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Wildfires, also termed bushfires or forest fires, are currently devastating large swaths of land in Australia. Detrimental ecologic consequences of these uncontrolled combustions of forest fuels and vegetation are numerous. One of the most serious…

The American beech (Fagus grandifolia) is native to forest regions east of the Mississippi River and is a key tree species in the United States. In particular, it is very abundant from Ohio to the New England states. The tree is also found in the…

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…

An organism that has had its genetic material manipulated or altered in a laboratory setting through the use of genetic or genomic engineering techniques. Genetically modified organisms (GMOs) are microorganisms, plants, or animals that have been…

The mental ability to store and access information that has been acquired through experience. Memory (Fig. 1) is a critical component of practically all aspects of human thinking, including perception, learning, language, and problem solving.…

The science that applies laws and principles of physics, especially continuum and particulate mechanics and hydraulics of porous media, to solve problems encountered in civil engineering that are related to force-deformation behavior of soil and the…

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…

The Joshua tree (Yucca brevifolia) is a remarkable evergreen, treelike plant found only in the southwestern United States. It was named by Mormon settlers in the early 1800s. Upon seeing the limbs of this plant branching upwards to heaven, the…

Habituation to a specific practice, such as drinking alcoholic beverages or using drugs (for example, heroin, cocaine, or amphetamines), and disorders characterized by the chronic use of a drug, alcohol, or similar substance. Addiction and addictive…

Behavior that is intended to threaten or inflict physical injury or emotional harm on another person or organism. Aggression is a type of behavior (physical or verbal, or both) displayed by an individual who aims or is motivated to harm another…

Any disorder of recognition. Agnosias were named originally by Sigmund Freud in 1891 to denote disturbances in the ability to recognize and name objects. Usually the misrecognition involves one sensory modality, with primary sensation in that…

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…

All buildings used on the farm for housing livestock and the farm family and for storing grain, livestock feed, and farm machinery. In the United States, today's farms are larger, more specialized, and more mechanized than those of the past, and…

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…

The repeated and/or excessive use of alcohol (ethanol) that continues despite negative physical, psychiatric, or social consequences. Alcoholism is characterized by consuming alcohol more often, in larger amounts, or over longer periods than…

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…

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…

A disease of the nervous system characterized by a progressive dementia that leads to profound impairment in cognition and behavior. Dementia occurs in a number of brain diseases where the impairment in cognitive abilities represents a decline from…

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…

A significant but relatively selective inability to remember. Amnesia can be characterized along two dimensions with respect to its onset: an inability to remember events that occurred after the onset of amnesia is referred to as anterograde…

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…

The use of live nonhuman animals for scientific research and experimentation. Animal testing has been a cornerstone of biomedical research, having contributed greatly to the understanding of human biology, to the unraveling of the complex underlying…

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…

A disorder of language, acquired as a result of brain disease. Aphasia strikes at that most human of attributes—communication with other people. Aphasia must be distinguished from three other conditions: motor speech disorders, developmental…

An impairment in the performance of voluntary actions despite intact motor power and coordination, sensation and perception, and comprehension. The apraxic person knows the act to be carried out, and has the requisite sensory-motor capacities; yet…

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…

A common psychiatric disorder (especially in children) characterized by attentional difficulties, impulsivity, and hyperactivity. Attention deficit hyperactivity disorder (ADHD) is a mental disorder marked by an individual's inability to pay…

The quantitative assessment of individual hearing, both normal and defective. In typical tests, pure tones are presented through headphones, though some tests use speech instead of tones. In bone conduction tests, tones are presented through a…

A neurodevelopmental condition that impairs the way that a person relates to and communicates with other people. Persons with autism have difficulties with social communication and interaction. They also can have unusual behaviors, such as…

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 branch of ecology that focuses on the evolutionary causes of variation in behavior among populations and species. The scientific study of behavioral ecology investigates how changes of behavior are influenced by ecological factors (Fig. 1).…

A discipline concerned with the application of ethics to biological problems, especially in the field of medicine. Bioethics is a broad term that encompasses the environmental, ethical, legal, and social implications of agriculture, life sciences,…

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 major mental disorder in which there are lifelong episodes of both mania and depression; also known as manic-depressive illness. Bipolar disorder, also termed manic-depressive illness or manic depression, is characterized by sudden and often…

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,…

Unwanted, aggressive behavior that involves a real or perceived power inequity. The behavior of bullying is often chronic and includes actions such as threats, spreading rumors, attacking someone physically or verbally, and purposefully excluding or…

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…

The internal structures and processes that are involved in the acquisition and use of knowledge, including sensation, perception, attention, learning, memory, language, thinking, and reasoning. The mental processes and behaviors that constitute…

Technology used to augment human mental capacity. In contrast, technology is widely used to augment human physical capabilities. We can move faster using cars, we can lift heavier weights using cranes, and we can even fly through the air using…

The ability to discriminate light on the basis of wavelength composition. Color vision is found in humans, in other primates, and in certain species of birds, fishes, reptiles, crustaceans, and insects. These animals have visual receptors that…

