Biology K
What is kala-azar (Leishmaniasis) ?
A disease found in tropical countries and southern Europe caused by a protozoan parasite, Leishmania donova, obtained through the bite of a sand fly. It affects some 1.5 million people each year. Also known as dumdum fever or visceral leishmaniasis.
What is kame ?
A short hill, ridge, or mound of stratified drift deposited by glacial meltwater.
What is karyogamy ?
In syngamy, the process of union of two gametes (fertilization), there are two processes. The first step, called plasmogamy, is the fusion of cytoplasm of two cells. The second step is karyogamy, the fusion of the nuclei of two cells. It is the fusion of two compatible haploid nuclei to form one diploid nucleus.
What is karyotype ?
A method of classifying the paired chromosomes of a cell in relation to number, size, and morphology. A microscopic picture is taken of an individual’s chromosome set. The chromosomes are then stained with special color dyes that produce a distinct stripe or banding pattern. The chromosomes are then rearranged according to size from largest to smallest. Used to see gross chromosomal abnormalities with the characteristics of specific diseases.
What is kelp ?
A group of large brown seaweeds or algae (class Phaeophyceae) that belong to the order Laminariales. They have a heteromorphic alternation of generations, which has two free-living life phases: the first or macroscopic diploid sporophyte generation and a microscopic haploid gametophyte generation. Sporophytes are typically differentiated into a holdfast, stipe, and one or more leaflike blades. They live in cold, nutrient-rich waters throughout the world in shallow open coastal waters. They are photosynthetic, which restricts them to clear shallow water not much deeper than 15–40 meters.
Who was Kendall, Edward Calvin ?
Kendall, Edward Calvin (1886–1972) American Biochemist Edward Calvin Kendall was born on March 8, 1886, in South Norwalk, Connecticut. He was educated at Columbia University and obtained a B.S. in 1908, M.S. in chemistry in 1909, and a Ph.D. in chemistry in 1910.
From 1910 until 1911 he was a research chemist for Parke, Davis and Co., in Detroit, Michigan, and conducted research on the thyroid gland, continuing the work from 1911 until 1914 at St. Luke’s Hospital, New York.
In 1914 he was appointed head of the biochemistry section in the graduate school of the Mayo Foundation, Rochester, that is part of the University of Minnesota. In 1915 he was appointed director of the division of biochemistry and subsequently professor of physiological chemistry. In 1951 he retired from the Mayo Foundation and accepted the position of visiting professor in the department of biochemistry at Princeton University.
In 1914 he isolated thyroxine, the active principle of the thyroid gland, and also discovered the crystallization and chemical nature of glutathione, and conducted work on the oxidation systems in animals.
Kendall isolated and identified a series of compounds from the adrenal gland cortex, and while working at Merk & Co., Inc., he prepared cortisone by partial synthesis. He also investigated the effects of cortisone and of adrenocorticotropic hormone (ACTH) on rheumatoid arthritis with Philip S. HENCH, H. F. Polley, and C. H. Slocumb. Kendall and Hench, along with Tadeus REICHSTEIN, shared the Nobel Prize in physiology or medicine in 1950 for this work. Kendall received many awards and honors. He died on May 4, 1972.
What is keratin ?
A tough, insoluble, fibrous protein with high sulfur content that forms the main structure and protective barrier or cytoskeleton of epidermal cells and is the chief constituent of skin, hair, nails, and enamel of the teeth. It is produced by keratinocytes, the most abundant cells in the epidermis (95 percent). Keratin makes up 30 percent of the cellular protein of all living epidermal cells. The high amount of sulfur content is due to the presence of the amino acid cystine.
What is keystone predator ?
A dominant species as predator that maintains species richness in a community through selective predation of the best competitors in the community, and as a result maintains populations of less competitive species.
The ocher star (Pisaster orchraceous) is a keystone predator because it prevents mussels, its prey, from taking over intertidal areas. Sea otters are a keystone predator in kelp beds, since they eat the urchins that feed on kelp, whose beds maintain a diversity of other organisms
The removal of a keystone predator from an ecosystem causes a reduction of the species diversity among its former prey
Keystone species increase or decrease the diversity of a system because they play a dominant role and affect many other organisms, including the death and disappearance of the dependent species.
