Sampling Flashcards
(22 cards)
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
Advantages of systematic sampling
-when habitat show clear gradient in environmental factor
Disadvantages of systematic sampling
-only species on line in belt will be recorded
-other species could be missed.
How does a beating tray work
Large white sheet placed on ground and held below tree. Tree shaken to dislodge animals
How does a pooter work
Use it to suck small animals into glass or plastic tube
How does a sweep net work
Large nets to catch flying insects and those that live in long grass
How does a pond net work
Stronger nets that can lift volumes of water from ponds or rivers. Water drains through leaving plants/vegetation
How do pitfall traps work
Cans/jars buried in ground to collect ground dwelling insects that are often nocturnal.
Paper/cardboard to provide shelter
Stone or lid to keep out rain
