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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 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 Strychnos

Strychnos nux-vomica: close-up view of leaves and flowering branch. (Photo courtesy of Dinesh Valke)

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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 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 Breadfruit

Breadfruit (Artocarpus altilis), showing the rounded (or elliptic) fruit and the cylindrical staminate flower cluster. (Photo courtesy of Forest and Kim Starr)

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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 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 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 Mango

Tommy Atkins cultivar of mango (Mangifera indica) growing in Florida. (Credit: Wilhelmina Wasik/Agricultural Research Service, U.S. Department of Agriculture)

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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 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 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 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 Pathotoxin

Oat seedling resistant to Victoria blight obtained by screening a susceptible population with the pathotoxin victorin, a product of the pathogen Helminthosporium victoriae.

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from article Pathotoxin

Separation of corn seedlings resistant (N) and susceptible (T) to southern corn leaf blight by treatment with a pathotoxin produced by Helminthosporium maydis race T.

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from article Pathotoxin

Chemical structures of four pathotoxins. (a) Fusicoccin. (b) Tentoxin. (c) AM-toxin. (d) HMT-toxin.

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from article Tree ferns

Cyathea cooperi (Australian tree fern), a common member of the family Cyatheaceae. (Photo by Forest and Kim Starr)

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from article Tree ferns

Arrangement of leaves of Cyathea cooperi (Australian tree fern). (Photo by Bryan Harry, Haleakalā National Park, National Park Service, Maui, Hawaii)

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from article Circadian clock (plants)

Three-module circadian clock system.

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from article Circadian clock (plants)

Model of the Arabidopsis circadian clock, showing light input (bold arrow), the central oscillator (large box) and output/response (tinted arrows). Light signals synchronize the clock via the cryptochromes (cry) and phytochromes (phy). These are…

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from article Ecosystem

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from article Ecosystem

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from article Ecosystem

Food chains are limited by energy transfer. In this illustration, energy is transferred from the Sun to a plant (producer) to a primary consumer and to a secondary consumer. Energy is used by the producer and consumer organisms and is lost to the…

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from article Ecosystem

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from article Ecosystem

General model of the carbon cycle in ecosystems: (A) carbon dioxide (CO2) from the air; (B) carbon from decomposition; (C) carbon from fossil fuels; (D) natural events (for example, forest fires and volcanoes) release CO2 into the air. (Copyright ©…

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from article Poplar

Quaking aspen (Populus tremuloides). (Photo courtesy of North Dakota State Soil Conservation Committee, USDA–NRCS PLANTS Database)

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from article Poplar

Common poplar species. (a) Quaking aspen (P. tremuloides); leaf scar with an axial bud, leaf, and twig. (b) Bigtooth aspen (P. grandidentata); leaf, terminal bud, and twig. (c) Cottonwood poplar (P. deltoides); leaf, leaf scar, terminal bud, and…

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from article Biodiversity

Global biodiversity hotspots. There are more than 30 biodiversity hotspots located around the world. These areas have experienced severe habitat losses (at least 70%) as the result of human activities, hampering the work of conservationists in their…

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from article Biodiversity

A regional analysis of 25 oceanic regions shows that 92% of all known biodiversity falls into a dozen groups, of which crustaceans (for example, crabs, shrimps, and lobsters), mollusks (for example, snails, bivalves, squids, and octopus), and fish…

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from article Biodiversity

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from article Gibberellin

Carbon skeleton of ent-gibberellane showing the carbon numbering system and ring designations. (Credit: Peter Hedden)

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from article Gibberellin

The GA-biosynthetic pathway in higher plants via 2-methylerythritol-4-phosphate (MEP). The biologically active end products of the pathway are GA1, GA3, and GA4. The general diterpene precursor trans-geranylgeranyldiphosphate (GGPP) is formed in…

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from article Gibberellin

Mechanisms for GA inactivation. C19-GAs and C20-GAs may be oxidized on C-2 by different classes of GA 2-oxidases (GA2ox). In rice, the enzyme ELONGATED UPPER INTERNODE (EUI) oxidizes the 16,17-double bond of non–13-hydroxylated GAs, such as GA4, to…

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from article Gibberellin

Illustration of a DELLA protein showing conserved domains, and a model for DELLA degradation via the SCF E3 ubiquitin ligase, which consists of a DELLA-specific F-box, Skp1, Cullin1 (CUL), and Rbx1 subunits. Binding of the GID1-GA complex to DELLAs…