What is kidney ?
An organ, paired, in vertebrates that regulates secretion and osmoregulation as part of the urinary system. Filtration takes place at the site of the glomerulus in the Bowman’s capsule, while the loops of Henle are responsible for taking waste material to be excreted. Millions of nephrons within the renal cortex and renal medulla filter the blood and regulate the volume and composition of body fluids during the formation of urine. A ureter from each kidney carries urine produced in the kidney to the bladder for elimination.
What is kilocalorie (kcal) ?
One kilocalorie is equal to 1,000 calories, a unit of heat equal to the amount of heat required to raise the temperature of 1 kilogram of water by 1 degree at one atmosphere pressure; used to measure the energy value in food and labor; usually just called calorie: 1 kilocalorie (kcal) = 1 Calorie (Cal) = 1,000 calories (cal). However, in the International System of Units (ISU), the universal unit of energy is the joule (J). One kilocalorie = 4.184 kilojoules (kJ).
What is kilogram ?
The basic unit of mass (not of weight or of force). A kilogram is equal to the mass of 1.000028 cubic decimeters of water at the temperature of its maximum density.
What is kinematics ?
A division of mechanics that studies objects in motion (like an animal’s gait) and their changes in position and the effects of motion on distance and time of travel. Differs from the study of mechanics, which also includes the effects of mass and force.
What is kinesis ?
When an animal finds itself in an unwanted environment, kinesis is its ability to respond to the intensity of this stimulus by undirected movement in a random way (trial and error).
What is kinetic energy ?
Energy of motion; kinetic energy depends on the object’s mass and velocity and can be described mathematically as K.E. = 1/2mv2. Moving matter, be it a rolling rock, flowing water, or falling ball, transfers a portion of its kinetic energy to other matter. For example, an inelastic collision is one in which at least a portion of the kinetic energy of the colliding particles is lost. Potential energy, energy stored in a body, can be converted to kinetic energy.
What is kinetochore ?
A specialized region or structure on the centromere of chromosomes, the region that joins two sister chromatids; links each sister chromatid to the mitotic spindle. The mitotic spindle is the specialized region on the chromatid where kinetochores and sister chromatids attach. When a chromosome replicates after mitosis or meiosis, it produces two side-by-side chromatids, with each eventually becoming a separate chromosome.
What is kinetochore fibers ?
The microtubules that connect kinetochores to spindle polar fibers.
What is kinetosome (basal body) ?
The structure at the base of a flagellum or cilium that rises from the centriole and consists of a cylinder composed of nine longitudinally oriented, evenly spaced, triplet microtubules surrounding one central pair, called the axoneme. Usually found in pairs. Also called a blepharoplast. The type of kinetosomes—based on number, structure, and position—are used to type ciliates.
What is kingdom ?
Taxonomic name used to organize, classify, and identify plants and animals. There are five taxonomic kingdoms: Monera, Protista, Plantae, Fungi, and Animalia. Only the domain is higher in ranking. This system of ranking, called the Linnaean system, was developed by the Swedish scientist Carolus Linnaeus (1707–78), who developed a two-name system, binomial nomenclature (genus and species), for identifying and classifying all living things. The system is based on a hierarchical structure in which organisms are sorted by kingdom, phylum, class, order, family, genus, and species. Organisms belonging to the same kingdom do not have to be very similar, but organisms belonging to the same species are very similar and can reproduce and create offspring.
What is kinocilium ?
A long cilium at the apex of a hair cell, along with other microvilla, that is used in the process of hearing. It senses movement of cupula and is important for balance.
What is kinship ?
The act of organizing individuals into social groups, roles, and categories based on parentage, marriage, or other criteria.
What is klinotaxis ?
A movement in a specific direction relative to a given stimulus, either directly toward or away from the source.
Who was Koch, Robert ?
Koch, Robert (1843–1910) was German Bacteriologist Robert Koch was born on December 11, 1843, in Clausthal in the Upper Harz Mountains and is considered one of the fathers of modern medical bacteriology (along with Louis Pasteur). The son of a mining engineer, he taught himself to read by age five. He attended the local high school and developed an interest in biology.
In 1862 Koch attended the University of Göttingen to study medicine under professor of anatomy Jacob Henle. In 1840 Henle had published that living, parasitic organisms caused infectious diseases. In 1866 Koch married Emmy Fraats and they had one daughter. After receiving his M.D. degree, Koch went to Berlin for further study. In 1867, after a period as assistant in the general hospital at Hamburg, he settled into general practice at Langenhagen and, in 1869, at Rackwitz, in the province of Posen. There he passed his district medical officer’s examination, but in 1870 he volunteered to serve in the Franco-Prussian War. From 1872 to 1880 he was district medical officer for Wollstein and while there carried out his groundbreaking research.
Studying from his four-room flat, with a microscope and other equipment he purchased, he began research on anthrax, earlier discovered by other scientists to be caused by a bacillus. Koch wanted to prove whether or not anthrax was actually caused by the bacillus, and he used mice and bacilli taken from the spleens of dead farm animals. He found that the mice did die from the bacillus and proved that the blood of anthrax-infected animals transmitted it. He also showed that the bacilli could produce resistance spores when environmental conditions were unfavorable, and that they could reemerge as viable anthrax-causing organisms when conditions changed. Koch’s work became internationally known when it was published in 1876. He was the first person to establish a definite causal connection between a particular disease and a particular bacillus. He continued working on methods of studying bacteria and in 1878 published his results that included how to control infections caused by bacteria.
Koch also discovered the tubercle bacillus, the cause of tuberculosis, and developed a method of growing it in pure culture, and in 1882, he published his now classical work on the bacillus. In 1883 he was sent to Egypt as leader of the German Cholera Commission to investigate a cholera outbreak and soon discovered the bacteria that causes cholera and brought back pure cultures of it to Germany. He also studied cholera in India.
Koch formulated rules for the control of epidemics of cholera in 1893 and formed the basis of the methods of control. His work on cholera was rewarded with a prize of 100,000 German marks.
In 1885 Koch was appointed professor of hygiene in the University of Berlin and director of the newly established Institute of Hygiene in the university. Five years later he was appointed brigadier general (generalarzt) class I and freeman of the city of Berlin. In 1891 he became an honorary professor of the medical faculty of Berlin and director of the new Institute for Infectious Diseases. In 1893 Koch married Hedwig Freiberg. Koch continued to travel and explore the causes of many other diseases.
Koch was the recipient of many prizes and medals; honorary doctorates from the Universities of Heidelberg
and Bologna; honorary citizenships of Berlin, Wollstein, and his native Clausthal; and honorary memberships of learned societies and academies in Berlin, Vienna, Posen, Perugia, Naples, and New York. He was awarded the German Order of the Crown, the Grand Cross of the German Order of the Red Eagle, and Orders from Russia and Turkey.
In 1905 Koch was awarded the Nobel Prize in physiology or medicine for his pioneering work on tuberculosis and continued his experimental work on bacteriology and serology. He died on May 27, 1910, in Baden-Baden.
Though he made great strides in the study of tuberculosis, today, 2 billion people worldwide suffer with latent infection. There are 8 million new cases a year, and up to 2 million annual deaths.
Who was Kocher, Theodor Emil ?
Kocher, Theodor Emil (1841–1917) was Swiss Surgeon Theodor Kocher was born on August 25, 1841, in Berne, Switzerland, to a Swiss engineer. He received his medical doctorate in Berne in 1865. In 1872 he became ordinary professor of surgery and director of the University Surgical Clinic at Berne, where he remained for the rest of his career.
He discovered a new method for the reduction of dislocations of the shoulder in 1902, which he explained in his Mobilization of the Duodenum.
He published numerous works on the thyroid gland, hemostasis, antiseptic treatments, surgical infectious diseases, gunshot wounds, and more. His book Chirurgische Operationslehre (Theory on surgical operations) reached six editions and was translated into many languages. His book Erkrankungen der Schilddrüse (Diseases of the thyroid gland) discussed the etiology, symptology, and treatment of goiters. His new ideas on the physiology and pathology of the thyroid gland caused great controversy, but after many successful surgeries, his work on goiter treatment became world known and accepted. In 1909 he received the Nobel Prize for this work and donated the prize money to create a research institute. Kocher devised many new surgical techniques, instruments, and appliances that carry his name, such as forceps (Kocher and Ochsner/Kocher forceps, Kocher tweezers), Kocher incision (in gallbladder surgery), the Kocher vein (thyroid), Kocherization (surgery technique), and Kocher’s test (for thyroid-tracheomalacia). The Kocher-Debré-Semélaigne syndrome is named for him and Robert Debré and Georges Semélaigne. There is also Kocher’s reflex (contraction of abdominal muscles following moderate compression of the testicle) and Kocher’s sign (eyelid movement). Kocher died in Berne on July 27, 1917.
