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A plant, Musa textilis, of the banana family that is valuable for its hard fiber (also known as Manila hemp) and native to Borneo and the Philippines. Abaca is one of the strongest of the hard fibers. Commercially, it is known as Manila hemp. The…

An autonomous undersea vehicle that can be launched from submarines, surface ships, or aircraft to attack enemy submarines and surface ships. An acoustic torpedo is a sophisticated weapon. Its main components are a guidance and control system, a…

Aircraft specifically designed or adapted from a general utility airframe for use in agriculture and forestry and for control of insect vectors of human, animal, and plant diseases. Agricultural aircraft (Fig. 1) have become an indispensable tool…

A discipline concerned with solving the engineering problems of providing food and fiber for the people of the world. These problems include designing agricultural machinery to work the soil and harvest the crops, as well as developing water…

The science that deals with the selection, breeding, nutrition, and management of domestic animals for economical production of meat, milk, eggs, wool, hides, and other animal products. The broad field of agricultural science focuses on two realms:…

The techniques and methods used in plowing, harrowing, planting, tilling, harvesting, drying, storing, and processing of agricultural crops. Agricultural soil and crop practices seek to keep the quality and fertility of soils at high levels so as to…

A model for the functioning of an agricultural system, with all inputs and outputs. An ecosystem may be as small as a set of microbial interactions that take place on the surface of roots, or as large as the globe. An agroecosystem may be at the…

The science and study of crops and soils. Agronomy is the umbrella term for a number of technical research and teaching activities (see illustration): crop physiology and management, soil science, plant breeding, and weed management frequently are…

Any of the deciduous shrubs and trees of the genus Alnus in the birch family (Betulaceae). There are approximately 30 species of alder, with 10 in the United States. Alders are widespread in cool north temperate regions and are also found southward…

The world's most valuable forage legume, Medicago sativa, also known as lucerne, and less often as purple medic, medica, snail clover, median herb, Burgundy hay or clover, and Chilean clover. Alfalfa is often referred to as the queen of forages. It…

The dried, unripe fruits (berries) of a small, tropical, evergreen tree, Pimenta dioica (P. officinalis), of the myrtle family (Myrtaceae). Allspice (see illustration), which is also known as Jamaica pepper, is a native of the West Indies and parts…

A book that contains astronomical or meteorological data arranged according to days, weeks, and months of a given year and may also include diverse information of a nonastronomical character. This article is restricted to astronomical and…

Prunus dulcis (also known as Prunus amygdalus or Amygdalus communis), a small deciduous tree of the order Rosales that is closely related to the peach and other stone fruit trees, and grown widely for its ellipsoidal edible seeds. The fruit of the…

Vicugna pacos, a member of the camel family (Camelidae), which has been domesticated for more than 2000 years and is economically important for its long, fine wool. The alpaca (Vicugna pacos; formerly, Lama pacos) [see illustration] belongs to the…

Any device which measures the height of an aircraft. The two chief types are the pressure altimeter, which measures the aircraft's distance above sea level, and the radar altimeter, which measures distance above the ground. Pressure Altimeter A…

An annual plant (seldom perennial) of the genus Amaranthus (family Amaranthaceae) that is distributed worldwide in warm and humid regions. Amaranth plants are botanically distinguished by their small chaffy flowers (see illustration), which are…

Determination of the relative or absolute age of materials or objects by measurement of the degree of racemization of the amino acids present. With the exception of glycine, the amino acids found in proteins can exist in two isomeric forms called d-…

The application of genetic principles for improving heredity for economically important traits in domestic animals. The science of animal breeding is based on fundamental genetic concepts. Through controlled mating and selection, which can involve…

An annual herb, Pimpinella anisum (family Apiaceae), whose fruit is used to provide food flavoring and to make a distilled oil. Anise is one of the earliest aromatics mentioned in literature. The anise plant (see illustration) is an annual herb that…

The observation, measurement, and explanation of human variability in time and space. Anthropology is a science concerned with the interrelations of the biological, cultural, geographical, and historical aspects of humankind, including modern human…

The systematic quantitative representation of the human body. Anthropometric techniques are used to measure the absolute and relative variability in size and shape of the human body. Instrumentation Depending on the objective, anthropometric…