A learned response performed by a human or other animal to a signal that was previously associated with an event of consequence for that human or animal. A conditioned reflex, also known as a conditioned response, is an acquired response in which…

The state of being aware of one's own existence, of one's mental states, and of the impressions made upon one's senses. Consciousness is central to human existence, yet it has proved difficult to define and characterize. Typically, consciousness…

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…

A syndrome characterized by a generalized decline in cognition that is severe enough to cause functional impairment in daily activities. Dementia is a term used to describe a collection of symptoms of severe cognitive decline. Individuals suffering…

A heterogeneous affective disorder involving a depressed mood and/or a loss of interest in daily activities. The most common form of affective disorder is depression (also termed clinical depression) [Fig. 1]. A major depressive episode is defined…

The study of age-related changes in behavior from birth to death. Developmental psychology is an important branch of psychological analysis that investigates the development and changes of behavior over an individual's lifetime (Fig. 1). In general,…

Disorders characterized by abnormal eating behaviors, extreme weight-control behaviors, and dysfunctional beliefs about eating, weight, and body shape. Individuals suffering from eating disorders display abnormal eating behaviors and extreme…

A term commonly associated with both behaviors and states of mind (known as feelings) that are not under the control of reason and disturb the flow of consciously directed behavior. Emotions influence human thinking and behavior (Fig. 1), and they…

An active and intentional act or practice of putting to death, in a relatively painless way, of persons suffering severely from medical conditions that are incurable, untreatable, or irreversible. Euthanasia is an act by a person, usually a…

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,…

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,…

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,…

Photosynthesis is a key natural process utilized by plants and is necessary for proper plant growth. Specifically, photosynthesis uses light to manufacture chemical compounds, including organic compounds—primarily carbohydrates—that are derived from…

The common name for about six species of thorny, spreading bushes of the genus Ribes, producing small, acidic, edible fruits. Gooseberries and currants all belong to the genus Ribes (order Saxifragales or Rosales, depending on the classification…

All freshwater comes from precipitation over land, which is distributed on Earth as blue and green water. Blue water—that is, surface and groundwater—is stored as freshwater in lakes, streams, ice, and snow, as well as below ground. Green water is…

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…

A sensory experience that occurs in the absence of corresponding external stimulation of the relevant sensory organ or organs. A hallucination is an apparent perception of something that is not present. It typically arises from a mental or nervous…

A long-keeping cultivar of muskmelon, Cucumis melo inodorus, of the gourd family. Honey Dew melons (see illustration) are members of the family Cucurbitaceae (which includes melons, squashes, pumpkins, and cucumbers) in the order Cucurbitales; they…

The application of experimental findings in behavioral science and physiology to the design and operation of technical systems in which humans are users or operators. Human-factors engineering is a scientific discipline that attempts to integrate…

A group of substances that are natural products of earth surface environments. Probably the most widely distributed organic carbon–containing materials in terrestrial and aquatic environments, they are dark-colored, predominantly aromatic, acidic,…

A presumed altered state of consciousness in which the hypnotized individual is usually more susceptible to suggestion than in his or her normal state. Individuals who undergo hypnosis (also known as hypnotic suggestion) appear to be in a trancelike…

The coding, retrieval, and combination of information in perceptual recognition, learning, remembering, thinking, problem solving, and performance of sensory-motor acts. The brain is the most complex organ of the body, composed of a network of nerve…

Learning based upon the consequences of behavior. Instrumental conditioning, also referred to as operant conditioning, is a method of learning wherein behavior is altered by the effects (either positive or negative) of the resulting consequences.…

General mental ability. Intelligence is the ability to comprehend and reason about things, as well as the skillful use of knowledge. It encompasses the integrative and adaptive functions of the brain (Fig. 1) and permits complex, unstereotyped,…

The gathering, processing, storage, and recall of information received through the senses. The mechanisms involved in learning are associated with those processes, activities, structural components, and alterations of the nervous system that produce…

The accumulated body of scientific and technical writing published to serve the informational needs of, primarily, scientists, engineers, and research workers, and, to the extent that it can be understood, the general public. This vast literature is…

The pattern of care given an offspring by its mother. Maternal behavior constitutes the various aspects of behavior displayed by the female parent in the course of raising its offspring. In most species that care for their young after birth, the…

The intentions, desires, goals, and needs that determine the behavior of humans and other animals. Motivation involves psychological factors and processes that arouse and guide goal-directed behaviors in animals, including humans. With regard to…

The scientific study of the effects of music on the brain. Neuromusicology is a scientific discipline concerned with the function of the brain in music processing. Although neuromusicology is an area of study that utilizes present-day neurological…

The Nobel Prizes for 2019 included the following awards for scientific disciplines. Chemistry The chemistry prize was awarded to John B. Goodenough of the University of Texas at Austin, United States; M. Stanley Whittingham of Binghamton University,…

An anxiety disorder defined by the presence of recurrent, intrusive thoughts (known as obsessions) or repetitive behaviors that a person feels driven to perform (known as compulsions). Individuals with obsessive-compulsive disorder (OCD) experience…

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…