19.5 investigating populations Flashcards
what are the 2 ways to sample?
- random
2. systematic (transect)
how do you sample at random?
- 2 numbered axis can be laid out over the sample area
2. generate random numbers to provide co-ordinates for areas to study
how do you sample systematically?
samples are taken at regular intervals along a transect
what are the 2 types of quadrat?
- frame
2. point
what are the things to consider when using a quadrat?
- size of quadrat
- number of samples being taken in the area
- position of each quadrat
what is the mean density equation?
total number of individuals counted/ number of quadrat X area of quadrat
why are the numbers generated in a random sampling done at random?
remove bias
why are more samples better than taking few sample?
more reliable
describe the process of mark- release- recapture
- set of animals are caught and then marked
- released back into the community
- after a specified length of time, the community is revisited ad the same number or individuals is caught again
- number of marked individuals is counted
estimated population size equation
total number of individuals in 1st sample X total number of individuals in 2nd sample/ number of marked individuals recaptured
assumptions in the mark- release- recapture method
- no births and deaths
- mark is not lost or rubbed off
- mark is not toxic nor does it make the individuals more conspicuous to predators
- define boundary so no immigration or emigration
- marked individual released distribute themselves evenly and have sufficient time to do so
- proportion marked to unmarked in the 2nd sample is the same as the proportion of marked and unmarked individuals in the population as a whole
in which sampling technique do you use quadrats?
random sampling
