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from article Information processing (psychology)

The four major lobes of the cerebral cortex, that is, the frontal, parietal, temporal, and occipital lobes, are responsible for different aspects of information processing. (Copyright © McGraw-Hill Education)

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from article Information processing (psychology)

Horizontal associative memory with a serious associative interference problem (who plays tennis—John, Peter, or both?) and no encoding of where each proposition begins and ends. (Copyright © McGraw-Hill Education)

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from article Information processing (psychology)

Vertical associative memory where concepts are grouped into phrases and propositions by associating each concept to a higher-order node that represents the entire group. (Copyright © McGraw-Hill Education)

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from article Octopoda

An octopod swimming in the ocean. (Credit: Getty Images/iStockphoto)

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from article Octopoda

Hapalochlaena maculosa, the Southern or lesser blue-ringed octopus, has vivid, small blue rings on its body and arms, highlighted with black outlines. Location: Mrs. Watson's Bay, Lizard Island, Great Barrier Reef, Australia. (Credit: Clyde F. E.…

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from article Octopoda

Hapalochlaena fasciata, the blue-lined octopus, has vivid blue lines on its body and rings on its arms, highlighted with black outlines. Location: Long Reef, New South Wales, Australia. (Credit: Clyde F. E. Roper)

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from article Octopoda

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from article Polyplacophora

Chiton on a rock surface. (Photo courtesy of the NOAA Okeanos Explorer Program, National Oceanic and Atmospheric Administration)

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from article Polyplacophora

Polyplacophoran mollusk (chiton): (a) dorsal view; (b) ventral view.

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from article Eclipse

The August 21, 2017 total solar eclipse, as seen from Hopkinsville, Kentucky, USA at 2:25 p.m. EDT. (Credit: NASA)

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from article Eclipse

Circumstances of solar and lunar eclipses (not to scale).

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from article Eclipse

Diamond-ring effect at the beginning of totality during the solar eclipse of July 11, 2010, observed from Easter Island in the middle of the Pacific Ocean. (Credit: Jay M. Pasachoff/Science Faction, Muzhou Lu, and Craig Malamut, Williams College…

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from article Eclipse

Total solar eclipse of July 11, 2010, observed from Easter Island in the Pacific Ocean. (a) Image composited from several exposures using radial filters in order to show a wide dynamic range of intensity of the corona and to bring out the structures…

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from article Eclipse

Solar eclipse of April 8, 2005, observed during totality from a ship in the mid-Pacific Ocean, west of the Galápagos Islands. (Credit: Jay M. Pasachoff and Dava Sobel/Science Faction)

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from article Eclipse

Paths of all total solar eclipses from 2001 through 2025. The point of greatest eclipse is indicated by an asterisk on each eclipse path. (Credit: Eclipse map by Michael Zeiler, www.eclipse-maps.com. Eclipse paths by Xavier Jubier, xjubier.free.fr.)

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from article Eclipse

Cross section through the Earth's shadow cone (umbra) at the Moon's distance, showing the motion of the Moon at three types of lunar eclipses: penumbral eclipse, partial umbral eclipse, and total umbral eclipse.

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from article Eclipse

Stages of the total lunar eclipse of December 21, 2010. (Credit: Glenn Schneider)

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from article Eclipse

Total lunar eclipse of December 9, 1992, which was so dark that it rendered the Moon nearly invisible during totality. (Credit: F. Espenak)

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from article Pituitary gland disorders

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from article Pituitary gland disorders

Infarction (obstruction of the blood supply) of the pituitary gland. This pituitary gland is almost entirely infarcted. Only a thin rim of viable cells remains (arrow). Pituitary infarcts can occur during pregnancy (Sheehan's disease) or as a result…

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from article Clathrate compounds

Schematic drawing of the lattices of (a, c) urea and (b, d) thiourea; c and d show accommodation of unbranched and branched paraffin chains, respectively.

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from article Clathrate compounds

Molecular model of α-dextrin–iodine compound seen in the direction of the c axis, that is, in the direction of the iodine chains, which lie in channels.

