Climate change, temperature and Q10 (Core practical 12)

Effects of climate change on organisms

• Distribution: species move towards the poles or uphill as their range warms; species that cannot move or adapt may become extinct locally.
• Timing of life cycles: earlier flowering, leaf burst, insect emergence, egg laying and migration. If a predator's breeding no longer matches the peak of its prey, its young may starve.
• Development: in some reptiles, such as many turtles, nest temperature determines sex, so warming changes sex ratios.
• Changes in rainfall alter plant growth, and new areas become suitable for pests and disease vectors.

Temperature, enzymes and Q10

As temperature rises, molecules gain kinetic energy and collide more often with enough energy to react, so enzyme activity increases, up to the optimum. Above it, bonds holding the tertiary structure break, the active site changes shape and the enzyme denatures.

The temperature coefficient Q10 compares rates 10 °C apart:

Q10 = rate at (t + 10) °C / rate at t °C

For many enzyme-controlled reactions between about 0 and 40 °C, Q10 is about 2: the rate roughly doubles for every 10 °C rise. Development rate in organisms that cannot control their body temperature (ectotherms) rises with temperature in a similar way.

Core practical 12

Investigate the effect of temperature on development, for example the hatching of brine shrimp eggs or the growth of seedlings.

1. Put the same number of eggs (about 40) in the same volume of salt water (for example 2 g sea salt in 100 cm³ dechlorinated water) at each temperature, such as 15, 20, 25, 30 and 35 °C.

2. After a fixed time (for example 24 hours), shine a light from the side so hatched shrimp swim towards it, then remove and count them.

3. Control salt concentration, volume, number of eggs, light and time.

Ethics: handle living organisms carefully, minimise harm, use the smallest number needed, and return or dispose of them humanely.

Worked example

An enzyme reaction has a rate of 12 units at 20 °C and 26 units at 30 °C. Calculate Q10.

1. Q10 = rate at 30 °C / rate at 20 °C
2. = 26 / 12 = 2.17

Answer: Q10 = 2.17

Check yourself

1. A reaction rate is 0.8 units at 15 °C and 1.8 units at 25 °C. Calculate Q10 to 2 decimal places.
   Show answer

   2.25. 1.8 / 0.8 = 2.25.

2. Q10 for a reaction is 2. The rate at 10 °C is 5 units. Assuming Q10 stays constant, what is the rate at 30 °C?
   Show answer

   20. Doubles from 10 to 20 °C (10 units), and again to 30 °C (20 units).

3. 28 of 40 brine shrimp eggs hatched at 25 °C. What percentage hatched?
   Show answer

   70 %. 28 / 40 x 100 = 70%.

4. How is climate change expected to affect the distribution of many species?
   • They all move towards the equator
   • Their ranges stay exactly the same
   • They move to lower altitudes in warmer regions
   • Their ranges move towards the poles or to higher altitudes
   Show answer

   Their ranges move towards the poles or to higher altitudes. Species track cooler conditions as their range warms.

5. Why can earlier spring warming harm young birds?
   • Birds cannot lay eggs in warm weather
   • Their hatching may no longer match the peak in their insect food
   • Warm weather kills all insects
   • Birds stop migrating altogether
   Show answer

   Their hatching may no longer match the peak in their insect food. A mismatch in timing leaves chicks short of food.

6. Why does enzyme activity fall above the optimum temperature?
   • Molecules have less kinetic energy
   • The substrate is used up instantly
   • The enzyme gains more active sites
   • Bonds holding the tertiary structure break and the active site changes shape
   Show answer

   Bonds holding the tertiary structure break and the active site changes shape. Denaturation changes the active site so substrates no longer fit.

7. Which is an ethical consideration in core practical 12?
   • Using as many organisms as possible
   • Using the smallest number of organisms needed and minimising harm
   • Keeping all organisms at 60 °C
   • Not counting the organisms
   Show answer

   Using the smallest number of organisms needed and minimising harm. Living organisms should be treated with care.

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Sources

• Pearson Edexcel International Advanced Level in Biology specification (XBI11/YBI11, first teaching 2018)
• Physics & Maths Tutor: Edexcel IAL Biology CP12, Temperature on the development of organisms

Last updated 7 November 2026. Spotted a mistake? Tell us.