My Science School

            Milk is a fine suspension of fat and protein globules in a watery liquid containing milk sugar (lactose) and other dissolved substances. Normally the fat is dispersed uniformly in the form of fine droplets and hence remains as an emulsion. But when milk is heated these fine droplets tend to raise up and at temperature of about  form a thick layer of cream on the surface. When milk comes to boiling, bubbles of steam formed at the bottom of the vessel rise up and force the thick creamy layer upwards causing the milk to spill.

                                    

            There is a close link between the sense of taste and the sense of smell. Much of what we think of as taste has a big smell component. The taste buds in the tongue monitor relatively crude sensation of the four basic tastes – sweet, salty, sour and bitter. Faint vapours of whatever we eat drift into the nasal cavity where the smell receptors add more detail to the information given by the taste buds.

When we have a cold our nose becomes blocked and the sensation of smell ceases. The gas and vapours from the food cannot be sensed by the smell receptors; consequently we cannot perceive the smell or aroma of the food, which in turn makes the food appear tasteless.

            Spoilage of foodstuffs is caused by microorganisms which decompose them to produce acid, alcohol, etc. Bacteria are always present in the atmosphere. When freshly prepared food is kept in the open for long periods it gets contaminated. The bacteria then act upon the foodcomponents such as proteins, carbohydrates and fats and break them down to products which due to their off-odours or bad-taste are not suitable for consumption. Factors such as high temperature and humidity help the bacteria to grow.

    Spoilage of food can be prevented by treatments like heat sterilization, refrigeration, deep-freezing and desiccation.

                                    

  Flowering is a natural mechanism by which the majority of plants perpetuate their species through the production of seeds. All the parts of a flower take part in one way or another in the reproductive process. The stamens consist of thread-like stalks supporting sac-like anthers which produce the pollen. The central pistil contains the ovary and a sticky stigma. The colourful petals serve as signals to attract insects and other pollinators. When pollinating insects or birds visit the flowers for nectar, they help transfer pollen to the stigma which leads to fertilization of the egg cells in the ovary. The ovary then grows into a fruit containing seeds that would, if planted, grow into new plants thus perpetuating the species.

            Like any living organism, plants need, besides air and sunlight, water and nutrients for growth and survival which they take up through their roots. For land plants, the soil provides the moisture and nutrients. The soil also protects the roots from rapid fluctuations in temperature, as just below the surface the temperature scarcely changes from day to night. But more importantly, soil provides the firm support which holds the plants on the ground. Some plants, like the water hyacinth which grow in water, and orchids which grow on trees do not need soil to grow on as they can get their nutrients from water or the host                                                                                              plant.

            All plants respond to touch, but Mimosa pudica, or the “touch-me-not” plant is more sensitive than the others. Whenever touched, the leaves of the mimosa plant close and drop immediately, appearing like a dead plant. Possibly it is a defense mechanism by which the plant protects itself against its enemies.

   The opening and closing of the leaflets and the entire leaf are controlled by fluid-filled sac-like structures found at the base of not only the compound leaf but of each leaflet as well. When the leaf is touched, a chemical signal immediately moves to the base of each leaflet making the fluid drain away from the sac which makes the leaflet fold. When the signal reaches the base of the whole leaf, it makes the entire leaf drop. If left untouched for some time, the sacs fill up and the leaflets open again.

When your mother frowns at you without saying a word, you know that you have displeased her. Her displeasure is expressed through her   body language. In this way, other emotions too, are reflected through When you cross your arms, and lean away from another person to you are telling him that you want him to keep a distance, though of course, it may also mean that your arms are cold. If you look at a person in the eyes while speaking, it is a sign of honesty and straight forwardness. Looking away can mean you are lying, or that you don’t like the person. A person who shakes his legs constantly, or wets his lips is under stress. A person who leans towards you with clenched fists is quite likely to attract you! So you see, understanding body language helps you to understand the emotions of other people better.

 

 

Some species of animals are especially clever at detecting human body language, both voluntary and involuntary. There is the instance of a horse called Hans, who seemed to be able to add, subtract, multiply, divide, work with fractions and do other intellectual tasks. If you asked him a question, Hans would reply by tapping his foot till the correct

Han’s abilities amazed the world, but a formal investigation showed that the horse was not really calculating the answers, but was responding to the questioner’s body language. As the horse’s taps approached the right answer, the questioner’s posture and facial expression

            The peculiar smell is produced by the soil inhabiting bacteria called streptomycetes. Streptomycetes are abundant in dry warm soil – a million of them are present in a pinch of soil. They release compounds such as geosmin and 2-methyl isoborneol, which vapourize easily, when wetted by rain water after a dry spell. That is why we get the musty odour only after the first rain of the rainy season. The smell can be detected in a newly ploughed field also.

            Vultures are scavenger birds which feed on the carcasses of large animals and search out their food by flying in circles at a height. Hovering at a height gives them the advantage of surveying a large area. This is because the effective area which they can survey is the base of a cone at the tip of which the birds fly. Greater the height of this cone, larger is the area of the base. Thus, birds flying in small circles at great heights can keep a watch on a large tract of land below to look for a meal. That is why vultures and other birds of prey like kites, hawks and raptors circle at great heights. Of course, picking up tiny animals from such distances requires sharp eyesight, which all these predatory birds have.

 

   The wings of butterflies and moths are covered with small scales. These tiny scales produce the magnificent colours and patterns by optical interference of light. The tiny scales reflect and disperse light producing brilliant colours. When we touch the wings, these tiny scales come out in the form of powder, thereby leaving the surface of the wings colourless.            

            The direction in which roots and shoots move after germination of a seed is guided by two opposing properties. On germination, the roots emerge first. They are guided downwards by the action of hormones which sense gravity. This property is called geotropism. The shoots, on the other hand, are guided upwards by hormones that sense light. This property is called phototropism. Together these two properties ensure that the roots and shoot grow the right way irrespective of the position of the germinating seed in the soil.

            Most birds produce sounds in their throats using a voice organ called the syrinx. But not all birds’ calls can be described as ‘songs’. Males of only about 5000 species of birds are known to produce organized patterns of sounds that can be called melodious and described as songs. Male birds sing to attract females and to warn off other males. Although no two individuals sing alike, the song of each species is distinct. Most birds usually sing in the morning or evening and are quiet at midday. During winter most birds don’t sing, but they burst out into myriads of melodies with the onset of the spring, the time for                                                                                             courtship and breeding.

         In animals belonging to the cat family and other nocturnal animals the back of the eye ball – the retina, has a layer called “tapetum lucidum”. This layer is made of special cells which reflect light falling on the retina. It is this layer which makes the eyes of these animals glow in the dark. The tapetum layer also helps the animals in gathering all the available light to see in near darkness    

            The camel’s hump is filled largely with fat, accumulated at times when food and water are available. This fat is digested to meet the energy needs of the animal. Camels can go for a week or more without water and for 10 days without food. During such periods the accumulated fat is used up. The hydrogen released as a by-product by the breakdown of fat combines with the oxygen the camel breathes in to produce water. By utilizing this metabolic water the camel can keep going for many days. In this process, it may lose up to 100 kg of body weight. But as soon as it arrives at an oasis, it is capable of rapidly drinking some 120 litres of water.