Image
from article Learning
Lateral view of the human brain, including the primary areas of the frontal, temporal, parietal, and occipital lobes. (Copyright © McGraw-Hill Education)
Search Results
Search Results
Refine this search
Search result paging links
1,923 results
Image
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.…
Image
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)
Image
from article Pine nut
Cone containing pine nuts (stone pine, Pinus pinea). (Photo by Vito Buono, Bari, Italy)
Image
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:…
Image
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.…
Image
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,…
Image
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)
Image
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.
Image
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.
Image
from article Pathotoxin
Chemical structures of four pathotoxins. (a) Fusicoccin. (b) Tentoxin. (c) AM-toxin. (d) HMT-toxin.
Image
from article Tree ferns
Cyathea cooperi (Australian tree fern), a common member of the family Cyatheaceae. (Photo by Forest and Kim Starr)
Image
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)
Image
from article Circadian clock (plants)
Three-module circadian clock system.
Image
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…
Image
from article Ecosystem
Levels of organization in ecosystems, which involve both biotic (living) components and abiotic (nonliving, physical) components. (Copyright © McGraw-Hill Education)
Image
from article Ecosystem
General model of energy flow through ecosystems. (Copyright © McGraw-Hill Education)
Image
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…
Image
from article Ecosystem
General model of the nitrogen cycle in ecosystems. (Copyright © McGraw-Hill Education)
Image
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 ©…
Image
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…
Image
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…
Image
from article Biodiversity
Ecosystem function (a) as a positive, linear function of biodiversity and (b) as a nonlinear, satiating function of biodiversity.
Image
from article Gibberellins
ent-Gibberellane carbon skeleton showing the carbon numbering system and ring designations.
Image
from article Gibberellins
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…
Image
from article Gibberellins
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…
Image
from article Gibberellins
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 promotes…
Image
from article Gibberellins
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…
Image
from article Urodela
A typical member of the order Urodela: the longtail salamander (Eurycea longicauda). (Photo by Ryan Hagerty, U.S. Fish and Wildlife Service)
Image
from article Urodela
World distribution of salamanders (order Urodela), indicated by areas of shaded blue color.
Image
from article Urodela
California tiger salamander (Ambystoma californiense). (Photo by John Cleckler, U.S. Fish and Wildlife Service)
Image
from article Urodela
The two-toed amphiuma salamander (Amphiuma means). (Photo courtesy of the Southeast Ecological Center, U.S. Geological Survey, Gainesville, FL)
Image
from article Urodela
The northern red salamander (Pseudotriton ruber ruber). (Photo by Alicia Lafever, U.S. National Park Service)
Image
from article Thirst and sodium appetite
Regulation of cellular water. ADH = antidiuretic hormone.
Image
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…
Image
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)
Image
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)
Image
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…
Image
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).
Image
from article Chlorophyceae
Ulothrix (Ulotrichales).
Image
from article Osage orange
Fruit and foliage of osage orange (Maclura pomifera). (Photo copyright © Karren Wcisel)
Image
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…
Image
from article Bryopsidales
Representative members of Bryopsidales. (a) Bryopsis; (b) Caulerpa; (c) Penicillus; (d) Halimeda; (e) Codium.
Image
from article Marine ecology
Cross-sectional profile of (a) estuarine and nearshore and (b) coastal and open-ocean marine environments. The nearshore region, although not precisely defined, is generally within kilometers of the coastline. 1 m = 3.3 ft.
Image
from article Marine ecology
Salinity structure of the three general types of estuaries found throughout the world. (a) Strongly stratified system due to high surface freshwater inflow. (b) Moderated stratified system showing lines of equal salinity in parts per thousand. (c)…
Image
from article Marine ecology
Photosynthetically active radiation intensity at depth for various values of the attenuation coefficient (k). The intersection of the 1% light level (the limiting light intensity for photosynthesis) with the decay curves marks the depth limit for…
Image
from article Marine ecology
Photosynthesis–photosynthetically active radiation curves for two marine plants with fundamentally different light relations. The high-light plant, which has a higher Pmax but requires much more light, is typical of high-light environments such as…
Image
from article Swamp, marsh, and bog
Cross-sectional diagram representing the progressive filling by vegetation of a pit lake in recently glaciated terrain.
