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The ongoing lower level of species extinction intensity occurring between episodes of mass extinctions. Extinction is a normal part of the history of life. Out of every 100 species that have ever lived on Earth, 99 are no longer in existence.…

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 subdiscipline of paleobiology that investigates the processes of preservation and their influence on information in the fossil record. Taphonomy is the study of fossilization and considers the processes at work in the incorporation of living…

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 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…

Most commonly, a generic name for all fossil resins, although it has been restricted by some to refer only to succinite, the mineralogical species of fossil resin that includes most of the Baltic Coast deposits. The time necessary to transform resin…

A genus of fossil birds in the extinct order Archaeopterygiformes, characterized by flight feathers like those of modern birds. Archaeopteryx is generally accepted as the oldest known fossil bird. It represents a unique snapshot of evolution; most…

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…

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 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…

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…

Any living or fossil member of the plant division Pinophyta, consisting chiefly of woody trees or shrubs that produce cones and evergreen needles. Conifers are predominantly cone-bearing, evergreen trees and shrubs belonging to the order Pinales, as…

The death and disappearance of a species. The extinction of a species usually represents an end point in a long series of population extinctions. During the extinction process, unique evolutionary history is lost at every stage, but the death of the…

An enzymatic transformation of organic substrates, especially carbohydrates, generally accompanied by the evolution of a gas. Fermentation is a chemical transformation of organic substrates, especially carbohydrates, to alcohol or organic acids,…

The application of different types of energy and techniques involving equipment and apparatuses to transform agricultural products of plant and animal origin or seafood into food ingredients, semifinished commodities, and finished ready-to-eat…

The study of the physical, chemical, and biological properties of foods as well as the sensory, nutritional, storage properties, and safety of foods. Food properties are influenced by growing, harvesting, and slaughtering practices, preservation and…

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…

A record of earlier life buried in rock. Originally meaning any distinctive object that has been dug up (from Latin fodio, dig), the term “fossil” soon came to refer particularly to things resembling animals and plants. These objects were known…

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…

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…

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),…

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…

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…

Solvent removal from the frozen state by sublimation; commonly referred to as freeze-drying. In lyophilization, the dried material, a porous solid, is sealed under vacuum or inert-gas (liquid nitrogen) atmosphere and retains its physical and…

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…

The widespread, catastrophic loss of many species in a relatively short period of geological time. Earth has supported life for approximately 3.5 billion years, and it is normal for species to become extinct and for new species to arise through…

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…

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…

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 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…

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,…

A morphologically distinct type of trace fossil left by boring organisms in hard biogenic substrates. Oichnus Bromley 1981 is a formal taxonomic name with the rank of ichnogenus (a trace fossil genus). Oichnus is a Latin-derived term that…

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…

Any plant of the genus Olea in the order Lamiales (alternatively Scrophulariales), especially O. europaea, which is cultivated for its drupaceous fruit. Olea europaea is a small to medium-sized evergreen tree (Fig. 1). Olive fruits, both ripe…

A class of the subphylum Asterozoa (phylum Echinodermata), comprising the brittle stars and basket stars, in which the arms are usually clearly demarcated from a central disk and perform whiplike locomotor movements, and the tube feet are…

A taxonomic fish group comprising the bony fishes. The Osteichthyes grouping (often considered a superclass) consists of the classes Actinopterygii (ray-finned fishes) and Sarcopterygii (lungfishes and lobefins, or coelacanths, but excluding…

Fossil lobe-finned (sarcopterygian) fishes of Devonian to Permian age (395–270 million years ago), the ancestral group for the land vertebrates, or “tetrapods.” Phylogeny The term “osteolepiforms” is applied to a range of fossil fishes, found…

An order of extinct jawless vertebrate fishes, also called Cephalaspida, known from the Middle Silurian to Upper Devonian of Europe, Asia, and North America. They were mostly small, about 2 in. (5 cm) to 2 ft (60 cm) in length. The head and part of…

