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

The sex of the baby is determined by the chromosomes. Usually, all of us have 23 pairs of 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 a sperm with a 'Y' chromosome fertilize the egg, then the chromosome combination for the baby would by XY: a boy. If an 'X  sperm' fertilize the egg, the result is XX: a girl. It is clear, therefore, that the sex of the baby is determined by the father.

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 the blood circulation of the child with that of the mother. The foetus, as the unborn child is called , gets nutrients and oxygen through 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 .

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, an change in the 21st chromosome, cause Down syndrome in the child. It is important to ensure that people with disabilities are not discriminated against in our society.

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 born with a disability.

How does fertilization occur ?

After a man and 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 air: 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.

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 membranes 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.

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 give us the ability to learn and adapt from previous experiences as well as to build relationships. It has a lifelong storage capacity, and no computer of the wold 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.

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 reaso 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 simple things like awaking, swallowing, or writing. Sometimes, the brain can build new connections between the brain cells and repair the damage.

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 fro more than 12 hours a day, some old people need only 5-6 hours of sleep.

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 in 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 damages, maybe due to a stroke, one has to relearn a lot of things like speaking, walking, or eating.

How do nerve cells transmit signals?

Signal transmission through nerve cells in quite complicated. Like all 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 1 mm, whereas in the spinal cord they can be as long as 1 m . A chemical substance is released through an electrical impulse into the synapse 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 signals are transmitted.

Why do we feel pain?

Pain is a 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 that comes later due to the burning skin or a blister, is transmitted by the slow pain system to the brain

Why do we have different skin colors?

The color of a person’s skin depends on his environment. In regions with abundant sunlight, a dark skin color 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 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 and the stimuli given by others. If we try to tickle ourselves, our brain 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.

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.

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 color of the skin and hair determines our appearance. Without the skin, we should not have any protection against UV 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.

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 curly ancestors who did not wear clothes.

Why does the skin get tanned in the sun?

In the summers, our skin is often exposed to UV radiation from strong sun that can damage the skin. A pigment, called melanin, is produced in the skin to protect against the harmful radiations from the sun. The more this pigment is produced, the darker, i.e. more tanned , is the skin and the higher is the protection against sunburn. That is why, many light-skinned people get sunburn very quickly. Sunburn always means damage to the skin. Even when the skin has apparently recovered from the burn, it remains damaged from inside and there is always a high risk of getting skin cancer later.

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

The skeleton give 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 from 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.

How many bones does a human being have?

An adult has 206 bones, which together weight about 9 kg. A baby has 350 bones. Many bones in a baby’s skeleton are not full 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 nerves, Blood vessels, and bone –building cells. Te bone marrow, which makes the red blood cells, is present inside long bones. The longest bone in our body is the thigh bone.

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 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 a 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.

How do muscle works?

The muscles are connected with bones through rope-like tendons and can only be contracted. Most of the muscles work in pairs so the different types of movements are possible. Such a muscle pair is needed, for instance, to bend the elbow. Which one muscle, the biceps, contracts and bends the arm, the other muscle, the triceps, relaxes. Exactly the reverse happens when the arm is stretched. The signal for muscle contraction or relaxation comes from the brain, which is controlled by us. The musculature of the internal organs works by itself since we cannot control these muscles.

What is muscle stiffness?

Muscle stiffness is a painful result of over strained muscle. It frequently occurs on days when the body suffers very strong physical stress. Physical strain causes micro cracks in the muscle fibers, which slowly get filled with water. As a result of this , the tissue gets stretched, which causes pain, and give rise to inflammation. After a few days of recuperation, the pain usually subsides.

Did you know : the only bone not connected with the rest of the skeleton is the hyoid bone? It lies at the root of the tongue. And the eye muscles move about 100,000 times a day? Most of the movements take place in the night while dreaming.

What happened after the discovery of America ?

After it became know in Europe that there was a continent in the west, people wanted to find out how big it was and what it had to offer. In the beginning, the original inhabitants of the continent greeted the visitors as friends. But soon the Europeans started migrating to the new world  in large groups, and the newly discovered areas became colonies of countries such as England, France, and Spain. In North America, many wars were fought between the White settlers and the North American Indians; further in the south, gruesome conquerors such as Cortez and Pizzaro attached and conquered the Aztecs and the Incas. Valuable goods were brought to Europe, but often the pirates captured the ships

Why did so many Europeans migrate to America ?

the immigrants had many reasons to migrate. The first people to venture on the long voyage to the new continent in . were called the Pilgrim Fathers, whose religious beliefs were suppressed in England. However, the main reason for the migration was the bitter poverty that was prevalent in many countries of Europe in the 19th century. There was a large famine in Ireland in 1845-1849 due to the potato blight, as a result of which about 1 million Irish left their homes in the hope of a better life in america. When gold was found in California in 1850, many cam ether driven by greed and a spirit of adventure.

What caused the Great Indian Wars ?

When it became clear to the native Indians of North America that the people coming in were not visitors, but had come to stay permanently, they started protesting and this frequently led to battles. But the individual native Indian races were often in dispute amongst themselves. Only when they combined into the tribes that they were able to win against the heavily armed army of the White Settlers. One of their greatest wins was in 1876 in the battle of Little Big Horn (today's US state of Montana). But finally, the native Indian (North American ) tribes were defeated and pushed into their reservations.

Who invented the scale?