A deciduous tree, Prunus armeniaca, in the order Rosales that produces a simple fleshy stone fruit. The apricot is thought to be native to China; then it was distributed throughout Asia and Europe, and eventually North America, South America, and…

The cultivation of freshwater and marine species for human purposes. Aquaculture, or aquatic farming, is concerned with the raising of animals and the harvesting of plants in freshwater and marine environments (Fig. 1). In other words, it is the…

The establishment of the temporal sequence of prehistoric events. An event can be defined as a duration of time during which certain features came together to form a set, for example, when certain materials were formed into an object (manufacturing…

Any member of an adaptively diverse group of extinct hominin species that inhabited Africa between approximately 4.2 million years ago (MYA) and 1.2 MYA. The term australopith is used in preference to the term australopithecine, which is sometimes…

The branch of applied physics which deals with the motion of projectiles and the conditions governing their motion. Ballistics is, for practical purposes, subdivided into exterior and interior ballistics. Exterior ballistics begins at the instant a…

A fast-growing tree, Ochroma pyramidale (also known as O. lagopus), which is widely distributed in tropical America, especially in Ecuador. Balsa (Ochroma pyramidale; also, O. lagopus) belongs to the mallow family, Malvaceae, in the order Malvales.…

Raising of cattle for meat. Beef cattle production is a section of animal agriculture concerned with the rearing of cattle in order to produce meat for human or other animal consumption (Fig. 1). This is in contrast to dairy cattle production, which…

The management and maintenance of colonies of honeybees for human purposes. Beekeeping is an ancient art. Although the commonly known honeybee species (Fig. 1) is native to Europe and Africa, humans have transported them to other continents. The…

The study of skeletal remains from archeological sites by biological (or physical) anthropologists. Bioarcheology differs in several ways from traditional skeletal research. Previous work focused on individual case studies (for example, individuals…

Biological agents that weaken or kill fungi so as to prevent plant disease development. Such agents may be used independently or formulated with other materials as biopesticides. They can be classified as microbial or biochemical, based on the…

The use of parasitoids, predators, and pathogens to reduce injurious pest insect populations and consequently the damage they cause. Viruses and bacteria are the most commonly used pathogens, but fungi, protozoa, and nematodes may also be important…

Organic materials or wastes produced by plants and animals that can be used as energy sources or fuels. Biomass is a collective term used to describe renewable materials that are derived from plants and animals. In some cases, microbial metabolic…

A deciduous tree of the genus Betula, which is distributed over much of North America, in Asia (south to the Himalayas), and in Europe. Birch trees are assigned to the genus Betula. They belong to the family Betulaceae (which also contains alders,…

An anchored or moored floating object, other than a lightship, intended as an aid to navigation. Buoys are the most numerous of all engineered aids to navigation, with some 20,000 in United States waters alone.A great variety of buoys are in use.…

A fine, natural animal fiber obtained from the Bactrian camel and known to consumers chiefly in the form of high-quality coat fabrics. Camel's hair (also spelled camel hair) is a textile fiber obtained from the two-humped Bactrian camel (see…

The tree Cinnamomum camphora, a member of the laurel family, from which camphor is extracted. The camphor tree (see illustration) belongs to the Lauraceae (laurel) family of plants in the order Laurales. It is a native species of China, Japan, and…

The product exuded from the leaves of the wax palm, Copernicia prunifera (alternatively C. cerifera), in the family Arecaceae (Palmae). The carnauba wax palm (see illustration) is a native tree of Brazil and other regions in tropical South America.…

The natural fiber obtained from the cashmere goat, native to the Himalayan regions of China and India. The fleece of the cashmere goat (see illustration) has long, straight, coarse outer hair of little value. However, the small quantity of…

Biodiverse ecosystem characterized by frequent to persistent clouds at the vegetation level. Relative to lowland tropical rainforests, cloud forests are shorter in stature and exhibit a denser understory (see illustration). Located in tropical and…

