Why do we cough and sneeze when we have a cold?

When we have a cold, the disease-causing germs reach the respiratory tract, and mucus builds in the bronchia. These are the branches of the air pipe that go inside the lungs. The body tries to get rid of this mucus by coughing vigorously and throwing the disease-causing germs out of the lungs along with air. The same thing happens when we sneeze. The nasal mucus is stimulated and the nose starts to tingle. We have to sneeze and in this case too, the germs are thrown outside forcefully.

Why do we fall ill?

Some diseases are caused by bacteria, and some, such as AIDS and the common cold, are caused by viruses. Normally, our immune system protects us against diseases. But sometimes our body-because of too little sleep or a lot of stress-becomes so weak that the immune system does not work properly and we succumb to diseases. Luckily, we can get ourselves vaccinated against some dangerous diseases.

Is playing sports healthy?

Playing a sport is healthy because it trains the muscles, improves blood circulation, and increases the supply of oxygen to the body cells. Improved oxygen supply to the brain improves concentration, and physical movement excites the nerves paths in the brain. We, therefore, become mentally more efficient. Sometimes professionally played sports may causes excessive strain on the body, but leisure sports that are fun can strengthen our immune system and are necessary for our will being.

How can we protect ourselves against bacteria?

We do not need to protect ourselves against all bacteria. Some live inside out body and are even very important to us, such as the intestinal bacteria. We fall sick only if there are too many bacteria or some harmful bacteria unknown to the body comes form outside. This can happen easily via cuts and bruises on the skin or when our bodies are weak. Antibiotics help against bacterial infections. Unfortunately, they are not always effective because many bacteria have already become 'resistant' to them. The best way to stay healthy is to strengthen our own immune system. A diet rich in vitamin, i.e., fruits and vegetables and exercise in fresh air helps in keeping us fit.

Why must we brush our teeth every day?

When we eat, small particles of food get stuck between the teeth, giving rise to bacteria. They reproduce and create dental problems like caries. At first, these are only holes in the enamel of the teeth, but as they become deeper they can be very painful. Chewing becomes difficult with bad teeth, and the jaw looks deformed if some teeth are missing. If the bacteria are not removed, they can enter your body through the mouth. The writings of a Greek doctor Hippocrates are a proof that the connection between hygiene and disease was known 3000 years ago. So, even the ancient Greeks brushed their teeth!

What happens when we eat too much?

If we eat more than what we really need, or body converts the excess food into fat and we become bulky and heavy. The skeleton and the joints are not designed to carry too much continuous load; hence, at some point of time the back and the joints begin to ache. Any kind of fast movement becomes tiring and strenuous for the heart and the circulatory system. We get out of breath very easily. Fat people are often the butt of people's jokes. Although is is difficult for them, they can get in shape again though training and healthy eating.

Why are vitamins necessary in diet?

Vitamins assist the body in utilizing the nutrients. They are not suppliers of energy like fats or carbohydrates, but help the body in absorbing minerals such as calcium, magnesium, or sodium contained in salt and transporting them to the required places. Vitamins also help in the correct functioning of enzymes that help convert food into components useful for the body. Since the body cannot synthesize vitamins, they need to be supplied form outside.

What keeps us healthy?

A lot of things can keep us healthy: a right amount of sleep, exercise fresh air, having friends, and healthy food. Eating healthy food means not eating too much and not eating the same thing always. Our food is composed of three components: fats, carbohydrates, and proteins. Carbohydrates like sugar and starch, are present in potatoes. We also need vitamins and minerals, such as salt or calcium to stay healthy. We need to brush our teeth often and keep ourselves clean to keep away he bacteria and remain healthy.

What is the different between sex and love?

Sex is a purely physical act, while love is also about emotions. There is trust, acceptance, security, and much more, in love. Love is a feeling that can change, and  is tested at times, such as between the parents and the children during puberty and between friends. Love may include sex, but there are lifelong friendships that have nothing to do with sexuality. Sex between two people can take place without any feeling of love.

At what age does one becomes an adult?

In most countries, a person is legally treated as an adult after his/her 18th birthday and is, considered responsible by the law for all his actions. For example, in most countries, a person is considered responsible enough to vote at the age of 18. Some cultures consider reaching physical maturity as the sign of growing-up and girls are often married at this time. In some religions, there are some ceremonies open only to boys and girls over a certain age. For instance, in Judaism, a person is allowed to read the Torah, their sacred writings, for the first time only after he/she attains a certain age.

What are the other changes during puberty?

Puberty is often a time of rebellion, in which familiar things, such as rules in the family, are questioned. Due to hormonal changes in the body, young people undergo emotional instability. Friends and people of the same age become very important. They are torn between being the glamour of being independent and the risk of leaving a secure life. Unfortunately, at this time peer pressure poses a grave danger of getting into conflicts and addictions-such as alcohol or drugs.

Do only boys undergo a voice change?

Girls also undergo a voice change, but it is not as pronounced as in boys. The larynx in the throat is responsible for the voice and the vocal cords are present inside it. In children, the vocal chords are short, so that the voice is rather shrill. During puberty, the larynx grows rapidly in boys and one can clearly see it, the 'Adam's apple', in the centre of the throat. The vocal cords enlarge and become thicker, and the voice becomes deeper. the muscles of the vocal cords take time to adjust tot he changes. Till then, the voice 'jumps' between high and low tones and is either shrill or deep.

How does the body change?

