Investigating Populations - Sampling Flashcards
1
Q
Why do we use sampling?
A
- Used to measure biodiversity of a habitat or the abundance of species.
- It is impossible to count all of the organisms of a species
- Sample needs to be representative of the whole habitat/ecosystem
- use sample data to estimate the total number of individuals in the habitat/ecosystem
2
Q
What about the size of the sample do we need to follow?
A
- a large sample size
- lots of repeats
3
Q
what does a large sample size allow us to do?
A
- calculate a mean
- use a statistical test
4
Q
What are the general rules about sampling?
A
- large sample size
- sample a different:
- times of the day/year
- weather conditions
- Standardised sampling methods
avoid capturing same individuals twice
5
Q
Why do we use random sampling?
A
- To avoid bias
6
Q
How do we avoid bias in random sampling?
A
- Divide sampling area into a grid
- use a random number generator to pick co-ordinates
7
Q
How would we do sampling in plants?
A
- Quadrats
- NOT TRANSECTS
8
Q
How would we do sampling in mobile animals?
A
- Traps
9
Q
How would we do sampling in Flying insects?
A
- Sweep nets
10
Q
What are the types of non-sampling methods?
A
- systematic sampling
- opportunistic sampling
- stratified sampling
11
Q
What is systematic sampling?
A
- samples are taken at fixed intervals e.g. transects
- Measures a change in the environment
- e.g. change in moving away from high tides
12
Q
What is opportunistic sampling?
A
- Sample sites are chosen by investigator
- samples will be placed
- easy and fast to do
13
Q
what is stratified sampling?
A
- survey area is divided into groups
- each area is surveyed separately
- in proportion to its coverage of total area
- more representative than random sampling
14
Q
What is random sampling?
A
Random sampling is used to select a sample that is unbiased.
