The question
Name: ______________________ Date: ____________ Oxygen use of a mouse and a lizard across temperatures (9 points)
Data table
Oxygen consumption of a mouse and a lizard at different air temperatures
Researchers measured the rate of oxygen consumption of six deer mice (an endotherm) and six fence lizards (an ectotherm), each with a body mass of about 20 g. Each animal was fasted for 6 hours and then rested alone in a sealed chamber kept at one air temperature for 1 hour while O₂ use was measured. Each animal was tested at all seven temperatures, in random order, on different days.
| Air temperature (°C) | Mouse | Lizard |
|---|---|---|
| 5 | 7.2 ± 0.6 | 0.05 ± 0.02 |
| 10 | 6.3 ± 0.5 | 0.08 ± 0.02 |
| 15 | 5.4 ± 0.5 | 0.12 ± 0.03 |
| 20 | 4.4 ± 0.4 | 0.19 ± 0.04 |
| 25 | 3.5 ± 0.3 | 0.30 ± 0.05 |
| 30 | 2.6 ± 0.3 | 0.45 ± 0.06 |
| 35 | 2.5 ± 0.3 | 0.68 ± 0.08 |
(a) Describe how an endotherm such as the mouse keeps its body temperature nearly constant when the air around it cools. [1 point]
(b) (i) Identify the independent variable in the experiment.
(ii) Justify fasting each animal for 6 hours before it was measured.
(iii) State the null hypothesis for comparing the mouse's rate of O₂ consumption at 30 °C and at 35 °C. [3 points](c) (i) Calculate how many times greater the mouse's rate of O₂ consumption is than the lizard's at 20 °C. Show your work.
(ii) Using the error bars (± 2 SE), determine whether the mouse's rate of O₂ consumption differs between 30 °C and 35 °C, and justify your answer. [2 points](d) (i) Explain why the mouse's rate of O₂ consumption rises as the air temperature falls from 30 °C to 5 °C.
(ii) Explain why the lizard's rate of O₂ consumption rises as the air temperature rises.
(iii) Both animals live where the air is about 10 °C. Predict which animal must eat more food per gram of body mass each day to keep its body mass steady, and about how many times more, and justify your prediction using the data. [3 points]