Q13 - Lethal Temperature in Homeotherms
Cold-blooded (poikilothermic) animals are able to tolerate significant fluctuations in body temperature (by several tens of degrees) without negative consequences. In contrast, some warm-blooded (homoiothermic) animals cannot survive a small change in body temperature (see Table).
| Group of animals | Normal core body temperature (°C) | Lethal core body temperature (°C) |
|---|---|---|
| Monotremata (Echidna) | 30–31 | 37 |
| Marsupials | 35–36 | 40–41 |
| Insectivores (Hedgehog) | 34–36 | 41 |
| Human | 37 | 43 |
| Most placental mammals | 36–38 | 42–44 |
| Birds (Kiwi) | 38 | 44 |
| Birds (except Passerines) | 39–40 | 46 |
True or False?
What is/are the main reason(s) warm-blooded animals are intolerant to changes in body temperature? State whether the following statements are true or false.
Q13.1. For Passerine birds (body temperature is 40-41 degrees C) lethal core body temperature will be about 47 degrees C.
Q13.2. Thermal denaturation of the majority of enzymes and other proteins with increasing temperature.
Q13.3. Thermal denaturation (melting) of DNA with increasing temperature.
Q13.4. Changes in the microviscosity of lipids of cellular and intracellular membranes with increasing temperature.
Q13.5. Different temperature sensitivity (Q10-coefficient) of biochemical reactions in cells.
Question reproduced from IBO 2023, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF