Taxes and Kineses
Laura Armstrong & Joe Wolfensohn
Teachers
Contents
Recall Questions
This topic requires prior knowledge of tropisms and insect gas exchange systems. You can test your knowledge on these below.
What does a positive response refer to in biology?
Refers to a movement or growth towards a stimulus.
What is a stimulus?
A detectable change in the environment which causes a living organism to respond to that change.
Why do insects keep their spiracles closed at times?
To reduce water loss through evaporation, especially in dry conditions, as insects have a relatively large surface area to volume ratio and are prone to drying out.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains taxes and kineses or read the full notes below. Once you've gone through the whole note, try out the practice questions!
What Are Simple Responses?
Simple responses keep simple organisms in a favorable environment. For example, woodlice and earthworms have simple responses to keep them in their favorable environment which would be a dark and moist place.
These responses are typically:
- Rapid.
- Automatic.
- Controlled by neurones or hormones in simple organisms.
Taxes (Singular: Taxis)
A directional response to a Stimulus: The organism moves towards or away from the stimulus.
In each case, movement is directed by the gradient of the stimulus.
Kineses (Singular: Kinesis)
A non-directional response to a stimulus. The organism changes the speed of movement and rate of turning depending on stimulus intensity.
Example:
- Woodlice in dry air:
-
- Move faster and turn less frequently.
- Increases chance of moving into more humid conditions.
- Once in a moist area, movement slows and turning rate increases, helping them stay in that favourable environment.
- These responses are not directional, so kinesis is a suitable response when the stimulus isn’t particularly localised. The end result is to keep the animal in a favourable environment.
Key Differences: Taxis vs Kinesis
Key Terms
- Taxis: A directional movement in response to a stimulus (e.g., light, chemicals).
- Kinesis: A change in the speed or frequency of movement in response to stimulus intensity, not direction (e.g., humidity, temperature).
- Positive response: Movement towards a stimulus (e.g., positive chemotaxis).
- Negative response: Movement away from a stimulus (e.g., negative phototaxis).
No answer provided.
Exam Tips
Taxis = Tactic = Direction.
Kinesis = Change in speed or turning rate.
Also, in explanations, always link the response to survival advantage (e.g. finding moisture to avoid desiccation, finding food, avoiding predators).
No answer provided.
The human body-louse is an insect which lives and feeds on the surface of the skin. A louse was placed in a chamber, half of which was kept at 35 °C and half at 30 °C. The diagram shows the pattern of movement of the louse.
a) Name the type of behavioural response shown by the body-louse in this investigation. Give evidence for your answer. (2 marks)
b) Suggest and explain one advantage of this behaviour to the human body-louse. (2 marks)
a) Kinesis
It is a non-directional response or
more turning at 35°C than at 30°C.
b) stays longer in warmer area / at 35°C / tends to leave cooler area / to leave 30°C / stays in favourable conditions. remains near food source / on host.
(Remember human body temperature is around 37)
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!