Describe how you would perform a random sampling to estimate the size of the population of your species you chose in the Galapagos. Use some actual numbers in your description. Try to base it on real numbers (this may take some research). What underlying assumptions must be made for this technique to be effective? [ /6 marks]
Random sampling is a method used by biologists to estimate the size of a population by collecting data as each organism usually can’t be accounted for separately. By using a random sample each individual within a population has an equal chance of being counted, guaranteeing that the data is not biased. Sampling methods can include:
Quadrats: used within small, non-mobile populations. It is a sampling frame that can either …show more content…
Step #2: Record how many Mockingbirds you grabbed and release them back into the wild.
Step #3: After the population has had time to mix with the samples birds, grab another small amount (25, for example) and record how many of the captured birds were already marked. In this case, 6 out of the 25 birds were marked.
Step #4: Using math, we can get an estimate for the population size:
20 = 6 ----> 20/x is about 25% of the population -> 20*4 would give an estimate of the population x 25 ---> (20/x) = 0.24 ---------------------------> 20*4 = 80 (The actual population is 79)
This is known as the mark-recapture method (sometimes called capture-recapture) which is a sampling technique for estimating population sizes and density, comparing the proportion of marked and unmarked species that are captured within a given areas.
Underlying assumptions that must be made are:
● All birds have an equal chance of being selected
● The bird population will not increase nor decrease during the time from the first sampling to the second sampling
● The proportion of marked to unmarked birds will remain constant during the time from the first sampling to the second
Random sampling is a method used by biologists to estimate the size of a population by collecting data as each organism usually can’t be accounted for separately. By using a random sample each individual within a population has an equal chance of being counted, guaranteeing that the data is not biased. Sampling methods can include:
Quadrats: used within small, non-mobile populations. It is a sampling frame that can either …show more content…
Step #2: Record how many Mockingbirds you grabbed and release them back into the wild.
Step #3: After the population has had time to mix with the samples birds, grab another small amount (25, for example) and record how many of the captured birds were already marked. In this case, 6 out of the 25 birds were marked.
Step #4: Using math, we can get an estimate for the population size:
20 = 6 ----> 20/x is about 25% of the population -> 20*4 would give an estimate of the population x 25 ---> (20/x) = 0.24 ---------------------------> 20*4 = 80 (The actual population is 79)
This is known as the mark-recapture method (sometimes called capture-recapture) which is a sampling technique for estimating population sizes and density, comparing the proportion of marked and unmarked species that are captured within a given areas.
Underlying assumptions that must be made are:
● All birds have an equal chance of being selected
● The bird population will not increase nor decrease during the time from the first sampling to the second sampling
● The proportion of marked to unmarked birds will remain constant during the time from the first sampling to the second