Description

From mammals to bacteria to plants, most organisms, have a circadian clock, a set of proteins whose expression oscillates with an endogenous rhythm of about 24 hours. The circadian clock regulates the daily timing of a wide variety of ecologically important processes including mammal sleep-wake pattern, millipede locomotion, Midshipman fish song, and Petunia scent release (Fenske and Imaizumi 2016, McCallum, 2017, Yerushalmi and Green 2009). The circadian system is also used by many organisms for measuring photoperiod length to regulate annual events, such as flowering in plants and long-distance migration in birds (Helm and Lincoln  2017, Song et al. 2015).

The current hypothesis for the evolution of the circadian clock is that it increases fitness by allowing organisms to anticipate cyclic external environmental changes and prepare accordingly. Organisms who have their circadian rhythm disrupted by the environment (e.g., light pollution by artificial light at night) or genetic mutations in clock genes can suffer decreased fitness (Dominoni et al. 2016).

Sleep is a defining trait of mammalian life. Although our impact on the physical and social environment is the result of actions while we are awake, wakefulness is not possible without sleep. As busy humans, we all struggle to get enough sleep and are aware of how much we need it to function optimally (Czeisler 2013).

In this lab students will generate and test a hypothesis and about the how a circadian rhythm, the sleep-wake cycle, influences an important mammalian adaptation, the ability to learn, in the model organism Homo sapiens. They will use data collected from Introductory Biology students who wore watches that measured their sleep-wake cycle for two weeks before a course mid-term. Students can use various sleep variables and Exam score to test their hypotheses.

Czeisler CA. 2013. Perspective: Casting light on sleep deficiency. Nature. 497(7450):S13.

Dominoni, D. M., Borniger, J. C., & Nelson, R. J. (2016). Light at night, clocks and health: from humans to wild organisms. Biology Letters, 12(2), 20160015.

Fenske, M. P., and Imaizumi, T. (2016)"Circadian Rhythms in Floral Scent Emission." Frontiers in plant science 7.

Helm, Barbara, and Gerald A. Lincoln. "Circannual Rhythms Anticipate the Earth’s Annual Periodicity." Biological Timekeeping: Clocks, Rhythms and Behaviour. Springer India, 2017. 545-569.

McCallum, E. "Singing fish take their cues from melatonin." Journal of Experimental Biology 220.3 (2017): 333-333.

Song, Y. H., et al. "Photoperiodic flowering: time measurement mechanisms in leaves." Annual review of plant biology 66 (2015): 441-464.

Yerushalmi, S, and Green, R. M. "Evidence for the adaptive significance of circadian rhythms." Ecology letters 12.9 (2009): 970-981.

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