1.
Gastrointestinal tract
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Gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines. A tract is a collection of related anatomic structures or a series of connected body organs, the mouth, oesophagus, stomach, and intestines are part of the human alimentary canal. All bilaterians have a gastrointestinal tract, also called a gut or an alimentary canal and this is a tube that transfers food to the organs of digestion. In large bilaterians, the gastrointestinal tract generally also has an exit, some small bilaterians have no anus and dispose of solid wastes by other means. The gastrointestinal tract contains thousands of different bacteria in their gut flora, the human gastrointestinal tract consists of the esophagus, stomach, and intestines, and is divided into the upper and lower gastrointestinal tracts. In contrast, the digestive system comprises the gastrointestinal tract plus the accessory organs of digestion. The tract may also be divided into foregut, midgut, and hindgut, the whole human GI tract is about nine metres long at autopsy. The GI tract releases hormones from enzymes to help regulate the digestive process, the structure and function can be described both as gross anatomy and as microscopic anatomy or histology. The tract itself is divided into upper and lower tracts, the upper gastrointestinal tract consists of the buccal cavity, pharynx, esophagus, stomach, and duodenum. The exact demarcation between the upper and lower tracts is the muscle of the duodenum. Upon dissection, the duodenum may appear to be an organ, but it is divided into four segments based upon function, location. The four segments of the duodenum are as follows, bulb, descending, horizontal, the suspensory muscle attaches the superior border of the ascending duodenum to the diaphragm. The suspensory muscle is an important anatomical landmark which shows the division between the duodenum and the jejunum, the first and second parts of the small intestine. This is a muscle which is derived from the embryonic mesoderm. The lower gastrointestinal tract includes most of the intestine and all of the large intestine. In humans, the intestine is further subdivided into the duodenum, jejunum and ileum while the large intestine is subdivided into the cecum, colon, rectum. The small intestine begins at the duodenum, which receives food from the stomach and it is a tubular structure, usually between 6 and 7 m long. The area of the human, adult small intestinal mucosa is about 30 m2 and its main function is to absorb the products of digestion into the bloodstream
2.
Vertebrate
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Vertebrates /ˈvɜːrtᵻbrᵻts/ comprise all species of animals within the subphylum Vertebrata /-ɑː/. Vertebrates represent the majority of the phylum Chordata, with currently about 66,000 species described. Vertebrates include the fish and the jawed vertebrates, which include the cartilaginous fish. A bony fish known as the lobe-finned fishes is included with tetrapods, which are further divided into amphibians, reptiles, mammals. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as 7.7 mm, to the blue whale, vertebrates make up less than five percent of all described animal species, the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, hagfish do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as Craniata when discussing morphology, molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a group of vertebrates in the common taxon of craniata. The word origin of vertebrate derives from the Latin word vertebratus, the Proto-Indo-European language origins are still unclear. Vertebrate is derived from the vertebra, which refers to any of the bones or segments of the spinal column. All vertebrates are built along the basic body plan, a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it. In all vertebrates, the mouth is found at, or right below, the remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut. However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon, jawed vertebrates are typified by paired appendages, but this trait is not required in order for an animal to be a vertebrate. All basal vertebrates breathe with gills, the gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior. Each gill is supported by a cartilagenous or bony gill arch, the bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their relatives have more than 50 pairs of gills. In amphibians and some primitive fishes, the larvae bear external gills. These are reduced in adulthood, their function taken over by the gills proper in fishes, some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods
3.
Amphibian
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Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. They inhabit a variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, the young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a respiratory surface and some small terrestrial salamanders and frogs lack lungs. They are superficially similar to lizards but, along with mammals and birds, reptiles are amniotes, the earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony-limbed fins, features that were helpful in adapting to dry land. They diversified and became dominant during the Carboniferous and Permian periods, over time, amphibians shrank in size and decreased in diversity, leaving only the modern subclass Lissamphibia. The three modern orders of amphibians are Anura, Urodela, and Apoda, the number of known amphibian species is approximately 7,000, of which nearly 90% are frogs. The smallest amphibian in the world is a frog from New Guinea with a length of just 7.7 mm. The largest living amphibian is the 1.8 m Chinese giant salamander, the study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology. The word amphibian is derived from the Ancient Greek term ἀμφίβιος, the term was initially used as a general adjective for animals that could live on land or in water, including seals and otters. Traditionally, the class Amphibia includes all tetrapod vertebrates that are not amniotes, the numbers of species cited above follows Frost and the total number of known amphibian species is over 7,000, of which nearly 90% are frogs. With the phylogenetic classification, the taxon Labyrinthodontia has been discarded as it is a group without unique defining features apart from shared primitive characteristics. Classification varies according to the phylogeny of the author and whether they use a stem-based or a node-based classification. The phylogeny of Paleozoic amphibians is uncertain, and Lissamphibia may possibly fall within groups, like the Temnospondyli or the Lepospondyli. If the common ancestor of amphibians and amniotes is included in Amphibia, all modern amphibians are included in the subclass Lissamphibia, which is usually considered a clade, a group of species that have evolved from a common ancestor. The three modern orders are Anura, Caudata, and Gymnophiona, although the fossils of several older proto-frogs with primitive characteristics are known, the oldest true frog is Prosalirus bitis, from the Early Jurassic Kayenta Formation of Arizona. It is anatomically similar to modern frogs. The oldest known caecilian is another Early Jurassic species, Eocaecilia micropodia, the earliest salamander is Beiyanerpeton jianpingensis from the Late Jurassic of northeastern China
4.
Bird
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Birds, a subgroup of Reptiles, are the last living examples of Dinosaurs. Birds live worldwide and range in size from the 5 cm bee hummingbird to the 2.75 m ostrich. They rank as the class of tetrapods with the most living species, at ten thousand. Birds are the closest living relatives of crocodilians, the fossil record indicates that birds evolved from feathered ancestors within the theropod group of saurischian dinosaurs. True birds first appeared during the Cretaceous period, around 100 million years ago, Birds, especially those in the southern continents, survived this event and then migrated to other parts of the world while diversifying during periods of global cooling. Primitive bird-like dinosaurs that lie outside class Aves proper, in the broader group Avialae, have been found dating back to the mid-Jurassic period, around 170 million years ago. Birds have wings which are more or less developed depending on the species, the digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have evolved for swimming. Many species annually migrate great distances, Birds are social, communicating with visual signals, calls, and bird songs, and participating in such social behaviours as cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of species are socially monogamous, usually for one breeding season at a time, sometimes for years. Other species have breeding systems that are polygynous or, rarely, Birds produce offspring by laying eggs which are fertilised through sexual reproduction. They are usually laid in a nest and incubated by the parents, most birds have an extended period of parental care after hatching. Some birds, such as hens, lay eggs even when not fertilised, songbirds, parrots, and other species are popular as pets. Guano is harvested for use as a fertiliser, Birds prominently figure throughout human culture. About 120–130 species have become extinct due to human activity since the 17th century, human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry, the first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae. Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system currently in use, Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade Theropoda, Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria
5.
Reptile
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Reptiles are tetrapod animals in the class Reptilia, comprising todays turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of amphibians, is called herpetology. Because some reptiles are more related to birds than they are to other reptiles. For this reason, many scientists prefer to consider the birds part of Reptilia as well. Some early examples include the lizard-like Hylonomus and Casineria, in addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the K–Pg extinction wiped out the pterosaurs, plesiosaurs, ornithischians, and sauropods, as well as species of theropods, crocodyliforms. Modern non-avian reptiles inhabit every continent with the exception of Antarctica, several living subgroups are recognized, Testudines, approximately 400 species, Sphenodontia,1 species, Squamata, over 9,600 species, Crocodilia,25 species, and Aves,10,000 species. Reptiles are tetrapod vertebrates, creatures that either have four limbs or, unlike amphibians, reptiles do not have an aquatic larval stage. As amniotes, reptile eggs are surrounded by membranes for protection and transport, many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. In the 18th century, the reptiles were, from the outset of classification, the terms reptile and amphibian were largely interchangeable, reptile being preferred by the French. Josephus Nicolaus Laurenti was the first to use the term Reptilia for an expanded selection of reptiles. Today, the two groups are commonly treated under the same heading as herptiles. He subsequently proposed the names of Sauropsida and Ichthyopsida for the two groups. In 1866, Haeckel demonstrated that vertebrates could be divided based on their strategies, and that reptiles, birds. The terms Sauropsida and Theropsida were used again in 1916 by E. S, Goodrich to distinguish between lizards, birds, and their relatives on the one hand and mammals and their extinct relatives on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, according to Goodrich, both lineages evolved from an earlier stem group, Protosauria in which he included some animals today considered reptile-like amphibians, as well as early reptiles. Watson observed that the first two groups diverged very early in history, so he divided Goodrichs Protosauria between them. He also reinterpreted Sauropsida and Theropsida to exclude birds and mammals, thus his Sauropsida included Procolophonia, Eosuchia, Millerosauria, Chelonia, Squamata, Rhynchocephalia, Crocodilia, thecodonts, non-avian dinosaurs, pterosaurs, ichthyosaurs, and sauropterygians
6.