A major taxon of the Crustacea containing small bivalved animals 0.004–1.4 in. (0.1–33 mm) long, with most between 0.04 and 0.08 in. (1 and 2 mm). Members of the Ostracoda inhabit aquatic environments in nearly all parts of the world.…

A popular name applied to several groups of extinct jawless vertebrates (fishes). Most ostracoderms were covered with an external skeleton or armor of bone, from which is derived their name, meaning “shell-skinned” (see illustration). They are known…

A peculiar arthropod, evidently related to the Pycnogonida and represented by a number of well-preserved fossils from the Devonian Hunsrück shales. Palaeoisopus was formerly considered by a number of paleontologists to have an anterior jointed…

A large, extinct assemblage of primitive ray-finned (actinopterygian) fishes known from the Silurian to Cretaceous, which were most numerous in Carboniferous and Permian times. They are known as fossils from all continents except Antarctica.…

A tiny fossil fish found only in rocks of Middle Devonian age within a small geographic region of Caithness, Scotland, and principally at one site, Achanarras Quarry, where it is surprisingly abundant. One of the most enigmatic of all fossil fishes,…

The study of chemical processes used by organisms that lived in the geological past. Most information on the nature of life in the geological past comes from the study of fossils; a record of biochemical processes that occurred can be found in the…

The study of pollen grains and spores, both extant and extinct, as well as other organic microfossils. Although the origin of the discipline dates back to the seventeenth century, when modern pollen was first examined microscopically, the term…

A fossil lobe-finned (sarcopterygian) fish from rock strata of the Baltic region dating to the Middle–Late Devonian Period (about 372–368 million years ago), which provides key evidence about the evolutionary transition from fish to land vertebrates…

An extinct order of relatively large placental mammals represented by Paleocene-Eocene fossils from western Europe, North America, and eastern Asia. Pantodonts were an early evolutionary experiment in large-bodied herbivory by primitive placental…

A type of pepper, Capsicum annuum, with nonpungent flesh, grown for its long red fruit. The paprika pepper (see illustration) is a member of the plant order Solanales (formerly assigned to Polemoniales) and is of American origin. It is most popular…

A medium-sized class of extinct blastozoan echinoderms containing about 17–19 genera, ranging from the late Early Ordovician to the Early Silurian throughout North America and in northern Europe. Their maximum standing diversity (13 genera) occurred…

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 order of herbivorous, odd-toed, hoofed mammals, including the living horses, zebras, donkeys, rhinoceroses, tapirs, and their extinct relatives. Members of the order Perissodactyla, or perissodactyls, are odd-toed ungulates (mammals with hooves).…

A concentration of appreciable numbers of petrified tree trunks exposed at the earth surface, standing upright in the position of growth, lying prostrate, or both. Petrifaction is a form of mineral emplacement or embedding, by which the organic…

An order of mammals comprising the living pangolins and their poorly known fossil predecessors. All living members of the mammalian order Pholidota, that is, the pangolins (also termed scaly anteaters), belong to the family Manidae and are assigned…

An alleged fossil human based on craniodental fragments that were eventually discovered to constitute a skillful hoax. The Piltdown man hoax was the scientifically most successful fraud in the history of anthropology. Between 1908 and 1914, Charles…

One of the major divisions of the seed plants. The most familiar and common representatives of the division Pinophyta are the evergreen, cone-bearing trees of the order Pinales (within the class Pinopsida). Members are known colloquially as…

The single class of the division Pinophyta (Gymnospermae). The class Pinopsida contains both living and fossil taxa. The living representatives of the Pinopsida are woody plants; most are trees with a central axis and excurrent branches. Leaves are…

A class of fishes (Pisces) known from the Devonian Period, and a few that survived into the base of the Carboniferous. They were true fishes or gnathostomes, and can be distinguished from other fishes by the following characters: the gill chamber…

