Sampling Flashcards
What is sampling
Taking measurements of limited number of individual organisms present in area
What must sampling be representative of
1-size of area or length if transect
2-incorporation of repeat measurements
3-accounting for different times of the year
What are quadrants used to assess
1.species frequency
2. Species density
3.percentage cover
What is random sampling
Via number of ways (number generator ect) to choose coordinates to sample from .
Removes bias as all locations have equal chance of being chosen
What are the types of non random sampling
1-Opportunistic
2-stratified
3-systematic
Describe opportunistic sampling
-weakest sampling
-make sampling decisions based on prior knowledge or during process of collecting data
-could deliberately sample area know contains particular species
Describe stratified sampling
Samples divided into areas which appear
Sampling each area differently
Describe systematic sampling
-samples taken at fixed intervals across habitat
Types of systematic sampling
Belt transect-info on quadrants along transect line
Interrupted belt transect- record quadrats set intervals along transect line
Line transect- record species touching transect line
What is an advantage of random sampling
Ensure no bias
Disadvantages of random sampling
-not cover all areas equally
- species with low presence may be missed
-underestimate of biodiversity
Advantages of opportunistic sampling
-quicker + easier than random
Disadvantages of opportunistic sampling
-biased data
-colourful or large species may make researchers focus on them
-overestimate species
Advantages of stratified sampling
-ensure all different areas of habitat sampled
-no under representation
Disadvantages of stratified sampling
-over representation of some areas in sample
