Phase Contrast

Transparent specimens often appear remarkably different when they are comparatively observed under positive and negative phase contrast illumination. In positive phase contrast, specimen intensity is manifested by relatively medium to dark gray features, surrounded by a bright halo, and superimposed on a lighter gray background. Alternatively, in negative phase contrast, the specimen often appears much brighter on a dark gray background and the accompanying halos are also dark (much darker than the background). This digital image gallery compares identical viewfields of a wide variety of specimens illuminated with both positive and negative phase contrast.

Arrowroot (Maranta arundinacea) Starch Granules

Use of arrowroot plant starch is a long-standing English tradition. Spice purveyors as far back as the 1700s understood the benefits of arrowroot starch and fought over rights to the crops. Since true arrowroot, known formally as Maranta arundinacea, is cultivated only in St. Vincent, there often was not enough product to meet demand. Even today, attaining true arrowroot starch is somewhat difficult. Products often labeled arrowroot are usually a less expensive version of a similar root, which originates in Brazil or China.

  • Arrowroot (Maranta arundinacea) Starch Granules - Positive

    Positive

    Arrowroot (Maranta arundinacea) Starch Granules - Positive

    Use of arrowroot plant starch is a long-standing English tradition. Spice purveyors as far back as the 1700s understood the benefits of arrowroot starch and fought over rights to the crops. Since true arrowroot, known formally as Maranta arundinacea, is cultivated only in St. Vincent, there often was not enough product to meet demand. Even today, attaining true arrowroot starch is somewhat difficult. Products often labeled arrowroot are usually a less expensive version of a similar root, which originates in Brazil or China.
  • Arrowroot (Maranta arundinacea) Starch Granules - Negative

    Negative

    Arrowroot (Maranta arundinacea) Starch Granules - Negative

    The reasons arrowroot starch is so highly sought after are numerous. Arrowroot stems contain complex carbohydrates with a molecular structure that enables thickening to occur at a lower cooking temperature than most starches. This means the starch is less likely to burn, a bonus for beginning cooks and experienced chefs alike. Also, because arrowroot contains high levels of amylopectin, the starch creates wonderful, clear glazes, gravies and sauces. As an added benefit, arrowroot starch is the easiest starch for humans to digest, and can be used to enhance digestion and aid in hangover recovery.

Asbestos Fibers

Should it stay or should it go? This controversial question regarding asbestos and its removal has no clear-cut answer and is the subject of great debate. Asbestos is the generic name for six naturally occurring mineral fibers, which have been commonly used in various building materials as insulation and as a fire-retardant.

  • Asbestos Fibers - Positive

    Positive

    Asbestos Fibers - Positive

    Asbestos was formerly considered a prime component for commercial products due to its strength, elasticity, low electrical conductivity, and resistance to both heat and chemicals. However, recent scientific studies have thrust asbestos into a negative light and many governmental restrictions have been placed on its use. High death rates from lung diseases and cancers of the chest and abdomen have been recorded among asbestos workers who did not wear protective gear. Asbestos is also a key suspect in the death of a large number of miners in North America. Yet, the highest lung cancer rates in the miners occurred in the group who were also smokers, making results analysis difficult and scientific agreement unlikely.
  • Asbestos Fibers - Negative

    Negative

    Asbestos Fibers - Negative

    Adding to the controversy is the fact that the term asbestos refers to a variety of mineral fibers. Some researchers believe that different health hazards accompany different types of asbestos and should, therefore, be regulated separately. The fiber bundles of asbestos easily separate into long, thin individual fibers when disturbed. Once breathed into the lungs, a fiber must be able to endure the lung fluids in order to stay intact, accumulate, and cause harm. While the durability of the different types of asbestos is being studied, all are under suspicion and should be handled with care. It is generally considered best to leave asbestos material that is undamaged alone and to only have it removed by qualified contractors.

Blue Mold (Peronospora tabacina) Fungus

The blue mold fungus produces spores that are the result of both sexual and vegetative reproduction. Resting spores, or oospores, are produced through sexual reproduction and are believed to be involved with long-term survival of the species. Sporangiospores are produced vegetatively as the mold, in essence, makes clones of itself. Sporangiospores can develop by the millions within hours after a tobacco plant is infected, intensifying the need for quick action by farmers who want to save their crops.

  • Blue Mold (Peronospora tabacina) Fungus - Positive

    Positive

    Blue Mold (Peronospora tabacina) Fungus - Positive

    Blue mold is highly weather-sensitive, yet genetically resilient. During intervals of cool, wet, and overcast weather the disease develops and spreads swiftly. In recent years, biologists have begun using meteorological tools to track clouds of these spores traveling on the wind over the Caribbean Sea, Latin America, the continental United States, and Canada. This information is used to predict outbreaks of blue mold, giving tobacco growers an opportunity to protect and treat their crops. Blue mold, however, has proven to be extremely adaptable. New strains of the fungus appear rapidly following release of resistant tobacco varieties and new fungicides.
  • Blue Mold (Peronospora tabacina) Fungus - Negative

    Negative

    Blue Mold (Peronospora tabacina) Fungus - Negative

    The blue mold fungus produces spores that are the result of both sexual and vegetative reproduction. Resting spores, or oospores, are produced through sexual reproduction and are believed to be involved with long-term survival of the species. Sporangiospores are produced vegetatively as the mold, in essence, makes clones of itself. Sporangiospores can develop by the millions within hours after a tobacco plant is infected, intensifying the need for quick action by farmers who want to save their crops.

Budding Hydra

In Greek mythology, the Hydra was a many headed water serpent with deadly breath. The second task of Hercules was to kill this beast, a difficult feat since each time one head was chopped off two more grew in its place. Although hydras, which belong to the phylum Coelenterata, are not quite so dreadful, their appearance and reproductive ability are reminiscent of the mythological creature of the same name.