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from article Gibberellin

Model for GA-induced production of α-amylase in the aleurone of germinating cereal grains. GAs produced in the scutellum diffuse to the aleurone cells, where they stimulate transcription, processing, and secretion of α-amylase and other hydrolytic…

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from article Urodela

A typical member of the order Urodela: the longtail salamander (Eurycea longicauda). (Credit: Ryan Hagerty/U.S. Fish and Wildlife Service)

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from article Urodela

Southern dwarf siren (Pseudobranchus axanthus), which has undergone limb degeneration and retains only tiny forelimbs. (Credit: U.S. Geological Survey)

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from article Urodela

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from article Urodela

California tiger salamander (Ambystoma californiense). (Credit: John Cleckler/U.S. Fish and Wildlife Service)

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from article Urodela

The two-toed amphiuma salamander (Amphiuma means). (Credit: Southeast Ecological Center, U.S. Geological Survey)

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from article Urodela

The northern red salamander (Pseudotriton ruber ruber) is a member of the family Plethodontidae. (Credit: Alicia Lafever/U.S. National Park Service)

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from article Thirst and sodium appetite

Regulation of cellular water. ADH = antidiuretic hormone.

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from article Thirst and sodium appetite

Hypovolemic thirst and sodium appetite are caused by altered sensory information from an underfilled circulation, reinforced by increases in circulating angiotensin II and mineralocorticoids. Angiotensin peptides generated from components of a…

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from article Environmental management

Environmental management seeks to provide solutions to the practical problems that humans encounter or create, including the production of garbage and waste. (Credit: Walter Zerla/Getty Images)

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from article Environmental management

Without proper environmental management, economic and industrial development often lead to environmental pollution, especially in urban environments. (Credit: Simon Alvinge/123RF)

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from article Chlorophyceae

Chlorococcales. (a) Chlorococcum (Chlorococcaceae), vegetative cell; (b) cell with zoospores; (c) zoospores; (d) Hydrodictyon (Hydrodictyaceae), portion of coenobium; (e) portion enlarged; (f) Dictyosphaerium (Dictyosphaeriaceae), colony in…

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from article Chlorophyceae

Filamentous green algae with chlorophycean ultrastructure. (a) Microspora (Microsporales), showing H-shaped wall segments; (b) Sphaeroplea (Sphaeropleales); (c) Chaetophora (Chaetophorales), heterotrichous thallus (erect and prostrate systems).

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from article Chlorophyceae

Ulothrix (Ulotrichales).

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from article Chicxulub impact crater

Bouguer gravity anomaly map over the Chicxulub impact crater. The coastline is designated by a thin white line, cenotes (natural pits) and sinkholes are designated by black dots, and the city of Mérida and the town of Chicxulub Puerto are designated…

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from article Chicxulub impact crater

Seismic line imaging of what lies beneath the seafloor, showing the Chicxulub impact crater. The crater includes many faults that can be grouped into an exterior ring fault, a series of outer ring faults, and a series of inner ring faults. Within…

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from article Osage orange

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from article Bryopsidales

Anatomical structures of selected members of Bryopsidales. (a) Dichotomosiphon, filament with oogonia and antheridia. (b) Ostreobium, filaments. (c) Caulerpa, section of filament showing trabeculae. (d) Codium, group of utricles with gametangia and…

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from article Bryopsidales

Representative members of Bryopsidales. (a) Bryopsis; (b) Caulerpa; (c) Penicillus; (d) Halimeda; (e) Codium.

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from article Marine ecology

Marine ecology investigates the basic structural and functional relationships within and among living populations and their physical–chemical environments in marine ecosystems. In this photograph, a cold water reef in California is host to a…

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from article Marine ecology

The snaking waterways of a mangrove estuary in northwestern Madagascar. (Credit: Michael Fay/Getty Images/National Geographic RF)

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from article Marine ecology

Estuary salt marshes in the Grand Bay National Estuarine Research Reserve, Mississippi. (Credit: P. R. Hoar/National Oceanic and Atmospheric Administration)

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from article Marine ecology

Coral bleaching in the lagoon of Huahine Island, French Polynesia. Coral bleaching is the response of corals to environmental stress in which they eject the single-cell algae that live within the transparent coral tissue, making the white coral…

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from article Magnolia

Flowers and leaves of the southern magnolia (Magnolia grandiflora). (Photo courtesy of Forest and Kim Starr)

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from article Ursa Minor

Modern boundaries of the constellation Ursa Minor, the Little Bear. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension…

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