1.
Mosquito
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Mosquitoes are small, midge-like flies that constitute the family Culicidae. Females of most species are ectoparasites, whose tube-like mouthparts pierce the skin to consume blood. The word mosquito is Spanish for little fly, thousands of species feed on the blood of various kinds of hosts, mainly vertebrates, including mammals, birds, reptiles, amphibians, and even some kinds of fish. Some mosquitoes also attack invertebrates, mainly other arthropods, though the loss of blood is seldom of any importance to the victim, the saliva of the mosquito often causes an irritating rash that is a serious nuisance. Much more serious though, are the roles of species of mosquitoes as vectors of diseases. The oldest known mosquito with a similar to modern species was found in 79-million-year-old Canadian amber from the Cretaceous. An older sister species with more primitive features was found in Burmese amber that is 90 to 100 million years old, two mosquito fossils have been found that show very little morphological change in modern mosquitoes against their counterpart from 46 million years ago. These fossils are also the oldest ever found to have blood preserved within their abdomens, the Old and New World Anopheles species are believed to have subsequently diverged about 95 million years ago. The mosquito Anopheles gambiae is currently undergoing speciation into the M and S molecular forms, consequently, some pesticides that work on the M form no longer work on the S form. Over 3,500 species of the Culicidae have already been described and they are generally divided into two subfamilies which in turn comprise some 43 genera. These figures are subject to change, as more species are discovered. The two main subfamilies are the Anophelinae and Culicinae, with their genera as shown in the subsection below, the distinction is of great practical importance because the two subfamilies tend to differ in their significance as vectors of different classes of diseases. Roughly speaking, arboviral diseases such as fever and dengue fever tend to be transmitted by Culicine species. Some transmit various species of malaria, but it is not clear that they ever transmit any form of human malaria. Some species do however transmit various forms of filariasis, much as many Simuliidae do, Anopheline mosquitoes, again not necessarily in the genus Anopheles, sometimes bear pathogenic arboviruses, but it is not yet clear that they ever transmit them as effective vectors. However, all the most important vectors of malaria are Anopheline. Anophelinae Culicinae Mosquitoes are members of a family of nematocerid flies, superficially, mosquitoes resemble crane flies and chironomid flies. In particular, the females of species of mosquitoes are blood-eating pests and dangerous vectors of diseases
2.
Rosy boa
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The rosy boa is a species of snake of the family Boidae. The rosy boa is one of two members of that family native to the United States, the other being the rubber boa. The rosy boa is native to the American Southwest, and adjacent Baja California and Sonora and these small, attractive snakes normally attain a length of 17–34 in, although some coastal specimens from California reach 36–44 in. A large adult has a width about the diameter of a golf ball. Coloration in rosy boas is highly variable, and usually locale-specific, the common name is derived from the rosy or salmon coloration that is common on the belly of rosy boas originating from coastal southern California and Baja Mexico. Most rosy boas do not have this coloration, but instead have a series of dark to orange spots on a light-colored background. Almost all rosy boas have at least some trace of three stripes, one down the center of the back, and two on the lower sides. The appearance of stripes varies widely, from extremely straight and having high contrast with the interspaces. Stripe colors can be orange, maroon, rust, brown, interspace colors can be shades of light to dark gray, yellow, or tan. The rosy boa is found in the southwestern United States in the states of California and Arizona, in California, the rosy boa ranges throughout the Colorado and Mojave Deserts and also occupies the coastal areas of Los Angeles, Orange, Riverside, and San Diego Counties. In Arizona, the rosy boa occupies the Mojave Desert and the areas of the Sonoran Desert. It is absent from the eastern and northern halves of the state, in Sonora, the rosy boa ranges from the border with the United States south throughout the Sonoran Desert to at least as far south as Ortiz. In Baja California, the rosy boa is almost ubiquitous ranging throughout the peninsula except in areas of extremely dry or rockless desert. Rosy boas spend most of their lives concealed beneath rocks and in crevices to escape the elements, granite outcroppings are the most common geologic association inhabited by the rosy boa. Less often, they are found in association with volcanic or other rock types, only in rare places do rosy boas inhabit rockless environments. In areas with few rocks, rosy boas use rodent burrows for concealment, rosy boas activity season follows local weather patterns, however, they are generally dormant during the winter, and active during the spring, summer, and fall. Like all snakes, they are dependent on external temperatures to promote such normal bodily functions as digestion and gestation, throughout most of their range, the winter is too cold for these functions and the rosy boas go into a dormant state called brumation. The spring is breeding season, resulting in their highest rate of activity, most rosy boas are encountered in spring as they leave the security of their rock piles and crevices to seek mates
3.
