Actograms What is an actogram Acto activity Actograms

Actograms

What is an actogram? • Acto = activity • Actograms are visual representations of an animals activity (activity record). • An animals activity on an actogram is said to be ‘free-running’ – the length of time an organism’s biological clock runs for in the absence of environmental cues. • If an animals behaviour continues independently of its external environment, it proves the behaviour is endogenous (has an internal origin). • These rhythms are controlled by an internal pacemaker (oscillator).

• Free-running, endogenous rhythms aren’t synchronised with the environment, which means the internal clock must be re-set, or entrained. • Under normal conditions, an animal’s daily cycle is synchronised with environmental rhythms and it’s internal clock is ‘re-set’ each day (entrainment). • The clock-setting external cue (light, temperature, pheromones) that is used to synchronise the internal clock with the environment is a zeitgeber.

• Actograms show activity rhythms in an animal species usually looking at one varying environmental factor (eg light). • When the start of the period of the rhythm is changed so that it is earlier or later, it is called a phase shift. • A phase shift occurs when an organism is entrained to a new regime of environmental cues.

To do • Complete pages 41 -43 in BZ • Read through the ‘Animal timing behaviour’ worksheet to ensure your understanding of words in bold. • Work through ‘Assessment activities’ and then check your answers. • Look at the actograms and ensure you can read and understand them.

Make sure you can do the following • Describe, using supplied actograms, an animal’s free-running period. • Explain how zeitbebers entrain an endogenous rhythm to exogenous cues. • Discuss the adaptive advantage(s) of using a zeitgeber to entrain a free-running period to environmental cycles.