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Why does our hair change its colour as we age?

     Hairs are the appendages of the skin generated from the epidermal layer. Hair is a made up of Keratin a highly insoluble and mechanically stable fibrous protein. This Keratin is not only found in hairs but also in the skin. Actually Keratin is produced from the Keratinisation zone of the epidermis, which is the outer most layer of the skin. In the skin it provides water proofing quality.

            The Keratin is generally pigmented. It is intensively pigmented in the hair. The dark black colour of the hair is due to the presence of high concentration of melanin pigments in it. The skin colour is also due to the presence of this pigment in the keratinocytes.

            The Keratin gets its melanin pigments from melanocytes, which are found in the inner layer of the epidermis, which is found just beneath the keratinizing layer. The melanocytes have long progresses which extent between and under the cells of the epidermis. The melanin granules formed in the melanocytes pass along their branches and are secreted at their tips. The granules are subsequently engulfed by the keratinocytes, which make up 90 per cent of the epidermal cells.

            Melanin is a protein like polymer of the amino acid tyrocin. In its biosynthesis tyrocin is converted in to dihydroxy phenyl alanine (DHPA) by oxidative enzymes amongst which tyrocin is particularly important. Then a series of reactions take place during which polymerization occurs to form the final melanoprotein.

            The hair grows only from the keratinocytes of the germinal matrix of the hair follicle. This germinal matrix lies in the proximal enlargement of the rot hair, called the hair bulb. The shaft, which projects from the surface, consists of an inner medulla, an intermediate cortex and an outer cuticle. All these parts are made up of cornified cells.

            The medulla is composed of polyhedral cells; the cortex consists of elongated cells with inner lumen. These cells are united to form flattened fusiform fibers. The lumens of these cells contain pigmented granules in dark hair and air space in white hair.

            The development of white hairs because of the absence of melanin pigments, may be due to the absence of one or more enzymes, necessary for the DHPA path way. It will lead to the failure of melanin accumulation in the keratinocytes, found in the hair bulb, from which hair is growing.

            Usually such physiological disorder occurs in the old age, which results in the growing of gray and white hairs in the body.

How do birds navigate home after long journeys?

         

 

 

 

 

 

 

  There are many theories explaining this capability of birds. According to one of them, the Sun’s rays and the direction of winds help them to navigate. Birds’ extra sensory capabilities assist them in this task and direction them with the help of the Earth’s magnetic field.

            Another theory suggests that these winged wonders understand star-maps so well that it helps them to rack their way. But no one answer has been put down for this as of now.

            Birds have the capability to detect changes in atmospheric pressure, weather and earth’s magnetic field. Based on these they locate specific regions and find their home. But the most important navigational aid is said to be “internal magnetic compass” that they are said to posses in their brain. The compass works in relation to the earth’s magnetic field. The magnetic currents generated here are turned into flight paths.

            As a result, disturbances in Earth’s field can seriously affect bird’s judgment. In July, 1998, 3000 homing pigeons that set off for their return journey from northern France to southern England could not reach their destination because an explosion on the surface of the Sun, a few days prior to their journey, had sent radiations that disrupted the Earth’s magnetic field. As a result their internal magnetic compass picked up confusing signals and the birds lost their way.

Do sheep swim? If so, how do they learn?

            Yes, sheep do swim, said Edward Spevak, assistant curator of mammals at the Bronx Zoo. “It’s basically instinctive, a life-saving device,” he said. They don’t go swimming every day, but in case of flooding, or falling into a river, in essence they know how to swim. Sheep have never been known as big swimmers, and mose of the habitat where they evolved does not have a lot of water resources, but swimming is part of their repertoire of skills, he said.  First of all, like many animals, they float, Spevak explained, “Then, in struggling to keep the head above water and to keep breathing, the method they use is basically fast walking, which constitutes a kind of dog paddle,” he said.

            Other large mammals are swimmers, too. Spevak said. Cattle can swim when herded across a river, as Western movie fans know. Deer can swim, as well, “The moose, the largest deer in the world, actually feeds in water and is a very good swimmer.” Spevak said.

