B u B b L e p e d i a

Region 13

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Region 12

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Region 11

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Region 10

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Region 9

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Region 8

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Region 7

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Region 6

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Region 5

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Region 4

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Region 3

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Region 2

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Region 1

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What are eyes made of?

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Eyes - the outer shell of the eyeball is made up of three coats: the fibrous tunic, the uveal tunic and the retina. The fibrous tunic is tough and elastic. It is opaque at the back, where it is called the sclera, and transparent at the front where it is known as the cornea. The uveal tunic is so called because of its similarity to a grape (Latin: uva). It contains the choroid membrane which supplies blood to the eye. The retina, or innermost coat, is an extremely delicate tissue and is only a fraction of a millimetre thick. Its inner layers carry blood from the central artery to the central vein. At the centre of the eye is a circular opening, the pupil, and immediately behind it is the crystalline lens, which consists of a great many transparent fibres arranged in sheets like the layers of an onion and enclosed in a clear, elastic membrane, the capsule. The perfectly smooth surface of the lens is curved and it is suspended by a number of delicate threads.

What are double joints?

2012-02-17T10:52:00.000-08:00

Double joints - is a capable of an unusual amount of movement, usually backward movement. Perhaps the most common demonstration of a double joints is to see someone bend his thumb downwards and backwards until it touches the inside of his forearms. A joint is a meeting place between different bones of the skeleton. Joints are divided into fixed and movable ones. Movable joints may be divided into gliding joints, such as the wrist and ankle; hinge-joints, like the elbow and knee; and the ball and-socket type such as the shoulder and hip.

Why are pebbles on a beach round?

2012-02-17T09:08:00.000-08:00

Pebbles - are to be found on a beach are invariably round and smooth owing to the constant battering they have received from the sea. Originally pebbles were part of much larger rocks, but various natural phenomena, such as earthquakes and volcanoes, have gradually broken them down. Caught in the movement of the sea, and constantly rubbed against other hard materials, the pebbles finally lose their irregularities and present a smooth round surface. Many of the rocks today will be pebbles in thousands of years time, and many of today's pebbles will eventually be turned into sand by the constant, wearing action of the sea.

Why is it possible to estimate the age of fossils?

2012-02-14T12:42:00.000-08:00

Age of fossils - it is possible to estimate the relative age of fossils, that is weather they came before or after a particular period, because most fossils are found in sedimentary rocks. These are rocks made of sediment which has been compressed or cemented together in layers. Older rock layers, or strata, are usually at the bottom. So each layer is younger than the layer below it an older than the one above. Fossils may be present in igneous rock (hardened the volcanic lavas)and metamorphic rocks (formed by pressure and heat within the earth) but they are usually destroyed. Telling the age of fossils in terms of years, or absolute time, is a much bigger problem. But scientists use several methods. The tree ring method, counting annual growth rings, can give a scientist a reasonably accurate date back to about 3,000 years ago. The varve method, based on counting the annual layers of sand and clay deposited in a lake, bay or river by melting glaciers, can be used for deposits less than about 15,000 years old. Similar calculations based on the rate of sedimentation, erosion, salt accumulation etc. have been successfully applied to very much older rocks. The third method is concerned with radioactive decomposition and is based on actual changes in some of the rock elements or in the fossils themselves. Radioactive uranium gradually changes to uranium lead, radiocarbon to nitrogen and so on. From proportion of uranium lead to uranium in the rock we can date the oldest rocks and fossils, nearly 3,000 million years old.

Why does the Mediterranean Sea look blue and the Atlantic Ocean look green?

2012-02-10T11:08:00.000-08:00

Mediterranean - the blueness of the Mediterranean and the greenness of the Atlantic Ocean are mainly due to the different amounts of sunlight reaching the water's surface. Owing to their different geographic positions, the Mediterranean is far more often directly exposed to sunlight than the Atlantic. The blue colour of the sea is the result of the molecules of light scattering in the water. The green colour of the Atlantic comes from decayed plants on the ocean bed. When these aquatic plants decompose, yellow pigments are released. It is this yellow, mixed with the already murky blue of the Atlantic that creates the characteristic green colour of that ocean.

What is a muscle?

2012-02-10T11:05:00.000-08:00

Muscle - is the body tissue which, because it has the power of contraction, enables the higher animals to move their bodies. Muscles are divided into two great groups, voluntary and involuntary, the former being controlled by the will, while the latter act independently. Most voluntary muscles are attached to the skeleton and range in size and shape to suit the particular jobs they perform. They can get into action within a few hundredths of a second, exert an enormous pull on the bone to which they are attached and, if necessary, support 1,000 times their own weight. Involuntary muscles include heart muscle and the muscles of the digestive system, and the fibres of which they are composed are very much smaller than those of voluntary muscle. Because of its exceptionally rich blood supply, muscle is the most infection-free of the body's basic tissues. If it is over-taxed it tires and will stop contracting altogether, but if used normally will give little trouble.

Why are many Japanese trees small?

