Rhythms

Question 1

Describe things that might control an

exogenous rhythm

Answer 1

Light availability (day-night cycle), tide lengths and changing day lengths can influence the active and inactive periods for an organism and they are all externally driven from the environment

Question 2

Describe what drives an endogenous rhythm

Answer 2

The internal biological clock is built in and is naturally occurring within an organism. The endogenous rhythms are regulated by the organisms internal biological clock and do not depend on external stimuli.

Question 3

Explain what a free running period is

Answer 3

A free running period is cyclic behaviour that is observed without an external stimulus

When a biological rhythm is running during constant environmental changes the rhythm is said to be free-running

Question 4

Describe the purpose of a zeitgeber

Answer 4

The purpose of the zeitgeber is to give external cues so that the activity of an organism occurs at the correct times each day

Question 5

Explain what entrainment is

Answer 5

Entrainment is the act of resetting the internal biological clock to match the environment

Question 6

Explain what phase shift is

Answer 6

Phase shift is when the time of activity or inactivity is pushed forwards or backwards

When an internal clock in entrained, phase shifting occurs

Question 7

Explain what an actogram is

Answer 7

An actogram is a graph showing when an organism is active and inactive over the course of each day, as well as any changes in the environment

Question 8

Explain everything on an actogram

Answer 8

Dark lines: show periods of activity

Consistent active periods: show the normal activity and inactivity of an organism with a zeitgeber present

Inconsistent active periods: show the activity and inactivity of an organism without a zeitgeber present

Free running period: can see that the active periods occur earlier or later each day the zeitgeber is absent