Monotreme
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Monotremes are basal mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals. The only surviving examples of monotremes are all indigenous to Australia and New Guinea, the existing monotreme species are the platypus and four species of echidnas. There is currently debate regarding monotreme taxonomy. The word monotreme comes from the Greek μονός, monos and τρῆμα, trema, in common with reptiles and marsupials, monotremes lack the connective structure which in placental mammals is the primary communication route between the right and left brain hemispheres. Extant monotremes lack teeth as adults, fossil forms and modern platypus young have a tribosphenic form of molars, which is one of the hallmarks of extant mammals. Some recent work suggests that monotremes acquired this form of molar independently of placental mammals and marsupials, toothloss in modern monotremes might be related to their development of electrolocation. Monotreme jaws are constructed differently from those of other mammals. Nonetheless, findings on the extinct species Teinolophos confirm that suspended ear bones evolved independently among monotremes, the external opening of the ear still lies at the base of the jaw. DNA suggests that while this trait is shared and is synapomorphic with birds, platypuses are still mammals, l-ascorbic acid is synthesized only in the kidneys. The monotremes also have extra bones in the girdle, including an interclavicle and coracoid. Monotremes retain a reptile-like gait, with legs on the sides of, rather than underneath, the monotreme leg bears a spur in the ankle region, the spur is not functional in echidnas, but contains a powerful venom in the male platypus. This venom is derived from b-defensins, proteins that are present in mammals that create holes in viral and bacterial pathogens, some reptile venom is also composed of different types of b-defensins, another trait shared with reptiles. It is thought to be an ancient mammalian characteristic, as many non-monotreme archaic mammal groups also possess venomous spurs, the penis only carries semen, urine is excreted through the cloaca. The monotreme penis is similar to a penis, and is covered by a preputial sac. However, the egg is retained for some time within the mother, which provides the egg with nutrients. Newborn monotremes are larval and fetus-like, much like those of marsupials, Monotremes, like all mammals, lactate, but have no defined nipples, excreting the milk from their mammary glands via openings in their skin. All species are long-lived, with low rates of reproduction and relatively prolonged parental care of infants, the zygotes of monotremes, however, undergo meroblastic division, which causes the ovum to split but not completely. Monotremes metabolic rate is low by mammalian standards
7.
Tenrec
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A tenrec is any species of mammal within the family Tenrecidae, found on Madagascar and in parts of the African mainland. Tenrecs are widely diverse, as a result of convergent evolution they resemble hedgehogs, shrews, opossums, mice and they occupy aquatic, arboreal, terrestrial and fossorial environments. Some of these species, including the greater hedgehog tenrec, can be found in the Madagascar dry deciduous forests, tenrecs are small mammals of variable body form. The common ancestry of these animals, along with aardvarks, hyraxes, elephants, continuing work on the molecular and morphological diversity of afrotherian mammals has provided ever increasing support for their common ancestry. Unusual among placental mammals, the anus and urogenital tracts of tenrecs share a common opening, or cloaca, a more commonly seen in birds, reptiles. They have a low temperature, sufficiently so that they do not require a scrotum to cool their sperm as do most other mammals. All species appear to be at least somewhat omnivorous, with forming the largest part of their diets. One species from Madagascar, Limnogale mergulus, is also semiaquatic, all of the species from Madagascar, semiaquatic or not, appear to have evolved from a single, common ancestor, with the mainland tenrecs comprising the next, most-closely related mammalian species. While the fossil record of tenrecs is scarce, at least some specimens from the early Miocene of Kenya show close affinities to living species from Madagascar, most species are nocturnal and have poor eyesight. Their other senses are well developed, however, and they have especially sensitive whiskers, as with many of their other features, the dental formula of tenrecs varies greatly between species, they can have from 32 to 42 teeth in total. Unusual for mammals, the permanent dentition in tenrecs tends not to completely erupt until well after adult body size has been reached and this is one of several anatomical features shared by elephants, hyraxes, sengis, and golden moles, consistent with their descent from a common ancestor. Tenrecs have a period of 50 to 64 days. While the otter shrews have just two young per litter, the tailless tenrec can have as many as 32, and females possess up to 29 teats, at least some tenrec species are social, living in multigenerational family groups with over a dozen individuals. In the island nation of Mauritius, some of the inhabitants eat tenrec meat, though it is difficult to obtain, the lesser hedgehog tenrec is one of 16 mammalian species that will have its genome sequenced as part of the Mammalian Genome Project. Podcast about hibernation which focusses on tenrecs in the last third
8.
Golden mole
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Golden moles are small, insectivorous burrowing mammals endemic to Southern Africa, where their Afrikaans names are gouemolle or kruipmolle. Their eyes are non-functional and covered with furred skin, the external ears are just tiny openings. The rhinarium is a greatly enlarged, dry leathery pad that protects their nostrils while the animal digs. In this respect too, they resemble the marsupial moles, some authors claim that their primary sense is that of touch, and they are particularly sensitive to vibrations that may indicate approaching danger. Note below however, the observations on the malleus in the middle ear, the species range in size from about 8 to about 20 cm. They have muscular shoulders and the forelimbs are radically adapted for digging, all the toes on the forefeet have been reduced, except for a large, the fifth digit is absent and the first and fourth digits are vestigial. The adaptations of the feet are less dramatic, they retain all five toes and are webbed as an adaptation to efficient backward shovelling of soil loosened by the front claws. At one time the Chrysochloridae were regarded as primitive, supporting arguments included, that they were thought to have originated in Gondwana, that they had a low resting metabolic rate, and that they could switch off thermoregulation when inactive. Furthermore, like the tenrecs, they possess a cloaca, however, such points are no longer regarded as strongly suggestive that golden moles are undeveloped reptilian mammals, some are seen rather as adaptations to regional climatic conditions. Going into a torpor when resting or during cold weather, enables them to conserve energy, similarly, they have developed particularly efficient kidneys and most species do not need to drink water at all, in fact they tend to drown easily if they fall into water. Most species of Chrysochloridae live almost exclusively underground in their respectively preferred environments, beneath either grassveld, forest, swamps, deserts, however, Chrysospalax species tend to forage above ground in leaf litter in forests or in meadows. Eremitalpa species such as Grants golden mole live in the sandy Namib desert, where they cannot form tunnels because the sand collapses. Instead during the day, when they must seek shelter, they swim through the loose sand, using their broad claws to paddle. There they enter a state of torpor, thus conserving energy, at night they emerge to forage on the surface rather than wasting energy shifting sand. Their main prey are termites that live under isolated grass clumps, most other species construct both foraging superficial burrows and deeper permanent burrows for residence. Residential burrows are complex in form, and may penetrate as far as a metre below ground and include deep chambers for use as bolt-holes. They push excavated soil up to the surface as mole-hills, or compact it into the tunnel walls and they feed on small insects and earthworms or small vertebrates such as lizards or burrowing snakes. Some species also have hypertrophied middle ear ossicles, in particular the malleus, in this respect there is some apparent convergent evolution to burrowing reptiles in the family Amphisbaenidae. Females give birth to one to three young in a grass-lined nest within the burrow system
9.
Marsupial mole
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Marsupial moles are specialized marsupial mammals, known from two species distributed in the Australian interior. Notoryctes caurinus Notoryctids are small, fossorial mammals that anatomically converge on other mammals, such as living golden moles. Marsupial moles spend most of their underground, coming to the surface only occasionally, probably mostly after rains. They are blind, their eyes having become reduced to vestigial lenses under the skin, the head is cone-shaped, with a leathery shield over the muzzle, the body is tubular, and the tail is a short, bald stub. They are between 12 and 16 cm long, weigh 40 to 60 grams, and are covered in fairly short. Their pouch has evolved to face backwards so it does not fill with sand, the limbs are very short, with reduced digits. The forefeet have two large, flat claws on the third and fourth digits, which are used to excavate soil in front of the animal, the hindfeet are flattened, and bear three small claws, these feet are used to push soil behind the animal as it digs. Epipubic bones are present but small and as in some other fossorial mammals, the molar teeth of Notoryctes are triangular, or zalambdodont, i. e. resembling an inverted Greek letter lambda in occlusal view. Nonetheless, reflecting the consensus of older studies, Archer et al. report the presence of four molars in each quadrant both in living Notoryctes and the fossil notoryctid Naraboryctes. The largest phylogenetic datasets strongly support the placement of Notoryctes as the taxon to a dasyuromorph-peramelian clade. ARKive - images and movies of the marsupial mole Australian Geographic - The marsupial mole, an enduring enigma
10.
