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from article Wool
Sheep at a research facility near Dubois, Idaho. (Photo courtesy of the Agricultural Research Service, U.S. Department of Agriculture)
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Image
from article Wool
Longitudinal section of a completely developed nonmedullated wool follicle, including sebaceous and sweat glands.
Image
from article Wool
Cuticle, cortex, and medulla of a wool fiber.
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from article Wool
Scale formation of Delaine Merino wool fibers.
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from article Wool
Fine wool staples showing distinct crimp (wavy) patterns. The length shown is the minimum for each classification.
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from article Brazil nut
Unshelled Brazil nuts (Bertholletia excelsa). (Photo courtesy of C. E. Timothy Paine)
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from article Anostraca
Branchinecta paludosa, male, small specimen, lateral aspect.
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from article Cerargyrite
Cerargyrite crystals from Leadville, Colorado. (Specimen from Department of Geology, Bryn Mawr College)
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from article Staining
Photomicrograph of Mycobacterium tuberculosis (the causative agent of tuberculosis) using the acid-fast Ziehl-Neelsen carbol fuchsin stain. In this case, the M. tuberculosis bacteria stain red (or reddish purple), whereas non-acid-fast species stain…
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from article Staining
Staining of Klebsiella bacteria using crystal violet. (Credit: Lisa Burgess/McGraw-Hill Education)
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from article Staining
Photomicrograph of a Gram-stained urethral exudate sample from a male who presented with a case of urethritis. Numerous extracellular Gram-negative Neisseria gonorrhoeae bacteria are evident. (Credit: Norman Jacobs/U.S. Centers for Disease Control…
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from article Vitamin A
Summary scheme depicting the dietary uptake, metabolism, and actions of vitamin A within the body. All vitamin A must be obtained from the diet as either preformed vitamin A (primarily as retinol and retinyl esters) or provitamin A carotenoid (such…
Image
from article Castor plant
Seeds of the castor plant (Ricinus communis). These seeds, which are also known as castor beans, are processed to make castor oil. (Credit: Brian Prechtel/Agricultural Research Service, United States Department of Agriculture)
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from article Bone disorders
A colored x-ray of the hand of a patient with severe rheumatoid arthritis in all of the fingers. (Credit: Science Photo Library/Alamy Stock Photo)
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from article Bone disorders
A colored X-ray of a linear displacement fracture of an ulna (forearm bone) of a man. (Credit: Puwadol Jaturawutthichai/Shutterstock)
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from article Bone disorders
Comparison of a healthy normal bone (left) and a bone with osteoporosis (right). Osteoporosis leads to a decrease in bone mass and density, causing bones to become weak and brittle. (Credit: Stocktrek Images/Alamy Stock Photo)
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from article Cowpea
Cowpea (Vigna unguiculata): pods and leaves. (Photo by Howard F. Schwartz, Colorado State University)
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from article Cowpea
Cowpea seeds, which are often called black-eyed peas. (Photo by Joseph Berger; Bugwood.org)
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from article Salmon farming
Adult Atlantic salmon (Salmo salar). (Credit: William Hartley/U.S. Fish and Wildlife Service)
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from article Salmon farming
Atlantic salmon (Salmo salar) at a pre-smolt stage. (Credit: Edward Peter Steenstra/U.S. Fish and Wildlife Service)
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from article Salmon farming
A congregation of coho salmon (Oncorhynchus kisutch) released from a hatchery. Investigators continue to study the effects of farmed fish on neighboring populations of wild salmonids. (Credit: Salmon Ecology Team/Southwest Fisheries Science Center,…
Image
from article Granulite
Southern part of peninsular India and Sri Lanka, showing broad tectonic and metamorphic features. (After A. P. Subramaniam, Charnockites and granulites of southern India: A review, Dan. Geol. Foren., 17:473–493, 1967)
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from article Suctoria
Endogenous budding in the suctorian Podophrya, a species which measures 10–28 μm.
