Research Methods (AS & A2) (Complete) Flashcards
1
Q
What is accuracy?
A
Measure of how close recorded result is to real value
2
Q
What is precision?
A
Intervals between possible recorded results, eg ruler measuring in millimetres → more precise than one in centimetres
3
Q
What is a representative sample?
A
Sample accurately reflecting complete data set
4
Q
What does a reliable method provide?
A
Consistent, accurate results
5
Q
What is an anomalous result and how can you see whether it’s a ‘real’ result or caused by other variables?
A
-Result differing from other results w/ which it was expected to be similar
-Repeating the study
6
Q
What does a valid study provide?
A
Precise, accurate, reliable results upon which conclusions can be based
7
Q
What factors required are in environmental fieldwork/lab work?
A
-Appropriate risk management
-Practical equipment & materials required & how to use these safely + correctly
-Data to be collected & analysed; using appropriate apparatus/instruments to record quantitative measurements (eg pH) & measure abiotic/biotic factors, selecting right sampling & statistical analysis techniques
8
Q
What are the general principles of scientific investigations?
A
-Identifying topic of interest
-Finding out what’s already been learnt
-Formulating hypothesis/null hypothesis that can be tested
-Designing & carrying out experiment to test hypothesis
-designing investigation, eg including consideration of location & timing of sampling sites, # & size of samples, standardised technique, stat analysis
-Analysing results & drawing conclusions
-Planning further research to fill gaps in existing knowledge/develop study further
9
Q
Scientific methodologies; why is careful planning needed?
A
To ensure data collected can be used to conclude whether a hypothesis should be rejected or accepted
10
Q
Scientific methodologies; what is done if all the data existing about a particular issue can’t be collected?
A
-Sub-samples collected, then used to estimate full situation
-Will only produce reliable conclusions if sub-samples are representative
11
Q
Scientific methodologies; what must the planning of sub-samping consider?
A
Factors that may affect how representative they are; location, timing, size, number
12
Q
Scientific methodologies; what should be used to test the reliability of a method?
A
A preliminary study
13
Q
Sampling; what needs to be considered for the location of a sample?
A
-If data aren’t being collected at single location, decisions will need to be made about positioning of sampling sites
-It’s essential to avoid intro of bias due to deliberate selection of locations for convenience/to support or dismiss hypothesis → can be achieved by random/systematic sampling
14
Q
Sampling; how does the shape of the study area affect random sampling?
A
-If study area has regular shape, grid can be laid out & coordinates of sampling sites selected w/ random numbers
-If study area has irregular shape, all possible sampling sites can be numbered + selected using random number generator
15
Q
Sampling; what is systematic sampling and how is choice of sampling site made?
A
-Involves samples taken using chosen interval distance/spacing
-Choice of sampling sites isn’t based on choices made using observable differences in study area
16
Q
Sampling; how should the distance between sampling sites be chosen?
A
To detect variable data w/out collecting more data than necessary → can be determined w/ preliminary study
17
Q
Sampling; why does sampling need to sometimes be done on different occasions and how is the timing determined?
A
-If factor measured changes w/ time, it’ll be necessary to sample on diff occasions to produce mean result representing ‘typical’ value/identify trends in changing values
-Ideal time interval betw samples depends upon rate at which values change → can be determined w/ preliminary study
18
Q
Sampling; what are some examples of sampling time scales and variables that may be affected?
A
-Long-term changes; population changes eg tigers, area of rainforest, atmospheric CO² level
-Seasonal changes; presence of migratory species, populations of annual wildflowers, temp, atmospheric CO² level, river level
-Diurnal changes (24hr); light levels, temp, atmospheric CO² levels
-Weather-related changes (minutes-weeks); flying insect activity, wind velocity, temp
-Other short-term changes; road noise level
19
Q
Sampling; when are different sample sizes needed and how can this be determined?
A
-If variable measured isn’t homogeneous, larger samples are more likely to produce representative results
-Sample size needed can be determined using preliminary study
20
Q
Sampling; how and why can the number of samples vary within studies?
A
-Single samples may not be representative as may be variability betw samples. Collecting multiple will help eliminate effect of variability
-# of samples needed to produce representative mean depends upon degree of scatter around mean, assessed by calculating standard deviation
-Can be found w/ preliminary study
-# of samples collected will also depend upon how results will be analysed. It’s easier to assess degree of stat sig of results w/ larger sample
21
Q
Sampling; why and how are techniques standardised?
A
-To allow comparison of results collected at diff times/locations/researches, must be collected in exactly the same way
-Other variables affecting results must either be controlled/monitored to assess their effects
22
Q
Population studies; why are good surveys essential in ecological monitoring?
A
-To find out which species are present
-To monitor habitat conditions, how they change & which conditions individual species require
-To monitor features of populations, how they change over time
-Population size
-Age structure
-Growth rates
-Breeding rates
-Territory size
-Population movements
-Reliable, representative data important in making good conservation management decisions
23
Q
Population studies; what is the technique used to monitor ecological conditions in ecosystems & species there depend upon?
A
-on what is measured
-Affected by rapid development of new techniques that may produce better results; more representative, quicker, more cost effective
24
Q
Population studies- ecological techniques; what is a quadrat and what can the results be used for?
A
-Study area, usually square, within which populations can be studied
-Results from number of quadrats can be scaled up to estimate overall situation for entire area
25
Population studies- ecological techniques; how should quadrat size be selected and what are examples of typical quadrat sizes?
-Dependent upon the habitat & groups of species being studied
Typical sizes=
-Lichens; 10 x 10cm
-Ground flora; 0.5 x 0.5m
-Trees in forest; 100 x 100m
-Bird presence survey; 10 x 10km
26
Population studies- ecological techniques; what is an open frame quadrat?
-Mark out a study area
-Smaller ones may be made of metal/plastic frame
-Larger ones use reference coordinates marked out by measuring tapes/GPS coordinates
27
Population studies- ecological techniques; what is a grid quadrat?
