1150 species of lizard on Caribbean islands evolved from 2 species on Mainland USA
Explain how Caribbean species could have evolved (6 marks)
Geographical isolation
Separate gene pools
Variation due to mutation
Different selection pressures
Selected organisms reproduce
Causes change in allele frequency
2Describe how you could use mark-release-recapture to estimate no. of lizards (3 marks)
Capture, mark and release
Method of marking doesn't harm lizard
Leave time for lizards to distribute before 2nd sample
3Determine mean % cover for beach grass on a sand dune
Use a random no. generator to determine position of quadrats
Large no. of quadrats
Divide total % by no. of quadrats
4Explain advantage of showing data using SD rather than ranges (3 marks)
SD is spread of data around the mean
Reduces affect of anomalies
Can be used to determine if significance is due to chance
5Suggest appropriate units for gross productivity of a woodland (1 mark)
Grams, per area, per year
6Explain why CO2 uptake is a measure of net productivity (1 mark)
NP = photosynthesis - respiration
7Student wants to test her results with ones she expected. Which stats test and why? (2 marks)
Chi squared
Categorical data
8Suggest one suitable method for sterilising bottles (1 mark)
Wash in disinfectant
9Explain why an increase in shoot biomass can be taken as a measurement of net primary productivity (2 marks)
Represents dry mass of carbon
NPP = GPP - R
10P value of 0.047. Is difference signicant?
Yes
Probability of difference being due to chance is less than 5%
11What is an advantage of having a high NPP:GPP? (2 marks)
Low respiration
More growth / biomass
12Suggest why soils that are anaerobic have higher concentrations of ammonium compounds and low conc of nitrite ions and nitrate ions (4 marks)
Less nitrification/nitrifying bacteria require O2
Less conversion of ammonium ions to nitrite and to nitrate
More denitrification
More nitrate converted to nitrogen
13Describe how you would use results from a 'water potential of potato' practical to find the water potential of the potato (3 marks)
X axis = conc.
Y axis = percentage / ratio / etc. change in mass
Find conc. where change is 0
Use another resource to find water potential of conc.
14Explain how taking additional readings at different conc. could improve the graph for water potential of a potato (2 marks)
Curve of best fit more reliable
Point where line crosses x axis more reliable
15Explain why increased cardiac output is an advantage during exercise (4 marks)
More aerobic resp
Higher cardiac output increases O2 supply
Increases glucose supply
Increases CO2 removal