Wikipedia Loop

Beginning the Wikipedia Loop with the remnant of a conversation from potluck last evening:

Polydactyl Cat
A polydactyl cat is a cat with a congenital physical anomaly, with more than usual number of toes on one or all of its paws as a result of a cat body type genetic mutation. In animals including humans, polydactyly (or polydactylism, also known as hyperdactyly) is the anatomical abnormality of having more than the usual number of digits on the hands or feet.

Click “polydactyly”

Polydactyly or polydactylism (from Ancient Greek πολύς (polus) “many” + δάκτυλος (daktulos) “finger”), also known as hyperdactyly, is a congenital physical anomaly consisting of supernumerary fingers or toes. When each hand or foot has six digits, it is sometimes called sexdactyly, hexadactyly, or hexadactylism.
The extra digit is usually a small piece of soft tissue; occasionally it may contain bone without joints; rarely it may be a complete, functioning digit. The extra digit is most common on the ulnar (little finger) side of the hand, less common on the radial (thumb) side, and very rarely within the middle three digits. The extra digit is most commonly an abnormal fork in an existing digit, or it may rarely originate at the wrist as a normal digit does.
Polydactyly can occur by itself, or more commonly, as one feature of a syndrome of congenital anomalies. When it occurs by itself, it is associated with autosomal dominant mutations in single genes, i.e. it is not a multifactorial trait.[1] But mutation in a variety of genes can give rise to polydactyly. Typically the mutated gene is involved in developmental patterning, and a syndrome of congenital anomalies results, of which polydactyly is one feature.

Click “autosomal dominant”

Autosomal Dominance
In genetics, dominance describes the effects of the different versions of a particular gene on the phenotype of an organism. Many animals (including humans) and plants have two copies of each gene in their genome, one inherited from each parent. The different variants of a specific gene (such as that coding for earlobes) are known as alleles. If an organism inherits two alleles that are at odds with one another, and the phenotype of the organism is determined completely by one of the alleles, then that allele is said to be dominant. The other allele, which has no tangible effect on the organism’s phenotype, is said to be recessive.
In most cases a dominance relationship is seen when the gene encodes an enzyme, and its recessive counterpart does not. In many cases, a normal function can be maintained with only half the amount of an enzyme. In these cases a single copy of the dominant allele produces enough of the gene’s product to give the same effect as two normal copies.
Dominance was discovered by Mendel, who introduced the use of uppercase letters to denote dominant alleles and lowercase to denote recessive alleles, as is still commonly used in introductory genetics courses (for example, E and e for alleles causing free and attached lobes). Although this usage is convenient it is misleading, because dominance is not a property of an allele considered in isolation, but a relationship between the effects of two alleles. When geneticists loosely refer to a dominant allele or a recessive allele, they mean that the allele is dominant or recessive to the standard allele.

Click “earlobe”

Earlobe
From Wikipedia, the free encyclopedia
On the ear of humans and many other animals, the earlobe(‘lobulus auriculæ’), sometimes simply lobe or lobule) is the soft lower part of the external ear, similar in composition to the labia, or pinna. It is the lowermost portion of the human pinna, projecting below the antitragus. The earlobe is composed of tough areolar and adipose (fatty) connective tissues, lacking the firmness and elasticity of the rest of the pinna. Since the earlobe does not contain cartilage the earlobe has a large blood supply and may help to warm the ears and maintain balance but generally earlobes are not considered to have any major biological function.[1]
Earlobes average about 2 cm long, and elongate slightly with age.[2] Human earlobes may be free or detached (hanging free from the head) or attached (joined to the head). Whether the earlobe is free or attached is a classic example of a simple genetic dominance relationship; freely hanging earlobes are the dominant allele and attached earlobes are recessive. Therefore, a person whose genes contain one allele for free earlobes and one for attached lobes will display the freely hanging lobe trait. It is a common misconception that this implies a precise 3-to-1 ratio between free and attached lobes in the human population. Such a ratio would require that the allele frequency for free lobes were precisely 50%, which there is no reason to assume. One study [3] found that the frequency of attached earlobes among Japanese subjects was 67.1%, and in Chinese subjects it was 64.3%.
Earlobes are normally smooth, but occasionally exhibit creases. Creased earlobes are associated with genetic disorders, including Beckwith-Wiedemann syndrome. Earlobe creases are also associated with an increased risk of heart attack and coronary heart disease; however, since earlobes become more creased with age, and older people are more likely to experience heart disease than younger people, age may account for the findings linking heart attack to earlobe creases.[4]
The earlobe contains many nerve endings, and for some people is an erogenous zone.

