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Typically, an aquatic vertebrate with scales, gills, and paired fins. Fishes (Fig. 1) are found throughout the world's waterways, from saltwater oceans to freshwater streams and ponds. About 35,000 species of fishes have been described to date. Many…

A plant that has 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…

A commercially grown plant that has 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 biological organism whose genetic material has been manipulated artificially through genetic or genomic editing techniques. In contrast to the long history of artificial selection (domestication), in which humans selectively breed organisms to…

A plant, Musa textilis, of the banana family that is valuable for its hard fiber (also known as Manila hemp). Abaca (Musa textilis) is a flowering plant native to the Philippines and Borneo. Taxonomically, it is assigned to the order Zingiberales.…

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 large aquatic reptile of the family Alligatoridae. Alligators belong to the family Alligatoridae in the reptilian order Crocodylia (Crocodilia). Common usage generally restricts the name alligator to the two extant species of the genus Alligator…

A small, tropical, evergreen tree (Pimenta dioica) and its dried, unripe fruit (berry). Allspice (Pimenta dioica; alternatively, P. officinalis) [see illustration] is a member of the myrtle family (Myrtaceae). Allspice, which is also known as…

Any protozoan moving by means of protoplasmic flow. In their entirety, ameboid protozoans (or ameboid protists) include naked amebas, those enclosed within a shell or test, and more highly developed representatives, such as heliozoians,…

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…

One of the three living orders of the class Amphibia, encompassing the frogs and toads. Anura is the largest order of amphibians (class Amphibia), containing more than 7000 species of frogs (Fig. 1) and toads. Because members of the order Anura…

A natural order of the class Arachnida, commonly known as the spiders. Members of the order Araneae (also called Araneida)—the spiders (Fig. 1)—are widespread over most of the land areas of the world and are well adapted to many different habitats.…

Any vegetable that is prevalent in Asian cuisines, but less well known in Western diets. Asian vegetables (Fig. 1), also referred to as Asian greens or oriental vegetables, are very important in Asian countries, but are not as popular in North…

Any of several leguminous plants, or their seeds, long utilized as food by humans or livestock. There are more than 40,000 varieties of beans, with only a small number of these being mass-produced for human or animal consumption. In particular,…

The drug as well as the plant known as deadly nightshade (Atropa belladonna). The belladonna plant (Atropa belladonna; see illustration) belongs to the nightshade family, Solanaceae, in the order Solanales. The plant is a coarse and poisonous…

The name for two species within the genus Bison of the cattle family Bovidae in the mammalian order Artiodactyla found in North America and Europe. Bison are artiodactyl mammals belonging to the genus Bison (family Bovidae). The North American bison…

A taxonomic order of insects comprising the cockroaches and termites. The order Blattodea, also referred to as Blattaria, contains at least 4500 species of cockroaches (Fig. 1) and 3000 species of termites. Previously, termites were assigned to a…

The name for several members of the family Bovidae in the mammalian order Artiodactyla. The buffalo is an Old World artiodactyl that resembles oxen in general appearance. The North American bison is often called a buffalo, but it is not related to…

Any terrestrial or aquatic animal that is capable of excavating holes in the ground for protection from adverse environmental conditions, as well as for storing food. Burrowing animals are uniquely adapted species, having the capacity to dig burrows…

A member of the mammalian family Camelidae in the order Artiodactyla. Camels are even-toed, hoofed mammals (ungulates). There are three extant camel species: the Bactrian camel (Camelus bactrianus; Fig. 1), the wild Bactrian camel (C. ferus), and…

A medium-sized, spreading evergreen tree (Anacardium occidentale), which is grown widely in the tropics for its kidney-shaped edible nuts (also called cashews) and the resinous oil in the shells of the nuts. Cashew trees, which are native to Brazil,…

A coarse, erect, annual herb plant, Ricinus communis, belonging to the spurge family (Euphorbiaceae). The castor plant (Ricinus communis) is a member of the spurge family (Euphorbiaceae) in the order Malpighiales. The plant varies greatly in height…

