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What is fire made of? What is its atomic structure? What causes things to burst into flames in the first place and why can’t all materials be made to produce flame?

Fire involves a chemical reaction between fuel and atmospheric oxygen.  Once initiated it is self-sustaining, generates high temperatures and release a combination of heat, light, noxious gases and particulate matter.

The visible flame is the region in which this chemical process occurs and so flame is essentially a gas phase phenomenon. For flaming combustion to occur, solid and liquid fuels must be converted into gaseous form.

 For liquid fuels this is achieved by evaporative boiling. For solid fuels, the solid is chemically decomposed through the process of paralysis to generate volatile gases.

A flame is a region containing very hot atoms. At high enough temperatures all atoms will emit energy in the form of light as their electrons, which have been prompted to higher energy levels by absorbing heat energy, fall to lower energy states. Because this light is emitted in discrete quanta according to the relationship E= hf (where E=energy, h=Planck’s constant and f= frequency), flame colour is related to the magnitude of the energy quantum which is transformed to light.

This can most easily be seen with a Bunsen burner. A Bunsen burner that has a choked air supply burns cool, the light emissions from carbon atoms are relatively low in energy and appear more red or orange.

However, when the Bunsen is allowed air so that combustion is complete, the flame is hotter and the light emitted is of a higher energy and frequency and appears blue.

The luminescence of a flame is only of the story. The structure of the flame region is important to understand too. The flame area in a normal combustion environment, such as an open-air bonfire, is structured by convention currents which form as hotter, lighter air rises and allows cooler fresh air to replace it.

It is this channeling effect and movement of air that shapes the dancing flames. It is interesting that in space, in zero gravity, the hotter and cooler air cannot move by convection, so flames take on weird shapes and may be stifled by their own combustion products. 

Why don’t identical twins have identical fingerprints?

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.

How do turtles reproduce?

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. 

How do spiders manage without getting caught in their own web?

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.

Why is the sting of a scorpion more painful than that of a snake sting? What are the chemicals in their poisons?

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          

Can snakes hear? How do they respond to charmers’ mahudi?

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. 

How do penguins survive and breed regularly in Antarctica despite the chill?

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.

Why do we get a bulge on the skin after a mosquito bite?

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.

When killed, some mosquitoes bleed and some do not. Why?

 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.