Weta and cockroach questions The chart below shows

Weta and cockroach questions

The chart below shows the activity of a weta kept in a laboratory at 20 OC. From day 1 to 11 the weta was exposed to 12 hours light followed by 12 hours dark. From day 12 it was kept in constant dark.

Free running period • The time between repeats of behaviour in CONSTANT conditions • In this case the behaviour starts later and later every “day” so it must be slightly longer than 24 hours Daily rhythm = circadian rhythm

Explain the activity pattern shown by the weta over the 30 days • It was regularly active during periods of light during the first 12 days • But it started progressively later when in constant conditions BECAUSE although it has a biological clock that keeps the rhythm, there is no zeitgeber to keep it in time. The endogenous free running period is slightly longer than 24 hours which is why it started activity later each day.

Endogenous or exogenous • Endogenous because the rhythmic behaviour continued after being put in constant conditions

• This actogram was incorrectly labelled. (You knew that weta is nocturnal) • This is how it should have looked

Light phase

Light phase Day 1

Light phase Day 2

Light phase Day 2 again

Light phase Day 3

Light phase Day 3 again This makes for easier comparisons

cockroaches

The diagram above records the spontaneous activity of two species of cockroaches over several days. The dark phase is shaded.

(a) Compare and contrast the behaviour of the two species. A B How are they the same? How are they different?

(b) Explain how you could find out if this rhythmic behavior was driven endogenously or exogenously. Endogenous means ……. Exogenous means ……. I would put them in ______ conditions. If the rhythmic behaviour continued it is driven ________ which means it has a ______

(c) Discuss what you would observe if C. subcorticaria had a biological clock and C. undulivitta did not. If C. sub had a biological clock I would observe that its behaviour in the constant conditions would. . . . … because _ _. However the rhythm _ _ ___ If C. und did not have a biological clock I would observe that its behaviour in the constant conditions would _ __ __. This is because _ __