Red kangaroo
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The red kangaroo is the largest of all kangaroos, the largest terrestrial mammal native to Australia, and the largest extant marsupial. It is found across mainland Australia, avoiding only the fertile areas in the south, the east coast. This species is a large kangaroo with long, pointed ears. Males have short, red-brown fur, fading to buff below. Females are smaller males and are blue-grey with a brown tinge, pale gray below. It has two forelimbs with small claws, two muscular hind-limbs, which are used for jumping, and a tail which is often used to create a tripod when standing upright. Females are considerably smaller, with a length of 85–105 cm. Females can weigh from 18 to 40 kg, while males weigh around twice as much at 55 to 90 kg. The average red kangaroo stands approximately 1.5 m tall to the top of the head in upright posture, large mature males can stand more than 1.8 m tall, with the largest confirmed one having been around 2.1 m tall and weighed 91 kg. The red kangaroo maintains its internal temperature at a point of homeostasis about 36 °C using a variety of physical, physiological, and behavioral adaptations. These include having a layer of fur, being less active and staying in the shade when temperatures are high, panting, sweating. The red kangaroos range of vision is approximately 300°, due to the position of its eyes, the red kangaroo ranges throughout western and central Australia. Its range encompasses scrubland, grassland, and desert habitats and it typically inhabits open habitats with some trees for shade. Red kangaroos are capable of conserving water and selecting enough fresh vegetation to survive in an arid environment. The kangaroo’s kidneys efficiently concentrate urine, particularly during summer, red kangaroo primarily eat green vegetation, particularly fresh grasses and forbs, and can get enough even when most plants look brown and dry. One study of kangaroos in Central Australia found that green grass makes up 75–95% of the diet and this grass continues to be green into the dry season. Kangaroos also primarily consumed this species, along with Enneapogon avanaceus, during dry times, kangaroos search for green plants by staying on open grassland and near watercourses. However, some perennial chenopods, such as round-leaf chenopod Kochia are avoided even when abundant, at times, red kangaroos congregate in large numbers, in areas with much forage, these groups can number as much as 1,500 individuals
4.
Asilidae
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The Asilidae are the robber fly family, also called assassin flies. They are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, the name robber flies reflects their notoriously aggressive predatory habits, they feed mainly or exclusively on other insects and as a rule they wait in ambush and catch their prey in flight. The Asilidae are a family in the order Diptera, the true flies, the common name for members of the family is the robber flies. The Asilidae are cosmopolitan, with over 7000 described species, latreille was the authority for establishing the family in 1802. Robber flies have stout, spiny legs and they have three eyes in a characteristic depression on the top of their head between their two large compound eyes. They also have a dense moustache of stiff bristles on the face, this is called the mystax. Some Asilidae do, however, specialize in smaller prey, and they do so apparently irrespective of any repugnatorial chemicals the prey may have at its disposal. Many Asilidae when attacked in turn do not hesitate to defend themselves with their proboscides, the antennae are short, have three segments, and sometimes bear a bristle-like structure called an arista. Though they are a characteristic group for such a large family. Some points of contrast between the families include that the labium in the Therevidae is not a piercing, predatory organ, again, the Therevidae commonly have fluffy setae above the mouthparts, unlike the stiff chaetae comprising the mystax of the Asilidae. Furthermore, in the Asilidae the depression on the vertex between the eyes, tends to be obvious than in the Therevidae. Many Asilidae have long, tapering abdomens, sometimes with a sword-like ovipositor, others, for instance Laphria are fat-bodied bumblebee mimics. The life histories are poorly known, larvae generally seem to live in soil, rotting wood, leaf mold and similar materials, some being predatory and others detrivorous. Adults are generally medium to large in size, with a body length of 1 to 1.5 cm. The shape is elongated, due to the conformation of the long tapering abdomen. Frequently they are aposematic, imitating the livery of Hymenoptera, the head is free and mobile and dichoptic in both sexes and has three ocelli arranged in a characteristic depression formed by the elevation of the compound eyes. This feature is clearly visible in the front view and is a peculiarity of Asilidae. The occipital region has one or more rows of bristles aligned behind the posterior margin of the eye, the facial region has a convex profile with a characteristic dense bundle of bristles, called a mystax
5.
