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Sunday 23 December 2012
Wednesday 25 May 2011
Origin of life
Origin of life
Human has been in search of possible extra terrestrial life for quite a while and has invested considerable effort in it. But how life began on our home planet earth is still riddled with mysteries. Different theories have been framed to solve this mystery. They only give some possibilities. The possibility apart, the evidence obtained so far tells us about when the earliest form of life existed. Yes, existed. But not pretty certain about exactly when it did originate.
When:
Evidence indicates that all plants and animals alive today have neither popped up from nowhere, nor dropped from the sky altogether. And even when the earliest form of life did originate it took thousands of million years to evolve into the forms we see now around us. All the plants and animals, known and unknown to us, has come into being through this step by step process. Called 'evolution', this process has given birth to different forms of life at different stages.
As life did evolve, however, creatures gradually developed hard parts and provided a record of their existence in the form of fossils. A study of the earth's age and the dating of fossils discovered from all over the planet have also helped us graduate the time scale along which life has flowed.
These fossils are the remains of prehistoric animals and plants or bear some direct evidence of their existence. They may be bones or shells of animals, imprints of leaves and stems of plants, or just trails or borings made by worms in wet mud or sand that was later changed into rock. But getting secured in such a dramatic way is only a game of chance for the dead animals. There may still be many which did not happen to be fossilized. This possible slippage may leave a gap in a series of evidences.
The oldest fossils are probably those of algae, one of the simplest form of plants. These date back to some 2700 million years. Meanwhile, the oldest rocks discovered so far are about 3,000 million years old. Even, these rocks do not represent the total age of the Earth. For, the Earth is still older, about 5,000 million years old. This is revealed by studying the expansion of the universe over our time scale.
So what about the fossils that can carry us farther back into the first 2000 million years of the Earth's history?
Only against a background of about 3,000 million years of life does the process of evolution become clear. Science is concerned largely with the question of how this evolution happened.
How:
Studying the stages of evolution and dating the fossils we seem to be certain about one thing. That the earliest living things on Earth must have been very simple.
The first atmosphere of the Earth probably consisted mainly of methane gas(CH4),water(H2O),and ammonia gas(NH3). These substances contain all the chemical elements needed to make amino acids - the building blocks of protein, which is the basis of life. Laboratory experiments have already demonstrated that a mixture of these gases subjected to an electric discharge will produce amino acids. But the planet is not like the confined laboratory. And did the electric charge spark plugged the process.
Some scientists believe that lightning in the early atmosphere may have assisted in bringing about such a reaction. Again it was not a single lightning. What could be brought about in the laboratory in such with an electric discharge in a few minutes had taken thousands of years to take the final shape. Again from the amino acids to proteins is a long and complex step. And it is a still longer one from proteins to the simplest living cell. Once the cell comes up life got started. For it is the cell that forms the building block of life. Though it took quite a long period of time for even a single cell life to make their appearance on this planet.
This discovery makes it possible to imagine a series of steps by which the earliest life may have originated.
However, the odds are indeed many against having the proper circumstances for the beginning of life in this manner. But the conditions necessary for this development of life must have existed on Earth for perhaps as long as 2000 million years and over enormous areas of the Earth's surface. And there is no proof that life did originate in this or any other particular way.
The stages:
Irrespective of this controversy over the how and when of the origin, we are certain about one thing that has made life live on for so many years. We know, as life was born, it did die, sometime or the other. So what is it that makes life go on for years together? Or, rather say, for some millions of years together? It is the capability to reproduce itself, sometime before the death comes along. This ability is so unique that it makes life differ so much from the non-living ones. So between its birth and death it brings in another life to carry on the journey for yet another bunch of years. So life in every form has its parent and children. It's like a parent-child chain that keeps life roll on for so long. As time passes the chain gets longer and longer. And from the days of origin until these days life rolls on through this long chain.
But doesn't the chain break? Yes, it does. And it does when some of the children becomes too weak to carry on. But while it breaks. Some other children make themselves stronger
and more intelligent to carry on. They keep on adjusting themselves with the changing environments. Thus while some children carried on, some died, never to be born again. And
in between the new ones were born. Scientists and historians mapped out the forms of life those evolved, survived and died into extinction along side.
And indeed, the chief ingredient of this process of evolution is - time.
Based on this time scale the origin of primitive form of life can be said to have happened during the Precambrian Era. The oldest fossils so far known come from the Pre-Cambrian age. They include algae, fungi, jellyfish, worms, and some sponge-like animals. This lasted till some 570 millions years ago, said to be the starting point of the Paleozoic Era. This lasted for about 345 million years and is subdivided into Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian and Permian periods. Following these came the Mesozoic Era stretching for 160 million years. The Mesozoic comprise Jurassic, Triassic and Cretaceous period. Following these came the Cenozoic Era starting some 65 million years. This comprises the Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene and the Recent period starting only about a million years ago and is still going.