  • Budding Hydra - Positive

    Positive

    Budding Hydra - Positive

    Hydras are freshwater relatives of saltwater anemones and corals that live in the open sea. Their bodies are tubular, translucent, and may vary in color. Hydras attach to rocks by a single foot on one end. The other end has a small opening, which can ingest nutrients and expel wastes, surrounded by many stinging tentacles. The tentacles are used in a variety of ways to stun, capture, and maneuver prey. Because their bodies are very elastic, hydras can catch and eat animals much larger than themselves.
  • Budding Hydra - Negative

    Negative

    Budding Hydra - Negative

    Although unable to produce new heads, as did the foe of Hercules, hydras can create small replicas of themselves. Hydras produce more hydras through a process called budding. In budding, small hydras, complete with tentacles, grow on the side of a larger hydra and then break off to form new individuals. Hydras can, however, also reproduce sexually. Males produce sperm, which are released into the water near a female to fertilize her eggs. Fertilized eggs become embryos that attach to the side of the female. After the tentacles and mouth are developed, the newly formed hydras then separate from their mother and live independently. Hydras produced sexually are generally more resilient and have a better chance of surviving cold winters than those that developed through budding.

Chinese Hamster Ovary Cell Culture

Commonly, hamsters are thought of as cute, furry, and disposable pets, but the small, rat-like, Chinese hamster serves a totally different function. These rodents are fairly uncommon as pets because they can be difficult to breed. Ironically, the cells of their reproductive organs are what make them so useful to scientists. The Chinese hamster ovary (often abbreviated CHO) tissue is commonly cultured as individual cells in a monolayer and studied worldwide.

  • Chinese Hamster Ovary Cell Culture - Positive

    Positive

    Chinese Hamster Ovary Cell Culture - Positive

    The majority of animal cells exhibit a finite lifetime when isolated and grown in a tissue culture medium that supplies necessary nutrients, salts, and vitamins. Typical vertebrate cells divide between 50 and 100 times before they can no longer carry on cell division and eventually die. Many theories suggest that this limited lifespan is related to the corresponding life cycle of the parent organism from which the cultured cells were derived.
  • Chinese Hamster Ovary Cell Culture - Negative

    Negative

    Chinese Hamster Ovary Cell Culture - Negative

    Occasional changes in the genetic makeup of cultured cells allow them to proliferate indefinitely, making them effectively immortal. Such lines are said to be transformed, and are often used in research as a standardized cell line. Chinese hamster ovary (CHO) cells were introduced in the early 1960s as a viable epithelial cell line containing twin female X chromosomes. The most common type of CHO cells has a nutritional requirement for the amino acid proline, which makes this cell line an ideal candidate for genetic studies.

Ctenoid Fish Scale

The fish most people encounter today are deep-fried, square-shaped and surrounded by a bun. It is almost possible to forget that fish begin their lives covered in scales, rather than a crispy batter shell. Yet, scales are an essential part of fish anatomy, providing these aquatic creatures with external protection from many predators and dangers, if not from man.

  • Ctenoid Fish Scale - Positive

    Positive

    Ctenoid Fish Scale - Positive

    All fish scales, however, are not alike. There are four major groups, one of which is comprised of cycloid and ctenoid scales. The ctenoid variety have a comb-like, spiny posterior edge, their name developing from the Greek word cteno, meaning comb. Conversely, cycloid scales have a smooth posterior edge as their name from the Greek cyclo, meaning circle, implies. Both types of scales, however, consist of two main regions; a rigid surface layer chiefly composed of calcium-based salts, and a deeper fibrous layer consisting mainly of collagen.
  • Ctenoid Fish Scale - Negative

    Negative

    Ctenoid Fish Scale - Negative

    Interestingly, fish scales can be used to estimate the age of a fish. As a fish with cycloid or ctenoid scales grows, its scales also grow. The increase in size of the scales causes the development of growth rings known as circuli. Theses rings are similar to the growth rings in tree trunks. When the weather becomes cool, scale growth slows down and the circuli appear more closely together, leaving a dark band. It is possible to estimate how old a fish is by counting the bands, known as annuli.

Dacron Polyester Fibers

Polyesters may be most memorable as the material used to make sleek and shiny disco clothes during the seventies. Polyester fiber does, however, have more practical uses and may be found in a variety of domestic products, such as mattresses, pillows, seat cushions and custom upholstery.

  • Dacron Polyester Fibers - Positive

    Positive

    Dacron Polyester Fibers - Positive

    All polyesters and other manufactured fibers are not alike. The composition of each fiber is distinct and has its own set of physical characteristics. The United States Federal Trade Commission has defined and generically named man-made fibers, for instance, polyester, nylon, rayon, and spandex. Yet, each fiber in a category may be different as producers chemically and physically modify the basic composition of the generic fiber. Variations produced may provide benefits such as softer feel, brighter color, or greater warmth retention.
  • Dacron Polyester Fibers - Negative

    Negative

    Dacron Polyester Fibers - Negative

    Improved fibers are owned and trademarked by the company that produces them. Dacron is a registered trade name for a polyester fiber made by DuPont. Dacron is especially known for its durability, consistency, and quality. Dacron, unlike natural fibers, is hypoallergenic, non-absorbent, and mildew-resistant. The versatility of synthetic fibers as a whole has warranted them an important and well-deserved place in the textile industry.

Earthworm Nervous System

Earthworms are simultaneous hermaphrodites, with each worm having complete male and female reproductive systems. Although earthworms possess ovaries and testes, they have a protective mechanism against self fertilization and can only function as a single sex at one time. Therefore, they still need to mate with another worm in order to produce offspring. Young earthworms are faithful, but miniature, replicas of the parents and become sexually mature in about three months.

  • Earthworm Nervous System - Positive

    Positive

    Earthworm Nervous System - Positive

    Earthworms are simultaneous hermaphrodites, with each worm having complete male and female reproductive systems. Although earthworms possess ovaries and testes, they have a protective mechanism against self fertilization and can only function as a single sex at one time. Therefore, they still need to mate with another worm in order to produce offspring. Young earthworms are faithful, but miniature, replicas of the parents and become sexually mature in about three months.
  • Earthworm Nervous System - Negative

    Negative

    Earthworm Nervous System - Negative

    Excellent self-healers, earthworms have the ability to regenerate a portion of the body when it is removed or damaged. If the posterior section of a worm is removed, then either a head or tail is regenerated. However, if a head grows back instead of the original tail, then the double-headed worm will starve. Anterior regeneration always results in a tail section being reproduced. Remarkably, portions of several worms can be united to make a single long worm.