A small group of marine reptiles forming part of the Sauropterygia, known only from deposits of Triassic age in Europe, the Near East (Israel), North Africa (Tunisia), and China. The earliest occurrence of placodonts is in the uppermost Lower…

The worldwide array of plant life, including plants that have roots in the soil, plants that live on or within other plants and animals, plants that float on or swim in water, and plants that are carried in the air. Fungi used to be included in the…

A Paleozoic (Ordovician and Devonian) order of sea stars of the class Asteroidea; only two genera have been recognized. Platyasteridans have relatively elongate flat arms; broad, transversely aligned ventral arm plates; and paxilliform aboral plates…

An order of the Podocopa (Ostracoda) containing a single family, Cytherellidae, and two extinct superorders. Platycopids are small marine or brackish-water ostracods with an asymmetrical shell that is oblong, nearly rectangular, and laterally…

One of two Recent subclasses of Ostracoda. The two (Podocopa and Myodocopa) may share many characteristics but differ significantly in others. Shared characteristics include a carapace (shell) with a straight-to-concave ventral margin and somewhat…

The only order of the superorder Polymixiomorpha, comprising the beardfishes. The order Polymixiiformes (infraclass Teleostei, class Actinopterygii) consists of one family (Polymixiidae) with one genus (Polymixia) and ten extant species. Several…

A class within the phylum Mollusca whose members are popularly called chitons, coat-of-mail shells, or sea cradles. The class Polyplacophora (alternatively Loricata) lies within the phylum Mollusca and comprises the chitons. Members of classes…

A division of the plant kingdom, commonly called the ferns, which is widely distributed throughout the world but is most abundant and varied in moist, tropical regions. The Polypodiophyta are sometimes treated as a class Polypodiopsida of a broadly…

A distinctive and apparently ancient order of actinopterygian fishes comprising the subclass Cladistia, commonly known as bichirs and reedfishes. The following combination of characteristics distinguishes members of the order Polypteriformes from…

An order of placental mammals containing the largest and most powerful living terrestrial mammals—the elephants. Proboscideans once had a wide distribution, reaching every continent except Australia and Antarctica. Although early forms lacked both…

One of the four subclasses of the class Mammalia. Prototheria contains a single order, the Monotremata. No ancestral genera of fossil monotremes are known, and the structure of the living monotremes is so specialized that the affinities of the…

A group long recognized as an order of fossil plants (subdivision Psilopsida) collected in rocks of Late Silurian and Devonian age. It has been subdivided, on the basis of many data, into three categories whose descriptions include the chief kinds…

An order of small, delicate insects, referred to as psocids, bark lice, or book lice. The order Psocoptera (an equivalent name is Corrodentia) belongs to a group (clade), the Acercaria, that also includes the Hemiptera (true bugs, aphids, and…

A subclass of the molluscan class Gastropoda, containing about 23,500 species of snails that are grouped into three orders (or superorders): Systellommatophora, Basommatophora, and Stylommatophora. Pulmonates include most of the common snails found…

An order of very specialized deep-bodied fishes near the holostean level of organization that are known only from the fossil record. They were a widespread group that first appeared in the Upper Triassic of Europe with the genus Eomesodon,…

Brassica napus, a plant of the cabbage family. Rape (Brassica napus) [see illustration] and turnip rape (B. rapa or B. campestris), which are closely related, are members of the Brassicaceae (Cruciferae) plant family [order Brassicales or…

A class of vertebrates composed of turtles, lizards, snakes, crocodilians, amphisbaenians, and tuataras, as well as a variety of extinct forms. The members of the vertebrate class Reptilia are tetrapods, meaning that they possess four limbs or are…

Mentha spicata, an aromatic, vegetatively propagated, clonal cultivar species of the mint family Lamiaceae (Labiatae). The leaves of the spearmint plant are used as a flavoring in foods. In many areas, the mint is grown primarily as a source of the…

