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81 Cards in this Set
- Front
- Back
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State your null hypothesis for an experiment measuring number of bubbles counted against distance of light from plant
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No correlation/relationship between light intensity and rate of photosynthesis
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For the no. of bubbles/plant/lightbulb at diff distances experiment, why would you use spearman rank
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Testing correlation between MEASUREMENTS OF rate of photosynthesis at different light intensities
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Explain why the rate of bubbling can be used as the rate of photosynthesis
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Bubbles contain oxygen/oxygen is a product of photosynthesis
higher rate of photosynthesis = more bubbles released |
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Suggest one way to reduce temp rises during bubbles/light intensity experiment
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Use water filled transparent container
LED lamp |
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State the purpose of sodium hydrogencarbonate in plant experiments
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Provides CO2 for photosynthesis
So CO2 not limiting |
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Why would you leave a plant at a particular light intensity for 5 minutes before measuring rate of photosynthesis
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Time for rate to adjust to new light intensity
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2 assumptions if rate of bubbling is used as rate of photosynthesis
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Bubbles are the same size
Bubbles are oxygen Rate of resp constant |
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Why would you need to monitor the number of hours of sunshine in a photosynthesis experiment?
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Can't control it so have to monitor it
To see if there was a difference in number of hours of sunshine -- can eliminate as a factor affecting dependent variable Number of hours of sunshine affects length of time for which photosynthesis can occur |
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Aside from temp, fertiliser and pest control + light intensity, what factors need to be controlled in a greenhouse and why
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Density of planting; competition for light/mineral ions
Water application; water needed for photosynthesis/needed for expansion/to maintain turgidity |
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Why do farmers need to monitor the population of a pest?
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Whether or not to introduce control
How much biological control Monitor effectiveness of control Threshold beyond which there is severe damage |
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Whats the disadvantage of biological control?
Advantage? |
Not immediate control
Some pest not eliminated (may itself become a pest) (Specific) (Cant become resistant) (reproduces itself) |
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If designing an investigation to see a populations affinity for diff traps, what factors need to be taken into account
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Size/surface area of trap
Climatic condition length of time for which traps left out Large number of traps Statistical test for significance |
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Why would you stopper a flask? |
Prevent contamination by bacteria bacteria would compete for oxygen |
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When do you use the chi squared test? |
Variable being measured (e.g number of green and yellow balls) is categoric |
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Why do you use cotton wool as a stopper? |
Allow oxygen/CO2/PERMEABLE to gas |
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How does oxygen increase growth? |
More anaerobic resp greater release of energy more energy for growth/cell division |
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Describe how they could find out whether this correlation was significant. |
Produce null hypothesis use spearman rank test to calculate coefficent find probability results are due to chance |
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Experiment W was a control experiment. Explain the purpose of the controlexperiment in this investigation. |
shows mass of seedlings when on their own; allows comparison/allows effect of competition to be seen |
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One disadvantage of growing only one type of wheat |
Less genetic diversity cant adapt to changing conditions |
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What factors determine the size of your sample? |
Large enough to be representative/prodcue a reliable mean/for statistical test Not so many that insufficient time/too few repeats |
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If 15 maggots turn 1 direction and 1 maggot turns in the other direction, is the movement of that one maggot an anomaly? |
Can be explained by natural variation/chance |
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What is a taxis |
Directional response to a stimulus |
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Why would you control light in maggot investigation? |
Reduce light as a variable, ensure light is uniform |
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The woodlice were left for 15 minutes at a particular humidity. Why? |
Allow humidity to be established allow acclimitisation - behaviour typical of light intensity |
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Why is it not possible to conclude a causal link between two variables that correlate? |
correlation does not show causation may be another factor |
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Why might all the points on a humidity versus movement of woodlouse graph fall on the line? |
Line of best fit variation in movemnt of woodlice due to age/species change in environment over time |
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How do you phrase the null hypothesis for a chi squared test? |
No difference in the frequency in which X |
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When do you use chi squared? |
Categorical/frequency data (direction is categorical variable) |
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Why can't you conclude things? |
Too few repeats no statistical test low sample size |
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What does subjectivity reduce? |
Reliability |
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How do you measure dry mass? |
Heat to 100 degrees weight and heat until constant masss |
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Why do you have to use dry mass? |
Water can vary this affects fresh mass but not dry mass |
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What is meant by bias? |
Selector influences/makes conscious choice/not random |
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What does the standard deviation show? |
Spread of the data |
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What does a large standard deviation indicate? |
Lots of variation In the variable |
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How do you use quadrats? |
Place at intervals along transect count frequency per metre squared |
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Explain why it is essential to control variables? |
Only the independent variable affects the dependent variable |
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How long should you count things for? |
Long enough to minimise effect of miscounting short enough to maintain accurate countring short enough to allow sufficient repeats |
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How many repeat counts should you do? |
Enough for statistical test enough for more representative/more reliable mean limited by time reduce effect of anomalies |