A tropical evergreen shrub or small tree of the genus Coffea (family Rubiaceae), a native of northeast Africa and adjacent southwest Asia, cultivated for the seeds (coffee beans) of its fruit. Members of the genus Coffea (Fig. 1) grow mainly between…

Zea mays, also known as maize, a grain crop grown for its edible seeds (kernels). Corn (Zea mays) [Fig. 1] is an important cereal grass plant belonging to the order Poales (formerly Cyperales). The top corn-producing countries are the United…

A warm-season annual cucurbit (Cucumis sativus), originally native to India, which is grown for its edible, immature, fleshy fruit. The cucumber is originally native to India and is grown for its edible, immature, fleshy fruit (Fig. 1). The cucumber…

A section of animal agriculture concerned with the production of milk and milk products. Over the course of thousands of years, humans have selected some mammals, especially the cow, goat, and water buffalo, for their ability to produce quantities…

The deliberate conversion of forest to nonforest land that results in the long-term reduction of tree canopy below a minimum level. Deforestation, also known as land clearing, permanently eliminates forests to utilize the land for other purposes…

The adaptation of an animal or plant through breeding in captivity to a life intimately associated with and advantageous to humans. Domesticated plants and animals differ genetically and morphologically from their wild counterparts, often in ways…

A burst of electromagnetic energy. In a military context—and the subject of this article—an electromagnetic pulse (EMP) is a transient electromagnetic signal produced by a nuclear explosion in or above Earth's atmosphere (Fig. 1). Though not…

The branch of ecology that studies the environmental changes that occur in ecosystems in relation to fire. Disturbance is a major environmental influence in many of Earth's ecosystems. Vital to the healthy functioning of forests, savannas,…

The application of physical anthropology theory and techniques to medicolegal questions. Forensic anthropology may also pertain to subdisciplines of anthropology, such as cultural anthropology, biological/physical anthropology, archaeology, and…

A plant community consisting predominantly of trees and other woody vegetation growing closely together. Forests are complex ecosystems comprising plants, animals, and their environment, with trees as the dominant form of vegetation (Fig. 1). Trees…

Uncontrolled combustion of forest fuels or vegetation. Forest fire, bushfire, wildland fire, and wildfire are terms that are used interchangeably and refer to all unplanned fires that burn surface fuels or vegetation (such as grasses, weeds, brush,…

Ancient fossilized members of human beings and those species directly ancestral to modern humans. Fossil humans comprise all prehistoric skeletal remains of humans that are archeologically earlier than the Neolithic (necessarily an imprecise limit,…

The application of biotechnological techniques utilizing fungi for agricultural purposes. Fungal biotechnology is applied in agriculture to promote plant vigor, to increase yields, and to reduce impacts of plant diseases, weeds, or invertebrate…

The expression of a heritable trait in both the homozygous and heterozygous conditions. Genetic dominance (Fig. 1) is a cornerstone of the basic laws of biological inheritance (also known as Mendelian inheritance or Mendelism). In particular,…

Plants that have altered genetic material (DNA) through recombinant DNA (rDNA) manipulation. Genetic engineering of plants allows for very specific genetic changes to be made to a plant's deoxyribonucleic acid (DNA), as opposed to the random…

Commercially grown plants that have altered genetic material through artificial recombinant manipulation. Genetic modification is the latest scientific tool for developing improved crop varieties. Such genetically modified (GM) crops can help to…

A glass- or plastic-enclosed structure that is used to grow plants under protected conditions. Greenhouses (also known as glasshouses) are transparent, enclosed, climate-controlled structures (Fig. 1) in which young, tender, or out-of-season plants…

The deoxyribonucleic acid of Homo neanderthalensis. Neandertals (also spelled Neanderthals) are the closest evolutionary relatives of modern humans. Based on fossil and archeological records, Neandertals are large-brained people with a distinct…

An explosion whose energy is produced by a nuclear transformation, either fission or fusion. Nuclear explosions can be either natural or artificial, for example in the form of a star undergoing a supernova or the deliberate detonation of an…

A system of food and fiber production that relies on the strategic management of the agroecosystem to foster plant and animal health and productivity, as opposed to reliance on external, synthetic agricultural inputs. As an ecological management…