American robin
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The American robin is a migratory songbird of the thrush family. It is named after the European robin because of its reddish-orange breast, the American robin is widely distributed throughout North America, wintering from southern Canada to central Mexico and along the Pacific Coast. It is the bird of Connecticut, Michigan, and Wisconsin. According to some sources, the American robin ranks behind only the red-winged blackbird as the most abundant extant land bird in North America and it has seven subspecies, but only T. m. confinis of Baja California Sur is particularly distinctive, with pale gray-brown underparts. The American robin is active mostly during the day and assembles in large flocks at night and its diet consists of invertebrates, fruits, and berries. It is one of the earliest bird species to lay eggs and its nest consists of long coarse grass, twigs, paper, and feathers, and is smeared with mud and often cushioned with grass or other soft materials. It is among the first birds to sing at dawn, the adult robin is preyed upon by hawks, cats, and snakes, but when feeding in flocks, it can be vigilant and watch other birds for reactions to predators. Brown-headed cowbirds lay eggs in nests, but robins usually reject the cowbird eggs. This species was first described in 1766 by Carl Linnaeus in the edition of his Systema Naturae as Turdus migratorius. The binomial name derives from two Latin words, turdus, thrush, and migratorius from migrare to go, the term robin for this species has been recorded since at least 1703. There are about 65 species of medium to large thrushes in the genus Turdus, characterized by rounded heads, longish pointed wings, libonyanus, and the olive thrush, T. olivaceus, both African species. This conflicts with a 2007 DNA study of 60 of 65 Turdus species which places the American robins closest relative as the rufous-collared robin of Central America, though having distinct plumage, the two species are similar in vocalization and behavior. Beyond this, it lies in a group of four species of otherwise Central American distribution. Seven subspecies of American robin are recognized and these subspecies intergrade and are only weakly defined. It winters in southern coastal Alaska, southern Canada, most of the US, Bermuda and it is uniformly darker or blackish on the head, with a dark gray back. The underparts are more red than those of the nominate subspecies. T. m. achrusterus breeds from southern Oklahoma east to Maryland and western Virginia and south to northern Florida and it winters through much of the southern part of the breeding range. It is smaller than the nominate subspecies, the black feathers of the forehead and crown have pale gray tips
6.
Hummingbird
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Hummingbirds are birds from the Americas that constitute the family Trochilidae. They are among the smallest of birds, most species measuring 7. 5–13 cm, indeed, the smallest extant bird species is a hummingbird, the 5-cm bee hummingbird weighing less than 2.5 g. They are known as hummingbirds because of the sound created by their beating wings which flap at high frequencies audible to humans. They hover in mid-air at rapid wing-flapping rates, typically around 50 times per second, hummingbirds have the highest metabolism of any homeothermic animal. To conserve energy when food is scarce, and nightly when not foraging, they go into torpor, a map of the hummingbird family tree—reconstructed from analysis of 284 of the worlds 338 known species—shows rapid diversification from 22 million years ago. Due to this exceptional evolutionary pattern, as many as 140 hummingbird species can coexist in a specific region, the hummingbird evolutionary tree shows ancestral hummingbirds splitting from insectivorous swifts and treeswifts about 42 million years ago, probably in Eurasia. One key evolutionary factor appears to be an altered taste receptor that enabled hummingbirds to seek nectar, by 22 million years ago the ancestral species of current hummingbirds became established in South America, where environmental conditions stimulated further diversification. The Andes Mountains appear to be a rich environment for hummingbird evolution because diversification occurred simultaneously with mountain uplift over the past 10 million years. Hummingbirds remain in dynamic diversification inhabiting ecological regions across South America, North America, within the same geographic region, hummingbird clades co-evolved with nectar-bearing plant clades, affecting mechanisms of pollination. The same is true for the hummingbird, one of the morphologically most extreme species. Hummingbirds exhibit sexual size dimorphism according to Renschs rule, in males are smaller than females in small species. The extent of sexual size difference varies among clades of hummingbirds. For example, the Mellisugini clade exhibits a large size dimorphism, conversely, the Lophomithini clade displays very little size dimorphism, males and females are similar in size. For males and females of the size, females will tend to have larger beaks. Males tend to be smaller than females, allowing conservation of energy to forage competitively, thus, sexual selection will favor smaller male hummingbirds. Female hummingbirds tend to be larger, requiring energy, with longer beaks that allow for more effective reach into crevices of tall flowers for nectar. Thus females are better at foraging, acquiring flower nectar, directional selection will thus favor the larger hummingbirds in terms of acquiring food. Another evolutionary cause of this sexual dimorphism is that the selective forces from competition for nectar between the sexes of each species are what drive the sexual dimorphism
7.