Frog Blood Cells

Unlike typical mammalian red blood cells, those from amphibians, such as frogs, contain a DNA-bearing nucleus that is visible in the center of the cell. The circulatory system of amphibians is rather unusual, their hearts having three chambers, two atria, and a single ventricle.

  • Frog Blood Cells - Positive

    Positive

    Frog Blood Cells - Positive

    The design of the amphibian circulatory system is curious because blood accumulates oxygen in the lungs and is then returned to the heart before being pumped into the rest of the circulatory system. Therefore, a mixing between oxygenated and deoxygenated blood occurs as blood returning to the heart from the lungs is mixed with incoming blood from the body. Frogs handle this situation by having a very slow metabolism and by absorbing some oxygen through their skin. In addition, the ventricle does have some directional control over the distribution of the blood.
  • Frog Blood Cells - Negative

    Negative

    Frog Blood Cells - Negative

    The presence of a nucleus in amphibian red blood cells allows researchers easy access to large quantities of amphibian DNA. Frog blood has both a solid and a liquid portion. The liquid plasma carries solid elements such as red and white blood cells. Blood can be collected from frogs and the red blood cells isolated by centrifugation. After removal of the residual plasma, purified cells can be treated with specific enzymes and detergents to digest the cellular envelope and release DNA from its protein complex. The DNA is then useful for scientific studies and experiments.

Fucus Seaweed

Members of this small genus of seaweeds are often seen washed up on the shores of beaches. Commonly called wracks, Fucus has a brown mossy appearance and a typical salty sea-like smell. Some species may have health benefits, which although not scientifically proven, are frequently advertised as key components in nutritional supplements.

  • Fucus Seaweed - Positive

    Positive

    Fucus Seaweed - Positive

    The term seaweed is loosely applied to the many plants found growing in the oceans. Seaweeds, however, are not weeds at all, but marine algae. Marine algae are different from the plants that grow on land because they lack many of the structures typically associated with their terrestrial cousins, such as roots, stems, leaves, and flowers. Yet, both land plants and seaweed are capable of converting the sun's energy into food through the process of photosynthesis. In Fucus and other large brown seaweeds, a structure called the blade contains the specialized cells needed to perform this function. The blade often has a gas bladder, termed a pneumatocyst, attached to it that helps keep the plant near the surface of the water so it can get the sunlight needed for photosynthesis.
  • Fucus Seaweed - Negative

    Negative

    Fucus Seaweed - Negative

    Seaweeds have long served a multiplicity of purposes for man. Mediterranean seaweeds were employed as fodder and as herbal medicine in ancient Greece and Rome. Reports indicate that they may have been used even earlier in China and Japan. Today, seaweeds are used for food, cosmetics, soaps and a wide range of other products. Some Fucus seaweed species are especially popular as of late due to their high iodine content. Iodine is believed to have the ability to stimulate the thyroid gland and, therefore, promote weight loss. Studies, nevertheless, have not provided any conclusive evidence that Fucus has special nutritional benefits, so buyers should beware.

Goniatitic Cephalopod Fossil

Goniatites are an extinct species of ancient marine animal that evolved approximately 400 million years ago. Flourishing in the Devonian period, goniatites now act as important zone, or index, fossils to geologists who use them to identify rocks of that period. All knowledge concerning goniatites derives from fossil records and familiarity with their modern-day relatives.

  • Goniatitic Cephalopod Fossil - Positive

    Positive

    Goniatitic Cephalopod Fossil - Positive

    Despite appearances, goniatites are believed to have been surprisingly mobile. They were cephalopods, similar in body structure to squids and octopuses, which lived in a multi-compartmental shell. The animal only occupied the last chamber and propelled itself by using its tentacles or by squirting water out of its body cavity. The internal chambers of the shell were probably filled with gas, making the animal float and drift in water. Goniatites were especially widespread in the shallow seas that surrounded, and occasionally flooded, deltas in North America, Europe, North Africa and Australia.
  • Goniatitic Cephalopod Fossil - Negative

    Negative

    Goniatitic Cephalopod Fossil - Negative

    The coiled shells of goniatites, though hard, were not unchanging. They sporadically grew to accommodate the soft body of the animal. The thin walls between the internal chambers of the shell are known as septa. As goniatites increased in size, they would move their bodies forward in the shell. At the same time, they secreted new septa behind them, thereby adding another chamber to their shells. Where each septum contacted the wall of the outer shell, sutures are visible as a series of narrow lines on the surface of the shell fossils. The sutures of goniatites have a characteristically zigzag shape.

Hemp Fibers

Today, hemp products are surrounded in controversy, but as far back as ten thousand years ago they were considered a staple of civilization. Early American colonists were legally bound to grow hemp, and the United States government subsidized the production of hemp during the Second World War. Hemp is a particularly valuable commodity because it is the world's strongest natural fiber.

  • Hemp Fibers - Positive

    Positive

    Hemp Fibers - Positive

    The reason hemp fiber is not as popular presently is because of its association with drug use. The most useful hemp fiber is derived from the plant Cannabis sativa. In modern day America, hemp (meaning the roots, stalks and stems of the Cannabis plant) is legal to posses. The flowers, buds, and leaves of the plant, however, are considered to be associated with the drug, marijuana, and are illegal to possess. Since it is impossible to grow hemp without being in possession of marijuana, the United States does not currently produce any industrial hemp products. Yet, recent research, coupled to a change in the tide of popular opinion, is returning hemp to the forefront of the textile industry. Many other countries, which never ceased their hemp production, export their products to the United States.
  • Hemp Fibers - Negative

    Negative

    Hemp Fibers - Negative

    The many advantages of hemp fibers are hard to ignore. Hemp cloth is stronger, longer lasting, more resistant to mildew, and cheaper to produce than cloth made of cotton. In fact, the original Levi Strauss jeans were even made from a hempen canvas. Hemp fiber paper resists decomposition and some samples have survived more than 1,500 years. Hemp products, such as ropes and nets, are famous for their strength and durability and were some of the very first items ever made from the plant. There are also environmental benefits to using hemp fiber. Hemp grows well without herbicides, fungicides, or pesticides, and produces more pulp per acre than timber on a sustainable basis.