Sub-divided into smaller squares, eg 10 x 10, each small square representing 1% of area
28
Population studies- ecological techniques; what is a point quadrat and when can it be used?
-Used to collect similar info to other quadrats but don't use square area
-Can be used where ground flora → too tall for other quadrats as it'd be flattened & provide unrepresentative results; % cover estimate would be inaccurate & shorter plants may be obscured by flattened foliage of taller plants
-Wooden frame supports metal rods, usually 10. Each time rod touches leaf, counts as 10% cover
29
Population studies- ecological techniques; what are the limitations of quadrats?
-Subjective judgement may be involved; eg estimating % cover
-Quadrat frame may flatten/move plants
30
Population studies- ecological techniques; what is the method for using a pond net?
-Can be swept through water/aquatic vegetation to capture invertebrates, amphibians, fish
-Using a particular length of sweep/number of sweeps, can be used in an attempt to standardise method & produce comparative data
31
Population studies- ecological techniques; what is the limitations of pond nets?
Mobile species may escape
32
Population studies- ecological techniques; what is kick sampling and the method used for it?
-Collects invertebrates living on riverbed
-Net held w/ its straight edge on river bed & its face open to the current
-Riverbed in front of net is disturbed by repeatedly scraping boot over it. Invertebrates that are dislodged are caught in the net
-Controlling number & length of kicks can be used to standardise the method
33
Population studies- ecological techniques; what are the limitations of kick sampling?
-Accurate standardisation is difficult
-Buried organisms/those fixed on stones may not be dislodged
-Some organisms can swim & avoid net
-Water flow rate → variable, affects capture rate
-Fragile organisms may be destroyed
34
Population studies- ecological techniques; why are surber samplers mare efficient than kick sampling?
Provide a more standardised technique
35
Population studies- ecological techniques; what is the method used for kick samplers?
-Fixed area of riverbed is sampled within box-like frame
-Riverbed is disturbed using trowel/similar tool & stones are inspected manually
-Netting at sides of net opening reduces number of organisms escaping
36
Population studies- ecological techniques; what are the limitations of surber samplers?
-Can only be used where water is fast enough to carry organisms → net
-Sampler's small size can make it hard to set on rough substrates in deep water resulting in loss of large organisms
37
Population studies- ecological techniques; what are plankton nets and the method used for them?
-Catch planktonic organisms floating in water, some can be used to give quantitative estimates of populations
-Fine mesh is pulled through water, can be used vertically/horizontally
-Net can be fixed where there's a current/may be towed through water
-Different mesh sizes are used for diff sizes of organisms. Phytoplankton are smaller than zooplankton so smaller mesh size is used
38
Population studies- ecological techniques; what are the limitations of plankton rets?
-Nets w/ coarse mesh size don't catch smaller organisms
-Nets w/ fine mesh may become clogged by phytoplankton, preventing water flawing into net
39
Population studies- ecological techniques; what are sweep nets and what is the method used for them?
-Are sturdy nets used to sample invertebrates in ground vegetation like grassland
-Net is swept through vegetation so dislodged organisms are caught
-Standardisation of method can be attempted by using same number of sweeps of same length
40
Population studies- ecological techniques; what is the limitation of sweep nets?
Mobile species may escape, like flying insects
41
Population studies- ecological techniques; what is the method used for aerial insect nets and its limitations?
-Lightweight nets used to capture flying insets like butterflies
-Successful collection depends on agility of researcher & prey
42
Population studies- ecological techniques; what is the method used for colonisation media?
Some species can be monitored by providing suitable habitats that they may colonise
43
Population studies- ecological techniques; what are the limitations of colonisation media?
-Not all species can be monitored as they may not use media
-Accurate population estimates aren't possible as proportion colonising media isn't known
44
Population studies- ecological techniques; what are pitfall traps used for?
Sampling populations of mobile animals on ground surface
45
Population studies- ecological techniques; what is the method used for pitfall traps?
-Container is placed in a hole in the ground w/ its open end making a close fit w/ soil & top being level w/ the ground surface
-Cover is supported over the opening to exclude predators that may eat animals that are caught & to prevent flooding by rain
-Trap is checked after a standard period of time, eg 24 hrs
-Preservative fluid may be used to kill captured animals for later study
46
Population studies- ecological techniques; what are the limitations of pitfall traps?
-Only mobile animals that live on the ground surface are caught
-More mobile species are more likely to be caught
-Trapped carnivorous animals may kill other organisms that have been caught
-If a preservative is used, it may attract/repel certain species
-Some species avoid traps/can escape
47
Population studies- ecological techniques; what are beating traps used for?
To sample invertebrates present on vegetation above ground
48
Population studies- ecological techniques; what is the method used for beating traps?
-Sheet/tray is placed beneath vegetation which is beaten several times w/ a stick
-Dislodged invertebrates fall onto sheet & are collected for identification & counting
49
Population studies- ecological techniques; what are the limitations of beating trays?
-It's difficult to standardise method between researchers, eg vigour of hitting branches
-Some species aren't dislodged
-Thicker branches shake less so organisms are less likely to be dislodged
-Some species fly away & aren't caught
-Higher branches can't be reached
50
Population studies- ecological techniques; what are light traps used for?
To collect night-flying insects attracted by bright lights, usually UV lights
51
Population studies- ecological techniques; what is the methods used for light traps?
-Flying insects, esp moths attracted to light fall into a container. Container is checked the following morning
-Insects that have been caught are identified & counted
52
Population studies- ecological techniques; what are the limitations of light traps?
-Moths only fly during their adult phase & activity is affected by weather + seasons so failure to find species doesn't mean it's absent
-Brightness & light wavelengths emitted by light can affect their attractiveness to insects so it may be hard to compare results produced by diff types of trap
53
Population studies- ecological techniques; what are tüllgren funnels used for?
To sample mobile invertebrates in leaf litter/soil
54
Population studies- ecological techniques; what is the method used for tüllgren funnels?
