Studied by 31 people
age structure
Percentage of the population (or number of people of each sex) at each age level in a population.
crude birth rate
Annual number of live births per 1,000 people in the population of a geographic area at the midpoint of a given year.
crude death rate
Annual number of deaths per 1,000 people in the population of a geographic area at the midpoint of a given year.
cultural carrying capacity
The limit on population growth that would allow most people in an area or the world to live in reasonable comfort and freedom without impairing the ability of the planet to sustain future generations.
demographic transition
Hypothesis that countries, as they become industrialized, have declines in death rates followed by declines in birth rates.
emigration
Movement of people out of a specific geographic area.
family planning
Providing information, clinical services, and contraceptives to help people choose the number and spacing of children they want to have.
fertility rate
Number of children born to an average woman in a population during her lifetime.
Immigration
Migration of people into a country or area to take up permanent residence.
infant mortality rate
Number of babies out of every 1,000 born each year who die before their first birthday.
life expectancy
Average number of years a newborn infant can be expected to live.
migration
Movement of people into and out of specific geographic areas.
population change
Increase or decrease in the size of a population. It is equal to (Births + Immigration) – (Deaths + Emigration).
replacement– level fertility
Average number of children a couple must bear to replace themselves. The average for a country or the world usually is slightly higher than two children per couple (2.1 in the United States and 2.5 in some developing countries) mostly because some children die before reaching their reproductive years.
total fertility rate (TFR)
Estimate of the average number of children who will be born alive to a woman during her lifetime if she passes through all her childbearing years (ages 15–44) conforming to age–specific fertility rates of a given year. More simply, it is an estimate of the average number of children that women in a given population will have during their childbearing years.
agroforestry
Planting trees and crops together.
alley cropping
Planting of crops in strips with rows of trees or shrubs on each side.
animal manure
Dung and urine of animals used as a form of organic fertilizer.
aquaculture
Growing and harvesting of fish and shellfish for human use in freshwater ponds, irrigation ditches, and lakes, or in cages or fenced-in areas of coastal lagoons and estuaries or in the open ocean.
arable land
Land that can be cultivated to grow crops.
bioaccumulation
An increase in the concentration of a chemical in specific organs or tissues at a level higher than would normally be expected.
biological pest control
Control of pest population by natural predators, parasites, or disease-causing bacteria and viruses (pathogens).
biomagnification
Increase in concentration of DDT, PCBs, and other slowly degradable, fat-soluble chemicals in organisms at successively higher tropic levels of a food chain or web.
chronic malnutrition
Faulty nutrition, caused by a diet that does not supply an individual with enough protein, essential fats, vitamins, minerals, and other nutrients needed for good health.
chronic undernutrition
Condition suffered by people who cannot grow or buy enough food to meet their basic energy needs. Most chronically undernourished children live in developing countries and are likely to suffer from mental retardation and stunted growth and to die from infectious diseases.
commercial inorganic fertilizer
Commercially prepared mixture of inorganic plant nutrients such as nitrates, phosphates, and potassium applied to the soil to restore fertility and increase crop yields.
compost
Partially decomposed organic plant and animal matter used as a soil conditioner or fertilizer.
conservation-tillage farming
Crop cultivation in which the soil is disturbed little (minimum-tillage farming) or not at all (no-till farming) in an effort to reduce soil erosion, lower labor costs, and save energy.
contour farming
Plowing and planting across the changing slope of land, rather than in straight lines, to help retain water and reduce soil erosion.
conventional-tillage farming
Crop cultivation method in which a planting surface is made by plowing land, breaking up the exposed soil, and then smoothing the surface.