Honeybee Wings

On warm days in early summer, while others are relaxing, honeybees are hard at work. This species (Apis mellifera) is especially adapted for its primary activity of collecting pollen and participates in a ritual that is perhaps the most famous and fascinating of all the forms of animal communication.

  • Honeybee Wings - Positive

    Positive

    Honeybee Wings - Positive

    A honeybee's body is divided into three segments, each one equipped with a pair of highly specialized legs. In conjunction, they make the perfect tools for collecting pollen, which provides essential proteins for honeybee larvae. Moreover, most honeybee species have relatively long, tube-shaped tongues (commonly termed a proboscis) that can probe deep into the recesses of flower blooms to lap up nectar. Many flowers, which benefit from the industry of honeybees, aid them in their task. The pollen grains of flowers most attractive to honeybees are very sticky so the pollen will secure easily to their bodies. Also, many flowers provide a landing lip for the bees to rest upon before they delve into the interior.
  • Honeybee Wings - Negative

    Negative

    Honeybee Wings - Negative

    Most remarkable, however, is the cooperation inherent in the species itself. After detecting a source of nectar, a honeybee will return to the hive and perform an intricate ritual. The waggle dance communicates essential information about the location of the food source. In turn, members of the hive echo the scout bee's directions by imitating the dance steps and wing sounds. The group then works together to obtain the most pollen from their precious find.

Horsefly Cornea

Horsefly is the common name for many of the stout flies in the family Tabanidae. The bite of adult female horseflies is an annoyance to humans, but an even greater menace to livestock. Adult males survive solely on pollen and nectar, but the larvae of the species are fierce predators that sometimes display cannibalistic behavior.

  • Horsefly Cornea - Positive

    Positive

    Horsefly Cornea - Positive

    During its lifecycle, a single horsefly will go through several stages. Eggs are laid in large masses on rocks or vegetation that overhang water, hatching after approximately four days. As larvae, horseflies are fairly mobile and usually pass through six to nine instars, or intermediate phases, before pupation. The process often takes several months and allows overwintering of the species. Horsefly larvae feed on other larvae, crustaceans, snails and earthworms, capturing prey with their sharp mandibles and injecting them with venom. When the larvae are ready to pupate they migrate towards water and the top few inches of soil where they remain for one to three weeks. Emerging from their pupal cases, the primary concern of adult horseflies is feeding, closely followed by the need to mate.
  • Horsefly Cornea - Negative

    Negative

    Horsefly Cornea - Negative

    Adult females are serious pests. They affect milk and meat production because the cattle they attack are heavily occupied in fending them off. A cow may lose more than a quarter of a liter of blood per day from horsefly bites. The flies, which are easily interrupted while feeding, may make numerous bites in order to finish a single meal. Horseflies readily move from one animal to another and are capable of transmitting diseases, such as anthrax and tularemia. Although the diseases they may carry primarily afflict animals, they can also occur in humans through contact with infected animals.

Human Cerebrum Thin Section

The cerebrum is divided into two hemispheres by a deep groove termed the longitudinal cerebral fissure. Each side of the cerebrum is active in different functions. The right side of the cerebrum controls activities such as orientation, awareness, depth perception, and facial recognition. Creativity is also often associated with the right hemisphere. The left hemisphere is associated with logic, numbering skills, reasoning, and language.

  • Human Cerebrum Thin Section - Positive

    Positive

    Human Cerebrum Thin Section - Positive

    The cerebrum is divided into two hemispheres by a deep groove termed the longitudinal cerebral fissure. Each side of the cerebrum is active in different functions. The right side of the cerebrum controls activities such as orientation, awareness, depth perception, and facial recognition. Creativity is also often associated with the right hemisphere. The left hemisphere is associated with logic, numbering skills, reasoning, and language.
  • Human Cerebrum Thin Section - Negative

    Negative

    Human Cerebrum Thin Section - Negative

    The hemispheres consist of an inner core, referred to as white matter, and the cerebral cortex, the gray, wrinkled outer layer. The cerebral cortex is organized into six layers and is the location of most the activity in the cerebrum. The functional units of the cortex are vertical columns of neurons, or nerve cells, that run through the layers. Although specific functions are relegated to some of the layers, most of the neurons in the cerebral cortex are devoted to communicating with other neurons. Thus, the cerebral cortex is essentially a network of neurons necessary to coordinate various activities in brain.

Human Erythrocytes

The compositional difference between blood types lies in the specific kinds of antigens found on the surface of the red blood cells. Antigens are protein molecules that provide the biological mark of an individual's blood and tissue type. When different types of blood are mixed within the body, the reaction can be fatal as red blood cells burst and the kidneys fail. Today, there are 27 known human blood groups. Understanding blood compatibility issues has had a revolutionary effect on the field of medicine.

  • Human Erythrocytes - Positive

    Positive

    Human Erythrocytes - Positive

    Red blood cells were first described in 1658, but it was almost another 250 years before the first four human blood groups, A, B, AB and O, were identified. The compositional difference between blood types lies in the specific kinds of antigens found on the surface of the red blood cells. Antigens are protein molecules that provide the biological mark of an individual's blood and tissue type. When different types of blood are mixed within the body, the reaction can be fatal as red blood cells burst and the kidneys fail. Today, there are 27 known human blood groups. Understanding blood compatibility issues has had a revolutionary effect on the field of medicine.
  • Human Erythrocytes - Negative

    Negative

    Human Erythrocytes - Negative

    As far back as the mid-Seventeenth Century, physicians attempted blood transfusions, albeit only in extreme circumstances. The earliest attempted transfusions employed animals as the donors. Later, in the Nineteenth Century, blood was usually transferred directly from a healthy individual to a patient through a rubber tube with hypodermic needles at each end. Physicians were perplexed by the seemingly random results. Some transplant recipients survived while many others did not. The discovery of blood types in the early Twentieth Century is what finally led doctors to understand how transfusions could consistently save lives.

Insect Wings

Insects use their wings to accomplish feats that pilots can only dream of. Their aerodynamic acrobatics have fascinated scientists for years, and the old conviction that bumblebees should not be able to fly has finally been undeniably dispelled. Recent studies in the area of fluid aerodynamics have shed a significant amount of light on insect wings and flight.

