A stimulus is a change in the internal or external environment that produces a reponse.
Animals with the correct responses to stimuli have more chance of survival and then more chance of passing on their alleles.
This then gives a selective pressure to organisms with the appropriate responses.
Taxes: A simple movement towards or away from a stimulus. If it is towards the stimulus, for example bacteria moving towards glucose, then it is known as positive taxes, and if it is away from the stimulus, such as an earth worm…