AQA A Level Biology: Survival and response Flashcards
What is a stimulus?
A detectable change in the internal or external environment that triggers a response.
What is the role of receptors?
Detect stimuli and convert energy from the stimulus into a nerve impulse.
What is the role of effectors?
Carry out the response, usually muscles or glands.
What is the definition of a response?
A reaction produced by an effector after a stimulus is detected.
What is a reflex?
A rapid, involuntary response to a stimulus that protects the body.
What is the reflex arc?
The pathway taken by nerve impulses during a reflex action:
Stimulus → Receptor → Sensory neuron → CNS → Motor neuron → Effector → Response
What is taxis?
A directional movement in response to a stimulus.
What are the types of taxis?
- Positive taxis: Movement towards the stimulus.
- Negative taxis: Movement away from the stimulus.
Give examples of taxis.
- Phototaxis: Movement towards/away from light.
- Chemotaxis: Movement towards/away from chemicals.
What is kinesis?
A non-directional movement in response to a stimulus where the speed and rate of turning change.
What is the difference between taxis and kinesis?
- Taxis: Directional movement towards/away from a stimulus.
- Kinesis: Random movement where the organism moves faster and changes direction more in unfavourable conditions.
Why is kinesis beneficial to organisms?
It increases the chance of finding a more favourable environment.
What is tropism?
A growth response in plants where the direction is determined by the stimulus.
What are the types of tropism?
- Phototropism: Growth in response to light.
- Gravitropism (geotropism): Growth in response to gravity.
- Hydrotropism: Growth in response to water.
What is positive and negative phototropism?
- Positive phototropism: Growth towards light (shoots).
- Negative phototropism: Growth away from light (roots).
What is IAA?
Indoleacetic acid, a type of auxin that controls plant growth by affecting cell elongation.
How does IAA cause phototropism in shoots?
- IAA accumulates on the shaded side of the shoot.
- This causes cell elongation, resulting in bending towards the light.
How does IAA cause gravitropism in roots?
- IAA accumulates on the lower side of the root.
- It inhibits cell elongation in roots, causing them to grow downwards.
What is the role of the nervous system in response?
It detects stimuli, processes information, and coordinates a response.
What are the divisions of the nervous system?
- Central nervous system (CNS): Brain and spinal cord.
- Peripheral nervous system (PNS): Sensory and motor neurons.
What are the divisions of the motor nervous system?
- Somatic nervous system: Controls voluntary movements.
- Autonomic nervous system: Controls involuntary responses.
What are the divisions of the autonomic nervous system?
- Sympathetic nervous system: Stimulates “fight or flight.”
- Parasympathetic nervous system: Promotes “rest and digest.”
What is the difference between the sympathetic and parasympathetic nervous system?
- Sympathetic: Increases heart rate, dilates pupils, inhibits digestion.
- Parasympathetic: Decreases heart rate, constricts pupils, stimulates digestion.
What is the role of sensory neurons?
Carry nerve impulses from receptors to the CNS.