True, the earliest form of life is believed to have originated in the Pre-Cambrian era, life in our known form all started during the Cambrian period. By the Ordovician periods and most of the Silurian, many kinds of creatures thronged the shallow seas. These periods show a wide variety of plant and animal life, all of which show considerable advancement over creatures of the Pre-Cambrian and are far evolved from the first living things.
Life in its first form made its appearance in the sea. Possibly there were no living things on land then, and possibly none in the existing streams and lakes. In those days the land areas must have been unbelievably desolate wastelands of bare rock, sand, and mud, without any single form of life.
The oldest well preserved land plants come from the upper Silurian of Victoria, Australia. By Devonian time land plants had become common and are known from such scattered areas across the world. Still most were small and primitive. But by upper Devonian times there were forests of scale trees in some areas. These trees, which became extinct during the Paleozoic era, were the forerunners of those forming coal swamps of Pennsylvanian times.
The oldest undoubted fossil record of animal life on land from Devonian times when arthropods, including spider like and tick like animals were established. Several kinds of insects had appeared by the upper Devonian times.
Fishes were well established and flourishing by the Devonian times.
The Mesozoic times saw the real thrive of various reptiles, especially the dinosaurs. Even crocodiles also appeared during the Mesozoic era. Flying reptiles which form the earliest bird also appeared during this time in the Jurassic age. The close of Mesozoic saw decline of reptiles.
Cenozoic saw the plants and animals resembling those of today. Flowering plants and mammals dominated in this era. Of all mammals man belongs to the Primates and is the latest and most advanced addition in the biological pyramid.
While various forms of life have emerged, sustained and gone into extinction over the past, they are all the ancestors of any form of life doing fine here on Earth. These, including us, are what we see around.
The forms of life:
Let us now see what types of life forms we see around us. Are they only some creatures, intelligent or not, capable of moving around? Or, are they only capable of growing? Or, are they capable of growing and feeding themselves? Or, are they the forms in which all of these can be found?
Earlier it was the world of animals that was thought to be the only living forms on this planet.
And it is a matter of only the last few decades that forms, other than animals, came to be included in the world of living beings. And it was till recently that the bacteria, the fungus, and some forms of algae have come to be regarded as separate forms of life.
So based on this, today we know that there is a five-kingdom system representing the living beings around us. This is as opposed to the two kingdom system of plants and animals.
The animals, the bacteria, the fungus, the algae, and, the plants.
When:
Evidence indicates that all plants and animals alive today have neither popped up from nowhere, nor dropped from the sky altogether. And even when the earliest form of life did originate it took thousands of million years to evolve into the forms we see now around us. All the plants and animals, known and unknown to us, has come into being through this step by step process. Called 'evolution', this process has given birth to different forms of life at different stages.
As life did evolve, however, creatures gradually developed hard parts and provided a record of their existence in the form of fossils. A study of the earth's age and the dating of fossils discovered from all over the planet have also helped us graduate the time scale along which life has flowed.
These fossils are the remains of prehistoric animals and plants or bear some direct evidence of their existence. They may be bones or shells of animals, imprints of leaves and stems of plants, or just trails or borings made by worms in wet mud or sand that was later changed into rock. But getting secured in such a dramatic way is only a game of chance for the dead animals. There may still be many which did not happen to be fossilized. This possible slippage may leave a gap in a series of evidences.
The oldest fossils are probably those of algae, one of the simplest form of plants. These date back to some 2700 million years. Meanwhile, the oldest rocks discovered so far are about 3,000 million years old. Even, these rocks do not represent the total age of the Earth. For, the Earth is still older, about 5,000 million years old. This is revealed by studying the expansion of the universe over our time scale.
So what about the fossils that can carry us farther back into the first 2000 million years of the Earth's history?
Only against a background of about 3,000 million years of life does the process of evolution become clear. Science is concerned largely with the question of how this evolution happened.
How:
Studying the stages of evolution and dating the fossils we seem to be certain about one thing. That the earliest living things on Earth must have been very simple.
The first atmosphere of the Earth probably consisted mainly of methane gas(CH4),water(H2O),and ammonia gas(NH3). These substances contain all the chemical elements needed to make amino acids - the building blocks of protein, which is the basis of life. Laboratory experiments have already demonstrated that a mixture of these gases subjected to an electric discharge will produce amino acids. But the planet is not like the confined laboratory. And did the electric charge spark plugged the process.
Some scientists believe that lightning in the early atmosphere may have assisted in bringing about such a reaction. Again it was not a single lightning. What could be brought about in the laboratory in such with an electric discharge in a few minutes had taken thousands of years to take the final shape. Again from the amino acids to proteins is a long and complex step. And it is a still longer one from proteins to the simplest living cell. Once the cell comes up life got started. For it is the cell that forms the building block of life. Though it took quite a long period of time for even a single cell life to make their appearance on this planet.
This discovery makes it possible to imagine a series of steps by which the earliest life may have originated.
However, the odds are indeed many against having the proper circumstances for the beginning of life in this manner. But the conditions necessary for this development of life must have existed on Earth for perhaps as long as 2000 million years and over enormous areas of the Earth's surface. And there is no proof that life did originate in this or any other particular way.
