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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 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 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 Telemetering
Functions of a generic aerospace telemetry system.
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from article Telemetering
Functions of a supervisory control and data acquisition (SCADA) system.
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from article Telemetering
Functions of a spacecraft telemetry and command system, using packet telemetry.
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from article Kumquat
Fruits and foliage of the Nagami kumquat (Fortunella margarita). (Photo by Forest and Kim Starr)
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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 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…
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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 Marjoram
Close-up view of marjoram (Majorana hortensis; alternatively Origanum majorana). (Photo courtesy of Forest and Kim Starr)
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from article Prehistoric technology
Elements of stone flaking. (a) Relationship between the core and the flake. (b) Major feature of the ventral or release surface of the flake. (After I. Tattersall, E. Delson, and J. A. Van Couvering, eds., Encyclopedia of Human Evolution and…
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from article Prehistoric technology
Principal techniques of stone-tool manufacture. (a) Hard-hammer, with free-hand percussion. (b) Anvil technique. (c) Bipolar technique. (d) Soft-hammer percussion. (e) Indirect percussion or punch technique. (f) Pressure flaking. (After…
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from article Prehistoric technology
Potters from the village of Harappa, Pakistan, display their wares in front of a replica of a two-chambered kiln used by ancient potters in the Indus Valley civilization. (Photo courtesy of R. P. Wright)
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from article Cellular automata
Cellular automata connections: (a) linear, (b) orthogonal, and (c) full.
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from article Cellular automata
Cellular automata in action.
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from article Devonian
Devonian, the fourth period of the Paleozoic Era.
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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…
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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 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 Malvales
A blooming hibiscus flower (genus Hibiscus, family Malvaceae, order Malvales). (Credit: Howard F. Schwartz/Colorado State University)
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from article Obolellida
Obolella. (a) Shell exterior (after J. Hall and J. M. Clarke, An introduction to the study of the Brachiopoda intended as a handbook for the use of students, Report of the N.Y. State Geologist for 1891, 1894). (b) Dorsal valve interior, and (c)…
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from article Caraway
Caraway (Carum carvi) fruits (often called “seeds”). Scale bar = 1 mm. (Photo by Steve Hurst; USDA–NRCS PLANTS Database)
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from article Enantiornithes
Protopteryx, the most primitive known enantiornithine bird, collected from the Early Cretaceous of Hebei Province, northern China.
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from article Dallis grass
Dallis grass (Paspalum dilatatum). (Photo courtesy of Larry Allain, USGS National Wetlands Research Center)
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from article Carnauba wax
Carnauba wax palm (Copernicia prunifera). The leaves of this palm are the source of carnauba wax. (Photo courtesy of Scott Zona)
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from article Information management
Information concept in a word tag cloud managed in the context of big data. (Credit: Shutterstock/Rafal Olechowski)
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from article Videotelephony
Video telephone call using a tablet computer. (Courtesy of Fotolia, https://us.fotolia.com)
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from article Mollusca
Higgins eye pearly mussels (Lampsilis higginsii). (Credit: U.S. Fish and Wildlife Service)
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from article Mollusca
Snails are assigned to the class Gastropoda in the phylum Mollusca. (Credit: Zuzha/Shutterstock)
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from article Mollusca
Generalized model of a stem mollusk (or archetype) in side view. There are three distinct regions in the molluscan body: head-foot, visceral mass, and mantle-shell. Water circulation through the mantle cavity, gills (ctenidia), and pallial complex…
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from article Mollusca
Arrangement of the mantle and shell layers in mollusks. The fleshy mantle margin is divided into three lobes, and the outer pallial lobe is largely responsible for secretion of the three layers of the shell. (Credit: W. D. Russell-Hunter)
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from article Mollusca
Aspidobranch ctenidium (feather or plume gill) as found in primitive gastropods and other molluscan groups. (a) Stereogram showing the water current from the ventral inhalant to the dorsal exhalant between adjacent gill plates; this current is…
Image
from article Mollusca
Common octopus (Octopus vulgaris). (Credit: Aerial-motion/Shutterstock)
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from article Frequency modulation
Examples of modulating signals and corresponding frequency-modulated waveforms. (a) Ramp modulating signal. (b) Periodic modulating signal.
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from article Frequency modulation
Example of direct method of frequency modulation.
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from article Frequency modulation
Example of indirect method of frequency modulation.