Urine
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Urine is a liquid by-product of metabolism in the bodies of many animals, including humans. It is expelled from the kidneys and flows through the ureters to the urinary bladder, cellular metabolism generates numerous by-products, many nitrogenous, that require clearance from the bloodstream. These by-products are eventually expelled from the body during urination, the method for excreting water-soluble chemicals from the body. These chemicals can be detected and analyzed by urinalysis, of the many such substances that exist, the three main nitrogenous wastes of the mammalian body are urea, uric acid, and creatinine. Animal urine forms part of the nitrogen cycle, in balanced ecosystems it fertilizes soil and plants, which in turn continue to support the animal population. Some animals use it to mark their territories, human urine and human feces are collectively referred to as human waste, as sewage, they require sewage treatment in places where population density is high. Livestock urine and feces similarly require proper management if the population density is high. Such management is part of ecological sanitation, most animals have excretory systems for elimination of soluble toxic wastes. In humans, soluble wastes are excreted primarily by the system and, to a lesser extent in terms of urea. The urinary system consists of the kidneys, ureters, urinary bladder, the system produces urine by a process of filtration, reabsorption, and tubular secretion. The kidneys extract the soluble wastes from the bloodstream, as well as water, sugars. The resulting urine contains high concentrations of urea and other substances, urine flows from the kidney through the ureter, bladder, and finally the urethra before passing from the body. Research looking at the duration of urination in a range of species found that 9 larger species urinated for 21 ±13 seconds irrespective of body size. Smaller species including rodents and bats cannot produce jets and instead urinate with a series of drops, producing too much or too little urine needs medical attention. Polyuria is a condition of excessive production of urine, oliguria when <400 mL are produced, about 91-96% of urine consists of water. Urine also contains an assortment of inorganic salts and organic compounds, including proteins, hormones, the total solids in urine are on average 59 g per person per day. Organic matter makes up between 65% and 85% of urine dry solids, with volatile solids comprising 75–85% of total solids, urea is the largest constituent of the solids, constituting more than 50% of the total. On an elemental level, human urine contains 6.87 g/L carbon,8.12 g/L nitrogen,8.25 g/L oxygen, the exact proportions vary with individuals and with factors such as diet and health
11.
Feces
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Feces or faeces are the solid or semisolid metabolic waste from an animals digestive tract, discharged through the anus or cloaca during a process called defecation. Urine and feces together are called excreta, collected feces has various uses, namely as fertilizer or soil conditioner in agriculture, as a fuel source, or for medicinal purposes. After an animal has digested eaten material, the remains of material are discharged from its body as waste. Although it is lower in energy than the food from which it is derived, feces may retain a large amount of energy and this means that of all food eaten, a significant amount of energy remains for the decomposers of ecosystems. Many organisms feed on feces, from bacteria to fungi to insects such as dung beetles, some may specialize in feces, while others may eat other foods as well. Feces serve not only as a food, but also as a supplement to the usual diet of some animals. Feces and urine, which reflect light, are important to raptors such as kestrels. Seeds also may be found in feces, animals who eat fruit are known as frugivores. An advantage for a plant in having fruit is that animals will eat the fruit and this mode of seed dispersal is highly successful, as seeds dispersed around the base of a plant are unlikely to succeed and often are subject to heavy predation. Provided the seed can withstand the pathway through the system, it is not only likely to be far away from the parent plant. This cycling of matter is known as the biogeochemical cycle, the distinctive odor of feces is due to bacterial action. Gut flora produce compounds such as indole, skatole, and thiols and these are the same compounds that are responsible for the odor of flatulence. Consumption of foods prepared with spices may result in the spices being undigested, the perceived bad odor of feces has been hypothesized to be a deterrent for humans, as consuming or touching it may result in sickness or infection. Human perception of the odor may be contrasted by an animals perception of it, for example. In humans and depending on the individual and the circumstances, defecation may occur daily, extensive hardening of the feces may cause prolonged interruption in the routine and is called constipation. Human fecal matter varies significantly in appearance, depending on diet, normally it is semisolid, with a mucus coating. The brown coloration comes from a combination of bile and bilirubin, in newborn babies, initially fecal matter is yellow-green after the meconium. This coloration comes from the presence of bile alone, throughout the life of an ordinary human, one may experience many types of feces
12.
Invertebrate
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Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the subphylum Vertebrata, familiar examples of invertebrates include insects, crabs, lobsters and their kin, snails, clams, octopuses and their kin, starfish, sea-urchins and their kin, jellyfish, and worms. The majority of species are invertebrates, one estimate puts the figure at 97%. Many invertebrate taxa have a number and variety of species than the entire subphylum of Vertebrata. Some of the invertebrates, such as the Tunicata and Cephalochordata are more closely related to the vertebrates than to other invertebrates. This makes the term invertebrate paraphyletic and hence almost meaningless for taxonomic purposes, the word invertebrate comes from the form of the Latin word vertebra, which means a joint in general, and sometimes specifically a joint from the spinal column of a vertebrate. In turn the jointed aspect of vertebra derived from the concept of turning, coupled with the prefix in-, meaning not or without. The term invertebrates is not always precise among non-biologists since it does not accurately describe a taxon in the way that Arthropoda. Each of these describes an valid taxon, phylum, subphylum or family. Invertebrata is a term of convenience, not a taxon, it has very little circumscriptional significance except within the Chordata, the Vertebrata as a subphylum comprises such a small proportion of the Metazoa that to speak of the kingdom Animalia in terms of Vertebrata and Invertebrata has limited practicality. That would at least circumscribe the Chordata, however, even the notochord would be a less fundamental criterion than aspects of embryological development and symmetry or perhaps bauplan. The following text reflects earlier scientific understanding of the term and of animals which have constituted it. According to this understanding, invertebrates do not possess a skeleton of bone and they include hugely varied body plans. Many have fluid-filled, hydrostatic skeletons, like jellyfish or worms, others have hard exoskeletons, outer shells like those of insects and crustaceans. The most familiar invertebrates include the Protozoa, Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Echinodermata, Mollusca, Arthropoda include insects, crustaceans and arachnids. By far the largest number of described species are insects. The following table lists the number of described extant species for major invertebrate groups as estimated in the IUCN Red List of Threatened Species,2014.3. The IUCN estimates that 66,178 extant vertebrate species have been described, the trait that is common to all invertebrates is the absence of a vertebral column, this creates a distinction between invertebrates and vertebrates
13.
Latin
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Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets, Latin was originally spoken in Latium, in the Italian Peninsula. Through the power of the Roman Republic, it became the dominant language, Vulgar Latin developed into the Romance languages, such as Italian, Portuguese, Spanish, French, and Romanian. Latin, Italian and French have contributed many words to the English language, Latin and Ancient Greek roots are used in theology, biology, and medicine. By the late Roman Republic, Old Latin had been standardised into Classical Latin, Vulgar Latin was the colloquial form spoken during the same time and attested in inscriptions and the works of comic playwrights like Plautus and Terence. Late Latin is the language from the 3rd century. Later, Early Modern Latin and Modern Latin evolved, Latin was used as the language of international communication, scholarship, and science until well into the 18th century, when it began to be supplanted by vernaculars. Ecclesiastical Latin remains the language of the Holy See and the Roman Rite of the Catholic Church. Today, many students, scholars and members of the Catholic clergy speak Latin fluently and it is taught in primary, secondary and postsecondary educational institutions around the world. The language has been passed down through various forms, some inscriptions have been published in an internationally agreed, monumental, multivolume series, the Corpus Inscriptionum Latinarum. Authors and publishers vary, but the format is about the same, volumes detailing inscriptions with a critical apparatus stating the provenance, the reading and interpretation of these inscriptions is the subject matter of the field of epigraphy. The works of several hundred ancient authors who wrote in Latin have survived in whole or in part and they are in part the subject matter of the field of classics. The Cat in the Hat, and a book of fairy tales, additional resources include phrasebooks and resources for rendering everyday phrases and concepts into Latin, such as Meissners Latin Phrasebook. The Latin influence in English has been significant at all stages of its insular development. From the 16th to the 18th centuries, English writers cobbled together huge numbers of new words from Latin and Greek words, dubbed inkhorn terms, as if they had spilled from a pot of ink. Many of these words were used once by the author and then forgotten, many of the most common polysyllabic English words are of Latin origin through the medium of Old French. Romance words make respectively 59%, 20% and 14% of English, German and those figures can rise dramatically when only non-compound and non-derived words are included. Accordingly, Romance words make roughly 35% of the vocabulary of Dutch, Roman engineering had the same effect on scientific terminology as a whole
14.