The stages:
Irrespective of this controversy over the how and when of the origin, we are certain about one thing that has made life live on for so many years. We know, as life was born, it did die, sometime or the other. So what is it that makes life go on for years together? Or, rather say, for some millions of years together? It is the capability to reproduce itself, sometime before the death comes along. This ability is so unique that it makes life differ so much from the non-living ones. So between its birth and death it brings in another life to carry on the journey for yet another bunch of years. So life in every form has its parent and children. It's like a parent-child chain that keeps life roll on for so long. As time passes the chain gets longer and longer. And from the days of origin until these days life rolls on through this long chain.
But doesn't the chain break? Yes, it does. And it does when some of the children becomes too weak to carry on. But while it breaks. Some other children make themselves stronger
and more intelligent to carry on. They keep on adjusting themselves with the changing environments. Thus while some children carried on, some died, never to be born again. And
in between the new ones were born. Scientists and historians mapped out the forms of life those evolved, survived and died into extinction along side.
And indeed, the chief ingredient of this process of evolution is - time.
Based on this time scale the origin of primitive form of life can be said to have happened during the Precambrian Era. The oldest fossils so far known come from the Pre-Cambrian age. They include algae, fungi, jellyfish, worms, and some sponge-like animals. This lasted till some 570 millions years ago, said to be the starting point of the Paleozoic Era. This lasted for about 345 million years and is subdivided into Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian and Permian periods. Following these came the Mesozoic Era stretching for 160 million years. The Mesozoic comprise Jurassic, Triassic and Cretaceous period. Following these came the Cenozoic Era starting some 65 million years. This comprises the Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene and the Recent period starting only about a million years ago and is still going.
True, the earliest form of life is believed to have originated in the Pre-Cambrian era, life in our known form all started during the Cambrian period. By the Ordovician periods and most of the Silurian, many kinds of creatures thronged the shallow seas. These periods show a wide variety of plant and animal life, all of which show considerable advancement over creatures of the Pre-Cambrian and are far evolved from the first living things.
Life in its first form made its appearance in the sea. Possibly there were no living things on land then, and possibly none in the existing streams and lakes. In those days the land areas must have been unbelievably desolate wastelands of bare rock, sand, and mud, without any single form of life.
The oldest well preserved land plants come from the upper Silurian of Victoria, Australia. By Devonian time land plants had become common and are known from such scattered areas across the world. Still most were small and primitive. But by upper Devonian times there were forests of scale trees in some areas. These trees, which became extinct during the Paleozoic era, were the forerunners of those forming coal swamps of Pennsylvanian times.
The oldest undoubted fossil record of animal life on land from Devonian times when arthropods, including spider like and tick like animals were established. Several kinds of insects had appeared by the upper Devonian times.
Fishes were well established and flourishing by the Devonian times.
The Mesozoic times saw the real thrive of various reptiles, especially the dinosaurs. Even crocodiles also appeared during the Mesozoic era. Flying reptiles which form the earliest bird also appeared during this time in the Jurassic age. The close of Mesozoic saw decline of reptiles.
Cenozoic saw the plants and animals resembling those of today. Flowering plants and mammals dominated in this era. Of all mammals man belongs to the Primates and is the latest and most advanced addition in the biological pyramid.
While various forms of life have emerged, sustained and gone into extinction over the past, they are all the ancestors of any form of life doing fine here on Earth. These, including us, are what we see around.
The forms of life:
Let us now see what types of life forms we see around us. Are they only some creatures, intelligent or not, capable of moving around? Or, are they only capable of growing? Or, are they capable of growing and feeding themselves? Or, are they the forms in which all of these can be found?
Earlier it was the world of animals that was thought to be the only living forms on this planet.
And it is a matter of only the last few decades that forms, other than animals, came to be included in the world of living beings. And it was till recently that the bacteria, the fungus, and some forms of algae have come to be regarded as separate forms of life.
So based on this, today we know that there is a five-kingdom system representing the living beings around us. This is as opposed to the two kingdom system of plants and animals.
The animals, the bacteria, the fungus, the algae, and, the plants.
