1.
Taxonomy (biology)
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Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate
2.
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
3.
Chordate
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Chordates are deuterostomes, as during the embryo development stage the anus forms before the mouth. They are also bilaterally symmetric coelomates, in the case of vertebrate chordates, the notochord is usually replaced by a vertebral column during development, and they may have body plans organized via segmentation. There are also additional extinct taxa, the Vertebrata are sometimes considered as a subgroup of the clade Craniata, consisting of chordates with a skull, the Craniata and Tunicata compose the clade Olfactores. Of the more than 65,000 living species of chordates, the worlds largest and fastest animals, the blue whale and peregrine falcon respectively, are chordates, as are humans. Fossil chordates are known from at least as early as the Cambrian explosion, Hemichordata, which includes the acorn worms, has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum. The Hemichordata, along with the Echinodermata, form the Ambulacraria, the Chordata and Ambulacraria form the superphylum Deuterostomia, composed of the deuterostomes. Attempts to work out the relationships of the chordates have produced several hypotheses. All of the earliest chordate fossils have found in the Early Cambrian Chengjiang fauna. Because the fossil record of early chordates is poor, only molecular phylogenetics offers a prospect of dating their emergence. However, the use of molecular phylogenetics for dating evolutionary transitions is controversial and it has also proved difficult to produce a detailed classification within the living chordates. Attempts to produce family trees shows that many of the traditional classes are paraphyletic. While this has been known since the 19th century, an insistence on only monophyletic taxa has resulted in vertebrate classification being in a state of flux. Although the name Chordata is attributed to William Bateson, it was already in prevalent use by 1880, ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866. Though he used the German vernacular form, it is allowed under the ICZN code because of its subsequent latinization, among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail. In fish and other vertebrates, this develops into the spinal cord, the pharynx is the part of the throat immediately behind the mouth. In fish, the slits are modified to form gills, a muscular tail that extends backwards behind the anus. This is a groove in the wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus and it also stores iodine, and may be a precursor of the vertebrate thyroid gland
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.
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
6.
North African ostrich
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The North African ostrich or red-necked ostrich, also known as the Barbary ostrich, is the largest subspecies of the common ostrich from West and North Africa, making it the largest living bird. The North African ostrich is the largest subspecies of S. camelus, at 2.74 m in height, the neck is pinkish-red, the plumage of males is black and white, and the plumage of females is grey. The North African ostrich was once widespread in western and northern Africa and it used to range from Ethiopia and Sudan in the east throughout the Sahel to Senegal and Mauritania in the west, and north to Egypt and southern Morocco. It has now disappeared from parts of this range and it only remains in 6 of the 18 countries where it originally occurred. This subspecies may also have occurred in the Sinai Peninsula, where Arabian ostriches once lived, North African ostriches can be found in open fields and the savannahs, especially in the Sahel of Africa. In Asia, the introduced North African ostriches live in grasslands, semi-deserts, the North African ostrich had dramatically declined to the point where it is now included on CITES Appendix I and some treat it as Critically Endangered. The North African ostrich was the most widespread subspecies of ostrich and it formerly had an extensive range but is now thought to live in fragmented pockets in Cameroon, Chad, Central African Republic and Senegal, whilst extinct in most of its range in northern Africa. Reintroduction projects for the ostriches have begun, especially in northern Sahara, ostriches were imported from Chad and reintroduced to Souss-Massa National Park in Morocco. In Tunisia, North African ostriches were once common in the region of the country. The subspecies had been extirpated since 1887, in 2014, North African ostriches were finally returned to Tunisia after 127 years of being extinct. The birds were first reintroduced to Dghoumès National Park and they were then reintroduced to Sidi Toui National Park, and then to Orbata Faunal Reserve. It is planned that the ostrich will also recover in other countries from western to northeastern Africa, such as Niger. The North African ostrich is the closest relative to the Arabian ostrich from Western Asia, in 1988-89, the ostriches, originally taken from Sudan, were introduced to National Wildlife Research Center in Saudi Arabia. A reintroduction project using the North African ostriches was set up at Mahazat as-Sayd Protected Area in 1994, currently, it is estimated that 90 to 100 individuals are living within the reserve. It was proposed that the North African ostriches should also reintroduced to Al-Khunfah Protected Area and it also has been reintroduced in the Yotvata Hai-Bar Nature Reserve from Israel as well and some will eventually be released in open fields of the Negev desert. However, the failed, as the reintroduced ostriches vanished. The red-necked ostriches were previously found at the Eilat mountains, the Negev desert and it is thought that the vanished species may have left Israel for Egypt or the Nahal Seifim. The reintroduction project for the ostriches was on hiatus, but the authority might try again in the future and it is hoped that Jordan and Egypt would collaborate with Israel to ensure that the ostriches can live in a broader range
7.