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If you show that there is no overlap, what should you say? |
Ranges around the mean |
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Why do you control a variable? |
It affects whats being measured IN A PARTICULAR WAY hence to ensure only independent affects dependent and nothing else |
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Is it valid to only test one animal? |
No: diff animals behave in diff ways; internal environment changes with time; repeats for one animal not comparable to another; investigation is general Yes: one has less variation more likely to see a diff response |
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Why do you have to clean a petri dish used for maggots for each new maggot? |
May leave scent that influence behaviour |
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How do you know if data supports a trend? |
Shows trend BUT if variation may be due to chance |
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Describe briefly how you would use a statistical test to find whether there is asignificant correlation between mean March temperature and the date whenchaffinches laid their first egg. |
Null hypothesis spearman rank look up in table accept or reject |
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Explain why a large number of traps was used |
Represenattive sample/minimise effect of anomalies |
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Explain why samples were selected at random? |
Avoid bias, allow statistical analysis |
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Why would you allow yeast to settle for 5 minutes befor edoing experiment? |
Allow time to reproduce |
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Why is it important to get quadrats from lots of diff areas? |
Biotic/abiotic factors diff in diff parts of the field |
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What is phenotype? |
How genes/alleles are expressed/physical appearance |
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Give one reason why it was not necessary to match the subjects in this investigation |
Everbody has these characteristics/age + gender + ethnicity have no effect on characteristics |
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Why do you need to control: age gender ethnicity |
age: diff stage of growth females have diff hormonal effects/smaller ethinicities have diff body shape/size |
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When do you use a scatter diagramn? |
see if there is a correlation Both variables are continous |
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How can you conclude that something is not caused by a single gene? |
Not categoric distribution no dominant/recessive form normal distribution continous variation |
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What is the advantage of recording data from island people? |
Can record all individuals low sampling error diff rates of mutation/diff selection more likely to be inbreeding little gene flow |
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Health Authorities often make use of estimates of the frequency of harmful alleles.Suggest and explain one advantage to Health Authorities of using these estimates. |
Have an idea of number of people that have disease/know if number of carriers has changed medical facilities in place |
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Nutritional information is shown per 100 g. Explain one advantage to the shopper ofshowing information in this way |
Calculate intake of protein/fat per day comparison between nutritional values/protein content of diff foods calculate energy intake per day control intake of something |
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Explain why a method of measuring something might not be accurate? |
Subjective so not reliable gives values as a range/not quantitiave so not PRECISE only records above a certain value |
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Why is it better to have a more sensitive medical test? |
Early detection leads to early treatment less damage to body |
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How do you randomly select plots? |
Use tape measures to divide into agrid use calculator to generate random numbers use as coordinates |
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What is integrated pest control? |
Controlling (not eradicating) pest population using biological and chemical means |
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What is a kinesis? |
A non directional response to a stimulus changed rate of movement/turning to remain in a more favourable environment |
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What factors disprove a correlation? |
No stastical test don't know if correlation is significant |
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Why is it important that you read the instructions with each repeat? |
Standardaised method so can compare |
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What determines if somjething is a reflex? |
It is automatic/not learned just involves the spinal cord prevents damage |
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How does the body reduce heat loss from the skin when immersed in water? |
Receptors hypothalamus/autonomic nervous system nerve impulses walls of arterioles contract vasoconstriction |
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Why do you need to match ethinicity? |
Same gentic make up/similar alleles |
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Why is it better to measure leaves while they are still attached to a plant? |
Not drying out ethical ecosystem not damaged |
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What does the standard error tell you? |
True mean is found within confidence limits |
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Why does a high standard error tell you? |
More varaition less confidence in the calculated mean being the true mean |
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Why cant you use mark release recapture on a human population? |
No random mixing not a closed pop/immigration and emigration births and deaths cant mark humans not an equal chance of capture |
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Give one assumption about the animals caught that is made in both methods (mark release recapture and proportional sampling) |
animals from the same pop |
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Give one advantage of showing numbers in a population pyramid? |
Can determine population size/used for futre planning |
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How can you tell if a population is getting smaller? |
Narrower base than above/lower birth rate |
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If you have a contracting age pyramid, and you know that age is a risk factor for alzheimers, can you say that alzheimers will rise? |
NO: might not reach old age cure might be found contracting pyramid may be short-term YES: middle aged become elderly life expectancy increases so risk increases |
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How does ventilation maintain conc gradient? |
Bring in air with higher oxygen conc remove air with lower oxygen conc |
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Two variables correlate. Why doesnt one cause the other? |
Correlation not causation another factor causes a rise in both |
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How does using more results improve reliability of a graph? |
Line of best fit more reliable intercept more reliable can plot error bars see significance |
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Why does decreased temp decrease growth in plants (based on photosynthesis)? |
Less enzyme activity less photosynthesis less biological molecules/organic substances less respiration less energy for growth/mitosis |
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How is a hypothesis developed? |
Look at other research see an effect assumed one causes the other |
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Why is skin temp not an accurate reflection? |
Fluctuates mroe more affected by environment |