Sanitary sewer
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A sanitary sewer or foul sewer is an underground carriage system specifically for transporting sewage from houses and commercial buildings through pipes to treatment or disposal. Sanitary sewers are part of a system called sewerage or sewage system. Sewage may be treated to water pollution before discharge to surface waters. Sanitary sewers serving industrial areas also carry industrial wastewater, separate sanitary sewer systems are designed to transport sewage alone. In municipalities served by sewers, separate storm drains may be constructed to convey surface runoff directly to surface waters. Sanitary sewers are distinguished from combined sewers, which combine sewage with stormwater runoff in the same pipe, sanitary sewer systems are considered beneficial because they avoid combined sewer overflows. To overcome these disadvantages, some cities built separate sanitary sewers to collect only municipal wastewater, the decision between a combined sewer system or two separate systems is mainly based on need for sewage treatment and cost of providing treatment during heavy rain events. Many cities with combined sewer systems built prior to sewage treatment have not replaced those sewer systems, in the developed world, sewers are pipes from buildings to one or more levels of larger underground trunk mains, which transport the sewage to sewage treatment facilities. Vertical pipes, usually made of precast concrete, called manholes, depending upon site application and use, these vertical pipes can be cylindrical, eccentric or concentric. The manholes are used for access to the pipes for inspection and maintenance. They also facilitate vertical and horizontal angles in otherwise straight pipelines, pipes conveying sewage from an individual building to a common gravity sewer line are called laterals. Branch sewers typically run under streets receiving laterals from buildings along that street, larger cities may have sewers called interceptors receiving flow from multiple trunk sewers. Design and sizing of sanitary sewers considers the population to be served over the life of the sewer, per capita wastewater production. Commercial and industrial flows are considered, but diversion of surface runoff to storm drains eliminates wet weather flow peaks of inefficient combined sewers. Pumps may be necessary where gravity sewers serve areas at lower elevations than the treatment plant. A lift station is a gravity sewer sump with a pump to lift accumulated sewage to a higher elevation, the pump may discharge to another gravity sewer at that location or may discharge through a pressurized force main to some distant location. Most of the solids are removed by the tanks, so the treatment plant can be much smaller than a typical plant. In addition, because of the vast reduction in solid waste, because the wastestream is pressurized, they can be laid just below the ground surface along the lands contour
15.
Bird anatomy
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Bird anatomy, or the physiological structure of birds bodies, shows many unique adaptations, mostly aiding flight. The development of a beak has led to evolution of a specially adapted digestive system and these anatomical specializations have earned birds their own class in the vertebrate phylum. The bird skeleton is highly adapted for flight and it is extremely lightweight but strong enough to withstand the stresses of taking off, flying, and landing. One key adaptation is the fusing of bones into single ossifications, because of this, birds usually have a smaller number of bones than other terrestrial vertebrates. Birds also lack teeth or even a true jaw, instead having a beak, the beaks of many baby birds have a projection called an egg tooth, which facilitates their exit from the amniotic egg, and that falls off once it has done its job. Birds have many bones that are hollow with criss-crossing struts or trusses for structural strength, the number of hollow bones varies among species, though large gliding and soaring birds tend to have the most. Respiratory air sacs often form air pockets within the bones of the birds skeleton. The bones of diving birds are often less hollow than those of non-diving species, loons and puffins are without pneumatized bones entirely. Flightless birds, such as ostriches and emus, demonstrate osseous pneumaticity, possessing pneumatized femurs and, in the case of the emu, Birds also have more cervical vertebrae than many other animals, most have a highly flexible neck consisting of 13-25 vertebrae. Birds are the vertebrates to have fused clavicles or a keeled sternum or breastbone. The keel of the sternum serves as an attachment site for the used for flight or, similarly, for swimming. Again, flightless birds, such as ostriches, which do not have developed pectoral muscles. Swimming birds have a sternum, while walking birds have a long or high sternum and flying birds have a sternum width. Birds have uncinate processes on the ribs and these are hooked extensions of bone which help to strengthen the rib cage by overlapping with the rib behind them. This feature is found in the tuatara. They also have a greatly elongate tetradiate pelvis, similar to some reptiles, the hind limb has an intra-tarsal joint found also in some reptiles. There is extensive fusion of the vertebrae as well as fusion with the pectoral girdle. They have a skull, as in reptiles, with a pre-lachrymal fossa
16.
Sperm
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Sperm is the male reproductive cell and is derived from the Greek word sperma. In the types of reproduction known as anisogamy and its subtype oogamy. A uniflagellar sperm cell that is motile is referred to as a spermatozoon, Sperm cells cannot divide and have a limited life span, but after fusion with egg cells during fertilization, a new organism begins developing, starting as a totipotent zygote. The human sperm cell is haploid, so that its 23 chromosomes can join the 23 chromosomes of the egg to form a diploid cell. In mammals, sperm develops in the testicles and is released from the penis, the mammalian sperm cell consists of a head, neck, a midpiece and a tail. The head contains the nucleus with densely coiled chromatin fibres, surrounded anteriorly by an acrosome, the neck contains the sperm centriole. The midpiece has a central core with many mitochondria spiralled around it, used for ATP production for the journey through the female cervix, uterus. The tail or flagellum executes the lashing movements that propel the spermatocyte, although semen contains millions of sperm, the egg will admit only one. The other ones will die and be absorbed. The spermatozoa of animals are produced through spermatogenesis inside the gonads via meiotic division. The initial spermatozoon process takes around 70 days to complete, the spermatid stage is where the sperm develops the familiar tail. The next stage where it becomes fully mature takes around 60 days when it is called a spermatozoan, Sperm cells are carried out of the male body in a fluid known as semen. Human sperm cells can survive within the reproductive tract for more than 5 days post coitus. Semen is produced in the vesicles, prostate gland and urethral glands. In 2016 scientists at Nanjing Medical University claimed they had produced cells resembling mouse spermatids artificially from stem cells and they injected these spermatids into mouse eggs and produced pups. Sperm quantity and quality are the parameters in semen quality. Thus, in humans, it is a measure of fertility in a man, the genetic quality of sperm, as well as its volume and motility, all typically decrease with age. Human sperm cells are vulnerable to free radical attack and the generation of oxidative DNA damage
17.
Common ostrich
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The ostrich or common ostrich is either one or two species of large flightless birds native to Africa, the only living member of the genus Struthio, which is in the ratite family. In 2014, the Somali ostrich was recognized as a distinct species, the common ostrich shares the order Struthioniformes with the kiwis, emus, rheas, and cassowaries. However, phylogenetic studies have shown that it is the group to all other members of Palaeognathae. It is distinctive in its appearance, with a neck and legs, and can run at up to about 70 km/h. The common ostrich is the largest living species of bird and lays the largest eggs of any living bird, the common ostrichs diet consists mainly of plant matter, though it also eats invertebrates. It lives in groups of 5 to 50 birds. When threatened, the ostrich will either hide itself by lying flat against the ground, if cornered, it can attack with a kick of its powerful legs. Mating patterns differ by region, but territorial males fight for a harem of two to seven females. The common ostrich is farmed around the world, particularly for its feathers and its skin is used for leather products and its meat is marketed commercially, with its leanness a common marketing point. Common ostriches usually weigh from 63 to 145 kilograms, or as much as two adult humans, ostriches of the East African race averaged 115 kg in males and 100 kg in females, while the nominate subspecies was found to average 111 kg in unsexed adults. Exceptional male ostriches can weigh up to 156.8 kg, at sexual maturity, male common ostriches can be from 2.1 to 2.8 m in height, while female common ostriches range from 1.7 to 2.0 m tall. New chicks are fawn in colour, with brown spots. During the first year of life, chicks grow at about 25 cm per month, at one year of age, common ostriches weigh approximately 45 kilograms. Their lifespan is up to 40–45 years, the feathers of adult males are mostly black, with white primaries and a white tail. However, the tail of one subspecies is buff, females and young males are greyish-brown and white. The head and neck of both male and female ostriches is nearly bare, with a layer of down. The skin of the neck and thighs is pinkish gray. The eyes are shaded from sunlight from above, However, the head and bill are relatively small for the birds huge size, with the bill measuring 12 to 14.3 cm
18.
