envi sci aqa - research methods

• What are the points to talk about when designing a practical investigation question?

  - method and equipment used

  - preliminary study?

  - sample locations

  - type of sampling

  - number of sample and repeats

  - sampling timing

  - size of samples

  - how to standardise

  - stats test
• How can random sampling be used to select sample locations?

  - location can be laid out on a grid a random number generator can be used to select the coordinates of the sample site

  - helps avoid bias
• How can systematic sampling be used to select sample locations?

  - use of regular chosen intervals

  - often use transects

  - avoids bias
• Why are practical investigations standardised?

  - fair comparison to other investigations

  - provides reliable data
• Why is ecological monitoring carried out?

  - find out which species are present

  - monitor habitat conditions

  - monitor features of population e.g. population size
• What are the ecological monitoring equipment used?

  - quadrats

  - pond nets

  - kick sampling

  - surber samplers

  - sweep nets

  - pit fall traps

  - beating trays

  - light traps

  - tullgren funnel
• What do you need to know about all monitoring equipment?

  - how its used

  - limitations

  - how to standardise
• Quadrats?

  - size should be selected depending on habitat/species being studied e.g. ground flora 1x1m

  types of quadrats

  - open frame (mark out an area)

  - grid (divide area into squares)

  - point (raised)

  limitations?

  - may be subjective
• Pond nets?

  - used to sweep through water to capture smaller aquatic species

  limitations

  - mobile species can escape
• Kick sampling?

  - net held facing into river current

  - scraping of boot in front of net disturbs river bed

  limitations

  - accurate standardisation is difficult

  - some organisms can avoid the net

  - fragile organisms may be destroyed
• Surber samplers?

  - box-like frame with net fixed to river bed

  - river bed in front disturbed

  limitations

  - can only be used with past water flow
• Pitfall traps?

  - containing placed in a whole

  - cover over the top to prevent larger animals from falling and flood

  - insects fall into the trap

  limitations

  - only mobile species on ground are caught

  - trapped carnivourus species may eat others

  - some species can avoid/escape trap
• Beating trays?

  - sheet/tray is placed underneath a vegetation

  - vegetation is beaten several times and invertebrates fall onto the sheet

  limitations

  - difficult to standardise

  - some species are not dislodged

  - some species fly away and are not caught
• Light traps?

  - flying insects when dark are attracted to the light and then fall into a container

  limitations

  - difficult to compare results with different light traps as different brightneses and wave lengths

  - moths only fly in adult phase

  - weather can impacts flying activity
• Tullgren funnel?

  - sample of leaf little/soil placed on mesh beneath a light

  - the light/heat repels some mobile invertebrates which move downwards pass the mesh and fall into a container

  limitations

  - only species that are repelled by heat/light will be collected

  - some may die from the heat

  - some to large to pass through mesh
• What are all the numerical measures used to compare data?

  - population size/density

  - abundance scales (DAFOR scale)

  - species richness/diversity

  - percentage vegetation cover
• How can the total population be estimated?

  - the Lincoln index
• How does the Lincoln index work?


  - a sample of population is caught, counted, marked and released

  - some time later a second sample is caught and counted

  - individuals with marks are also counted

  - data then put into the equation
• What is the Lincoln index equation?

  - total population = number in 1st sample x number in 2nd sample / number of marked individuals in 2nd sample
• What assumptions does the Lincoln index reply on?

  - species are mobile and can be caught

  - size of population does not change e.g. births and deaths

  - marks do not fall off/ware away

  - marks do not affect the survival rates of the species

  - marked individuals mixed with the population
• How can the quality of an environment be estimated?

  - biotic indices

  - use of present/absence species to indicate the quality of the environment
• What characteristics of species used for biotic indices have?

  - different sensitivities to the pollution

  - easy to identify

  - easy to find

  - common species

  - normally present

  - generally distributed
• What are the pros and cons of biotic indices?

  + help trace source of pollution

  + no need for expensive equipment

  + monitor current levels of pollution

  - can be time consuming

  - identification can be difficult
• How can biodiversity be estimated?

  - Simpsons index
• What data is collected for Simpsons index?

  - N = total number of individuals of all species

  - n = number of individuals of a particular species
• What are all the specialist techniques for ecological research? -
• What are all the abiotic factors we need to knows how to measure?

  - light intensity

  - humidity

  - wind velocity

  - water turbidity

  - water pH

  - soil temp

  - soil texture

  - soil water content

  - soil organic matter content
• What must you do with all electronic meters?

  - calibrate
• How is light intensity measured?

  - calibrated light meter

  - sensor orientation must be same
• How is humidity measured?

  - whirling hygrometer

  - electronic humidity meter
• How is wind velocity measured?

  - anemometer

  - same distance from ground

  - no obstacles to disrupt air flow

  - must face wind in same direction
• How is water turbidity measured?

  - secchi disc
• How does a secchi disc work and what are the limitations?

  - secchi disco is lowered until black and white sectors can not be distinguished

  limitations

  - subjective

  - sunlight levels affect visibility

  - water may not be deep enough
• How is soil temp measured?

  - soil thermometer

  - pushed 10cm into ground

  - leave until alcohol stops moving

  - take recording whilst in soil
• How is soil texture measure?

  - soil sieves
• How do soil sieves work?

  - stack of sieves with largest mesh at the top and smallest at the bottom

  - dried crushed soil sample placed at the top

  - sieve stack is shaken for 2 mins

  - sand, silt and clay sediments collect at different sieves and can then be collected and weighed individually to calculate proportions of each texture
• How does soil sedimentation measure soil texture?

  - lager objects removed from soil sample and sample is dried and sieved

  - placed into to cylinder half filled up with water

  - left for suspension to happen

  - proportion of total volume of each texture category can then be calculated
• How is soil water content measured?

  - soil sample is collected, weighed and placed in sealed bag to prevent evaporation

  - soil sample is placed in a pre-weighed basin

  - basin is heated at about 100C for 24 hours

  - the basin is then re-weighed

  - percentage water content can then be calculated
• How is percentage water content calculated?

  - (wet soil mass - dry soil mass / wet soil mass) x 100
• How is soil organic matter content measured

  - dry soil sample is collected using soil water content method

  - dry soil sample is weighed

  - crucible is then strongly heated to around 500C using furnace of bunsen burner

  - crucible is then re-weighed

  - percentage organic matter content then be calculated