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from article Moho (Mohorovicic discontinuity)

Characteristics of waves traveling along the Moho. (a) Schematic cross section of the continental crust and upper mantle showing typical wave paths from a source of direct waves traveling near the surface of the crust, refracted waves traveling…

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from article Moho (Mohorovicic discontinuity)

Contour map of Moho depth in the United States. Contour values are given in miles (kilometers). (After R. J. Allenby and C. C. Schnetzler, United States Crustal Thickness, Tectonophysics, 93:13–31, 1983)

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from article Herrings

A composite herring. (Illustration courtesy of the Food and Agriculture Organization of the United Nations)

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from article Herrings

Three clupeid juveniles: (top) Atlantic herring (Clupea harengus); (middle) blueback herring (Alosa aestivalis); and (bottom) alewife (Alosa pseudoharengus). (Photo courtesy of Justin Stevens, Northeast Fisheries Science Center, National Oceanic and…

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from article Herrings

Gulf menhaden (Brevoortia patronus). (Photo courtesy of the SEFSC Pascagoula Laboratory, Collection of Brandi Noble, Southeast Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration)

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from article Herrings

Spanish sardine or round sardinella (Sardinella aurita). (Photo courtesy of the SEFSC Pascagoula Laboratory, Collection of Brandi Noble, Southeast Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric…

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from article Travertine

Travertine boulder. (Credit: U.S. National Park Service)

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from article Cocoa powder and chocolate

Cocoa pods on tree. (Credit: Norman Chan/Shutterstock)

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from article Cocoa powder and chocolate

Cocoa beans, powder, and chocolate. (Credit: Fcafotodigital/iStock/Getty Images)

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from article Cocoa powder and chocolate

Chocolate production line. (Credit: Â©bogdanhoda/Shutterstock)

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from article Space navigation and guidance

Jupiter flyby of a space probe in (a) Jupiter's frame of reference and (b) the Sun's frame of reference.

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from article Tunicata

Polycarpa aurata, commonly referred to as the ox heart ascidian, is a tunicate native to the tropical Indo-Pacific region. (Credit: Dwayne Meadows/National Oceanic and Atmospheric Administration)

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from article Tunicata

Representative members of Tunicata: (a) Doliolum, a planktonic thaliacean; (b) Oikopleura, a planktonic appendicularian (larvacean) with a tail, removed from its house. (Credit: P. A. Meglitsch and A. Alldredge)

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from article Myodocopida

Morphology of a typical myodocopid ostracode, an adult female of Cypridina norvegica Baird, viewed from the left side with the left valve removed. (Modified from R. C. Moore, ed., Treatise on Invertebrate Paleontology, pt. Q, Arthropoda, University…

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from article Myodocopida

Morphology of both sexes of Conchoecia elegans Sars, viewed from the left side with the left valve removed. (a) Adult female with eggs. (b) Adult male. (Modified from R. C. Moore, ed., Treatise on Invertebrate Paleontology, pt. Q, Arthropoda,…

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from article Mineral

Peridot is a variety of olivine. Gem-quality peridot, as seen here, is transparent to translucent and pale-, clear-, or yellowish-green in color. (Credit: Albert Russ/Shutterstock)

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from article Alfalfa

Trifoliolate leaves of alfalfa (Medicago sativa). (Photo by Patrick J. Alexander; USDA-NRCS PLANTS Database)

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from article Alfalfa

Flowering alfalfa (Medicago sativa). (Photo by Scott Bauer, Agricultural Research Service, United States Department of Agriculture)

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from article Alfalfa

Cut alfalfa during a harvesting operation in Colorado. (Photo by Howard F. Schwartz, Colorado State University)

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from article Alfalfa

Alfalfa plants affected by symptoms of verticillium wilt. (Photo by William M. Brown, Jr.; Bugwood.org)

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from article Alfalfa

Alfalfa leaf spot caused by Pseudopeziza medicaginis (a fungal plant pathogen). (Photo courtesy of the University of Georgia Plant Pathology Archive; Bugwood.org)

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from article Legume

A variety of legumes. Clockwise from top right: Lentils, fenugreek seeds, fava beans, tepary beans, scarlet runner beans, lupini beans, tarwi beans, and fava bean pods. (Photo by Keith Weller, Agricultural Research Service, U.S. Department of…

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from article Coleoidea

Octopus Benthoctopus photographed by the deep-submergence vehicle ALVIN at a depth of 2770 m (9088 ft), Gorda Ridge, Northeast Pacific Ocean.

