An investigator studied the rate of aerobic respiration in the freshwater amphipod Gammarus pulex at different environmental temperatures using a flow-through respirometer system.
The investigator measured the rate of oxygen consumption (μl O2 g−1 h−1\mu\text{l }\text{O}_2\text{ g}^{-1}\text{ h}^{-1}μl O2 g−1 h−1) for amphipods of different body masses at three constant temperatures: 8 ∘C8\ ^\circ\text{C}8 ∘C, 13 ∘C13\ ^\circ\text{C}13 ∘C, and 18 ∘C18\ ^\circ\text{C}18 ∘C.
The results are shown in the table below:
| Body mass (mg\text{mg}mg) | Rate of oxygen consumption (μl O2 g−1 h−1\mu\text{l }\text{O}_2\text{ g}^{-1}\text{ h}^{-1}μl O2 g−1 h−1) at 8 ∘C8\ ^\circ\text{C}8 ∘C | Rate of oxygen consumption (μl O2 g−1 h−1\mu\text{l }\text{O}_2\text{ g}^{-1}\text{ h}^{-1}μl O2 g−1 h−1) at 13 ∘C13\ ^\circ\text{C}13 ∘C | Rate of oxygen consumption (μl O2 g−1 h−1\mu\text{l }\text{O}_2\text{ g}^{-1}\text{ h}^{-1}μl O2 g−1 h−1) at 18 ∘C18\ ^\circ\text{C}18 ∘C |
|---|---|---|---|
| 101010 | 120120120 | 178178178 | 258258258 |
| 202020 | 105105105 | 154154154 | 221221221 |
| 303030 | 929292 | 135135135 | 193193193 |
| 404040 | 818181 | 118118118 | 168168168 |
Suggest how the investigator could ensure that the water temperature remains stable inside the respirometer chamber during the measurements.
Explain why maintaining a constant, continuous flow of water past the animals in the respirometer is essential for ensuring the validity of the respiration measurements.
Use the formula:
Q10=(R2R1)10T2−T1 Q_{10} = \left(\frac{R_2}{R_1}\right)^{\frac{10}{T_2 - T_1}} Q10=(R1R2)T2−T110to calculate the temperature coefficient (Q10Q_{10}Q10) for respiration in the smallest group of amphipods (10 mg10\text{ mg}10 mg) between 8 ∘C8\ ^\circ\text{C}8 ∘C and 18 ∘C18\ ^\circ\text{C}18 ∘C. Show your working and give your answer to 3 significant figures.
Based on the data, evaluate the claim that increasing the temperature from 8 ∘C8\ ^\circ\text{C}8 ∘C to 18 ∘C18\ ^\circ\text{C}18 ∘C has a greater relative effect on the metabolic rate of smaller amphipods compared to larger amphipods.