Krill
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Krill are small crustaceans of the order Euphausiacea, and are found in all the worlds oceans. The name krill comes from the Norwegian word krill, meaning small fry of fish, which is also often attributed to species of fish. In the Southern Ocean, one species, the Antarctic krill, Euphausia superba, makes up an estimated biomass of around 379,000,000 tonnes, making it among the species with the largest total biomass. Of this, over half is eaten by whales, seals, penguins, squid and fish each year, most krill species display large daily vertical migrations, thus providing food for predators near the surface at night and in deeper waters during the day. Krill are fished commercially in the Southern Ocean and in the waters around Japan, the total global harvest amounts to 150, 000–200,000 tonnes annually, most of this from the Scotia Sea. Most of the catch is used for aquaculture and aquarium feeds, as bait in sport fishing. In Japan, Philippines and Russia, krill are used for human consumption and are known as okiami in Japan. They are eaten as camarones in Spain, in the Philippines, it is known as alamang and it is used to make a salty paste called bagoong. Krill are also the prey of baleen whales, including the blue whale. Krill belong to the arthropod subphylum, the Crustacea. The most familiar and largest group of crustaceans, the class Malacostraca, the order Euphausiacea comprises two families. The more abundant Euphausiidae contains ten different genera with a total of 85 species, of these, the genus Euphausia is the largest, with 31 species. The lesser known family, the Bentheuphausiidae, has one species, Bentheuphausia amblyops. It is considered the most primitive extant krill species, well-known species of the Euphausiidae of commercial krill fisheries include Antarctic krill, Pacific krill and Northern krill. There have been many theories of the location of the order Euphausiacea, later, William Thomas Calman ranked the Mysidacea in the superorder Peracarida and euphausiids in the superorder Eucarida, although even up to the 1930s the order Schizopoda was advocated. It was later proposed that order Euphausiacea should be grouped with the Penaeidae in the Decapoda based on developmental similarities, as noted by Robert Gurney. The reason for debate is that krill share some morphological features of decapods. Molecular studies have not unambiguously grouped them, possibly due to the paucity of key rare species such as Bentheuphausia amblyops in krill, one study supports the monophyly of Eucarida, another groups Euphausiacea with Mysida, while yet another groups Euphausiacea with Hoplocarida
8.