The production of sex hormones results in the growth of breasts in girls, a broadening of the hips, and the start of menstruation. In case of boys, the body becomes more muscular, testes and penis increase in size, the production of semen starts, and the night ejaculations begin. This is the time for first loves and understanding sexual orientation. A lot of activity goes on in the brain too. New nerve paths arise, and old ones disappear.

Why are some babies disabled at birth?

The causes of disabilities are many and cannot always be explained. We do know that a lack of oxygen at birth can cause damages to the brain. If the mother smokes or takes drugs during pregnancy, it can have serious consequences because the drug reaches the blood circulation of the child via the umbilical cord. Sometimes, there may be genetic changes which may cause disabilities. For instance, a changes which may cause disabilities. For instance, a change in the 21st chromosome, causes Down syndrome in the child. It is important to ensure that people with disabilities are not discriminated against in our society.

How does the baby breathe in the uterus?

A baby does not need to breathe in the uterus. Everything that it needs for its growth is provided to it by its supply line: the umbilical cord. This cord connects that blood circulation of the child with that of the mother. The foetus, as the unborn child is called, gets nutrients and oxygen though the umbilical cord. The waste products of the foetus are thrown out into the blood circulation of the mother and are excreted by the mother. After the birth of the baby, the umbilical cord is no longer required and is cut off.

What happens at puberty?

Puberty starts at about 11 or 12 years of age for girls and around 13 years for boys. This is a phase of development, in which the body and the mind undergo a change. Growth spurts, the production of sex hormones start, girls experience their first menstruation, and boys experience the breaking of there voices. Boys and girls start discovering their own sexuality and emotions run high. The transition from childhood to the adult phase is a special time and has different meanings in different cultures.

e-commerce

   Since the introduction of credit cards and the beginning of banking automation in the 1960s, computers and com-munications networks have played an increasing role in the infrastructure of commerce (see banking and computers). Some businesses also established proprietary networks (for example, to allow pharmacies to order drugs directly from suppliers).

Electronic sales directly to consumers were pioneered by “teletex,” such as the French Minitel, as well as such ser-vices as CompuServe and America Online. However, these services were proprietary, meaning that businesses could only market to subscribers. The widespread adoption of the Internet in the mid-1990s (see World Wide Web) created an open and potentially much larger marketplace.

   The first e-commerce boom came in the late 1990s, when enthusiasm about the seeming potential for unlim-ited profits drove numerous online startups, often with poorly conceived business plans that assumed that rapid expansion and low prices would result in gaining con-trol of a particular sector and achieving a dominant (and profitable) position. Among the numerous casualties of the “dot-bust” of 2000–2001 was WebVan, a company that sold and delivered groceries directly to consumer’s homes.

While the bursting of the “dot-com bubble” was pain-ful to investors, entrepreneurs, and workers, recovery was soon underway. The recovery was aided by the steady growth of Internet users (particularly those with broad-band connections), innovative software for interacting with consumers and analyzing transaction information, and the coming of age of a generation that had virtually grown up online.

   Today e-commerce is a steadily growing sector, and it is increasingly international, fed by nearly 1.5 billion Internet users worldwide. (China, with more than 250 million Web users, has become the world’s largest online market.)

Meanwhile in the United States in 2007 total consumer retail sales on the Internet reached $136 billion, up nearly 20 percent over the previous year. According to a report from Forrester Research, online retail revenues (excluding travel-related services) will pass $250 billion by 2011. Sur-veys show that about 80 percent of American Internet users have bought something online, while many users who buy products off-line originally searched for information about them online.

The most popular e-commerce sectors today include the selling of books, music and movies, travel-related services, electronics, clothing, luxury goods, and medications. (In 2006, online buyers actually spent more money on cloth-ing than on computers and related products.) A number of other online activities can be considered part of e-com-merce, although they are usually not included in retail-ing statistics (see auctions, online; online gambling; online games; and social networking).

Infrastructure

   Successful e-commerce depends on a complex array of ser-vices, facilities, and software. For marketing and consumer communications, see online advertising and customer relationship management. Behind the scenes, trans-action data is constantly being collected and analyzed to determine the success of the marketing program and to “personalize” the customer experience and allow for tar-geted marketing (see cookies and data mining).

   The actual transaction processing requires shopping cart software and a connection to the credit card processing infrastructure (see digital cash). Specialized forms of sell-ing require additional software and support systems (see, for example, auctions, online). An ongoing e-business must also deal with functions shared by “brick and mortar” (traditional) stores: inventory control, ordering from sup-pliers (see supply chain management), taxes, payroll, and so on. The broader e-commerce sector also includes busi-nesses that do not target consumers but, rather, the needs of business itself—so-called business to business or B2B.

Security and Privacy

   One continuing obstacle to the growth of e-commerce has been consumers’ concerns about the theft or misuse of per-sonal information gathered as part of the shopping process. This can involve either fake Web sites (see phishing and spoofing) or legitimate businesses that sell information about customers without their knowledge or consent (see privacy in the digital age). According to a report from Gartner Research, more than $900 million in e-commerce sales during 2006 was lost because of consumers’ security concerns, and about a billion dollars more in sales was lost because customers decided not to buy online at all.