The Human Body
The Human Body
| The human body is the most well defined of all animals. We are the most intelligent as well! Like any vertebrates, the parent family to which the humans and other mammals belong, humans have an internal bone structure. This is called the skeleton. It includes a backbone of vertebrae. Above the skeleton lie layers of tissues, flesh, networks of nerves and blood vessels, fats. All these layers are topped by the layers of skins. And, like any other mammal, the sub family or the vertebrates, the human body shows certain common things such as hair, mammary glands, and highly developed sense organs. Despite these similarities, there lie many differences. The differences that has made human so unique. In no other animal you will find so much of perfection. The right thing at the right place and of right size. There lies two to three of the cages that hurries any activity. Take, for instance, the backbone, the rod like bone joint, is common to all vertebrates. But human backbone has a unique feature. Because it helps human to be blessed with a stable two-legged erect posture. Thus human can walk straight for hours only on two limbs. The vertebrates, have all got a spine-like bone joints. Even those who hop on two legs when moving rapidly, like the marsupial kangaroos, walk on four legs and uses their tails as a "third leg" to stand. So is the case with the primates like the half-erect chimps and guerrillas who use all fours more often than two limbs. Moreover, the human brain is by and large the most highly developed in the animal kingdom. As intelligent as are many other mammals--such as chimpanzees and dolphins--nonehave achieved the intellectual status of the human beings. Let us take down a look at ourselves. It is a uniquecombination of two(s). Our body has two sides. The frontside called the ventral side. And the dorsal or the back side. Height wise too, it has got two different ends. The anterior, or the head, end. And a posterior, or tail, end. So is the case with the most other body parts. Like two pairs of limbs, two halves of breast, each housing a similar looking cage-like bony structure, called ribs. At the top of the ribs sit two shoulders. Above this the tube like neck is crowned by the head. Even the head has got a set of two eyes, two ears, two sets of teeth, two nostrils. And they are distributed in such a manner that if the whole body is sliced cutting from the head to the tailbone, two similar looking halves will come out. This is why human body is called predominantly symmetrical. Let us start with the limbs. Like any other mammals humans have two pairs of limbs. But for none other, the upper and lower limbs have such distinctive jobs to do. The slimmer and lighter upper limbs are hands. Made of upper and lower arms, the knuckle and the fingers. The elbow hinges the upper arm to the lower one. The wrist hinges the lower arm to the padded palm, the knuckles and fingers. Obviously all are meant for doing all the handy jobs - mighty and also the finer ones. The heavier lower limbs are the legs. Each one is made of thigh, calf, and feet. The thigh is hinged at the hip joint. The sheen and the calf are hinged at the knee, while the feet and the hill are hinged at the ankle. All are meant for doing the leggy business. They do not only help you stand, and walk, and run, and sit, and lie down and jump like other animals. But they also help us hold our 'default' erect posture all the time. The legs are hinged at the pelvis with the upper body, or, the trunk, through the hip joint. Hip has a pair of bones connected at the tail bone inside. At the outside the hips are also divided into two halves. Each has got an extra pad of flesh at the hind to help you do things, like sitting, and lying down. Ii is the hip joint that supports and balances the trunk. The hips apart, the pelvis contains and supports the The excretory organs, like the urinary bladder and tubes, the ends of intestines. Each of them helps us get rid of the body wastes. The pelvis also contains internal reproductive organs. These organs are different for different sexes. Moving up higher, lies the abdomen. It is the largest cavity or hollow space in the human body. It has got no bone support except the rod like backbone that runs through the hind side. It houses many important organs. The digestive organs, including the pancreas, liver, intestines, spleen, gall bladder lie here. These organs produce juice like secretions which help the process of digestion. The abdomen also contains the base of the excretory organs, like the kidneys. Moving up still further, there lies the chest. It is the second largest cavity. Human chest is supported by a cage-like bone structure made of 12 pairs of ribs, the breastbone. And the backbone part at the hind side. Chest contains the chief organs of respiration and circulation. They include the lungs some air passages, the heart. The lung is placed within the right rib cage. And the four-chamber human heart is in the left cage. In between the two rib cages runs the food pipe, called the esophagus. Below, the chest is bounded by an elastic screen, called diaphragm. This screen separates the chest cavity from the abdominal one. The chest is connected at the shoulder to the head through the neck. At the front side is the throat, made up of the cone shaped pharynx. The pharynx connects the mouth and the nose endings at the head to the wind pipe and the food pipe. The food pipe is called the esophagus. And the larynx includes the mouth of the wind pipe and the voice box. The wind pipe, or the trachea, a 10 to 12 cm long tube, carries air down to the lungs. The food pipe, or esophagus, originating from the throat opening runs through this supple tube-like part, down to the chest and tummy. The pharynx chamber, thus, serves both the breathing and digestive functions. Top of all lies the head. It is like the cockpit of a plane that drives the functioning of the whole body. It houses the eyes, and ears, the nose and the mouth. And it has brain, protected inside the hard shelled skull. All these help us see, smell, hear, and taste. And most importantly, think. All major nerve endings that receive and send signals from outside and also from within the body lead to the brain. |
Our Home Planet
Planet Earth
 is just one of the nine planets in the family of Sun, called the solar system. If you start counting away from the Sun, the planet Earth comes third in distance. At one stage of its infancy,Planet Earth was in a very |
like all other planets it too has undergone many changes before reaching the present stage.
Today, if you approach the Earth from outer space it appears to wear a fade greenish blue color. This is absolutely uncommon. For, no other planet in the solar system wears this color - the color of life.
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BIRDS
When on ground, some prefer the grassy land, some high rocks. Some are just ga ga over the wild flowery woodlands. Some prefer preying in fresh water, some like to be busy by the seashore. Depending on the preference of hunting and hatching the birds thrive and throng the earth in myriad of size, shapes, color and sound.
