BioEd Online

Teacher Background

Cycles and rhythms can be found in all organisms on Earth. Many are synchronized to the 24-hour cycle of Earth’s rotation about its axis. In general, 24-hour cycles are called circadian, from the Latin words for “about” (circa) and “day” (dies).

People’s schedule of sleeping and waking is determined, to a large extent, by an “internal clock” in our brains. Environmental cues, particularly light, keep this clock synchronized to external conditions. However, the clock will continue to run on approximate 24-hour cycles, even without changes in the environment.

The human cycle of sleeping and waking can be disrupted by changes in external conditions. Such changes occur when travelers move across time zones, or when astronauts travel in space. Not getting enough sleep can contribute to poor performance on mental or physical tasks, and may even lead to dangerous accidents.

Space life scientists are seeking ways to help astronauts achieve the sleep they need to function well under the stresses of long-term space flight. Their research also will help to solve sleep-related problems for people on Earth.

Objectives and Standards

Not applicable for assessment.

Materials and Setup

Materials per Student

• Writing paper

• Markers, pencils

• Copy of student sheet (see Lesson pdf)

Setup

1. Conduct discussion with the entire class.

2. Have students work independently or in small groups to write their poems.

Procedure and Extensions

1. Review the major concepts to which students were exposed in this unit.

2. Read or have students read the poem, “Tick-Tock, Tick-Tock.” Lead a class discussion about the poem’s key concepts.

3. Have students create their own illustrated poems about sleep and/or circadian rhythms. Each poem should include at least one new concept that students learned about this topic from the activities in this unit. Possible approaches are given below.

• After the poem is read, have students write their own poems about sleep and/or circadian clocks.

• Read a few verses of the poem to get students started, and then have them write their own verses to complete the poem.

• Share the first line of each verse and have students complete the verses with their own words.

Handouts and Downloads

Download color images from The Science of Sleep and Daily Rhythms Teacher's Guide.