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← Theoretical A

Q41 — Octopus Active Sleep and Circadian Control

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

In Octopus laqueus, two distinct sleep stages are observed: active (AS) and quiet (QS). Active sleep is marked by active bouts, which include only specific body and eye movements along with transitions in skin patterns, occurring between periods of quiet sleep. There are potential parallels between vertebrates’ non-REM and REM (Rapid Eye Movement) sleep phases and octopuses’ QS and AS stages, respectively. Researchers measured the occurrence of active bouts in the group of octopuses during the day and night and in the interrupted conditions as seen in Figure 1.

Average number of active bouts per hour over 36 hours before and after sleep deprivation, a plot of the probability of the next active bout occurring N minutes after a normal or interrupted bout, and active bouts per hour over 3 days of constant darkness. Figure 1. A Average number of active bouts per hour over 36 hours before (Q) and after (R) 2-day sleep deprivation (darkness is depicted in gray background areas). B Probability of the next bout (Y-axis) occurring N minutes after (X-axis) a normal (S) or interrupted (T) bout. C Active bouts per hour (Y-axis) during 3 days of constant darkness (darkness is depicted in gray background areas).

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

A. Bouts are more likely to be controlled by internal circadian mechanisms than by external environmental signals.
B. On average, octopuses of this species have 8 active bouts per night.
C. The data shows that sleep deprivation in this octopus species increases the average duration of an active bout.
D. Active bouts can be replenished if they do not occur in the normal amount.
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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)