Trends

   E-commerce is maturing even as it continues to evolve. Some trends in the second half of the 2000 decade reflect changes in what is presented to the consumer, how it is delivered, and how users can participate in ways other than simply viewing content and selecting products:

•  delivery of richer and more interactive multimedia experience, catering to the widespread availability of broadband connections

•  integration of marketing using programming inter-faces (see mashups) with popular online services such as Google Maps, online game worlds, and social networking sites (see online games and social net-working)

•  increasing participation of consumers in develop-ing the quality of the shopping experience, such as through user product reviews and blogs (see user-created content)

•  increased emphasis on serving rapidly growing for-eign markets, such as India and China

•  the spread of e-commerce to new mobile platforms (see pda and smartphone)

Eckert, J. Presper

Eckert, J. Presper

(1919–1995) American

Computer Engineer

   J. Presper Eckert played a key role in the design of what is often considered to be the first general-purpose electronic digital computer, then went on to pioneer the commer-cial computer industry. An only child, Eckert grew up in a prosperous Philadelphia family that traveled widely and had many connections with Hollywood celebrities such as Douglas Fairbanks and Charlie Chaplin. He was a star stu-dent in his private high school and also did well at the Uni-versity of Pennsylvania, where he graduated in 1941 with a degree in electrical engineering and a strong mathematics background.

   Continuing at the university as a graduate student and researcher, Eckert met an older researcher, John Mauchly. They found they shared a deep interest in the possibili-ties of electronic computing, a technology that was being spurred by the needs of war research. After earning his master’s degree in electrical engineering, in 1942 Eckert joined Mauchly in submitting a proposal to the Ballistic Research Laboratory of the Army Ordnance Department for a computer that could be used to calculate urgently needed firing tables for guns, bombs, and missiles. The Army granted the contract, and they organized a team that grew to 50 people. Begun in April 1943, their ENIAC (Electronic Numerical Integrator and Computer) was finished in 1946. While it was too late to aid the war effort, the room-size machine filled with 18,000 vacuum tubes demonstrated the practicability of electronic computing. Its computation rate of 5,000 additions per second far exceeded other calculators of the time.

   With some input from mathematician John von Neu-mann, Eckert and Mauchly began to develop a new machine, EDVAC, for the University of Pennsylvania (see von Neumann, John). While this effort was still under way, they formed their own business, the Eckert-Mauchly Computer Corporation and began to develop the BINAC (BINary Automatic Computer), which was intended to be a (relatively) compact and lower-cost version of ENIAC. This machine demonstrated a key principle of modern com-puters—the storage of program instructions along with data. The ability to store, manipulate, and edit instructions vastly increased the flexibility and ease of use of computing machines (see history of computing).

   By the late 1940s, Eckert and Mauchly began to develop Univac I, the first commercial implementation of the new computing technology. When financial difficulties threat-ened to sink their company in 1950, it was acquired by Remington Rand. Working as a division within that com-pany, the Eckert-Mauchly team completed Univac I in time for the computer to make a remarkably accurate forecast of the 1952 presidential election results.

   Eckert continued with the Sperry-Rand Corporation (later called Univac and then Unisys Corporation) and became a vice president and senior technical adviser. He retired in 1989. He received an honorary doctorate from the University of Pennsylvania in 1964. In 1969, he was awarded the National Medal of Science, the nation’s highest award for achievement in science and engineering.

e-books and digital libraries

   An e-book is a book whose text is stored in digital form and can be read on a PC or a handheld reading device. Since most books today are created on word processors and typesetting systems, it is easy for a publisher to create an electronic version. Older books that exist only in printed form can be scanned and converted to text .

   An e-book has a number of advantages over its printed counterpart. The text can be searched and can include links to sections or even to documents on the World Wide Web. Reading software or devices can easily enlarge text for the visually handicapped, or read it in a synthesized voice. Since only bits need to be moved around, e-books save trees as well as the cost of manufacturing, transporting, ware-housing, and displaying conventional books.

   There are some disadvantages. Many people are not comfortable reading large amounts of text at a computer. Portable reading devices that may be more convenient are relatively expensive and not standardized. There is no uni-versal format for e-books, so some software or readers may not be able to read all e-books.

   As of 2008 the e-book landscape may be in the process of being reshaped. Amazon’s Kindle book reader is the lat-est attempt to marry e-books to handheld devices. Weigh-ing less than a paperback book, the Kindle can download books and other content directly over a cellular broadband connection and display text using an “electronic ink” tech-nology that simulates print. Amazon is offering a large selection of e-books including electronic versions of current best sellers at prices several dollars below that of the hard-back version.

   Authors and publishers, like other content creators, may have to deal with the illicit copying and distribution of text in digital form, as happened with the last Harry Potter book even before its publication in 2007. Some e-books contain a form of copy protection (see digital rights management). This, as with video and music, can lead to compatibility problems.

   A number of e-publishers as well as conventional pub-lishers now offer books online, most commonly as pdf (portable document format) files. A hybrid service, “publish on demand,” keeps the book on file and prints and ships bound copies as they are ordered, eliminating the problem of remainders. In the future, so-called digital paper (a thin membrane that can display text), may be used to create a more book like reading experience.

Digital Libraries

A digital library is to e-books what a conventional library is to printed books. Sometimes called an electronic library or virtual library, digital libraries can be created in a variety of ways. Printed books can now be scanned and digitized rapidly. Google has said that it can scan 3,000 volumes a day using a proprietary system. (This is not necessary, of course, for books that were originally cre-ated in digital form.)

Advantages of digital libraries include the following:

•  There is never a shortage of copies or the need for a reader to wait for access.

•  many digital libraries allow full searching of the text of all volumes. Libraries can also use a common data format (such as “Open Archives.”) to make their mate-rial searchable throughout the Internet.

•  many older, hard-to-find books can be made more “discoverable” and accessible.

