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Stimulus and Response in Plants and Animals.

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Introduction

´╗┐Topic: Response of plants and animals Stimulus and Response Plants and animals receive information about changes in conditions both inside and outside their bodies. Any information to which an organism reacts is known as a stimulus because it stimulates the organism to make a response. A stimulus could be an external event, e.g. change in the direction of light, change in light intensity or change in temperature. Internal events include arrival of food in the stomach, changes in blood glucose levels, entry of foreign organisms in the body or change in water content of cells. Some changes are favourable and advantageous to the organism, others are unfavourable or harmful and others may be of no importance. ...read more.

Middle

It may also involve muscular activity, i.e. movement, for example, an increase in the heart rate in response to an increase in the carbon dioxide content of the blood. The importance of response Response to stimuli is important for the survival of organisms. The shoots of green plants grow in the direction of light so they can make food. The roots grow in the direction of gravity. This ensures that they grow towards moisture and also provide stability for the plant. Animals avoid unsuitable conditions by moving towards more suitable ones, for example, earthworms avoid the drying effects of the sun by moving towards dark, moist areas. Humans maintain a constant body temperature by producing sweat when body temperature rises above normal temperature. ...read more.

Conclusion

An animal responds to changes in its internal environment which signal that it needs food. The hungry animal will then look for food and recognize it when it finds it. Without these responses it would soon die. A male moth is attracted to a female of the same species by being able to detect and respond to chemical signals released by the female. A female bird is able to detect and respond to the courtship behavior of a compatible male. These responses ensure that reproduction takes place and the species survives. Plants do not usually respond as actively as animals but there are some interesting exceptions; the sensitive plant (Mimosa pudica) folds its leaves quickly when touched. This makes it more difficult for it to be seen by animals which might eat it, and some insect-eating plants close certain specialized structures when insects rests on them, trapping the insects which they then digest. ...read more.

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