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Modern boundaries of the constellation Cancer, the Crab. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension representing 15° of…

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from article Phosphatase

Reaction mechanism for the phosphatase-catalyzed hydrolysis of a phosphoric acid ester. Steps: (1) Noncovalent binding of the phosphatase (EH) to the organic substrate (RPO42−). (2) Release of an alcohol from the complex and covalent binding of…

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from article Boring bivalves

A pholad shell: (a) external view, showing position of accessory plates and parts of the valve; (b) internal view, showing position of muscle and parts of the valves. (After R. D. Turner, The family Pholadidae in the western Atlantic and eastern…

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from article Boring bivalves

Typical boring bivalves: (a) Diplothyra smithii boring in Crassostrea virginica; (b) Penitella penita boring in shale; (c) Zirfaea crispata removed from burrow, showing foot, anterior adductor muscle, and siphons (from R. D. Turner, The family…

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from article Fungal genomics

Fungal papers published by year that included the term genome or genomics.

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from article Apraxia

Language skills involve comprehension, speech, reading, and writing. The motor speech area (Broca's area) in the brain initiates speech motor functions. The Wernicke area aids in the interpretation of language. The primary motor cortex is…

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from article Carp

Mirror carp (Cyprinus carpio), showing a few large scales.

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from article Cheilostomata

Cheilostome colonies and zooecia (scale of colonies, ×1). (a) Encrusting sheets of Membranipora and Electra on bivalve shell. (b) Erect, flat branches of Chartella. (c) Upper (frontal) surface section (scale, ×8) of encrusting sheet of…

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from article Cheilostomata

Anascan cheilostome zooid, showing soft parts and zooecium, with tentacles extended. (Reprinted with permission from R. J. Cuffey and J. E. Utgaard, Bryozoans, in R. Singer, ed., Encyclopedia of Paleontology, Fitzroy Dearborn, 1999)

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from article Cheilostomata

Arrangements of frontal walls in Cheilostomata. The X indicates the membrane that can be pulled by muscles in order to displace fluid/liquid that pushes the polypide (shaded) out so that the tentacles can feed in the space above the skeleton. (a)…

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from article Genetically engineered plant

Stalks of genetically engineered barley. This particular genetically engineered plant carries a gene that helps it to resist attack by barley yellow dwarf virus. (Credit: Jack Dykinga/Agricultural Research Service, U.S. Department of Agriculture)

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from article Genetically engineered plant

Plasmid vector schematic illustrating the common elements of a plasmid vector that is used to deliver the gene (or genes) of interest to plant cells that have been prepped for transformation. Depending on the transformation technique, the components…

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from article Genetically engineered plant

A simplified schematic showing the elements of a gene gun as used in biolistic transformation of plant cells. Plasmid vectors that contain the gene of interest and other vector components are purified and coated onto microscopic particles of gold or…

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from article Genetically engineered plant

The basic steps in transforming plants using Agrobacterium-mediated transformation. Tumor-inducing (Ti) plasmid vectors are manipulated to remove the opine production genes, which the bacterium transfers to the plant in nature. In their place,…

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from article Genetically engineered plant

The binary vector system allows scientists to manipulate only a small vector (plasmid B) that contains the T-DNA region (the DNA to be transferred to the plant), whereas other trans-acting components of the Ti plasmid that are needed for DNA…

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from article Liver disorders

Fatty metamorphosis (fatty liver) can affect the entire liver in alcoholics. Fatty liver also can occur as a result of other processes, including malnutrition and obesity, and is referred to as nonalcoholic fatty liver disease. (Copyright © McGraw…

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from article Insectivora

Buena Vista Lake ornate shrew (Sorex ornatus relictus) sitting on the palm of a hand. (Photo courtesy of California State University, Stanislaus; and the U.S. Fish and Wildlife Service)

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from article Insectivora

Reconstruction of Deinogalerix, an extinct giant insectivore (erinaceid) from the Miocene of Italy. (Adapted from M. Freudenthal, Deinogalerix koenigswaldi nov. gen., nov. spec., a giant insectivore from the Neogene of Italy, Scr. Geol., 14:1–19,…

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from article Insectivora

Skull of Kennalestes, an extinct proteutherian from the Cretaceous of Mongolia.