   Project Gutenberg is one of the oldest and best-known digital library projects, dating back to 1971. Most of the collection consists of scanned or transcribed texts of public domain (no longer subject to copyright) books. As of late 2007, Project Gutenberg had more than 17,000 different titles in its collection.

   Of course more recent books are covered by copyright. In order to include copyrighted books in a digital library, some sort of compensation to the copyright holder gener-ally needs to be made, and it is unclear how that might be implemented in a way that preserves free access.

   There are also what might be called “digital pseudo-libraries” such as Google Book Search. Google has been scanning part or all of the collections of universities such as Stanford, Harvard, and Oxford as well as the New York Pub-lic Library. Google provides full access to public domain books (or those for which permission has been obtained from the publisher). For copyrighted books there is a lim-ited ability to search by keyword and view a limited num-ber of pages. Amazon.com’s “Search inside the Book” works rather similarly, but only with books for which the pub-lisher has granted permission.

   Google’s initiative has aroused some controversy because, according to traditional practice, someone wanting access to a copyrighted work beyond “fair use” is supposed to obtain permission. Google has reversed this presumption, allowing publishers who do not want their material to be available to opt out. The Authors Guild of America and the Association of American Publishers have separately sued Google for copy-right infringement. Google argues that the limited amount of text provided for copyrighted books falls within the fair use provisions of copyright law. The authors and publish-ers, however, point to the fact that Google is copying the whole text of the book in order to allow for searching.

   If the legal issues can be settled in such a way as to allow robust digital libraries, the benefits for researchers will be considerable. Google already offers a “my library” feature that users can use to search for books they already know and organize and search them digitally.

What determines whether a baby is a boy or a girl?

The sex of the baby is determined by the chromosomes. They determine how our body looks like and how it works. They are also the reason we resemble our parents. The 23rd pair of chromosomes is different in case of males and females. In a woman, these are two X chromosomes, in a man it is one X and one Y chromosome. The egg cell has an X chromosome, the sperm could have either a X or a Y chromosome. If the sperm with a 'Y' chromosome fertilizes the egg, then the chromosome combination for the baby would be XY: a boy. If an 'X sperm' fertilizes the egg, the result is XX:a girl. It is clear, therefore, that the sex of the body is determined by the father.

What happens to the fertilized egg cell?

A new life can start with the fusion of the sperm and the egg, which contains the genetic information of the father and the mother in equal parts. On the way through the fallopian tube, the egg cell divides several times. It finally gets lodged in the mucous membrane of the uterus, a special hollow muscle. This has a good blood supply and provides the egg cell with nutrients. After it is fixed in the uterus, the egg cell is called an embryo and development starts immediately.

How does fertilization occur?

After a man and a woman have had sex, about 300 million sperm cells are present in the woman's vagina. The sperms swim forward with the help of their tails with a common aim: to fertilize the egg cell. The egg cell ripens in the ovary of a woman only once a month. Certain hormones then trigger 'ovulation', in which the egg cell is released from the ovary in the fallopian tube. Fertilization occurs if the egg cell meets a sperm. Doctors assume that after ovulation, an egg cell can be fertilized for a maximum of 12-24 hours. A single sperm cell is enough to fertilize the egg cell.

How are babies born?

When a man and a woman have sex, the erect penis of the male is inserted into the vagina of the female. The sperm cells of the male are ejaculated into the vagina of the female. If an egg cell has been released in the ovary at that time, it may get fertilized by the sperm and the woman may become pregnant. The baby develops in the woman's uterus for about 40 weeks, till it is developed enough to be born. Usually, babies are born healthy, but sometimes they may be with a disability.

Why must we sleep?

We may not know exactly why we need to sleep, but we do know that our body needs sleep to rest and recover. If the sleep is inadequate, performance of the brain and the body goes down. One becomes irritable and cannot concentrate. After several days of inadequate sleep, one may start hallucinating. The duration of sleep needed depends on the person and the age. While most babies sleep for more than 12 hours a day, some old people need 5-6 hours of sleep.

What is a stroke?

A stroke is a serious medical condition occurring as a result of an interruption in the supply of oxygen to the brain. The most frequent reason for a stroke is the blockage or bursting of a blood vessel in the brain. In both cases, the blood circulation and, hence, the supply of oxygen to the brain is interrupted. The result is damaged brain tissue. Stroke patients may lose all information that was stored in the damaged area and may have to relearn walking, swallowing, or writing. Sometimes, the brain can build new connections between the brain cells and repair the damage.

What is memory?

It is the store of things learned and retained from our activity or experience. Our memory is a collection of knowledge, experiences, impressions, skills, habits, and many other things. It gives us the ability to learn and adapt form previous experiences as well as to build relationships. It has a lifelong storage capacity, and no computer of the world can match its performance. Short-term memory is the information that we are currently thinking of and it lasts for only a few seconds. Important things which we have experienced and would not like to forget are transferred from short-term memory into long-term memory.

Why do we feel pain?

Pain is warning signal telling us that there is some danger threatening our health. We feel pain through specific receptors, the sensors, in the skin. These can also be found in the organs and the periosteum. Our body has two pain systems, a fast one and a slow one. If our hand touches a hot object, we withdraw it instinctively without even thinking. This is the fast pain system in action. However, the pain the comes later due to the burning skin or a blister, is transmitted by the slow pain system to the brain.

How do nerve cells transmit signals?

