Random Sampling
- Measuring the different levels of biodiversity within an ecosystem can be a time-consuming task
- Finding out which species live in an ecosystem and the size of the populations requires the identification and cataloging of all organisms present to build a species list
- This is possible for areas that are very small or where the species are very large, like trees
- However, for larger and more complex ecosystems like rainforests, it is simply impossible to find, identify and count every organism that exists there
- When this is the case different samples of the area can be taken and used to make estimates of the total species numbers in the area
Sampling
- Sampling is a method of investigating the abundance and distribution of species and populations
- There are two different types of sampling:
- Random
- Systematic
- In random sampling the positions of the sampling points are completely random or due to chance
- This method is beneficial because it means there will be no bias on the part of the person that is carrying out the sampling that may affect the results
- In systematic sampling the positions of the sampling points are chosen by the person carrying out the sampling
- There is a possibility that the person choosing could show bias towards or against certain areas
- Individuals may deliberately place the quadrats in areas with the fewest species as these will be easier and quicker to count
- This is unrepresentative of the whole area
- When a sampling area is reasonably uniform or has no clear pattern to the way the species are distributed then random sampling is the best choice
Random v Systematic Sampling Diagram
Random sampling differs from systematic sampling when choosing sample sites on an island