-Sample of leaf litter/soil placed on mesh beneath a light
-Light & heat repel some mobile invertebrates which more downwards, pass through mesh & fall into container
-Tüllgren funnel is left operating for standard period of time
-Invertebrates collected are identified & counted
55
Population studies- ecological techniques; what are the limitations of tüllgren funnels?
-Only species repelled by heat/light will be collected
-Some organisms may die/stop moving due to heating/desiccation before they're collected
-Some organisms are too large to pass through mesh
56
Population studies- ecological techniques; what do suction samplers do?
-Capture airborne insects/invertebrates dislodged from vegetation
-Some just show presence of organisms but some give quantitative data
57
Population studies- ecological techniques; what is the method used for suction samplers?
There's several types of suction sampler used to collect invertebrates from the ground, vegetation or atmosphere;
-Air suction samplers capture flying insects. If air flow rate is measured & cross-sectional area of collector tube is known then number of insects per unit vol of air can be estimated
-Motor-driven suction samplers can be used to sample invertebrates on ground vegetation. Area of ground covered by suction pipe is known, so population density of invertebrates can be estimated
-Rooter= suction sampler used to pick up invertebrates that have been found. It's a handling method, not a population sampling technique
58
Population studies- ecological techniques; what are the limitations of suction samplers?
-Some invertebrates may not be caught by an air sampler; may sense it and fly away
-Some insects may not be dislodged from vegetation by suction sampler
59
Population studies- ecological techniques; why do earthworms need to be extracted from the soil?
They're difficult to observe, so need to be removed for their populations to be monitored
60
Population studies- ecological techniques; what is the method of soil flooding?
-Mark out a sample area of suitable size, 0.5 x 0.5m/1 x 1m
-Remove vegetation that may hide worms at surface
-Add irritant solution, eg detergent/mustard in water
-Keep adding until soil is saturated
-Saturate surrounding area (so worms are less likely to move sideways)
-Add more as solution infiltrates into soil
-Collect worms coming to surface
-Continue collecting until no more worms appear/for suitable time period/standardised time period
-Count/measure/weigh/identify collected worms
61
Population studies- ecological techniques; what are the limitations of soil flooding?
-Irritant solution may not percolate through impermeable soils
-Irritant solution may not reach deepest worms
-Worms may more sideways/down
-Worms may die
-Worms may move too slowly to be collected during study period
62
Population studies- ecological techniques; what is the method and limitations of soil pit extraction?
-Method; pit of chosen area & depth is dug, eg 0.5x 0.5 x 0.5m, soil is hand sorted & worms collected
-Limitations; smaller worms may be overlooked, digging may disturb worms that move sideways/down out of sample site
63
Population studies- quantitative/comparative/numerical measures; how can you measure population size/density?
-Method used depends on features of species studied; for some it may be possible to count all individuals in a pop., eg all birds in a cliff nest colony
-Some species are dispersed over large areas so sub-sampling is necessary
-Some species can’t be easily observed but may be possible to catch sample of pop. Mark-release-recapture may be used to estimate total pop., eg Lincoln Index
64
Population studies- quantitative/comparative/numerical measures; what are abundance scales and how are they categorised?
Involve allocating species to diff categories based on relative abundance, eg dafor scale species are categorised into the following groups;
-Dominant
-Abundant
-Frequent
-Occasional
-Rare
65
Population studies- quantitative/comparative/numerical measures; what are the advantages and disadvantages of adundance scales?
-Judgement of abundance is subjective, can vary betw diff people but it’s quick & allows many areas to be studied quickly
-Results aren’t quantitative so statistical analysis of results may not be possible
66
Population studies- quantitative/comparative/numerical measures; what is species richness/diversity and what does it involve?
-Measure of number of diff species found in area
-Often focuses on particular taxon, eg birds, ground flora, reptiles
-To standardise method & allow for comparison between sites, may be used in specific areas, eg tree species in 100 x 100m squares
67
Population studies- quantitative/comparative/numerical measures; what is species frequency?
Measure of dispersal of species by recording proportion of all samples in which it was found
68
Population studies- quantitative/comparative/numerical measures; what is species density?
Relates number of species found to specific area & makes species richness results more compatible, eg number of species per square metre
69
Population studies- quantitative/comparative/numerical measures; how is percentage vegetation cover estimated?
By observing the proportion of;
-Ground covered by vegetation for ground flora
-Sky obscured by vegetation for tree cover
Grid quadrats are commonly used
70
Population studies- quantitative/comparative/numerical measures; what does the Lincoln index estimate?
Total population by catching a proportion of the population
71
Population studies- quantitative/comparative/numerical measures; what is the method used for the Lincoln index?
-Sample of population is caught, counted, marked, released
-Some time later, second sample is caught & counted. Individual already marked from first sample are counted
-Lincoln index formula is used to estimate total population;
Number in 1st sample x number in 2nd sample/number in 2nd sample with marks
72
Population studies- quantitative/comparative/numerical measures; what are the limitations of the Lincoln Index?
Estimation of population relies on some assumption;
-Individual animals are mobile & can be caught
-Size of population doesn't change during time of study, eg due to births, deaths, migration
-Being caught & marked doesn't affect survival rates
-Marks dan't fall off/wear away during study
-Marked individuals mix freely w/ rest of population
-All individuals in population have same chance of being caught
73
Population studies- quantitative/comparative/numerical measures; what is Simpson’s Index of Biodiversity used to assess?
-Variety & abundance of species in area
-May be used to consider all species but is often used for single taxonomic group, eg biodiversity of ground flora/insects
74
Population studies- quantitative/comparative/numerical measures; what is the formula of Simpson’s Index of Biodiversity and what do values indicate?
-D = N (N-1) / sum of (n(n-1) , where;
-D= index of diversity
-N= total number of individuals of all species
-n = number of individuals of a particular species, each species has own n (n-1) value
-Higher value= higher biodiversity
75
Population studies- quantitative/comparative/numerical measures; what is the method used and limitation of species identification ID keys?
-Often dichotomous keys where sequence of questions narrows down possibilities, based on unique visible features; size, shape, markings
-Limitations; some species lack characteristic features & look the same as other species, characteristic features may not always be present, eg flowers and seeds
76
Specialist techniques used in ecological research- imagery; why are image databases used?
