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View of an area of deforestation in Central Kalimantan, Indonesia. In this case, the land is being cleared to develop areas for intensive rice production. (Credit: Australian National University)

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from article Deforestation

The relationship between forest and nonforest (other) land. Preservation of forest lands includes reforestation and natural regeneration. However, deforestation and natural events can lead to nonforest land. Afforestation (the act or process of…

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from article Deforestation

Natural forest areas (in hectares; 1 hectare = 2.47 acres) in various climatic domains (boreal/polar, temperate, subtropical, and tropical) from 1990 to 2015. The data are derived from the Global Forest Resources Assessment 2015 by the Food and…

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from article Deforestation

Former rainforest in northern Queensland, Australia, that was deforested in the early 1900s and is now used for pasture. (Credit: Rodney Keenan)

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from article Deforestation

Aerial view of deforestation in the Amazon region of Brazil. Clearing of trees in the Amazon rainforest has resulted in the elimination of natural resources and numerous species. (Credit: Luoman/Getty Images)

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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 Ferret

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from article Sexually transmitted diseases

Acquired immune deficiency syndrome (AIDS) is a sexually transmitted disease caused by the human immunodeficiency virus (HIV). In this image, a human T cell (blue) is under attack by HIV (yellow), hampering the effectiveness of the body's immune…

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from article Sexually transmitted diseases

Prevalence of Chlamydia trachomatis (the most-common sexually transmitted bacterial pathogen) among individuals aged 14 to 39. The prevalence varies by sex, race/ethnicity, and age. Error bars indicate 95% confidence intervals. (Credit: U.S. Centers…

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from article Sexually transmitted diseases

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from article Tetanus

Photomicrograph showing endospores forming at the ends of Clostridium tetani bacterial cells, which are shaped like small tennis rackets. Clostridium tetani is the causative agent of tetanus. (Credit: Lisa Burgess; copyright © McGraw Hill)

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from article Syphilis

Syphilis is caused by Treponema pallidum, which is a corkscrew-shaped motile bacterium (spirochete). (Credit: National Institute of Allergy and Infectious Diseases, National Institutes of Health)

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from article Rabies

Negri bodies (cytoplasmic inclusion bodies) in infected nerve cells in a dog brain are characteristic cellular changes that occur as a result of rabies encephalitis. (Credit: G. Heid/Centers for Disease Control and Prevention)

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from article Rabies

Schematic model of a rabies virus showing the surface glycoprotein spikes (projections) extending from the lipid envelope that surrounds the internal nucleocapsid and the matrix protein lining the envelope. The nucleocapsid comprises the single RNA…

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from article Echocardiography

Two-dimensional echocardiogram from a position near the apex of the ventricles of a human heart. The left ventricle is on the right, separated from the left atrium below by the mitral valve. The right ventricle is on the left, and the right atrium…

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from article Microbiology

Two important types of microbes are bacteria (Mycobacterium tuberculosis; left) and fungi (Histoplasma capsulatum; right). [Credit: Janice Haney Carr/Centers for Disease Control and Prevention (left); Libero Ajello/Centers for Disease Control and…

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from article Microbiology

Viruses (Herpes simplex; left) and protozoa (Oxytricha trifallax; right) are microorganisms studied by microbiologists. [Credit: Centers for Disease Control and Prevention (left); National Human Genome Research Institute (right)]

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from article Bean

Pods of soybean plants (Glycine max). (Credit: Howard F. Schwartz/Colorado State University)

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from article Bean

Red dry bean pods (Phaseolus vulgaris). (Credit: Howard F. Schwartz/Colorado State University)

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from article Bean

Different stages of maturity of the seeds of light red kidney beans in opened pods. (Credit: Howard F. Schwartz/Colorado State University)

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from article Bean

Symptoms of Pythium disease on Phaseolus vulgaris (common bean) plants. (Credit: University of Georgia Plant Pathology Archive)

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from article Bean

Anthracnose, caused by Colletotrichum lindemuthianum, on bean pods. (Credit: U.S. Department of Agriculture Cooperative Extension Series, Clemson University)

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from article Chronic fatigue syndrome

Chronic fatigue syndrome is more widespread among women. (Credit: Sirikorn Thamniyom/Shutterstock)

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from article Bronchiolitis obliterans organizing pneumonia (BOOP)

Colorized computerized tomography (CT) scan showing alveolar airspace consolidation and nodular opacities characteristic of bronchiolitis obliterans organizing pneumonia (BOOP). (Credit: Sara Al-Ghanem)

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from article Vegetation and ecosystem mapping

Terrestrial major habitat types.