DDT
Dichlorodiphenyltrichloroethane, a chlorinated hydrocarbon that has been widely used as an insecticide but is now banned in some countries.
desertification
Conversion of rangeland, rain–fed cropland, or irrigated cropland to desertlike land, with a drop in agricultural productivity of 10% or more. It usually is caused by a combination of overgrazing, soil erosion, prolonged drought, and climate change.
domesticated species
Wild species tamed or genetically altered by crossbreeding for use by humans for food (cattle, sheep, and food crops), as pets (dogs and cats), or for enjoyment (animals in zoos and plants in botanical gardens).
famine
Widespread malnutrition and starvation in a particular area because of a shortage of food, usually caused by drought, war, flood, earthquake, or other catastrophic events that disrupt food production and distribution.
feedlot
Confined outdoor or indoor space used to raise hundred to thousands of domesticated livestock.
fertilizer
Substance that adds inorganic or organic plant nutrients to soil and improves its ability to grow crops, trees, or other vegetation
fishery
Concentration of particular aquatic species suitable for commercial harvesting in a given ocean area or inland body of water.
food insecurity
Condition under which people live with chronic hunger and malnutrition that threatens their ability to lead healthy and productive lives
food security
Condition under which every person in a given area has daily access to enough nutritious food to have an active and healthy life.
fungicide
Chemical that kills fungi.
genetically modified organism (GMO)
Organism whose genetic makeup has been altered by genetic engineering.
green manure
Freshly cut or still–growing green vegetation that is plowed into the soil to increase the organic matter and humus available to support crop growth.
green revolution
Popular term for the introduction of scientifically bred or selected varieties of grain (rice, wheat, maize) that, with adequate inputs of fertilizer and water, can greatly increase crop yields.
herbicide
Chemical that kills a plant or inhibits its growth.
humus
Slightly soluble residue of undigested or partially decomposed organic material in topsoil. This material helps retain water and water–soluble nutrients, which can be taken up by plant roots.
hydroponics
Form of agriculture in which farmers grow plants by exposing their roots to a nutrient–rich water solution instead of soil.
industrialized agriculture
Production of large quantities of crops and livestock for domestic and foreign sale; involves use of large inputs of energy from fossil fuels (especially oil and natural gas), water, fertilizer, and pesticides.
insecticide
Chemical that kills insects.
integrated pest management (IPM)
Combined use of biological, chemical, and cultivation methods in proper sequence and timing to keep the size of a pest population below the level that causes economically unacceptable loss of a crop or livestock animal.
intercropping
Growing two or more different crops at the same time on a plot. For example, a carbohydrate–rich grain that depletes soil nitrogen and a protein–rich legume that adds nitrogen to the soil may be intercropped.
leaching
Process in which various chemicals in upper layers of soil are dissolved and carried to lower layers and, in some cases, to groundwater.
metabolism
Ability of a living cell or organism to capture and transform matter and energy from its environment to supply its needs for survival, growth, and reproduction.
monoculture
Cultivation of a single crop, usually on a large area of land.
organic agriculture
Growing crops with limited to no use of synthetic pesticides and synthetic fertilizers; genetically modified crops, raising livestock without use of synthetic growth regulators and feed additives; and using organic fertilizer (manure, legumes, compost) and natural pest controls (bugs that eat harmful bugs, plants that repel bugs and environmental controls such as crop rotation).
organic fertilizer
Organic material such as animal manure, green manure, and compost applied to cropland as a source of plant nutrients.
overnutrition
Diet so high in calories, saturated (animal) fats, salt, sugar, and processed foods, and so low in vegetables and fruits that the consumer runs a high risk of developing diabetes, hypertension, heart disease, and other health hazards.
percolation
Passage of a liquid through the spaces of a porous material such as soil.
pest
Unwanted organism that directly or indirectly interfere with human activities.
pesticide
Any chemical designed to kill or inhibit the growth of an organism that people consider undesirable.
plantation agriculture
Growing specialized crops such as bananas, coffee, and cacao in tropical developing countries, primarily for sale to developed countries.
polychlorinated biphenyls (PCBs)
Group of 209 toxic, oily, synthetic chlorinated hydrocarbon compounds that can be biologically amplified in food chains and webs.
polyculture
Complex form of intercropping in which a large number of different plants maturing at different times are planted together.