The high flyersinclude the mountain birds who are equipped to stand cold, wind and fierce rays from the sun. The small ones rarely risk a flight. In summer, the sparrow-like accentors of Europe and Asia merely hop about in search of insects on the green patches and in the rocky crevices. High up in the Andes the Patagonian earth creeper is a bird no bigger than a flinch. It nests in a windproof snuggery which it builds by digging up a meter long tunnel to ward off the cold and gale. The Himalayan variety actually nests above 5000 meters (17000 ft). But as winter closes in, they move downhill to safer land.
Wall creepers reach even higher levels as they probe cliffs for insects, clinging on with toes and tail.
The partridge like rock ptarmigan turns white in winter to camouflage against the snow.
The bigger mountain birds
are strong enough to cope with violent winds. Some fly or soar among the very high peaks. Mountaineers have even seen choughs flying even near the summit of some highest mountain tops. These are a type of crow with yellow bills, find worms and insects among the rocks. Winds continuously shower the upper slopes with dead and dying insects whisked up from the lowlands. Million end up high on the snowfields which act as a natural freezer. So the mountain birds can have them in plenty.
However, the flying giants need bigger morsels. Mountain eagles with the sharpest eyesight swoop on small mammals and birds from a long distance below. Vultures scavenge food from any corpse, also with a gifted vision to spot food. Andean condors are the largest of all soaring vultures. Both groups can soar for hours on air rushing up the slopes. Their mighty wings are specially designed to do so. Both nest and lay eggs on cliff ledges, safe from other mountain predators.
Thousands of bird variety thrive in the cold icy polar regions of Arctic lands. But because of tremendous cold most migratory in nature and are summervisitors. Long daylight hours for feeding, and plenty of insects make the tundra a good place for lots of song birds such as wheatears, warbles and sand martins.
Among the predators there is snowy owls which depend heavily on mouse-like lemmings. But when lemmings go scarce many owls migrate or starve.
Forest birdsThe forest of the island continent Australia is inhabited by colorful birds. Like lyre-birds which skulk among thick underbrush, where males display their long tails shaped like the ancient musical instrument.
Yet another variety is kookaburra, belonging to the kingfisher family. It hunts insects and reptiles.
In the rain forests of Amazons is inhabited by scarlet macaw, of parrot family. Though they do not have the crest like the Cockatoos, but they display brighter variety of colors.
The toucans are of the fruit eating birds with huge, pointed, brightly colored beaks.
The tiny multicolored hummingbird that sips nectar from the flowers can hover mid-air with the beaks planted inside the flower. It does so by flapping its wings at a tremendous speed. The predator bird in the Amazon include the harpy eagle which rests and nests on the treetops with a keen eye for the prey, mostly monkeys.
But most variety in color and species is seen among the tropical birds. Plenty of thick trees and the creepers provide homes for birds along with snakes and monkeys.
The broadleaved branches and treetops make the perfect nesting sites for a wealth of gaily colored birds.
The brilliantly colored male birds like Wilson's bird of paradise, regent bowerbird and Count Raggi's bird of paradise deck the hot and humid forests of New Guinea and north eastAustralia. The males have a plumage and display to help the females of their species to identify them among the branches.
In the tropical forests of Africa and South East Asia there are fruit eating birds feeding among the canopy. This include hornbills, parrots. And there is also tiny gaily colored sunbird of the hummingbird family.
The broadleaved woodlands of the North is the habitat for a lesser variety of birds than the tropical forests. The small ones include the song birds like thrush, nightingale and the common variety like woodpecker. Blue jays live in the woodlands of the eastern United States and Canada. They eat nuts, acorns and small seeds. In spring they steal eggs and chicks from the nests of other woodland birds. Hummingbirds also inhabits North America.
Farther up the coniferous forests in the north offers short summer and long cold winter. While most are migratory visitors from the colder tundra and Arctic land, the typical inhabitant of these forests include the tits, warblers, and the plant eating crossbills; along with the woodpeckers. Tilts and warblers hunt insects high up among the twigs ad leaves. As autumn draws warblers fly south. Swallows nest in Europe in the summer. To escape the winter cold they fly deep south to Africa. Other migratory birds include bobolink, a songbird. It breeds as far north as the Canadian forests. But it winters as far south as Argentina.
Again some from the polar region make these lesser cold forest their winter home. The hunter birds include the goshawk and the owl. Both are famous for the agility.
Grasslands
The grasslands of the prairies in North America is the habitat of quite a lesser variety of birds. While the prairie chicken belongs to the fowl family and the larger preying variety include the prairie falcon and the burrowing owl.
Meanwhile, the grasslands of African savannah houses no more a greater variety. The flightless ostrich, the largest bird on earth, hails from here. Each of its two antelope-like feet rests on long toes that help to lengthen the leg and give a long, swift stride.
The grasslands of steppe is replete with birds of prey like the huge taloned steppe harrier and the very large tawny eagles.
