My Science School

Before you shout out an answer, it is not to store water. It may be quite true that camels can store a huge amount of water. They can drink over ninety litres in just ten minutes. But they keep this elsewhere. Humps are stores of food - well, fat actually.

Out in the desert with nothing to eat or drink for days on end, a camel can live off the water stored in its belly. In the same way, the fat in its hump provides the nutrition it needs. When camels are fit and healthy their humps are large and firm. But by the end of a long desert journey, when the reserves of fat have been used up, the humps are flabby and may droop.

 

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Millions of years ago when the earth was still young, the land that now forms the Himalayas was an ocean floor. A lot has changed since then and today the Himalayas are the world's highest mountains. They rise to a peak at the summit of Mount Everest - not far short of nine kilometres above sea level. So what turned an ocean floor into a mountain range? The answer is a huge build-up of pressure.

The earth's surface is formed from gigantic rafts of land, known as tectonic plates. Sixty million years ago the plate on which India lies started moving. It moved northwards towards the plate that the rest of central Asia sits on. In between India and Asia at that time was the sea. And when the two plates crashed together the ocean bed under the sea was crushed. As the Indian plate kept pushing north, the sea floor buckled and folded. One layer of rock was squeezed up and piled on top of another. After sixty million years the effect is dramatic. The sea has long since disappeared and in its place stands a mighty mountain range separating India from the rest of central Asia. The process is still going on and experts think the Himalayas are being pushed slowly upwards, perhaps growing as much as five centimetres a year.

And what about the sea shells? Buried in some of the rock high up in the mountains, climbers have found the remains of shells that once lay on the floor of that ancient sea.

 

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Most of them go to the big fly heaven in the sky. In that case, you may say, how come there are so many flies the following summer? The point is, they do not all die. A very few survive. Some last out the winter as adults. Others make it through to spring as unformed flies known as larvae or pupae.

As soon as the weather turns warm again, the surviving flies set about making up their numbers. And they do this at a staggering rate. One estimate is that a single pair of flies can produce over 300,000,000,000,000 offspring in one season. That is why there are so many flies around the following summer.

 

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Crickets are very sensitive to air temperature – so sensitive that they act as living thermometers. Crickets are cold-blooded and their bodies work faster or slower depending on how hot or cold the air around them. This relationship between activity and temperature I very accurate. By doing a little mental arithmetic it is possible to calculate the temperature in Fahrenheit by counting a cricket’s chirps.

There are two ways of doing this. You can count the number of chirps in one minute. Then take away forty. Then divide by four. And finally add fifty. The number you end up with is the temperature in Fahrenheit. That is the most accurate way.

A simpler, but rougher, method is to count the number of chirps in fourteen seconds and then add forty.

In both cases you will have to do another calculation to convert the Fahrenheit temperature, if you want it in Centigrade. To do this subtract thirty-two from the Fahrenheit total. Then divide by 1.8. Your answer will be the temperature in Centigrade.

 

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Mushrooms belong to the group of plants known as fungi. They are different from other plants because of the way they grow. Instead of growing from seeds, fungi grow from very simple organisms called spores. The hit rate of successful spores is very low. So fungi have to produce literally millions to be sure that some will grow into new plants. One large mushroom can produce 16,000 million spores, but only a few of these will germinate and grow into new mushrooms.

If a spore lands on a suitable piece of ground, it sends out fine branching threads known as hyphae. They form a dense network underground. Small white bumps grow from this and eventually appear on the surface as mushrooms. Once the new mushrooms open out into their familiar umbrella shapes, they start shedding spores of their own to continue the growing process.

Mushrooms are delicious. Other varieties of fungi can be eaten too. Be warned, however. There are some that are terribly poisonous. So we should not eat any of them until we have identified that they are safe.

 

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Zebra crossings on the road have black and white stripes in order that we can see them clearly. So you might think that having black and white stripes would make a real-life zebra a sitting target for animals that hunt zebras lived on their own, you would probably be right. But nature is cleverer than that. Zebras move about in herds. So when they are grouped together, their colouring makes a confusing pattern of mixed black and white stripes all moving in different directions at the same time. Any predator trying to single out one particular zebra for its next snack would get cross-eyed looking at that lot. That is what the zebras hope. As long as they keep together, their strange camouflage gives them great protection.

 

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The smart answer is by touching you! But when you find out that some of the largest of these fish can knock a man over with their electric shock, the question deserves a fuller answer.

The idea of fish producing electricity as strong as this is amazing, to begin with. Yet several species have this capability. Some of the smaller ones can produce currents able to light small bulbs while some of the larger fish have powered small electric motors for some minutes before getting tired.

Some fish have generating organs in their heads. Others have them on either side of their tails. These are supplied with nerves from wither the brain or the spinal cord. In all cases the parts of the fish that produce electricity are really modified muscles. In brief bursts, however, they provide a very useful weapon. Enemies can be frightened off with a quick electric shock. And when the same shock is used to stun small fish, the electric fish does not have to look any further for supper.