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from article Paleoecology
Zonation of Silurian (425 million year old) marine communities in the Welsh Basin, United Kingdom. Marine animal communities were typically arranged in belts parallel to the shoreline and related to water depth. A classic study using fossil…
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from article Paleoecology
Classification of shales in terms of percentages of three benthic habitat groups: epifaunal suspension-feeding bivalves (those living at the sediment-water interface and filtering seawater), infaunal (living within and feeding on the sediment), and…
Image
from article Paleoecology
Comparison of four developmental stages in four ancient reef masses. (After K. R. Walker and L. P. Alberstadt, Ecological succession as an aspect of structure in fossil communities, Paleobiology, 3:238–257, 1975)
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from article Paleoecology
Formation and burial sequence of Bobcaygeon hardground. (a) Soft-bottom community of strophomenid brachiopods and infaunal burrowers inhabiting carbonate mud. (b) Hardground community consisting of boring and encrusting organisms. (c)…
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from article Paleoecology
Tiering or vertical depth stratification in marine communities through time. Note the rapid rise of the highest-tier (level) organisms (crinoids or sea lilies, bryozoans) from a few centimeters to over a meter above the sea floor during the…
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from article Paleoecology
The three great marine evolutionary faunas of the Phanerozoic. The Cambrian fauna, composed of trilobites, primitive groups of brachiopods, and mollusks, arose early during that period to a diversity of about 50 families, and then dwindled during…
Image
from article Plant development
Stages of plant development for a daisy (genus Gerbera) showing the progression from a seedling to a blooming plant. (Credit: Hue Photography/Getty Images)
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from article Plant development
The aboveground body of the plant (shoot) comprises a stack of plant segments termed phytomers. Phytomers consist of a leaflike lateral organ (attached to the stem at a node), a stem (internode), and a lateral meristem or bud. All cells that are…
Image
from article Plant development
The root (a, b) is built by files of cells and contains three distinct zones of maturation (c). In contrast, the shoot apical meristem (d, e) gives rise to all aboveground plant tissues and comprises zones of cells. The central zone (CZ) maintains…
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from article Plant development
Much of plant morphological diversity can be explained by variations in (a) branching order/pattern, (b) phyllotaxy, and/or (c) leaf shape. (Copyright © McGraw-Hill Education)
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from article Plant development
The ABCE model for floral development. (a) Plants can regulate which type of floral organ is produced in each whorl by restricting the expression pattern of ABCE transcription factors. (b) The four whorls of the flower are shown (stamen, sepal,…
Image
from article Bromegrass
Smooth bromegrass (Bromus inermis). (Photo by Roselyn Heil, Yellowstone National Park, National Park Service)
Image
from article Quaternary
Quaternary, the second period of the of the Cenozoic Era.
Image
from article Pith
Shoot apex of Coleus blumei, longitudinal section. (After R. A. Popham, Laboratory Manual for Plant Anatomy, C. V. Mosby, 1966)
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from article Pith
Various types of pith in branchlets. (a) Continuous. (b) Diaphragmed. (c) Chambered. (After E. L. Core, Plant Taxonomy, Prentice-Hall, 1955)
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from article Secretory structures (plant)
Petunia. (a) Young leaf covered with glandular hairs. (b) Higher magnification of the hairs.
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from article Secretory structures (plant)
Hair of stinging nettle.
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from article Secretory structures (plant)
Ceanothus. (a) Longitudinal section of flower. The nectary is ringlike and surrounds the ovary. (b) Enlarged view of a section of the nectary. The epidermis and the small cells beneath it are secretory.
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from article Secretory structures (plant)
Resin duct from pinewood in (a) transverse section and (b) longitudinal section.
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from article Secretory structures (plant)
Laticifers of Nerium oleander. (a) Longitudinal section of shoot tip. The wavy solid lines represent parts of laticiferous cells, which are arranged irregularly. (b) Enlarged view of the area in the rectangle in a showing parts of laticifers with…
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from article Placodermi
Two cladograms portraying differing concepts of relationships of orders of placoderms: (a) according to Denison (after R. H. Denison, Placodermi, vol. 2 of O. Kuhn and H. P. Schultz, eds., Handbook of Palaeoichthyology, 1978); and (b) according to…
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from article Placodermi
Stensioella heintzi in dorsal view; length about 10 in. (25 cm).
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from article Placodermi
Pseudopetalichthys problematica, ventral view; length about 6 in. (15 cm).
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from article Placodermi
Gemuendina stuertzi from the Lower Devonian of Germany; restoration in dorsal aspect.