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from article Kumquat
Fruits and foliage of the Nagami kumquat (Fortunella margarita). (Photo by Forest and Kim Starr)
Image
from article Titan
Natural color view of Titan at left. The false-color view at right incorporates infrared light in place of red light, revealing surface details and clouds. Both images obtained by the Cassini orbiter. (Credit: NASA/JPL-Caltech/Space Science…
Image
from article Titan
Images of Titan taken by Cassini's visual and infrared mapping spectrometer, penetrating through the moon's hazy atmosphere. The flyby dates are as follows: October 28, 2005 (left), December 26, 2005 (middle), and January 15, 2006 (right). A notable…
Image
from article Titan
Physical structures of the atmospheres of Titan and Earth. The vertical axis is logarithmic pressure. The two atmospheres appear similar, except offset in temperature. Also marked are the corresponding altitude levels in each atmosphere, showing…
Image
from article Titan
Map of Titan, with names indicated for many major regions, compiled through mapping by Cassini as of June 2015. (Credit: NASA/JPL-Caltech/Space Science Institute/USGS)
Image
from article Titan
Huygens probe descent mosaic of three images, about 7 km (4.3 mi) across, showing a high ridge area and river channel flows. (Credit: ESA/NASA/JPL/University of Arizona)
Image
from article Titan
Side-looking image acquired by the Huygens probe after impact on Titan's surface, showing rounded cobbles between about 5 and 15 cm (2 and 6 in.) across. (Credit: NASA/JPL/ESA/University of Arizona)
Image
from article Titan
Synthetic aperture radar from Cassini of Ligeia Mare, the second largest body of liquid on Saturn's moon Titan. It is comparable in size to Lake Superior. The methane-dominated maria is rendered black, with Titan's surrounding land rendered yellow…
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from article Titan
Map of Titan's mountain chains compiled by Cassini, with officially named peaks indicated. The mountains are named after mountains appearing in the fictional works of J.R.R. Tolkien, such as The Lord of the Rings. (Credit NASA/JPL-Caltech/University…
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from article Melilite
Melilite crystals from Vesuvius, Italy. (Specimen from Department of Geology, Bryn Mawr College)
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from article Mulberry
White mulberry (Morus alba). (Photo courtesy of Forest and Kim Starr)
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from article Jawless vertebrate
Interrelationships of jawless and jawed vertebrates, showing the distribution of some major evolutionary steps. (Copyright © McGraw Hill)
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from article Beech
Leaf on top of bark of American beech (Fagus grandifolia). (Photo courtesy of Robert H. Mohlenbrock, USDA–NRCS PLANTS Database)
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from article Beech
Beechnuts of the American beech (Fagus grandifolia). (Photo courtesy of Steve Hurst, USDA–NRCS PLANTS Database)
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from article Organoid
Generation of an organoid and some of its therapeutic potential. To date, organoids can be derived from patient-derived induced pluripotent stem cells (iPSCs). Like organogenesis in vivo, organoids self-organize through cell differentiation, cell…
Image
from article Organoid
A flowchart outlining the basic steps to create a cerebral organoid. The process takes a span of months, and the size of the organoid is limited by the availability of nutrients.
Image
from article Psocoptera
Valenzuela flavidus, male (family Caeciliusidae): habitus (general appearance). Body length: 2.02 mm (0.08 in.).
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from article Psocoptera
Metylophorus novaescotiae, female (family Psocidae): habitus. Body length: 5.24 mm (0.2 in.).
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from article Psocoptera
(a–e) Mouthparts of a typical psocid, Echmepteryx hageni (family Lepidopsocidae): a = labrum, b = maxilla (l = lacinia), c = hypopharynx (li = lingual sclerite), d = mandible, e = labium. Scale: 0.1 mm (0.004 in.). (f) Wing venation of a typical…
Image
from article Psocoptera
Liposcelis brunnea, female (family Liposcelididae): habitus of a cleared specimen. Body length: 1.1 mm (0.043 in.).
