Taxis and kinesis

• Taxis


  Directional movement in response to external stimulus
• Kinesis


  Non-directional response to presence and intensity of external stimulus
• Taxis and kinesis


  • Maintain mobile organism in optimum environment e.g. to prevent dessication
• Many organisms respond to temperature and humidity via kinesis rather than taxis
• Reason for kinesis rather than taxis


  Less directional stimuli; often no clear gradient from one extreme to the other
• Recognising kinesis in an organism's movement


  1. Organism crosses sharp division between favourable & unfavourable environment: turning increases (return to the original favourable environment)

  2. If organism moves considerable distance into unfavourable environment: turning slowly decreases; begins to move in long, straight lines; sharper turns (lead organism to new environment)
• Chi squared


  Suitable statistical test to determine whether a factor has a significant effect on the movement of an animal in a choice chamber