Cassowary
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The cassowaries are ratites in the genus Casuarius and are native to the tropical forests of New Guinea, nearby islands, and northeastern Australia. The most common of these, the cassowary, is the third-tallest and second-heaviest living bird, smaller only than the ostrich. Cassowaries are very shy, but when provoked they are capable of inflicting injuries, occasionally fatal, to dogs, cassowaries are part of the ratite group, which also includes the emu, rheas, ostriches, and kiwi, and the extinct moas and elephant birds. g. The taxonomic name C. papuanus may also be in need of revision to Casuarius westermanni, the evolutionary history of cassowaries, as of all ratites, is not well known. A fossil species was reported from Australia, but for reasons of biogeography this assignment is not certain and it might belong to the prehistoric Emuarius, the northern and dwarf cassowaries are not well known. All cassowaries are usually shy birds of the deep forest, adept at disappearing long before a human knows they are there, even the more accessible southern cassowary of the far north Queensland rain forests is not well researched. Females are bigger and more brightly coloured, adult southern cassowaries are 1.5 to 1.8 m tall, although some females may reach 2 m, and weigh 58.5 kg. All cassowaries have feathers that consist of a shaft and loose barbules and they do not have retrices or a preen gland. Cassowaries have small wings with 5–6 large remeges and these are reduced to stiff, keratinous quills, like porcupine quills, with no barbs. A claw is on each second finger, the furcula and coracoid are degenerate, and their palatal bones and sphenoid bones touch each other. These, along with their body, are thought to be adaptations to ward off vines, thorns. Cassowaries have three-toed feet with sharp claws, the second toe, the inner one in the medial position, sports a dagger-like claw that can be 125 mm long. This claw is particularly fearsome since cassowaries sometimes kick humans and animals with their powerful legs. Cassowaries can run at up to 50 km/h through the dense forest and they are good swimmers, crossing wide rivers and swimming in the sea. All three species have a keratinous skin-covered casque on their heads which grows with age, the casques shape and size, up to 18 cm, is species-dependent. Casuarius casuarius has the largest and Casuarius bennetti the smallest, with Casuarius unappendiculatus having variations in between, contrary to earlier findings, the hollow inside of the casque is spanned with fine fibres which are believed to have an acoustic function. Several functions for the casque have been proposed, one is that they are a secondary sexual characteristic. Other suggested functions include being used to batter through underbrush, as a weapon in dominance disputes, the latter three are disputed by biologist Andrew Mack, whose personal observation suggests that the casque amplifies deep sounds
19.
Kiwi
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Kiwi or kiwis are flightless birds native to New Zealand, in the genus Apteryx and family Apterygidae. At around the size of a chicken, kiwi are by far the smallest living ratites. DNA sequence comparisons have yielded the surprising conclusion that kiwi are much more related to the extinct Malagasy elephant birds than to the moa with which they shared New Zealand. There are five recognised species, two of which are vulnerable, one of which is endangered, and one of which is critically endangered. All species have negatively affected by historic deforestation but currently the remaining large areas of their forest habitat are well protected in reserves. At present, the greatest threat to their survival is predation by mammalian predators. The kiwi is a symbol of New Zealand, and the association is so strong that the term Kiwi is used internationally as the colloquial demonym for New Zealanders. The Māori language word kiwi is generally accepted to be of imitative origin from the call, with its long decurved bill and brown body, the curlew resembles the kiwi. So when the first Polynesian settlers arrived, they may have applied the word kiwi to the new-found bird, the genus name Apteryx is derived from Ancient Greek without wing, a-, without or not, pterux, wing. The name is usually uncapitalised, with the either the anglicised kiwis or, consistent with the Māori language. There are five species of kiwi, as well as a number of subspecies. Relationships in the genus Apteryx The largest species is the great spotted kiwi or Roroa, Apteryx haastii and it has grey-brown plumage with lighter bands. The female lays just one egg, which both parents then incubate, the population is estimated to be over 20,000, distributed through the more mountainous parts of northwest Nelson, the northern West Coast, and the Southern Alps. The small little spotted kiwi, Apteryx owenii is unable to withstand predation by introduced pigs, stoats and cats, about 1350 remain on Kapiti Island. It has been introduced to other islands and appears to be becoming established with about 50 Little Spots on each island. A docile bird the size of a bantam, it stands 25 cm high and she lays one egg, which is incubated by the male. Females lay as many as three eggs in a season, each one in a different nest, the distribution of these kiwi is limited to a small area on the west coast of the South Island of New Zealand. The southern brown kiwi, Tokoeka, or Common kiwi, Apteryx australis, is a common species of kiwi, known from south and west parts of the South Island
20.
Goose
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Geese are waterfowl belonging to the tribe Anserini of the family Anatidae. This tribe comprises the genera Anser, Branta and Chen, some other birds, mostly related to the shelducks, have goose as part of their names. More distantly related members of the family Anatidae are swans, most of which are larger than true geese, and ducks, the word goose is a direct descendent of Proto-Indo-European root, *ghans-. In Germanic languages, the root gave Old English gōs with the plural gēs and gandres, Frisian goes, gies and guoske, New High German Gans, Gänse, and Ganter, and Old Norse gās. The term goose applies to the female in particular, while applies to the male in particular. Young birds before fledging are called goslings, the collective noun for a group of geese on the ground is a gaggle, when in flight, they are called a skein, a team, or a wedge, when flying close together, they are called a plump. The three living genera of true geese are, Anser, grey geese, including the goose, and domestic geese, Chen, white geese. Either these or, more probably, the goose-like Coscoroba swan is the closest living relative of the true geese, the aptly named Anser atavus from some 12 million years ago had even more plesiomorphies in common with swans. In addition, some birds are known from subfossil remains found on the Hawaiian Islands. Geese are monogamous, living in permanent pairs throughout the year, however, unlike most other permanently monogamous animals, paired geese are more dominant and feed more, two factors that result in more young. Some mainly Southern Hemisphere birds are called geese, most of which belong to the shelduck subfamily Tadorninae, the blue-winged goose, Cyanochen cyanopterus, and the Cape Barren goose, Cereopsis novaehollandiae, have disputed affinities. They belong to separate ancient lineages that may ally either to the Tadorninae, Anserinae, the three species of small waterfowl in the genus Nettapus are named pygmy geese. They seem to represent another ancient lineage, with affinities to the Cape Barren goose or the spur-winged goose. A genus of prehistorically extinct seaducks, Chendytes, is sometimes called diving-geese due to their large size, the unusual magpie goose is in a family of its own, the Anseranatidae. The northern gannet, a seabird, is known as the Solan goose, although it is a bird unrelated to the true geese. Well-known sayings about geese include, To have a gander is to something in detail. Whats sauce for the goose is sauce for the means that what is appropriate treatment for one person is equally appropriate for someone else. Saying that someones goose is cooked means that they have suffered, or are about to suffer, a wild goose chase is a useless, futile waste of time and effort
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Swan
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Swans are birds of the family Anatidae within the genus Cygnus. The swans close relatives include the geese and ducks, Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a subfamily, Cygninae. There are six or seven species of swan in the genus Cygnus, in there is another species known as the coscoroba swan. Swans usually mate for life, though divorce does sometimes occur, particularly following nesting failure, and if a mate dies, the number of eggs in each clutch ranges from three to eight. The English word swan, akin to the German Schwan, Dutch zwaan, an adult male is a cob, from Middle English cobbe, an adult female is a pen. Swans are the largest extant members of the waterfowl family Anatidae, the largest species, including the mute swan, trumpeter swan, and whooper swan, can reach a length of over 1.5 m and weigh over 15 kg. Their wingspans can be over 3.1 m, compared to the closely related geese, they are much larger and have proportionally larger feet and necks. Adults also have a patch of unfeathered skin between the eyes and bill, the sexes are alike in plumage, but males are generally bigger and heavier than females. The Northern Hemisphere species of swan have pure white plumage but the Southern Hemisphere species are mixed black, the Australian black swan is completely black except for the white flight feathers on its wings, the chicks of black swans are light grey. The South American black-necked swan has a body with a black neck. The legs of swans are normally a dark grey colour. Bill colour varies, the four species have black bills with varying amounts of yellow. The mute swan and black-necked swan have lumps at the base of their bills on the upper mandible, Swans are generally found in temperate environments, rarely occurring in the tropics. A group of swans is called a bevy or a wedge in flight, four species occur in the Northern Hemisphere, one species is found in Australia and New Zealand and one species is distributed in southern South America. They are absent from tropical Asia, Central America, northern South America, one species, the mute swan, has been introduced to North America, Australia and New Zealand. Several species are migratory, either wholly or partly so, the mute swan is a partial migrant, being resident over areas of Western Europe but wholly migratory in Eastern Europe and Asia. The whooper swan and tundra swan are wholly migratory, and the swans are almost entirely migratory
22.
