Response to a Stimuli
- Created by: wana.m
- Created on: 03-05-15 20:14
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- response to stimuli
- sensory reception
- stimulus are detectable changes in the internal and external environment of an organism that produces a response in the organism
- Stimuli are detected by Receptors (cells or organs)
- Receptors transform stimuli energy to form another form of energy in order to lead to a response.
- Responses are carried out by effectors (muscles or glands)
- Receptors and effectors communicate via the use of hormones. this is a slow process in both plants and animals.
- Responses are carried out by effectors (muscles or glands)
- A more rapid means of communication in animals is via the nervous system.
- stimuli--->receptor--->coordinator--->effector--->response.
- Receptors transform stimuli energy to form another form of energy in order to lead to a response.
- Stimuli are detected by Receptors (cells or organs)
- the ability to respond to stimuli increases the organisms survival rate.
- stimulus are detectable changes in the internal and external environment of an organism that produces a response in the organism
- Stimuli are detected by Receptors (cells or organs)
- Receptors transform stimuli energy to form another form of energy in order to lead to a response.
- Receptors and effectors communicate via the use of hormones. this is a slow process in both plants and animals.
- A more rapid means of communication in animals is via the nervous system.
- stimuli--->receptor--->coordinator--->effector--->response.
- A more rapid means of communication in animals is via the nervous system.
- Receptors and effectors communicate via the use of hormones. this is a slow process in both plants and animals.
- Receptors transform stimuli energy to form another form of energy in order to lead to a response.
- Stimuli are detected by Receptors (cells or organs)
- e.g. detect and move away from harmful stimuli like predators, extreme environment (e.g. high temperature) or detect and move towards stimuli e.g. a source of food.
- These organisms that survive can breed successfully & pass their alleles to the next generation.
- therefore this states that there is selection pressure i.e.. organisms with better responses to stimuli are more likely to be selected
- These organisms that survive can breed successfully & pass their alleles to the next generation.
- stimulus are detectable changes in the internal and external environment of an organism that produces a response in the organism
- Responses
- Taxes
- This is a simple response. A motile organism responds directly to environmental changes by moving their body...
- Example of Taxis,
- Single-celled algae move towards light (positive photo-taxis). This increases survival as being able to photosyntheses effectively as there's more food
- Earthworms move away from light (negative photo-taxis) which increases it chance of survival as it takes them into the soil where they're better able to conserve water, find food & avoid predators.
- Some species of bacteria move towards highly concentrated glucose regions (positive chemo-taxis) which also increases chance of survival as glucose is a source of food.
- towards a favourable stimulus
- POSITIVE TAXIS
- or away from a unfavourable stimulus
- NEGATIVE TAXIS
- Example of Taxis,
- This is a simple response. A motile organism responds directly to environmental changes by moving their body...
- Kineses
- This is a response which brings about an increase in random movement from the organism (either away or towards the stimuli).
- the more unpleasant the stimulus, the more rapidly the organism moves & changes direction to allow it to go back into more favourable condtions
- Kinesis response is important when the stimulus is less directional e.g. temperature & humidity. These don't produce a clear gradient from one extreme to another.
- the more unpleasant the stimulus, the more rapidly the organism moves & changes direction to allow it to go back into more favourable condtions
- Example of Kinesis
- Woodlice in dry conditions lose water from their bodies. This effect creates rapid, random movement (inc. changes their direction more).
- This increases their chance of moving into a different, more favourable area of conditions (i.e. moist area).
- Once reached this area they would slow down and change direction less meaning they spent more time in these favourable conditions, thus increasing their chance of survival
- This increases their chance of moving into a different, more favourable area of conditions (i.e. moist area).
- Woodlice in dry conditions lose water from their bodies. This effect creates rapid, random movement (inc. changes their direction more).
- This is a response which brings about an increase in random movement from the organism (either away or towards the stimuli).
- Tropisms
- growth movement part of a plant in response to a Directional stimulus, so parts move...
- towards (positive --tropism) stimulus
- or away (negative -- tropism) from stimulus
- Plant SHOOTS grow towards light (positive photo-tropism), therefore the leaves are in the most favourable condition to capture light for photosynthesis
- Plant ROOTS grow towards water (positive hydro-tropism) so that the roots can develop where there's the most water available in the soil.
- Plant ROOTS grow away from light (negative photo-tropism) & towards gravity (positive geo-tropism). Both increase the probability that the roots will grow into the soil where roots are better able to absorb water & mineral ions
- Plant ROOTS grow away from light (negative photo-tropism) & towards gravity (positive geo-tropism). Both increase the probability that the roots will grow into the soil where roots are better able to absorb water & mineral ions
- growth movement part of a plant in response to a Directional stimulus, so parts move...
- Taxes
- stimulus are detectable changes in the internal and external environment of an organism that produces a response in the organism
- sensory reception
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