It is true that a red flag agitates a bull?

    It is generally believed that anything red makes a bull angry and causes it to attack. Therefore, the bull fighter has to have a bright red cape and use a red cloth.

            The truth is that if the bull fighter had any other coloured cloth he would be able to accomplish the same reaction from the bull. Bulls are colouring blind.

            Many experiments were conducted where they used white cloth and got the bulls to behave in the same way as with the red cloth.

            The reason is the movement of the cap and not colour of the cloth brings about the reaction in the bull. Anything waved in front of a bull would excite it.

How come zoo animals like lions seem to lie around all day and yet stay fit? Also pet cats seem to lie around all day and yet stay fit?

It is a partly a matter of appearances, with zoo animals less active at peak visiting hours, and partly a matter of normal rhythms of carnivore life. It is said that lions in the wild are normally inactive for 20-22 hours a day because they need to conserve their energy for hunting. They can never be sure where their next meal will come from.

As for the house cat, although it does know when the next can will be opened, the basic behavioural pattern is the same. Even a cat that has never seen real prey will stalk a butterfly through the window.

Young animals can afford to do that, but from an evolutionary point of view, old lions especially must conserve their energy for the business of surviving. At some point of life, their metabolism does begin to slow down, and a sedentary cat may become overweight.

In general, many zoo animals are from hot climates and are most active in early morning and late afternoon. They sensibly lie low from 11-3 on a hot day, so visitors should try to come early in the morning. Zoo animals have the benefit of a nutritional staff that prepares diets as close to natural as possible. Modern zookeepers also make sure that animals mimic natural behaviour, living in groups, with plenty of space, and foraging and competing for food. Some do get chunky, like the dominant animal in a group that always gets its fill, but most stay lean.

Why and how do falling cats land on their four legs, always?

 

 

 

 

 

 

 

            Cats have a superb vestibular system and make gyroscopic turns, while falling, so that all the four feet quickly point downwards, regardless of their orientation at the start of the fall. This enables them to dissipate the impact force, of the fall, through all the four limbs and have a higher survival rate compared to other animals like dogs. This lends credence to the old adage that cats have nine lives. Cat-specific advantages are believed to have evolved through natural selection, according to Prof. D. Balasubramaniam, Director Centre for Cellular and Molecule Biology, Hyderabad.

            A cat falling from great heights (say100 ft) extends its limbs, reflexly, more horizontally in a flying-squirrel fashion. This reduces the velocity of the fall besides absorbing the impact over a greater area of its body, say scientists. Also, when falling, the animal does so with its limbs flexed so that much of the impact is dissipated through its soft tissues. This is the same reason why parachutists are trained to dissipate impact forces by lending with knees and hips flexed, than rolling, (J.M. Diamond, Nature, April 14, 1988).

What imparts fragrance to flowers, fruits and species?

            Fragrance in flowers, fruits and spices is due to a wide variety of essential oils (volatile liquids) present in them. They are mostly insoluble in water but freely soluble in alcohol, ether and vegetable mineral oils. They are not oily to touch.

            The oils may be grouped into five classes, according to their chemical structure alcohols, esters, aldehydes, ketones, lactones and oxides.

            The fragrance may be in leaves (as in sage, thyme and mint), in bark (as in cinnamon and cassia), in wood (as in cedar and sandalwood), in flower petals (as in rose and violet), in seeds (as in anise and caraway), in roots, in fruit rind (as in orange) or in resinous gums secreted from the tree (as in camphor and myrrh).

            The oils are formed generally in the green parts of the plant, and with plant maturity, transported to other tissues particularly to flowering shoots. The exact function of an essential oil in a plant is unknown – it may be to attract insects for pollination, or to repel harmful insects, or it may simply be a metabolic intermediate.