What is Koch’s postulates ?
Criteria proposed in the 19th century by Nobel Prize winner (1905) Robert Koch to determine whether a microbe is the cause of a particular infection. He laid down the following postulates, which must be satisfied before it can be accepted that particular bacteria cause particular diseases.
Who was Kossel, Ludwig Karl Martin Leonhard Albrecht ?
Kossel, Ludwig Karl Martin Leonhard Albrecht (1853–1927) German Chemist, Medical doctor Ludwig Karl Martin Leonhard Albrecht Kossel was born in Rostock on September 16, 1853, the eldest son of Albrecht Kossel, a merchant and Prussian consul, and his wife Clara Jeppe. He attended the secondary school in Rostock and went to the newly founded University of Strassburg in 1872 to study medicine. He received his doctor of medicine in 1878.
Kossel specialized in chemistry of tissues and cells (physiological chemistry), and by the 1870s he had begun his investigations into the constitution of the cell nucleus. He isolated nucleoproteins from the heads of fish sperm cells in 1879. By the 1890s he had focused on the study of the proteins. In 1910 he received the Nobel Prize in physiology or medicine for his contributions in cell chemistry and work on proteins.
Among his important publications are Untersuchungen über die Nukleine und ihre Spaltungsproducte (Investigations into the nucleins and their cleavage products), 1881; Die Gewebe des menschlichen Körpers und ihre mikroskopische Untersuchung (The tissues in the human body and their microscopic investigation), 1889–91, in two volumes, with Behrens and Schieerdecker; and Leitfaden für medizinisch-chemische Kurse (Textbook for medicalchemical courses), 1888. He was also the author of Die Probleme der Biochemie (The problems of biochemistry), 1908; and Die Beziehungen der Chemie zur Physiologie (The relationships between chemistry and physiology), 1913.
Kossel had honorary doctorates from the Universities of Cambridge, Dublin, Ghent, Greifswald, St. Andrews, and Edinburgh, and he was a member of various scientific societies, including the Royal Swedish Academy of Sciences and the Royal Society of Sciences of Uppsala. Albrecht Kossel died on July 5, 1927.
What is Krakatoa ?
An island volcano along the Indonesian arc, between the islands of Sumatra and Java. Krakatoa erupted in 1883 in one of the largest eruptions in history and was heard as far away as Madagascar (2,200 miles). The volcanic dust veil that created spectacular atmospheric effects, like vivid red sunsets, acted as a solar radiation filter, lowering global temperatures as much as 1.2°C in the year after the eruption. Temperatures did not return to normal until 1888.
Who was Krebs, Sir Hans Adolf ?
Krebs, Sir Hans Adolf (1900–1981) German Biochemist Sir Hans Adolf Krebs was born in Hildesheim, Germany, on August 25, 1900, to Georg Krebs, M.D., an ear, nose, and throat surgeon of that city, and his wife Alma (née Davidson).
Krebs was educated at the Gymnasium Andreanum at Hildesheim. Between 1918 and 1923 he studied medicine at the Universities of Göttingen, Freiburg-imBreisgau, and Berlin. He received an M.D. degree at the University of Hamburg in 1925. In 1926 he was appointed assistant to Professor Otto Warburg at the Kaiser Wilhelm Institute for Biology at Berlin-Dahlem, where he remained until 1930. He was forced to leave Germany in 1933 because of his Jewish background.
In 1934 he was appointed demonstrator of biochemistry at the University of Cambridge, and the following year was appointed lecturer in pharmacology at the University of Sheffield. In 1938 he became the newly founded lecturer-in-charge of the Department of Biochemistry. In 1939 he became an English citizen. By 1945 he was a professor and director of the Medical Research Council’s research unit established in the department. In 1954 he was appointed Whitley Professor of Biochemistry in the University of Oxford, and the Medical Research Council’s Unit for Research in Cell Metabolism was transferred to Oxford.