Individuals of some species can be recognised from image databases of unique features
-Eg Tiger facial stripes, Cheetah tail markings, Whale Shark spot patterns, dolphin fin marks/injuries & zebra stripes
77
Specialist techniques used in ecological research- imagery; what does being able to identify individuals provide information on?
-Territory size
-Population movements, like migrations
-Lifespans
-Social groupings
78
Specialist techniques used in ecological research- imagery; what is the limitation of image databases?
Few species have unique features that can be used to identify individual
79
Specialist techniques used in ecological research- imagery; what are motion-sensitive cameras used for?
Habitat monitoring to detect presence/activity of animals using visible light photography during day or infrared photography at night
80
Specialist techniques used in ecological research- imagery; what can Closed circuit TV (CCTV) be used for?
To observe animal behaviour w/ lower risk of disturbance than if researchers visit site, eg for researching birds' nests
81
Specialist techniques used in ecological research- marking; what is a method used to identify individual animals previously caught?
Rings placed on birds' legs; provide information on movements & lifespan if are caught later
82
Specialist techniques used in ecological research- DNA databases; how can DNA be used to detect the presence of a species?
Presence of some aquatic species can be detected from DNA of cells they shed into water; environmental DNA/eDNA
83
Specialist techniques used in ecological research- DNA databases; what are examples of eDNA being used and how has this been advantageous?
-eDNA evidence of presence of legally protected Great Crested Newt may prevent development being permitted in UK that'd damage its habitat
-In USA, presence of non-indigenous Bighead Carp & Silver Carp is detected using eDNA
84
Specialist techniques used in ecological research- DNA databases; how can regional populations be identified using DNA and what are examples of this?
-Each separate population within species has its own unique gene pool
-May be possible to identify where plant/animal came from if its DNA can be compared w/ DNA database for diff regional populations
-This technology is being developed to track sources of tropical timber, elephant ivory & some commercially fished species, eg cod & haddock
85
Specialist techniques used in ecological research- auditory monitoring; what are sonograms and how are they used?
-Records of the sounds made by taxa, eg dolphins, bats & some insects
-Can be used as evidence of their presence, abundance & activity
86
Specialist techniques used in ecological research- position monitoring; what are the range of technologies used to monitor the location of individuals?
-Radio, GPS & some acoustic transmitters can be used to track animals in air/freshwater
-In seawater, acoustic transmitters are used. They give real-time info of current position of animal carrying transmitter
-Geolocator tags may be used where transmitters would be too heavy/where battery life would be too short for a long-term study; are small & only collect data on time + light. When animal is re-caught, data can be downloaded & used to work out latitude + longitude of animal for each day during study.
87
Specialist techniques used in ecological research; what do data recorders collect data on and how is this obtained?
-Range of abiotic factors, eg temp, light intensity, light wavelength, salinity & pressure
-Data may be downloaded when recorder is recovered, or by radio, or auditory transmission
88
Specialist techniques used in ecological research- sensor carrier system; why are carrier systems used?
If data is to be collected in a single location then sensor just needs to be placed there but it's often necessary to have a carrier system to move the sensor to the study areas
89
Specialist techniques used in ecological research- sensor carrier system; what are examples of sensor carrier systems?
- ROV (Remotely Operated Vehicles), incl drones
-AUV (Autonomous Unmanned Vehicles)
-Balloon
-Aircraft
-Satellites
-Animals
90
Specialist techniques used in ecological research- sensor carrier system; why are satellites and sensors on satellites important?
-Satellites are increasingly important for collecting info that increases our understanding of environmental issues & for making well-informed decisions
-Sensors mounted on satellites can be used to collect large amounts of data about the Earth using diff types of electromagnetic radiation
91
Specialist techniques used in ecological research- sensor carrier system; how are different types of electromagnetic radiation used in satellite sensors to collect data about the Earth?
-Reflected visible light provide images of large areas of the Earth's surface. These can be used for creating maps, monitoring land use changes & monitoring environmental changes, eg deforestation + flooding
-Infrared (Ir) emitted by the Earth's surface can be used to monitor vegetation density & temp
-Weather monitoring & forecasting use sensors that detect cloud cover, humidity, wind velocity, wind direction & temp
-Radar microwaves emitted by satellite which reflect off Earth's surface can be used to monitor; wind velocity, sea surface altitude, wave height & oil pollution
92
Specialist techniques used in ecological research- sensor carrier system; what do GPS satellites use and why?
-Radio waves
-To track positions of mobile animals, floats in the oceans, location of sampling sites
93
Specialist techniques used in ecological research; how can species leave indirect evidence of their presence?
-Nests/burrows
-Droppings; can give info on diet, gender, territory size
-Feeding marks, eg chewed nuts
-Owl pellets; give info on diet
-Tracks/footprints
-Territorial marks, eg scratching posts
94
Abiotic factors- electronic meters; which abiotic factors can be measured using electronic meters?
-Temperature
-pH
-Dissolved oxygen
-Light level
-Wind/water velocity
95
Abiotic factors- electronic meters; how are electronic meter readings made accurate and what is done if this isn't possible?
-Meter must be calibrated by adjusting its reading to be same as meter known to be accurate
-If this cannot be done, % error should be noted so results can be adjusted
96
Abiotic factors- electronic meters; how can light intensity be measured with electronic meters?
-A calibrated light meter can be used to measure light intensity
-Method must be standardised, esp sensor orientation
97
Abiotic factors- electronic meters; what is a whirling hygrometer and how does it measure humidity?
-Traditional method of measuring humidity
-Uses 2 thermometers, one being dry, other wet
-When they’re spun, wet bulb is cooled by evaporation of the water, dry bulb isn’t cooled
-Rate of evaporation on wet bulb depends on humidity, so temp difference betw the two thermometers can be compared w/ a table of values to estimate humidity
98
Abiotic factors- electronic meters; how is an accurate reading acquired with a hygrometer?
ust be spun until there’s no further cooling
99
Abiotic factors- electronic meters; how is an accurate reading acquired with a electronic humidity meter?
