What Is Crop Rotation And What Are The Benefits Of Crop Rotation

The land that we need for growing food is very important. We can't afford to spoil it. There are many ways in which farmers could make better use of the land and grow good crops without the help of factory-made chemicals.
If it is farmed with care, the land will go on giving us enough food to eat for thousands of years to come.
One method of careful farming is called crop rotation.
Different kinds of plants take different nutrients from the soil and leave others behind. The same crop planted year after year takes out the same nutrients.
But different crops, like corn and alfalfa, can be planted on the same piece of land.
One year, corn is planted. This will take out certain nutrients from the soil. The following year, alfalfa will be planted. The alfalfa will put back the nutrients absorbed by the corn.

Health Care Careers List - List of Jobs in The Medical Field

Medical specialists are medical professionals who have knowledge, education, and training in a particular field of medicine.
In the following lists are presented some types of medical specialists and their areas of expertise.

List of medical careers


Area of expertise: Treatment of allergies


Area of expertise: Administration of anesthetics for surgery


Area of expertise: Diseases of the heart and circulatory system

Pulmonary Specialist

Area of expertise: Diseases of the lungs and chest


Area of expertise: Diseases of skin, hair, and nails

Emergency Medicine Specialist

Area of expertise: Emergency treatment of acute illnesses and injuries


Area of expertise: Causes, transmission, and control of infectious diseases

Family Physician

Area of expertise: Ongoing health care for persons of all ages


Area of expertise: Diseases of the digestive system

General Surgeon

Area of expertise: Surgical treatment of diseases of the abdomen, breast, and other areas


Area of expertise: Diseases of the female reproductive organs


Area of expertise: Diseases of the blood, bone marrow, and lymph tissues


Area of expertise: Nonsurgical treatment of diseases of the internal organs


Area of expertise: Diseases of the kidney


Area of expertise: Diseases of the brain and nervous system


Area of expertise: Surgical treatment of diseases of the brain and spinal cord 


Area of expertise: Health care for pregnancy, labor, and childbirth


Area of expertise: Treatment of cancer


Area of expertise: Diseases of the eye


Area of expertise: Diseases of the bones, joints, and muscles


Area of expertise: Diseases of the ear, nose, throat, and neck


Area of expertise: Study of biopsy specimens and body fluids


Area of expertise: Health care of infants, children, and adolescents


Area of expertise: Rehabilitation of patients following illness or injury

Plastic Surgeon

Area of expertise: Cosmetic surgery and surgical reconstruction


Area of expertise: Disorders of the foot


Area of expertise: Diseases of the anus, rectum, and colon


Area of expertise: Treatment of mental disorders


Area of expertise: Study of X ray and ultrasound


Area of expertise: Treatment of rheumatic diseases


Area of expertise: Diseases of the urinary tract and the male reproductive organs

Vascular Surgeon

Area of expertise: Surgical treatment of diseases of blood vessels

What is Tallying? - Tallying and Tally Marks

Can you imagine a time when people did not use numbers?
The first people on earth lived by hunting wild animals and collecting wild fruit and nuts.
They had no need to count.
Numbers did not matter to them.
But then, about 11,000 years ago, herdsmen began to keep flocks of sheep and goats.
They had to be able to count so that they would know if any of their animals were missing.
The first calculations were made by counting in ones—'1 and 1 and 1,' and soon.

This method of counting is called tallying. 

One way herdsmen used to tally was to put a stone on a pile for each animal.
Other ways were to tie knots in a length of rope, cut notches in sticks, or make scratches on a rock. Each stone, knot, notch, or scratch represented one sheep or goat.

Space Probes Information - Voyager 1 and Voyager 2 - Voyage of discovery

On August 20, 1977, Voyager 2 was launched into space.
Two weeks later, Voyager 1 set off. 

The two Voyagers were types of unmanned spacecraft called space probes.
Their mission was to travel to the more distant planets of the solar system and send information about them back to earth.
No spacecraft had ever traveled so far into space before.
Voyagers 1 and 2 each carried 11 instruments. 
These included remote-controlled computers, television cameras, ray detectors, infrared and ultraviolet sensors, and a magnetometer.
These instruments recorded and sent back information about our solar system.
Technology has developed quickly since the Voyager probes were launched. That equipment is now out of date. A modern, desktop computer is more powerful than the Voyager computers. Scientists have updated the probes' computer programs and made repairs from earth by remote control.
In 1980, three years after its launch, Voyager 1 reached Titan, Saturn's largest moon.
The probe sent back information to earth. It found chemicals like those on earth. But Titan is too cold for these chemicals to develop into living things as they have done on earth.

