PACK 13: ECOLOGICAL TECHNIQUES

Question 1

why is random sampling used?

Answer 1

to avoid bias, be representative of data as a whole, and produce statistically significant results

Question 2

why does the sample size need to be large

Answer 2

to be representative of the population, to allow statistical tests to be carries out on data

Question 3

how would you use random sampling to calcite the population of daises in a field using random sampling?

Answer 3

use tape measures at a right angle to each other to mimic a grid, use a random number generator to generate random coordinates and place the left corner of a quadrat at the co-ordinates repeat this until you have a large sample size (of at least 20 quadrats). work out the mean number of daises per quadrat and multiply by the number of quadrats in the area.

Question 4

describe how you would use a belt transect to calculate the distribution of a plant across different environments, e.g. from the shade of a tree into the light in the middle of a field

Answer 4

place quadrats at regular intervals along the line and record the abundance of the plantin each quadrat

Question 5

how would you make sure the belt transect data was as accurate as possible, and how could you use the data in calculation

Answer 5

more than one quadrat at each point to increase sample size (thus representation), the measurements should be regular in order to establish a pattern, then the data should be used to calculate percentage cover, specifies frequency, and species density

Question 6

describe the process of mark release recapture

Answer 6

a large sample of the organism is collected, they are then marked, and released back into the population allowing time to mix. the marking bust not harm the animal in any way, or be visible to any predators so doesn’t hinder the chances of survival. then capture a large sample once again and count the total nu,ber and the total number that are marked.

Question 7

how to calculate an estimate of the population size based of capture recapture

Answer 7

(number of originally caught x total number caught the second time) / the number of recaptures (marked individuals on the second recapturing)

Question 8

what assumptions does the mark-release-recapture method make

Answer 8

there is no immigration or emigration
there are no births or deaths
marking wont affect the likelihood of being recaptured or preyed upon
marked individuals have had enough time to fully reintegrate back into the population