  • Insect Wings - Positive

    Positive

    Insect Wings - Positive

    Insect wings are thought to have evolved from a gill-like thoracic segment present in early insects. Their essential material is a thin membrane covered with hair-like projections and supported by blood-filled veins. The leading edge of the wing is much stronger and stiffer than other regions of the wing, which are more elastic and capable of twisting. The areas between the veins arch up, curve down, angle and bend in a multiplicity of architectures.
  • Insect Wings - Negative

    Negative

    Insect Wings - Negative

    Energy is transferred to the wings from powerful muscles within the insect's thorax, but like sails on boats, wings largely depend on the arrangement of their supporting framework. During flight, the wings become distorted by the shifting forces acting upon them, but in a useful and efficient way. Accompanied by complex wing movements, which are often in a figure-eight pattern, wing distortion provides insects with tremendous mid-air maneuverability. In hopes of developing something of great practical use, engineers have been trying to replicate the intricate wing structure and motions of insects for many years. If their attempts prove successful, the advances in flight technology could be phenomenal.

Kidney Tissue Thick Section

Mouse kidneys are located on the upper wall of the abdominal cavity and are held in place by fibrous capsules. Similar to other mammalian kidneys, mouse kidneys appear bean shaped, brownish red, granular, and have a firm consistency. The outer region of the kidney is termed the cortex and the inner area is known as the medulla. Tiny structures called nephrons, which consist of even smaller and more intricate elements, stretch across both sections. The nephrons are the functional units of the kidneys, responsible for filtering blood, reabsorbing water and nutrients, and secreting wastes.

  • Kidney Tissue Thick Section - Positive

    Positive

    Kidney Tissue Thick Section - Positive

    Mouse kidneys are located on the upper wall of the abdominal cavity and are held in place by fibrous capsules. Similar to other mammalian kidneys, mouse kidneys appear bean shaped, brownish red, granular, and have a firm consistency. The outer region of the kidney is termed the cortex and the inner area is known as the medulla. Tiny structures called nephrons, which consist of even smaller and more intricate elements, stretch across both sections. The nephrons are the functional units of the kidneys, responsible for filtering blood, reabsorbing water and nutrients, and secreting wastes.
  • Kidney Tissue Thick Section - Negative

    Negative

    Kidney Tissue Thick Section - Negative

    The similarity of mouse kidneys to human kidneys makes them extremely useful in scientific studies. For instance, researchers have gained a much better understanding of one of the most common forms of kidney disease by using genetically engineered mice as models for the disease. Affecting millions of people worldwide, IgA nephropathy, or Berger's disease, is a condition in which the kidneys cease to filter properly. The disease traditionally results in the need for dialysis or organ transplant. Thanks to researchers and their experimental mice, however, a far more convenient and safe option may soon be available.

Luna Moth Wing Scales

Due to their striking beauty, luna moths are often reared in captivity. They are an integral part of the lucrative lepidopteran trade, and dried adults, live eggs, larvae, and pupae are often sold for profit. Unfortunately for collectors, however, this species is not as vibrant in death as it is in life. Dried specimens fade to a pale yellow, leaving only a faint shadow of what was once a dazzling, luminous green.

  • Luna Moth Wing Scales - Positive

    Positive

    Luna Moth Wing Scales - Positive

    Although fairly common throughout the eastern United States, their nocturnal flying habits and short life span as adults make luna moths a rare find. Luna moths are strong fliers that prefer deciduous hardwood forests, but fare well in urban settings. Indeed, sometimes a careful observer can catch a glimpse of a male luna moth circling a city lamppost very late at night. Females are less often seen than their male counterparts because they do not fly until after mating and usually emerge later. Adults only live for about a week and do not eat during that time. Adult luna moths have no functional mouthparts and must survive solely on the energy stores gained in their larval stage, as they strive to reproduce successfully.
  • Luna Moth Wing Scales - Negative

    Negative

    Luna Moth Wing Scales - Negative

    Due to their striking beauty, luna moths are often reared in captivity. They are an integral part of the lucrative lepidopteran trade, and dried adults, live eggs, larvae, and pupae are often sold for profit. Unfortunately for collectors, however, this species is not as vibrant in death as it is in life. Dried specimens fade to a pale yellow, leaving only a faint shadow of what was once a dazzling, luminous green.

Meiosis in Grasshopper Testes

Members of the order Orthoptera, grasshoppers are well known for their amazing jumping ability. Despite their small size, grasshoppers can cause a tremendous amount of damage if present in large numbers. They are capable of destroying entire crops of alfalfa, clover, cotton, corn and other grains, resulting in millions of dollars in crop damage every year.

  • Meiosis in Grasshopper Testes - Positive

    Positive

    Meiosis in Grasshopper Testes - Positive

    Grasshoppers are widespread and can be found in most habitats except for the colder regions near the North and South poles. Rather than jumping, most species have two pairs of wings that help them get from place to place in search of food. Although some grasshoppers are general herbivores that will eat a wide variety of plants, others are finicky consumers. They demonstrate strong preferences and sometimes pass many edible and nutritionally sound plants in search of something they simply like better.
  • Meiosis in Grasshopper Testes - Negative

    Negative

    Meiosis in Grasshopper Testes - Negative

    Grasshoppers are strong insects with a well-protected body and sight that enables them to identify predators from afar. Some of their most common predators are beetles, birds, mice, snakes, and spiders. Yet, certain varieties of flies that spawn on or near grasshopper eggs are, perhaps, their most unusual predator. After the fly eggs hatch, the newborn flies eat the grasshopper eggs first, soon followed by the adult grasshopper. Nevertheless, humans represent the greatest threat to grasshoppers due to pesticide use and urbanization. In a small way, grasshoppers often fight back. Many species will spit a brown bitter liquid, commonly referred to as "tobacco juice," when handled by humans.

Mosquito Proboscis

There are over 2500 different species of mosquitoes throughout the world and most do not stray more than a mile away from their breeding site. Female mosquitoes need water to lay their eggs. They can produce 100-300 eggs at a time, forming groups that float upon the water's surface like rafts. Areas nearby creeks, lakes, and other slow moving or standing water are, therefore, the most heavily inhabited and should be avoided if one wants to avoid the dreaded mosquito bite.