Duck
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Duck is the common name for a large number of species in the waterfowl family Anatidae, which also includes swans and geese. The ducks are divided among several subfamilies in the family Anatidae, they do not represent a group but a form taxon, since swans. Ducks are mostly birds, mostly smaller than the swans and geese. Ducks are sometimes confused with several types of unrelated water birds with similar forms, such as loons or divers, grebes, gallinules and this word replaced Old English ened/ænid duck, possibly to avoid confusion with other Old English words, like ende end with similar forms. Other Germanic languages still have similar words for duck, for example, Dutch eend duck, the word ened/ænid was inherited from Proto-Indo-European, compare, Latin anas duck, Lithuanian ántis duck, Ancient Greek nēssa/nētta duck, and Sanskrit ātí water bird, among others. A duckling is a duck in downy plumage or baby duck. A male duck is called a drake and the female is called a duck, the overall body plan of ducks is elongated and broad, and the ducks are also relatively long-necked, albeit not as long-necked as the geese and swans. The body shape of diving ducks varies somewhat from this in being more rounded, the bill is usually broad and contains serrated lamellae, which are particularly well defined in the filter-feeding species. In the case of some fishing species the bill is long, the scaled legs are strong and well developed, and generally set far back on the body, more so in the highly aquatic species. The wings are strong and are generally short and pointed. Three species of duck are almost flightless, however. Many species of duck are temporarily flightless while moulting, they seek out protected habitat with good food supplies during this period, the drakes of northern species often have extravagant plumage, but that is moulted in summer to give a more female-like appearance, the eclipse plumage. The plumage of birds generally resembles that of the female. Over the course of evolution, female ducks have evolved to have a corkscrew shaped vagina to prevent rape, Ducks exploit a variety of food sources such as grasses, aquatic plants, fish, insects, small amphibians, worms, and small molluscs. Dabbling ducks feed on the surface of water or on land, along the edge of the beak there is a comb-like structure called a pecten. This strains the water squirting from the side of the beak, the pecten is also used to preen feathers and to hold slippery food items. Diving ducks and sea ducks forage deep underwater, to be able to submerge more easily, the diving ducks are heavier than dabbling ducks, and therefore have more difficulty taking off to fly. A few specialized species such as the mergansers are adapted to catch, to avoid injury when digging into sediment it has no cere, but the nostrils come out through hard horn
23.
Elasmobranchii
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Elasmobranchii is a subclass of Chondrichthyes or cartilaginous fish. Members of this subclass are characterised by having five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins, the teeth are in several series, the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades, the pelvic fins in males are modified to create claspers for the transfer of sperm. There is no bladder, instead these fish maintain buoyancy with large livers rich in oil. The earliest elasmobranch fossils came from the Devonian and many surviving orders date back to the Cretaceous, many species became extinct during the Permian and there was a burst of adaptive radiation during the Jurassic. Extant species are classified under Selachii, the sharks, and Batoidea. Elasmobranchii is one of the two subclasses of cartilaginous fish in the class Chondrichthyes, the other being Holocephali, members of the elasmobranchii subclass have no swim bladders, five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins, and small placoid scales. The teeth are in series, the upper jaw is not fused to the cranium. Extant elasmobranchs exhibit several archetypal jaw suspensions, amphistyly, orbitostyly, hyostyly, in amphistyly, the palatoquadrate has a postorbital articulation with the chondrocranium from which ligaments primarily suspend it anteriorly. The hyoid articulates with the mandibular arch posteriorly, but it appears to provide support to the upper and lower jaws. In orbitostyly, the orbital process hinges with the orbital wall, in contrast, hyostyly involves an ethmoid articulation between the upper jaw and the cranium, while the hyoid most likely provides vastly more jaw support compared to the anterior ligaments. Finally, in euhyostyly, also known as true hyostyly, the mandibular cartilages lack a connection to the cranium. Instead, the hyomandibular cartilages provide the means of jaw support, while the ceratohyal and basihyal elements articulate with the lower jaw. The eyes have a tapetum lucidum, the inner margin of each pelvic fin in the male fish is grooved to constitute a clasper for the transmission of sperm. These fish are distributed in tropical and temperate waters. Many fish maintain buoyancy with swim bladders, however elasmobranchs lack swim bladders, and maintain buoyancy instead with large livers that are full of oil. This stored oil may also function as a nutrient when food is scarce, deep sea sharks are usually targeted for their oil, because the livers of these species can weigh up to 20% of their total weight. Fossilised shark teeth are known from the early Devonian, around 400 million years ago, during the following Carboniferous period, the sharks underwent a period of diversification, with many new forms evolving
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Sarcopterygii
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The living sarcopterygians are the coelacanths and lungfish, additionally, all tetrapods are sarcopterygians or descendants of them. Early lobe-finned fishes are bony fish with fleshy, lobed, paired fins, the fins of lobe-finned fishes differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. The scales of sarcopterygians are true scaloids, consisting of lamellar bone surrounded by layers of bone, dentine-like cosmine. Pectoral and pelvic fins have articulations resembling those of tetrapod limbs and these fins evolved into the legs of the first tetrapod land vertebrates, amphibians. They also possess two dorsal fins with separate bases, as opposed to the dorsal fin of actinopterygians. The braincase of sarcopterygians primitively has a line, but this is lost in tetrapods. Many early sarcopterygians have a symmetrical tail, all sarcopterygians possess teeth covered with true enamel. Most species of lobe-finned fishes are extinct, the largest known lobe-finned fish was Rhizodus hibberti from the Carboniferous period of Scotland which may have exceeded 7 meters in length. Among the two groups of extant species, the coelacanths and the lungfishes, the largest species is the West Indian Ocean coelacanth, reaching 2 m in length, the largest lungfish is the African lungfish which can reach 2 m in length and weigh up to 50 kg. Taxonomists who subscribe to the approach include the grouping Tetrapoda within this group. The fin-limbs of lobe-finned fishes such as the show a strong similarity to the expected ancestral form of tetrapod limbs. The lobe-finned fishes apparently followed two different lines of development and are separated into two subclasses, the Rhipidistia and the Actinistia. The classification below follows Benton 2004, and uses a synthesis of rank-based Linnaean taxonomy, the earliest fossils of sarcopterygians, found in the uppermost Silurian, closely resembled the acanthodians. In the early–middle Devonian, while the predatory placoderms dominated the seas, in the Early Devonian, the sarcopterygians split into two main lineages — the coelacanths and the rhipidistians. The Rhipidistians, whose ancestors lived in the oceans near the river mouths, left the ocean world. They in turn split into two groups, the lungfish and the tetrapodomorphs. The lungfishs greatest diversity was in the Triassic period, today there are fewer than a dozen genera left, the lungfish evolved the first proto-lungs and proto-limbs, developing the ability to live outside a water environment in the middle Devonian. There are three hypotheses as to how they evolved their stubby fins
25.
Lamprey
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Lampreys are any jawless fish of the order Petromyzontiformes, placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like sucking mouth, the common name lamprey is probably derived from Latin lampetra, which may mean stone licker, though the etymology is uncertain. Currently there are about 38 known extant species of lampreys, parasitic species are the best known, and feed by boring into the flesh of other fish to suck their blood, but only 18 species of lampreys are parasitic. Adults of the species do not feed, they live off reserves acquired as ammocoetes. The lampreys are an ancient lineage of vertebrates, though their exact relationship to hagfishes. Adults superficially resemble eels in that they have scaleless, elongated bodies, lacking paired fins, adult lampreys have large eyes, one nostril on the top of the head, and seven gill pores on each side of the head. The pharynx is subdivided, the part forming a respiratory tube that is isolated from the mouth by a valve called the velum. Near the gills are the eyes, which are developed and buried under skin in the larvae. The eyes complete their development during metamorphosis, and in adults are covered by a thin, instead of true vertebrae, they have a series of cartilaginous structures called arcualia arranged above the notochord. Hagfish, which resemble lampreys, have traditionally considered the sister taxon of the true vertebrates. Studies have shown that lampreys are amongst the most energy-efficient swimmers and their swimming movements generate low-pressure zones around their body, which pull rather than push their bodies through the water. Parasitic lampreys feed on prey as adults by attaching their mouthparts to the animals body, then using their teeth to cut through surface tissues until they reach blood. A study of stomach content of some lampreys have also shown remains of intestines, fins, although attacks on humans do occur, they will generally not attack humans unless starved. Non-parasitic lampreys, which are freshwater species, do not feed as adults, they live off reserves acquired as ammocoetes. Lamprey leukocytes express surface variable lymphocyte receptors generated from somatic recombination of leucine-rich repeat gene segments in a recombination activating gene-independent manner, northern lampreys have the highest number of chromosomes among vertebrates. Pouched lamprey larvae also have a high tolerance for free iron in their bodies. Adult lampreys spawn in rivers and then die, the young larvae, ammocoetes, spend several years in the rivers, where they live burrowed in fine sediment, filter feeding on detritus and microorganisms. Then, ammocoetes undergo a metamorphosis lasting several months, some species do not feed after metamorphosis, while others migrate to the sea or lakes, where they feed on different species of fish and even on marine mammals
26.