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from article Trace fossils

Domichnial dwelling burrow with pelleted wall, probably created by a burrowing crustacean. Ophiomorpha, Cretaceous, North Dakota. (From W. Häntzschel, in C. Teichert, ed., Treatise on Invertebrate Paleontology, pt. W, revised, University of Kansas…

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from article Trace fossils

Highly branched, fodinichnial mining burrow, possibly produced by a deposit-feeding crustacean or worm. (a) Chondrites, Tertiary, Austria. (b) Chondrites, Tertiary, Spain. (From W. Häntzschel, in C. Teichert, ed., Treatise on Invertebrate…

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from article Trace fossils

Agrichnial farming trace of an unknown organism, composed of a hexagonal, meshlike network of tunnels. Paleodictyon, Tertiary, Poland. (Photograph by W. Häntzschel)

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from article Trace fossils

Agrichnial farming traces of unknown organisms, including a double-spiral tunnel (Spirorhaphe) and a meshlike network of tunnels (Paleodictyon). Tertiary, Austria. (Photograph by W. Häntzschel)

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from article Trace fossils

Loosely meandering, agrichnial farming trace of an unknown organism. Cosmorhaphe, Tertiary, Poland. (From W. Häntzschel, in C. Teichert, ed., Treatise on Invertebrate Paleontology, pt. W, revised, University of Kansas Press, 1975)

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from article Trace fossils

Praedichnial boring drilled in a bivalve shell by a carnivorous gastropod. Oichnus, Recent, Texas. (Photograph by A. A. Ekdale)

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from article Trace fossils

Tightly meandering, pascichnial grazing trail, created by an unknown worm. Helminthoida, Tertiary, Austria. (From W. Häntzschel, in C. Teichert, ed., Treatise on Invertebrate Paleontology, pt. W, revised, University of Kansas Press, 1975)

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from article Trace fossils

Repichnial trail of an arthropod, possibly a trilobite. Cruziana, Cambrian, Alberta. (Photograph by J. P. A. Magwood)

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from article Trace fossils

Unnamed escape structure (fugichnial trace) in sandstone. Cretaceous, Utah. (Photograph by A. A. Ekdale)

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from article Trace fossils

Cubichnial resting trace of an ophiuroid brittle star. Asteriacites, Jurassic, Germany. (Photograph by W. Häntzschel)

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from article Trace fossils

Complex, composite ichnofabric created by numerous successive phases of burrowing in a fine-grained pelagic carbonate deposit, which has been weakly cemented to become chalk. Upper Cretaceous, Denmark. (Photograph by A. A. Ekdale and R. G. Bromley)

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from article Aconchulinida

Aconchulinida. (a) Penardia cometa. (b) Penardia mutabilis.

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from article Phonoreception

Generalized sketch of the vertebrate labyrinth. The three cristae, macula ultriculi, and macula sacculi are always present in vertebrates, and the other endings appear as indicated, with a few exceptions.

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from article Phonoreception

Diagram (from above) of the two labyrinths of an ostariophysan fish and their connections with the swim bladder through the Weberian ossicles.

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from article Phonoreception

Simplified diagram of the frog ear.

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from article Phonoreception

Diagram of the ear of a snake. The nonauditory parts and endings are not shown.

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from article Phonoreception

Auditory sensitivity of a wood turtle (Clemmys insculpta), as shown by the potentials produced in its ear by sounds. The curve shows the sound pressure necessary to produce a potential of 0.3 microvolt.

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from article Phonoreception

Graph showing threshold sensitivity in the bullfinch (mean of four birds). (Credit: J. Schwartzkopff)

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from article Phonoreception

Auditory thresholds in primates. The curves show the sound pressures that are barely audible for humans, chimpanzees, rhesus monkeys, and marmosets.

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from article Phonoreception

Diagram of the ear of a grasshopper.

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from article Phonoreception

Auditory thresholds of the katydid (Conocephalus strictus). Sensitivity is greatest in the 7000–60,000-Hz region. (Credit: E. G. Wever and J. A. Vernon)

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from article Siphonaptera

Head of Spilopsyllus cuniculi (rabbit flea), with extended mouthparts.

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from article Planet

An artist’s impression of a mere sampling of the planetary diversity expected to exist in nature. [Credit: C. Pulliam & D. Aguilar (CfA)]

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from article Planet

Plan of the solar system's major and dwarf planets. (a) Solar system out to Neptune. (b) Dwarf planets in the outer solar system (Credit: Emily L. Schaller)

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from article Planet

Orbital elements, which determine the position of a planet in its orbit and the orientation of the orbit in space. Symbols explained in text.

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from article Planet

The interiors of the 8 planets and the dwarf planet Pluto. Mercury, Venus, Earth, and Mars are characterized by dense, metallic cores and lower-density mantles and crusts. Jupiter and Saturn have compositions that mimic the Sun's, though…

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from article Planet

Complex lunar crater Bullialdus, 60 km (37 mi) in diameter, shows terraced sides, a central peak, and a flat bottom. It may be compared to the small (less than 8 km or 5 mi) crater in the foreground, which is simple and bowl-shaped. (Credit: NASA)

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from article Planet

Ultraviolet images from the Hubble Space Telescope, which reveal auroral emission surrounding the north magnetic pole of Jupiter. [Credit: NASA, ESA, and J. Nichols (University of Leicester)]