A class in the phylum Mollusca that is exclusively marine and includes squids, octopuses, and cuttlefishes. The molluscan class Cephalopoda is one of the major taxonomic groupings of marine animals and contains both extant members—squids (Fig. 1),…

Any member of the grass family (Poaceae or Gramineae) that produces edible grains usable as food by humans and livestock. Cereals are important cultivated crops. Common cereals include rice, wheat, barley, oats, maize (corn), sorghum, rye, and…

An order of the class Reptilia, including the turtles, terrapins, and tortoises; also termed Testudines. The order Chelonia (often referred to as Testudines) comprises one of the oldest groups of reptiles on Earth. Members of the Chelonia…

A type of sweet or sour fruit of the Prunus genus, as well as the tree that bears the fruit. Cherry trees belong to the Prunus genus in the order Rosales, and the sweet and sour fruits of these trees are called cherries (Fig. 1). There are…

The common name for any of 25 species of rodents in the mammalian family Sciuridae. Chipmunks are assigned to three different genera within the mammalian family Sciuridae: Tamias, with 1 species; Eutamias, with 1 species; and Neotamias, with 23…

An evergreen shrub or small tree, particularly Cinnamomum verum, and the spice obtained from the plant's bark. The cinnamon plant (see illustration) is a member of the laurel family (Lauraceae) in the order Laurales. Native to Sri Lanka, the…

A large palm, Cocos nucifera, widely grown throughout the tropics and valuable for its fruit and fiber. The coconut (Cocos nucifera) belongs to the plant family Arecaceae. The name coconut can refer to the tree and its fruit. Usually found near the…

Any of various tropical trees belonging to the genus Cola. Members of the genus Cola (family Malvaceae, order Malvales), which are native to tropical Africa, are called cola trees (see illustration). In particular, two species, C. acuminata and C.…

An order of Insecta comprising the beetles. Beetles belong to the insect order Coleoptera. This is the largest animal order, containing approximately 400,000 species. With so many species, beetles show very great diversity in size, form, color,…

A fiber obtained from the cotton plant Gossypium. The cotton plant (genus Gossypium, order Malvales; Fig. 1) has been used by humans for more than 5000 years. The fiber (cotton) obtained from this plant is the most widely used natural fiber because…

An unharvested crop grown to improve soil quality or enhance pest management. Increasing numbers of farmers plant cover crops as a means of conserving soil, enhancing subsequent production, and reducing off-farm inputs. The sustainable agriculture…

The common name used for the large aquatic reptiles included in the family Crocodylidae. Crocodile (see illustration) is the common name used to describe about 17 species of large aquatic reptiles assigned to the family Crocodylidae, which is one of…

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…

An order of insects commonly known as earwigs, in reference to an unfounded superstition that they crawl into the ears of sleeping persons. Earwigs are elongate and flattened, with a pair of forceps-like appendages, or cerci, at the end of the…

An order of mammals comprising one family (Cynocephalidae), one genus (Cynocephalus), and two species—C. variegatus (Malayan colugo) and C. volans (Philippine colugo). These mammals inhabit the rainforests of Southeast Asia from the Malay Peninsula…

An order of the class Insecta comprising the true flies. Members of the order Diptera (class Insecta, phylum Arthropoda) are known as dipterans or flies (Fig. 1). The name Diptera is derived from the Greek di-ptera, for "two wings," because the…

Any member of the carnivorous mammalian family Canidae. All breeds of domestic dogs (Fig. 1), the wild dogs, and related species belong to the family Canidae. Despite the various breeds of domestic dogs that are known, the scientific name for all…

The biological study of insects that have a direct influence on humanity. Economic entomology is a subdiscipline of entomology (the biological science that deals with the investigation of insects) and focuses on the effects of insects on human…

The common name for three living species of mammals in the family Elephantidae (order Proboscidea). Elephants are extant members of the mammalian family Elephantidae, which is one of several families included in the order Proboscidea. The remaining…

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…

A plant that retains its green foliage throughout the year. An evergreen plant, or simply evergreen, is a tree, shrub, or plant whose leaves are not shed in the winter and instead remain green year-round. In contrast, deciduous trees and plants…