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from article Urine
Overview of the human urinary system. Urine production takes place in the kidneys. Ureters transport urine to the urinary bladder, where the urine is stored. Urine passes to the outside via the urethra. (Copyright © McGraw Hill)
Image
from article Sun
The Sun rising over Bloomingdale, Illinois. (Credit: Jonathan Kriz/Flickr)
Image
from article Sun
An artist's impression of a young Sun-like star surrounded by a planet-forming disk of material. (Credit: NASA/JPL-Caltech)
Image
from article Sun
Map of the differential rotation of the Sun, determined from helioseismology. The poles rotate slowly and the equator much faster, but the center of the Sun, below the convective zone, rotates as a rigid body. (Credit: K. G. Libbrecht and M. F.…
Image
from article Sun
The diamond-ring effect surrounded along the limb of the Moon by the pinkish chromosphere and the pinkish prominences on either side, viewed at the Easter Island total solar eclipse of 2010. The inner corona is also visible outside the silhouette of…
Image
from article Sun
Photospheric granulation in white light taken with the Swedish 1-m Solar Telescope (SST), located on the island of La Palma and operated by the Institute for Solar Physics in the Spanish Observatorio del Roque de los Muchachos of the Instituto de…
Image
from article Sun
Sunspot numbers from about 1700 to early 2018. (Credit: SILSO data/image, Royal Observatory of Belgium, Brussels)
Image
from article Sun
A symmetric sunspot with its dark umbra and lighter fibrils of its penumbra, on a background of solar granulation. Bright filigree is seen threading its way through some of the dark lanes between granules. The umbra and penumbra together are about…
Image
from article Sun
Image of the Sun in hydrogen-alpha (Hα) light. As the dark filament at upper left on the disk goes over the limb, it becomes visible as a prominence seen against the sky. The Sun rotates from left to right in this picture. A sunspot is visible in…
Image
from article Sun
Large prominence in its eruptive phase after days or weeks of static inactivity, seen through a filter that passed only the 30.4-nm radiation of helium with the Atmospheric Imaging Assembly of NASA's Solar Dynamics Observatory (SDO). The horizontal…
Image
from article Sun
A solar flare is seen as a bright flash at the Sun's right in this ultraviolet image NASA's Solar Dynamics Observatory, recorded on Sept. 10, 2017. (Credit: NASA/SDO/Goddard)
Image
from article Sun
Composite image of a two-ribbon flare and a cross section of a coronal mass ejection (CME) as observed by the SOHO spacecraft (the CME image is offset from the flare image for clarity). The diagram depicts the inferred magnetic field structure…
Image
from article Sun
Total solar eclipses in the period 2010–2060, including some that are hybrid in that the beginnings and ends are annular. (Credit: Michael Zeiler, eclipse-maps.com, with eclipse paths from Xavier Jubier, [email protected])
Image
from article Oil sand
Tar sand deposits in Alberta. 1 mi = 1.6 km.
Image
from article Lightning
Charge distribution in storm clouds. (Credit: NOAA)
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from article Lightning
Natural cloud-to-ground lightning near Tucson, Arizona. Note that each discharge strikes the ground in more than one place. (Credit: Michael J. Leuthold)
Image
from article Lightning
Sprites, elves, and blue jets are transient luminous events in the upper atmosphere associated with thunderstorms. (Credit: NOAA)
Image
from article Marjoram
Close-up view of marjoram (Majorana hortensis; alternatively Origanum majorana). (Photo courtesy of Forest and Kim Starr)
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from article Stress (psychology)
Dimensions of stressful experiences. (Credit: National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health)
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from article Stress (psychology)
Diagram of the hypothalamic-pituitary-adrenal axis. The thicker arrow indicates that the feedback of glucocorticoids on ACTH is most potent. Abbreviations: ACTH, adrenocorticotropic hormone; CRH, corticotropin-releasing hormone. (Copyright ©…
Image
from article Tooth
Stages in the development of a tooth.
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from article Tooth
Schema showing tooth replacement in lower vertebrates. (a, b) Horizontal lines represent the strand of tissue which connects the tooth germs in most vertebrates; vertical lines indicate the distance from the tooth germs to the surface of the jaw. In…
Image
from article Psittaciformes
Sulphur-crested cockatoo (Cacatua galerita). (Photo by Lloyd Glenn Ingles; copyright © California Academy of Sciences)
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from article Strigiformes
Northern spotted owl. (Photo by John and Karen Hollingsworth/U.S. Fish and Wildlife Service)
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from article Sloth
Pale-throated three-toed tree sloth (Bradypus tridactylus). (Credit: Lloyd Glenn Ingles; copyright © California Academy of Sciences)
Image
from article Chameleon
A short-horned chameleon (Calumma brevicorne, family Chamaeleonidae), which is a representative species found in Madagascar. (Credit: Gerald and Buff Corsi; copyright © California Academy of Sciences)
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from article Bioterrorism
Civilians are the prime targets in bioterrorist attacks. During World War II, gas masks with filters were distributed to British civilians because of fears of a chemical agent attack. (Credit: Ingram Publishing/SuperStock)
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from article Bioterrorism
A color-enhanced scanning electron micrograph (SEM) showing splenic tissue from a monkey with inhalation anthrax. Rod-shaped bacilli of Bacillus anthracis (yellow) and an erythrocyte (red) are shown. (Credit: Arthur Friedlander/National Institute of…
Image
from article Infarction
Magnified gross photograph of a wedge-shaped infarct of kidney (I). Renal cortex (C), medullary pyramid (M), and renal pelvis (P) can be seen.
