Agriculture- The study and practice of cultivating land for the growing of crops and the rearing of livestock. The increasing demands for food production since the mid 20-th century have seen many developments in agricultural technology and practices that have greatly (greatly) increased crop and livestock production. However, these advances in modern intensive farming techniques have had their impact on the environment, particularly with increased use of fertilizers and pesticides. the now widespread practice of crop monoculture (in which one crop is crown densely over an extensive area) has required an increase in the use of pesticides as monoculture provides an ideal opportunity for crop pests. Monoculture also requires vast areas of land, which has meant that natural habitats have been destroyed. Deforestation has resulted from the clearing of forests for crop production and cattle rearing. Advances in technology have including ploughing machines with hydraulic devices that can control the depth to which the soil is ploughed, and seed drills that automatically implants seeds in the soil so that ploughing is not necessary. Food supply in many less-developed countries relies on subsistence farming, in which the crops and livestock produced are used soley to feed the farmer and his family. in such countries a system known as slash and burn is common, in which the vegetation in an area is cut down and then burnt, thus returning the minerals to the soil. The area can then be used for crop cultivation until the soil fertility drops, at which point it then abandoned for a number of years and another site is cultivated. The selective breeding of crop plants and farm animals has had an enormous impact on productivity in agriculture. Modern varieties of crop plants have increased nutritional value and greater resistance to disease, while animals have been selectively bred to enhance their yields of milk, meat, and other products. Developments in genetic engineering have enabled the introduction to commercial cultivation of genetically modified crop plants, such as tomatoes and soya, which contain genes from other organisms to enhance crop growth, nutritional properties, or storage characteristics. Genetic modification can also confer resistance to herbicides, thereby allowing more effective weed control, as well as improved resistance to insects and other pests and to diseases. The application of similar technology to animal production is being researched.
Biome: A major ecological community or complex of communities that extends over a large geographical area characterized by a dominant type of vegetation. The organisms of a biome are adapted to the climate conditions associated with the region. There are no distinct boundaries between adjacent biomes, which merge gradually with each other. Examples of biomes are tundra, tropical rainforest, taiga, chaparral, grassland, and desert.