The test of a hypothesis under controlled conditions. The experiment is one of the distinctive tools of the scientist. It enables the scientist to put questions to nature and receive answers. These answers lead to new problems whose solutions…

Plants grown and harvested for food, feed, or industrial purposes. Farm crops may be roughly classified as follows: (1) food crops—the bread grains [wheat (see illustration) and rye], rice, sugar crops (sugarbeets and sugarcane), potatoes, and dry…

Materials added to the soil, or applied directly to crop foliage, to supply elements needed for plant nutrition, and the management of this nutrient application to sustain maximum plant growth and yield while minimizing environmental impacts of…

A plant grown for its fibrous material, which is used for many commercial purposes and for home industry. Many plants are grown as fiber crops because of their content or yield of fibrous material (see illustration), which is used in the manufacture…

The segment of horticulture concerned with the commercial production, marketing, and sale of plants grown and used for decorative or display purposes. Floriculture is a branch of horticulture, that is, the art and science of growing plants,…

Any of the grasses and legumes that make up grasslands and are consumed by grazing livestock. Grasslands represent an ancient renewable natural resource. In general, grasslands form 25% of the world's vegetation and occupy the largest area of any…

The natural medium for growth of tree roots and associated forest vegetation. Proper forest growth and management depend on many factors, including the quality of the forest soil (see illustration). In general, weathering of underlying rock,…

The science, art, and practice of managing and using the natural resources that occur on and in association with forested lands. Forestry is the management of forested lands (see illustration). It involves the planning and implementation of…

A hardy perennial, Allium sativum, of Asiatic origin and belonging to the plant order Asparagales. Garlic is grown for its pungent bulbs (see illustration). Segments of these are used primarily for seasoning. Europeans have grown garlic for probably…

The common name for any of the numerous small lizards in the infraorder Gekkota. Members of the reptilian infraorder Gekkota (order Squamata) are called geckos (see illustration). These small lizards are distinguished by a flattened body [never…

Soil ingestion by animals. Grazing animals such as sheep and cattle ingest varying amounts of soil when they graze herbage contaminated with it.Pastures become contaminated with soil when livestock walk across the herbage, particularly in wet…

An important spice or condiment, and the plant (Zingiber officinale) from which it is obtained. The ginger plant, Zingiber officinale, is a member of the ginger family Zingiberaceae and is a native of southeastern Asia. The plant is an erect…

The common name for a group of perennial herbs in the genus Panax cultivated for the aromatic root of the plant, which is used medicinally in China. Herbal members of the genus Panax belong to the aralia family (Araliaceae) and are native to…

An artiodactyl member of the genus Giraffa in the mammalian family Giraffidae. The giraffe (see illustration) is the only extant member of the genus Giraffa (family Giraffidae, class Mammalia). Giraffes were once thought to consist of a single…

Any of the crop plants belonging to the grass family (Poaceae or Gra­mineae) that are generally grown for their edible starchy seeds. Grain crops are often referred to as cereal crops and include wheat, rice, corn (maize), barley (see illustration),…

The common name for plants of the genus Vitis characterized by climbing stems and grown for the edible, pulpy berries. Grapes (genus Vitis) comprise one of the world's most significant and economically important crops. The common grapevine is…

An evergreen tree (Citrus paradisi) and its edible citrus fruit. Grapefruit (Citrus paradisi) is a subtropical evergreen tree belonging to the order Sapindales. It has a well-rounded top and is cultivated for its large and globose citrus fruit. The…

Any member of the family Poaceae (Gramineae) cultivated as forage and grain for consumption. Grasses are arguably the most useful of all the plants that cover the Earth. The cereal grass crops [wheat (Fig. 1), rice, corn (maize), rye, barley, oats,…

An uncrewed, controlled-flight vehicle that is guided to a target by guidance and control equipment. This equipment may be carried in the missile vehicle itself, or guidance may be directed from the launch site. The term is generally reserved for…