  • Mosquito Proboscis - Positive

    Positive

    Mosquito Proboscis - Positive

    There are over 2500 different species of mosquitoes throughout the world and most do not stray more than a mile away from their breeding site. Female mosquitoes need water to lay their eggs. They can produce 100-300 eggs at a time, forming groups that float upon the water's surface like rafts. Areas nearby creeks, lakes, and other slow moving or standing water are, therefore, the most heavily inhabited and should be avoided if one wants to avoid the dreaded mosquito bite.
  • Mosquito Proboscis - Negative

    Negative

    Mosquito Proboscis - Negative

    All mosquitoes, however, are not to blame for the itching and irritation so closely associated with their annoying feeding habits. Only female mosquitoes bite. They need the proteins found in blood in order to lay their eggs. The mouthparts of male mosquitoes are unsuitable for piercing skin so they only feed upon plant juices. The bump from a mosquito bite is caused by the saliva a female mosquito injects into her victim to help the blood flow more easily into her abdomen. Most humans are allergic to the saliva, which then produces itching and swelling.

Mouse Intestine Thick Section

Not all mice attain the fame of such greats as Mickey, Jerry, and Mighty Mouse. However, many are significant in other ways, especially as laboratory animals. Their large intestines are very similar to those of other vertebrates, the primary function of which is to absorb water and electrolytes from digestive residues and to store fecal material.

  • Mouse Intestine Thick Section - Positive

    Positive

    Mouse Intestine Thick Section - Positive

    The word "mouse" has no scientific meaning, but species of many families of small rat-like rodents are referred to as mice. Most mouse species, such as the common house mouse, belong to the family Muridae. Over 1300 species of murid rodents have been identified, making Muridae undoubtedly the largest family of mammals currently in existence. Members reside in nearly every habitat on all continents except Antarctica and may even be found on many oceanic islands. In numerous locations, however, species were introduced by humans, rather than occurring naturally.
  • Mouse Intestine Thick Section - Negative

    Negative

    Mouse Intestine Thick Section - Negative

    Laboratory mice are special breeds of house mice and comprise a majority of the animals used in research, teaching, and testing. Large mammals are not often practical for scientific study. Mice, however, are small, easy to handle, inexpensive to rear, breed quickly, and are genetically similar to humans. Beginning in the Twentieth Century, scientists bred different strains of mice with specific genetic deficiencies in order to produce models for human diseases. Today, mice are used to study everything from drug addiction to cancer and human immunodeficiency virus (HIV).

Paramecium Conjugation

The Paramecium genus contains numerous species of single-celled microscopic organisms that appear much like a lady's slipper surrounded by tiny hair-like appendages termed cilia. The miniature protozoan glides through water by a coordinated movement of its cilia like millions of miniature oars. Paramecia are generally found in slow moving and still bodies of freshwater, especially in areas containing large amounts of pond scum, which is rich in algae.

  • Paramecium Conjugation - Positive

    Positive

    Paramecium Conjugation - Positive

    Over 75,000 individual species of paramecia have been recorded and all share certain common features. Constantly moving in search of food, a paramecium sweeps up its meals, mainly bacteria and other small organisms, with a series of cilia that line its oral groove and gullet. A single paramecium has three nuclei. A large, macronucleus is essential for its survival, while one or two smaller micronuclei are necessary for sexual reproduction. Reproduction is usually asexual by binary fission and can occur several times a day. Occasionally, two organisms will exchange nuclear material through conjugation, a form of sexual reproduction.
  • Paramecium Conjugation - Negative

    Negative

    Paramecium Conjugation - Negative

    Although quick to reproduce, a paramecium cannot always successfully compete with its most extraordinary predator. Didinium is smaller in size, but exhibits a ravenous appetite for paramecia. Also classified as protozoa, most species of Didinium are barrel shaped, surrounded by cilia, and have a sharp horn with which they attack and maneuver the prey. After forcing a paramecium into a position in line with its mouth, Didinium opens wide in order to swallow its meal whole. The tiny creature can ingest a paramecium twice its size and repeat the feat as many as a dozen times a day. A group of didinia can rapidly annihilate a large colony of paramecia.

Potato Starch

The value of a potato has had its ups and downs over the past few thousand years. During some moments in history, potatoes were shunned because they were believed to be poisonous. Yet, in other periods, such as the Alaskan Klondike gold rush, they were quite literally worth their weight in gold.

  • Potato Starch - Positive

    Positive

    Potato Starch - Positive

    Potatoes are native to various parts of South America, and the Incas were the first to cultivate the nutritious vegetable in about 200 BC. They were not introduced to other locales until a much later date and were eyed suspiciously by potential consumers who recognized their similarities to the poisonous nightshades. Indeed, Sir Walter Raleigh who was the first to introduce the potato to Ireland, reportedly made the mistake of eating the berries rather than the tuber. His gardener is credited with discovering their true value while in the process of removing the plants by Raleigh's command. The potato's rise in popularity in England was similarly slow to begin. The Puritans opposed their cultivation, primarily because they could find no mention of the potato in the Bible, and it was not until the middle of the Eighteenth Century that potatoes became common in Western Europe as a vegetable. Today, potatoes are grown in all 50 of the United States, in about 125 different countries, and have even been grown in outer space.
  • Potato Starch - Negative

    Negative

    Potato Starch - Negative

    The tubers of the potato, which are the edible part, are not the root but enlarged underground stems in which starch is stored for the future use by the plant. Potatoes consume only a small amount of their own starch during winter months to maintain life functions until spring. The starch of potatoes can also be processed and extracted for use by humans. Potato starch is found in a wide variety of foods, dyes, adhesives, gums, and pharmaceuticals. Moreover, it is of great interest in the development of biodegradable and renewable plastics. Scientists have high hopes for the ecological benefits such improved plastics could produce.

Ramie Fibers

The long, glossy ramie fibers are naturally white and have an almost silky appearance. Ramie is a cellulosic substance as is cotton, linen and other plant fibers. The inner structure of ramie, however, differs from the other plant fibers that contain polymeric carbohydrate structural components. The physical form of the cellulose in the Ramie fiber is very rigid and crystalline but is extremely porous, which provides it with better absorbency than many other cellulose fibers. One of the strongest natural fibers, ramie exhibits even greater strength when wet.

