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Heart-Rate Monitor

This project uses a sensitive light-detecting resistor to detect small changes in the light beaming through your finger as your blood pumps through tiny arteries in the finger. This device is not the same as the heart-rate monitors typically used in…

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from article Information processing (psychology)

The four major lobes of the cerebral cortex, that is, the frontal, parietal, temporal, and occipital lobes, are responsible for different aspects of information processing. (Copyright © McGraw-Hill Education)

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from article Information processing (psychology)

Horizontal associative memory with a serious associative interference problem (who plays tennis—John, Peter, or both?) and no encoding of where each proposition begins and ends. (Copyright © McGraw-Hill Education)

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from article Information processing (psychology)

Vertical associative memory where concepts are grouped into phrases and propositions by associating each concept to a higher-order node that represents the entire group. (Copyright © McGraw-Hill Education)

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from article Octopoda

An octopod swimming in the ocean. (Credit: Getty Images/iStockphoto)

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from article Octopoda

Hapalochlaena maculosa, the Southern or lesser blue-ringed octopus, has vivid, small blue rings on its body and arms, highlighted with black outlines. Location: Mrs. Watson's Bay, Lizard Island, Great Barrier Reef, Australia. (Credit: Clyde F. E.…

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from article Octopoda

Hapalochlaena fasciata, the blue-lined octopus, has vivid blue lines on its body and rings on its arms, highlighted with black outlines. Location: Long Reef, New South Wales, Australia. (Credit: Clyde F. E. Roper)

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from article Octopoda

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from article Polyplacophora

Chiton on a rock surface. (Photo courtesy of the NOAA Okeanos Explorer Program, National Oceanic and Atmospheric Administration)

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from article Polyplacophora

Polyplacophoran mollusk (chiton): (a) dorsal view; (b) ventral view.

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from article Pituitary gland disorders

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from article Pituitary gland disorders

Infarction (obstruction of the blood supply) of the pituitary gland. This pituitary gland is almost entirely infarcted. Only a thin rim of viable cells remains (arrow). Pituitary infarcts can occur during pregnancy (Sheehan's disease) or as a result…

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from article Aconchulinida

Aconchulinida. (a) Penardia cometa. (b) Penardia mutabilis.

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from article Phonoreception

Generalized sketch of the vertebrate labyrinth. The three cristae, macula ultriculi, and macula sacculi are always present in vertebrates, and the other endings appear as indicated, with a few exceptions.

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from article Phonoreception

Diagram (from above) of the two labyrinths of an ostariophysan fish and their connections with the swim bladder through the Weberian ossicles.

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from article Phonoreception

Simplified diagram of the frog ear.

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from article Phonoreception

Diagram of the ear of a snake. The nonauditory parts and endings are not shown.

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from article Phonoreception

Auditory sensitivity of a wood turtle (Clemmys insculpta), as shown by the potentials produced in its ear by sounds. The curve shows the sound pressure necessary to produce a potential of 0.3 microvolt.

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from article Phonoreception

Graph showing threshold sensitivity in the bullfinch (mean of four birds). (Credit: J. Schwartzkopff)

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from article Phonoreception

Auditory thresholds in primates. The curves show the sound pressures that are barely audible for humans, chimpanzees, rhesus monkeys, and marmosets.

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from article Phonoreception

Diagram of the ear of a grasshopper.

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from article Phonoreception

Auditory thresholds of the katydid (Conocephalus strictus). Sensitivity is greatest in the 7000–60,000-Hz region. (Credit: E. G. Wever and J. A. Vernon)

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from article Siphonaptera

Head of Spilopsyllus cuniculi (rabbit flea), with extended mouthparts.

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from article Neandertals

Neandertal cranium excavated from Forbes' Quarry, Gibraltar. Note the pronounced brow ridges, large braincase, and receding forehead. (Credit: Clive Finlayson/Gibraltar Museum)

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from article Neandertals

Gorham's Cave, Gibraltar, is the last known site of Neandertal occupation, being dated possibly to 30,000 years ago. (Credit: Clive Finlayson/Gibraltar Museum)

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from article Neandertals

Reconstructed skull of a Neandertal from the cave at La Chapelle-aux-Saints, France. (Credit: Illustration adapted from an original drawing by M. F. Ashley Montagu)

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from article Notch signaling

Notch-ligand interactions. Two Notch ligands, Delta and Serrate, are shown on the signal-sending cell (left). These ligands are distinguished by differing numbers of EGF-like repeats (indicated by the light boxes) and an extracellular cysteine-rich…

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from article Folic acid

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from article Digenea

Diagrams of various adult types of digenean trematodes. (After R. M. Cable, An Illustrated Laboratory Manual of Parasitology, Burgess, Minneapolis, 1940)

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from article Digenea

Digenean trematode life cycle. (After R. M. Cable, An Illustrated Laboratory Manual of Parasitology, Burgess, Minneapolis, 1940)

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from article Urinary bladder