Optical instruments that establish an optical line or axis for the purpose of aiming a weapon. The axis includes the observer's eye, a suitable mark in the instrument, and the target. For a pistol, the traditional iron sights employ a rear notch and…

An intensively managed plant cultivated for food or for esthetic purposes. Plant agriculture is divided traditionally into the fields of agronomy (herbaceous field crops, mainly grains, forages, oilseeds, and fiber crops), forestry (forest trees and…

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)…

An African carnivore belonging to the family Hyaenidae. The mammalian family Hyaenidae (order Carnivora) comprises three species of hyenas (also spelled hyaenas): one species (spotted hyena) in the genus Crocuta (see illustration), one species…

A tentative supposition with regard to an unknown state of affairs, the truth of which is thereupon subject to investigation by any available method, either by logical deduction of consequences which may be checked against what is known, or by…

The study of the functional properties of insect tissues and organs. Insect physiology is a branch of biology that investigates how insects live and function. Insects are one of the most diverse groups of animals on Earth and have evolved…

Any of several low, perennial, tropical South American shrubs or half-shrubs in the family Rubiaceae. Ipecac plants (also termed ipecacuanha plants) are native to the tropical forests of Brazil and Colombia. Several species are used, but the dried…

The artificial application of water to the soil to produce plant growth. Irrigation also cools the soil and atmosphere, making the environment favorable for plant growth. The use of some form of irrigation (Fig. 1) is well documented throughout the…

An arachnid taxon comprising the ticks. Ticks are arachnids (Fig. 1). Specifically, they are members of the Ixodida, which is considered to be an order or suborder (depending on the exact classification) of the subclass Acari (Acarina) in the class…

Intentional generation of interfering signals in the electromagnetic spectrum by powerful transmitters as a countermeasure intended to block a communication, radar, or infrared system or to impair its effectiveness appreciably. Radio broadcasts or…

The common name for a member of the agnathan fishes. The fish superclass Agnatha (subphylum Vertebrata, phylum Chordata) comprises the jawless vertebrates (agnathans). Members include cyclostomes (modern lampreys and hagfishes), various extinct…

A single species, Phascolarctos cinereus, which is the sole extant member of the family Phascolarctidae in the mammalian order Marsupialia (pouch-bearing animals). The koala (see illustration) is a small, clean, affectionate animal that weighs from…

The removal of water from the surface of the land and the control of the shallow ground water table improves the soil as a medium for plant growth. The sources of excess water may be precipitation, snowmelt, irrigation water, overland flow or…

Citrus limon, a small evergreen tree belonging to the order Sapindales that is cultivated for its fruit. In commercial terms, the lemon (Citrus limon; order Sapindales) is the most important of the acid citrus fruits (see illustration). It probably…

Lama glama, a member of the camel family (Camelidae) found only in South America. The llama (see illustration) is an artiodactyl, or even-toed ungulate, belonging to the mammalian family Camelidae. It has two toes on each foot. The llama is a…

A lineage of true elephants in the extinct genus Mammuthus that occupied Eurasia and North America in the late Cenozoic Era. Mammoths (genus Mammuthus) are extinct elephants assigned to the mammalian order Proboscidea (Fig. 1). They inhabited…

A psychoactive narcotic drug obtained from the dried leaves, stems, seeds, and flowering tops of the hemp plant, Cannabis sativa. Cannabis sativa (Fig. 1), commonly called cannabis, is the source of marijuana, which is one of the most widely used…

The names associated with a great number of species of mammals in a number of different families of the order Rodentia. The rodents constitute the largest order (Rodentia) of mammals, and they include approximately 2300 species, or about 42% of the…

The body of knowledge that concerns the fundamental nature, function, development, and use of formal models in science and technology. In its most general sense, a model is a proxy. A model is one entity used to represent some other entity for some…

A major phylum of the animal kingdom comprising a diverse group of unsegmented, soft-bodied invertebrates. The phylum Mollusca is one of the most significant groupings of invertebrate animals. Members of the Mollusca, termed mollusks or molluscs,…

