- This is a response that causes an organism to move to avoid predation, it is a fast automatic response
- For example earth worms will go underground if they feel vibrations in the ground, they do not have eyes so rely on other sense organs (such as light or touch) - they have very wide axons to speed up the nerve impulse if it is not myelinated.
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- This is a non-directional movement that causes the rate of movement to increase but the direction is not coordinated
- For example this is the case with woodlice, they move around very rapidly and randomly when the conditions are bright or dry. They will slow down when they find cool, damp, dark areas
- Woodlice are not good at conserving water so need to spend most of their time where humidity is high to avoid dehydrating
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- This is the directional movement of an organism as a response to a change in stimulus
- Example of this can be chemotaxis or phototaxis - towards the stimulus is positive and away is negative
- Nematode worms wiggle their heads from side to side to test the strength of the chemical signals in the air through chemoreceptors before moving its whole body up or down the concentration gradient
- Maggots move away from a light source, they have photoreceptors at their anterior ends and if a light shines onto it then they move their heads to sample the light intensity and will move in the direction which has the lower light intensity
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More complex innate behaviour
- This is a more complicated system - the waggle dance is performed by honey bees to communicate the distance and direction of a food source
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Case study: sand wasps and fixed action patterns
- Sand wasps, called Sphex, dig a shaft into the soil and a small compartment where they will lay their eggs. When the nest is almost complete the female Sphex goes off in search of pray, she brings it back to the nest, leaves it outside the entrance, goes into the nest, turns around and comes back out to pull the prey down.
- She lays an egg and then repeats the process - her behaviour is highly sterotypical.
- When the prey was moved in an experiment away from the entrance of the nest the wasp comes up and moves it closer to the entrance before going back into the nest and pulling it down. Her actions are continuous.
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