Sugar
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Sugar is the generic name for sweet, soluble carbohydrates, many of which are used in food. There are various types of derived from different sources. Simple sugars are called monosaccharides and include glucose, fructose, the table sugar or granulated sugar most customarily used as food is sucrose, a disaccharide of glucose and fructose. Sugar is used in prepared foods and it is added to some foods, in the body, sucrose is hydrolysed into the simple sugars fructose and glucose. Other disaccharides include maltose from malted grain, and lactose from milk, longer chains of sugars are called oligosaccharides or polysaccharides. Some other chemical substances, such as glycerol may also have a sweet taste, low-calorie food substitutes for sugar, described as artificial sweeteners, include aspartame and sucralose, a chlorinated derivative of sucrose. Sugars are found in the tissues of most plants and are present in sufficient concentrations for efficient commercial extraction in sugarcane, the world production of sugar in 2011 was about 168 million tonnes. The average person consumes about 24 kilograms of sugar each year, equivalent to over 260 food calories per person, since the latter part of the twentieth century, it has been questioned whether a diet high in sugars, especially refined sugars, is good for human health. Sugar has been linked to obesity, and suspected of, or fully implicated as a cause in the occurrence of diabetes, cardiovascular disease, dementia, macular degeneration, the etymology reflects the spread of the commodity. The English word sugar ultimately originates from the Sanskrit शर्करा, via Arabic سكر as granular or candied sugar, the contemporary Italian word is zucchero, whereas the Spanish and Portuguese words, azúcar and açúcar, respectively, have kept a trace of the Arabic definite article. The Old French word is zuchre and the contemporary French, sucre, the earliest Greek word attested is σάκχαρις. The English word jaggery, a brown sugar made from date palm sap or sugarcane juice, has a similar etymological origin – Portuguese jagara from the Sanskrit शर्करा. Sugar has been produced in the Indian subcontinent since ancient times and it was not plentiful or cheap in early times and honey was more often used for sweetening in most parts of the world. Originally, people chewed raw sugarcane to extract its sweetness, sugarcane was a native of tropical South Asia and Southeast Asia. Different species seem to have originated from different locations with Saccharum barberi originating in India and S. edule, one of the earliest historical references to sugarcane is in Chinese manuscripts dating back to 8th century BC that state that the use of sugarcane originated in India. Sugar was found in Europe by the 1st century AD, but only as an imported medicine and it is a kind of honey found in cane, white as gum, and it crunches between the teeth. It comes in lumps the size of a hazelnut, sugar is used only for medical purposes. Sugar remained relatively unimportant until the Indians discovered methods of turning sugarcane juice into granulated crystals that were easier to store, crystallized sugar was discovered by the time of the Imperial Guptas, around the 5th century AD
9.
Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
10.
Evolution
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Evolution is change in the heritable characteristics of biological populations over successive generations. Evolutionary processes give rise to biodiversity at every level of organisation, including the levels of species, individual organisms. In July 2016, scientists reported identifying a set of 355 genes from the LUCA of all living on Earth. The fossil record includes a progression from early biogenic graphite, to microbial mat fossils, existing patterns of biodiversity have been shaped both by speciation and by extinction. More than 99 percent of all species that lived on Earth are estimated to be extinct. Estimates of Earths current species range from 10 to 14 million, more recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described. In the mid-19th century, Charles Darwin formulated the theory of evolution by natural selection. This teleonomy is the quality whereby the process of natural selection creates and preserves traits that are fitted for the functional roles they perform. The processes by which the changes occur, from one generation to another, are called evolutionary processes or mechanisms, the four most widely recognized evolutionary processes are natural selection, genetic drift, mutation and gene migration. Natural selection and genetic drift sort variation, mutation and gene migration create variation, consequences of selection can include meiotic drive, nonrandom mating and genetic hitchhiking. In the early 20th century the modern evolutionary synthesis integrated classical genetics with Darwins theory of evolution by natural selection through the discipline of population genetics, the importance of natural selection as a cause of evolution was accepted into other branches of biology. Moreover, previously held notions about evolution, such as orthogenesis, evolutionism, evolutionary computation, a sub-field of artificial intelligence, involves the application of Darwinian principles to problems in computer science. The proposal that one type of organism could descend from another type goes back to some of the first pre-Socratic Greek philosophers, such as Anaximander, such proposals survived into Roman times. The poet and philosopher Lucretius followed Empedocles in his masterwork De rerum natura, in contrast to these materialistic views, Aristotelianism considered all natural things as actualisations of fixed natural possibilities, known as forms. This was part of a teleological understanding of nature in which all things have an intended role to play in a divine cosmic order. In the 17th century, the new method of modern science rejected the Aristotelian approach, however, this new approach was slow to take root in the biological sciences, the last bastion of the concept of fixed natural types. The biological classification introduced by Carl Linnaeus in 1735 explicitly recognized the nature of species relationships. Other naturalists of this time speculated on the change of species over time according to natural laws
11.