A biennial herb, Petroselinum crispum, of European origin belonging to the plant order Apiales (Umbellales). Parsley (see illustration) is grown for its edible foliage and is used to garnish and flavor foods. It contains large quantities of vitamins…

A hardy biennial, Pastinaca sativa, of Mediterranean origin belonging to the plant order Apiales (Umbellales). The parsnip (see illustration) is grown for its edible thickened taproot and is used primarily as a cooked vegetable. Propagation is by…

An annual leafy leguminous vine, Pisum sativum (order Fabales), cultivated for its smooth or wrinkled, round edible seeds, which are borne in dehiscent pods. The garden pea is one of the world's oldest cultivated crops. It is a native of western…

A deciduous fruit tree species, Prunus persica, of the order Rosales that originated and was first cultivated in western China. The peach (see illustration) is adapted to relatively moderate climates in the temperate zone. Although most peach…

A low-branching, self-pollinated, one- to six-seeded annual legume (Arachis hypogaea) cultivated for its edible seed, which forms beneath the soil in a pod. Peanuts are cultivated throughout the tropical and temperate climates of the world. Peanut…

Any of approximately 20 species of deciduous trees, and their fruits, in the genus Pyrus (order Rosales). About half of the species of pear are native to Europe, North Africa, and the Middle East, especially areas around the Mediterranean Sea; the…

A large deciduous hickory tree [Carya illinoensis (alternatively C. illinoiensis or C. illinoinensis)], and the edible, oblong, thin-shelled nut from this tree. The pecan tree belongs to the family Juglandaceae (order Fagales; alternatively…

Defined narrowly, a science that is concerned with the nature and arrangement of horizons in soil profiles; the physical constitution and chemical composition of soils; the occurrence of soils in relation to one another and to other elements of the…

Any of several warm-season species of the plant genus Capsicum (family Solanaceae, order Solanales), especially Capsicum annuum, which is cultivated for its fruit. The garden pepper, Capsicum annuum, is a warm-season crop originally domesticated in…

The mint species Mentha piperita in the family Lamiaceae (Labiatae). Peppermint (see illustration) is a sterile interspecific hybrid that is believed to have occurred in nature from the hybridization of fertile Mentha aquatica with fertile Mentha…

An optical instrument that permits viewing along a displaced or deflected axis, providing an observer with the view from a position which may be inaccessible or dangerous. Periscopes range in complexity from the simple unit-power tank periscope to…

Perennially frozen ground. Two classes of frozen ground are generally distinguished: seasonally frozen ground, which freezes and thaws on an annual basis; and permafrost, which is formed when subsurface earth materials remain below 0°C (32°F) for…

The biological, physical, and chemical processes involved in the cycling of phosphorus in the environment. The cycle comprises a geological (long-term) cycle and a biological (short-term) cycle, the latter with both terrestrial and aquatic…

The subfield of anthropology that deals with human and nonhuman primate evolution, the biological bases of human behavior, and human biological variability and its significance. Physical anthropology is a branch of anthropology that investigates the…

The application of genetic principles to the improvement of cultivated plants. The science of plant breeding involves the controlled mating and selection of plants, often utilizing hybridization and genetic engineering techniques, to modify plant…

The science of breeding, raising, and marketing of domesticated fowl grown for their meat and eggs. Poultry production is one of the most important agricultural enterprises involving animals. The predominant types of poultry are domestic chickens…

A type of dense forest that occurs in continually wet climates with no dry season. Rainforests comprise some of the most important and oldest ecosystems on Earth. Characterized by high amounts of rainfall, rainforests contain a rich diversity of…

Finely divided rock-derived material containing an admixture of organic matter and capable of supporting vegetation. Soils are independent natural bodies, each with a unique morphology resulting from a particular combination of climate, living…

The study of the composition and chemical properties of soil. Soil chemistry involves the detailed investigation of the nature of the solid matter from which soil is constituted and of the chemical processes that occur as a result of the action of…

The study of the interactions among soil organisms, and between biotic and abiotic aspects of the soil environment. Soil (Fig. 1) is made up of a multitude of physical, chemical, and biological entities, with many interactions occurring among them.…

