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
used
Reliable means that figure can be reproduced when measurement
Repeated/show little variation about true value
2
(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
2
(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...
1
(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
3
(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
2
(d) Some stomachs may contain more than one type of prey item
1

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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
2
[15]
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
[8]
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
1
(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
2
(e) (A statistical test) determines the probability of results being due
to chance
Enables null hypothesis/description of null hypothesis to be
accepted/rejected
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
increases
(Large value of ratio due to) large biomass ÷ small number/large
size ÷ small number/biomass greater than abundance
Explanation of seaweed ratio
2
(ii) 1. Fewer larger animals/more smaller animals where
more people/more disturbance
Principle
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
2
(ii) more food for insects
1
(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
nd
respired and CO released
2
used by plants in photosynthesis/ enters leaves
4 max
[15]
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
phospholipids
ATP/ADP
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
3
[20]…read more

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