Hi! I dont understand how humidity could be less 'directional' please help. This is in a level biology. response to stimuli aqa textbook
I indented the sentence I was talking about (4rd paragraph) but i added the whole paragraph from the textbook for context, Tysm!
Kinesis is a form of response in which the organism does not move towards or away from a stimulus. Instead, it changes the speed at which it moves and the rate at which it changes direction.
If an organism crosses a sharp dividing line between a favourable and an unfavourable environment, its rate of turning increases. This raises its chances of a quick return to a favourable environment.
However, if it moves a considerable distance into an unfavourable environment. Its rate of turning may slowly decrease so that it moves in long straight lines before it turns, often very sharply.
This type of response tends to bring the organism into a new region with favourable conditions.
It is important when a stimulus is less directional. Humidity and temperature, for example, do not always produce a clear gradient from one extreme to another.
Lose water from their bodies in dry conditions – damp area is favourable.
When they move from a damp area into a dry one, they move more rapidly, and change direction more often. This increases their chance of moving back into the damp area. Once back in the damp area, they slow down and change direction less often. This means they are more likely to stay within the damp area.
However, if after some time spent changing direction rapidly they are in the damp area their behaviour changes. Instead they move more rapidly in straight lines, which increases their chances of moving through the dry area and into a new damp one. In this way they spend more time in favourable damp conditions than in less favourable drier ones.
This prevents them drying out and so increases their chance of survival.
This is what it says in the cgp book:
Woodlice in humidity - move slowly and turn less often - so that they stay where they are
As the air gets drier, they most faster and turn more often, so that they move into a new area.