Stimulus and Response- AQA biology
- Created by: lily goulder
- Created on: 09-02-22 08:01
View mindmap
- Stimulus and response
- Stimulus = Detectable change in the environment
- Response to a stimulus increases the chances of survival
- Stimulus-receptor - coordinator - effector - response
- A taxis is when a motile organisms moves its whole body towards (positive) or away (negative) from a stimulus
- A kinesis is when an organism changes the speed of movement and rate of direction change when exposed to a stimulus. This increases chances of finding a suitable environment
- Non-directional response
- A tropism is the growth of a plant towards (positive) or away (negative) from a stimulus
- Directional responses
- A taxis is when a motile organisms moves its whole body towards (positive) or away (negative) from a stimulus
- Directional responses
- IAA- Synthesised in the tips of roots and shoots
- Positive Gravitropism- IAA is transported to the bottom of the root due to gravity. Here it inhibits cell elongation. Top of the shoot grows more than the bottom, causing the root to bend downwards.
- Helps plants be anchored in the ground. Allows them to find water for turgor support and photosynthesis.
- IAA binds to receptor on cell membrane. It allows hydrogen ions from the cytoplasm to the cell wall. This lowers the pH. Expansin is activated. H bonds are broken in cellulose. Water can easily enter the vacuole by osmosis. The cell swells and elongates.
- Positive Gravitropism- IAA is transported to the bottom of the root due to gravity. Here it inhibits cell elongation. Top of the shoot grows more than the bottom, causing the root to bend downwards.
- Central Nervous System is the brain and spinal cord
- Reflex arc
- Stimulus - Receptor- Sensory neurone-Intermediate neurone- Motor neurone -Effector - Response
- Importance of a reflex: Involuntary and don't need slow decisions from the brain. The brain does get some impulses in case it needs to override something.
- Protect body from harm. Don't have to be learnt. Very fast. Only include 2 synapses (slowest part)
- Reflex arc
- Stimulus = Detectable change in the environment
Similar Biology resources:
Teacher recommended
Comments
No comments have yet been made