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from article Supernova

Telescopic imagery of one of the closest supernovae in a generation, SN 2011fe, captured in January 2011. It exploded in the Pinwheel Galaxy, located about 21 million light-years away. The supernova, a Type Ia, shines brighter than its entire host…

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from article Supernova

Optical spectra of four supernovae, all about 1 week old, are shown, with types indicated in parentheses. The Si II line is used to identify Type Ia spectra. (Credit: Alex Filippenko)

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from article Supernova

Schematic light curves for supernovae of four types and for SN 1987A. The absolute values of magnitude are quite approximate as each curve depends upon uncertain distances and there can be considerable variation within each subclass (less in Type Ia…

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from article Supernova

Region of the Tarantula Nebula in the Large Magellanic Cloud (a) before Supernova 1987A (the star that exploded to create the supernova is indicated by the arrow) and (b) with the supernova about 2 weeks after it was discovered. (Credit: Australian…

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from article Supernova

Supernova 1987A and its triple ring system 20 years after the explosion, as observed by the Hubble Space Telescope. The inner ring, which appears to be elliptical but is actually a circular equatorial ring, displays 30–40 bright spots, like pearls…

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from article Marmot

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from article Space biology

Aboard the International Space Station, NASA astronaut Steve Swanson harvests a crop of red romaine lettuce. This and other plant varieties have been grown in the station's Vegetable Production System (Veggie), for space biology experiments as well…

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from article Space biology

During a Space Shuttle Endeavour flight in 2008, astronauts Shane Kimbrough and Sandra Magnus experience weightlessness, further demonstrated by the floating apples, oranges, and pears. (Credit: NASA)

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from article Cell biology

A typical animal cell and its major organelles. (Credit: McGraw-Hill Education)

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from article Caprimulgiformes

Puerto Rican nightjar (Caprimulgus noctitherus). (Photo by Mike Morel, U.S. Fish and Wildlife Service)

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from article Deer

Male white-tailed deer (Odocoileus virginianus). (Credit: N. Mishler and M. J. Mishler/U.S. Fish and Wildlife Service)

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from article Deer

Male red deer (Cervus elaphus). (Credit: Rictor Norton and David Allen)

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from article Deer

Adult male Siberian musk deer (Moschus moschiferus). (Credit: Brent Huffman/Ultimate Ungulate Images)

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from article Energy metabolism

The energy derived from the oxidation of carbohydrates, fats, and proteins sustains the biochemical reactions required for life. Through a number of steps, energy is released and coupled to the biosynthesis of adenosine triphosphate (ATP). Acetyl…

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from article Energy metabolism

Energy metabolism involves the conversion of glucose to carbon dioxide and water to liberate free energy (termed Gibbs free energy). This energy is released in a stepwise fashion and is coupled to the biosynthesis of adenosine triphosphate (ATP)…

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from article Polarized light microscope

Diagram of a high-sensitivity biological polarizing microscope. Polarizing microscopes for petrography may not require the use of the expensive prism polarizer and analyzer, which can be replaced by dichroic polarizing filters. Some petrographic…

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from article Anemia

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from article Anemia

Aplastic anemia. This low-power photomicrograph of the bone marrow exhibits only a small amount of hematopoiesis (the process by which the cellular elements of the blood are formed). (Copyright © McGraw-Hill Education)

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from article Anemia

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from article Homocysteine

Homocysteine metabolism. CBS, cystathionine ß-synthase; MTHFR, 5,10-methylene tetrahydrofolate reductase; MS, methionine synthase; BHMT, betaine:homocysteine methyltransferase; SAM, S-adenosylmethionine; SAH, S-adenosylhomocysteine; 5-methyl THF,…

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from article Opioid

Chemical structures of various opioid compounds: (a) morphine (a plant-derived mu-opioid agonist from the opium poppy), (b) heroin (a semisynthetic mu-opioid agonist derived from morphine), and (c) fentanyl (a synthetic mu-opioid agonist). (Credit:…

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from article Echolocation

Echolocation is a physiological tool used by gray bats (Myotis grisescens). (Credit: Amareta Kelly)

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from article Echolocation

Sound spectrograms representing sonar signals of (a) Brazilian or Mexican free-tailed bats (Tadarida brasiliensis), (b) big brown bats (Eptesicus fuscus), (c) Wagner's mustached bats (Pteronotus personatus), and (d) greater horseshoe bats…

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from article Chevrotain

Water chevrotain (Hyemoschus aquaticus). (Photo by Brent Huffman; courtesy of Ultimate Ungulate)

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from article Cat

Puma (Puma concolor) and cub in forest. (Credit: Grant Faint/Stockbyte/Getty Images)

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from article Cat

A domestic cat (Felis catus) nursing her kittens. (Credit: Westend61/Getty Images)

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from article Cat

Canadian lynx (Lynx canadensis). (Credit: Erwin and Peggy Bauer/U.S. Fish and Wildlife Service)

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from article Cat

Ocelot (Leopardus pardalis). (Credit: Tom Smylie/U.S. Fish and Wildlife Service)

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from article Cat

Two cheetahs (Acinonyx jubatus). (Credit: Gary M. Stolz/U.S. Fish and Wildlife Service)

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from article Cat

Lion (Panthera leo). (Credit: Trisha M. Shears)

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from article Cat

Siberian tiger (Panthera tigris). (Credit: John and Karen Hollingsworth/U.S. Fish and Wildlife Service)

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from article Ovary

Anatomy of an ovary in an adult human female. The left inset shows the location of a pair of ovaries in relation to the uterus. The right inset is a close-up image of an oocyte. (Copyright © McGraw Hill)

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from article Ovary

Colored light micrograph of a section through a primary follicle in an ovary. The egg's nucleus is located at the center, surrounded by cuboidal follicular cells (yellow). (Credit: Steve Gschmeissner/Science Photo Library/Alamy Stock Photo)

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from article Ovary

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from article Ovary

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from article Ear (vertebrate)

Anatomy of a human ear, including three sections: outer ear, middle ear, and inner ear. The outer ear and middle ear transmit sounds to the inner ear. In the inner ear, vibrations are converted to nerve signals. (Copyright © McGraw Hill)

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from article Ear (vertebrate)

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from article Ear (vertebrate)

Dorsal view of the anterior part of the head and body of an otophysan fish showing the ear and its position relative to the brain. Also shown are the swim bladder and the Weberian ossicles. (Credit: A. N. Popper and S. Coombs)

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from article Ear (vertebrate)

Diagrammatic view of the middle and inner ears of a lizard (reptile). (Credit: D. B. Webster and M. Webster)

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from article Agricultural machinery

A tractor pulling a multipurpose machine used for precision tillage and planting. (Credit: Scott Bauer/U.S. Department of Agriculture)

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from article Agricultural machinery

Agricultural aircraft applying a chemical pesticide on a field. (Credit: jupiterimages/Getty Images)

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from article Agricultural machinery

A combine harvester hopper filling up with corn kernels as the machine harvests the field. (Credit: Glow Images)

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from article Agricultural machinery

A harvester machine is used to drop tomatoes into a container. (Credit: Phil Schermeister/National Geographic RF/Getty Images)

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from article Lemming

The lemming, a small burrowing rodent with short legs and stout claws adapted for digging. (Photo by Robert R. Nack, Minnesota Cooperative Fish and Wildlife Research Unit)

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from article Synthetic biology

Graphical summary of synthetic biology foundational disciplines, technologies, and applications in medicine. Synthetic biology, which evolved from advances in molecular biology, genomics, and directed evolution, has led to the development of new…

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from article Saffron

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from article Messier Catalog

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from article Messier Catalog

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from article Immunity

The immune response to an invading microbe can generate immunity via antibody production. Steps: (1) Antigen binds to a B cell receptor (antibody) on a B cell. (2) The B cell may also receive more information from a helper T cell about the presence…

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from article Immunity

Colored scanning electron micrograph of an activated human macrophage. Activation of macrophages is often an important aspect of the immune response. (Credit: Steve Gschmeissner/Science Photo Library/Alamy Stock Photo)

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from article Immunity

Colored scanning electron micrograph of B lymphocytes. These white blood cells are involved in the immune response. (Credit: Steve Gschmeissner/Science Photo Library/Alamy Stock Photo)

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from article Evolutionary computation

Typical flowchart for an evolutionary algorithm.

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from article Evolutionary computation

Traveling salesperson problem comprising 1000 cities. (a) Best-evolved solution after examination of 4 × 107 possible solutions. (b) Rate of evolutionary optimization.

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from article Evolutionary computation

Arrangement for distributing an evolutionary algorithm across multiple processors. Each processor holds its own population that undergoes random variation and selection. Occasionally, solutions will migrate from one population to another and begin…

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from article Symphyla

Scutigerella immaculata. This symphylan is a garden and greenhouse pest. (Photo by Ivo Antušek; BioLib.cz)

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from article Symphyla

Cercus (enlarged view). (Courtesy of Robert T. Allen, Academy of Natural Sciences, Philadelphia; Amanda Lawrence, Electron Microscope Center, Mississippi State University)

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from article Cestida

Structure of Cestum veneris.

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from article Precession of equinoxes

Illustration of the celestial sphere, an imaginary sphere of infinite radius centered on the Earth and projected using Earth's celestial poles and celestial equator. (Credit: NASA)

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from article Precession of equinoxes

Motion of the Earth's axis of rotation.

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from article Lipidomics

Components of phosphoinositides. (a) General structure of phospholipids, showing positions sn-1 and sn-2, where various fatty acids may attach. X represents a phosphate-linked group; FA represents a fatty acid. (b) Space-filling models of four…

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from article Lipidomics

Selected MS ion chromatograms of synthetic 1,2-diacyl-sn-3-glycerol (DAG) molecular species from polymorphonuclear neutrophilic leukocytes (PMNs) of patients with local aggressive periodontal disease. DAG species were resolved and identified by…

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from article Lipidomics

Families of bioactive lipids. (a) Arachidonic acid is the precursor for many of the known bioactive mediators, such as EETs, prostaglandins, leukotrienes, and lipoxins. (b) Eicosapentanoic acids (C20:5 and C22:6) are precursors to potent new…

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from article Lipidomics

Functional-mediator lipidomics approach to evaluate and profile compounds during experimental inflammation and its resolution.

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from article Thrombosis

Thrombin molecular model. (Credit: Molekuul/Science Photo Library/Getty Images)

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from article Thrombosis

Organized thrombus in an artery with recanalization.

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from article Thrombosis

Organized thrombus in an artery with scar formation; the artery is completely occluded by the fibrotic mass.

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from article Cephalochordata

European lancelet (Branchiostoma lanceolatum). (After J. E. Webb, On the populations of Branchiostoma lanceolatum and their relations with the West African lancelets, Proc. Zool. Soc. Lond., 127:131, 1956)

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from article Decision theory

Decision tree for the problem given in the text. Numbers at nodes represent time past alarm (7:00 A.M.), and numbers at branches refer to the decision mode or state of nature.

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from article Decision theory

From of a decision matrix. Oij = outcome corresponding to the interaction of a strategy (Si) and a state of nature (Nj).

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from article Decision theory

Decision tree structure to determine the subjective utility of lottery outcomes.

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from article Decision theory

Hypothetical subjective utility curves.

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from article Mitochondria

A mitochondrion is a specialized compartment (organelle) of a eukaryotic cell (upper left). The electron micrograph (upper right) and the accompanying illustration (bottom) indicate the outer and inner membranes, cristae, and matrix. [Credit…

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from article Mitochondria

Three-dimensional reconstruction of a rat liver mitochondrion produced by electron microscopic tomography. During imaging, the sample is tilted around one or more axes to generate different projections that are later digitally combined to produce a…

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from article Mitochondria

Guard cells of a transgenic tobacco plant expressing green fluorescent protein (GFP) targeted to mitochondria. Chloroplasts (cell plastids) show red chlorophyll autofluorescence and mitochondria show green protein fluorescence. (Credit: Rainer…

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from article Mitochondria

Mitochondria are the powerhouses of the cell, being responsible for energy generation in the form of adenosine triphosphate (ATP). ATP is produced by the coupled processes of electron transport and oxidative phosphorylation in mitochondria.…

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from article Eye (invertebrate)

Pigment spot ocellus, the simplest invertebrate eye. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)

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from article Eye (invertebrate)

Simple open eye of the marine limpet Patella. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)

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from article Eye (invertebrate)

Large, complex eye of the marine snail Murex. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)

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from article Eye (invertebrate)

Simple pigment cup ocellus of flatworm. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)

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from article Eye (invertebrate)

Large, complex eye of the clam worm Nereis. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)

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from article Eye (invertebrate)

Simple eye of Ranzania, a marine annelid. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)

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