Mouth
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It is also the cavity lying at the upper end of the alimentary canal, bounded on the outside by the lips and inside by the pharynx and containing in higher vertebrates the tongue and teeth. This cavity is known as the buccal cavity, from the Latin bucca. Some animal phyla, including vertebrates, have a digestive system, with a mouth at one end. Which end forms first in ontogeny is a used to classify animals into protostome and deuterostome. In the first multicellular animals there was probably no mouth or gut, the particles became enclosed in vacuoles into which enzymes were secreted and digestion took place intracellularly. The digestive products were absorbed into the cytoplasm and diffused into other cells, the vast majority of other multicellular organisms have a mouth and a gut, the lining of which is continuous with the epithelial cells on the surface of the body. A few animals which live parasitically originally had guts but have secondarily lost these structures, the original gut of multicellular organisms probably consisted of a simple sac with a single opening, the mouth. Indigestible waste is ejected through the mouth, in animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the formation of the gut. In deuterostomes, the blastopore becomes the anus while the gut tunnels through to make another opening. In the protostomes, it used to be thought that the formed the mouth while the anus formed later as an opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the slit-like blastopore close up in the middle, apart from sponges and placozoans, almost all animals have an internal gut cavity which is lined with gastrodermal cells. In less advanced invertebrates such as the sea anemone, the mouth also acts as an anus, circular muscles around the mouth are able to relax or contract in order to open or close it. A fringe of tentacles thrusts food into the cavity and it can gape widely enough to large prey items. Food passes first into a pharynx and digestion occurs extracellularly in the gastrovascular cavity, annelids have simple tube-like gets and the possession of an anus allows them to separate the digestion of their foodstuffs from the absorption of the nutrients. Many molluscs have a radula which is used to scrape microscopic particles off surfaces, in invertebrates with hard exoskeletons, various mouthparts may be involved in feeding behaviour. Insects have a range of mouthparts suited to their mode of feeding and these include mandibles, maxillae and labium and can be modified into suitable appendages for chewing, cutting, piercing, sponging and sucking. Decapods have six pairs of appendages, one pair of mandibles. Sea urchins have a set of five sharp calcareous plates which are used as jaws and are known as Aristotles lantern, in vertebrates, the first part of the digestive system is the buccal cavity, commonly known as the mouth
12.
Whale
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Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. They are a grouping within the infraorder Cetacea, usually excluding dolphins. Whales, dolphins and porpoises belong to the order Cetartiodactyla with even-toed ungulates and their closest living relatives are the hippopotamuses, the two parvorders of whales, baleen whales and toothed whales, are thought to have split apart around 34 million years ago. The whales comprise eight extant families, Balaenopteridae, Balaenidae, Cetotheriidae, Eschrichtiidae, Monodontidae, Physeteridae, Kogiidae, Whales are creatures of the open ocean, they feed, mate, give birth, suckle and raise their young at sea. So extreme is their adaptation to life underwater that they are unable to survive on land. Whales range in size from the 2.6 metres and 135 kilograms dwarf sperm whale to the 29.9 metres and 190 metric tons blue whale, the sperm whale is the largest toothed predator on earth. Several species exhibit sexual dimorphism, in that the females are larger than males, baleen whales have no teeth, instead they have plates of baleen, a fringe-like structure used to expel water while retaining the krill and plankton which they feed on. They use their throat pleats to expand the mouth to take in huge gulps of water, balaenids have heads that can make up 40% of their body mass to take in water. Toothed whales, on the hand, have conical teeth designed for catching fish or squid. Some species, such as whales, are well adapted for diving to great depths to catch squid. Whales have evolved from land-living mammals, as such they must breathe air regularly, though they can remain submerged for long periods. They have blowholes located on top of their heads, through air is taken in. They are warm-blooded, and have a layer of fat, or blubber, under the skin, with streamlined fusiform bodies and two limbs that are modified into flippers, whales can travel at up to 20 knots, though they are not as flexible or agile as seals. Whales produce a variety of vocalizations, notably the extended songs of the humpback whale. Although whales are widespread, most species prefer the waters of the Northern and Southern Hemispheres. Species such as humpbacks and blue whales are capable of travelling thousands of miles without feeding, males typically mate with multiple females every year, but females only mate every two to three years. Calves are typically born in the spring and summer months and females bear all the responsibility for raising them, mothers of some species fast and nurse their young for one to two years. Once relentlessly hunted for their products, whales are now protected by international law, the North Atlantic right whales nearly became extinct in the twentieth century, with a population low of 450, and the North Pacific gray whale population is ranked Critically Endangered by the IUCN
