My Science School

Fingerprint formation is like the growth of capillaries and blood vessels in angiogenesis. The pattern is not strictly determined by the genetic code but by small variables in growth factor concentrations and hormones within the tissue. There are so many variables during fingerprint formation that it would be impossible for two to be alike. However it is not totally random, perhaps having more in common with a chaotic system than a random system.

It is believed that the development of a unique fingerprint ultimately results from a combination of gene-environment interactions. One of the environmental factors is the so-called intrauterine forces such as the flow of amniotic fluid around the fetus. Because identical twins are situated in different parts of the womb during development (although they are not static), each fetus encounters slightly different intrauterine forces from their sibling, and so a unique fingerprint is born.

            Your genes specify only your biochemistry and through it, your general body plan. The pattern of your fingerprints forms rather in the way that wrinkles form over cooling custard. At most you may predict, say, the fineness of the wrinkles and their general pattern. Fingerprints are just one example. Many of your features could mark you out from any clone. Your genome only controls gross characteristics such as the rates at which the skin and its underlying attachments develop and grow. Even if there is no way for genes to specify everything exactly, there is no way the genome could carry enough information for the details. If our genomes had to specify everything, we would not be here. But, while the consequences of imperfect specification are usually trivial, they may have more serious effects. A minor distortion of a blood vessel could give poor blood flow or an aneurysm, and the branching and interconnection of brain cells affect mental aptitudes. That is why, though bright parents tend to have bright children, dimmer ones may have a child genius and vice versa.

The turtle lives ‘twixt’ plated decks

Which practically conceal its sex?

I think it’s clever of the turtle

In such a fix to be so fertile

            The poet Ogden Nash was right about the turtle’s external ambiguity and fertility, according to Grzimek’s Animal Encyclopedia (Van No strand Reinhold). Turtles are not only enthusiastic breeders; they also have external sexual characteristics that often make it hard for creatures other than turtles to determine which is which. The male is sometimes distinguishable by an indentation or curvature in its plastron, or lower shell, which fits over the back of the female; females have a flat or convex plastron.

To fertilize female's eggs, the male turtle conceals a sexual organ inside the cloaca, or waste removal chamber. The male positions itself over the female and often grasps the upper shell, or carapace, with its claws, then curves its tail until the vent contacts the female's vent; the penis emerges for often fertilization. The often dozens of eggs develop internally and are then usually laid and buried in sandy soil.

Fertilization is sometimes preceded by elaborate courtship rituals, with hours of demonstration followed by a few minutes of copulation. The female can store sperm to fertilize its eggs, sometimes years later. 

A thin coating of oil on the surface of the spider's legs prevents them from sticking to their own web.

Spiders have 3 pairs of spinnerets (silk spinning apparatus) located beneath the hind tip of their abdomen. Silk, made up of proteins, secreted by the silk glands, and are made into fibres as thin as a thousandth of a millimetre. The threads we see are actually a bundle of these fibres. The proteins are water soluble when secreted, but when made into a fibre, some Physical and chemical changes take place, and so, after a while the fibre becomes tough and does not dissolve in water. In fact, it becomes stronger than a steel wire of the same thickness. Hence, the spider silk is also used to make bullet proof vests.

To construct a web, the spider first lays the radical threads. These resemble the spokes on a wheel and they radiate from the centre or hub of the web. The radial fibres are then connected by spiraling threads. There may be 10-60 turns in a web. To capture the insects, spiders scatter small glue droplets throughout. The glue droplets remain sticky by absorbing moisture from the air. They also increase the capacity of the web to resist wind forces.

While some spiders do not place glue droplets around the central area of their web so that they can wait there for the prey, a few others attach a separate 'signal thread' from the web’s centre to a nearby place (not on the web) where it can conveniently relax. When the insects get stuck to web, spiders sense the vibrations and leap on the prey.

To help avoid being caught in their own webs, the spiders secrete oil and coat it on their toes. One can test this by dipping a spider’s legs in ether, an organic solvent, which dissolves the oil. If the spider is returned to the web after the dip, it will be caught in its own web.

Scorpion’s venom acts on the nerve tips and roots whereas snake’s poison acts on dendrites and axons of the nerves. As defence and prey capture are the sole aim of these and other animals and insects, it is the purpose on hand that determines venom’s composition and type.