Signal transmission through nerve cells is quite complicated. Like all the other cells, nerve cells also have a cell body with a nucleus. There are fine extended branches known as dendrites and a long 'tail' called the axon on the body of the nerve cells. Axons in the brain are smaller than 1mm,  whereas in the spinal cord they can be as long as 1m. A chemical substance is released through an electrical impulse into the synapses present at the end of the axon. This chemical substance, known as the neurotransmitter, is transferred to the dendrite of another nerve cell and the signal are transmitted.

What is the structure of our brain?

The brain is made up of two halves. Different areas of the brain have different functions. All nerve cells in the brain, about 100 billion of them, are connected to one another and transmit information. This network of the nerve cells is expanded through learning and training. Our brain controls our actions, regulates our sleep, and allows us to feel sensations like pain and joy. If it is damaged, maybe due to a stroke, one has relearn a lot of things like speaking, walking, or eating.

Why do we become dizzy?

Our balancing organs in the inner ear are three  semicircular canals filled with fluid and with fine sensory hair. These hairs sway with our movement and transmit the changes to the brain. The eyes and the foot contact with the floor confirm these movement signals. When we spin around and then stand still, our brain gets confused with different messages: the balancing organs say that we are still moving, but eyes and body convey a different message-and we become dizzy.

Why do we lose our sense of taste when we have a cold?

Our sense of smell in responsible for about 80% of what we taste. The tastebuds present on our tongues are limited to only the basic sensations: sweet, salty, sour, and bitter. All other flavours that we experience come from smell. This is why, when our nose is blocked, as by a cold, most foods seem bland or tasteless. Our sense of smell can normally detect up to 10,000 smells.

How do we judge the direction of a sound?

We can judge the direction of sound only because we have two ears. The sound waves reach the right and the left ear with a small time difference because the ears are at slightly different distances from the source of the sound. The eardrums vibrate, and the ear ossicle transmits the impulse to the inner ear. The inner ear sends it further to the brain where the signals from both ears reach at marginally different times. The brain calculates the direction of the sound from the tiny difference in these times.

Why is the sense of touch important?

Without the sense of touch we would be quite helpless. We would not be able to feel oneself, we would not feel our feet hitting the floor while walking and injuries would go unnoticed because no pain would be felt. We would also be deprived of many pleasant experiences important for social interaction. For blind people the sense of touch is very important. They move around safely by feeling and touching objects in their surroundings. Blind people compensate for their lack of sight by highly developed sense of touch.

How does the eye work?

We can think of the eye as a kind of camera. The iris behind the cornea is light-sensitive and corresponds to the aperture of the camera. This can be set near of far, depending on the amount of light falling on it. The light rays penetrate the lens of the eye, and fall on the retina. Millions of light-sensitive cells convert the light into signals sent to the brain via the optic nerve. These are put together to make images, and are interpreted by the brain. There are two types of cells in the retina: the light-sensitive rods that helps us see in the dark and the less sensitive cones that help us see colours.

What is hallucination?

Whatever we perceive is not always real. For example, in a magic show, we may think what we see is real, but actually it is an illusion. Even our sense of balance can be deceived, and then one would react with uncertainty and dizziness. Hallucinations often occur because things do not happen the way we expect them to, and the brain gets 'confused'.

How can people be identified with the help of fingerprints?

Just as each human being is unique, his grooved fingertips are also unique. Even identical twins do not have the same patterns of grooves on their fingertips. Minor cuts and some skin diseases may cause temporary changes in the patterns, but on healing, the same pattern appears. Since 1901, police have used this knowledge to compare the fingerprints found at a crime site with those of the suspects. In early days, this comparison was done manually and used to be very cumbersome and time-consuming. Today, fingerprints are matched by the computer in a fraction of the time used earlier.

Why can't we tickle ourselves?

The skin, as a sense organ, perceives all kinds of touch sensations as signals. These signals are sent to the brain, are interpreted, and the body reacts accordingly. The brain can differentiate between the touch stimuli that we create ourselves anticipates this type of touch from our hands and prepares itself for it. Since the element of unexpectedness is missing, the body does not respond the same way as it would if someone else were to tickle us.

Why do we have different skin colours?

The colour of a person's skin depends on his environment. In regions with abundant sunlight, a dark skin colour is necessary to provide protection against the harmful UV rays. Light-skinned people in north Europe, where there is very little sunlight, do not need this protection. UV rays are not always harmful: they are needed for the formation of vitamin D, which the body needs for building bones. The darker the skin, the less sunlight can enter the skin and  vitamin D formation is reduced. A dark skin may, therefore, result in Vitamin D deficiency in areas where there is not much sunlight.

why do we get goose pimples?

Goose pimples help in regulating the body temperature. When we are exposed to cold temperature or  get scared, our body hairs stand up so that the air between them can form an insulating layer. Each hair is permanently anchored to the skin with its root. Small muscles are present at these roots, which contract in case of cold or fear. This is visible on the skin as small bumps. The contraction of the muscles also produces heat in the body. This was an excellent warm-up device for our thickly haired carly ancestors who did not wear clothes.

What does the skin do?

Our skin is the largest, heaviest, and the most versatile organ. The skin forms the outer covering of our bodies. The colour of the skin and hair determines our appearance. Without the skin, we would not have any protection against UV rays, injuries, and germs invading from outside. Our sense of touch would not work without it. The skin reacts to the outside stimuli and becomes red, brown, or gets goose pimples. Each person has a unique set of fingerprints, and police can often catch criminals by matching their fingerprints.

How are the bones joined with one another?

