Chapter 15: Research Methods Flashcards
Accuracy
A measure of how close the recorded result is to the real value
Precision
The intervals between possible recorded results
E.g. millimetres on a ruler are more precise measurements than centimetres
Representative sample
A sub sample that accurately reflects the complete data set
Reliable method
Provides constant and accurate results
Anomalous Results
A result that differs from other results that is was expected to be similar to
Repeating the study means you can find out if it was a ‘rea’ result or caused by other variables
Valid study
Produces precise, accurate, reliable results that conclusions can be based on
General principles of scientific investigations
Identifying a topic of interest
Find out what has already been learnt
Formulate a hypothesis/null
Design/carry out an experiment to test the hypothesis
Design investigation
Analyse results and draw conclusions
Random sampling
Used if the study are is a regular shape
A grid can be laid out
The coordinates of the sampling site can be be selected using random numbers
Random sampling at a study area that is an irregular shape
All possible sampling sites can be numbered and selected with a random number generator
Systematic sampling
Involves samples taken using a chosen interval distance or spacing
The choice isnt made based on observable differences in the study area
Sample timing
If a factor being measured changes with time then it will be necessary to sample on different occasions to identify trends in changing values
Number of samples
A single sample may not be representative, collecting multiple will help eliminate the effect of variability
It is also easier to assess the degree of statistical significance of the results with larger numbers of samples
Why are techniques standardised?
To allow the comparison of results collected at different times, locations or researchers
Why is ecological monitoring important for wildlife conservation or Grammies?
To find out which species are present, monitor habitat conditions, monitor features of populations that change e.g: population size, growth rates, movements
What is a quadrat?
A study area that is usually a square
Populations within it can be studied
Results from a number of quadrants can be used to estimate the situation of an area
How is the quadrat size selected?
Depends on the habitat and groups of species being studied
E.g. might be 10cm x 10cm for lichens, but 100m x 100m for trees in a forest
3 types of quadrats
Open frame quadrats
Grid quadrats
Point quadrats
Limitations of Quadrats
Subjective judgement may be involved- estimating percentage cover
The frame may flatten of move plants
Method for using a pond net
- they are swept through water to capture invertebrates, amphibians and fish
- to standardise, there can be a particular length of sweep or number
Limitations of a pond net
Mobile species may escape
What is the purpose of kick sampling?
To collect invertebrates that live on riverbeds
Method for Kick sampling
Hold a net with the straight edge on the river bed and its face open to the current
Use boot to disturb the riverbed in front of the net- this will dislodge invertebrate
Standardising kick sampling
The number and length of kicks controlled
Limitations of kick sampling
Difficult to standardise
Some organisms may not be dislodged
Some organisms can swim and avoid the net
Water flow rate is variable and that can affect the capture rate
Fragile organism might be destroyed
What is a more standardised technique than kick sampling ?
Surber samplers
Method of using surber samplers
Fixed area of the riverbed is sampled within a box-like frame
Riverbed disturbed with a trowel and stones manually inspected
Netting at the sides reduces the number of organisms that escape
Limitations of surber samplers
Only be used where water flows fast enough to move organisms into the net
Small sized sample which makes it difficult to set on rough substrates in deep water
Can result in the loss of large organisms
Purpose of plankton nets
To catch floating planktonic organisms
Some can be used to give quantative estimates of populations
Method for using plankton net
A fine mesh is pulled through the water, it can be towed or fixed where there is a current
Limitations of plankton nets
Nets with coarse mesh dont catch smaller organisms
Nets with fine ese can be clogged with phytoplankton which prevents the flow of water
Method for sweep nets
Used to sample invertebrates in ground vegetation
Sweep net through vegetation to catch dislodged organisms
Limitations of sweep nets
Mobile species like flying insects might escape
What are aerial insect nets?
Lightweight nets used to capture flying insects like butterflies
Limitations of aerial insect nets
To do it successfully depends on agility of species and researcher
Purpose of pitfall traps
Sample populations of mobile animals on ground surface
Method for pitfall traps
Container in the ground, with a cover to exclude predators and prevent flooding
Trap is checked after a standardised period
Limitations of pitfall traps
Only mobile species that live on ground are caught
Some trapped organisms may kill others that have been caught
Some species can avoid them or escape
Method for beating trays
A tray is placed under vegetation which is beaten several times to dislodge invertebrates so they can be identified and counted
Limitations of beating trays
Difficult to standardise
Some species aren’t dislodged
Thicker branches will shake less
Some species will fly away
Higher branches cant be reached
What are light traps used for?
To collect night-flying insects that are attracted by bright lights
Methods for light traps
Flying insects that are attracted to light fall into a container which is checked the following morning. Species are identified and counted
Limitations of light traps
Moths only fly in their adult phase, but activity depends on weather- so species may not be in the trap even if they are in that habitat
The type of WL of light can affect the attractiveness t insects
Purpose of the Tullgren Funnel
To sample mobile invertebrates in leaf litter or soil
Method for the Tullgren funnel
A sample of leaf litter/soil is put on mesh beneath light
Light/heat repel some mobile invertebrate so they move down,pass through mesh and fall into container
Invertebrates are collected and identified and counted
Limitations of the Tullgren funnel
Only species repelled by heat/light are collected
Some organisms may die because of the heat
Some organisms are too large to pass through the mesh
Purpose of suction samplers
Capture airborne insects or invertebrates that are dislodged from vegetation
Limitations of suction samplers
Some invertebrates can fly away
Some insects might not be dislodged
2 ways earthworms can be removed from the soil to be monitored
Soil flooding
Soil pit extraction
