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EnglandBiologyQuick questions
3.6 Organisms respond to changes in their internal and external environments
Quick questions on Stimuli and responses: taxes, kineses, tropisms and the reflex arc - AQA A-Level Biology
6short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the simple reflex arc?Show answer
A reflex is a rapid, automatic (involuntary) response to a stimulus that does not involve conscious thought. Reflexes protect the body from harm because they are fast and do not need processing by the brain.
What is taxis?Show answer
A directional response in which the organism moves its whole body towards or away from a directional stimulus. A positive taxis moves towards the stimulus, a negative taxis moves away. Example: motile bacteria show positive chemotaxis towards glucose; maggots show negative phototaxis away from light.
What is kinesis?Show answer
A non-directional response in which the rate of movement and rate of turning change with the intensity of the stimulus. There is no movement towards or away from a particular direction. Example: woodlice move faster and turn less in dry air, so they leave dry areas and accumulate in humid areas where they slow down and turn more.
What is q1?Show answer
Distinguish between a taxis and a kinesis. [2 marks]
What is q2?Show answer
Explain why a shoot bends towards a light source coming from one side. [4 marks]
What is q3?Show answer
Describe the pathway of a simple reflex arc and explain why it protects the body. [4 marks]
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