Many of our bones are joined to one another through joints, which permit different kinds of movements. The ball joints of our hips and shoulders offer the highest freedom of movement. Here, the ball-shaped end of one bone moves inside the bowl-shaped end of the other. Knees and elbows are joined by means of a hinge joint, which permits only the back and forth movement, like the hinge in a door. Our head sits on the condyloid joint, which allows it to move sideways, front or back, but not rotate. Fluid is present in the joints as a lubricant so that the joints and the bones do not rub against each other.

Which parts of the body does the skeleton protect?

Most of our organs are protected by the skull and the body skeleton. Some of our most sensitive organs lie embedded in the powerful cranial bone of the skull-the brain, the eyes, and the hearing organs. The mouth cavity protects the only movable bone of the skull, the lower jaw. The body skeleton with the ribs fanning out of the backbone protects the area of the chest. Internal organs such as the heart, lung, liver, and spleen are protected behind the rib cage, and the backbone covers the vital spinal cord.

How many bones does a human being have?

An adult has 206 bones, which together weigh about 9 kg. A baby has 350 bones. Many bones in a baby's skeleton are not fully grown, such as those of the skull. Cartilages are present at these points, and turn into bone at a later point. Bones are made up of different materials, and provide strength and elasticity. The bone mass is covered by a periosteum (bone skin), which contains nerves, blood vessels, and bone-building cells. The bone marrow, which makes the red blood cells, is present inside long bones. The longest bone in our body is the thigh bone.

Why do we have a skeleton and how do we move it?

The skeleton gives us our shape and keeps our body upright. Without the bony framework, we would probably have looked like a flabby jellyfish on land, because, after all, one-fifth of our body is water. We differentiate our skeleton into the skull, the body, and the limbs. The first two protect us against injuries form outside, and the limb skeleton primarily takes care of our movement. The bones of the skeleton are joined by ligaments. We move with the help of muscles. Muscles become stiff and ache after a vigorous workout.

What happens when we do not eat?

If we do not eat for some time, we lose weight and feel tired and weak. In the absence of food, the body starts using its fat reserves. Once these are used up and if there is still no or very little food supply form outside, the result is malnutrition. Life-saving processes in the body slow down because there is no fuel/energy to maintain them. We become susceptible to disease-causing germs. We have all seen pictures of children with bloated stomachs and very thin legs. The bloated stomach filled with water is a result of serve malnutrition.

What causes diarrhoea?

Stress, an unhealthy way of life, bacteria, and viruses are the most important causes of intestinal problems. Bacteria and viruses reach the body via food or water and cause sickness, vomiting, and diarrhoea. Diarrhoea is caused because the body fights against these invaders and wants to get rid of them as quickly as possible. Sometimes, with diarrhoea,  We have fever too, since an increase in the body temperature accelerates the healing processes of the body.

How is urine formed?

Urine is a waste product, which is formed in the kidneys after the purification of blood. Kidneys contain millions of very tiny canals, called nephrons, which filter out harmful substances as well as excess water from the blood to form primary urine. This liquid still contains some useful components that are reabsorbed into the body in the kidneys. The remaining fluid that can no longer be used flows through the ureters into the bladder. Once the bladder is full, we need to go to the toilet and relieve ourselves.

What does the large intestine do?

After the absorption of the nutrients in the small intestine, the 1.5m long large intestine absorbs water from the remaining undigested food and converts it into a solid mass. The solid mass of waste matter is stored in the lowermost part of the large intestine, the rectum, and is then excreted as 'stools' through the anus.

Why is the small intestine so long?

The function of the small intestine is to digest the food into simpler nutrients, and to absorb these nutrients. If food stays longer in the small intestine, it will have more time to get digested completely and will also enable the body to absorb all the nutrients. The very long length (more than 6 m) of the small intestine enables the food to stay there longer. The finger-like 'intestine enables the food to stay there longer. The finger-like 'intestinal villi' on the inner wall of the small intestine help in absorbing the nutrients in the bloodstream. The liver and pancreas produce enzymes that travel to the small intestine to help break down proteins, fats, and carbohydrates into sugar. This process is known as metabolism.

eBay

eBay Inc. (NASDAQ symbol: EBAY) is the world’s largest online auction and shopping site. The first appearance of the auction service was in 1995 as AuctionWeb, part of the personal Web site of Pierre Omidyar (see auctions, online and Omidyar, Pierre). Omidyar was surprised at how rap-idly the auction service (which was initially free) grew. After he imposed a modest listing fee, Omidyar found himself receiving thousands of dollars in small checks, and decided that online auctions could become a full-time business.

In September 1997, with Jeff Skoll now on board as president, AuctionWeb officially became eBay. When the company went public in 1998 (at the height of the first “Internet boom”), Omidyar and Skoll became instant mil-lionaires. Meanwhile, eBay took on Margaret (Meg) Whit-man as its new CEO, and under her leadership the company has expanded rapidly through its first decade.

eBay also seeks new markets and revenue through stra-tegic acquisitions. These include payment services such as the very popular PayPal, other e-commerce sites such as Half.com, shopping.com, and rent.com, and even Skype, the Internet phone service. eBay’s net revenue for 2007 was $7.67 billion.

Online Auctions

Auctions remain at the core of eBay’s business, with mil-lions of items in dozens of categories being listed and sold each day. Offerings can range from factory equipment (in the Business & Industrial category) to books, toys, sports memorabilia—even cars and, in a limited fashion, real estate. There are now hundreds of small- to medium-size businesses who derive their revenue from eBay, whether selling their own merchandise, acting as agents for others, or selling software or templates for managing auctions.


eBay does not charge any buyer’s fees, but makes its money by charging the seller for each listing and then a percentage of the selling price. As of 2007 eBay has regional operations in more than 20 countries, including China and India. (Yahoo, a distant second to eBay in online auctions, discontinued its U.S. auction site in mid-2007.)