The low Australian grassland is also home to a sizeable variety of birds. And many of them are not found elsewhere in the world. Perching on the grassland trees there are flocks of budgerigars. The big-tailed crested cockatoosof parrot family also perch on the gum trees. Here, wedge-tailed eagles swoop on birds, rabbits the small marsupials. These beat all the eagles in the wing-span which extends 2 meters(6 1/2 ft).
Desert
Deserts offer a more hostile surroundings for the birds and animals to live in. Most desert birds must drink often to replace the water they lose. This forces them to live near the waterholes or rivers. But pools of water in deserts often tend to be salty. Ostriches are among the few birds that can drink salty water without coming to harm.
Most of the desert birds eat insects. Others are carnivorous - mostly reptiles. Still a handful eat seeds. Vultures and condors soar up into the cool air high above the hot sands or rocks. The Californian roadrunner kills and eats snakes. The Sonora white rumpled shrike builds a larder of lizards skewered on thorns. Small birds hide from the heat of the day in the shade. Small birds of this region include fowls, geese, ducks and grouses. The Gila woodpecker lives in the hollow of large cactus plants in the North America. The sand grouse may soak their breasts, then fly many kilometers to chicks that suck water from their feathers.
Peacocks are seen in the semi desert region of India. The male birds sport a crest and a long feathery tail of multiple shades of silvery blue, green and golden and yellow.They raise their tail like a fan to attract the female bird, peahen. Equipped with sharp bills they eat insects and small snakes. Their number has reduced much these days.
Water birdsWater birds comprise majority of the migratory birds. Crustaceans in the many ponds make it suitable for these birds, particularly ducks, eiders, geese, terns and waders. These migratory birds are famous for taking long distance flight. These include the red throated pipit and water birds like red breasted goose and snow goose. But the champion long distance traveler is the Arctic tern which migrates half way around the world.
Compared to the Arctic birds in Antarctica lacks variety. Though migratory water birds do visit the cold summer seas belting the continent, they do not make it farther up to the frozen land where food is a real scarcity.
Best known of all the Antarctic birds are penguins. Though most of the variety live on the icy coasts of the Antarctic, some venture farther upward on the desolate islands of the Indian oceans. Apart from the flightless penguins, the sheathbill are the rather ugly southern relatives of gulls. These live by snapping up the dead penguin chicks and morsels dropped by penguin parents. The skua is the snatching variety, which live on by seizing untended eggs and chicks of penguins.
Among the others, the fragile looking snow petrel nests up to 320 km inland farther south than any other bird.
The flightless birds
The flightless variety in the South include the penguins. These flightless birds have wings which they use as flippers. They are more comfortable in water and swim superbly after fish and squids. On land they waddle awkwardly. They lay eggs on land. The smaller Adelie penguins trudge and slide across large distance to reach the breeding rookeries. Hardiest of all is the emperor penguin. It breeds on ice sheets. Males incubate the eggs between their feet and belly skin flaps. They also protect the eggs from the predators. The females fish for squids to feed the hatchlings.
Moving northward from the Antarctica lies the Australia and New Zealand. New Zealand houses most significant of all flightless variety. While giant moa, larger than ostrich have been wiped off by man long ago. Only the small variety like kiwi and takahe sustains. The small kiwis, laying larger-than-self eggs, have been made New Zealand's national bird. The takahe is a hen-sized bird with green blue eyes. It spends summer in marshy mountain valleys and during winters it hops lower down.
The vast Australian lowland houses a wealth of colorful birds. The large variety includes the Emus. The largest of all in this lowland. Strutting in the lowlands of Australia, they are, in fact, second only to the Ostrich, the African variety .
Fresh water variety:
These apart, all over the world fresh water birds show the greatest variety and countless in number. Almost all undisturbed lakes, ponds, pools and wetlands are busy with the noise and activities of water birds. Ranging from the familiar family of ducks and ducklings, and those conceited long necked swans and ganders, there are flamingos, pelican, cranes, herons, coots, great crested grebe, drakes, bitten, lily trotters and many more. Leave aside the gaily colored kingfisher and other birds that rests up above the ground on the branch, their diving or swooping platform.
Some keeps wading, some waits meditatively, some prefers to stand erect on just one leg like a watch tower, while some drops in water suddenly from nowhere. Some are hard swimmers, some just float idly. Some are too restless - taking dips, flapping on the wings, pacing up the swimming speed and then pacing down.
The darters of Asia, Africa and the Americas swim well underwater. These snaky necked birds can stab a fish with their long, spear-like bills.
Cormorants also dive for fishes. Brown pelicans plunge for prey but white pelicans often swim in flocks to trap fishes by driving them into the shallows.
Shovellers are ducks that sieve small creatures from the mud. Flamingos and spoonbills feed in a similar way. But the long legged herons are wading birds that hunt for fishes.
The dainty lily-trotters go in for insects and snails that live among the lilies.
But the water birds not only throng the freshwater area. Those preferring the salty seashores are also quite a few.