 Cobra venom consists of 10 different enzymes, several different types of neurotoxins, cardio-toxins, cytotoxins, dendrotoxins and fasciculins (for example, lysocephalins, lysolecithins which are phospholipids). Snakes of the elapidae family (for example cobras, kraits and mambas) have venoms that kill primarily through neuro-muscular paralysis. It contains 60-75 amino acids and target nicotinic cholinoceptors in the muscle cell membranes which are sensitive to a chemical transmitter, acetylcholine. (Acetylcholine is released from nerve endings in response to an electrical impulse in the nerves.) The amino acids in snake’s venom block the junction between the nerves and the muscle. Scorpion’s venom consists of an arsenal of toxic compounds which contain 37 amino acids called charybdotoxin.

            When a scorpion stings these acids incapacitate the nerve cells causing severe pain, by rigidly binding with sulphur bonds unlike the snake’s toxin which binds by a ligand series. Moreover snake’s venom is digestible, but scorpion’s venom is not          

Snakes are stone deaf, yet they respond to charmers’ mahudi. Though this appears a contradiction the fact is that snakes actually respond to vibrations produced on the ground and not to the sound waves produced by the mahudi, in the air. Snakes do not have ears; instead they have a long bony rod called columella auris that extends from fenestra oval is to the quadrate bone. It is this bone which helps the snake to detect the vibrations.

One would have noticed that charmers first hit the ground with the pipe before playing it. The snake picks up the vibrations on the ground thus caused and comes out. When the snake charmer sways his pipe as he plays, up, down and forward, the snake too sways its body in the direction of the mahudi, only considering it as an object to be targeted and not because it follows the music. In some experiments, snakes have responded even without the ground tap because in these cases the tin in which the snake is housed is made to vibrate by the music (air waves) generating from the pipe. 

The subject is being studied by Dr. Julian Vincent of Reading University’s Biomimetics Centre, southern England, who hopes to learn the secret and adapt it for clothing.

 The idea of looking to nature for such answers is steadily becoming a science itself. The bones in a bird’s wing are powerful but incredibly light while spider silk is as strong as steel (in proportion) but enormously elastic and recyclable. “In nature the good designs eat the bad”, said Dr. Vincent.

            In Antarctica where temperatures reach minus 40 degrees Celsius, emperor penguins congregate to breed and produce a single egg which the male incubates. The penguins huddle together not eating for four months until the egg hatches.

            During that time they lose almost half their body weight. About 80 per cent of their insulation comes from their feathers which, it has been discovered, grow all over their body leaving no skin exposed.

            On land the birds use tiny muscles to erect the feathers forming a barrier of still air around their bodies. At the base of the feather is down, in which air is trapped close to the skin in small pockets. Each fiber has along its length a number of spikes, or nodes. When fibers from neighbouring plumes push into each other, the nodes buckle into loops producing a dense structure of tiny air pockets. By trapping the air, the penguin’s heat loss is drastically reduced.

            Dr. Vincent hopes to copy the essential features of the penguin’s insulation system and reproduce it in clothing.

Stings of insect group animals like mosquito cause skin lesions by direct effects of the insect parts or secretions which cause irritation. When the insect parts or secretions are retained for some time they tend to cause hypersensitivity responses. The immediate itching effect on the site of the bite is the appearance of urticaria or inflamed papules. Histologically the lesion shows a wedge shaped per-vascular infiltrate of the lymphocytes, histocytes and eosinophils within the dermis. The first event of the inflammation is an increased blood flow to the bite area. This results mainly due to the arteriolar dilation. Another event is the increased vascular permeability which results in the accumulation of protein rich extra vascular fluid.

The major chemical mediator of inflammation is the histamine. It is widely distributed in the tissue, the richest source being the mast cells that are normally present in the corrective tissues adjacent to the blood vessels. Preformed histamine is present in mast cell granules and is released by mast cell de-granulation process which in response to the stimulus caused due to irritation at the site of the bite. This histamine causes dilation of the arterioles and increase vascular permeability of venules. This in turn causes venular endothelial contraction and widening of the interendothelial cell Junctions, where the extra-vascular fluid accumulates causing, inflammation.

 There are more than 1,200 species of mosquitoes but all of them do not feed on the blood of mammals. The three important blood feeders found throughout the world are Culex, Anopheles and Aides. Even in these species, only the female mosquitoes suck blood, while the males thrive on plant sap and honey from flowers. The blood when drawn enters the highly dilatable stomach of the female which uses it for reproductive purposes. At least one-fifth of a drop of blood is sucked at a time. If these female mosquitoes are killed, they bleed.  Unfed females and males do not bleed when killed.

Some sleep out of the water, and some may not sleep at all. The furred or hairy aquatic mammals in the Pinniped order (like seals) have a variety of interesting adaptations that permit them to spend a comparatively long time under water sometimes at considerable depths, according to the Encyclopedia of Mammals.