At the University of Freiburg in 1932, he discovered a series of chemical reactions (now known as the urea cycle) by which ammonia is converted to urea in mammalian tissue. For his discoveries of chemical reactions in living organisms now known as the citric acid cycle or the Krebs cycle, he was awarded the 1953 Nobel Prize in physiology or medicine. These reactions involve the conversion, in the presence of oxygen, of substances that are formed by the breakdown of sugars, fats, and protein components to carbon dioxide, water, and energy-rich compounds.
Krebs was a member of many scientific societies, winning many awards and citations for his work, and published works including Energy Transformations in Living Matter (1957) with British biochemist Hans Kornberg. He was knighted in 1958. He died on November 22, 1981, in Oxford, England.
What is Krebs cycle ?
A biochemical cycle in the second stage of cellular respiration involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide. Acetyl coenzyme A (CoA) is combined with oxaloacetate to form citric acid. Citric acid is then converted into a number of other chemicals, and carbon dioxide is released. The process takes place within the mitochondrion. Also called the citric acid cycle or tricarboxylic acid (TCA) cycle, it was conceived and published by scientist Hans Adolf Krebs in 1957.
Who was Krogh, Schack August Steenberg ?
Krogh, Schack August Steenberg (1874–1949) Danish Physiologist Schack August Steenberg Krogh was born in Grenaa, Jutland, Denmark, on November 15, 1874, to Viggo Krogh, a shipbuilder, later brewery master, and Marie Drechmann. He earned his upper secondary school diploma at the Cathedral School of Århus in 1893 and entered the University of Copenhagen in 1893. He began his studies in medicine but turned to zoology, an early childhood interest.
In 1897 he began work for Christian Bohr at the laboratory of medical physiology and later became his assistant. In 1916 he became chair of the zoophysiology department at the University of Copenhagen, a position he held until he retired in 1945.
In 1904 he constructed a microtonometer, making it possible to determine the gas content of blood with great precision. He established that the movement of gases between the alveoli and the blood occurs through passive diffusion. With exercise physiologist Johannes Lindhard, Krogh began the field of exercise physiology in Scandinavia between 1910 and 1915. He developed an automatically controlled bicycle ergometer (1910–11) that is still in use today for exercise. He also demonstrated that muscles burn fat during exercise, and included in his inventions was a climate chamber that could be carried to measure continuous temperature and humidity over a 24-hour period. For his work on capillaries, discovering capillary-motor-regulating mechanisms, he received the Nobel Prize in physiology or medicine in 1920. Some of his important writings include The Anatomy and Physiology of Capillaries (1922, rev. ed. 1959), Osmotic Regulation in Aquatic Animals (1939), and Comparative Physiology of Respiratory Mechanisms (1941). He died on September 13, 1949, in Copenhagen.
What is krummholz ?
Trees that grow near the tree line and that are profoundly shaped by wind and ice, often twisted and flaglike or stunted. Krummholz literally means “crooked wood.”
What is K-selection ?
What is Natural selection, or pattern of reproduction, that occurs in populations at or near the carrying capacity (K) of a normally stable environment. Characteristics of these populations are slow reproduction, increased longevity of individuals, delayed maturity of offspring, or reduction in the number of offspring, with increased level of parental care. In effect, the Kselection strategy is to ensure maximum survival of the individual over that of reproductive capacity. A prime example is humans. ?
What is k-T boundary ?
A transitional stage in geology from the end of the Cretaceous (k) to the beginning of the Tertiary (T), approximately 65 million years ago. Also pertains to a site or area showing evidence of rocks and other materials from both periods. There is a superabundance of iridium and osmium isotopes typical of meteorites in this zone, and this has led some to suggest that the mass extinction of species including dinosaurs was caused by a large Earth collision with asteroids or meteorites.
What is kuru (trembling disease) ?
A slowly progressive and fatal disease of the brain; a human transmissible spongiform encephalopathy (TSE) caused by a prion. Found in New Guinea and transmitted when people handled and ate the brains of their dead relatives, a cannibalistic ritual in Papua New Guinea.
Comments
Post a Comment