Click “erogenous zone”

Erogenous zone (I think I elaborated on this one a little too much…)
An erogenous zone is an area of the human body that has heightened sensitivity and stimulation of which normally results in sexual response. There is individual variation in sensitive areas,[citation needed], but the majority of men and women have common erogenous zones, both areas of the skin, and the penis in men and clitoris in women.
There are two types of erogenous zone response in the skin: nonspecific and specific
Nonspecific
The skin is similar to normal haired skin and has the normal high density of nerves and hair follicles. These areas include the sides and back of the neck, the axillae (armpits) and sides of the thorax. An exaggerated tickle and anticipatory response are responsible for the heightened sensual response.
Specific
These areas produce stronger sensation and include the genitals, including prepuce, penis, clitoris, vulva and perianal skin, scrotum, lips and nipple. The rete ridges of the epithelium are well formed and more of the nerves are close to the external surface of the skin than in normal haired skin.
Female genitalia
The clitoris, a visible button-like structure located above the Labia, and is covered by a small fold of skin known as the clitoral hood. It has the most dense nerve supply of any part of the skin.
Located past the clitoris, just above and on either side of the urethral opening is sensitive erectile tissue known as the Skene’s Gland, or U-Spot.
Within the vaginal canal there is a patch of ribbed rough tissue along the front of the canal. It has a texture similar to the Palate (the roof of a mouth). This is the Gräfenberg spot, or G-spot.
At the deepest point on the anterial (front) wall of the vagina located between the cervix and the bladder. This is the Anterior Fornix Erogenous Zone, or A Spot
Male genitalia
The penis is the most sensitive erogenous zone in the male body. In particular, the natural glans (head) and frenulum (foreskin) are highly sensitive and may elicit strong sensations from the slightest touch or movement. The ridged band, theorized by John R. Taylor, is believed to be a sensitive part of the penis as well.
The skin of the scrotum (testicles) is very sensitive to light touching and stroking, causing a pleasurable sensation; the scrotum may also be quite ticklish.
Males can also be aroused by light stroking and touching of the perineum (the area between the scrotum and the anus). Applying a firm pressure on it just before ejaculation can heighten the intensity of orgasm,[citation needed] although this causes retrograde ejaculation and the pressure is sometimes harmful to the pudendal nerve and other anatomical structures in the area.
The Foreskin, which carries the ridged band and lower frenular delta, has mucocutaneous end-organs extending from the distal margin to the point where hairy skin starts.[1] The thin dermis and minimal subcutaneous tissue results in closely set nerve networks. Vater-Pacini corpuscles are present. The mucocutaneous end-organs are formed after birth, with few in newborn infants and many well-organized endings in adults. Winkelmann suggests that the prepuce is a “specific erogenous zone.”[2]
Anus
Moving from the hairy skin to the glabrous skin around the anus the nerve networks rise higher in the skin and the mucocutaneous end-organ becomes apparent at the vermilion border, occurring frequently in this transition zone. The Vater-Pacini corpuscle is deep in the subcutaneous tissues, and into the anal canal.

Click “thorax”

Thorax
The thorax is a division of an animal’s body that lies between the head and the abdomen.
In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae and the ribs. It extends from the neck to the diaphragm, and does not include the upper limbs. The heart and the lungs reside in the thoracic cavity, as well as many blood vessels. The inner organs are protected by the rib cage and the sternum.
In insects and the extinct trilobites, the thorax is one of the three main divisions (or tagmata) of the creature’s body, each of which is in turn composed of multiple segments. It is the area where the wings and legs attach in insects, or an area of multiple articulating plates in trilobites. In most insects, the thorax itself is composed of three segments; the prothorax, the mesothorax, and the metathorax. In extant insects, the prothorax never has wings, though legs are always present in adults; wings (when present) are restricted to at least the mesothorax, and typically also the metathorax, though the wings may be reduced or modified on either or both segments (as in the fly shown, where the metathoracic wings have been reduced to tiny balancing organs called halteres). In the Apocritan Hymenoptera, the first abdominal segment is fused to the metathorax, where it forms a structure known as the propodeum. Accordingly, in these insects, the functional thorax is composed of four segments, and is therefore typically called the mesosoma to distinguish it from the “thorax” of other insects.
Each thoracic segment in an insect is further subdivided into various parts, the most significant of which are the dorsal portion (the notum), the lateral portion (the pleuron; one on each side), and the ventral portion (the sternum). In some insects, each of these parts is composed of one to several independent exoskeletal plates with membrane between them (called sclerites), though in many cases the sclerites are fused to various degrees.