            However they rise frequently to breathe and emerge from the ocean to sleep, relax, molt, mate and reproduce on a sandy beach or rock above the water.

            The situation is less clear for cetaceans (whales) and sirenians (sea cows and manatees). The whales evolved from land animals that returned to the sea, millions of years ago.

Though whales come to the surface to breathe air into their lungs, they can spend a long time between breaths, up to an hour in   some species, and spend nearly all their lives under water. However, whales learned to hold their breath so well that they lost their involuntary breathing mechanism and must be conscious to continue to breathe. Not only would a reflex have to take care of breathing, he said, it would have to take them to the surface for air.

Also, the blow hole automatically closes and must be opened voluntarily by the whale. Whales would drown if they fell asleep or were knocked unconscious. Sea cows and manatees tend to live in warm, calm, shallow, vegetation-rich waters where they can float lethargically at or near the surface.   They have an extremely low metabolic rate, do not expend much energy to regulate body temperature and require little oxygen.

Manatees may sleep or rest supported by the bottom. When they hold their breath, large blubber deposits and natural buoyancy let them float at the surface and engage in a resting behaviour, though not an unconscious sleep. 

            Leeches, carnivorous or bloodsucking worms, live as external parasites attaching themselves to a host and sucking blood. Actually, land leeches feed only on the blood of mammals. These flattened ringed worms, measure from 5mm to 46cm in length and are equipped with sucking disks at both the anterior and posterior ends. In some leeches, the anterior mouth contains three toothed plates with which the animal pierces the skin of its prey.

            First, with its 3 jaws set with sharp teeth, it makes a Y-shaped incisor in the flesh. Its saliva contains substances that anaesthetize the wound area, dilate the blood vessels to increase blood flow and at the same time prevent the blood from clotting.

            Hence the victim is often unaware that he has been bitten until blood is discovered running from the wound. Also the site of bite is directly connected to the crop of the leech through its buccal system.

            In the crop or pouch, food can be stored for several months. Land leeches await their victim in damp vegetation poising one end in the air.

            Leeches were once used by physicians and barbers for bloodletting and are still used for this purpose in some regions of the world. In modern medicine, bloodletting is no longer practiced, but leeches continue to be used to relieve blood congestion in certain delicate operations, where such use is less likely to cause infection than other techniques, according to the encyclopedia.

Blood ingested by leeches is mixed with salivary juices containing an anticoagulant substance known as hirudin (which can be extracted and has been used in medicine to prevent blood clotting. It is employed as an anticoagulant in surgical operations and has been recommended for the prevention of phlebitis and post-operative pulmonary inflammations.

            Hirudin has been synthesized by recombinant DNA technique. The blood passes into a dilated, branched stomach, or crop, where it is stored for several months before being completely digested. A leech consumes about 3 times its weight in one feeding and then subsists for months on the stored food.

  Clotting is a remarkable property of blood. Certain substances promote coagulation (procoagulants) and others inhibit coagulation (anticoagulants). Clotting depends on the balance between procoagulants and anticoagulants in the blood. While the anticoagulants normally predominate, the procoagulants get activated and cause clotting when a blood vessel ruptures. Injury to a blood vessel causes a complex cascade of reactions leading to the formation of a clot. The control of clotting is a major medical concern. Heparin, the most frequently used natural anticoagulant, is administered before and after surgery to retard clot formation.

 The prevention of clotting is also a concern of blood-sucking organisms, such as leeches which have been used (and misused) in the medical profession for centuries. The active agent responsible for the anticoagulative effect is a protein called hirudin secreted from the salivary glands of Hiduro Medicinalis.

   Hirudin is a small, highly active protein with a molecular weight of 7000 Daltons. It specifically binds to thrombin, the enzyme that catalysis the final step of clotting. It forms a stable 1:1 non-covalent complex with thrombin thereby inactivating it and preventing clot formation. Consequently, leech bite, though a minor wound bleeds quiet freely. It is the most potent thrombin inhibitor known because of exceedingly low dissociation constant of hirudin-thrombin complex. The x-ray structure of the complex of hirudin with human thrombin has revealed that numerous interactions are responsible for hirudin’s tight binding to thrombin.

  Hirudin is of great medical interest, not only because of its high specificity for thrombin, but because it possesses a number of characteristics which make it superior to the currently used blood anticoagulants such as heparin.

The breeding season of house fly, Musca nebulo, is from March to October in most of India. In the course of the breeding season, a single female may lay eggs 4 to 6 times and each time each female lays 120 to 160 eggs. They lay their eggs in clusters on compost, waste heaps, manure and dung. The conditions required for laying eggs are moisture and favourable temperature. The eggs hatch in 8 to 24 hours depending on the temperature. The whitish larvae moult twice to become the familiar white maggots in 5 to 7 days.