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from article Neandertals

Neandertal cranium excavated from Forbes' Quarry, Gibraltar. Note the pronounced brow ridges, large braincase, and receding forehead. (Credit: Clive Finlayson/Gibraltar Museum)

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from article Neandertals

Gorham's Cave, Gibraltar, is the last known site of Neandertal occupation, being dated possibly to 30,000 years ago. (Credit: Clive Finlayson/Gibraltar Museum)

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from article Neandertals

Reconstructed skull of a Neandertal from the cave at La Chapelle-aux-Saints, France. (Credit: Illustration adapted from an original drawing by M. F. Ashley Montagu)

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from article Root (botany)

Kinds of roots. (a) Adventitious, on a cutting or slip (geranium). (b) Prop and other adventitious (corn). (c) Fibrous adventitious (grass). (d) Primary, or taproot (dandelion). (e) Fleshy taproot (carrot). (f) Fleshy, fascicled adventitious…

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from article Root (botany)

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from article Root (botany)

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from article Root (botany)

Distribution of tissues in a typical root apex.

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from article Root (botany)

Transverse sections of roots, showing primary and secondary tissues. (a) Soybean. (b) Barley. (c) Soybean; enlarged part of a, showing early formation of cambium. (d) Soybean with abundant secondary tissue.

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from article Root (botany)

Diagrams of vascular transition in dicotyledonous seedling (beet, Beta vulgaris) from root tip upward to level of cotyledons. (a) Root is diarch; its vascular tissues are continuous with those of (e) the cotyledons through (b–d) the transition…

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from article Island biogeography

Equilibrium number of species (Sequilibrium) is determined by the intersection of the immigration ( I ) and extinction ( E ) rate curves. P is the maximum number of species in the source pool.

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from article Notch signaling

Notch-ligand interactions. Two Notch ligands, Delta and Serrate, are shown on the signal-sending cell (left). These ligands are distinguished by differing numbers of EGF-like repeats (indicated by the light boxes) and an extracellular cysteine-rich…

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from article Wilkinson Microwave Anisotropy Probe

Wilkinson Microwave Anisotropy Probe (WMAP) spacecraft. (Courtesy of NASA/WMAP Science Team)

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from article Wilkinson Microwave Anisotropy Probe

WMAP sky-scan strategy. (a) Location of the satellite relative to the Earth and Sun (not to scale), and the orientation of the satellite and of the lines of sight to the spots on the sky focused by the primary reflectors, which continually changed…

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from article Wilkinson Microwave Anisotropy Probe

WMAP full-sky CMB anisotropy map. The microwaves captured in this picture from WMAP are from when the universe was 378,000 years old, over 13 × 109 years ago. It is a “baby picture” of the universe, equivalent to taking a picture of an 80-year-old…

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from article Folic acid

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from article Digenea

Diagrams of various adult types of digenean trematodes. (After R. M. Cable, An Illustrated Laboratory Manual of Parasitology, Burgess, Minneapolis, 1940)

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from article Digenea

Digenean trematode life cycle. (After R. M. Cable, An Illustrated Laboratory Manual of Parasitology, Burgess, Minneapolis, 1940)

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from article Hydroponics

Green- and red-leaf lettuce growing in a hydroponic vegetable garden on a bamboo fence. The pipes, which supply nutrients and water, are part of the hydroponic system. (Credit: Piyachok Thawornmat, Shutterstock)

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from article Hydroponics

Hydroponic techniques: (a) aerated standing culture; (b) flowing-solution culture with standing solution; (c) nutrient film technique; (d) aeroponics.

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from article Urinary bladder

Light micrograph of the healthy transitional epithelium tissue (stained by hematoxylin and eosin) of a urinary bladder. The transitional epithelium is a type of tissue consisting of multiple layers of epithelial cells, which can contract and expand.…

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from article Urinary bladder

Types of tubal bladders: (a) duplex; (b) bilobed; (c) simplex, with ureters united; (d) simplex, with separate ureters. (Credit: H. E. Walter and L. P. Sayles)

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from article Flower

Flower structure, median longitudinal section.

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from article Flower

Diagrammatic section of an orange blossom. (After J. B. Free, Insect Pollination of Crops, Academic Press, 1970)

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from article Flower

Flower of Penstemon, a member of the foxglove family, in section. (After C. E. Wood, Jr., A Student's Atlas of Flowering Plants: Some Dicotyledons of Eastern North America, Harper and Row, 1974)

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from article Flower

Longitudinal section of a flower bud and one carpel in section of blackberry (Rubus betulifolius). (After K. R. Robertson, The genera of Rosaceae in the southeastern United States, J. Arnold Arbor., 55:344–401, 1974)

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from article Flower

Placentation: (a) parietal, (b) axile, and (c) free central. (After P. H. Raven, R. F. Evert, and H. Curtis, Biology of Plants, Worth Publishers, 1976)