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from article Moose

Bull moose (Alces alces). (Photograph courtesy of Jeff Foott/National Park Service)

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from article Cavies

Guinea pig (Cavia porcellus). (Photo courtesy of Anne Moss)

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from article Diorite

Diorite. (Credit: Siim Sepp/Alamy Stock Photo)

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from article Lime (botany)

Fruit and leaves of the lime (Citrus aurantifolia). (Photograph courtesy of Forest and Kim Starr)

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from article Stylolites

Stylolite in limestone.

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from article Notacanthoidei

Spiny eel (Notacanthus abbotti). (Photo courtesy of K. T. Shao, Taiwan Fish Database)

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from article Entodiniomorphida

Ophryoscolex, an entodiniomorphid.

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from article Myrmecochory

A carpenter ant, Camponotus castaneus, carrying a wild ginger seed in the southeastern United States. (Photo by Katharine L. Stuble)

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from article Myrmecochory

Polygala grandiflora seed with elaiosome. This plant species is dispersed by ants in the southeastern United States. (Photo by Katharine L. Stuble)

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from article Amaranth

Amaranth (Amaranthus) flowers and leaves. (Photo by Howard F. Schwartz, Colorado State University)

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from article Genetic dominance

The crossing of tall (dominant AA) and short (recessive aa) homozygous plants in the parent (P1) generation leads to tall heterozygotes (Aa) in the F1 generation of offspring. This is an example of genetic dominance. In the F2 generation, three…

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from article Genetic dominance

The production of phenotypes that are intermediate between those of the parents is an example of partial or incomplete dominance. In this illustration, plants with red flowers crossed to plants with white flowers produce pink offspring in the F1…

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from article Genetic dominance

In codominance, both the dominant and recessive alleles are expressed in heterozygous individuals. The visible expression of a gene is known as the phenotype, whereas the genetic constitution of an individual is known as its genotype. (Copyright ©…

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from article Argentiniformes

Herring smelt (Argentina georgei). (Photo courtesy of the SEFSC Pascagoula Laboratory, Collection of Brandi Noble, Southeast Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration)

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from article Shrew

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from article Basses

Largemouth bass (Micropterus salmoides). (Photo courtesy of Ken Hammond/USDA)

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from article Basses

Chalk bass (Serranus tortugarum). (Photo courtesy of John E. Randall)

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from article Phasmatodea

Walking stick insect. (Photo courtesy of National Park Service)

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from article Earth's gravity field

Level surfaces and plumb lines. The arrow gives the direction of the gravity vector g at point P. W is the gravity potential.

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from article Earth's gravity field

Direction of plumb line is defined by the geographical coordinates ϕ and λ. The unit sphere is frequently used for representing spatial directions.

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from article Earth's gravity field

Gravimetric geoid of Europe, 1957. Geoidal heights in meters (1 m = 3.3 ft), referred to an ellipsoid of flattening 1/297.

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from article Earth's gravity field

Geoid from satellite observations combined with terrestrial gravity measurements (EGM96–360). Geoidal heights are in meters (1 m = 3.3 ft), referred to the Geodetic Reference System 1980.

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from article Earth's gravity field

Pratt isostasy model. 1 km = 0.6 mi.

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from article Earth's gravity field

Airy isostasy model. 1 km = 0.6 mi.

