Research Methods Flashcards
What is a hypothesis?
An educated guess as to what will happen during an experiment
What is a null hypothesis?
A hypothesis that states there will be no change during an experiment (no statistical relationship)
What is random sampling?
A subsample is chosen randomly from a larger set (e.g. random number generator)
What is the importance of random sampling?
Avoids bias
What is systematic sampling?
A subsample is chosen from a larger set with a fixed periodic interval (e.g access points along a river)
What is the importance of systematic sampling?
Regular sample intervals
What are the 2 types of transect?
- Line transect
- Belt transect
Where are transects applied?
To environmental gradients
Why is sample timing important?
To ensure variability is detected
What is sample size dependent on?
Homogeneity
What is sample number dependent on?
Variability
Why is standardisation important?
To allow comparisons between different experiments and ensure consistent reliability
What are the 3 types of quadrat?
- Frame
- Grid
- Point
What do the 3 types of quadrat measure?
- Frame - percentage frequency
- Grid - percentage cover
- Point - local frequency
What are the limitations of quadrats?
- Subjective observations
- Plants may be flattened
What are kick sampling and surber sampling used for?
Sampling of freshwater invertebrate species
How does kick sampling work?
- Net held downstream in a river
- Agitation through kicking
- Invertebrates are caught in the net
What are the limitations of kick sampling?
- Organisms may swim away
- Difficult to standardise
How does surber sampling work?
- Net attached to a frame is held downstream in a river
- Agitation in the frame using a trowel or a stick
- Invertebrates are caught in the net
What are the limitations of surber sampling?
- Difficult on uneven river beds
- Water flow must be fast
How can kick sampling and surber sampling be standardised?
- Same amount of kicks
- Same sized net
What is colonisation media?
Providing a suitable habitat which is attractive to species that an individual wants to monitor (e.g. beetle banks)
What are the limitations of colonisation media?
- Habitat may not be colonised
- Affects true population size
What is a pitfall trap used for?
Sampling of small terrestrial species (e.g. insects)
How does a pitfall trap work?
A small container is placed in the ground level to the surface and covered before being left for a period of time
What are the limitations of a pitfall trap?
- More mobile organisms are caught
- Possible predation in the trap
How can a pitfall trap be standardised?
- Same sized container
- Same preservation fluid
- Same period of time it is left for
What is a sweep net used for?
Sampling of invertebrates in ground vegetation
How does a sweep net work?
A net is swept in a figure of eight configuration and repeated
What are the limitations of a sweep net?
- Flying organisms may escape
- Some organisms may be harmed
How can a sweep net be standardised?
- Same number of sweeps
- Same sweep length
What is a beating tray used for?
Sampling of invertebrates in tall vegetation
How does a beating tray work?
Vegetation is shaken and anything that falls out is collected in a tray
What are the limitations of a beating tray?
- Difficult to standardise
- Flying organisms may escape
What is a light trap used for?
Sampling of night-flying insects (e.g. moths)
How does a light trap work?
Flying insects are attracted to the UV light and are trapped, allowing for counting and identification the next day
What are the limitations of a light trap?
- No moths will be present if it rains
- Different insects are attracted to different wavelengths of light
What is a tullgren funnel used for?
Sampling of mobile invertebrates in leaf litter or soil
How does a tullgren funnel work?
A sample is placed on mesh beneath a light which causes organisms to move downward away from the light and through the mesh into a funnel and collection pot
What are the limitations of a tullgren funnel?
- Only species repelled by heat or light will be collected
- Only small organisms fit through the mesh
What is earthworm extraction used for?
Sampling of earthworms in soil
How does earthworm extraction work?
Irritant is added to the soil to force earthworms to the surface for counting and identification
What are the limitations of earthworm extraction?
- Earthworms may move deeper
- Earthworms may die
What is the most common abundance scale?
DAFOR
What does DAFOR stand for?
Dominant
Abundant
Frequent
Occasional
Rare
What is species frequency?
A measure of the dispersal of a species by recording the proportion of samples in which they were found
What does the Lincoln Index calculate?
An estimate of species’ population size (capture, re-capture)
What are the limitations of the Lincoln Index?
- Assumes no population change
- Assumes marked individuals mix freely with the rest of the population
What does Simpson’s Index of Biodiversity calculate?
Biodiversity of an area