Actinopterygii
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Actinopterygii /ˌæktᵻnˌɒptəˈrɪdʒi. aɪ/, or the ray-finned fishes, constitute a class or subclass of the bony fishes. These actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, numerically, actinopterygians are the dominant class of vertebrates, comprising nearly 99% of the over 30,000 species of fish. They are ubiquitous throughout freshwater and marine environments from the sea to the highest mountain streams. Extant species can range in size from Paedocypris, at 8 mm, to the ocean sunfish, at 2,300 kg. Ray-finned fishes occur in variant forms. The main features of a typical ray-finned fish are shown in the diagram at the left. In nearly all ray-finned fish, the sexes are separate, development then proceeds with a free-swimming larval stage. However other patterns of ontogeny exist, with one of the commonest being sequential hermaphroditism, in most cases this involves protogyny, fish starting life as females and converting to males at some stage, triggered by some internal or external factor. This may be advantageous as females become less prolific as they age while male fecundity increases with age, protandry, where a fish converts from male to female, is much less common than protogyny. Most families use external rather than internal fertilization, of the oviparous teleosts, most do not provide parental care. Viviparity is relatively rare and is found in about 6% of teleost species, male territoriality preadapts a species for evolving male parental care. There are a few examples of fish that self-fertilise, the mangrove rivulus is an amphibious, simultaneous hermaphrodite, producing both eggs and spawn and having internal fertilisation. This mode of reproduction may be related to the habit of spending long periods out of water in the mangrove forests it inhabits. Males are occasionally produced at temperatures below 19 °C and can fertilise eggs that are spawned by the female. This maintains genetic variability in a species that is otherwise highly inbred, the earliest known fossil actinopterygiian is Andreolepis hedei, dating back 420 million years. Remains have been found in Russia, Sweden, and Estonia, actinopterygians are divided into the subclasses Chondrostei and Neopterygii. The Neopterygii, in turn, are divided into the infraclasses Holostei and Teleostei, during the Mesozoic and Cenozoic the teleosts in particular diversified widely, and as a result, 96% of all known fish species are teleosts. The cladogram shows the groups of actinopterygians and their relationship to the terrestrial vertebrates that evolved from a related group of fish
27.
Chimaera
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Chimaeras are cartilaginous fishes in the order Chimaeriformes, known informally as ghost sharks, rat fish, spookfish, or rabbit fish. Today, they are confined to deep water. Chimaeras live in temperate ocean floors down to 2,600 m deep, exceptions include the members of the genus Callorhinchus, the rabbit fish and the spotted ratfish, which locally or periodically can be found at relatively shallow depths. Consequently, these are also among the few species from the Chimaera order kept in public aquaria and they have elongated, soft bodies, with a bulky head and a single gill-opening. They grow up to 150 cm in length, although includes the lengthy tail found in some species. In many species, the snout is modified into a sensory organ. Like other members of the class Chondrichthyes, chimaera skeletons are constructed of cartilage and their skin is smooth and largely covered by placoid scales, and their color can range from black to brownish gray. For defense, most chimaeras have a venomous spine located in front of the dorsal fin, Chimaeras resemble sharks in some ways, they employ claspers for internal fertilization of females and they lay eggs with leathery cases. They also use electroreception to locate their prey, however, unlike sharks, male chimaeras also have retractable sexual appendages on the forehead and in front of the pelvic fins. The females lay eggs in spindle-shaped, leathery egg cases and they also differ from sharks in that their upper jaws are fused with their skulls and they have separate anal and urogenital openings. They lack sharks many sharp and replaceable teeth, having instead just three pairs of large permanent grinding tooth plates and they also have gill covers or opercula like bony fishes. In some classifications, the chimaeras are included in the class Chondrichthyes of cartilaginous fishes, in other systems, Chimaeras also have some characteristics of bony fishes. The order appears to have originated about 420 million years ago during the Silurian, the 39 extant species fall into three families – the Callorhinchids, Rhinochimaerids and Chimaerids with the callorhinchids being the most basal clade. The families appear to have diverged during the late Jurassic to early Cretaceous List of prehistoric cartilaginous fish List of Chimaeras
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Teleost
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The teleosts or Teleostei are by far the largest infraclass in the class Actinopterygii, the ray-finned fishes, and make up 96 percent of all fish. This diverse group arose in the Triassic period and members are arranged in about 40 orders and 448 families, over 26,000 species have been described. Teleosts range from giant oarfish, measuring 25 ft or more, as well as torpedo-shaped fish built for speed, teleosts can be flattened vertically or horizontally, be elongated cylinders or take specialised shapes as in anglerfish and seahorses. Teleosts dominate the seas from pole to pole and inhabit the depths, estuaries, rivers, lakes. This is of advantage, enabling them to grab prey. Other bones further back in the serve to grind and swallow food. Another difference is that the upper and lower lobes of the fin are about equal in size. The spine ends at the peduncle, distinguishing this group from other fish in which the spine extends into the upper lobe of the tail fin. Teleosts have adopted a range of reproductive strategies, most use external fertilisation, the female lays a batch of eggs, the male fertilises them and the larvae develop without any further parental involvement. A fair proportion of teleosts are hermaphrodites, starting life as females and transitioning to males at some stage, a small percentage of teleosts are viviparous and some provide parental care with typically the male fish guarding a nest and fanning the eggs to keep them well-oxygenated. Teleosts are economically important to humans as is shown by their depiction in art over the centuries, the fishing industry harvests them for food and anglers attempt to capture them for sport. Some species are farmed commercially, and this method of production is likely to be important in the future. Others are kept in aquaria or used in research, especially in the fields of genetics, the defining features of the teleosts are mobile premaxilla, elongated neural arches at the end of the caudal fin and unpaired basibranchial toothplates. The premaxilla is unattached to the neurocranium, it plays a role in protruding the mouth and this lowers the pressure inside the mouth, sucking the prey inside. The lower jaw and maxilla are then pulled back to close the mouth, by contrast, mere closure of the jaws would risk pushing food out of the mouth. In more derived teleosts, the premaxilla is enlarged and has teeth, the maxilla functions to push both the premaxilla and the lower jaw forward. To open the mouth, an adductor muscle pulls back the top of the maxilla, in addition, the maxilla rotates slightly, which pushes forward a bony process that interlocks with the premaxilla. The pharyngeal jaws of teleosts, a set of jaws contained within the throat, are composed of five branchial arches
29.
Anus
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The anus is an opening at the opposite end of an animals digestive tract from the mouth. Amphibians, reptiles, and birds use the same orifice for excreting liquid and solid wastes, for copulation, monotreme mammals also have a cloaca, which is thought to be a feature inherited from the earliest amniotes via the therapsids. Marsupials have a single orifice for excreting both solids and liquids and, in females, a vagina for reproduction. The development of the anus was an important stage in the evolution of multicellular animals and it appears to have happened at least twice, following different paths in protostomes and deuterostomes. In animals at least as complex as an earthworm, the forms a dent on one side, the blastopore, which deepens to become the archenteron. In deuterostomes, the original dent becomes the anus while the gut tunnels through to make another opening. The protostomes were so named because it was thought that in their embryos the dent formed the mouth first and the anus was formed later at the opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the dent close up in the middle, leaving openings at the ends become the mouth. Anal canal Imperforate anus, a birth defect, media related to Anus at Wikimedia Commons
30.
Marsupial
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Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia and the Americas, a distinctive characteristic common to these species is that most of the young are carried in a pouch. Well-known marsupials include kangaroos, wallabies, koalas, possums, opossums, wombats, Tasmanian devils, others include the numbat, the bandicoot, the bettong, the bilby, the quoll, and the quokka. Marsupials represent the clade originating from the last common ancestor of extant metatherians, like other mammals in the Metatheria, they give birth to relatively undeveloped young that often reside with the mother in a pouch, for a certain amount of time. Close to 70% of the 334 extant species occur on the Australian continent, the remaining 100 are found in the Americas — primarily in South America, but thirteen in Central America, and one in North America, north of Mexico. Taxonomically, the two divisions of Marsupialia are, American and Australian marsupials. The order Microbiotheria is found in South America, but is believed to be closely related to Australian marsupials. There are many small species in each group. The term opossum is used to refer to American species, while similar Australian species are properly called possums, again, shrew opossums are more closely related to australidelphians than to true opossums. Order Notoryctemorphia. Marsupials have the characteristics of mammals—e. g. Mammary glands, three middle ear bones, and true hair, there are, however, striking differences as well as a number anatomical features that separate them from Eutherians. In addition to the front pouch, which contains multiple nipples for the protection and sustenance of their young, ossified patellae are absent in most modern marsupials and epipubic bones are present. Marsupials also lack a gross communication between the right and left brain hemispheres, the skull has peculiarities in comparison to higher mammals. In general, the skull is small and tight. Holes are located in the front of the orbit, the cheekbone is enlarged and extends further to the rear. The angular extension of the jaw is bent toward the center. Another feature is the palate which, in contrast to the higher mammals foramina. The teeth differ from that of mammals, so that all taxa except wombats have a different number of incisors in the upper and lower jaws
31.
