Q44 — Bee Thermoregulation and Body-Size Scaling

Theoretical B Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license

Bees can redirect excess heat from the thorax to the abdomen, thus maintaining heat homeostasis. Figure 1A shows body temperature differences due to various outside temperatures for a bee with a large body mass. Figures 1B and 1C show how body mass influences other parameters. Figure 1D shows how thorax temperature affects mass-specific metabolic rate. mut99-bees carry a mutation that impairs both effective thorax cooling and abdomen warming. All graphs below show data for wild-type bees without any mutation.

Figure 1. A Body temperature vs. air temperature for a large bee; X — thorax, Y — abdomen, W — dashed unity line (body temperature = air temperature). B Temperature difference between body and air vs. log body mass, for head, thorax, and abdomen. C Log wing-beat frequency and log total wing area vs. log body mass. D Mass-specific metabolic rate (Watt/mg) vs. thorax temperature.

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. The smaller the bee, the lesser the mut99 mutation impact on heat homeostasis.

B. Abdomen temperature for large-sized mut99-bee would likely follow the line W in figure 1-A.

C. Mut99-bee during intensive flight can attain an even higher metabolic rate in the thorax than a normal bee.

D. Smaller bees lose more heat due to a higher surface-to-volume ratio, thus they compensate for it by a higher frequency of wing beat.

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Question reproduced from IBO 2024, Theoretical Exam Part B, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF