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from article Sturgeon
Shovelnose sturgeon (Scaphirhynchus platorynchus). (Photo by Konrad Schmidt)
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from article Set theory
Sets of points on a plane.
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from article Set theory
Vertical projection of set X onto segment Y.
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from article Polygon
Triangle ABC with nine-point circle. Symbols are explained in text.
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from article Polygon
Regular pentagon, showing approximate construction without a protractor. Symbols are explained in text.
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from article Polygon
Polar triangles A, B, C and A′, B′, C′. The center of the sphere is at O. AQ and PB are 90° arcs, so angle C′ = arc PQ is the supplement of AB.
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from article Epicycloid
Diagram of an epicycloid.
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from article Plant-water relations
Water transport system in plants. The xylem (the principal water-conducting tissue) is continuous from the roots through the stem to the leaves. (Copyright © McGraw-Hill Education)
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from article Plant-water relations
Relationship of water and turgor pressure in plants: (a) the plant cells in a wilted plant need water; (b) after water enters the plant, the plant cells become turgid. (Copyright © McGraw-Hill Education)
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from article Plant-water relations
Light-microscope view of a stoma on a plant cell. (Credit: Bumbim/Stockimo/Alamy Stock Photo)
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from article Plant-water relations
Daily periodicity of transpiration of alfalfa on three successive days with adequate light, temperature, and soil water conditions. (Copyright © McGraw-Hill Education)
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from article Plant-water relations
Colored scanning electron micrograph (SEM) of a section through wood showing the phloem vessels (dark green holes) and xylem tissue (lower frame). (Credit: Steve Gschmeissner/SPL/Getty Images)
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from article Camel
Bactrian camel (Camelus bactrianus). (Photo courtesy of Brent Huffman, Ultimate Ungulate Images)
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from article Plant communication
Hillsides in central California covered by hard chaparral composed almost entirely of chemise shrubs. Chemise (also spelled chamise) produces allelopathic chemicals that, through plant communication, inhibit the germination of seeds and the…
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from article Spelaeogriphacea
Lateral and dorsal views of the Western Australian spelaeogriphacean species Mangkurtu mityula.
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from article Greenhouse
A greenhouse is a transparent, enclosed, climate-controlled structure in which young, tender, or out-of-season plants are cultivated and protected. (Credit: Antema/Getty Images)
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from article Greenhouse
Common commercial greenhouse shapes are the hoop, arch, and gable.
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from article Greenhouse
Interior of an agricultural high tunnel. Long rows of fresh green lettuce are being cultivated. (Credit: Photology1971/Shutterstock)
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from article Greenhouse
Modern greenhouses utilize computerized technologies to control and regulate various environmental parameters, including air temperature, air movement, carbon dioxide concentration, relative humidity, and supplemental light. (Credit:…
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from article Diplomonadida
A diplomonad, Trepomonas rotans.
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from article Seed
Basic eudicot (bean) and monocot (corn) seed structure and germination. (Copyright © McGraw Hill)
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from article Seed
Seed structures: (a) median longitudinal section of pea ovule shortly after fertilization, showing attachment to pod tissues; (b) mature kidney bean; (c) mature castor bean; (d) opened embryo of mature kidney bean. Scale bar = (a, b) 0.5 mm (0.02…
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from article Seed
In this longitudinal section of a castor bean seed, the median embryo is surrounded by copious endosperm. Scale bar = 1 mm (0.04 in.). (Credit: Steven P. Lynch)
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from article Seed
Seed dormancy and viability during development under (a) field conditions and (b) greenhouse conditions. Black medick (Medicago lupulina) seeds were detached from the plant and tested for germination. Three phases of germinability occurred depending…
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from article Seed
A germinating cabbage seed in soil with the root developing with root hair. (Credit: Nigel Cattlin/Alamy Stock Photo)
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from article Currant
American black currants (Ribes americanum). (Photo courtesy of Steve Hurst, ARS Systematic Botany and Mycology Laboratory, USDA)
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from article Currant
Flowering branch of golden currant (Ribes aureum). (Photo courtesy of Susan McDougall )
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from article Photosynthesis
A simplified diagram of a chloroplast is used to delineate the overall process of photosynthesis. Chloroplasts in the plant cells of leaves absorb light energy and convert it into chemical energy, which is used to synthesize carbohydrates (CH2O) and…
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from article Photosynthesis
The photosynthetic electron transport system provides the means to drive the process of oxygenic photosynthesis, which involves the oxidation of water (H2O) to produce oxygen (O2) molecules. These oxygen molecules are then released into the…
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from article Photosynthesis
A typical chloroplast: (a) schematic diagram of a higher plant chloroplast; (b) electron micrograph of a chloroplast. (Credit: Based on original images provided by L. Taiz and E. Zeiger)
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from article Photosynthesis
A diagram of the four major protein complexes of the thylakoid membrane. (Copyright © McGraw-Hill Education)
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from article Photosynthesis
Absorption spectra of three photosynthetic pigments: chlorophyll a, chlorophyll b, and the carotenoids. (Copyright © McGraw-Hill Education)
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from article Photosynthesis
Schematic outline of the C3 (Calvin-Benson-Bassham) carbon dioxide assimilation cycle (including the three phases of carboxylation, reduction, and regeneration), showing the partitioning of assimilated carbon into starch within the chloroplast [via…
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from article Photosynthesis
Colorized structural model of Rubisco. (Copyright © McGraw-Hill Education)
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from article Photosynthesis
Schematic outline of the C4 carbon dioxide assimilation process in the mesophyll cells and bundle sheath cells of a type-1 NADP-ME plant. (Copyright © McGraw-Hill Education)
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from article Photosynthesis
Scheme for the flow of CO2 within a single crassulacean acid metabolism (CAM) cell over a day, showing the initial dark CO2 fixation, malic acid storage in the vacuole at night, decarboxylation, and the C3 cycle occurring the next day. (Copyright ©…
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from article Fruit
Tissue components of fruit of Prunus persica (peach). (a) Longitudinal section of fruit, a drupe. Circles indicate positions of sections shown in b–e, which are representative of a young fruit about 1 in. (2.5 cm) in diameter. (b) Epidermal hair of…
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from article Fruit
Tissue components of fruit of Malus sylvestris (apple). (a) Transverse section of fruit, a pome. Rectangles indicate positions of sections shown in b–h; b and d–g are from a young fruit 0.4 in. (1 cm) in diameter; c and h are from a mature fruit.…
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from article Fruit
Fleshy fruits. (a) Aggregate fruit (blackberry) in surficial view and (b) in sectional view. (c) Multiple fruit (mulberry). (d–i) Simple fruits: (d, e) pome (apple), (f) drupe (cherry), (g) berry (tomato), (h) hesperidium (orange), (i) pepo…
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from article Fruit
Dehiscent dry fruits: (a) Follicles (milkweed). (b) Legume (bean). (c) Loment (beggar's-ticks). (d, e) Silique, closed and open (mustard). (f, g) Silicle, closed and open (shepherd's-purse). (h) Capsule (lily). (i) Pyxis, closed and open (purslane).
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from article Fruit
Indehiscent dry fruits. (a–d) Achenes; (a) clematis, (b) dandelion, (c) buttercup, and (d) sticktight. (e) Caryopsis or grain (corn) in surficial view and (f) in sectional view. (g) Utricle (goosefoot) in surficial view and (h) in sectional view.…
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from article Fruit
Transverse section of wall of immature fruit of Simmondsia chinensis (jojoba) at point of potential dehiscence (central smaller cells). The outer epidermis (at the top) consists of tannin-filled macrosclereids. (From R. Schmid, Floral and fruit…
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from article Fruit
Transverse sections of placental vascular bundles of (a) female flower bud and (b) mature fruit of Actinidia chinensis (kiwi). Both bundles are from comparable parts of the flower or fruit, both are mesarch amphicribral, and both are at the same…
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from article Fertilization (plant)
Longitudinal section through (a) an immature and (b) a mature archegonium. The sperm swim through the canal to the egg.
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from article Fertilization (plant)
Gymnosperm reproductive structures. (a) Immature pollen grain and (b) pollen tube of pine. (c) Longitudinal section through a pine ovule showing the mature female gametophyte with two archegonia and the pathway of the pollen tube to the egg cell.
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from article Fertilization (plant)
Pistil of a flowering plant showing the embryo sac and the path of the pollen tube.
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from article Dormouse
The fat dormouse (Glis glis). (Photo courtesy of Alenka Kryštufek)
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from article Isobryales
Fontinalis duriaei, an example of the order Isobryales. (a) Leaf. (b) Apex of leaf. (c) Trellis and teeth. (d) Alar cells. (After W. H. Welch, Mosses of Indiana, Indiana Department of Conservation, 1957)
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from article Fossil primates
Representatives of living primate families. (Copyright © McGraw-Hill Education)
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from article Fossil primates
Carpolestes simpsoni, a 55.5-million-year-old plesiadapiform from Wyoming: (a) skeleton as recovered, laid out in approximate anatomical position; (b) reconstruction in life stance on a tree branch; elements in dark gray are known; (c) external…
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from article Fossil primates
Cranium of the omomyoid tarsiiform Teilhardina asiatica, from deposits dated approximately 55 MYA in China: (a) dorsal (top) view as found; (b) left lateral reconstruction. (Credit: Xijun Ni)
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from article Fossil primates
Anjohibe (Madagascar) specimen of Palaeopropithecus ingens (an extinct lemur), mounted in a probable habitat posture. (Credit: American Geological Institute)
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from article Fossil primates
Partly reconstructed skeleton (casts) of Paracolobus chemeroni, a 3.2-million-year-old colobine monkey from Kenya, on exhibit at the American Museum of Natural History in New York. (Credit: Eric Delson)
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from article Fossil primates
Reconstructed skeleton of Proconsul heseloni, an early hominoid (23–14 MYA) from East Africa. Known parts are shaded. (Credit: R. L. Ciochon and R. S. Corruccini)
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from article Gyrocotylidea
Gyrocotylidean adult and larva.
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from article Science
Italian physicist and astronomer Galileo Galilei (1564–1643) founded the modern scientific method of deducing laws to explain the results of observation and experiment. (Credit: Getty Images)
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from article Kutorginata
Kutorgina, showing (a) exterior of pedicle (ventral) valve; (b) lateral view of shell; (c) exterior of brachial (dorsal) valve. (After C. D. Walcott, Cambrian Brachiopoda, USGS Monogr., vol. 51, 1912)
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from article Fossil seeds and fruits
Early Tertiary fruits and seeds which were found in the Brandon lignite of Vermont. (a) Endocarps of Symplocos. (b) Seeds of grape (Vitis). (c) Seeds of Rubus. (d) Endocarp of extinct species of Nyssa. (e) Seeds of fossil genus of family Rutaceae,…
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from article Procellariiformes
Black-footed albatross (Phoebastria nigripes). (Photo from Olympic Coast National Marine Sanctuary/National Oceanic & Atmospheric Administration)
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from article Pinales
Leaf, branch, and cone characteristics of conifers. (a) Branch of pine with leaves and ovulate cones. (b) Ovulate cone of spruce cut longitudinally to show scales with ovules. (c) Detail of one scale with two ovules. (Copyright © McGraw-Hill…
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from article Pinales
Fertile dwarf shoots of a cordaite and select fossil conifers, representing stages in cone scale evolution. A direct phylogenetic series is not implied. (a) In Cordaites, the ovules were borne terminally on the megasporophylls. (b) Emporia. (c) The…
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from article Predator-prey interactions
A predatory panther chameleon (Furcifer pardalis) is preying upon a cricket. (Credit: Cathy Keifer/Shutterstock)
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from article Predator-prey interactions
Predator-prey interactions play important roles in explaining the population dynamics of many species. In this photograph, a cheetah (Acinonyx jubatus) is hunting a springbok (Antidorcas marsupialis) in Namibia. (Credit: Elana Erasmus/Shutterstock)
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from article Predator-prey interactions
Snowshoe hare populations (solid blue circles) and lynx populations (white squares) inferred from the numbers of pelts sold to the Hudson's Bay Company. (Credit: Based on data compiled by D. A. MacLuclich; copyright © McGraw-Hill Education)
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from article Selaginellales
Characteristic features of a typical heterophyllous selaginellalean of the Stachygynandrum type. (After T. R. Webster, Developmental problems in Selaginella in an evolutionary context, Ann. Mo. Bot. Gard., 79:633–647, 1992)
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from article Watermelon
Watermelon (Citrullus lanatus): fruit growing in the field. (Photo courtesy of Howard F. Schwartz, Colorado State University, www.Bugwood.org)
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from article Watermelon
Anthracnose lesions (with concentric rings within the lesions) on a watermelon fruit. The pathogen responsible for these lesions is Colletotrichum orbiculare. (Photo courtesy of David B. Langston, University of Georgia, www.Bugwood.org)
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from article Lettuce
Lettuce (Lactuca sativa) growing near Yuma, Arizona. (Photo by Jeff Vanuga, USDA Natural Resources Conservation Service)
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from article Saxifragales
Chinese peony or common garden peony (Paeonia lactiflora), a popular ornamental plant member of the order Saxifragales. (Photo by Liz Best)
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from article Carboniferous
Carboniferous, the fifth period of the Paleozoic Era.
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from article Carboniferous
Development of stratigraphic nomenclature for the Carboniferous.
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from article Carboniferous
Curves outlining the fluctuations of sea level during the Carboniferous. The Mississippian sea-level curve is typical of times when glaciation was not a major factor in controlling sea levels, and the Pennsylvanian sea-level curve is characteristic…
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from article Carboniferous
Paleogeography of the Carboniferous. (a) Early Carboniferous (Mississippian) Tournaisian and Visean epochs, with a major east-west equatorial seaway between Euramerica and Gondwana. (b) Late Carboniferous (Pennsylvanian) Moscovian (or Desmoinesian)…
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from article Carboniferous
Typical shelf sedimentary patterns in Upper Carboniferous depositional sequences. The broken line represents the condensed section that forms during maximum sea-level highstands when sedimentation rates are low. The prominent unconformities at the…
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from article Asteroidea
A five-armed sea star (genus Fromia) resting on coral in the waters surrounding the Maldive Islands. (Credit: Ian Cartwright/Getty Images)
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from article Asteroidea
A representative asteroid, Astrostole scabra. (Copyright © McGraw-Hill Education)
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from article Asteroidea
The Pacific blue sea star (Linckia laevigata) belongs to the asteroid order Valvatida. This sea star is common in the tropical waters of the Indo-Pacific. (Credit: Comstock Images/Getty Images)
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from article Asteroidea
A large sun sea star (Solaster stimpsoni) in the intertidal-zone waters of Kodiak Island, Alaska. (Credit: Mandy Lindeberg/National Oceanic and Atmospheric Administration)
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from article Asteroidea
Transverse section through an asteroid arm. (Copyright © McGraw-Hill Education)
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from article Asteroidea
Anatomy of a sea star, Diplodontias robustus, as viewed from the aboral surface. (Copyright © McGraw-Hill Education)
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from article Burgess Shale
Marrella splendens, a characteristic Burgess Shale arthropod. The head shield bears two prominent pairs of spinose extensions; also visible are various appendages that include walking legs and gills. The prominent dark areas appear to represent…
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from article Burgess Shale
Cathaymyrus diadexus, a primitive chordate from the Chengjiang assemblage of China. The body is eellike, and at the anterior there are a pharynx and gill slits. (Copyright © Simon Conway Morris)
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from article Burgess Shale
An articulated halkieriid, Halkieria evangelista, from the Sirius Passet fauna, North Greenland. The body was coated with platelike sclerites, and at either end carried a large shell. (Copyright © Simon Conway Morris)
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from article Difference equation
Numerical solution of Eq. (32) for a = 0.05, b = 0.1, c = 0.01, and a step input. The solution uses the state-variable representation of Eq. (33) and the difference-equation approximation of Eq. (36) with h = 0.1.
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from article Collenchyma
Transverse sections of Jimsonweed (Datura stramonium), progressively magnified. (a) Stem section. (b) Stem section, showing the corner thickenings of collenchyma cell walls and air spaces surrounded by wall thickenings. (c) Collenchyma section,…
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from article Gopher
Plains pocket gopher (Geomys bursarius). (Photo courtesy of Bob Gress)
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from article Platyasterida
Ventral view of an arm and a portion of the disk of Platanaster ordovicus. Note lateral alignment of the arm plates. (After W. K. Spencer and C. W. Wright, Asterozoans, in R. C. Moore, Treatise on Invertebrate Paleontology, Pt. U, Echinodermata 3,…
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from article Rugosa
Rugose corals. (a) Aulacophyllum sp. of horn coral showing the major external features of a solitary coral skeleton; septa pinnately arranged about the cardinal fossula. Devonian, North America, ×0.75. [Most rugose corals need to be studied in thin…
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from article Rugosa
Rugose coral skeletons. (a) Palaeocyclus porpita, discoidal corallite, calical view with platelike epitheca beneath, cardinal septum shortened. Silurian, Sweden, ×2. (b) Caninia sp., typical horn coral in growth orientation with septa visible in the…
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from article Rugosa
Rugose coral skeletons. (a) Siphonphyllia gigantea, solitary cylindrical corallites prone on bedding plane; individual bottom-right showing sharp change of growth direction. Carboniferous, Ireland; width of photo, 1 m. (b) Arachnophyllum pentagonum,…
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from article Cycloid
Diagram of cycloid; symbols explained in text.
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from article Cucumber
Cucumber (Cucumis sativus) fruit growing on a vine in the field. (Credit: Howard F. Schwartz/Colorado State University)
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from article Cucumber
Downy mildew on a cucumber leaf. Angular lesions are induced by the leaf-inhabiting fungus Pseudoperonospora cubensis. (Credit: G. J. Holmes)
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from article Cucumber
Scab (causal fungus: Cladosporium cucumerinum) on a cucumber. (Credit: Mary Ann Hansen/Virginia Tech)
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from article Hyracoidea
Cape hyrax (Procavia capensis). (Photo by Lloyd Glenn Ingles; copyright © California Academy of Sciences)
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from article Bivalvia
Freshwater mussels (subclass Paleoheterodonta, class Bivalvia) in the Missouri River. (Credit: U.S. Fish and Wildlife Service)
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from article Bivalvia
Red shell of a spiny oyster (genus Spondylus, subclass Pteriomorphia, class Bivalvia). (Credit: Pablo Hidalgo/123RF)
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from article Bivalvia
Bivalve anatomy as represented by the quahog clam (Mercenaria mercenaria). (Copyright © McGraw-Hill Education)
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from article Field theory (mathematics)
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from article Field theory (mathematics)
