You would capture a small sample and mark the organisms. Then, you would release these and take another sample. In the second sample, you would count the number of organisms that were previously marked, and use the following equation.
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What equation is used in the CAPTURE-RECAPTURE method?
Population size= (number in the first sample x number in the second sample) ÷ the number in the second sample that were previously marked.
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How does sample size affect the accuracy of the estimate?
The bigger your sample, the more accurate your estimate of the total population is likely to be.
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What assumptions should you make when using the capture-recapture method?
That there were no changes in population size due to death, immigration or emigration, that the sampling methods for the capture-recapture were identical, and that the marking didn't affect the organisms chances of survival (e.g. making them visible)
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## Other cards in this set

### Card 2

#### Front

What is a COMMUNITY?

#### Back

A community is the populations of different species in a habitat.

### Card 3

#### Front

How would you estimate population sizes by scaling up from a small sample area?

### Card 4

#### Front

How would you measure population sizes using the CAPTURE-RECAPTURE method?

### Card 5

#### Front

What equation is used in the CAPTURE-RECAPTURE method?