As w/ all electronic meters, they must be calibrated
100
Abiotic factors- electronic meters; how is wind velocity measured?
An electronic anemometer
101
Abiotic factors- electronic meters; how must an anemometer be standardised?
-Distance from the ground
-No obstacles to air flow
-Axis of rotation must be horizontal (impeller type) or vertical (rotating cup type)
-Impeller type anemometers must face into wind
102
Abiotic factors- electronic meters; how is a secchi disc used to measure water turbidity?
-Lower a secchi disc into the water until the black & white sectors can’t be distinguished
-Record the depth of disc (length of string below water level)
103
Abiotic factors- electronic meters; what are the limitations of using a secchi disc to measure water turbidity?
-Depth judgement is subjective
-Sunlight levels may affect visibility
-Water may not be deep enough for segments to become indistinguishable
104
Abiotic factors- electronic meters; how is a turbidity bottle used to measure water turbidity?
-Add a standard depth of water to a turbidity bottle
-Hatched circles at the bottom of the bottle are observed to see which are obscured
-Note the coarsest circle which can’t be distinguished
105
Abiotic factors- electronic meters; what are the limitations of using a turbidity bottle to measure water turbidity?
-Judging which circles can be distinguished is subjective
-Light levels may affect visibility
106
Abiotic factors- electronic meters; how are test strips used to measure the concentration of ions in solution?
-Have bands of reagents that change colour when they react w/ ion
to be measured
-Strips are dipped into solutions being analysed then compared w/ a reference colour chart
107
Abiotic factors- electronic meters; how are electronic colorimeter used to measure the concentration of ions in solution?
-Reagent is added to test solution
-Intensity of colour produced is measured by a light meter that’s adjusted to measure a specific wavelength of light
108
Abiotic factors- electronic meters; how are ion selective electrodes used to measure the concentration of ions in solution?
-An electronic probe is put into the test solution
-Electrode potential that’s produced by the solution betw 2 electrodes is used as a measure of the ion concentration
109
Abiotic factors- electronic meters; what is the limitation of using ion selective electrodes to measure the concentration of ions in solution?
The presence of other ions can lead to inaccurate results
110
Soil analysis; how is soil sampled and why?
-If soil is to be analysed in the lab then a representative sample must be collected
-A soil auger will collect a sample of known cross-sectional area & depth
-Collecting soil w/ a trowel produces less representative samples that can’t be compared w/ other samples as reliably
111
Soil analysis- temperature; how is a soil thermometer used to measure soil temperature?
-Thermometer must have a protective metal tube to prevent it breaking
-Push the thermometer into the soil to a standard depth, eg 10 cm
-Protect the thermometer from direct sunlight
-Leave it until alcohol liquid stops moving & constant temp is shown
-Temp is read while thermometer is still in soil
112
Soil analysis; what does soil texture assess?
Proportions of the mineral particles in different size categories; sand, silt & clay
113
Soil analysis- texture; how are soil sieves used to measure soil texture?
-Stack of sieves is assembled in order of mesh size, w/ coarsest mesh at top
-A dried, crushed soil sample is placed in top sieve
-Sieve stack is shaken by hand/mechanically, for 2 mins (long enough for no more particles to fall through). Particles drop through sieves until they reach a sieve where holes are too small to pass through
-Each portion is weighed & % composition of the 3 portions calculated
-Wet sieving is also possible. The sub-samples collected in each sieve must be dried before weighing;
-Top sieve (mesh size > 2mm) contains pebbles, twigs etc. These aren’t part of the soil
-Second sieve (0.02 - 2mm) contains sand. (Some stacks have extra sieve to separate coarse & fine sand)
-Third sieve (0.002 - 0.02mm) contains silt
-Base container holds clay
114
Soil analysis- texture; how is sedimentation used to measure soil texture?
-Larger objects are removed from dried soil sample by using a 2mm sieve/by hand, eg pebbles, twigs
-Soil is crushed to ensure particles are separated
-Measuring cylinder is about 1/2 filled w/ soil, then topped up w/ water
-Top is sealed then cylinder is shaken by repeatedly inverting it
-Suspension is allowed to settle
-Total depth of settled soil components is measured after 2 mins, 2 hours, & 2 days
-Proportion of total volume of each textural category can then be calculated
115
Soil analysis; what is a soil triangle and how is it used?
-A triangular graph used to display combined proportions of the 3 mineral soil components
-Different areas of graph represent soils w/ characteristic properties
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Soil analysis; what is the method for finding the soil water content?
1.Soil sample is collected using a standardised technique eg a core sampler/auger
2.Soil sample is placed in a sealed bag to prevent water loss by evaporation
3.Larger mineral particles, organic detritus & visible organisms are removed
4.Soil sample is placed in a pre-weighed evaporating basin/similar container
5.Basin is heated at about 100°C for 24hrs
6.Basin is reweighed
7.Stages 5) & 6) are repeated until constant mass is reached
-Percentage water content can then be calculated;
Percentage water content= Wet soil mass - Dry soil mass/Wet soil mass x 100
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Soil analysis; what is the methods for finding the soil organic matter content?
-Follow Steps 1 -7 of soil water content method then;
8. Dry soil sample is placed in a pre-weighed crucible which is reweighed
9. Crucible is heated strongly in furnace/w/ Bunsen burner
10. Crucible is re-weighed
-If heating temp is 550°C+ then minerals may break down, eg calcium carbonate breaking down, releasing CO². This’d give an inaccurately high estimate of organic matter as reduction in mass wouldn’t be caused by loss of organic matter alone
11. Stages 9 & 10 are repeated until constant mass is reached
-The percentage organic matter content can then be calculated;
Percentage organic matter content= Dry soil mass - Burnt soil mass/Dry soil mass × 100
118
Soil analysis; what is soil bulk density?
The mass of dry soil per unit volume
119
Soil analysis; how can the volume of a soil sample be controlled?