A mammalian order containing the egg-laying platypus and echidnas. Members of the order Monotremata (monotremes) are egg-laying mammals belonging to the subclass Prototheria (in some alternative classifications, the monotremes have been assigned to…

An even-toed, bovid ungulate, Ovibos moschatus. The musk-ox (Ovibos moschatus) is a member of the family Bovidae in the mammalian order Artiodactyla. The single species of musk-ox (see illustration) is the northernmost representative of the family,…

Weapons that arm warships. Of the wide variety of such weapons, three important categories are exclusively naval: antiship missiles, torpedoes, and mines. Other weapons all correspond to land-based types, but submarine-launched ballistic missiles…

A tree that can convert (fix) atmospheric nitrogen into a form that can be utilized for growth. The ability to convert (fix) atmospheric nitrogen into a form that can be used for plant growth is confined to bacteria and cyanobacteria. Plants fix…

The Nobel Prizes for 2021 included the following awards for scientific disciplines. Chemistry The chemistry prize was awarded jointly to Benjamin List of the Max-Planck-Institut für Kohlenforschung, Mülheim an der Ruhr, Germany, and David W.C.…

The cultivation of plants, primarily trees, that produce nuts. The term nut is used loosely. In general, a nut is defined as any edible fruit or seed enclosed in a hard shell. Botanically, a nut is a hard, indehiscent, one-seeded (nut), pericarp…

A delicately flavored spice obtained from the nutmeg tree (Myristica fragrans), a native of the Moluccas (Maluku Islands or Spice Islands). The nutmeg tree is a dark-leafed evergreen that can reach 9–18 m (30–60 ft) in height and is a member of the…

A genus (Quercus) of trees, some of which are shrubby, with about 200 species, mainly in the Northern Hemisphere. About 50 species of oaks are native in the United States. All oaks have scaly winter buds, usually clustered at the ends of the twigs,…

An agricultural cereal crop of the genus Avena grown for its grain and straw. Oats (Fig. 1) belong to the genus Avena in the family Poaceae (Gramineae) of the order Poales (Cyperales). The most important crop species is Avena sativa, known as the…

A small extinct order of articulated brachiopods that ranges in age from Early to Middle Cambrian and includes the earliest known calcitic brachiopods. Classification The order Obolellida is included within the class Obolellata, subphylum…

A subclass of Anthozoa consisting of colonial cnidarians. Members of the subclass Octocorallia (Alcyonaria) are benthic as adults, living attached to firm substrata or burrowed into soft sediments, from the intertidal zone to great depths. As in all…

An order of coleoid cephalopods, characterized by eight appendages (which encircle the mouth), a saclike body, and an internal shell that is much modified or reduced from that of its ancestors. Members of the order Octopoda (subclass Coleoidea,…

An order of the class Insecta, commonly known as dragonflies and damselflies. Odonates (Fig. 1) generally are conspicuous insects with strong flying ability and a complex range of behaviors. They occur on all continents except Antarctica, although…

A former primitive order of brittle stars (class Ophiuroidea) reassigned to the order Ophiurida. The order Oegophiurida is an invalid taxon of brittle stars. Formerly comprising a single living genus, Ophiocanops, the members of this former order…

A warm-season annual, Hibiscus esculentus (also Abelmoschus esculentus), of Ethiopian origin. Okra, also called gumbo, is grown for its immature pods (see illustration), which are used generally in the preparation of soups, but are also eaten as a…

A suborder of trilobites (a class of extinct arthropods) and a diverse clade consisting of roughly 100 distinct species. The trilobites constituting the suborder Olenellina belong to the order Redlichiida in the class Trilobita. These extinct…

A subclass of worms, including the earthworms, within the class Clitellata of the phylum Annelida. Oligochaeta is an important annelid subclass of worms. The most notable worm types belonging to the Oligochaeta are earthworms (Fig. 1). In general,…

An extinct order of irregular echinoids in the superorder Neognathostomata resembling clypeasteroids but lacking the accessory ambulacral pores characteristic of that group. Oligopygoids have well-developed petals, and there are characteristic small…