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from article Taiga

Siberian mountain taiga. (Credit: M. Valerii/Shutterstock)

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from article Taiga

Schematic profile of the three main subzones of the North American taiga, showing the main forest assemblages on three of the more important landform types: (a) northern taiga; (b) middle taiga; (c) southern taiga. (Copyright © McGraw-Hill Education)

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from article Medical dialysis

A patient receiving dialysis. (Credit: Science Photo Library/Alamy Stock Photo)

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from article Medical dialysis

Illustration of a patient receiving a hemodialysis treatment using a hemodialysis machine with the blood lines connected to the patient's left arm. (Credit: BSIP SA/Alamy Stock Photo)

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from article Medical dialysis

Illustration depicting how peritoneal dialysis can be performed using gravity to direct peritoneal dialysis fluid into the abdomen via a catheter. (Credit: National Institute of Diabetes and Digestive and Kidney Diseases)

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from article Zika virus disease

A female Aedes aegypti mosquito acquiring a blood meal on a human. This type of mosquito is the primary vector responsible for the transmission of the Zika virus. (Credit: James Gathany/Centers for Disease Control and Prevention)

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from article Zika virus disease

Babies born with microcephaly have smaller head sizes than normal. There is an association between babies born with neurological complications, such as congenital microcephaly, and Zika virus infection. (Credit: Centers for Disease Control and…

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from article Zika virus disease

Countries and territories that have been affected by Zika virus transmission. Color key: dark purple, country or territory that has reported locally acquired, mosquito-borne Zika cases (past or current); light purple, area with low likelihood of…

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from article Zoonoses

The Rocky Mountain wood tick (Dermacentor andersoni) is the etiologic agent of Rocky Mountain spotted fever. (Credit: Christopher Paddock/Centers for Disease Control and Prevention)

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from article Zoonoses

Cryptococcosis of a lung in a patient with acquired immune deficiency syndrome (AIDS). Histopathology of the lung shows a widened alveolar septum containing a few inflammatory cells and numerous yeasts of Cryptococcus neoformans. The inner layer of…

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from article Zoonoses

Light micrograph of a dog roundworm (Toxocara canis). (Credit: olgaru79/Shutterstock)

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from article Forest ecosystem

Forest in Moran State Park on Orcas Island, Washington. (Credit: Chris Willig)

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from article Forest ecosystem

Forest fire in No Name Creek area of Colorado. (Credit: Andrea Booher/FEMA)

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from article Forest ecosystem

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

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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.…

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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)

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from article Forest ecosystem

Belowground food web. (Credit: Elaine Ingham)

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from article Medical waste

The uniform international biohazard symbol.

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from article Huntington's disease

Huntington's disease is a hereditary disorder that affects approximately five to ten of every 100,000 persons. The average age at onset is between 35 and 40 years. Invariably fatal, the disease progresses gradually over time. (Copyright ©…

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from article Belladonna

Close-up view of the belladonna plant (Atropa belladonna), showing the leaves and berries, which are toxic. (Credit: Leo Michels)

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from article Pharmacy

Pharmacy is the science dealing with the preparation and dispensing of medicinal or therapeutic drugs. (Credit: Sanchai Rat/Shutterstock)

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from article Hepatitis C virus

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from article Hepatitis C virus

Natural history of chronic hepatitis C. It is presumed that liver fibrosis progresses in a linear course from the time of acquisition of the infection to the development of cirrhosis. Stages of fibrosis are from the METAVIR (meta-analysis of…

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from article Hepatitis C virus

The genomic structure of hepatitis C virus (HCV) and potential targets for therapy. Through analysis of the genomic structure of HCV, additional therapies (for example, serine protease inhibitors, helicase inhibitors, and RNA polymerase inhibitors)…

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from article Surgery

Medical personnel performing a surgical procedure in a modern operating room. (Credit: OJO Images Limited/Alamy Stock Photo)

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from article Surgery

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from article Surgery

Close-up view of a surgeon organizing the instruments required for an operation. (Credit: ER Productions Limited/Blend Images)

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from article Surgery

A medical operation involving a robot. Robotic surgery is being implemented to perform procedures that once required the presence of an expert surgeon. (Credit: Master Video/Shutterstock)