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from article Placodermi
Rhamphodopsis threiplandi from the Middle Devonian of Scotland. Restoration of skeleton with outline of body in lateral aspect.
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from article Placodermi
Romundina stellina, head and shoulder girdle in lateral view; length about 1.2 in. (3 cm).
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from article Placodermi
Lunaspis broilii from the Lower Devonian of Germany; restoration in dorsal aspect.
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from article Placodermi
Phyllolepis orvini from the Upper Devonian of Greenland. The restoration of the dermal armor is shown in dorsal aspect. The outline of the front of the head and the body is hypothetical, but shows how the fish might have appeared in life.
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from article Placodermi
Representative arthrodires. (a) Cranial and thoracic shields of giant Upper Devonian Dunkelosteus (Dinichthys), a brachythoracic arthrodire showing reduction of thoracic shield, large nuchal gap, and elevated cranio-thoracic joint. Length of…
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from article Placodermi
Pterichthyodes (Ptericthys), a Middle Devonian antiarch. (a) Lateral view showing scale-covered tail; about 15 cm (6 in.) in length. (b) Dorsal and (c) ventral views of the armor. (After Traquair)
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from article Mycology
Amanita muscaria (fly agaric or fly amanita) is a toxic mushroom with hallucinogenic properties. (Credit: Ondrej83/Shutterstock)
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from article Phanerozoic
Phanerozoic, the present geologic eon representing the past half-billion years.
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from article Phanerozoic
Geologic time scale showing the eons, eras and periods of the Phanerozoic; epochs of the Cenozoic Era; and major events in the history of life. Geologic ages are given in millions of years ago (Ma). The beginning of the Archean Eon is undefined at…
Image
from article Corn
Corn (Zea mays) growing in a field. (Credit: Bob Nichols, Agricultural Research Service/U.S. Department of Agriculture)
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from article Corn
Ear of field corn on a stalk. The husk has been peeled back to display the kernels (seeds). (Credit: Howard F. Schwartz, Colorado State University)
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from article Corn
The corn leaf at the top is more resistant against leaf blight than the severely damaged leaf on the bottom. (Credit: Keith Weller, Agricultural Research Service/U.S. Department of Agriculture)
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from article Corn
Gall of corn smut, caused by Ustilago maydis, on a stalk of corn. (Credit: H. J. Larsen)
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from article Corn
White ear rot and seedling blight on a corn ear. The pathogen responsible for the afflicted corn is Stenocarpella maydis. (Credit: U.S. Department of Agriculture Cooperative Extension Slide Series/Clemson University)
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from article Fennel
Fennel (Foeniculum vulgare). (Photo courtesy of Forest and Kim Starr)
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from article Reptilia
Desert tortoise (Gopherus agassizii). (Credit: Robb Hannawacker/National Park Service)
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from article Reptilia
Western or variable ground snake (Sonora semiannulata). (Credit: Peter Paplanus)
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from article Reptilia
Greater short-horned lizard (Phrynosoma hernandesi). (Credit: Lake Mead National Recreation Area, Arizona–Nevada/National Park Service)
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from article Archaeopteryx
Cast of the Archaeopteryx fossil specimen located at the Berlin Natural History Museum. Notable features of this fossil bird include spread-out wings and long clawed fingers. (Copyright © Natural History Museum, London)
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from article Calcarea
A calcareous sponge belonging to the family Leucettidae (order Clathrinida). (Credit: Bernard Dupont)
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from article Calcarea
Grades of construction of the water-current system in Calcarea: (a) asconoid type; (b) syconoid type without cortex; (c) syconoid type with cortex; (d) intermediate or transitional stage between syconoid and leuconoid types; (e) leuconoid type.…
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from article Calcarea
Spicule formation in the calcareous sponges: (a, b, c) early stages in secretion of the triactine spicule; (d) late stage of spicule formation. (Copyright © McGraw-Hill Education)
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from article Squash
Crookneck squash (Cucurbita moschata). (Credit: Howard F. Schwartz, Colorado State University/www.Bugwood.org)
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from article Squash
Delicata squash (Cucurbita pepo), a variety of winter squash. (Credit: Shaun Case)
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from article Squash
Leaves of Cucurbita pepo infected by a squash mosaic virus. (Credit: William M. Brown, Jr./www.Bugwood.org)
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from article Programmable controller
Functional architecture of a typical high-performance single-chip microcontroller used for control and signal processing. (National Semiconductor Corp.)
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from article Llama
The llama (Lama glama) of South America. (Copyright © McGraw Hill)