Light micrograph of the healthy transitional epithelium tissue (stained by hematoxylin and eosin) of a urinary bladder. The transitional epithelium is a type of tissue consisting of multiple layers of epithelial cells, which can contract and expand.…

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from article Urinary bladder

Types of tubal bladders: (a) duplex; (b) bilobed; (c) simplex, with ureters united; (d) simplex, with separate ureters. (Credit: H. E. Walter and L. P. Sayles)

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from article Learning

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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.…

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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:…

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from article Ctenothrissiformes

A Cretaceous ctenothrissiform fossil, Ctenothrissa sp. (order Ctenothrissiformes), on a limestone matrix found in Lebanon. Size: 90 mm (3.5 in.). (Photo courtesy of The Virtual Fossil Museum)

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from article Lung

Human lungs. (a) The trachea bifurcates as the right and left primary bronchi that enter each lung. The bronchi subdivide further to form the bronchial tree. (b) Color-coded view of the major branches of the bronchial tree. (Copyright © McGraw Hill)

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from article Animal testing

Mice are the most commonly used vertebrate species in animal testing and research. (Credit: Dolores Bonaparte)

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from article Animal testing

The use of animals in biomedical research remains essential, but the handling of these sentient beings must be done humanely to minimize and prevent animal harm. (Credit: U.S. Department of Agriculture)

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from article Circadian clock (plants)

Three-module circadian clock system.

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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…

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from article Acari

Parasitiformes body plan. Lateral view of a predatory adult female Mesostigmata showing major body regions and important structures. Scale bar = 0.1 mm (0.004 in.). (Scanning electron micrograph by D. E. Walter)

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from article Acari

Acariformes body plan. (a) Adult female Oribatida (Sarcoptiformes) in lateral view showing major body regions and important structures. (b) Hexapod larva (Trombidiformes): dorsal view of a chigger, a parasite of vertebrates. (c) Octopod deutonymph…

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from article Anthrax

A color-enhanced scanning electron micrograph showing splenic tissue from a monkey with inhalation anthrax. Rod-shaped bacilli of Bacillus anthracis (yellow) and an erythrocyte (red) are shown. (Credit: Arthur Friedlander/National Institute of…

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from article Anthrax

Micrograph (stained with hematoxylin and eosin) showing submucosal hemorrhage in the small intestine of a person fatally affected by gastrointestinal anthrax. (Credit: Marshal Fox/Centers for Disease Control and Prevention)

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from article Neuron

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from article Mutagens and carcinogens

Arsenic is a known carcinogen. In this graphical example, more than half of the mice exposed to arsenic in their drinking water [at concentration levels of 50 and 500 parts per billion (ppb)] showed increased incidences of lung tumors (compared to a…

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from article Mutagens and carcinogens

Proflavin is a chemical disinfectant agent against bacteria, causing mutagenic DNA changes (such as the insertion or deletion of a DNA base pair). However, it is carcinogenic in mammals. Thus, it is used only for the disinfecting of surfaces or for…

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from article Mutagens and carcinogens

Model of carcinogenesis. Changes often occur in the growth properties of normal cells, leading to cancer cells that are not responsive to normal regulatory controls and can eventually give rise to a visible neoplasm or tumor. The main stages of the…

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from article Autophagy

Modes of autophagy in yeast and mammalian cells. Macroautophagy involves the uptake of cytoplasm at a site away from the lysosome or vacuole. The origin of the sequestering membrane is not known, but it likely includes multiple sources such as the…

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from article Autophagy

Basic steps involved in macroautophagy, shown with the structural intermediates. See the text for full details.

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from article Autophagy

The cytoplasm-to-vacuole targeting (Cvt) pathway is an example of selective autophagy. The schematic illustrates the steps of the Cvt pathway and also shows electron micrographs of the sequestration event. Precursor aminopeptidase I (prApe1) forms a…

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from article Autophagy

Atg8 tagged with white fluorescent protein (GFP-Atg8) can be used to monitor autophagosome formation. Cells in growing conditions (for example, in the presence of nitrogen; +N) carry out a basal level of macroautophagy and typically display a single…

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from article Cell cycle

Phases of the eukaryotic cell cycle. Interphase is subdivided into three phases: gap phase 1 (G1), synthesis (S), and gap phase 2 (G2). M phase, which follows interphase, consists of mitosis (nuclear division) and cytokinesis (cell division). G0…

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from article Cell cycle

During cytokinesis (cell division), the cell pinches into two parts between the separated daughter nuclei. At the end of this process, the two daughter cells often remain tethered by a thin "midbody" of microtubules. Once this midbody breaks, the…

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from article Cell cycle

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from article Pituitary gland

The pituitary, also known as the hypophysis, is a pea-sized gland situated at the base of the brain. The hypothalamus is designed and anatomically positioned to receive a diversity of messages from external and internal sources that can be…

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from article Pituitary gland

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from article Salicylate

Chemical structures of (a) salicylate, the conjugate base of (b) salicylic acid, and the nonsteroidal anti-inflammatory drug (NSAID) (c) acetylsalicylic acid (aspirin).