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from article Flower

Nectaries. (a) Cherry flower (after W. H. Brown, The bearing of nectaries on the phylogeny of flowering plants, Proc. Amer. Phil. Soc., 79:549–595, 1938). (b) Flower of nasturtium (after B. J. D. Meeuse, The Story of Pollination, Ronald Press,…

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from article Flower

Sunflower (Helianthus annuus) of the composite family. (a) Inflorescence in section. (b) Side view of ray floret. (c) Side view of tubular floret. (d) Section of tubular floret. (After J. B. Free, Insect Pollination of Crops, Academic Press, 1970)

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from article Flower

Successive stages of flower formation in a wood sorrel. (a) Sepals and petals already initiated; the androecium begins as five bumps on the floral apex; five more will be added. At maturity, five long stamens will alternate with five short ones. (b)…

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from article Flower

Lily anther. (a) Cross section of young anther showing four microsporangia with sporogenous tissue. (b) Cross section of mature anther with two pollen sacs containing pollen. (After A. W. Haupt, Plant Morphology, McGraw-Hill, 1953)

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from article Flower

Gametophyte: (a) embryo sac and (b) pollen tube. (After O. Tippo and W. L. Stern, Humanistic Botany, W. W. Norton, 1977)

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from article Tomato

Tomatoes (Solanum lycopersicum). (Credit: Peggy Greb, Agricultural Research Service, U.S. Department of Agriculture)

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from article Tomato

Tomato affected by anthracnose (caused by the fungus Colletotrichum phomoides). (Credit: U.S. Department of Agriculture Cooperative Extension Slide Series, Clemson University)

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from article Tomato

Tomatoes showing blossom-end rot. (Credit: Mary Ann Hansen, Virginia Polytechnic Institute and State University)

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from article Electrolysis

Electrolysis cell in which the electrolyte is a solution of sodium chloride.

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from article Learning

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from article Learning

Brain activity can be recorded in various ways, from single-cell activity (top tracing) to the familiar electrical patterns ("brain waves") of an electroencephalogram (bottom tracing). (Credit: Based on an original drawing by C. Cotman and J.…

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from article Pine nut

Pine nuts in their hard shell (Mexican piñon pine, Pinus cembroides). (Photo by Steve Hurst, U.S. Department of Agriculture–Natural Resources Conservation Service PLANTS Database)

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from article Pine nut

Cone containing pine nuts (stone pine, Pinus pinea). (Photo by Vito Buono, Bari, Italy)

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from article Ultracentrifuge

Diagram of an electrically driven analytical ultracentrifuge. (Beckman Instruments)

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from article Ultracentrifuge

Analytical rotor. (Beckman Instruments)

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from article Ultracentrifuge

Fixed-angle preparative rotor and tubes. (Beckman Instruments)

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from article Biofilm

Biofilms are highly structured communities of microorganisms that are surface-associated or attached to one another, and are enclosed within a self-produced protective extracellular matrix. Biofilm formation and actions involve a number of stages:…

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from article Ctenothrissiformes

A Cretaceous ctenothrissiform fossil, Ctenothrissa sp. (order Ctenothrissiformes), on a limestone matrix found in Lebanon. Size: 90 mm (3.5 in.). (Photo courtesy of The Virtual Fossil Museum)

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from article Equisetales

Equisetum arvense. (a) Sterile shoot. (b) Fertile shoot growing from an underground rootstock. (c) Cone. (d) Two views of shield-shaped sporangiophores. (e) Spores, greatly enlarged. As spore dries, elaters expand. (After E. W. Sinnott and K. S.…

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from article Equisetales

Equisetum gametophyte. (a) Small gametophyte, showing antheridia only. (b) Male gametes. (c) Larger gametophyte; branching lobes have archegonia at bases. (After E. W. Sinnott and K. S. Wilson, Botany: Principles and Problems, 6th ed., McGraw-Hill,…

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from article Equisetales

Sporophytes. (a) Equisetum gametophyte with sporophytes. (b, c, d) The young sporophytes of Equisetum hiemale. (After G. M. Smith, Cryptogamic Botany, vol. 2, 2d ed., McGraw-Hill, 1955)

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from article Lung

Human lungs. (a) The trachea bifurcates as the right and left primary bronchi that enter each lung. The bronchi subdivide further to form the bronchial tree. (b) Color-coded view of the major branches of the bronchial tree. (Copyright © McGraw Hill)

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from article Animal testing

Mice are the most commonly used vertebrate species in animal testing and research. (Credit: Dolores Bonaparte)

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from article Animal testing

The use of animals in biomedical research remains essential, but the handling of these sentient beings must be done humanely to minimize and prevent animal harm. (Credit: U.S. Department of Agriculture)

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