Pearson Edexcel International A Level Biology: Climate Change, Evolution, Speciation and Sustainable Resources (YBI11) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover statements 5.16 to 5.26 of the Pearson Edexcel International Advanced Subsidiary/Advanced Level Biology specification (YBI11), Issue 2, including Core Practical 12. Topic 5 is International A2 (IA2) and there are no tiers. Learn the content from the study guide and revision notes first. The course hub and checklist show the wider course.

Questions

1. Explain how pollen from a peat bog and rings in a tree trunk can each provide evidence of past climate. [4]

2. A botanist records the mean spring temperature and the day of the year of first flowering of a plant in five periods.

Mean spring temperature (°C)	6.1	6.8	7.4	8.0	8.6
First flowering (day of year)	118	112	109	101	98

(a) Describe the relationship shown. [2] (b) The correlation coefficient is −0.99. Explain why this does not on its own prove that temperature causes the change. [2]

3. Explain how greenhouse gases cause the greenhouse effect. [4]

4. Using your knowledge of the carbon cycle, explain two ways of reducing the concentration of carbon dioxide in the atmosphere. [4]

5. The atmospheric carbon dioxide concentration was 338 ppm in 1980 and 370 ppm in 2000 (data supplied).

(a) Calculate the mean rate of increase per year. [1] (b) Extrapolate to predict the concentration in 2030. [2] (c) Give two reasons why climate models limit the reliability of such a prediction. [2]

6. Oxygen uptake by a lizard was measured (data supplied).

Temperature (°C)	14	18	26	28
Oxygen uptake (cm³ per g per hour)	1.8	0.32	4.5	0.72

The values at 18 °C and 28 °C come from one experiment. The values at 14 °C and 26 °C come from another.

(a) Calculate Q₁₀ from the 18 °C and 28 °C values. [2] (b) Calculate Q₁₀ from the 14 °C and 26 °C values, to 2 significant figures. [2] (c) Explain why the rate would fall if the lizard’s body temperature reached 45 °C. [2]

7. A student investigated brine shrimp hatching. Fifty eggs were placed in each of three tubes at each temperature. The numbers hatched after 24 hours were:

Temperature (°C)	15	25	35	40
Tube 1	8	26	37	5
Tube 2	10	28	38	7
Tube 3	9	27	39	6

(a) Calculate the mean number hatched at each temperature, and the percentage hatched at 15 °C. [2] (b) Describe and explain the trend. [3] (c) Calculate Q₁₀ for 15 °C to 25 °C using the means. [1] (d) Suggest one control variable and one ethical precaution. [2]

8. In a beetle population, a pesticide-resistance allele was present as 36 copies among 600 alleles in generation 1 and 117 copies among 650 alleles in generation 8.

(a) Calculate the allele frequency in each generation. [2] (b) Explain how mutation and natural selection could account for the change. [4]

9. A species of snail lived on both sides of a valley. A river then changed course and divided the population.

(a) Explain how this could lead to the formation of two species. [4] (b) Describe how speciation could occur without a geographical barrier. [2]

10. A report concluded that human activity has little effect on climate. It was paid for by a coal company. Suggest two reasons for caution and two checks you would make. [4]

11. A reforestation scheme plants 250 ha. The trees store 8.0 tonnes of carbon per hectare per year (data supplied).

(a) Calculate the mass of carbon dioxide that this represents each year, to 3 significant figures. [3] (b) Evaluate reforestation and biofuel crops as ways to balance human needs and conservation. [4]

Answers

1. Pollen: peat is waterlogged and acidic, so pollen is preserved in layers [1]; the species present at each depth show the plants, and so the climate, at that time [1]. Tree rings: one ring is added each year [1]; wide rings indicate favourable (warm, wet) years and narrow rings poor years [1] [4] Examiner insight: “Explain” needs a link from the record to the climate, so state what the pollen or ring shows and what it means.

2. (a) As temperature rises, the day of first flowering is earlier [1], from day 118 at 6.1 °C to day 98 at 8.6 °C, a negative correlation [1] (b) A correlation only shows the two variables rise and fall together, which does not establish cause [1]; another factor (such as rainfall or day length) could change over the same periods, and a mechanism is needed [1] [4] Examiner insight: Quote values from the table in (a), and name a possible confounding factor in (b); “it is not proven” alone earns little.

3. Incoming sunlight, mostly short-wavelength, reaches the surface and warms it [1]; the warmed surface emits longer-wavelength infrared [1]; greenhouse gases such as carbon dioxide and methane absorb it [1] and re-emit some towards the surface, so less heat escapes to space and the surface warms [1] [4] Examiner insight: Name the type of radiation at each stage; “traps heat” is too vague to show the mechanism.

