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from article Ovary

Ovarian histology. (a) Pika (Ochotona princeps); (b) pocket gopher; (c) prairie dog (Cynomys leucurus); (d) chicken (Gallus domesticus) (from W. Andrew, Textbook of Comparative Histology, Oxford, 1959). (e) Lizard (Xantusia vigilis) (courtesy of M.…

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from article Ovary

Structural formulas of the principal natural estrogens.

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from article Ovary

Active and inactive forms of pregnancy hormone.

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from article Ovary

Hormonal interactions of the hypothalamus, pituitary, and ovary.

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from article Ear (vertebrate)

Generalized diagram of a sensory hair cell found in the ear of all vertebrates.

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from article Ear (vertebrate)

Left-ear external view of the membranous labyrinths of (a) teleost, (b) frog, (c) bird, and (d) mammal. (After A. S. Romer, The Vertebrate Body, 3d ed., Saunders, 1962)

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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. (From A. N. Popper and S. Coombs, Auditory mechanisms in…

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from article Ear (vertebrate)

Diagrammatic view of the middle and inner ears of a lizard. (After D. Webster and M. Webster, Comparative Vertebrate Morphology, Academic Press, 1974)

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from article Ear (vertebrate)

Schematic drawing of the human ear. (After M. Brödel, Three Unpublished Drawings of the Anatomy of the Human Ear, Saunders)

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from article Ear (vertebrate)

Otic region of the head of a mammal (showing the ear region only). (A. S. Romer, The Vertebrate Body, 3d ed., Saunders, 1962)

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from article Ear (vertebrate)

Inner ear of a mammal. (a) Cross section of a single turn of the cochlea. (b) Organ of Corti. (After D. Webster and M. Webster, Comparitive Vertebrate Morphology, Academic Press, 1974)

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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 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. (After D. B. Fogel, Applying evolutionary programming to selected traveling…

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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 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 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 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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from article Eye (invertebrate)

Highly developed eyes at anterior end of pelagic marine annelid Alciopidae. (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)

Scallop Argopecten with one valve removed showing ocelli along the margin of the mantle. (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)

Longitudinal section through the tubelike anterior median eye of jumping spider Salticus. (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)

Octopus 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)

Two ommatidia from compound eye of crayfish Astacus. (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)

Compound eye adapted for opposition image formation. Light rays from points a, b, and c. (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)

Compound eye adapted for superposition image formation. The light from points a, b, and c is concentrated on an ommatidium. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed.,…

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from article Rhinoceros

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from article Ferret

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from article Physiological acoustics

Schematic outline of the central auditory pathways. Numbers indicate the number of neurons from the cochlea. (After S. S. Stevens, ed., Handbook of Experimental Physiology, John Wiley and Sons, 1951)

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from article Physiological acoustics

Distribution of frequency maxima along the basilar membrane. Numbers give frequencies in hertz. Length of basilar membrane = 32 mm, width = 0.04 mm at base, 0.50 mm at apex. (After O. Stuhlmann, An Introduction to Biophysics, John Wiley and Sons,…

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from article Physiological acoustics

Isoamplitude curves of the dc receptor potential within one guinea pig inner hair cell of the basal region. Q10 is a measure of the width of each curve, equal to the center frequency divided by the bandwidth at 10 dB above threshold. (After I. J.…

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from article Physiological acoustics

Intensity/rate functions of two cat cochlear nerve fibers tuned to (a) 2.2 kHz and (b) 10.6 kHz. (After W. D. Keidel and W. D. Neff, eds., Handbook of Sensory Physiology, Springer, 1975)

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from article Physiological acoustics

Tuning curves of a number of nerve fibers in the cat cochlear nerve. (After N. Y.-S. Kiang, Discharge Patterns of Single Fibers in the Cat's Auditory Nerve, MIT Res. Monogr. 35, MIT Press, 1965)

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