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from article Regolith
Diagram showing the components of residual regolith.
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Image
from article Galliformes
White-tailed ptarmigan (Lagopus leucurus), Glacier National Park, Montana. (Photo by Gerald and Buff Corsi, copyright © California Academy of Sciences)
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from article Climate history
Plot of the average temperature for the contiguous United States during the month of August from 1895 to 2016. (Credit: NOAA)
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from article Climate history
Global temperature relative to peak Holocene temperature, based on ocean cores. (Credit: NASA)
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from article Echinoida
Tripneustes ventricosus (Lamarck), tropical eastern and western Atlantic, found at depths of 0–55 m (0–180 ft). (From G. Hendler et al., Sea Stars, Sea Urchins and Allies: Echinoderms of Florida and the Caribbean, Smithsonian Press, Washington, DC,…
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from article Echinoida
A pyramid from Aristotle's lantern, showing epiphyses joined and tooth with keel. (After H. L. Hawkins, The lantern and girdle of some Recent and fossil Echinoidea, Philos. Trans. R. Soc. Lond. Ser. B, 223:617–649, 1934)
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from article Echinoida
An ambulacral plate from the test, with the lowest element being the largest. (After T. Mortensen, A monograph of the Echinoidea: Camarodonta, C. A. Reitzel, Copenhagen, 1943)
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from article Heterodonta
Common heterodont bivalves. (Credit: Ronald V. Dimock, Jr.)
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from article Heterodonta
Common heterodont bivalves. (Credit: Ronald V. Dimock, Jr.)
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from article Restoration ecology
Restored sand dune habitat at Cape Canaveral, Florida. To help prevent erosion, 180,000 shrubs, including grasses, sunflowers, vines, sea grapes, and saw palmettos, were planted. (Credit: Dan Casper/National Aeronautics and Space Administration)
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from article Weathering processes
Exchange-energy relationships between a rootlet and three minerals. (a) A potassium-bearing, primary silicate mineral. (b) A clay mineral well stocked with exchangeable metal cations. (c) A clay mineral scantily stocked with metal cations. The…
Image
from article Weathering processes
Comparison of binding energy (calories per gram-equivalent weight) on nutrient metal cation (indicated by M) by rocks and soil minerals with exchange binding energy on cation by plant roots. The relation of plant nutrition to weathering and…
Image
from article Prehnite
Prehnite in reniform aggregates, Paterson, New Jersey. (Specimen from Department of Geology, Bryn Mawr College)
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from article Euryalida
Aboral body of a basket star, Euryale aspera (family Euryalidae, order Euryalida), clinging to a red soft coral colony and spreading its branching arms.
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from article Euryalida
A snake star, Astrochele pacifica (family Gorgonocephalidae, order Euryalida): (a) aboral body; (b) aboral arms; and (c) a scanning electron microscope (SEM) image of a separated microscopic hook. (Credit for photo a: Shimoda Marine Research Center,…
Image
from article Cordaitales
Cross sections of cordaitean stems, with simple wood. Left, Cordaixylon iowensis, with septate pith. Right, Mesoxylon priapi, with solid pith. (Photographs by M. L. Trivett)
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from article Cordaitales
Shoot of Cordaixylon dumusum illustrating strap leaves and nonaxillary Cordaitanthus-type cones. (Courtesy of G. W. Rothwell)
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from article Cordaitales
Compound Gothania-type cone of Mesoxylon priapi with bracts subtending secondary shoots. (Courtesy of M. L. Trivett)
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from article Biological productivity
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from article Pinnipeds
Walrus (Odobenus rosmarus). (Credit: Donna Dewhurst Collection/U.S. Fish and Wildlife Service)
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from article Pinnipeds
Steller sea lion and pup (Eumetopias jubatus). (Credit: Alaska Image Library/U.S. Fish and Wildlife Service)
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from article Pinnipeds
Evolutionary relationships and stratigraphic ranges of major groups of pinnipeds. Shaded bars correspond to known ranges, and white bars correspond to inferred ranges. Ma = million years ago. (Copyright © McGraw-Hill Education)
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from article Eocrinoidea
Reconstructions of Cambrian and Ordovician eocrinoids. (a) Gogia spiralis, from the Middle Cambrian of Utah, showing the primitive holdfast; sutural pores between the numerous thecal plates; and long, spiraled brachioles attached to the summit…
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from article Air armament
Air Superiority Missile Concept.
Image
from article Air armament
Low-Cost Autonomous Attack System (LOCAAS; formerly Low-Cost Antiarmor Submunition). (a) Autonomous submunition, with length of 30 in. (0.75 m), wingspan of 40 in. (1.0 m), and weight of 90–100 lb (40–45 kg). (b) Various warhead modes.
Image
from article Conulariida
Conulariid morphology. (a) Paraconularia byblis, a well-preserved specimen in siderite (iron carbonate) from the Carboniferous (Mississippian) of Ohio showing two adjacent sides meeting at a deep corner groove (arrow). Ridges along each side meet at…
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from article Conulariida
Conulariid paleoecology and taphonomy. (a) Cluster of Conularia congregata compacted in shale from the Devonian of New York. The specimens show apical walls (lower arrow), indicating detachment from, or nonpreservation of, their attachment stalks.…
Image
from article Ankerite
Ankerite. (a) Specimen of the mineral (specimen from Department of Geology, Bryn Mawr College). (b) Crystal habits (after C. Klein, Manual of Mineralogy, 21st ed., John Wiley & Sons, Inc., 1993).