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from article Food allergy

Children (under the age of 18) who experience food allergies are more likely to experience other allergic conditions, including asthma (black), eczema/skin allergy (blue), and respiratory allergy (green). (Credit: National Center for Health…

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from article Food allergy

Allergic responses (immunological responses mediated by the IgE class of immunoglobulins) can be caused by certain foods. In a person with allergies, mast cells will be coated with IgE against one or a few antigens (allergens) that, upon entering…

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from article Food allergy

Peanuts are a common trigger of food allergies in both adults and children. (Credit: Christian Jung/Shutterstock)

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from article Sport-related concussion

Sport-related concussion is among the most frequent injuries experienced by athletes participating in contact and collision sports, including football. (Credit: Skynesher/Getty Images)

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from article Sport-related concussion

Medical imaging and scanning techniques can identify the brain areas affected by a sport-related concussion. (Credit: Puwadol Jaturawutthichai/Shutterstock)

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from article Sport-related concussion

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from article Prairie dog

Black-tailed prairie dogs (Cynomys ludovicianus). (Photo by Ron Singer, U.S. Fish and Wildlife Service)

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from article Streptococcus pneumoniae (pneumococcus)

Photomicrograph of Streptococcus pneumoniae bacteria that have been grown from a blood culture. Streptococcus pneumoniae is the most common bacterial cause of pneumonia in adults, but various forms of the bacteria have acquired resistance to…

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from article Desertification

Overgrazing on North American rangelands contributes to soil compaction and alters the composition of vegetation. (Credit: Thomas Wikle)

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from article Desertification

Desertification can be accelerated by cultivation in areas better suited for herding, such as this field in Ethiopia. (Credit: Thomas Wikle)

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from article Desertification

Grazing animals have contributed to desertification in Africa’s Sahel region. (Credit: Thomas Wikle)

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from article Binocular vision disorders

Exotropia (simulated photographically) is a misalignment of the eyes. In this type of manifest strabismus, one or both eyes turn outward. (Credit: Kerri McTigue)

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from article Binocular vision disorders

Esotropia (crossed eyes; simulated photographically) is a type of manifest strabismus in which one or both eyes turn inward. (Credit: Kerri McTigue)

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from article Coronavirus

Highly magnified, digitally colorized electron micrograph of MERS-CoV virions (red color). (Credit: National Institute of Allergy and Infectious Diseases)

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from article Coronavirus

Illustration of SARS-CoV-2. Note the spike (S) proteins protruding from the surface of the coronavirus, which impart the look of the Sun's corona or crown. S proteins bind to host cell receptors for entry or infection of the cell. (Credit: Alissa…

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from article Coronavirus

Classification of coronaviruses. Human coronaviruses are shown in bold type. Highly pathogenic coronaviruses in humans are shown in red type. Human coronaviruses belong to two different genera: Betacoronavirus and Alphacoronavirus. (Credit: Teri…

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from article Coronavirus

Primary and intermediate hosts of human coronaviruses showing cross-species transmission. No concrete evidence exists about the intermediate host (or hosts) of HCoV NL63 and HCoV HKU1. The years of isolation or emergences of each viral strain are…

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from article Laminariales

Laminaria: (a) sporophyte; (b) cross section of blade, showing a sorus of unilocular sporangia interspersed with sterile hairs (paraphyses); (c) zoospore; (d) male gametophyte with antheridia; (e) antherozoid (sperm); (f) female gametophyte with…

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from article Laminariales

Giant kelp (Macrocystis pyrifera) can grow up to 0.6 m (2 ft) per day. Note the series of frond blades, with each subtended by a bladder. (Photo courtesy of Charlotte Stevenson, University of Southern California Sea Grant, Los Angeles)

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from article Obesity

Map of the United States showing the growing prevalence of obesity. In general, the South had the highest prevalence of obesity, followed by the Midwest, the Northeast, and the West. (Credit: U.S. Centers for Disease Control and Prevention)

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from article Obesity

Colored scanning electron micrograph (SEM) of fat (adipose) tissue. The round fat cells (adipocytes) are surrounded by collagen fibers. Lipid is colored purple. Empty cells are seen at top right. (Credit: Science Photo Library/Alamy Stock Photo)

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from article Obesity

Estimated percentage of obesity according to gender. Dark color indicates the percentage of obesity in females; light color indicates the percentage of obesity in males. (Credit: National Institute of Diabetes and Digestive and Kidney Diseases,…

