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← Theoretical A

Q40 — Circadian Misalignment in Mice

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

In a study examining the behavioral activity of mice and its dependence on feeding time, mice were kept on a 12-hour light/12-hour dark cycle. They were divided into two groups: one that was fed only during the light phase, and the other that was fed with the same diet only during the dark phase. The locomotor activity and calorie intake (Figure 1) together with the body temperature (Figure 2) were measured for mice.

Line graphs of weekly locomotor activity and caloric intake over several weeks for light-fed versus dark-fed mice, with dark-fed mice showing higher activity and calorie intake throughout. Figure 1. A – weekly locomotor activity counts, C – caloric intake in kcal, W – time in weeks, DA – dark-fed mice activity, LA – light-fed mice activity, DC – dark-fed mice calories, LC – light-fed mice calories.

Body-temperature recordings over several days for light-fed and dark-fed mice, with feeding periods marked by bars and dark phases shaded in blue, showing wider temperature swings in the light-fed group. Figure 2. Recordings of body temperature of the two mice groups fed during the light (A) for 5 days and dark (B) for 7 days phases. The feeding periods are indicated by solid bars on top of the panels. The dark phases are depicted in blue.

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

A. We can expect light-fed mice to have higher body weight than dark-fed mice.
B. Night-time feeding is an example of circadian-behavior misalignment in mice.
C. Night-time feeding altered the circadian body temperature range stronger than light-time feeding.
D. It can be concluded that the decrease in locomotor activity in light-fed mice occurs due to reduced calorie intake.
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Question reproduced from IBO 2024, Theoretical Exam Part A, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)