7C Investigating Populations

Question 1

How to take a random sample

Answer 1

Choose a small area to sample
Sample should be random to avoid bias
Use a random number generator to select coordinates
Repeat the process to decrease the likelihood that the results are due to chance

Question 2

How are quadrats and transects used to measure non motile species

Answer 2

Create a grid
Use a random number generator to select coordinates
Place many quadrats
To find out the percentage cover define area by percentage cover

Question 3

How do you use Mark release recapture to investigate motile species

Answer 3

Capture a sample
Mark the sample in a harmless way
Release them back into their habitat and allow time for them to randomly distribute
Take a second sample
Then use this equation

Total population size = number caught in 1st sample x number caught in 2nd sample/ number marked in 2nd sample

Question 4

What are some assumptions that need to be made when using mark release recapture

Answer 4

Ensure the marking hasn’t affected the organisms chance of survival
Ensure the organism has time to mix back in with the population
There are no changes in population size due to births deaths or migration