The journey of Voyager 2

1. On August 20, 1977, Voyager 2 was launched from earth at a speed of just over 24,800 miles (40,000 kilometers) per hour. The idea was to use the gravity, or pull, of each planet it passed to catapult the space probe faster and faster through space, from one planet to the next.
2. On July 9 1979, Voyager 2 came closest to Jupiter and discovered it has three more moons. The planet’s gravitational pull increased the speed of Voyager 2 to around 30.700 miles (48.000 kilometers) per hour.
3. It was August 25, 1981, and Voyager 2 passed Saturn at a speed of 33,700 miles (54,400 kilometers) per hour. Then we learned that Saturn has nine more moons that it was known to have.
4. At Uranus, on January 24, 1986, Voyager 2 discovered 10 new moons. Its speed was now 36,700 miles (59,200 kilometers) per hour.
5. Mission completed! On August 25, 1989, Voyager 2 passed within 3,000 miles (4,800 kilometers) of Neptune's cloud top.
We learned that this planet is a hostile world.
No living thing could survive here.
Twelve years after it left Earth, Voyager 2 reached Neptune. It had traveled nearly 4.4 billion miles (7.1 billion kilometers) and arrived four minutes early!
Voyager 2 carries its own message—a record of voices and other sounds from earth— just in case there is life beyond our solar system.
Voyager 2 is expected to enter interstellar space within a few years of 2016. It is not headed toward any particular star, although in roughly 40,000 years it should pass 1.7 light-years (9.7 trillion miles) from the star Ross 248.
Voyager 2 is expected to keep transmitting weak radio messages until at least 2025, over 48 years after it was launched.

What is a Space Probe? - Information on Space Probes

Until now, human beings have traveled into space only as far as the moon, about 236,000 miles (380,000 kilometers) away.
But robot space crafts are sent very much farther.
These have visited the distant planets.
These robot space crafts are called space probes.

What is a Space Probe?

Space probes carry cameras and many kinds of instruments to study the planets they visit. They send information back to earth by radio.
Probes must be launched from the earth at a very great speed—more than 24,800 miles (40,000 kilometers) an hour.
Then they can escape from the earth's gravity.
Aiming the probe is very difficult, because the planet it must reach is always moving. The probe must be aimed so that it reaches a point in space almost at the same time as its target. It must do this after a journey of many millions of miles, lasting for years.

Voyager space probes

It is an astonishing fact that most probes sent to the planets have reached their targets. In 1989, the American probe Voyager 2 flew past the planet Neptune almost exactly on time, after a 12-year journey. The planet was nearly 3.1 billion miles (5 billion kilometers) away from earth at the time. From this distance, the radio waves from Voyager took over four hours to reach the earth.
A Voyager probe photographed Saturn on its journey into the outer solar system. It used nuclear generators to make electricity.
Solar cells couldn’t be used because sunlight is too weak near Saturn.

Venera space probe

Most probes study a planet as they fly past it. But some actually land on the planet and report back from its surface.
A Russian probe, called Venera, was the first to land on a planet. It parachuted down to Venus in 1970. Since then, several Venera probes have sent back pictures of its surface.
Two American Viking probes landed on Mars in 1976. They sent back pictures and reported on the Martian weather. They also examined the soil for signs of life—but didn't find any!

What is the Function of the Kidneys and How do Kidneys Work?

The kidney filters body fluids within the nephron units and expels wastes via the ureter.

Kidney is one of a pair of organs located at the back of the abdomen, against the strong muscles next to the spine, and behind the intestines and other organs.
The adrenal glands lie on top of the kidneys.
Each kidney weighs about 5 ounces (140g) and is about 4 inches (10cm) long in the average adult.
Its inner structure, which is called the renal pelvis, collects urine as it is formed and passes it out of the kidney to the bladder via the ureter.
The renal pelvis also is connected to the artery and vein that carry blood to and from the kidney.

What is the function of the Kidneys?

The kidneys filter out water and also unwanted substances in the blood.
These substances are produced by the normal working of the body.
They are excreted by the kidneys in the form of urine.
The kidneys also keep the salts and water of the body in correct balance.

How do kidneys work?

The blood passes through each kidney under high pressure.
The blood is filtered by the glomeruli, special structures in the kidney containing clusters of capillaries that collect water, salts, and unwanted substances.
The filtrate passes along a fine tube, the nephron (of which there are approximately one million in each kidney), which reabsorbs any of the water, glucose, and salts that the body still re-quires and allows the rest to pass into the pelvis of the kidney as urine.

