Effects of climate change and predictionsEdexcel A-Level Biology A: Mind map

Exam questions on Effects of climate change and predictions

1. A student investigates the effect of temperature on the activity of catalase in a suspension of liver tissue. She keeps the pH constant using a buffer, mixes the enzyme with hydrogen peroxide at each temperature and measures the initial rate of oxygen production. At 20 °C the initial rate was 0.012 cm³ s⁻¹ and at 30 °C it was 0.030 cm³ s⁻¹. At 60 °C no oxygen was produced.
   Explain why the student measured the initial rate of the reaction rather than the rate after several minutes.2 marks
2. In a woodland in the Netherlands, great tits time their breeding so that the chicks hatch when winter moth caterpillars are most abundant, because the chicks are fed mainly on caterpillars. Over 25 years the mean spring temperature has risen. The caterpillars now hatch from their eggs 14 days earlier than they did 25 years ago, whereas the date on which great tits lay their eggs has advanced by only 4 days.
   Predict, and explain, the effect of this change on the size of the great tit population.2 marks
3. A student investigates the effect of temperature on the development of brine shrimp. At each temperature she places 100 eggs in salt water of the same concentration in a thermostatically controlled water bath and counts the newly hatched shrimp every hour. Her results for the mean rate of hatching are: 15 °C, 0.5 % of eggs per hour; 20 °C, 0.9 % per hour; 25 °C, 1.6 % per hour; 30 °C, 1.3 % per hour.
   Describe how the student should set up the investigation so that her results are valid.3 marks