Image
from article Infarction
Gross photograph of a brain section, showing a wedge-shaped infarct (I) that resulted from a thrombus. Secondary hemorrhage has occurred.
Image
from article Stichosomida
Anterior end of Trichinella spiralis showing stichosome. (Adapted from B. G. Chitwood, 1930)
Image
from article Stichosomida
Portion of the stichosome of the whipworm, Trichuris trichiura. (Photomicrograph by Sung-Jong Hong, The Korean Society for Parasitology)
Image
from article Devonian
Devonian, the fourth period of the Paleozoic Era.
Image
from article Devonian
Biostratigraphic zones based on conodonts (left) plotted to show approximate correspondence to the chronostratigraphic stages and series which compose the Devonian System (right) and relative sea-level changes (center) showing major fluctuations…
Image
from article Devonian
Reconstruction of Middle Devonian continental positions based on distribution of lithologic climatic indicators. Probable ocean currents derived from this paleogeography explain the biogeographic realms. Kolyma and Tarim are microcontinents of the…
Image
from article Smog
Smog, Downtown Los Angeles, California, USA. (Credit: Yenwen Lu/Getty Images)
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from article Smog
Average background concentration of ozone in the atmosphere as a function of altitude. Note the enhancement of O3 near the Earth's surface that can occur in polluted areas as a result of photochemical smog.
Image
from article Centrohelida
Centrohelida. (a) Raphidiophrys ambigua. (b) Acanthocystis erinaceoides.
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from article Hemiptera
Phylogenetic relationships among the extant Hemiptera groups.
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from article Hemiptera
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from article Hemiptera
Image
from article Hemiptera
Mouthparts and method of feeding of a plant bug.
Image
from article Hemiptera
Plant pests. (a) A colony of aphids on a rose shoot. (b) The citrus mealybug. (Ohio Agricultural Experiment Station)
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from article Hemiptera
An aphid (dorsal aspect).
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from article Hemiptera
Anterior dorsum of various Auchenorrhyncha: (a) cicada; (b) fulgoroid (apical part of antenna omitted); (c) another species of fulgoroid; (d) cercopid; (e) membracid, anterior view of face and pronotum.
Image
from article Hemiptera
Membracids on stems: (a) adult; (b) nymphs. (Courtesy of C. H. Hanson)
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from article Hemiptera
Peloridora kuscheli China (Peloridiidae).
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from article Hemiptera
Triatoma pallidipennis (Reduviidae). (Photo by E. S. Ross)
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from article Hemiptera
External anatomy of a typical bug.
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from article Hemiptera
Squash bug. (Photo by Scott Bauer, Agricultural Research Service, U.S. Department of Agriculture)
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from article Hemiptera
Brown marmorated stink bug (Halyomorpha halys): adult (top) and fifth-instar nymph (bottom). (Photo by Stephen Ausmus, Agricultural Research Service, U.S. Department of Agriculture)
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from article Hemiptera
Oblique-dorsal view of a bedbug, Cimex lectularius. (Photo by Piotr Naskrecki, Public Health Image Library)
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from article Hemiptera
Nymph of the tarnished plant bug (Lygus lineolaris). (Photo by Scott Bauer, Agricultural Research Service, U.S. Department of Agriculture)
Image
from article Chestnut
American chestnut (Castanea dentata). (Photo courtesy of Forest and Kim Starr)
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from article Chestnut
Nuts of the Allegheny chinquapin (Castanea pumila). (Photo courtesy of Steve Hurst, USDA–NRCS PLANTS Database)
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from article Genetic mapping
A genetic map shows the relative locations of genes in a linear arrangement. The map is based on the idea of linkage (that is, the closer that two genes are to each other on the chromosome, the greater is the probability that they will be inherited…
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from article Genetic mapping
The process of genetic mapping involves analyses of how traits and genetic markers segregate in experimental or natural populations to determine whether traits and markers (collectively, loci) are inherited together or independently from one…