The common variety includes various seagulls, oystercatchers, the long billed curlews, the terns, gannets, kittiwakes, guillemots and puffins. Sea gulls may be different like the black headed gull, the all white gull, the grayish gulls. And the albatross is the largest of all the gulls.
Of all these shore birds some prefer sandy shores some the sea washed rocks. Obviously it is due to their food habits.
Well, all these represent just a cross section based on the broad classification of the habitats of birds the world over. There are also various commonly seen birds which live and play around us. Who hasn't been harassed by the little mischievous magpie? Or irritated by the quarreling sparrows, the harsh cawing of the crows? Partridges though not a frequenter around our locality, they are not rare. There are a few who have not seen kites and gulls circling high up in the sky. Again there are plenty chirping and twittering from the nearby trees, the backyard bushes and from among the wayside underbrush. Mostly beyond our busy eyes. A caring look will reveal them and be a source of real pleasure. While quite a few have been included, many more are possibly left. May be, they will be seen here in future.
Three Tips to Keep Your Desktop Computer Cool
Three Tips to Keep Your Desktop Computer Cool
Are you concerned over the amount of heat your desktop computer is generating? Heat is a common by-product of a running computer. Your desktop is designed to operate at certain levels both below and above normal room temperature. If your desktop computer gets too hot, however, you are in for disaster. There are three things that you can do to curtail dangerously high computer temperatures.
* Thermal Compound
Use a thermal compound to fully join the central processing unit (CPU) to the heat sink. Although the CPU is connected to the heat sink, there are air holes in between the irregular surfaces of the two components. Thermal compounds or thermal pastes conduct heat faster than air. Filling in the gaps with a thermal compound will aid the heat sink in drawing heat away from the CPU.
* Additional Fans
Better airflow can accelerate the rate at which internal computer components cool. To enhance airflow, install additional fans inside your computer case. You can strategically place the fans such that cool outside air is sucked inside one side of the computer case, while hot internal air is expelled through a different side.
* Water Cooling
For serious overheating issues, you may want to consider water cooling. This involves running water through cables looped inside your computer case. Liquids are better at absorbing heat than air; thus, a water cooling system can control computer temperatures more effectively than internal fans.
Some people are hesitant to try out water cooling due to the risk of water leaks. Should a leak occur, your computer will be short-circuited in moments. Water cooling is also very costly.
In most cases, proper ventilation is enough to keep a computer cool and away from overheating problems. Should you want a really cool PC though, you will have to look into water cooling and the risks and costs associated with this relatively novel cooling system.
Saturday 21 May 2011
Things to make - LED reading light
Things to make - LED reading light
Led reading light
This project makes a flashlight that puts out just enough light to read by. It might be useful on camping trips, for reading road maps while riding in a car at night or for someone outdoors at night pursuing amateur astronomy. Its advantage over a manufactured flashlight is that this design gets more than 50 hours operation from a set of batteries. It uses a led which lasts practically forever instead of an incandescent bulb which typically last about 20 hours.
It may be that this project is of interest only to those who already have some of the required tools and materials. Otherwise the project might be too expensive. In particular, some people may already have a soldering iron, solder, black electrical tape and a small amount of hook up wire. Also needed from a discarded ink pen, is a large ink pen cap with a metal clip. You will need to purchase an extra bright led. This is Radio Shack part number 276-205. It outputs 6000 mcd of light and draws 20 ma of current from the batteries. The price is about $2.00. Two 1.5 volt AA alkaline cells are a good choice for batteries. Standard(non alkaline) batteries will last maybe one third as long. C or D cells will increase the hours of operation 3 and 6 times respectively but you may find their larger sizes objectionable. A 56 ohm resistor is needed. Either 1/4 or 1/2 watt will do. The color code for this resistor in case you need to pick one out from used parts, is green, blue and black. The ink pen cap with metal clip will function as an on/off switch. The resistor is to limit current so the led will not be destroyed. The Radio Shack led package will tell you that about 1.9 volts and 20 ma is needed for the led. Ohms Law(voltage=current times resistance) can be used to calculate the resistor's value. Just rearrange the Ohms Law terms to get resistance=voltage/current or ohms=volts/amps. 20 ma is .020 amps. For the voltage use 1.1 volts since you start with a total of 3 volts(2 X 1.5) from the batteries and 1.9 is used by the led. That leaves 1.1 left to be across the resistor. So the equation becomes ohms=1.1/.02. The math comes out to about 50 ohms but the closests common resistor value is 56.
Tape the two batteries together side to side with a positive end next to a negative end. Place the cap along side the batteries and tape it securely in place running the tape under the metal clip and going around at least several times. Solder the lead coming from the resistor to the positive battery end that is near the closed end of the cap. The wire coming from the switch can now be soldered to the negative battery terminal that is near the closed end of the pen cap.The wire from the other led lead goes to the metal clip. Cut it to length allowing about 3/4 inch for wrapping around the base of the clip. Remove the insulation from that 3/4 inch portion before wrapping. Put a piece of paper or thin cardboard between the switch contacts. Connect the other two battery terminals to each other with a short piece of wire soldered to the two terminals.