            Dr. Palaniappan of Pudukkottai, TN, writes: aroma associated with cinnamon, vanilla and cuminum are due to carbonyl group of aldehydes and ketone. Aromatic aldehydes such as cinnamaldehyde and vanillin are found in cinnamon and vanilla respectively. Cumaldehyde (p-isopropyl benzaldehyde) is found in the volatile oil of cuminum. Aliphatic esters namely methyl n-butyrate and ethyl n-butyrate are found in apples and pineapples. Benzyl acetate, an aromatic ester imparts fragrance to jasmine. Spices and condiments contain monoterpenoids with two isoprene units and sesquiterpenoids with three isoprene units. Eugenol in clove, linalool in coriander, zingiberene in zingiber, menthol in mint, cineol in cardamom and anethole in feoniculum are a few examples. Sandalwood contains a terpenoid called santol in the wood cells.

Fruits were supposed to attract animals. So what is the point of lemons tasting, so sour? Are there any animals which actually like the taste? Did we breed lemons from ones that were sweeter? Or do an

            Plants use many methods to distribute their seeds and succulent fruits such as lemons are not necessarily designed to be eaten. Many, such as blackberries and plums, are bitter until the seeds are ‘ready, while others, apples and many tropical fruits are designed to encourage pecking by birds, which scatters the seeds. Another group including figs and senna pods encourage animals to eat the fruits without digesting the seeds, allowing the seeds to pass undamaged through the animals, be it a mouse and elephant.

Yet other fruits remain unappetizing to animals until they drop to the ground, where they are eaten or scattered when fully rips or rotten.

Lemons come into this category, though it is possible that monkey, baboons or other animals may be fascinated by the bitterness and attack them earlier, giving  themselves an unexpected dose of vitamin C and, of greater benefit to the tree, subsequently spitting out the pipe. 

            Many citrus trees that are natives of and regions have sour fruits to discourage animals from eating it. The flesh of a lemon is there for three main reasons: to add weight so that it will roll a long way after it falls from the tree. To dissuade foraging animals from eating the seeds before they can develop and to supply water and nutrients as the flesh rots around the germinating seeds. The main aim of any seed is to propagate the species, not to feed the local animals. Animals benefit only as a side effect of plants wanting to use them as a form of transport for their seeds.

            The trouble with citrus fruits is that they have been cultivated for so long that nobody knows what their original seeds dispensers actually were. In cultivation, however, they do seem to be eaten by monkeys. May be monkeys like acid tastes more that more than people do. Many tropical fruits are dispersed by becoming over ripe, falling to the ground and being eaten by animals. May be the acid in citrus fruits was meant to act as a deterrent to these foraging animals  so that the fruits and the seeds the contained were left to grow where fell. 

How do trees reduce air pollution?

            Plants can prevent pollution of environment in many ways. However, the answer is restricted to prevention of air pollution by trees.

            The major components of atmosphere are nitrogen (78.08 per cent) and oxygen (20.95 per cent) (major) with minor components are argon and carbon dioxide (0.0314 per cent) and many trace elements such as neon, helium, nitrous oxide, methane, carbon monoxide, sulphur dioxide, ozone, ammonia and aerosols (colloidal sized particles) are also present.

            The ratio of these components is changing very fast due to increased human activities like fossil fuel burning, afforestation and changes in land use. They result in the liberation of tones of carbon dioxide, carbon monoxide, methane and aerosols into the atmosphere. The server human interference over the last century is said to have strained the buffering capability of nature.

            Trees help reduce the pollution in more than one way. First, they act as sink for carbon dioxide. Through photosynthesis they synthesize carbohydrates using carbon dioxide, water and sunlight. This way thousands of tonnes of carbon dioxide are trapped by the trees. By the same process, trees release oxygen, which is needed by other living organisms. They also help in cooling of the atmosphere by transpiration, a process in which water is given up by plants as vapour. I addition, aerosols and dust particles (components of atmosphere pollution) settle on the dense foliage of trees. Thus trees, especially the tall ones with dense foliage around houses and industrial establishments, reduce aerosol and dust pollution by acting as barriers or curtains.