Any of the crops produced as major sources of sugar, syrup, and other sugar substances. Sugar crops include sugarbeet (also spelled sugar beet), sugarcane (Fig. 1), sweet sorghum, sugar maple, sugar palm, honey, corn, and chicory. Sugar is a broad…

The most recent and successful group (infraclass) of actinopterygians (ray-finned fishes), first appearing in the Upper Triassic. The members of the Teleostei (teleosts) constitute one of the major fish groups belonging to the class Actinopterygii…

One of the largest recognized groups of early amphibians with about 180 described genera. The Temnospondyli first appear in the fossil record in the lower Carboniferous and reach substantial diversity in the later Carboniferous and Permian. The…

One of the four subclasses of the class Mammalia, including all living mammals except the monotremes. The Theria were by far the most successful of the several mammalian stocks that arose from the mammallike reptiles in the Triassic. The subclass is…

Any of a large and diverse group of perennial plants in the genus Thymus (order Lamiales), whose essential oil and leaves are utilized in cooking and medicine. Hundreds of different forms, or ecotypes, of thyme are found in the Mediterranean area,…

An important paleontological concept that denotes temporal mixing (or age mixing) of fossils. Unlike live-collected organisms, fossils found together within a single stratum need not be contemporaneous with one another, but may represent mixed…

A class of extinct Paleozoic arthropods, occurring in marine rocks of Early Cambrian through Late Permian age. The members of the extinct arthropod class Trilobita are commonly known as trilobites (Fig. 1). With about 5000 described genera and…

A cereal grass plant (× Triticosecale) obtained from the hybridization of wheat with rye. Triticale (Fig. 1) is a crop plant with a small-seeded cereal grain that is used for human food and livestock feed. Plant breeders developed triticale by…

An order of mammals containing a single living genus, Orycteropus, the aardvark. Aardvarks (Orycteropus afer) are the only extant species belonging to the order Tubulidentata. These nocturnal, insectivorous mammals occur in suitable habitats…

A group of benthic marine annelid worms, discovered in 1969, that is restricted to habitats rich in sulfide (for example, hydrothermal vents and sulfide seeps). As adults they lack a mouth, gut, and anus, and are nourished by internal symbionts. All…

A family of Paleozoic elasmobranch sharks that are characterized by teeth with large divergent lateral cusps (diplodont crowns), an elongate dorsal fin preceded by a distinctive spine, and paired fins with an unusually well-developed skeletal axis.…

An order of large, primitive, digitigrade, hoofed, tapirlike mammals with relatively short, slender limbs and five-toed feet with broad, flat phalanges. Members of the order Xenungulata (xenungulates) are restricted to the Paleocene deposits of…

A suborder (xiphosurids, or horseshoe crabs) of the order Xiphosura (phylum Arthropoda). Horseshoe crabs are members of the suborder Xiphosurida. These “sword-tailed” arthropods are a classic example of a “living fossils” group that has seemingly…

A collective name for those fungi that possess, under normal growth conditions, a vegetative body (thallus) consisting, at least in part, of simple, single cells. Yeasts are a phylogenetically diverse group of organisms that occur in two divisions…

One of the major classes composing the superclass Tetrapoda of the subphylum Vertebrata, and including frogs, toads, salamanders, and caecilians. Amphibians, that is, members of the class Amphibia, are tetrapod vertebrates. Modern amphibians number…

The group of primates most closely related to humans. The primates included in the ape group are the African great apes, the gorillas (Fig. 1) and chimpanzees; the Asian great apes, the orangutans; and the lesser apes from Asia, the gibbons. Humans…

A white, crystalline compound, 1-aspartyl-1-phenylalanine methyl ester (APM), used as an artificial sweetener. Aspartame is composed of two amino acids: aspartic acid and phenylalanine [structure (1)]. Amino acid Artificial sweetener Aspartame…

A class of the asterozoan group of the phylum Echinodermata, often known as sea stars or starfish. Members of the class Asteroidea, that is, asteroids, are notable echinoderms with a star-shaped body plan (Fig. 1). Unlike members of their sister…