  • Ramie Fibers - Positive

    Positive

    Ramie Fibers - Positive

    The long, glossy ramie fibers are naturally white and have an almost silky appearance. Ramie is a cellulosic substance as is cotton, linen and other plant fibers. The inner structure of ramie, however, differs from the other plant fibers that contain polymeric carbohydrate structural components. The physical form of the cellulose in the Ramie fiber is very rigid and crystalline but is extremely porous, which provides it with better absorbency than many other cellulose fibers. One of the strongest natural fibers, ramie exhibits even greater strength when wet.
  • Ramie Fibers - Negative

    Negative

    Ramie Fibers - Negative

    Often mistaken for linen because of the unevenness in the fiber, ramie is frequently found in modern textiles. China is still one of the leading producers, but faces competition from Taiwan, Korea, the Philippines and Brazil. When incorporated into fabric alone, ramie is extremely absorbent, dries quickly, resists shrinkage, and is unusually resilient against mildew, mold, and insect attacks. Yet, its poor elasticity and brittleness make it better suited for fabric blends. Added to cotton, for instance, ramie increases strength, color, and luster without overly degrading the flexibility of the fabric. Therefore, vegetable fiber is frequently a component in cotton knit sweaters. Besides apparel, ramie can also be found in fish netting, canvas, straw hats, upholstery, and fire hose.

Saccharomyces Yeast Cells

Members of the Saccharomyces genus of yeast fungi have a direct impact on the daily lives of society. Whenever a dinner roll is nibbled or a glass of wine sipped these microorganisms are largely responsible. One of Saccharomyces' many species is employed primarily for the fermentation of sugars in the winemaking process, while another is useful for the rising of bread.

  • Saccharomyces Yeast Cells - Positive

    Positive

    Saccharomyces Yeast Cells - Positive

    The genus Saccharomyces is similar to other yeast genera. Its species are unicellular and cylindrical, oval, or spherical in shape. They reproduce asexually through a process of budding, a new cell forming a protrusion on an existing cell, enlarging, and then breaking away. They can also reproduce sexually through the use of spores. In fact, the Saccharomyces genus is distinguished by asci, small internal structures that contain four to eight sexually produced fungal spores. All yeasts flourish in the presence of sugars and obtain food by direct absorption of nutrients.
  • Saccharomyces Yeast Cells - Negative

    Negative

    Saccharomyces Yeast Cells - Negative

    Saccharomyces cerevisae is an exceptionally important yeast. It is the organism commonly referred to as baker's yeast and has played a central role in food production for thousands of years. The yeast has also been an important tool in scientific research. Due to its easy cultivation, short generation time, and manipulability, scientists have accumulated a tremendous amount of detailed genetic and biochemical information about the species. In fact, Saccharomyces cerevisae was the first unicellular eukaryotic organism to have the entire genome sequenced. Scientists hope to use this knowledge to make discoveries about biological processes that are relevant for higher organisms, such as man.

Spirogyra Filamentous Algae

During times of environmental strain, such as extended droughts or heat waves, members of Spirogyra switch from asexual to sexual reproduction. Genetic material is exchanged via temporary conjugation tubes established between neighboring strands, or even cells from the same strand, forming an egg-shaped, orange zygospore. The cell wall of the zygospore is thick and adapted to surviving harsh conditions. The zygospore emerges as a new algal strand once the environment is more favorable.

  • Spirogyra Filamentous Algae - Positive

    Positive

    Spirogyra Filamentous Algae - Positive

    Although the green slime floating atop a body of water may appear dirty or polluted, this is not necessarily so. In the full sun of the day, Spirogyra produce a relatively large volume of oxygen, which becomes trapped as tiny bubbles between the tangling strands and causes the algae to rise. At night and on overcast days, the process reverses and the simple plants consume oxygen and produce carbon dioxide as a metabolic waste product of cellular respiration. Filamentous algae such as Spirogyra thrive in nutrient rich environments. However, exceptionally large amounts of Spirogyra can indicate over-fertilization of farmlands since excess phosphates and nitrates may contaminate storm water runoff, which, in turn, seep into surrounding waters. When this occurs, wide fluctuations in carbon dioxide and oxygen concentrations can result in rapid changes in the water's pH, causing stress or even death to aquatic organisms such as fish.
  • Spirogyra Filamentous Algae - Negative

    Negative

    Spirogyra Filamentous Algae - Negative

    During times of environmental strain, such as extended droughts or heat waves, members of Spirogyra switch from asexual to sexual reproduction. Genetic material is exchanged via temporary conjugation tubes established between neighboring strands, or even cells from the same strand, forming an egg-shaped, orange zygospore. The cell wall of the zygospore is thick and adapted to surviving harsh conditions. The zygospore emerges as a new algal strand once the environment is more favorable.

Surirella gemma Diatom Frustule

Diatoms are one of the most abundant plants on the Earth. Usually classified in the family Bacillariophyceae, these unicellular algae live in both fresh and salt water. Their extensive fossil record has made them a favorite tool of ecological researchers.

  • Surirella gemma Diatom Frustule - Positive

    Positive

    Surirella gemma Diatom Frustule - Positive

    Each diatom has a cell wall composed primarily of silica, which forms a pillbox-like shell, known as a frustule, around the organism. The cell wall is unusually beautiful and contains intricate markings and designs. The color of the living tissue of diatoms is yellow-brown instead of the green frequently seen in other creatures that use light as a source for energy. There are an estimated 6 million diatoms per cubic foot of seawater, most of which are free-floating. Some, however, are bottom dwellers or grow on other algae and plants. Although not well understood, diatoms have the power of locomotion. Through a slit along the side of the cell, tiny microfibrils protrude and can be used to help the microscopic creatures move.
  • Surirella gemma Diatom Frustule - Negative

    Negative

    Surirella gemma Diatom Frustule - Negative

    Diatoms are important as food for other organisms living in water, but also serve other purposes for humans. For instance, diatomaceous earth, a substance composed of fossilized diatoms, is used in filters, insulation, abrasives, paints, and varnishes. Diatoms are also employed for scientific purposes. Although they are found in all of the world's aquatic environments, most species are habitat specific, living only in areas with certain physical, chemical, and biological characteristics. Therefore, by collecting and analyzing individual species and communities, ecologists can employ diatoms to help determine the condition of an aquatic habitat. Long-term monitoring of habitats and analysis of the fossil record provide scientists with a unique long-term perspective on marine ecosystems.