Amniote
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Amniotes are a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals that lay their eggs on land or retain the fertilized egg within the mother. They are distinguished from the anamniotes, which lay their eggs in water. Older sources, particularly prior to the 20th century, may refer to amniotes as higher vertebrates and anamniotes as lower vertebrates, based on the discredited idea of the Great Chain of Being. Amniotes are tetrapods that are characterised by having an egg equipped with an amnion, amniotes include synapsids and sauropsids, as well as their ancestors, back to amphibians. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes, in eutherian mammals, these membranes include the amniotic sac that surrounds the fetus. These embryonic membranes and the lack of a larval stage distinguish amniotes from tetrapod amphibians, the first amniotes, referred to as basal amniotes, resembled small lizards and evolved from the amphibian reptiliomorphs about 312 million years ago, in the Carboniferous geologic period. Their eggs could survive out of the water, allowing amniotes to branch out into drier environments, the eggs could also breathe and cope with wastes, allowing the eggs and the amniotes themselves to evolve into larger forms. From this point the amniotes spread around the globe, eventually to become the dominant land vertebrates, very early in the evolutionary history of amniotes, basal amniotes diverged into two main lines, the synapsids and the sauropsids, both of which persist into the modern era. Amniotes can be characterized in part by embryonic development that includes the formation of several extensive membranes, the amnion, chorion, and allantois. Amniotes develop directly into a form with limbs and a thick stratified epithelium. In amniotes, the transition from a two-layered periderm to cornified epithelium is triggered by thyroid hormone during embryonic development and their kidneys and large intestines are also well-suited to water retention. Most mammals do not lay eggs, but corresponding structures may be found inside the placenta, the ancestors of true amniotes, such as Casineria kiddi, which lived about 340 million years ago, evolved from amphibian reptiliomorphs and resembled small lizards. At the late Devonian mass extinction 360 million years ago, all known tetrapods were essentially aquatic, indeed, many modern day amniotes are dependent on moisture to keep their eggs from desiccating. Although some modern amphibians lay eggs on land, they all lack advanced traits like an amnion, the amniotic egg was formed through a series of evolutionary steps. This allowed the egg to both its size and the rate of gas exchange, permitting a larger, metabolically more active embryo to reach full development before hatching. Further development of the design, like extraembryonic membranes and a shell, were not essential. The only way for the eggs to increase in size would be to develop new internal structures specialized for respiration, as this happened, it would also affect how much the juveniles could grow before they reached adulthood. In fish and amphibians there is one inner membrane, the embryonic membrane
32.
Mammal
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Mammals are any vertebrates within the class Mammalia, a clade of endothermic amniotes distinguished from reptiles by the possession of a neocortex, hair, three middle ear bones and mammary glands. All female mammals nurse their young with milk, secreted from the mammary glands, Mammals include the largest animals on the planet, the great whales. The basic body type is a quadruped, but some mammals are adapted for life at sea, in the air, in trees. The largest group of mammals, the placentals, have a placenta, Mammals range in size from the 30–40 mm bumblebee bat to the 30-meter blue whale. With the exception of the five species of monotreme, all modern mammals give birth to live young, most mammals, including the six most species-rich orders, belong to the placental group. The largest orders are the rodents, bats and Soricomorpha, the next three biggest orders, depending on the biological classification scheme used, are the Primates, the Cetartiodactyla, and the Carnivora. Living mammals are divided into the Yinotheria and Theriiformes There are around 5450 species of mammal, in some classifications, extant mammals are divided into two subclasses, the Prototheria, that is, the order Monotremata, and the Theria, or the infraclasses Metatheria and Eutheria. The marsupials constitute the group of the Metatheria, and include all living metatherians as well as many extinct ones. Much of the changes reflect the advances of cladistic analysis and molecular genetics, findings from molecular genetics, for example, have prompted adopting new groups, such as the Afrotheria, and abandoning traditional groups, such as the Insectivora. The mammals represent the only living Synapsida, which together with the Sauropsida form the Amniota clade, the early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that produced the non-mammalian Dimetrodon. At the end of the Carboniferous period, this group diverged from the line that led to todays reptiles. Some mammals are intelligent, with some possessing large brains, self-awareness, Mammals can communicate and vocalize in several different ways, including the production of ultrasound, scent-marking, alarm signals, singing, and echolocation. Mammals can organize themselves into fission-fusion societies, harems, and hierarchies, most mammals are polygynous, but some can be monogamous or polyandrous. They provided, and continue to provide, power for transport and agriculture, as well as commodities such as meat, dairy products, wool. Mammals are hunted or raced for sport, and are used as model organisms in science, Mammals have been depicted in art since Palaeolithic times, and appear in literature, film, mythology, and religion. Defaunation of mammals is primarily driven by anthropogenic factors, such as poaching and habitat destruction, Mammal classification has been through several iterations since Carl Linnaeus initially defined the class. No classification system is accepted, McKenna & Bell and Wilson & Reader provide useful recent compendiums. Though field work gradually made Simpsons classification outdated, it remains the closest thing to a classification of mammals
33.
Spongy urethra
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The spongy urethra is the longest part of the male urethra, and is contained in the corpus spongiosum of the penis. It is about 15 cm long, and extends from the termination of the portion to the external urethral orifice. The spongy urethra runs along the length of the penis on its ventral surface and it is about 15–16 cm in length, and travels through the corpus spongiosum. The ducts from the urethral gland enter here, the openings of the bulbourethral glands are also found here. Some textbooks will subdivide the spongy urethra into two parts, the bulbous and pendulous urethra, the urethral lumen runs effectively parallel to the penis, except at the narrowest point, the external urethral meatus, where it is vertical. This produces a stream of urine and has the effect of cleaning the external urethral meatus. The lack of an equivalent mechanism in the female urethra partly explains why urinary tract infections occur so much more frequently in females
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Shrew
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A shrew or shrew mouse is a small mole-like mammal classified in the order Eulipotyphla. True shrews are not to be confused with West Indies shrews, treeshrews, otter shrews, or elephant shrews. Although its external appearance is generally that of a long-nosed mouse and it is in fact a much closer relative of moles, and related to rodents only in that both belong to the Boreoeutheria Magnorder. Shrews have sharp, spike-like teeth, not the familiar gnawing front incisor teeth of rodents, all shrews are comparatively small, most no larger than a mouse. They have small eyes and generally poor vision, but have excellent senses of hearing and they are very active animals, with voracious appetites. Shrews have unusually high rates, above that expected in comparable small mammals. Shrews in captivity can eat 1/2 to 2 times their own weight in food daily. They do not hibernate, but are capable of entering torpor, in winter, many species undergo morphological changes that drastically reduce their body weight. Shrews can lose between 30% and 50% of their weight, shrinking the size of bones, skull. Apart from the first pair of incisors, which are long and sharp, and the molars at the back of the mouth, the teeth of shrews are small and peg-like. The dental formula of shrews is,3.1. 1-3. 31-2. 0-1.1.3 Shrews are fiercely territorial, driving off rivals, many species dig burrows for caching food and hiding from predators, although this is not universal. Female shrews can have up to 10 litters a year, in the tropics, they breed all year round, in temperate zones, Shrews have gestation periods of 17–32 days. The female often becomes pregnant within a day or so of giving birth, Shrews live 12 to 30 months. Shrews are unusual among mammals in a number of respects, unlike most mammals, some species of shrews are venomous. Shrew venom is not conducted into the wound by fangs, the venom contains various compounds, and the contents of the venom glands of the American short-tailed shrew are sufficient to kill 200 mice by intravenous injection. The saliva of the northern short-tailed shrew contains soricidin, a peptide which has studied for use in treating ovarian cancer. Also, along with the bats and toothed whales, some species of shrews use echolocation, unlike most other mammals, shrews lack zygomatic bones, so have incomplete zygomatic arches. The only terrestrial mammals known to echolocate are two genera of shrews, the tenrecs of Madagascar, rats and the solenodons and these include the Eurasian or common shrew and the American vagrant shrew and northern short-tailed shrew
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