Estimating population sizes

Question	Answer
POPULATION	all the organisms of one species in a habitat
COMMUNITY	populations of different species in a habitat
Estimating population sizes from scaling up from small sample area	a quadrat is a square frame enclosing a known area. You can study the small area within a quadrat and scale up your findings to make estimates for larger areas: 1. count all the organisms in a 1m2 quadrat 2. multiply the no. of organisms by the total area (in m2) of the habitat
Capture - recapture	1. capture a small sample of the pop. and mark the animals in a harmless way 2. release them back in to the environment 3. recapture another sample of this population. Count how many of this sample are marked. 4. estimate pop. size using: no.in 1st sample x no. in 2nd sample -------------------------------- no. in 2nd sample previously marked
Important points about scaling up from a sample size and capture-recapture	1) the sample size affects the accuracy of the estimate - the bigger your sample, the more accurate your estimate of the total pop. is likely to be. 2) when you're using capture-recapture data you have to assume: there have been no changes in the pop. size due to deaths, immigration or emigration; the sampling methods for the capture and recapture were identical; the marking hasn't affected the individuals' chances of survival

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	Created by eibhlinjones200 almost 11 years ago