Termite Claw

Surprisingly, these members of the insect order Isoptera may be likened to cows. Both species have a hugely modified, multi-compartmented stomach developed for digesting a cellulose-based diet. Termites are generally dreaded by homeowners but play an important part in wildlife ecology. They provide food for more amphibians, reptiles, and birds in the tropics than any other insect.

  • Termite Claw - Positive

    Positive

    Termite Claw - Positive

    Of all the insect orders, termites are the only one in which all species are categorized as highly social. Living in colonies, or social communities, they exhibit brood care and strong family ties. In fact, a startling attribute of the termite family is that it is based on monogamy. Termites are faithful to their mates and are considered by scientists to be the most sophisticated families ever known to have evolved.
  • Termite Claw - Negative

    Negative

    Termite Claw - Negative

    Members of termite families may follow different developmental pathways to become part of various castes. Each caste has its own role within the family. Workers comprise the bulk of the population and are responsible for activities such as feeding all dependent castes, digging tunnels, and building and repairing the nest. Soldiers provide colony defense against predators. Queens, or primary reproductives, are relatively immobile and greatly depend upon the workers. The queen's mate, the king, also loyally attends her. Secondary reproductives will take over if a primary reproductive of the same sex dies. They sometimes have to wait a very long time, however, since termite queens have been known to live for over ten years and some mounds indicate longevity of forty years.

Water Fleas (Daphnia)

Daphnia are small in size, but large in purpose. These microscopic crustaceans, belonging to the order Cladocera, are more populous than ants, found worldwide, and essential for the fishing industry. They are nicknamed water fleas due to their characteristic hopping motion and resemblance to the common flea.

  • Water Fleas (Daphnia) - Positive

    Positive

    Water Fleas (Daphnia) - Positive

    Like other Cladocerans, Daphnia are an important link in the food chain. Most species of Daphnia are found in freshwater habitats, but a few occur in marine environments. The microscopic organisms feed upon the microscopic particles and phytoplankton they encounter in their aquatic surroundings. In turn, Daphnia act as food for juvenile fish. These tiny crustaceans are one of the most popular live food for aquarium fishes, but are also important on a much grander scale. In the Great Lakes of North America, water fleas are the basic food of nearly all commercial fish species.
  • Water Fleas (Daphnia) - Negative

    Negative

    Water Fleas (Daphnia) - Negative

    The reproduction and survival of the species, therefore, is of great interest. Daphnia is parthenogenetic most of the year, producing unfertilized eggs that develop into females. Towards the end of seasonal population peaks, in a mechanism not well understood, parthenogenetic females produce parthenogenetic males and sexual females. The sexual females and males copulate and produce a small number of resilient eggs. These eggs can overwinter, withstand drying and freezing, etc., and will hatch when conditions permit. Consequently, the eggs aid the organism in dispersal between bodies of water and allow the species to endure in ephemeral habitats.

Whipworms (Trichuris)

Parasitic members of the Trichuris genus, commonly referred to as whipworms due to the whip-like body form of the adults, contain numerous species that affect a wide variety of mammals, including humans, cattle, rodents, cats and dogs.

  • Whipworms (Trichuris) - Positive

    Positive

    Whipworms (Trichuris) - Positive

    Over 60 species of Trichuris have been documented, and each has been found to undergo a similar life cycle. The adults thrive in a host's large intestine with their anterior end embedded in the cell lining to rob nutrients. The parasite's exact lifespan is unknown, but they can live for several years. Females are capable of producing more than 10,000 eggs in a single day, which are passed out of the host's body with digestive waste and require a warm, moist environment to continue development into the embryonic stage. Infection is acquired through the accidental ingestion of eggs and embryos. Because these parasites do not actually multiply within the host, every individual worm inside a host represents an independent infection event.
  • Whipworms (Trichuris) - Negative

    Negative

    Whipworms (Trichuris) - Negative

    Trichuris trichiura is the species that infests humans. Symptoms of whipworm infection include anemia, pallor, abdominal discomfort, and dysentery. The intensity of symptoms depends upon how many parasites are carried, with individuals having only a few worms appearing to be wholly unaffected. Children are more prone to infection than adults and tend to suffer more severely. Extended infections of whipworms in the young may even cause mental and physical retardation.

Zygnema Green Algae

A common sight floating atop stagnant water, algae of the genus Zygnema can be identified microscopically by its two star-shaped chloroplasts per cell. Found often alongside Spirogyra, another still water green algal genus, Zygnema filaments combine to form green or yellow-brown mats and can reproduce sexually or asexually, including vegetatively.

  • Zygnema Green Algae - Positive

    Positive

    Zygnema Green Algae - Positive

    When their environment becomes unsuitable, akinetes, which are spore-like bodies, are produced asexually. Their very thick cell walls allow these algae to withstand droughts and harsh winters. Sexual reproduction may also commence in poor environments as two side-by-side filaments grow conjugation tubes toward each other. DNA from each plant moves toward the center of the tube, combines, and forms a zygospore. The zygospore sinks into the sediments of the still waters, awaiting more favorable habitat conditions before emerging as new algal strands. However, when nitrates and phosphates are available in sufficient quantities, most frequently vegetative reproduction, or fragmentation of Zygnema, occurs. As with Spirogyra, thick mats and green clouds of Zygnema can indicate over-fertilization or "enrichment" of water bodies, often by contaminated storm water runoff.
  • Zygnema Green Algae - Negative

    Negative

    Zygnema Green Algae - Negative

    During the day, the hair-like strands of green algae produce relatively large volumes of dissolved oxygen. At night, the metabolic processes reverse and the masses of green algae consume oxygen and produce carbon dioxide gas as a cellular respiratory waste product. The rapid creation of carbon dioxide in the water can change the pH level too quickly for aquatic organisms, such as fish, resulting in stress, and abnormal behaviors that make them much more susceptible to predators. During winter months in temperate regions the algal mats die and decompose, creating a significant biological oxygen demand due to bacteria feeding on the decaying organic plant matter. Severe competition for limited oxygen resources often results in a phenomenon referred to as winterkill, a large die-off of fish populations that remains generally undiscovered until the following spring.

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