Agriculture and domestication probably started in the Fertile Crescent (the Nile Valley, The Levant and Mesopotamia). The area called Fertile Crescent is now in the countries of Iraq, Syria, Turkey, Jordan, Lebanon, Israel, and Egypt. Wheat and barley are some of the first crops people grew. People probably started agriculture slowly by planting a few crops, but still gathered many foods from the wild. People may have started farming because the weather and soil began to change. Farming can feed many more people than hunter-gatherers can feed on the same amount of land.
Arable farming means growing crops. This would include wheat or vegetables. Growing fruit means having orchards devoted to fruit. They cannot be switched easily with growing field crops. Therefore they are not classed as arable land in the statistics.
Agriculture is not only growing food for people and animals, but also growing other things like flowers and nursery plants, manure or dung, animal hides (skins or furs), leather, animals, fungi, fibers (cotton, wool, hemp, and flax), biofuel , and drugs (biopharmaceuticals, marijuana, opium).
Many people still live by subsistence agriculture, on a small farm. They can only grow enough food to feed the farmer, his family, and his animals. The yield is the amount of food grown on a given amount of land, and it is often low. This is because subsistence farmers are generally less educated, and they have less money to buy equipment. Drought and other problems sometimes cause famines. Where yields are low, deforestation can provide new land to grow more food. This provides more nutrition for the farmer's family, but can be bad for the country and the surrounding environment over many years.
In some countries, farms are often fewer and larger. During the 20th century they have become more productive because farmers are able to grow better varieties of plants, use more fertilizer, use more water, and more easily control weeds and pests. Many farms also use machines, so fewer people can farm more land. There are fewer farmers in rich countries, but the farmers are able to grow more.
This kind of intensive agriculture comes with its own set of problems. Farmers use a lot of chemical fertilizers, pesticides (chemicals that kill bugs), and herbicides (chemicals that kill weeds). These chemicals can pollute the soil or the water. They can also create bugs and weeds that are more resistant to the chemicals, causing outbreaks of these pests. The soil can be damaged by erosion (blowing or washing away), salt buildup, or loss of structure. Irrigation (adding water from rivers) can pollute water and lower the water table. These problems have all got solutions, and modern young farmers usually have a good technical education.
Farmers select plants with better yield, taste, and nutritional value. They also choose plants that can survive plant disease and drought, and are easier to harvest. Centuries of artificial selection and breeding have changed crop plants. The crops produce better yield. Fertilizers, chemical pest control, and irrigation all help.
Some plants are improved with genetic engineering. One example is modifying the plant to resist herbicides.
It is important for there to be enough food for everyone. The food must also be safe and good. People say it is not always safe, because it contains some chemicals. Other people say intensive agriculture is damaging the environment. For this reason, there are several types of agriculture.
Agricultural policy focuses on the goals and methods of agricultural production. Common goals of policy include the quality, amount, and safety of food.
There are some serious problems that people face trying to grow food today.
These include:
The major crops produced in the world in 2002, are maize (corn), wheat, rice, and cotton.
Arithmetic
In mathematics, arithmetic is the basic study of numbers. The four basic arithmetic operations are addition, subtraction, multiplication, and division, although other operations such as exponentiation and extraction of roots are also studied in arithmetic.
Other arithmetic topics includes working with signed numbers, fractions, decimals and percentages.
Most people learn arithmetic in primary school, but some people do not learn arithmetic and others forget the arithmetic they learned. Many jobs require a knowledge of arithmetic, and many employers complain that it is hard to find people who know enough arithmetic. A few of the many jobs that require arithmetic include carpenters, plumbers, auto mechanics, accountants, architects, doctors, and nurses. Arithmetic is needed in all areas of mathematics, science, and engineering.
Some arithmetic can be carried out mentally. A calculator can also be used to perform arithmetic. Computers can do it more quickly, which is one reason Global Positioning System receivers have a small computer inside.
Addition
In mathematics, addition, represented by the symbol formula_1, is an operation which combines two mathematical objects together into another mathematical object of the same type, called the sum. Addition can occur with simple objects such as numbers, and more complex objects such as vectors and matrices.
In arithmetic, addition is finding the total of two or more numbers. The sign for addition is "+", and the name for the sign "+" is "plus". Another name for the total is the sum.
For example, there are objects in two groups. The objects are small circles: "o". One group has five of these objects. The other group has three of these objects. To find the total number of objects in both groups, the objects can be counted. Another way to find the number of objects in both groups is to add the numbers in each group.
Another method is to add the numbers of objects in group A and group B, since they are already counted. In symbols:
There are rules for adding numbers that people learn. There are also rules for adding numbers that are built into machines (binary adder). The rule says that:
In another counting example, Sally and Bill have 2 children. Sally and Bill get 3 more children. Sally and Bill have added three children to their two children, and now have five children.
Vertical Addition
The animation above demonstrates the addition of seven hundred and eighty six and four hundred and sixty seven, the problems digits have been separated into units, tens and hundreds (place value).
First, the units 6 and 7 are added together to make 13, so 1 ten and 3 units, with the 3 written below and the 1 ten carried to the tens column. Next, in the tens column, the 1, 8 and 6 are added together to make 15 tens, so 1 hundred and 5 tens, with the 5 written below and the 1 hundred carried to the hundreds column. Finally, in the hundreds column, 1, 7 and 4 are added together to make 12 hundreds, so 1 thousand and 2 hundreds, with the 2 written below and the 1 thousand carried to the thousand column. The final answer is thus one thousand two hundred and fifty three.
Tom wants to know the distance between his house and Sally's house. Bob's house is 300 meters east of Tom's house. Sally's house is 120 meters east of Bob's house:
The distance from Tom's house to Sally's house can be found by adding the distances already measured. The distance from Tom's house to Bob's house, added to the distance from Bob's house to Sally's house, is the same as the distance from Tom's house to Sally's house. That is, three hundred (300) meters plus 120 meters.
Hence Sally's house is 420 meters to the east of Tom's house.
Addition can also mean to make bigger.
Australia
Australia, formally the Commonwealth of Australia, is a country and sovereign state in the southern hemisphere, located in Oceania. Its capital city is Canberra, and its largest city is Sydney.