 

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One of the most unnerving things about a snake is its steady gaze. If you have ever had those unblinking eyes fixed on you, even through a zoo window, you will know what I mean.

For a snake, its penetrating stare is a terrific way of scaring prey. Some animals are turned rigid with fright when they see a snake’s eyes, glaring at them. But the reason they cannot blink is not quite as calculating. Snakes cannot blink because they do not have eyelids. They cannot even close them to go to sleep. Instead they have a permanent glassy stare that can turn most creatures cold with fear.

 

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Some plants do. They do not eat large animals, which is just as well for us. But they do trap insects and consume them. Insects provide these plants with their food. One of the most well known is the Venus fly trap. Any insect unlucky enough to crawl in triggers a mechanism in the plant which snaps it shut. The insect is trapped inside. Then juices in the plant get to work and dissolves it.

The Pitcher plant is another insect eater. It is shaped like a jug, or pitcher – which is how it got its name. Inside the plant is so rough and uneven that a trapped insect cannot crawl out again. In the end it drops exhausted to the bottom of the plant, where it is digested by the plant’s juices.

 

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Lizards have a brilliant way of escaping from predators – detachable tails. It sounds crazy, but that is what they are. A lizard’s tail has a special weak link. If it is unlucky enough to be caught by the tail, this link snaps. The lizard escapes and the predator is left with just a short piece of tail in its jaws. The stump of tail left does not take long to grow back to its correct length, and as nature intends it to snap, it does not cause the lizard any real harm. One kind of lizard called skink goes a stage further. It has a tail which thrashes around when it is pulled away from the rest of the body. This can be really confusing for a predator, which often, mistakes the bit of tail for a living creature. And while it is puzzling that out, the skink has bags of time to make a run for it.

 

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 Amazingly, yes they can. Some kinds of primitive plants living in water have very small tentacles which they thrash around in the water to propel themselves along. Looking at them, you might they were animals, not plants. But even ordinary plants are on the move all the time – only very slowly.

Roots burrow into the earth in search of moisture. Tendrils reach out for something to cling to and climb. When they find a support, they quickly curl round it and soon become firmly attached. Flowers turn towards the sun. The sunflower even has an Italian name meaning ‘turning with the sun’, because it follows the sun round during the course of a day. And many flowers, like the daisy, open their petals in the morning when the sun shines on them, and close them again at the end of the day, when the light fades.

 

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When a dandelion flowers it has a bright yellow head. Gardeners proud of their lawns know this to their cost. To them, dandelions are weeds. The flower stays like this until the whole head has matured. Then it closes up again, to return to the shape it had as a bud. Sometimes it is called a swine’s snout, because it looks like the snout of a pig.

But inside, big changes are taking place. The dandelion’s seeds are growing. When they are all ready, the swine’s snout turns into a snowy-white puff-ball of seeds topped by tuffs of hair. This replaces the yellow flower on top of the stalk. There the seeds wait for the breeze to blow them free, so that they can float off to a new piece of ground and begin growing another dandelion. That is why gardeners are not very fond of them.

 

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Deep down in the oceans it is pitch-black. You cannot see a thing without artificial light, because sunlight cannot penetrate further than 460 metres below the surface. This could be a serious problem for fish living so deep, if they did not have lights of their own.

Some, like the angler fish, use light to catch their prey. The rat-tail fish sends out a cloud of light to dazzle an enemy while it makes a speedy getaway. Then there are those who use light just to keep in touch with friends and find a mate. They have ‘recognition lights’, rather like ships.

The light produced in these fish is like no other light on earth. For one thing, it’s cold. Almost every other sort of light we know of produces heat. Being cold makes it very energy efficient. Some fish produce their light by mixing chemicals with a little oxygen from their blood. These meet in glands in the fish’s skin. The chemicals form a combustion and light is produce in the gland, which turns into a lamp.

In other oceanic fish bacteria produce the light. The bacteria live and feed on tissue in the fish’s skin, which the fish is constantly replacing. However, the bacteria help the fish by producing substances that glow with bright light. So while the fish helps them, they help the fish.

 

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There may not seem a lot of point when flying forwards is so efficient and presumably much more useful. But, yes one species can – the humming-bird. These are tiny little birds. The bee humming-bird from Cuba is the world’s smallest bird. From beak to tail it is only 57 millimetres long. And it only weighs 1.6 grams.

Humming-birds get their name from the phenomenal speed at which they beat their wings. This is so fast that little birds can hover like a helicopter while drinking nectar from a flower. And their wing speed also lets them fly backwards when they feel like it.

 

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Olive branches have been important symbols for thousands of years. Brides getting married in ancient Greece used to wear or carry olive garlands, just as present-day ones carry orange blossom. Winners at the ancient Olympic Games used to be rewarded with a crown of olive too. The story goes that the goddess after whom Athens was named presented the city with an olive branch. It has been a mark of peace and plenty ever since.

Other parts of the ancient world thought olive branches were important too. In the story of the Flood, the first sign of life as the waters went down was an olive leaf. Noah let a dove out of the ark to see what it could find, and back it came with an olive leaf – a sign that God was restoring life to the drowned world.

 

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