The maggots transform into quiescent reddish brown pupa from which the adult flies emerge after 5 days if the temperature is optimum. Summer provides all the favourable conditions. So the flies mate and lay a number of eggs and suddenly increase their population within 15 day.

    Firefly also known as lightning bug is the common name for about 100 species of insects found throughout the tropical and temperate regions. Fireflies are soft-bodied insects measuring` from a few centimetres to about a few tens of centimetres. They have generally dark brown sheath-like front wings covering the flying wings at rest, yellow or orange markings and luminescent glands located on the underside of the rear abdominal segment. Both sexes emit intermittent light signals often seen in meadows on late-spring and summer nights, to attract mates. The luminescent larvae and females of some species are also called glowworm. The firefly emits light by allowing oxygen, breathed through its abdominal tracheae, to combine with a substance called luciferins. The fly also controls the timing and duration of the flashes, for example, to attract its mates. The unique characteristic of the fly is that it emits light without producing heat.

            The process of emission of ‘cold’ light by living beings by various enzymatic reactions is termed bioluminescence or chemiluminescence. The glowworms, Lampyris noctiluca, are bioluminescent insects. The light produced may either be extracellular (outside the cells) or intracellular (inside the cells). Luciferin, a substance present in glowworms gets oxidized in the presence of an enzyme called luciferases to give light and carbon dioxide. Emitted light may be blue, green, yellow, red, orange or a combination of these colours.

            The intensity of the colour also differs among various animals. It is said that when 10 Phyrophorus noctilucus are kept in a glass bulb, one can read printed pages comfortably.

            The animals use this cold light to procure food, to escape from predators, as warning signal and as mating signal. During photosynthesis radiant energy (light) is converted into chemical energy (starch) by plants. But during bioluminescence the chemical energy in the body is converted into radiant energy, without raising the temperature in the process.

            In glowworms, a combination of adenosine tri phosphate (ATP) and oxidative energy is used in a set of reactions that convert chemical energy into light energy. Generation of light flash requires activation of luciferins by an enzymatic reaction with ATP in which a pyrophosphate cleavage of ATP occurs to form luciferyl adenylate. This compound is then acted upon by molecular oxygen luciferases to bring about the oxidative decarboxylation of luciferins to yield oxyluciferin. The intermediate step of this reaction is accompanied by emission of light. Luciferin is then regenerated from oxyluciferin subsequently.

            Many factors are involved in hair loss. The exact cause is not known but scientists think that stress and severer illness, can cause hair to fall out (Chemistry in Britain). Iron deficiency or pregnancy can cause hair loss in women. Some cases are potentially reversible. For example, hair may re-grow once the illness has been cured.

            Scientists also know that the largest cause of hair loss in men is genetic in origin. Alopecia androgenetica, which creates male pattern baldness in men and general thinning of the hair in women, is an ageing phenomenon. They do know that the mechanisms involved in hair loss are complex and mediated to some extent by the male hormone (androgen).

            There are also suggestions that genetic hair loss is just an ageing process where the chronological age of an affected individual becomes desynchronized with that of the hair follicles.

            The male hormone, testosterone, is pivotal in the physiology of balding. It includes any hairs that are predestined to stop growing. Treating suffers with testosterone can stimulate dormant hair follicles into growth, but giving testosterone to men cause unwanted side-effects.

            In genetic hair loss, changes occur in all three fundamental hair variables; hair density (number of hairs per square centimetre0; the proportion of hair follicles in the active growth phase and the hair diameter per unit area. Initially, there is a reduction in the period of active growth, which results in an increase in the number of hairs being shed from scalp. This is followed by a reduction in hair diameter as the hair follicle gradually becomes smaller. Finally, the number of productive hair follicles decreases, reducing the meaningful hair density.

            The principle mechanism of genetic hair loss appears to be “localized tissue sensitivity to normal androgen concentrations.” While the metabolic processes are far from clear, an important candidate is the enzyme 5-alpha-reductse inhibitor, which catalyses are reduction of testosterone to dihydrotestosterone (DHT).

 The object of blinking of our eyelids is to keep the front of the eyeball clean. Blinking is done by means of muscles in the eye lids and the cleansing by tears. The tears are secreted in a little gland and carried along to the eye and when our eyelids open and close the tears are poured over the front of the eye and they wash away any particles of dust or any other harmful substances.

            Some animals like the snake for example, do not have eye lids and hence cannot blink. But there is a hard film or scale over the eyes to protect them from dust and injury.