Biology aqa unit 9.1 key terms and points to remember 4.0 / 5 based on 1 rating ? BiologyA2/A-levelAQA Created by: laurenCreated on: 27-02-13 13:53 what is a stimulus a stimulus is a detecable change in the internal or external evironment of an organism that produces a response 1 of 24 what are stimuli detected by cells or organs known as receptors 2 of 24 what does a receptor do transform energy of a stimulus to a form of energy that can be processed by the organism leading to a response 3 of 24 effectors are... a range of diferent cells, tissues, organs or systems that carry out a response 4 of 24 what is needed between receptors and effectors and why? a form of comunication, because they are usually some distance apart 5 of 24 two methods of communication between receptors and effectors... 1) hormones (slow animals and plants) 2) the nervous system (rapid animals) 6 of 24 what is each receptor linked to within the nervous system a central coordinator 7 of 24 events from stimulus response is summarised as stimulus--receptor--coordinator--effector--response 8 of 24 what is a taxis a simple response whose direction is detirmined by direction of stimulus 9 of 24 how does a motile organism ( or motile part of it) respond as a result of a taxes by moving either towards or away from the stimulus depending on conditions 10 of 24 how are taxes classified Positive taxis ( moving towards the stimulus) negative taxis ( moving away from stimulus) and by the ature of the stimulus 11 of 24 if a single celled algae move towards light it is a positive phototaxis 12 of 24 earthworms move away from light negative phototaxis 13 of 24 bacteria moving towards a higher concentration of glucose positive chemotaxis 14 of 24 what is a kinesis a form of response whereby the more unpleasent the stimulus the more rapid the organism moves and changes direction 15 of 24 a kinesis results n an increase in random movements 16 of 24 what is a kinesis response designed to do bring the organism back into favourable conditions 17 of 24 when are kinesises important when a stimulus is less directional 18 of 24 two example of stimuluses to a kinesis response temperature and humidity 19 of 24 what is a tropism a growth movement of part of a plant in response to a directional stimulus. 20 of 24 example of tropism plant shoots grow towards light (positive phototropism) plant roots grow away from light ( negative phototropism) plant roots grow towards water ( positive hydrotropism) 21 of 24 some species of bacteria move away from the waste products they produce ... this is known as negative chemotaxis 22 of 24 the sperm cells of a moss plant are attracted towards a chemical produced by the female reproductive organ on another moss plant positive chemotaxis 23 of 24 the young stems of seedlings grow away from gravity negative geotropism 24 of 24
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