2012-01-28T02:13:00.001-08:00

Japanese trees - many Japanese trees are small because they are dwarfed by the Japanese art of bonsai. This art consists in training and growing dwarf trees as symbols of the Japanese ideal of the immersion of the self in nature. This ideal also finds expression in their poetry, the tea ceremony and flower arranging. The tiny trees express quietness, beauty of shape and line, and the changes brought about by the seasons. They must look old, with a sturdy yet shapely trunk which has bark of an interesting colour and texture, and well-exposed roots. There must also be a proper feeling of scale. This means short needles on deciduous trees, and small flowers or fruit. Lastly, there must be open space between branches and between masses of foliage.

The word "bonsai" means tray planted. The art goes back more than 1,000 years. It originated in China and spread to Japan in the 12th Century. During the 19th Century many Westerners came to admire bonsai. But it was not until the end of the Second World War that it became really popular in the western world. Bonsai societies were established in many countries, and many Japanese families now maintain a flourishing overseas trade.

Why do plants flower at different times of the year?

2012-01-28T02:12:00.001-08:00

Plants in flower - the flowers appear at the times most suited to the production of seed for the continuation of the species. Before seed can develop the flower must be pollinated. This means that the dust-like pollen produced by the stamen of the flower must be transfered to the stigma of the ovary. Pollination is brought about by various means. Most plants are pollinated by insects and, therefore, flower at the time when the insects are active. The flowers may have revolved a particular colour and scent to attract particular varieties of insects. Five classes of insects visit flowers-Hamiptera (bugs), Coleoptera ( beetles), Dipters (flies), Hymenoptera ( bees) nad Lepidoptera ( moths and butterflies). Pollination by birds is widespread throughout the tropics and some animals, such as bats, also play a part.

Wind-pollinated plants include all the conifers, grasses, sedges and rushes, and many forest trees which tend to flower either early or late in the season when the chance of wind is greater. If pollination by some other agent has failed, self-pollination will often take place at the end of a flower's life. This is usually brought about by movements of the stamens.

Why don't trees grow on mountain tops?

2012-01-28T02:11:00.001-08:00

Trees on mountains - trees do not grow in mountain tops either because the situation is too exposed, or because the soil is too thin or too frozen to allow their roots to draw nourishment from the ground. In most mountainous areas there is usually a clearly marked timberline, a boundary above which there is no tree growth. Sometimes the height of the timberline is dictated by local climatic or soil conditions, but as a general rule the boundary gets lower as the distance from the Equator increases. In the far north and south the cold is so intense that it is quite impossible for any trees to grow, and the timberline is therefore at sea level.

A range of mountains on or near the Equator, like the Ruwenzori range in Africa, can be divided into different belts of vegetation according to the types of trees growing at its base and at various heights up its slopes. Similarly the belts of vegetation change according to the distance from the Equator. The first belt is the tropical or rain-forest region where it is hot and trees grow rapidly. Next comes a hot dry belt where few trees grow because there is so little rain. This is followed by the deciduous or warm and temperate belt, and by the coniferous belt, with very cold winters but fairly warm summers. Then comes the timberline, beyond which trees cannot grow, and finally the regions of permanent ice and snow, where no vegetation at all can live.

When does a tadpole become a frog?

2012-01-28T02:09:00.001-08:00

Tadpole - frogs egg become tadpoles within two weeks of being laid in the water, but tadpole may take anything from two months to three years to change completely into frogs. The time taken seems to depend on the environment. Tadpoles will generally develop faster in warmer waters. Also the more advanced species of frog have simplified and shortened the process of transformation. Tadpoles, like fish, breathe through gills. They develop lungs during the change-over, gain legs and lose their tails. The menu changes, too from plants to very small insects.

When does the tuatara hunt?

2012-01-28T02:06:00.001-08:00

Tuatara - is the only survivor of the beak headed order of reptiles, called Rhynchocephalia, that goes back to the time of the dinosaurs. It hunts by night and its prey are insects. Like the coelecanth, a prehistoric fish that still survives, the tuatara is almost the living fossil. It can now be found only on some of the small islets off the coast of New Zealand, having been exterminated from the mainland. It basks in the sun during the day and burrows into the soil for safety. It is covered in scales and grows to about 30 ins.

Where do spiders keep their webs?

2012-01-28T02:04:00.001-08:00

Spider's web - a spider does not have a ready made web. She spins one. If you are lucky, you may be able to watch the female spider doing this. The material that makes the thread for the spider's web is a liquid which she produces from tiny spinning tubes. These spinning tubes are to be found on small lumps on her body, known as spinnerets. As soon as the liquid comes into the air, it hardens and changes into thread. When the spider sets out to spin a web she first uses a tough thread to build an outer frame in which she fits spokes, as in a wheel. Next she starts from the hub to weave a spiral crossing the spokes about five times, just to keep them in position. Then she begins again at the outside rim to spin a complete spiral with finer silk, cutting away the "scaffolding" as she nears the center. Finally she constructs new support-lines for the finished web. When the spiders move they spin out lines behind them. These are known as the "draglines", and spiders use them as anchors. They do this by pressing their spinnerets against small objects like pebbles or plants. These are the most important threads of all. Spider use their webs for trapping flies and other insects to eat. So, besides being beautiful to look at, spider's webs are vital to them as food providers.