Organism response to Stimuli
- Created by: Megan Lewsley
- Created on: 15-11-19 10:26
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- Organisms Responding to Change
- Stimulus
- Detectable change to external environment or internal
- Produces organism response
- Caused by muscle contraction in animals
- Caused by chemical production in plants
- Individuals with most appropriate response survive & pass on alleles - natural selection
- Caused by muscle contraction in animals
- Individuals with most appropriate response survive & pass on alleles - natural selection
- Produces organism response
- Receptor
- Co-ordinator
- Effector
- Response
- Effector
- Co-ordinator
- Detectable change to external environment or internal
- Responses
- Help organisms to survive
- Taxes
- Kineses
- Tropisms
- Help organisms to survive
- Taxes
- Simple Directional Response
- Positive Taxes
- Move towards stimulus
- Negative Taxes
- Move away from stimulus
- Kineses
- Response to general stimulus
- In favourable conditions, move slowly & change direction frequently to stay in same region
- Not directional as there is no clear gradient. e.g. temperature
- Tropisms
- Growth movement of a plant in response to a directional stimulus
- Phototropism - light
- Gravitropism - gravity
- Hydrotropism - water
- Plant Growth Factors
- Chemicals that control plant response to the environment, as plants don't have a nervous system
- Indoleacetic Acid (IAA)
- Chemicals that control plant response to the environment, as plants don't have a nervous system
- Plant shoots
- Positive phototropism & negative gravitropism
- Move towards light & away from gravity
- Cells in tip produce IAA
- IAA diffuses evenly down the shoot, causing cells to elongate
- Directional light causes IAA to diffuse down the dark side more than the light.
- Greater concentration of IAA on the dark side, means cells elongate more than that of the light side.
- Dark side gets longer & causes shoot to bend towards the light.
- Greater concentration of IAA on the dark side, means cells elongate more than that of the light side.
- Directional light causes IAA to diffuse down the dark side more than the light.
- IAA diffuses evenly down the shoot, causing cells to elongate
- Positive phototropism & negative gravitropism
- Plant roots
- IAA causes growth to decrease.
- If root grows horizontally, IAA diffuses to bottom side of root
- Higher concentration of IAA on bottom side reduces growth, causing root to bend down into the soil.
- Positive gravitropism
- Higher concentration of IAA on bottom side reduces growth, causing root to bend down into the soil.
- If root grows horizontally, IAA diffuses to bottom side of root
- IAA causes growth to decrease.
- Growth movement of a plant in response to a directional stimulus
- Stimulus
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