In 5000 BC. The Egyptians were the first people to build the beam balance and weight goods. Pans hung from both ends of a balance beam. In one pan the load to be weighed was placed, and in the second pan the weights were put, until both the pans were perfectly balanced. The earliest and the smallest unit of weight was a gain of wheat and it was used to weigh gold. The steelyard has been used as a weighing device since 2000 BC. It has two arms of different lengths and uses a counterweight that slides along the calibrated longer arm to counterbalance the load on the other arm and indicate its weight.

What is triangular trade?

Triangular trade means trading through a third party. There is no direct exchange between two trading partners. Instead, dealers buy the goods from an overseas market and sell them in the home market to the consumer. They are, therefore, an intermediary between the manufacture and the consumer and make a living from the profit made by selling the goods. The term triangular trade is often associated with the trading of slaves in the 18^th century: Europeans traveled to Africa with goods like weapons, cloth, salt, bought salves in return, and sold them in America in exchange for cane sugar product such as rum.

How were distance measured?

In ancient times, the Egyptians and the Babylonian used their body parts as measurement tools. A very old unit of measurement is the cubit : It is the length from the elbow to the tip of the middle finger. Smaller lengths were specified by the length of a finger or the span of the palm-this is the stretched hand from the tip of the thumb to that of the little finger. The foot was also used to measure distances – just as the step and the double step. The Romans also use these measures. A Roman mile had a thousand double steps, and each double step measured five Roman feet.

How was trade done earlier ?

The Stone Age man was not aware of any trading. They hunted for their own requirements, later they started cultivating fields. When the wild animals became scarce in a particular area of the crop was bad, tribes moved forwards. Eventually, people cam across the other groups that cultivated and produced different things - an exchange of goods started. For the exchange of goods, the value of the goods had to be determined . This could not be done without numbers, measures, and weights. Scales and calculating devices such as the Abacus were invented, the trading activity expanded and a real triangular trade arose

Who invented the numbers ?

The first written number system is about 5000 years old and comes from the Sumerians in Mesopotamia. But man wanted to specify quantities even much earlier: of the animals killed or of mushrooms. In the beginning, man counted using the finger joints on each hand. Even today, young children are taught to count on their fingers. It is known about the Stone Age man that he used tallies by cutting notches in wood, bones, and stones. Similar tally sticks were even used in England till the 19th century.

How does an abacus work ?

Abacus is the most ancient tool used for the purpose of calculations. It consists of a frame with rods or wires, on which spheres are beaded. The value of the spheres depends on the rod, on which they are beaded: units, tens, hundreds, and so on. By moving the balls on can do the four simple mathematical operations as well as more difficult calculations. the result can then be read from the position of the balls. Abacus is used even today in some countries of retailers, such as China and Russia.

How does a ferry work without an engine ?

Ferries without engines are driven by the flow of water. They are attached to a wire cable, which is spanned across the river by means of two short ropes. When the ferryman shortens one of the two short ropes with the help of a device called 'winch', the ferry is tilted at an angle to the current, and the force of  the current propels the ferry across the river

How is energy obtained from high and low tides ?

High and low tides come alternately, that is, one after the other. In high tides, the level of water rises and covers a part of the coast, and in low tides it flows away again. This energy of the tides is sued to run turbines. Special water turbines are used in tidal power plants. Water - rising in case of high tides and receding in case of low tides - can flow through these turbines in both the directions. electricity is generated in tidal power plants due to the rotary movement of the turbines. These power plants need a tidal hub - the difference in the height of water between high and low tides - of more than 5 m to be able to work economically. Such a power plant is int he French Bretagne, in St. Malo.Here, the tidal hub is at 12-15

What is hydro power ?

Water has huge power. We can feel this one our bodies when we cross a sea or river. The power we get from water is called hydro-power. Hydro-power has been one of the first force used by human beings to simplify their work. For example, tasks such as turning wheat into flour, processing wood to make paper, making textile, and turning hard metals into various interesting shapes, which were difficult to do earlier, have been made easy by using hydro-power. Dams are made by erecting huge walls in water to generate electricity. Even today there are ferries and boats without engines that use the force of flowing water. Even tides in the oceans can be used to produce energy.

How does a watermill work ?

A watermill uses a large wooden or metal wheel to generate power. It consists of many small blades, over which the flowing water of a stream run; this wheel is called the 'water wheel'. The flowing water rotates the wheel. This rotational movement produces electricity when connected to a generator. Although mills were used to generate hydro power in earlier times in all countries, people in the underdeveloped countries uses them even today. Electricity produced in such a manner is pollution free and does not harm our environment.

How is electricity generated by using a dam ?

Dam walls are mostly made of a material called concrete. These dams retain a large amount of water. The retained water puts very high pressure on the lowermost layers of water. If the water in these lowermost layers is diverted, it flows at a very high speed, and hence a high energy is produced with the hep of a device called turbine. In the turbine, the energy is sued to generate  electricity. The type of energy we can reuse since it is unlimited in nature is called renewable energy, such as the energy from the sun, wind, and water. Hydro-power is currently the only renewable energy that is used to a large extent. In Austria, approximately half of the electricity is generated by hydro-power, while in Norway all the electricity is generated by hydro-power

(all the image from google image credit goes to google)

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 the the toilet and relieve ourselves.

What happens when we don 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 start using its fat reserves. Once these are used up and if there is still nor or very little food supply from 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 stomach and very thing legs. The  bloated stomach filled with water is a result of server 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, vomitting, 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.