The ability of soil to supply plant nutrients. Soil contains an admixture of organic matter that is capable of supporting vegetation (Fig. 1). Thus, soil fertility is of paramount importance to ensure proper plant nutrition and maximal plant growth.…

A ship that can operate completely submerged in the water. The term "submarine" formerly applied to any ship capable of operating completely underwater, but now usually describes a ship built for military purposes (Fig. 1). The expected military…

Saccharum officinarum, a stout, perennial member of the grass family characterized by two-ranked leaves and a many-jointed stalk; the source approximately 70% of the world's annual sugar production. Sugarcane (also spelled sugar cane) [Fig. 1]…

A biological community (ecosystem) of plants and animals dominated by trees and other woody plants located between the Tropic of Cancer and the Tropic of Capricorn, and extending beyond this region where climate conditions are suitable. Forests are…

The plant Brassica rapa (alternatively B. campestris var. rapa), a cool-season, hardy crucifer of Asiatic origin belonging to the order Capparales (Brassicales) and grown for its enlarged root and its foliage. The turnip plant (see illustration) is…

A food grain crop of the genus Triticum, in which the inflorescence is a spike bearing sessile spikelets arranged alternately on a zigzag rachis (main axis). Wheat (genus Triticum) [Fig. 1] is the most widely grown food crop in the world and ranks…

The science of chemical compositions and changes involved in the production, protection, and use of crops and livestock. As a basic science, agricultural chemistry (see illustration) embraces, in addition to test-tube chemistry, all the life…

Mechanized systems of food and fiber production used in agriculture. The mechanized systems comprising agricultural machinery are utilized in numerous aspects of agriculture, including the initial tillage of the soil (Fig. 1), planting, cultural…

A deciduous tree (genus Malus) in the order Rosales, which produces an edible, simple, fleshy, pome-type fruit. Apples (Fig. 1) belong to the family Rosaceae, which includes many other deciduous fruits, including pears, peaches, and cherries. There…

The scientific study of past material culture. The initial objective of archeology (often spelled archaeology) is to construct cultural chronologies that order past material culture into meaningful temporal segments. The intermediate objective is to…

A device for suddenly producing an explosive neutron chain reaction in a fissile material such as uranium-235 (235U) or plutonium-239 (239Pu). An atomic bomb derives its destructive potency from the rapid release of nuclear energy brought about by…

Addition of elements or other materials to the soil to increase or maintain plant yields. For plants to develop, all the elements essential for growth must be supplied by way of the root system or, to a limited extent, through the leaves. The total…

The diversity of biological and genetic differences observed in the human population. Anthropologists study human biology to better understand the extent of human biological variability, to explain the mechanisms that create and pattern this…

A device in which an uncontrolled, self-sustaining, thermonuclear fusion reaction is carried out in heavy hydrogen (deuterium or tritium) to produce an explosion. Initial conceptualization of the hydrogen bomb occurred alongside development of the…

The collective techniques for supplying nutrients and water directly to the roots of plants, without soil or other media. Hydroponics is concerned with the cultivation and growing of plants without soil or other media. Hydroponic systems (Fig. 1)…

Pathological conditions caused by pathogenic microorganisms in animals that are consumed as food. The introduction of an infectious disease into an animal population intended for food consumption by humans can have many negative outcomes, including…

The name (Spanish in origin) for the dried leaves, stems, seeds, and flowering tops of the hemp plant, Cannabis sativa, which can be smoked in cigarette form or in a pipe. Marijuana is the Spanish-derived name for the dried leaves, stems, seeds, and…

Fundamental principles governing the transmission of genetic traits, as discovered by Gregor Mendel. Mendelism is the term used to describe the basic laws of genetic inheritance (Fig. 1). These operating laws were formulated by Gregor Johann Mendel…

The study of biota that inhabit the soil and the processes that they mediate. Soil is a complex environment (Fig. 1) colonized by an immense diversity of microorganisms. As such, soil microbiology is concerned with the investigation of the…

The structure and composition of the hard fibrous substance that makes up the trunks and large branches of trees beneath the bark. Wood (Fig. 1) is composed mostly of hollow, elongated, spindle-shaped cells that are arranged parallel to each other…