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from article Chiroptera

Anatomical features of bat. (After R. Peterson, Silently by Night, McGraw-Hill, 1964)

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from article Chiroptera

Skeleton of Pteropus, giant fruit bat (lacking tail). (After R. Peterson, Silently by Night, McGraw-Hill, 1964)

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from article Chiroptera

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from article Australia

Map of Australia.

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from article Australia

Climate zones of Australia.

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from article Australia

Land surface characteristics of mainland Australia and Tasmania. (a) Landforms of Australia. (b) Sketch map of predominant geologic structure and major landform regions of Australia. (c) Landforms of Tasmania.

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from article Australia

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from article Australia

Basic vegetation distributions in Australia. (After R. M. Moore ed., Australian Grasslands, Australian National University Press, 1970)

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from article Australia

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from article Australia

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from article Air temperature

Average temperature distribution with height, from the International Reference Atmosphere. Note that the nomenclature for stratosphere and mesosphere varies, the upper part of the stratosphere being considered part of the mesosphere by some…

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from article Acrotretida

Morphology of dorsal (left) and ventral (right) valve interiors of Ceratreta. [After R. L. Kaesler, ed., Treatise on Invertebrate Paleontology, pt H: Brachiopoda, rev. vol. 2, Geological Society of America/University of Kansas Press, Boulder,…

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from article Acrotretida

Ceratreta hebes dorsal valve exterior (a, ×18), interior (b, ×18), and oblique interior, illustrating the median septum (c, ×21); ventral valve exterior, apical view (d, ×15), illustrating the slit-like apical foramen, oblique lateral view (e, ×18)…

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from article Sequoia

Giant sequoia (Sequoiadendron giganteum). The General Sherman Tree, which is the largest (by volume) known tree in the world, is located in Sequoia National Park, California. (Credit: U.S. National Park Service)

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from article Chrysotile

Chrysotile asbestos. (Credit: © McGraw-Hill Education/Bob Coyle)

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from article Chrysotile

Atomic structure of a portion of two contiguous chrysotile layers (Oc = octahedral sheet, Te = tetrahedral sheet). Atoms and bonds are seen on and inside translucent coordination polyhedra. Note the progressive deformation and breaking of hydrogen…

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from article Chrysotile

Chrysotile tube. (a) High-resolution TEM image. (b) Numerical Fourier transform. The fivefold symmetry of the pattern shows up from the 36° angle between visible spots. (Credit: of B. Devouard)

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from article Chrysotile

Polygonal serpentine. (a) TEM image of crosssectioned serpentines, with 15 sectors each. (b) Electron diffraction pattern of a serpentine as a rose with fivefold symmetry. (Credit: A. Baronnet and B. Devouard)

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from article Juniper

Branches and evergreen leaves of eastern redcedar (J. virginiana). (Photo courtesy of Forest and Kim Starr)

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from article Juniper

Habit of western juniper (J. occidentalis). (Photo courtesy of Susan McDougall, USDA–NRCS PLANTS Database)

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from article Juniper

Closeup view of Rocky Mountain juniper (J. scopulorum) showing scalelike leaves and berrylike cones. (Photo courtesy of D. E. Herman, North Dakota State Soil Conservation Committee, USDA–NRCS PLANTS Database)

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from article Upwelling

Regions of major upwelling are stippled.

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from article Upwelling

Schematic diagram of coastal upwelling.

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from article Cytokinins

Structures of naturally occurring (trans-zeatin, cis-zeatin, dihydrozeatin, isopentenyladenine, benzyladenine) and synthetic (kinetin, thidiazuron, CPPU) cytokinins. The purine ring of cytokinins/adenine derivatives is numbered, as shown for zeatin.…

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from article Cytokinins

Typical phenotypes of plants (exemplified by Nicotiana tabacum L.) with cytokinin excess (a, shooty plants expressing an agrobacterial ipt gene for cytokinin biosynthesis) or deficiency (b, dwarf plants expressing CKX genes for cytokinin…

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from article Cytokinins

Scheme of cytokinin signal transduction from membrane receptors (sensor histidine kinases) via phosphotransfer proteins to nuclear transcription factors (B-type response regulators). The histidine-aspartate phosphorelay is shown by the arrows.…

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from article Okra

Okra (Hibiscus esculentus). (Photo courtesy of Forest and Kim Starr)

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from article Agate

Section of polished agate showing the characteristic banding. (Credit: Doug Sherman/Geofile)

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from article Agate

Moss agate cut as gems, showing the dendritic patterns.