Using a soil auger of known cross-sectional area & pushing it into the soil to a chosen depth
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Soil analysis; how can the dry soil mass be found?
Weighing the soil after it’s been heated at about 100°C to constant weight
121
Soil analysis- pH; (colorimetry) why is universal indicator solution used to measure pH in soil?
-pH indicator chemicals absorb different wavelengths of light at different pHs
-This colour change is predictable & can be used to measure pH by comparing colour of indicator w/ a reference chart
-Method is simple but is subjective as it relies upon judgement of colour
122
Soil analysis- pH; (colorimetry) what is the standard colourimetric method used to estimate the pH of a soil sample?
-Add 2.5cm^3 of soil to a test tube
-Add 1cm^3 of barium sulfate (toxic), which helps soil particles settle
-Add 3.5 cm^3 distilled water
-Add 10 drops of universal indicator solution.
-Firmly push a bung into tube
-Shake thoroughly & leave to stand for 15 mins
-Compare colour of coloured solution above soil w/ a colour chart
123
Soil analysis- pH; (colorimetry) what are universal indicator papers and how are they used to find the pH of a soil sample?
-These are strips of absorbent paper that are impregnated w/ universal indicator solution
-Papers can be dipped into solutions to be tested & any colour changes compared w/ a reference chart
-For soil samples, the procedure is similar to that for universal indicator solution. No universal indicator solution is added. A universal indicator paper is dipped into settled water sample & colour change is compared w/ a colour chart
-For water samples, the papers are simply dipped into sample & compared w/ a colour chart
124
Soil analysis- pH; how are electronic pH meters used to measure pH of a soil sample and how is this made accurate?
-Quantitative values produced by electronic meters can be easy to interpret & compare but it’s important to ensure results are accurate, representative & collected using a standardised method
-pH meter should be calibrated using buffer solutions of known pH
-Meter should be left to stabilise for long enough to give stable readings
-Probe should be inserted to a standard depth
125
Soil analysis- pH; what is the limitation of using electronic pH meters to measure the pH of a soil sample?
Need to regularly calibrate probe w/ buffer solutions makes this method less convenient than universal indicator papers
126
Specific practical investigations- climatic variability & use of renewable energy; how can intensity of solar power/light be measured and how is this made reliable?
-Using an electronic light meter
-As w/ all electronic meters, this should be calibrated to ensure it’s reliable & can be used w/ a standardised technique
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Specific practical investigations- climatic variability & use of renewable energy; what are the factors that affect the intensity of solar power?
Time of day, time of year & cloud cover
128
Specific practical investigations- climatic variability & use of renewable energy; which local factors affecting wind velocity can be investigated?
-Distance from the ground
-Topography
-Aspect in relation to prevailing winds
-Nearby trees/buildings
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Specific practical investigations- climatic variability & use of renewable energy; why is heat loss measured?
-Heat energy that must be added to a building, furnace, or heat store to maintain a constant temp depends upon rate at which heat is lost
-Reducing rate at which heat is lost will therefore reduce rate at which heat must be added
130
Specific practical investigations- climatic variability & use of renewable energy; what are the factors affecting heat loss?
-Thermal insulation; rate of heat loss depends upon thermal conductivity of surrounding material. The thicker the surrounding material, & lower the thermal conductivity, the lower the rate of heat loss, but each additional layer has a smaller effect than previous ones. If value of heat saving & cost of insulation are known then optimum thickness of insulation can be calculated
-Volume; heat energy stored in a hot mass of material is lost via external surface. As volume increases the surface area volume changes so rate of heat loss also changes. Total amount of heat lost will be increased as the surface area & amount of heat stored have also gone up. However, rate of heat loss per unit volume goes down so temp drops more slowly
131
Specific practical investigations- climatic variability & use of renewable energy; what are the factors that should be standardised when investigating the effect of volume on the rate of heat loss?
-The material the objects are made of, eg clay cubes, water-filled round-
bottomed flasks, or PET bottles
-3D shape
-Colour, darkness & texture of surface
-Experimental conditions like room temperature, air movements & contact w/ other materials & surfaces
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Specific practical investigations- climatic variability & use of renewable energy; why does the estimation of heat loss require careful planning & interpretation?
-Total amount of heat energy stored can be calculated using specific heat capacity & temp of materials used
-However, temp will vary throughout volume, being lower near surfaces & higher in the core
-It may also be higher near the top, if water-filled containers are used where convection currents may occur
133
Specific practical investigations- use of biotic indices in monitoring pollution; what is a biotic index?
A method of monitoring environmental conditions, usually pollutants, by
the presence/absence, state of health/growth & abundance/diversity of species which would normally be present
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Specific practical investigations- use of biotic indices in monitoring pollution; what are the advantages of using biotic indices?
-They monitor current pollution levels & can be used to estimate past levels
-They can help trace source of pollution
-They can be very sensitive to small changes
-Very low levels of pollutants which bioaccumulate may be detectable in raised concentrations in organisms
-They don’t need expensive monitoring equipment
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Specific practical investigations- use of biotic indices in monitoring pollution; what are the disadvantages of using biotic indices?
-Sorting samples can be time-consuming
-Identification can be difficult for the inexperienced
136
Specific practical investigations- use of biotic indices in monitoring pollution; what are the features of good indicator species?
-Easy to identify
-Normally present if there’s no pollution
-Normally common if there’s no pollution
-Widely distributed rather than found in groups
-Easy to find
-Ideally there’ll be a range of species w/ different sensitivities to pollution. In this case they may disappear in an order which indicates level of pollution
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Specific practical investigations- use of biotic indices in monitoring pollution; why can long-term effects of pollutants be difficult to assess by measuring levels of pollutants causing damage?
-These can fluctuate widely
-Eg, atmospheric concentrations of sulfur dioxide & other acidic gases vary widely, mainly due to varying rate of their removal by rain. This makes it difficult to measure concentration of pollutants such that they can be reliably correlated to damage they cause
138
Specific practical investigations- use of biotic indices in monitoring pollution; what may a better indication of pollution problems be achieved by?