Keratitis Definition – What causes Keratitis?

What is Keratitis?

Keratitis is an inflammation of the cornea, the transparent membrane that forms the front of the eye. If the condition occurs suddenly, it causes pain, sensitivity to light (photophobia), and watering of the eye. If atitis develops gradually, only minor discomfort may result.
Opaque patches in the cornea can cause the patient vision to blur.

What causes keratitis?

Keratitis is often a symptom of more general disorder. Virus infections, such as trachoma (chronic conjunctivitis) or herpes simplex may infect the cornea.
Bacteria infection may follow any eye wound.
Keratitis is also a consequence of congenital syphilis or, rarely, tuberculosis.
It most often occurs in children between the ages of 5 and 15.
A deficiency of vitamin A causes dryness of the cornea, which makes it more susceptible to infection.

Keratitis Treatment

Further damage to the cornea can be prevented with eye drops, containing the drug atropine, to dilate the pupil.
Corticosteroid drugs reduce the inflammation.
It is essential for the eyes to be examined by an ophthalmologist.

Kaposi’s Sarcoma Definition - What is Kaposi’s Sarcoma?

Kaposi’s Sarcoma is a malignant tumor, which usually begins as soft, purplish, raised lesions on the feet and spreads through the lymphatic system.
Before 1980, this tumor was seen only in elderly Italian or Jewish men or in younger people from equatorial Africa.
It was a relatively rare disease.
Now, however, a specific, more severe form of Kaposi’s sarcoma (KS), associated with Acquired Immune Deficiency Syndrome (AIDS), has reached epidemic proportions in the United States and several other countries.
The treatment for the milder form of KS is electron beam radiotherapy, while deeper lesions are treated using X-ray therapy.
The more severe type of KS is sometimes treated with antimicrobial drugs and other forms of treatment to help re-store the immune system within the cells.

Albinism Definition - What is Albinism and What Causes Albinism?

Albinism is the lack of brown pigment - melanin, and a person with such property is called albino. The appearance of albinism can also be found in Africa.
Albinism may be partly inherited. Many people are not albinos, but passed the traits of albinism to their children.

What causes albinism?

The color of the skin, hair, eyes, etc.. in humans is the result of the interaction of various substances in the body.
One are the substances that form the basis of future color, and other are the enzymes that act on that basis.
If someone doesn’t has one of these two substances, or their relationship is disturbed, the result is albinism.
The name derives from the Latin word albus, meaning white.

Albinism symptoms

Albinos have pink eyes, because the red blood in the retina of the eye.
Albinos eyes are very sensitive to light. That's why they keep flashing and keep partially lowered eyelids.
Hair and body hair of Albinos are white.
Even the tissues in the body are white, such as brain and spinal cord.

Albinism exists not only in humans but also in animals of all species. 
It was also found in birds.
Albinos are probably white mice, rats and rabbits, which we all know. There are people who have seen albinos squirrel and even a giraffe albino!

What Are Human Bones Made of?

Strength of normal, healthy human bones is amazing. The bones must be strong, because they make the skeleton which holds the whole body.
Bones vary in shape and size depending on the type of animal to which they belong. Fish and small birds have small bones.
The elephant has bones that are difficult few hundred pounds!

Bone composition

All the bones are of similar composition.
Bone is hard, grey-white color and two-thirds of bone tissue are inorganic or mineral substances, especially lime phosphate.
This gives the bone its hardness, but at the same time makes them brittle.
The remaining third of the bone makes organic matter. It gives bone strength and resistance to fracture. The center of the bone is spongy and filled with bone marrow.
Some of bone marrow fat is stored in the second part and the core creates blood cells. In the bones there is a small amount of water, which, with the aging of the body, gradually disappears.
With less water in the bones, greater is the amount of minerals, causing bones to become brittle and break after slowly coming together.

Interesting Facts About Bones

  • Humans have about 300 bones when born. Some of these, fuse together creating a single bone. When maturity is reached, humans have 206 bones in the body.
  • The teeth are not counted as bones.
  • The greatest bone in the body, “the femur”, is around 1/4 of the persons height. 
  • The smallest bone in the body is the stapes (stirrup) located in the middle ear, with size around 1/10 of an inch (2.8 millimetres).
  • The only bone which is full-grown at birth is the stapes bone, and is situated in the ear.
  • Hand, fingers and wrist make the area of the body with most bones - 54.
  • The bones of an adult person make approximately 14 % of the total body weight.
  • The bones are made of approximately 75 % of water
  • Human bones start to grow from birth, until mid 20's. 
  • Broken bones re-grow and repair themselves. 
  • The human skeletal system has six major functions: 1. production of blood cells, 2. support, 3. movement, 4. protection, 5. storage of ions and 6. endocrine regulation.
  • The Bone marrow makes up 4% of a human body mass.