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from article Enzyme inhibition

Enzyme inhibition often works by preventing a substrate from attaching to an active enzyme. In this example, E1 is one of three sequential enzymes that will convert a substrate (S) into a product (P). However, the product that is created can then…

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from article Enzyme inhibition

Two types of reversible enzyme inhibition. (Left) In competitive inhibition, the inhibitor interferes with the active site of the enzyme, so the substrate is unable to bind to it. (Right) In noncompetitive inhibition, the inhibitor changes the…

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from article Alpine vegetation

A windswept and stunted whitebark pine (Pinus albicaulis) growing among the alpine vegetation on Mount Washburn in Yellowstone National Park, Wyoming, United States. (Credit: R. G. Johnsson)

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from article Alpine vegetation

Alpine vegetation and flowers blooming in Mount Rainier National Park in Washington, United States. (Credit: National Park Service)

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from article Killer whale

Killer whales (Orcinus orca) in the waters off Alaska. (Credit: David Ellifrit/Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration)

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from article Killer whale

The tail of a killer whale. (Credit: Janice Waite/Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration)

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from article Radiography

Relation of the penetration characteristics of x-rays to the type and thickness of various materials.

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from article Radiography

Geometry of radiographic image formation. F = size of focal spot of x-ray tube; d = distance from focal spot to specimen (lead plate); t = distance from plate to film; U = unsharpness.

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from article Radiography

Penetrameter. The windows show plan views and cross sections of the penetrameter plates. T is plate thickness; t is object thickness.

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from article Radiography

Chest radiograph of foundry worker made with intense beam from rotating-target x-ray tube, showing nodules in lungs which are caused by silicosis, and shadows of skeleton, heart, and stomach.

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from article Radiography

Thermal neutron radiograph of an investment-cast turbine blade, showing image of residual ceramic. (Industrial Quality, Inc.)

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from article Paleopathology

The fused spine and ribs in a case of ankylosing spondylitis from an adult male human found at a burial site near the Kuskokwim River, Alaska. (Credit: Department of Anthropology, National Museum of Natural History, Smithsonian Institution Catalog…

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from article Paleopathology

Pottery figurine of an achondroplastic dwarf from an archeological site in Tachina, Esmeraldas, Ecuador, dated between 500 BCE and 500 CE. (Credit: Department of Anthropology, National Museum of Natural History, Smithsonian Institution Catalog No.…

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from article Paleopathology

Sword trauma that removed part of the left upper jaw and the right lower jaw so that no remaining teeth were in contact between the jaws. The adult male human survived this injury. The skull is from an archeological burial site near the Stewart…

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from article Paleopathology

Destruction of the lower portion of the fourth lumbar vertebra (arrow), probably caused by tuberculosis, from a young male human skeleton found at the archeological burial site of Bâb edh-Dhrâ in Jordan, dated to approximately 3300 BCE. (Credit:…

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from article Paleopathology

The effect of scurvy on the right side of the cranium of an 11-year-old human child from the archeological site of Pachacamac, Peru. (Credit: Department of Anthropology, National Museum of Natural History, Smithsonian Institution Catalog No. 266599)

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from article Gastrointestinal tract disorders

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from article Gastrointestinal tract disorders

A cross section of a peptic ulcer, illustrating the four layers: fibrin (black arrowhead), neutrophils (black arrow), granulation tissue (white arrowhead), and fibrosis (white arrow). (Copyright © McGraw-Hill Education)

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from article Gastrointestinal tract disorders

Small intestine biopsy showing villous atrophy, which is found in individuals affected by celiac disease. (Credit: Ed Uthman/National Institutes of Health)

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from article Extremophile

Extremophile (psychrophile) bacteria (Carnobacterium pleistocenium) retrieved from the ice of a frozen Alaskan pond dating back approximately 32,000 years. (Credit: Marshall Space Flight Center, National Aeronautics and Space Administration)

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from article Mouth disorders

Stages involved in the formation of periodontitis: (left) normal, nondiseased state of teeth, bone, and the gingiva (gum tissue); (middle) calculus buildup and early gingivitis (inflammation of the gums); (right) late-stage periodontitis, with…

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from article Forest fire

Exclusion of fire by humans has contributed to dramatic large blazes in the western United States. (Credit: Kari Greer)

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from article Forest fire

Crown fire in northern California. (Credit: Kari Greer)

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