The finished led reading light photo should eventually appear at the bottom of this page.
Led reading light
This project makes a flashlight that puts out just enough light to read by. It might be useful on camping trips, for reading road maps while riding in a car at night or for someone outdoors at night pursuing amateur astronomy. Its advantage over a manufactured flashlight is that this design gets more than 50 hours operation from a set of batteries. It uses a led which lasts practically forever instead of an incandescent bulb which typically last about 20 hours.
It may be that this project is of interest only to those who already have some of the required tools and materials. Otherwise the project might be too expensive. In particular, some people may already have a soldering iron, solder, black electrical tape and a small amount of hook up wire. Also needed from a discarded ink pen, is a large ink pen cap with a metal clip. You will need to purchase an extra bright led. This is Radio Shack part number 276-205. It outputs 6000 mcd of light and draws 20 ma of current from the batteries. The price is about $2.00. Two 1.5 volt AA alkaline cells are a good choice for batteries. Standard(non alkaline) batteries will last maybe one third as long. C or D cells will increase the hours of operation 3 and 6 times respectively but you may find their larger sizes objectionable. A 56 ohm resistor is needed. Either 1/4 or 1/2 watt will do. The color code for this resistor in case you need to pick one out from used parts, is green, blue and black. The ink pen cap with metal clip will function as an on/off switch. The resistor is to limit current so the led will not be destroyed. The Radio Shack led package will tell you that about 1.9 volts and 20 ma is needed for the led. Ohms Law(voltage=current times resistance) can be used to calculate the resistor's value. Just rearrange the Ohms Law terms to get resistance=voltage/current or ohms=volts/amps. 20 ma is .020 amps. For the voltage use 1.1 volts since you start with a total of 3 volts(2 X 1.5) from the batteries and 1.9 is used by the led. That leaves 1.1 left to be across the resistor. So the equation becomes ohms=1.1/.02. The math comes out to about 50 ohms but the closests common resistor value is 56.
| Use a safety pin to poke two holes in the pen cap on either side of the clip. The holes should be exactly to the side of where the clip end contacts the cap. This is at the free end of the clip. Then strip the insulation off of a piece of hook up wire and weave it through the holes as in the lower diagram. Bring the wire all the way around the cap and twist it together. The wire should be tightly wrapped around the cap. At least one end of this wire needs to be long enough to reach a battery end. See the photo at the bottom of this page for where the batteries will be. The clip and wire make a closed switch that will keep the light turned on without having to hold the switch closed. Then to turn off the switch, slip a piece of thin card board or some other material between the clip end and the wire. |
| Make a hole on each side of the cap near the closed end of the cap. This can be done by heating a nail on a stove, holding the nail with pliers and letting the hot nail melt a hole. The holes should be slightly larger than the hook up wire that you soldered to the led and resistor. |  |
| Select two pieces of insulation covered copper hook up wire, each a couple of inches longer than the pen cap. Put an end of each lead into the open end of the cap manuevring the ends through the melted holes. |  |
| Solder the resistor to the long positive lead of the led. Solder the leads coming from the open end of the cap to the free end of the resistor and the free led lead. Make sure you remember which lead goes to the resistor. That lead must go to a positive battery terminal. Put tape on any bare wire of the led/resistor/lead wire assembly that might touch and short circuit. |  |
| Carefully pull the leads farther through the melted holes until the led is up againt the open end of the pen cap.After that, wrap black electrical tape tighly around the end of the cap so about 1/4 inch of the tape's width is on the led. Go around 6 or so times keeping the tape stretched as you go so that it holds the led securely. |  |
Tape the two batteries together side to side with a positive end next to a negative end. Place the cap along side the batteries and tape it securely in place running the tape under the metal clip and going around at least several times. Solder the lead coming from the resistor to the positive battery end that is near the closed end of the cap. The wire coming from the switch can now be soldered to the negative battery terminal that is near the closed end of the pen cap.The wire from the other led lead goes to the metal clip. Cut it to length allowing about 3/4 inch for wrapping around the base of the clip. Remove the insulation from that 3/4 inch portion before wrapping. Put a piece of paper or thin cardboard between the switch contacts. Connect the other two battery terminals to each other with a short piece of wire soldered to the two terminals.
| If the light will only be used inside a vehicle, the batteries can be elimnated. Two leads coming out of the pen cap could go to a plug connector made to get power from the vehicles cigarette lighter. Or run the wire from the positive led lead to a terminal on the vehicle's fuse box. The other negative lead would be attached to metal that is connected to the vehilce's body. The resistor value must be changed to use the higher voltage from the vehicle. Roughly 2 volts will be across the led which leaves about 10 volts across the resistor. Ohms Laws gives resistance=voltage\current=10\.020=500 ohms. The common closest value is 470. Don't worry about running the vehicle's battery down. It would take at least a few days of constant operation to do that. |
The finished led reading light photo should eventually appear at the bottom of this page.
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