Click “trilobites”

Trilobite
Trilobites (“three-lobes”) are extinct arthropods that form the class Trilobita. They appeared in the Early Cambrian period and flourished throughout the lower Paleozoic era before beginning a drawn-out decline to extinction when, during the Late Devonian extinction, all trilobite orders, with the sole exception of Proetida, died out. The last of the trilobites disappeared in the mass extinction at the end of the Permian about 250 million years ago (m.y.a.).
Trilobites are very well-known, and possibly the second-most famous fossil group, after the dinosaurs. When trilobites appear in the fossil record of the Lower Cambrian they are already highly diverse and geographically dispersed. Because of their diversity and an easily fossilized exoskeleton, they left an extensive fossil record with some 17,000 known species spanning Paleozoic time. Trilobites have been important in biostratigraphy, paleontology, and plate tectonics research. For example, trilobites have been important in estimating the rate of speciation during the period known as the Cambrian Explosion because they are the most diverse group of metazoans known from the fossil record of the early Cambrian,[1] and are readily distinguishable because of complex and well preserved morphologies. The trilobites are often placed within the arthropod subphylum Schizoramia within the superclass Arachnomorpha (equivalent to the Arachnata),[2] although several alternative taxonomies are found in the literature.
Different trilobites made their living in different ways. Some led a benthic life as predators, scavengers or filter feeders. Some swam (a pelagic lifestyle) and fed on plankton. Most life styles expected of modern marine arthropods are seen, except for parasitism.[3] Some trilobites (particularly the family Olenida) are even thought to have evolved a symbiotic relationship with sulfur-eating bacteria from which they derived food.

Click “plankton”

Plankton
Plankton consist of any drifting organisms (animals, plants, archaea, or bacteria) that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. Plankton are defined by their ecological niche rather than their genetic classification. They provide a crucial source of food to aquatic life.

Click “bacteria”

Bacteria
The Bacteria [bækˈtɪr.i.ə] (help•info) (singular: bacterium) are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. The name derives from the Greek βακτήριον, baktērion, meaning “small staff”.) Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste,[2] water, and deep in the Earth’s crust, as well as in organic matter and the live bodies of plants and animals. There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water; in all, there are approximately five nonillion (5×1030) bacteria on Earth,[3] forming much of the world’s biomass.[4] Bacteria are vital in recycling nutrients, with many important steps in nutrient cycles depending on these organisms, such as the fixation of nitrogen from the atmosphere and putrefaction. However, most bacteria have not been characterized, and only about half of the phyla of bacteria have species that can be cultured in the laboratory.[5] The study of bacteria is known as bacteriology, a branch of microbiology.
There are approximately ten times as many bacterial cells as human cells in the human body, with large numbers of bacteria on the skin and in the digestive tract.[6] Although the vast majority of these bacteria are rendered harmless by the protective effects of the immune system, and a few are beneficial, some are pathogenic bacteria and cause infectious diseases, including cholera, syphilis, anthrax, leprosy and bubonic plague. The most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people a year, mostly in sub-Saharan Africa.[7] In developed countries, antibiotics are used to treat bacterial infections and in various agricultural processes, so antibiotic resistance is becoming common. In industry, bacteria are important in processes such as sewage treatment, the production of cheese and yoghurt through fermentation, as well as biotechnology, and the manufacture of antibiotics and other chemicals.[8]
Once regarded as plants constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a fully differentiated nucleus and rarely harbour membrane-bound organelles. Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotic life consists of two very different groups of organisms that evolved independently from an ancient common ancestor. These evolutionary domains are called Bacteria and Archaea.

Click “bubonic plague”

Bubonic plague
Bubonic plague is the best-known manifestation of the bacterial disease plague, caused by the bacterium Yersinia pestis (formerly known as Pasteurella pestis). Bubonic plague is often used synonymously for plague, but it does in fact refer specifically to an infection that enters through the skin and travels through the lymphatics, as is often seen in flea-borne infections. Bubonic Plague kills about 50% of infected patients in 4-7 days. The Bubonic plague is believed by many to be the Black Death that was in Europe in the 1340s.
Pathology and transmission
The Bubonic plague is an infection of the lymphatic system, usually resulting from the bite of an infected flea. The fleas are often found on rodents, and seek out other prey when their rodent hosts die. Once established, bacteria rapidly spread to the lymph nodes and multiply. Yersinia pestis can resist phagocytosis and even reproduce inside phagocytes and kill them. As the disease progresses, the lymph nodes can hemorrhage and become necrotic. Bubonic plague can progress to lethal septicemic plague in some cases.

Click “flea”

Flea
Flea is the common name for any of the small wingless insects of the order Siphonaptera (some authorities use the name Aphaniptera because it is older, but names above family rank need not follow the ICZN rules of priority, so most taxonomists use the more familiar name). Fleas are external parasites, living by hematophagy off the blood of mammals and birds. Genetic and morphological evidence indicates that they are descendants of the Scorpionfly family Boreidae, which are also flightless; accordingly it is possible that they will eventually be reclassified as a suborder within the Mecoptera. In the past, however, it was most commonly supposed that fleas had evolved from the flies (Diptera), based on similarities of the larvae. In any case, all these groups seem to represent a clade of closely related insect lineages, for which the names Mecopteroidea and Antliophora have been proposed.

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