With reference to an example, define what is meant by a circadian rhythm
[3 marks]
Circadian rhythm is a type of biological rhythm consisting of a 24-hour cycle which
regulates sleep/wake cycle. Internal body clocks (endogenous pacemakers) as
well as external changes to the environment (exogenous zeitgebers)
Describe one study that investigated a circadian rhythm. [4 marks]
One study that investigated a circadian rhythm is conducted by Michael Siffre, who was a self-taught
caveman that used to stay underground for long periods in order to study the effects of his own
biological rhythms. He stayed underground for around 2 months, with a lack of sunlight and sound
but enough food and drink. A decade later he performed a similar study, this time 6 months in a
Texas cave. In each case, his ‘free-running’ biological rhythm settled down to one that was beyond
usual 24 hours- 25 instead, although he woke up and fell asleep on a regular schedule
[3 marks]
Circadian rhythm is a type of biological rhythm consisting of a 24-hour cycle which
regulates sleep/wake cycle. Internal body clocks (endogenous pacemakers) as
well as external changes to the environment (exogenous zeitgebers)
Describe one study that investigated a circadian rhythm. [4 marks]
One study that investigated a circadian rhythm is conducted by Michael Siffre, who was a self-taught
caveman that used to stay underground for long periods in order to study the effects of his own
biological rhythms. He stayed underground for around 2 months, with a lack of sunlight and sound
but enough food and drink. A decade later he performed a similar study, this time 6 months in a
Texas cave. In each case, his ‘free-running’ biological rhythm settled down to one that was beyond
usual 24 hours- 25 instead, although he woke up and fell asleep on a regular schedule