Image
from article Plant vulnerability to climate change
Subarctic tundra and vegetation of the Denali National Park and Preserve in Alaska. As a result of climate change and the resultant poleward and upward shift of plant ranges, plants and their ecosystems may become particularly vulnerable. (Credit:…
Image
from article Plant vulnerability to climate change
Blue grama (Bouteloua gracilis) growing in Montana. As a result of warming temperatures, this type of grass could face decreased productivity, allowing forbs to increase and making the ecosystem less tolerant of drought and grazing. (Credit: Matt…
Image
from article Plant vulnerability to climate change
Modeled distribution of suitable climate space in Europe for stiff sedge (Carex bigelowii), which is an Arctic-Alpine plant: (a) during the period 1961–1990 (green color = suitable climate space during the 1961–1990 period); (b) climate model…
Image
from article Plant vulnerability to climate change
The endangered western prairie fringed orchid (Platanthera praeclara) is declining across much of its range in North America. (Credit: U.S. Fish and Wildlife Service)
Image
from article Plant juvenility
The basic miRNA, siRNA, and ta-siRNA pathways in plants. The enzymes that carry out the different steps are written to the right of the downward arrows. The miRNA pathway schematic shows processing of the hairpin into an miRNA:miRNA* duplex by the…
Image
from article Plant juvenility
The developmental expression patterns of genes that regulate vegetative phase change. This graph is meant to show only the changes in expression for each gene during development rather than actual expression levels or relative levels between genes.
Image
from article Rosemary
Leaves of rosemary (Rosmarinus officinalis). (Photograph courtesy of Forest and Kim Starr)
Image
from article Squash
Zucchini (Cucurbita pepo), a type of summer squash, with flowers. (Credit: Howard F. Schwartz, Colorado State University/www.Bugwood.org)
Image
from article Squash
Crookneck squash (Cucurbita moschata). (Credit: Howard F. Schwartz, Colorado State University/www.Bugwood.org)
Image
from article Squash
Delicata squash (Cucurbita pepo), a variety of winter squash. (Credit: Shaun Case)
Image
from article Squash
Leaves of Cucurbita pepo infected by a squash mosaic virus. (Credit: William M. Brown, Jr./www.Bugwood.org)
Image
from article Speech
Human head and thorax. (Courtesy of G. E. Peterson)
Image
from article Speech
Action of the glottis during speech. (a) Six successive positions of the vocal folds in one vibration cycle at 120 Hz. (b) Relation between pitch and vocal fold tension. (Courtesy of D. W. Farnsworth)
Image
from article Speech
Sound spectrograms of the utterance “speech production.” (a) Energy patterns: A, pulse; B, periodic; C, aperiodic; and D, silence. (b) The dotted lines represent the pitch pattern of the utterance.
Image
from article Speech
Computer-generated three-dimensional spectral display of the spoken syllable “yah.”
Image
from article Speech
Speech flakes of vowels in the words (a) “far,” (b) “food,” and (c) “fee.” (Courtesy of Charles Wooters)
Image
from article Speech
Regions of the brain involved in speech. (a) Left hemisphere, usually more involved in speech functions than the right hemisphere. (b) A model for the neural processes involved in speaking a heard word. Arrows indicate the path of the relayed signal…
Image
from article Dormancy
Viviparous seeds of maize (Zea mays) germinating on the cob because of a mutation (vp14) preventing abscisic acid synthesis. (From S. H. Schwartz and J. A. D. Zeevaart, Abscisic acid biosynthesis and metabolism, pp. 137–155, in P. J. Davies, ed.,…
Image
from article Phaeophyceae
Embryonic sporophyte of Desmarestia anceps, showing trichothallic growth resulting in an embryonic stipe and several pairs of embryonic branches.
