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jt || ContRoL AND COORDINATION, S| INLIvING ORGANISM, , <a ~ Wace a, , , , , , , , , , , , , , , , , , , , , , , , , , , , , {a) Sensitivity and response in plants : <=. a), , _™@ Detection of change in environment and mechanism of response in plants :, , “Living organisms exist in a changing environment. Some changes are favourable and, tv ‘azeous, while others are unfavourable or harmful. Sensitivity is the ability of, ssanisms to detect change and respond to it. Changes which are detected and lead to, esponses are referred to as stimuli. All living organisms respond to stimuli. Stimulus is a kind, Any physicochemical change of energy in the surrounding environment of an organism, , Sat can generate an impulse or response in the organism is called as stimulus., , " The stimulus may be external like water, temperature, oxygen, air etc. Whereas internal, , stimulus may be hormone, nutrient etc., _ Any sort of change in direction or position found in living organisms is called movement, , movement is associated with change of place it is termed locomotion, , : The process by means of which the living organisms, spontaneously or due to the, influence of stimuli, can move any part of their body is called movement., 4 In higher plants, movement is a common phenomenon. However, some exceptional, plants like chlamydomonas, volvox can very slowly swim in water and are not fixed at a, particular place., the whole body of an organism is shifted from one place to other place, it is ), . . = 55 1, locomotion. This is generally found in animals. However, Sponge, Coral, Ascidia etc. ©, e fixed at substratum—they exhibit little movement but no locomotion. These animals —, led as sedentary or sessile animals., ' In fact, the basic relation between movement and locomotion is that movement of, locomotory organs result into locomotion eg. movement of wings in birds result into flight., plant responses are less evident than those of, , As most plants are anchored organisms,, mely rare. Generally, plant responses are slow, , ; als. Rapid movements by plants are extre, growth movements or turgor movements., , © Plant sensitivity and response in Mimosa and Desmodium : Both the plants are, extremely sensitive. When the leaflets or Mimosa pudica (touch-me-not/Lajjabati) is, , 1