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from article Holly

American holly (Ilex opaca). (Photo credit: Larry Stritch, USDA Forest Service)

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from article Pycnogonida

Nymphon, external features in dorsal view.

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from article Pycnogonida

Pycnogonum stearnsi, a common littoral pycnogonid of the Pacific Coast.

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from article Pycnogonida

Protonymphon larva, ventral view.

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from article Ciconiiformes

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from article Varnish tree

Varnish tree (Toxicodendron vernicifluum). To obtain the lacquer, grooves are cut into the bark of the trunk. The exudate (a milky sap) that oozes from these grooves is collected and refined into various types of lacquer. (Photo courtesy of Kintaro…

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from article Heliozoia

Organization of Heliozoia. (a) Actinophryida type. (b) Centrohelida type. (c) Desmothoracida type. (After R. P. Hall, Protozoology, Prentice-Hall, 1953)

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from article Sferics

Sferic that originated 1006 mi (1610 km) from the receiver.

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from article Sferics

Sferic exhibiting a slow tail; it originated in a positive lightning stroke 812 mi (1300 km) from the receiver.

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from article Coquina

Coquina limestone. (Credit: Jacques Cornell/McGraw Hill)

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from article Animal flight

Flamingos take flight at the Lake Bogoria National Reserve in Kenya. (Credit: Shutterstock / Kirill Dorofeev)

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from article Animal flight

Aerodynamics of flight. (a) Airflow around a typical wing profile. (b) Pressure distribution around a typical wing profile. (c) The difference in pressure disappears toward the wingtips as trailing vortices in the wake.

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from article Animal flight

The Southern flying squirrel, Glaucomys volans, in flight. (Credit: Nebraska Game and Parks Commission)

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from article Animal flight

Vortex wakes behind a bird in flapping flight and below a hovering bird. (a) In slow flight, vorticity is shed only during the downstroke, resulting in a stack of vortex rings. (b) In faster flight, lift can be generated also during the upstroke,…

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from article Beaver

American beaver (Castor canadensis). (Photo courtesy of Rocky Mountain National Park, Colorado; National Park Service)

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from article Yak

An adult male domestic yak (Bos grunniens). (Credit: Brent Huffman)

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from article Plant keys

Leaves of six representative trees and shrubs of North America. (a) Leaves are simple and opposite; margins are lobed. (b) Leaves are simple, margins are lobed, and stipules are absent. (c) Leaves are simple and alternate; margins are entire. (d)…

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from article Plant keys

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from article Onyx

Onyx. (Credit: RF Company/Alamy)

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from article Rhubarb

Rhubarb (Rheum rhabarbarum or Rheum rhaponticum). (Photo by P. J. Bennett, Lakewood, OH)

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from article Botanical garden

Colorized photochrom print of the Royal Botanical Gardens at Kew, England, in the 1890s. (Credit: Library of Congress Prints and Photographs Division)

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from article Strongylida

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from article Strongylida

Enterobius vermicularis, adult female. (After F. A. Brown, Selected Invertebrate Types, John Wiley and Sons, 1950)

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from article Xanthophyceae

Xanthophytes. (a) Lutherella, a coccoid xanthophyte epiphytic on another alga, showing vegetative cell, an empty two-piece cell wall, and a zoospore. (b) Tribonema, a filamentous xanthophyte, showing immature zoospores and H-shaped wall segments.…

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