Image
from article Mental disorders
X-ray of a human brain (side view) against a black background. The image is transparent and detailed with soft blue swaps. (Credit: Brainmaster/Getty Images)
Image
from article Mental disorders
Colorized CT (computerizd tomography) scan of a healthy brain (view from above). The axial (horizontal) scan has revealed the head and brain in cross section. The front of the head is at the top. The ventricles (dark areas, center), which lie…
Image
from article Coriander
Coriander seeds (Coriandrum sativum). (Photograph courtesy of Steve Hurst, USDA–NRCS PLANTS Database)
Image
from article Marine conservation
A marine conservation biologist surveying marine invertebrates in a Mediterranean marine protected area in the Gulf of Gökova, Turkey. (Credit: Images & Stories/Alamy Stock Photo)
Image
from article Marine conservation
Bleached Acropora coral in shallow water, French Polynesia. Warming climates have affected marine habitats, with numerous marine species being depleted, threatened, or endangered. (Credit: Seaphotoart/Alamy Stock Photo)
Image
from article Marine conservation
An oil slick off a beach along the South Devon coast of England. Restoration efforts undertaken by marine conservationists attempt to return compromised habitats to ecologically functional, more pristine conditions. (Credit: Richard Packwood/Getty…
Image
from article Social mammals
Meerkats (Suricata suricatta) are notable social mammals. Here, they are looking for danger outside of their den. (Credit: Alta Oosthuizen/Shutterstock)
Image
from article Social mammals
An adult female African lion (Panthera leo) nurses four cubs. The early ingestive behavior (nursing) of mammals has a high degree of social significance. (Credit: Glow Images)
Image
from article Social mammals
Mexican spider monkeys (Ateles geoffroyi vellerosus) are primates that display many examples of social behavior and organization. (Credit: Oksana Kunka/123RF)
Image
from article Strawberry
June-bearing strawberries (Fragaria × ananassa), which are produced in early summer. (Photo courtesy of Kimberly Lewers, Agricultural Research Service, United States Department of Agriculture)
Image
from article Strawberry
Botrytis cinerea fungal sporulation on a ripe strawberry. (Photo courtesy of Scott Bauer, Agricultural Research Service, United States Department of Agriculture)
Image
from article Scrophulariales
Flowers of the common snapdragon (Antirrhinum majus), a typical member of the family Scrophulariaceae in the order Scrophulariales (Lamiales). (Photo by Ondřej Zicha, BioLib, Czech Republic)
Image
from article Venus' flytrap
Dionaea muscipula (the Venus' flytrap) growing in a South Carolina nature preserve. Winged petioles and traps in various stages of the capture cycle are visible. The plant is surrounded by Sphagnum moss, which is a frequent community associate.…
Image
from article Venus' flytrap
Stages in the capture and digestion of a fly by the Venus' flytrap. A prey item is attracted to the trap margins by nectar (a). When a trigger hair on the inside leaf surface is twice stimulated (b), the trap closes rapidly (c). Complete closure is…
Image
from article Oats
Oats (genus Avena). (Photo by Jan Samanek, State Phytosanitary Administration, Czech Republic)
Image
from article Oats
Oat panicles with many branches and spikelets. (Photo by Jan Samanek, State Phytosanitary Administration, Czech Republic)
Image
from article Oats
Oat florets. Scale bar = 1 cm (0.4 in.). (Photo by Steve Hurst, USDA–Natural Resources Conservation Service PLANTS Database)
Image
from article Oats
Crown rust on oat leaves. This devastating disease is caused by Puccinia coronata. (Photo courtesy of the USDA Agricultural Research Service)
Image
from article Oats
Stem rust infection (caused by Puccinia graminis) on oat stems. (Photo by Howard F. Schwartz, Colorado State University)
Image
from article Cell plastids
Light microscope view of part of Hypochaeris radicata leaf, showing chloroplasts sectioned in a variety of planes and displaying internal grana.
Image
from article Cell plastids
Three-dimensional model of grana with intergranal connections. (After W. Wehrmeyer, Planta, 63:13–30, 1964)
Image
from article Cell plastids
Electron microscope view of two oat leaf chloroplasts, one showing successive layers of grana in side view, and the other showing grana in face view (disk shape of constituent thylakoid lobes are seen).
Image
from article Cell plastids
Part of oat leaf chloroplast at higher magnification. Grana are seen in side view, revealing profiles of membranes. Thylakoids that interconnect grana are shown, with components of stroma, or ground substance, in which thylakoids lie. The dense…
Image
from article Cell plastids
Proplastid in cell of broad bean root tip. Double membranous envelope is shown and rudimentary nature of internal membrane system is obvious.
Image
from article Forest ecosystem
Forest in Moran State Park on Orcas Island, Washington. (Credit: Chris Willig)
Image
from article Forest ecosystem
Forest fire in No Name Creek area of Colorado. (Credit: Andrea Booher/FEMA)
Image
from article Forest ecosystem
Puma and cub in forest. (Credit: Grant Faint/Stockbyte/Getty Images)
Image
from article Forest ecosystem
Conceptual model of elemental cycling in a terrestial ecosystem, emphasizing the presence and activities of arthropod consumers. The indirect regulation of elemental movement by arthropods is indicated by the hourglass-shaped valves on these flows.…
Image
from article Forest ecosystem
The southern pine beetle (Dendroctonus frontalis) is a destructive insect pest of coniferous forests in the southern United States. (Credit: U.S. Forest Service)
Image
from article Forest ecosystem
Belowground food web. (Credit: Elaine Ingham)
Image
from article Fruit, tree
Apple trees growing in an orchard. (Photo by Charles Rondeau)
Image
from article Fruit, tree
Apple scab on fruit. This disease, caused by the fungus Venturia inaequalis, leads to unsightly blemishes on ripe apples. (Photo courtesy of the University of Georgia Plant Pathology Archive)
Image
from article Fruit, tree
Brown rot, caused by the fungus Monilinia fructicola, on a peach. (Photo by Jonas Janner Hamann, Universidade Federal de Santa Maria, Brazil)
