Effects of climate change and modellingEdexcel International A Level Biology: Subtopic test

1. 1
   A climate scientist has fitted a straight line to the mean global surface temperature measured each year from 1980 to 2020 and has extended the line to the year 2100 to predict future warming. Other research groups use computer models that include processes such as the melting of sea ice and the release of methane from thawing soils, and that are run with different assumptions about future greenhouse gas emissions.

   (a)

   What is meant by extrapolation when it is applied to the temperature data?

   [1 mark]

   • AExtending a trend beyond the range of the measured data, assuming the pattern continues
   • BEstimating a value between two measured data points
   • CCalculating the mean of all the measured values
   • DRemoving results that do not fit the trend

   (b)

   Which statement describes a limitation of the computer models used to predict climate change?

   [1 mark]

   • AThey cannot use any data from the past
   • BThey always predict a smaller temperature rise than the real one
   • CThey depend on assumptions about future emissions and on incomplete understanding of feedback processes, so their predictions are uncertain
   • DTheir predictions are not affected by the assumptions that are put into them

   (c)

   Suggest two reasons why extending the straight line to 2100 may give an inaccurate prediction.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Over fifty years the mean spring temperature in a temperate region has risen by 1.5 °C. Naturalists have recorded that a butterfly species now emerges from its pupae 12 days earlier than in the 1970s, that a bird species now lays its eggs earlier in the year, and that a cold-adapted alpine plant is now found on mountain slopes about 150 m higher than before.

   (a)

   Which is the most likely explanation of why the alpine plant is now found at higher altitude?

   [1 mark]

   • ASeeds are carried uphill by rainwater
   • BThe plant has acquired mutations that make it require higher altitudes
   • CPlants grow towards cooler air
   • DLower slopes have become too warm for the cold-adapted plant to survive, so it survives only where it is cooler

   (b)

   Caterpillars are the food of the nestlings of the bird species. Suppose the caterpillars now emerge much earlier in spring but the birds' egg-laying advances by less. What is the most likely consequence?

   [1 mark]

   • AThe nestlings hatch after the peak abundance of caterpillars, so less food is available and fewer chicks survive
   • BThe nestlings have more food than before and more survive
   • CThere is no effect on the birds
   • DThe caterpillars will no longer be eaten, so they evolve to emerge later

   (c)

   Suggest how a warmer spring could cause the butterfly to emerge from its pupae earlier.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A researcher measured the rate of oxygen consumption of a species of beetle larva at three temperatures, using a respirometer. The mean rate was 18 µmol O₂ g⁻¹ h⁻¹ at 15 °C, 41 µmol O₂ g⁻¹ h⁻¹ at 25 °C and 38 µmol O₂ g⁻¹ h⁻¹ at 35 °C.

   (a)

   Calculate the Q10 for the larvae between 15 °C and 25 °C.

   [3 marks]

   (b)

   Calculate the Q10 between 25 °C and 35 °C and explain why it differs from the value between 15 °C and 25 °C.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A student investigated the effect of temperature on the development of brine shrimp (Artemia). Batches of eggs were incubated in salt solution at 10 °C, 20 °C and 30 °C, and the time taken for 50% of the eggs in each batch to hatch was recorded. The times were 96 hours at 10 °C, 40 hours at 20 °C and 18 hours at 30 °C. Each batch was tested once.

   (a)

   Describe how the student should have carried out the investigation so that the results were valid and reliable.

   [6 marks]

   (b)

   Using rate = 1 ÷ time, calculate Q10 for 10–20 °C and 20–30 °C, and evaluate what the results show about the effect of temperature on development and its significance for organisms in a warming climate.

   [6 marks]

   Total for question 4: 12 marks

End of questions