Ecological Techniques and Statistics Answers

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  • Created on: 02-04-16 11:11
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Ecological techniques and statistics questions Mark Scheme
M1. (a) (i) Accurate means without error/free from mistakes when callipers
Reliable means that figure can be reproduced when measurement
Repeated/show little variation about true value
(ii) If data unreliable, there will be a wide range of values
Large standard deviation
The higher the figure on the top line of the equation, the greater
The percentage measurement error
2 max
(b) (i) Plot graph of mean skull breadth against mean cranial volume/
scatter diagram
Draw line of best fit / calculate coefficient of correlation
Look for figures close to +1 or ­1
(ii) Skull breadth is a linear measurements/can be measured with a
single measurement/less prone to error/Cranial volume more
difficult to measure because...
(iii) Could distinguish between large male polecats and small
female ferrets
Little overlap in standard deviations
Mean measurements for female polecats and male ferrets
are very similar
(c) Scientists could use method suggested/protocol established in
earlier paper (thus saving time)
Findings more likely to be reliable if they replicate the findings of others
(d) Some stomachs may contain more than one type of prey item

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Unidentified bird remains small percentage of total prey/found
in few stomachs
Significant numbers of rabbits/rats eaten and these are pests
M2. (a) (i) Method of positioning quadrats,
E.g. Find direction and distance from specified point/find
coordinates on a grid/split area into squares
Method of generating random numbers
E.g.…read more

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Negative correlation/the higher the temperature the fewer daffodils
in flower
All statistically significant so not likely to be/not due to chance
2 max
M3.…read more

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One mark for a valid explanation based on individual shrews
entering more than one hair tube/many hairs from same
shrew/shrews enter without leaving hair
(ii) Rules out differences due to changes in population/changes
in environmental conditions
That could be produced by births/deaths/migration/specific
example of environmental conditions affects results
(e) (A statistical test) determines the probability of results being due
to chance
Enables null hypothesis/description of null hypothesis to be
Determines whether correlation/result is significant
2 max
(f) (i) (Curve/line of best fit…read more

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There was a probability of less than 0.…read more

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The site/site U with most people/34.6 has the largest ratio/3.24
Accept: as number of people increases, ratio
(Large value of ratio due to) large biomass ÷ small number/large
size ÷ small number/biomass greater than abundance
Explanation of seaweed ratio
(ii) 1. Fewer larger animals/more smaller animals where
more people/more disturbance
2. 0.09 linked to 34.6/appropriate link between row 4 and row 1:
Use of data
3. Larger animals affected by human activity
Accept: converse
4.…read more

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Results unlikely to be due to chance/ have a biological cause
P < 0.1% / < 5%
2 max
(c) (i) biomass respired/ GPP ­ respiration = NPP
biomass lost as CO 2
(ii) more food for insects
(iii) decomposers/ saprotrophs
release enzymes and digest detritus/
substances found in detritus/ eq.
absorb products of digestion/ suitable e.g. that relates to
candidates 2 point
respired and CO released
used by plants in photosynthesis/ enters leaves
4 max
M6.…read more

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The key points here are chance and probability used in the
correct context.…read more

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DNA / RNA / nucleotides
2 max
(iii) arsenictolerant plants would not be able to take up phosphates /
take up a little phosphate
since likely to involve same mechanism/same carrier/protein
(process of ) growth would be poorer than nontolerant plants
[20]…read more


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