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from article Meningococcus

A photomicrograph reveals the presence of the bacterium Neisseria meningitidis, which can be pathogenic, leading to meningococcal meningitis. (Credit: James Volk/Centers for Disease Control and Prevention)

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from article Haplosporida

Spore of Urosporidium fuliginosum.

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from article Haplosporida

Stages in the development of Icthyosporidium giganteum.

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from article Oxygen toxicity

The dual effect of oxygen on biologic activity. Organisms that avail themselves of the enormous metabolic advantages provided by dioxygen (O2) must defend themselves against its toxicity. (Copyright © McGraw Hill)

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from article Gibberellin

Carbon skeleton of ent-gibberellane showing the carbon numbering system and ring designations. (Credit: Peter Hedden)

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from article Gibberellin

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…

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from article Gibberellin

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…

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from article Gibberellin

Illustration of a 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…

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from article Gibberellin

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…

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from article Urodela

A typical member of the order Urodela: the longtail salamander (Eurycea longicauda). (Credit: Ryan Hagerty/U.S. Fish and Wildlife Service)

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from article Urodela

Southern dwarf siren (Pseudobranchus axanthus), which has undergone limb degeneration and retains only tiny forelimbs. (Credit: U.S. Geological Survey)

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from article Urodela

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from article Urodela

California tiger salamander (Ambystoma californiense). (Credit: John Cleckler/U.S. Fish and Wildlife Service)

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from article Urodela

The two-toed amphiuma salamander (Amphiuma means). (Credit: Southeast Ecological Center, U.S. Geological Survey)

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from article Urodela

The northern red salamander (Pseudotriton ruber ruber) is a member of the family Plethodontidae. (Credit: Alicia Lafever/U.S. National Park Service)

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from article Spinal cord disorders

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from article Thirst and sodium appetite

Regulation of cellular water. ADH = antidiuretic hormone.

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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…

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from article Mutation

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from article Mutation

The karyotype (complement of chromosomes) characteristic of an individual with Down syndrome. Note that there are three copies of chromosome 21; this mutation is known as trisomy 21. (Copyright © McGraw-Hill Education)

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from article Mutation

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from article Antibody

Computer-generated models of (a) an antibody molecule and (b) a metalloantibody molecule. The amino acid side chains have been omitted for clarity. In panel (a), blue indicates the constant regions of light chains and heavy chains; white, the…

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from article Antibody

Typical antibody molecule. There are two H and two L chains, held together by disulfide bonds, and the N-terminal variable domains are shown in dark color. The molecule is bilaterally symmetrical, so two identical epitopes are bound. The…

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from article Antibody

Domain structure of three typical light (L) and heavy (H) chains shows their similarities and differences. The amino- and carboxy-terminals of the chains are marked N and C, respectively. The flexible hinge region is also shown. At the N-terminals,…

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from article Chamois

Alpine chamois (Rupicapra rupicapra). (Photograph courtesy of Brent Huffman/Ultimate Ungulate Images)

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from article Bioassay

In conducting bioassays, researchers often employ laboratory culture tests, which use, for example, bacteria cultured in a petri dish (usually to model an effect on the organism of interest or on some basic cellular function). (Credit:…

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from article Amniota

Basic types of vertebrate eggs.

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from article Amniota

Embryo developing in amniote eggs.

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from article Human genetics

A genetic map is a type of chromosome map that shows the relative locations of genes and other important features. The map is based on the idea of linkage (that is, the closer that two genes are to each other on the chromosome, the greater is the…

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from article Human genetics

Digital illustration of the human karyotype. The karyotype is the complete set of chromosomes in an organism. (Credit: Science Photo Library/Alamy Stock Photo)

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from article Human genetics

The double-helix structure of a DNA molecule. (Credit: Darryl Leja/National Human Genome Research Institute)

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from article Human genetics

Simplified diagram showing (a) the structure of a gene, (b) the mature messenger RNA (mRNA) after the two intervening sequences have been spliced out and the “cap” and “tail” added, and (c) the polypeptide translated from the mRNA. (Copyright ©…

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from article Human genetics

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from article Human genetics

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from article Human genetics

Typical pedigree pattern of a rare autosomal-dominant trait: classical achondroplastic dwarfism. Individuals with this anomaly, caused by a defect in bone growth, have extremely short arms and legs, but are otherwise normal. I–IV are generations;…

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from article Human genetics

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from article Human genetics

Typical pedigree patterns of a sex-linked recessive trait: hemophilia A. (a) Only males are affected and usually come from unaffected mothers, who often have affected fathers or brothers. (b) An affected female can result from an affected father and…

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from article Mecoptera

Male scorpion fly (Panorpa), order Mecoptera.

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from article Developmental genetics

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from article Nerve

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from article Microbiome

Profile of the human microbiome by anatomical niche. DNA sequence analysis reveals the relative abundances of the six most abundant bacterial phyla in the human body. The phyla shown represent 99.6% of the sequences sampled. Cyanobacteria were…

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