Jet Lag Definition - What is Jet Lag and How to Avoid Jet Lag?

Jet lag is the disorientation in the normal biological circadian rhythm, which is experienced by a person traveling from one time zone to another with more than four hours difference.
The greater the time difference, the greater the degree of disorientation.

Jet lag symptoms

During the time the traveler needs for his or her body to adjust to new eating and sleeping patterns, he or she may feel disoriented, tired, and “out of sync” with the new schedule, that is, sleepy during the day, awake at night, and hungry at inconvenient hours.
The body temperature may also no longer be synchronized with day and night requirements.

How to avoid jet lag

The symptoms of jet lag are often made worse by overeating and by a high consumption of alcohol during the flight, which is known to cause dehydration.
It is, therefore, advisable to drink plenty of nonalcoholic fluids during a long flight.
Some people believe that jet lag may be completely avoided by abstaining totally from alcohol and eating as lightly as possible during the flight, preferably on the schedule of mealtimes in the destination time zone.
Additionally, a diet developed by some researches is thought by some travelers to help adjust the circadian rhythms prior to flying by altering the intake of food and caffeine for several days before travel. There is no medical evidence to support this; people are advised to check with their physician before following the diet, since it could have detrimental effects on certain health conditions, such as diabetes.

Jet Lag Treatment

The body may take a long time to adjust to a new circadian rhythm, possibly as long as 10 days.
If the stay in the new time zone is to be brief, it is often advisable not to try to adapt, but rather to retain the familiar rhythm, even at the expense of unusual hours.
On a business trip this generally means that at least some working hours fall within commercial times.
A longer stay in the new time zone requires adaptation.
A mild sedative, prescribed by a physician, may help to ensure proper sleep for a few nights after arrival. The body will adjust its eating habits to conform with the new sleeping pattern.
Jaundice Definition - What is Jaundice?

Jaundice Definition - What is Jaundice?

Jaundice (Icterus) is a condition characterized by a yellowing of the skin and the whites of the eyes.
Jaundice is a symptom, not a disease in itself.
The yellow coloration is caused by an excess in the body of the bile pigment bilirubin.
Normally, bilirubin is formed by the breakdown of hemoglobin during the destruction of worn-out red blood cells. It is then excreted by the liver into the bile via the bile ducts.

What causes high bilirubin in the body?

High bilirubin can be caused by:
  • Overproduction of bilirubin;
  • Failure of the liver to metabolize bilirubin or to excrete it;
  • Blockage of the bile ducts.
Overproduction of bilirubin may be caused by the destruction of an excessive number of red blood cells (hemolytic anemia).
The liver then can’t excrete bilirubin fast enough.
This occurs in malaria, thalassemia, and hemolytic disease of the newborn.
Jaundice may also result from various diseases that can affect the liver, such as hepatitis, cirrhosis or cancer.
If the bile ducts become blocked, bile can’t be excreted and jaundice occurs.
The ducts may be blocked by inflammation and in fection (cholangitis); a gallstone (cholelithiasis); or cancer of the pancreas or the common bile duct.
Occasionally a drug such as chlorpromazine may inhibit bilirubin excretion by the liver.

Jaundice in Babies

Mild jaundice occurs as a common and normal condition in newborn babies because at birth there is both a deficiency in the enzyme that helps to excrete bilirubin and also an increased breakdown of red blood cells.
In babies, the condition generally disappears within a few days as the enzyme is formed.
Rarely, this enzyme deficiency can also cause jaundice in adults.

Symptoms of Jaundice

Symptoms of Jaundice depend on the specific cause of the jaundice.
In many forms of the condition, bilirubin is excreted in the urine, which becomes dark brown in color.
If the excretion of bile is obstructed, stools are almost white and the digestion of fat is impaired.
If the condition has been present for some time, intense localized itching may occur due to blockage of the bile ducts.

How are the causes of jaundice diagnosed?

Diagnosis requires special blood tests, in which a physician determines whether the liver is diseased; whether the bilirubin is being correctly metabolized by the liver cells; and whether there is any abnormal breakdown of the red blood cells.
The urine is examined for bilirubin, and the feces for pale coloration (which would indicate an obstruction to bile excretion).
It Is sometimes necessary to perform a liver biopsy to examine Cells under a microscope or to examine the liver, gallbladder, and bile ducts with ultrasound to locate gallstones.