-Measuring impact of pollution through abundance & diversity of organisms that are affected
-Organisms that are sensitive to pollution give an indication of past pollutant levels as well as what’s happening now
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Specific practical investigations- use of biotic indices in monitoring pollution; why can lichens be used to estimate long-term pollution conditions at different locations?
-They’re particularly sensitive to acidic conditions, w/ different species having different sensitivities so presence/absence, size & state of health of different species can be used to produce a scale of the severity of pollution
-This can be used to estimate long-term pollution conditions at different locations
140
Specific practical investigations- use of biotic indices in monitoring pollution; what are the factors that should be standardised when using lichens to estimate long-term pollution conditions at different locations?
-The surface on which lichens are found, as materials like limestone/granite will also affect pH
-Aspect of surface in relation to prevailing wind & thus exposure to rain
-Factors that influence lichen growth like exposure to sunlight
-It’s common to study lichen distribution on gravestones as their orientation normally faces west-east & substrate can be standardised; they’re often made of granite
141
Specific practical investigations- use of biotic indices in monitoring pollution; why are aquatic invertebrates used to measure aquatic pollution and what are some examples?
-A range of aquatic invertebrate taxa w/ different sensitivities to pollution are used to monitor pollution
-They meet the desired criteria
-Following taxa are often included; Stonefly larvae, mayfly larvae, caddisfly larvae, freshwater shrimps, freshwater hoglouse, midge larvae
142
Specific practical investigations- the effect of pH on seed germination; why does pH affect seed germination?
-High & low pH conditions denature proteins + inactivate enzymes
-Each species has its own range of tolerance
143
Specific practical investigations- the effect of pH on seed germination; how should plant species be chosen in the investigation?
Some species make good experimental subjects;
-Small seeds
-Genetic uniformity
-High normal germination rate
-Rapid germination
-These species aren’t necessarily the ones that produce results which can be applied directly to natural ecosystems
144
Specific practical investigations- the effect of pH on seed germination; how should the number of seeds and replicates be made?
Each test must use enough seeds to produce results that can be distinguished from each other if there’s a real difference, but not so many that unnecessary extra work is undertaken
145
Specific practical investigations- the effect of pH on seed germination; why should each test be replicated?
To allow anomalies to be identified & results to be statistically valid
146
Specific practical investigations- the effect of pH on seed germination; what choices should be made about pH range?
-Range of pHs tested should cover full range at which germination can take place
-This can be established w/ a preliminary study using a range of widely spaced pHs
-pH range investigated in final experiment would cover range from pH below lowest pH at which germination occurred to pH above highest pH at which germination occurred
147
Specific practical investigations- the effect of pH on seed germination; what choices should be made about study duration?
-Experiment should be continued until it’s clear that seeds haven’t germinated aren’t going to
-Possibility that pH could delay germination must be eliminated
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Specific practical investigations- the effect of pH on seed germination; what choices should be made about other variables that should be standardised?
-Temp; temp should be standardised, ideally at a constant temp that would occur during natural germination
-Nutrient supplies; seeds don’t need to absorb nutrients to germinate. They’d only need to be provided if plants were going to be grown beyond time at which they’d have exhausted nutrients originally present in seed
-Using soil as a growth medium replicates natural growth situation but may affect experimental condition, including pH
149
Specific practical investigations- the effect of water turbidity on light penetration; why is turbidity of water measured and how?
-Measuring turbidity of water is an important way of monitoring soil erosion
-Can be measured using a number of techniques in field/laboratory
-Secchi discs & turbidity bottles give semi-quantitative/qualitative results
-Electronic meters give quantitative data
150
Specific practical investigations- the effect of water turbidity on light penetration; what is an electronic turbidimeter and how does it measure the effect of water turbidity in light penetration?
-Most electronic turbidimeters measure amount of light that’s scattered by suspended particles in a water sample, usually at 90° to angle at which it entered water
-An increase in turbidity causes more light scatter, so light reading rises
-Light readings give relative values of concentration of suspended particles in water samples
-Quantitative estimates can be produced if a calibration curve is produced by measuring light scatter from samples w/ known amounts of suspended matter
151
Specific practical investigations- the effect of water turbidity on light penetration; which factors must be standardised when producing a calibration curve by measuring the light scatter from samples?
-Brightness of the light bulb
-Colour of light emitted by lightbulb
-Distance to sample holder
-Material used to produce calibration samples
152
Specific practical investigations- the effect of inorganic nutrients on the growth of aquatic plants/algae; why is biomass growth measured?
Increase in growth caused by availability of nutrients may cause increase in biomass as more sunlight is converted into carbohydrates
153
Specific practical investigations- the effect of inorganic nutrients on the growth of aquatic plants/algae; why is measuring biomass growth difficult and how is this best carried out?
-Living matter is mainly water, so measuring living biomass isn’t necessarily a good indicator of amount of carbohydrate present
-It’s especially difficult w/ aquatic plants where surface water will affect mass but drying it off may damage plants
-Dry biomass is a more precise measure but involves killing plants/algae so long term studies can’t be carried out on same organisms
-If increase in dry biomass is estimated on several occasions over a period of time then large number of original samples will be needed since each is destroyed when it’s weighed
-For some aquatic plants, eg duckweed (Lemna spp), leaf area can be used as a reasonable estimate of biomass & allows continued use of same plants
154
Specific practical investigations- the effect of inorganic nutrients on the growth of aquatic plants/algae; which other factors must be controlled when measuring biomass growth?
-Temperature
-Light levels
-If nutrient solutions need to be topped up, it’s best to transfer plants to new solutions rather than adding more nutrients to remaining nutrient solution which will have an unknown nutrient concentration
155
Specific practical investigations- factors affecting noise levels; how can noise levels be measured and how is this made accurate?
-W/ an electronic sound level meter but if one is unavailable many mobile phones incorporate sound level meters
-If uncalibrated meters are used then same one should be used to collect all results. This’ll ensure that degree of error in results is constant so they can be compared w/ each other
156
Specific practical investigations- factors affecting noise levels; how does distance from source affect light levels and how can this be measured?