Image
from article Cicada
Brood IX periodical cicada in Athens, West Virginia. (Photo by Louie H. Yang)
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from article Cicada
Periodical cicada life cycle. Counterclockwise from lower left: Nymphal cicada feeding on plant roots belowground; ants and other detrivores feeding on dead cicada litterfall; teneral adult cicada recently emerged from the nymphal exuviae; bird…
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from article Cicada
Brood X periodical cicadas in Boyce, Virginia. (Photo by Louie H. Yang)
Image
from article Lava
Examples of lava. (a) Pahoehoe lava (in Kilauea, Hawaii) has a smooth and wavy surface formed by a thin layer of cooler lava at the surface. The surface layer is pushed into folds from the faster-moving, hot fluid lava beneath (photograph by J. D.…
Image
from article Tektite
Dumbbell-shaped tektite (irgizite) from the Zhamanshin meteoritic impact crater, Northern Aral Region, Russia. The glass is so dark brown that it appears black in reflected light.
Image
from article Pteridosperms
Suggested reconstruction of Callistophyton. (After G. W. Rothwell, The Callistophytaceae (Pteridospermopsida): I. Vegetative structures, Palaeontographica, 151B:171–196, 1975)
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from article Pteridosperms
Transverse section of Stenomyelon. (From C. B. Beck, The appearance of gymnosperm structure, Biol. Rev., 45:379–400, 1970)
Image
from article Reproductive behavior
The mating of dragonflies encompasses a number of reproductive behaviors. Typically, the male is in front and the female is behind. If the female is willing to mate, she bends her abdomen forward to collect sperm from the male's accessory genitalia,…
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from article Reproductive behavior
Sage-grouse lek. Males stake out and defend territories on a traditional breeding ground. Females breed with males in selected territories. (Credit: U.S. Fish and Wildlife Service)
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from article Reproductive behavior
Two bull northern elephant seals fighting for dominance on the beach. (Credit: eoind/Getty Images)
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from article Reproductive behavior
Natterjack toad giving a mating call with its vocal sac expanded. (Credit: Bobby Bok)
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from article Reproductive behavior
Mating behavior of sticklebacks: (a) zigzag dance of a male, which leads a female to the nest; (b) the male stimulates the female in the nest to lay eggs; (c) schematic portrayal of the events in a courtship sequence. (Credit: Based on original…
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from article Reproductive behavior
Lordosis in a female rodent. When mounted, the females of many mammalian species adopt the lordotic posture, rendering copulation possible. Note the concave arching of the spine. (Credit: Based on an original drawing by L. C. Drickamer and S. H.…
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from article Reproductive behavior
A black-browed albatross feeding a chick. This is one example in which parental care may be extensive and prolonged. (Credit: Vetta/Getty Images)
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from article Craniiformea
Isocrania egnabergensis (Retzius): (a) dorsal valve interior; (b) dorsal valve exterior; (c) ventral valve interior; (d) ventral valve exterior; (e) complete shell, lateral view, dorsal valve above; 8 mm (0.32 in.) in width. Danocrania tuberculata…
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from article Craniiformea
Muscle system of Novocrania viewed (top) dorsally and (bottom) laterally. (Adapted from O. M. B. Bulman, Muscle systems of some inarticulate brachiopods, Geol. Mag., 76:434–444, 1939; after R. L. Kaesler, ed., Treatise on Invertebrate Paleontology,…
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from article Deep-marine sediments
Bathymetric display of the northern Gulf of Mexico based on high-resolution bathymetric swath data. The data are displayed to give a 3-D perspective of present-day shelf, slope, and basin settings. Note the highly irregular sea-floor topography and…
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from article Deep-marine sediments
Map showing long-distance transport of modern slides of about 300 km (186 mi) downslope from the shelf edge (100-fathom, 183-m, or 600-ft contour line) off northwestern Africa. Thickness of slide = 25 m (82 ft). (From R. D. Jacobi, Sediment slides…
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from article Deep-marine sediments
Conceptual model showing interaction between channelized (axial) turbidity currents, overbank turbidity currents, and bottom currents (contour currents) in deep-sea environments. (From G. Shanmugam, T. D. Spalding, and D. H. Rofheart, Process…
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from article Deep-marine sediments
Amazon Fan. (a) Channel bifurcation through avulsion on the deep-sea Amazon Fan results in unchannelized sandy flows by breaching their confining levee through a crevasse and spreading out initially as unchannelized flows into a lower interchannel…
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from article Deep-marine sediments
Sizes of modern abyssal plains. (From P. P. E. Weaver, J. Thomson, and P. M. Hunter, Introduction, in P. P. E. Weaver and J. Thomson (eds.), Geology and Geochemistry of Abyssal Plains, Geol. Soc. London Spec. Publ., no. 31, pp. vii–xii, 1987)
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from article Deep-marine sediments
GLORIA long-range side-scan sonar imagery showing fingerlike patterns of debris flows in the Bear Island Fan on the continental margin of the modern Norwegian-Barents Sea. These fans are composed of cohesive debris flows. Properties of the Bear…