Beyond Auctions

In recent years eBay has increasingly tried to build a more “traditional” online shopping experience in parallel with its auctions. The Buy It Now feature allows a seller to list an item at a fixed price, either instead of auctioning the item or as an option that can be exercised if there have been no auction bids. Sellers can organize their offerings into regu-lar “stores” to make it easier for customers to browse their merchandise. (Many traditional stores, such as antiques or collectibles dealers, now offer some of their items via their eBay store.) eBay Express, introduced in 2006, adds conve-nience by allowing users to buy selected items from mul-tiple sellers using a standard online shopping cart.


Like Amazon.com, eBay has focused considerable atten-tion on developing more ways for users to comment on their purchases and otherwise contribute content (see user-created content). The most important mechanism is feedback, which lets buyers summarize their opinions of a transaction after its completion. The feedback system has been recently expanded and structured to allow users to give specific ratings on aspects of the transaction, such as accuracy of description and shipping cost and speed. Although not perfect (feedback can be “pumped up” by setting up phony transactions between two accounts), the system does allow buyers to exercise a certain amount of caution before bidding on an expensive item from an unknown seller. eBay also offers various forms of “con-sumer protection” if items are not received or are substan-tially not as described.

Not surprisingly in a marketplace of this size, there is opportunity for various forms of fraud, including sale of counterfeit, defective, or lower-grade merchandise and, on the part of buyers, credit card fraud. eBay has been criticized for not policing fraud adequately. Generally, the service has maintained the position that it is only a facilita-tor of transactions. If it had to guarantee the authenticity of merchandise, it would have to operate like a conventional auction house, with the attendant fees. However, eBay has solicited the help of experts in fields such as coins and stamps to help them identity counterfeit or misdescribed items.

eBay provides a number of forums for user comments, including discussion boards and chat rooms. Users can also write reviews and guides to help, for example, nov-ice collectors who might find themselves overwhelmed by the coin or stamp listings. In mid-2006 eBay expanded its “community content” to include an eBay Community Wiki (see wikis and Wikipedia) and eBay blogs (see blogs and blogging).

eBay is always trying to make it easier to match users’ specific needs with the thousands of potentially relevant offerings. Providing recommendation information (includ-ing user-generated recommendations) is another way to make shopping easier and more satisfying, as has been shown by Amazon.com. Another possible way to get a big-ger share of users’ day-to-day purchases is to make eBay available on mobile devices as well as linking it to sites such as Facebook, where young people in particular spend much of their time (see social networking.)


Long-time eBay CEO Meg Whitman stepped down in March 2008, while calling for innovation to reinvigorate a company that many observers now consider to be staid and “old school” in the age of Web 2.0. Whitman’s succes-sor, John Donahoe, has announced a new fee structure and new ways of searching for and displaying listings—devel-opments that have provoked some controversy in the seller community.

What happens to the food after it is swallowed?

After the food has been chewed and mixed with saliva, it reaches the stomach through the oesophagus. The food is prepared for actual digestion in the small intestine, which is connected to the large intestine, and ends in the rectum. The undigested remains of the food and urine are excreted from the body. We can survive without water only for a few days, but the body can manage without food for quite some time. If the starvation goes on for a very long time, the body becomes weak and prone to diseases.

What are organs?

Organs are parts of the body having specific tasks. An example is the intestine, in which food is broken down and the nutrients are absorbed in the blood. Another important organ is the liver, which utilizes the components of food. Other organs are the kidneys, the spleen, the heart, and our biggest  organ, the skin. They are all made up of different kinds of tissues, such as muscular tissue, fatty or supportive tissue, and blood vessels. The tissue in each organ is specifically designed to perform the tasks assigned to that organ. Thus, the muscular tissue of the heart is different and performs different functions as compared to that in the upper thigh. Each organ interacts with other organs to keep the body healthy.

What are cells made of?

The different cells of our body have very different tasks, but they are all similar in their structure. They have a cell wall or a cell membrane, which protects the inner matter of the cell and controls what goes in the cell and what comes out of it. The nucleus inside the cell controls all the processes in the cell. The energy for these processes comes from mitochondria, the power house of the cell. They are responsible for cell respiration. The endoplasmic reticulum takes care of the conversion of substances and for detoxifying the cells. All these organelles are embedded in the liquid cytoplasm inside the cell. If we drink less fluids, the cytoplasm will dry out and the cell may die.

Where does the oxygen in the blood come from?

When we breath, the oxygen reaches our lungs via the mouth, nose, and trachea. The lungs have a number of very tiny cavities known as air sacs which are covered by a network of very fine blood vessels. An exchange of gases takes place here. Impure blood reaches these capillaries and releases the waste gas carbon dioxide in the air sacs. This is exhaled out of the body, and freshly inhaled oxygen is absorbed into the air sacs. This oxygen is released into the blood via the capillaries.

How does the heart work?

The heart, a hollow organ with four chambers, can be imagined as an unbelievably strong pump. It is about the same size as a fist. Electrical signals coming from the brain cause the heart muscle to contract about 70 times in a minute in an adult. The contractions are more frequent in children and while we are playing sports. These contractions pump the blood through the whole body through the circulatory system. This system consists of two types of vessels:arteries with blood rich in oxygen and veins with blood poor in oxygen. While the arteries blood supplies oxygen to every cell in the body, the venous blood is sent to the lungs where the it is purified by removing the waste product carbon dioxide and absorbing new oxygen.