-The fact that noise levels decline as distance from source increases is predictable
-Collecting quantitative data & assessing variations in noise levels from sources like roads & airports is more difficult
-As decibel scale is logarithmic, a simple arithmetic mean doesn’t give a true representation of typical sound levels
-Presence of sound absorbing/reflecting surfaces & topography can affect noise levels, so study sites should be as similar as possible
157
Specific practical investigations- factors affecting noise levels; how does acoustic insulation affect light levels and how can this be measured?
-May be investigated under laboratory conditions w/ a source of sound, eg a speaker, surrounded by acoustic insulation of different materials/thickness
-Effectiveness of insulation around roads/airports eg baffle mounds, embankments, walls, fences, or vegetation can be compared
158
Specific practical investigations- the effect of slope & vegetation on rain splash erosion; what are the variables that can affect rain splash erosion?
-Rainfall intensity
-Soil texture
-Soil compaction
-Organic matter content
-Soil depth
-Permeability of material beneath soil
-Precipitation rate; volume per unit area per unit of time
-Raindrop size
-Raindrop height drop
-Gradient
-Vegetation cover
-Root binding
159
Specific practical investigations- the effect of trees on microclimates; how do tree affect the local climate and why is this important?
-In & around woodlands
-Even individual trees produce microclimates
-An understanding of how these microclimates are produced & effects they have can alter management plans for urban areas & rural areas like farmland, forestry plantations & woodlands for wildlife conservation
160
Specific practical investigations- the effect of trees on microclimates; which variables should be considered when measuring the effect of trees on microclimates?
Vegetation features;
-Tree height
-Foliage characteristics
-Tree spacing
-Total area of woodland
161
Specific practical investigations- the effect of trees on microclimates; what are the features of the microclimate that can be measured?
-Wind direction
-Wind velocity
-Light levels
-Humidity
-Soil moisture
-Temperature
162
Statistical analysis; what is the variability of results?
-To increase validity of values used, it’s normal to take replicate readings & calculate a mean value
-However, this value gives no indication of how variable original results were
-2 means may have different values but range of original values in both data sets may overlap so much that it’s not possible to be confident that they’re significantly different
-Alternatively, 2 means may have been produced from data sets that hardly overlap & there’s a significant difference betw them
163
Statistical analysis; how can the degree of variability calculated?
-As the Standard Deviation
-For normally distributed results, it’s possible to estimate % of all values that are within a particular range around mean
-Where a graph is drawn using means, error bars may be added to show standard deviation. This can help to assess whether differences in mean values are statistically significant
164
Statistical analysis; what is significance and when is a result statistically significant?
-Most scientific investigations produce quantitative results that are compared to establish the significance of any differences
-Good scientific analysis never 'proves' anything as there’s always some remaining uncertainty. The key issue is the level of confidence that can be held over significance of a conclusion
-A result is statistically significant if a result is unlikely to have occurred by random chance
-The probability that result was produced by random chance can be calculated. The lower it is, the greater reliability of result
165
Statistical analysis; what is the p-value and how is it expressed?
The probability of an event being caused by random chance & is usually expressed as the probability that a single event was significant; 0.9, 0.95, 0.9, 0.995, or as a degree of confidence that difference investigated is significant
166
Statistical analysis; how is the significance interpreted?
-Showing that a result is significant doesn’t mean it’s important/that a causal relationship has been found
-Two correlated factors may both be caused by another variable that hasn’t been investigated
-P-value 0.1= 90% chance of results NOT being produced by random choice
-P-value 0.005= 99.5% chance of results NOT being produced by random choice
167
Statistical analysis- stat tests; why is the Spearman Rank Correlation Coefficient used and what does it assess?
-To see whether there’s a consistent change in the value of one variable as another variable increases/decreases
-Assesses how closely two variables are correlated by comparing rank orders of two variables in a variety of sampling situations
168
Statistical analysis- stat tests; what are examples of hypotheses that can be tested using Spearman's Rank Correlation Coefficient?
-Crop yield increases as fertiliser application increases
-Noise levels decrease as distance from a road increases
-Per capita energy use increases as per capita income increases
-Number of moths increases as temp rises
-Number of earthworms declines as soils become more acidic
169
Statistical analysis- stat tests; why and when is the Chi-squared test used?
-To compare frequencies/numbers of things in different groups are significantly different
-It can’t be used for data that can be continuously variable eg measured/calculated data
170
Statistical analysis- stat tests; what are examples of hypotheses that can be tested using the Chi-squared test?
-The different management practices in a range of woodlands affects numbers of dormice
-A range of new GM varieties of wheat produce more seeds per seed head than a traditional variety
171
Statistical analysis- stat tests; what is the T-test and when is it used?
-To see if there’s a significant difference betw 2 means, where the data were measured, eg mass, length, wind speed & dissolved oxygen concentration
-It can only be used if the data are normally distributed, which may be difficult to determine w/ small samples
-If there’s uncertainty then the Mann-Whitney U test should be used instead
172
Statistical analysis- stat tests; what are examples of hypotheses that can be tested using the t-test?
-The mean mass of lobsters is higher in areas where collection is banned
-The dissolved oxygen level is lower in a sewage-polluted river
-Wind speed is lower in a woodland than in a clearing
-Soil water content is lower on south side of a hedge than on north side
173
Statistical analysis- stat tests; why is the Mann-Whitney U test used?
To see if there’s a significant difference betw 2 median values, where the data was counted, eg numbers of organisms/vehicles, or was calculated eg diversity indices
174
Statistical analysis- stat tests; what are examples of hypotheses that can be tested using the Mann-Whitney U test used?
-Fewer cars use a road when road charging is introduced
-Biodiversity is higher in a hedge that’s trimmed less frequently
-More wading birds visit a nature reserve after water level is raised
-More bats feed over an uncut grassland than over a close-mown one
-Fewer seeds germinate at pH 5 than pH 7
