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Animal Behaviour

Wherever people have a chance to watch animals - at a zoo, park, pet store, or circus - it is evident that animal behaviour is a source of fascination1 for most humans. As they watch animals at play and at rest, feeding or protecting themselves, and tending to their young, frequently marvel (восхищаться) at the similarities between animal and human behaviour. These similarities are, in fact, one important reason for studying the activities of animals: that is, their implications for the better understanding of human behaviour.

The question of why animals behave the way they do has attracted the interest of scientists from many fields - psychologists, zoologists, ecologists, geneticists, endocrinologists - to name a few.

What is Behaviour? Simply defined, behaviour is activity in response to an internal or external stimulus. All animals make adjustments to information or stimuli, from their external and internal environments. These adjustments may be voluntary or involuntary, and may range from a simple, single act to a complex and elaborate sequence of activities.

Taxis, Kinesis, Reflex. A very important behavioural response in the lives of many invertebrates and some vertebrates is the taxis. This is a directional movement in response to a specific type of environmental stimulus. The taxis response is inborn, and need not be learned; but it is fixed, and cannot be altered to suit unusual conditions.

For example, a moth navigates in a straight line by keeping at a constant angle to the parallel rays of the sun (or more often the moon, since most moths are nocturnal). This taxis works well under natural conditions. However, it can cause trouble2 when the light source is so

near that it produces diffused instead of parallel rays, as in the case of a candle (свеча) or a light bulb3. In this case, instead of a straight path, the constant angle may lead the moth into a spiral, so that it circles

ever inward toward the light source and is eventually burned to death.

Another involuntary behaviour pattern, best known in simple organisms, is kinesis. This is an increase or decrease in the movement of an animal in proportion to the intensity of a stimulus. Such movements are not directional like the taxis. Instead, they consist of increases in the rate of turning from side to side, or in other body movements. Planarians, for instance, when placed in the light, do not swim directly back to the darker areas where they normally stay. Instead, they continue weaving from side to side, but they turn more strongly toward the side where they encounter less intense light. This turning eventually bring them back to the dark area.

A third behaviour pattern involving relatively simple, innate responses to stimuli is reflex. A reflex is the involuntary movement of some part of the animal's body in response to a stimulus. A familiar example is the kicking motion you make when the tendons below your kneecap are struck by a doctor's hammer. Unlike the taxis and kinesis, the reflex does not involve a complete body movement.

Notes

1. a source of fascination - источник восхищения

2. trouble - неприятность, беда

3. a light bulb - электрическая лампочка

 



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