Why do we need blood?

Our body consists of millions of cells, which must be supplied with water properly. This supply is the responsibility of the blood. The red blood cells transport vital oxygen(O2) around the body. The blood also absorbs nutrients from the digestive tract, distributes them to the organs, and in return, takes away the waste products from the organs. Blood contains platelets that seal the wounds and white blood cells that helps us fight disease-causing germs.

Why is drinking water important for humans?

The human body is made up of 80% water, which is present in blood and other cells. Since we lose a lot o fluid through sweat, urine, and breath, we need to replenish it constantly. Drinking less water can cause immediate problems. The body cells become dry, and the skin wrinkles. Blood becomes thicker, and the heart has to make effort to pump it through the body. Since the blood is responsible for transporting oxygen around the body, oxygen is not supplied adequately to the organs. The heart and the brain react immediately to a hack of oxygen-they get damaged in just a few minutes.

What is so special about our thumb?

Unlike other animals, out thumb is opposable, which means that it has free movement and  can be placed opposite the fingers of the same hand. This helps us to grip things securely and lets us do delicate jobs like threading a needle. Our grooved fingertips prevent smooth tings form slipping away. This movement of the hand, combined with the freely moving shoulder joint and the upright posture, gave our ancestors a development advantage: tools or weapons could be used for a specific purpose with great power.

Is out brain bigger than that of dinosaurs?

Dinosaurs had small brains, much smaller than the human brain. The dinosaur brain often weighed only a thousandth of their huge body mass. An adult human brain is about one-fifth of its body mass, on an average around 100 g. Since the early hominid creatures, whose skeletons were found in Africa, the brain mass of humans has increased threefold. In comparison, the size of the brains of other mammals has hardly changed in the course of millions of years.

Do animals use tools?

Animals do make use of tools for getting food or for protecting themselves. Apes reach for sticks or stones when threatened, sea otters break their favorite food, the shells, with the help of stones, and a species of finches picks  out insects form tree trunks, with a long cactus quill. for generations the young ones of animals have watched the traits of the adults and imitated them exactly. Humans, on the other hand, may change the traits according to personal requirements. Humans advance and discover new things by adapting and learning. It is hard to believe that the hand axe made by prehistoric man out of stone has today given rise to sharp knives, chainsaws, and many other things. 

Who were the Neanderthals?

The Neanderthals were people who lived 130,000-30,000 years ago, but then died out due to unknown reasons. One theory is that other lines of humans were stronger and eliminated them. The Neanderthals were about 1.70 m tall, had a heavily built body and were very powerful. They needed this power and strength to hunt woolly mammoths and rhinoceros with their home-made spears and knives. They made clothes of animal skins, lived in caves, and used fire. Their name is derived from the place where their remains were found, the Neander vallynear Dusseldorf.

Did humans evolve from the apes?

Today, one can think of the apes and humans as cousins. They have common ancestors, but have not descended directly from each other. About 5-7 million years ago, a line of man-like apes grow apart, and evolved independently of the other apes. The oldest, almost completely intact skeleton of an upright ancestor of human-the Australopithecus-was found in 1974 in Ethiopia(Africa). The scientists named it 'Lucy'.

What differentiates human from animals?

Biologists classify humans as animals and part of the animal kingdom. Like our nearest relatives, the apes, humans are also mammals. Humans have evolved from apes, but there are features that differentiate us form other animals-including apes. These include the upright walk, our Opposable thumb, our special ability to communicate by a language, and our highly developed brain. Our brain allowed our ancestors, like the Neanderthals, to  invent tools

Danger and death are a part of life

Unfortunately, most people become severely ill at least once in their lifetime. People who drink alcohol, smoke, or take drugs have a higher risk of falling ill. There are some diseases, like rheumatism, which occur mostly in the old age: though,in rare cases, young people can also get them. While it is ture that all of us have to die, the death of loved one is always a big loss.

About health and disease

Sickness is annoying and tiring, even if it is just a common cold or an allergy. If we fall sick, we have to take some medicine or get operated upon. Our body is continuously fighting diseases, so it is very important to be fit. To be fit, you need to exercise in fresh air, eat healthy, and brush your teeth regularly.

Love+Sex= Childeren?

In today's modern world, nobody believes that children are brought by storks! When a man and a woman have sex with each other, with or without love, the woman may become pregnant and have a baby. The baby grows up and discovers his/her own sexuality in puberty. This is the first step towards becoming an adult.

Nothing works without a brain

Our brain is a marvel. It organizes our thoughts, analyzes information received by our senses, and sends commands to all parts of the body. Sometimes it also creates unreal experiences for us like hallucinations. The brain can work properly only if it is supplied adequately with nutrition. Bodily functions fail if this supply is interrupted as a result of illness.

Cells, bones, muscles, and organs

We all know very well that without drinking enough fluids, the blood cannot supply adequate oxygen to the body cells. This supply of oxygen is sometimes even more important than eating. Excessive weight also causes problems. The bones need to support more weight and the muscles must work more. Although the sun is very important for our health, athletes spending a lot of time  in the sun must protect their skin from sunlight.

What differentiates humans from animals?

Our body structure shows an important difference between us and out nearest relatives, the apes-the upright walk. Our genetic material differs form that of a chimpanzee only by a hundredth. But this 1% accounts for our superior thinking and culture and enables us to develop further.