salinization
Accumulation of salts in soil that can eventually make the soil unable to support plant growth.
slash-and-burn agriculture
Cutting down trees and other vegetation in a patch of forest, leaving the cut vegetation on the ground to dry, and then burning it. The ashes that are left add nutrients to the nutrient–poor soils found in most tropical forest areas. Crops are planted between tree stumps. Plots must be abandoned after a few years (typically 2–5 years) because of loss of soil fertility or invasion of vegetation from the surrounding forest.
soil
Complex mixture of inorganic materials (clay, silt, pebbles, and sand), decaying organic matter, water, air, and living organisms.
soil conservation
Methods used to reduce soil erosion, prevent depletion of soil nutrients, and restore nutrients previously lost by erosion, leaching, and excessive crop harvesting.
soil erosion
Movement of soil components, especially topsoil, from one place to another, usually by wind, flowing water, or both. This natural process can be greatly accelerated by human activities that remove vegetation from soil.
soil horizons
Horizontal zones, or layers, that make up a particular mature soil, Each horizon has a distinct texture and composition that vary with different types of soils.
soil profile
Cross-sectional view of the horizons in a soil.
strip-cropping
Planting regular crops and close-growing plants, such as hay or nitrogen-fixing legumes, in alternating rows or bands to help reduce depletion of soil nutrients.
sustainable agriculture
Method of growing crops and raising livestock based on organic fertilizers, soil conservation, water conservation, biological pest control, and minimal use of nonrenewable fossil–fuel energy.
terracing
Planting crops on a long, steep slope that has been converted into a series of broad, nearly level terraces with short vertical drops from one to another that run along the contour of the land to retain water and reduce soil erosion.
traditional intensive agriculture
Production of enough food for a farm family’s survival and a surplus that can be sold. This type of agriculture uses higher inputs of labor, fertilizer, and water than traditional subsistence agriculture.
traditional subsistence agriculture
Production of enough crops or livestock for a farm family’s survival.
waterlogging
Saturation of soil with irrigation water or excessive precipitation so that the water table rises close to the surface.
windbreak
Row of trees or hedges to partially block wind flow and reduce soil erosion on cultivated land.
aquifer
Porous, water–saturated layers of sand, gravel, or bedrock that can yield an economically significant amount of water.
dam
A structure built across a river to control the river’s flow or to create a reservoir.
desalination
purification of salt water or brackish (slightly salty) water by removal of dissolved salts.
drought
Condition in which an area does not get enough water because of lower-than-normal precipitation or higher-than-normal temperatures that increase evaporation.
floodplain
Flat valley floor next to a stream channel. For legal purposes, the term often applies to any low area that has the potential for flooding, including certain coastal areas.
groundwater
Water that sinks into the soil and is stored in slowly flowing and slowly renewed underground reservoirs called aquifers; underground water in the zone of saturation, below the water table.
natural recharge
Natural replenishment of an aquifer by precipitation, which percolates downward through soil and rock.
reliable runoff
Surface runoff of water that generally can be counted on as a stable source of water from year to year.
reservoir
Artificial lake created when a stream is dammed.
subsidence
Slow or rapid sinking of part of the earth’s crust that is not slope–related.
surface runoff
Water flowing off the land into bodies of surface water.
surface water
Precipitation that does not infiltrate the ground or return to the atmosphere by evaporation or transpiration.
virtual water
Water that is not directly consumed but is used to produce food and other products.
water footprint
A rough measure of the volume of water that we use directly and indirectly to keep a person or group alive and to support their lifestyles.
water table
Upper surface of the zone of saturation, in which all available pores in the soil and rock in the earth’s crust are filled with water.
watershed
Land area that delivers water, sediment, and dissolved substances via small streams to a major stream (river).
zone of aeration
Zone in soil that is not saturated with water and that lies above the water table.
zone of saturation
Zone where all available pores in soil and rock in the earth’s crust are filled by water,
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