Taxis & Kinesis (AQA A Level Biology): Revision Note
Exam code: 7402
Taxes & kineses
Taxes and kineses are simple, innate responses that enable mobile organisms to stay in a favourable environment; they allow organisms to respond to stimuli such as:
light
temperature
humidity
Kineses
Kineses (singular kinesis) are non-directional responses to a stimulus that involve random movement, e.g.:
flatworms show photokinesis
in bright light flatworms move faster and change direction more often, increasing the chance of leaving the unfavourable conditions; this allows them to avoid predation
Taxes
Taxes (singular taxis) are directional responses to a stimulus that involve moving towards or away from a stimulus, e.g.:
Euglena are single-celled organisms that show positive phototaxis
they swim towards any light source using a flagellum; this allows them to carry out photosynthesis
Examiner Tips and Tricks
Make sure that you are comfortable with the difference between kineses and taxes:
kineses are non-directional and involve random movement
taxes are directional and involve movement towards or away from a stimulus
Be careful not to confuse these simple animal responses with plant responses, e.g. a beetle moving away from light is a taxis and not a tropism.
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