4. Reforestation (or protecting forests): photosynthesis removes carbon dioxide, which is stored as organic carbon in wood [1], so less remains in the atmosphere [1]. Burning less fossil fuel (or capturing carbon dioxide from power stations): fossil fuels release carbon that was stored for millions of years [1], so avoiding combustion cuts input to the atmosphere [1] [4] Examiner insight: Each method needs its cycle process, such as photosynthesis or combustion, to earn the explaining mark.

5. (a) (370 − 338) ÷ 20 = 1.6 ppm per year [1] (b) 370 + 1.6 × 30 [1] = 418 ppm [1] (c) Models depend on assumptions about future emissions [1]; many interacting variables and feedback loops, so the rate may change [1] [5] Examiner insight: Show the working in (b) and check the number of years from the last measured date, so the method is visible.

6. (a) The interval is 10 °C, so Q₁₀ = 0.72 ÷ 0.32 [1] = 2.25 (about 2.3) [1] (b) The interval is 12 °C: (4.5 ÷ 1.8)^(10/12) [1] = 2.1 [1] (c) High temperature breaks hydrogen bonds, changing the tertiary structure and active site [1]; enzymes denature, so substrates no longer fit and the rate falls [1] [6] Examiner insight: Q₁₀ is a ratio with no units; using 10 ÷ 12 as the power is the usual step to show for a non-10 °C interval.

7. (a) Means 9, 27, 38 and 6 [1]; at 15 °C, 9 ÷ 50 × 100 = 18% [1] (b) Hatching rises from 15 to 35 °C [1] because greater kinetic energy gives more enzyme-substrate collisions [1]; at 40 °C it falls because enzymes denature [1] (c) 27 ÷ 9 = 3.0 [1] (d) Control: egg number, salinity, volume, light, or time [1]; ethical: use the minimum number of eggs, and dispose of nauplii humanely [1] [8] Examiner insight: A control variable must be something you keep the same; naming “temperature” does not gain credit.

8. (a) 36 ÷ 600 = 0.06 [1]; 117 ÷ 650 = 0.18 [1] (b) A random mutation produced the resistance allele [1]; the pesticide is a selection pressure, so resistant beetles survive [1]; they reproduce more and pass on the allele [1]; so its frequency rises across generations [1] [6] Examiner insight: Say that the mutation occurred before the pesticide; marks are lost for implying beetles mutate to cope.

9. (a) The river is a geographical barrier that stops gene flow [1]; the two populations experience different mutations and selection pressures [1]; allele frequencies diverge [1]; eventually they cannot interbreed to produce fertile offspring, so they are separate species [1] (b) Sympatric speciation: reproductive isolation within the same area [1], for example flowering at different times, a new food source, or polyploidy in plants [1] [6] Examiner insight: The end point matters: a good answer states that interbreeding no longer gives fertile offspring.

10. Caution: the funder has a financial interest, so data may be selected [1]; values and interests can shape the conclusion [1]. Checks: whether the report was peer reviewed and results replicated [1]; the data, sample size and period, and whether the conclusion goes beyond them [1] [4] Examiner insight: Point to who gains from the result; do not say it must be wrong.

11. (a) 250 × 8.0 = 2,000 tonnes of carbon [1]; × 44 ÷ 12 [1]; 7,330 tonnes of carbon dioxide per year [1] (b) Reforestation restores habitat, stores carbon and reduces erosion [1], but young trees store little at first and monoculture supports less biodiversity [1]. Biofuel crops give fuel that is nearly carbon neutral [1], but they compete with food or forest, and fertiliser and machinery use energy [1] [7] Examiner insight: An “evaluate” answer needs benefit and drawback for each option.

Where marks are usually lost

• Writing that a correlation proves a cause, or dismissing it without a mechanism.
• Saying “traps heat” without absorption and re-emission of infrared.
• Forgetting the exponent when the temperature interval is not 10 °C.
• Giving a unit with Q₁₀.
• Naming the independent variable as a control variable.
• Missing ethical precautions in Core Practical 12 answers.
• Saying mutations happen because an organism needs them.
• Describing speciation without isolation and without loss of fertile interbreeding.
• Calling biofuels carbon neutral with no limitation.

Next steps

• Review the revision notes and the study guide.
• Visit the course hub and the checklist.
• Take one of the free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

Pearson Edexcel International Advanced Subsidiary/Advanced Level in Biology (YBI11), Specification, Issue 2, February 2021, Topic 5, statements 5.16 to 5.26, published by Pearson Education Limited.