Arabian ostrich
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The Arabian ostrich or Syrian ostrich is an extinct subspecies of the ostrich which lived on the Arabian Peninsula and in the Near East until the mid-20th century. Towards the Sinai Peninsula, it probably intergraded with the North African subspecies camelus in earlier times and it looked exactly like that form, possibly, the females were of a slightly lighter coloration. The only certain way to distinguish camelus and syriacus was the size of the latter, with only marginal overlap. The Arabian ostrich has long had a significant place in the culture of the region, an adult with 11 offspring is featured on the famous prehistoric Graffiti Rock I near Riyadh. In Mesopotamia, it was used as an animal and featured in artwork, painted on cups and other objects made from ostrich eggs. In Tang China, an ostrich was a welcome exotic gift fit for an emperor, ostriches figure in the decoration of the Qianling Mausoleum, the Jewish view of this bird was less favorable. In Roman times, there was a demand for ostriches to use in games or cooking. Arabian ostrich products, as well as birds, were exported as far as China. A Tang Dynasty source states that the camel bird inhabiting Arabia is four chi and more in height, its feet resembling those of a camel, its neck is very strong, the Arabian ostrich is mentioned by T. E. Lawrence in Seven Pillars of Wisdom when one Arabian tribe brings eggs to Faisal I of Iraq as a peace offering and it is mentioned that the ostrich is plentiful in that tribes territory. The widespread introduction of firearms and, later, motor vehicles marked the start of the decline towards extinction of this subspecies. Earlier hunting methods with bow, arrows and dogs had allowed most animals of a group to escape, by the early 20th century, the Arabian ostrich had become rare. Remains of old eggs are found in the former range of the southern subpopulation. Some eggshell fragments were collected by St. John Philby from Mahadir Summan, Arabia, today the North African ostrich has been re-introduced from captivity to the open areas of the Negev in Israel where the Arabian ostrich lived before. On Some Animals Mentioned in the Bible, all the birds of the Bible, Their stories, identification and meaning. Checklist of Birds of the World, description of a new subspecies of Ostrich from Syria. Bulletin of the British Ornithologists Club, robinson, Terence J. Matthee, Conrad A. Molecular genetic relationships of the ostrich, Struthio camelus syriacus
8.
Ethiopia
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Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It shares borders with Eritrea to the north and northeast, Djibouti and Somalia to the east, Sudan and South Sudan to the west, and Kenya to the south. With nearly 100 million inhabitants, Ethiopia is the most populous landlocked country in the world and it occupies a total area of 1,100,000 square kilometres, and its capital and largest city is Addis Ababa. Some of the oldest evidence for modern humans has been found in Ethiopia. It is widely considered as the region from modern humans first set out for the Middle East. According to linguists, the first Afroasiatic-speaking populations settled in the Horn region during the ensuing Neolithic era, tracing its roots to the 2nd millennium BC, Ethiopia was a monarchy for most of its history. During the first centuries AD, the Kingdom of Aksum maintained a unified civilization in the region, subsequently, many African nations adopted the colors of Ethiopias flag following their independence. It was the first independent African member of the 20th-century League of Nations, Ethiopias ancient Geez script, also known as Ethiopic, is one of the oldest alphabets still in use in the world. The Ethiopian calendar, which is seven years and three months behind the Gregorian calendar, co-exists alongside the Borana calendar. A slight majority of the population adheres to Christianity, while around a third follows Islam, the country is the site of the Migration to Abyssinia and the oldest Muslim settlement in Africa at Negash. A substantial population of Ethiopian Jews, known as Bete Israel, resided in Ethiopia until the 1980s, Ethiopia is a multilingual nation with around 80 ethnolinguistic groups, the four largest of which are the Oromiffa, Amhara, Somali, and Tigrayans. Most people in the country speak Afroasiatic languages of the Cushitic or Semitic branches, additionally, Omotic languages are spoken by ethnic minority groups inhabiting the southern regions. Nilo-Saharan languages are spoken by the nations Nilotic ethnic minorities. Ethiopia is the place of origin for the coffee bean which originated from the place called Kefa and it is a land of natural contrasts, with its vast fertile West, jungles, and numerous rivers, and the worlds hottest settlement of Dallol in its north. The Ethiopian Highlands are Africas largest continuous mountain ranges, and Sof Omar Caves contain Africas largest cave, Ethiopia has the most UNESCO World Heritage Sites in Africa. Ethiopia is one of the members of the UN, the Group of 24, the Non-Aligned Movement, G-77. In the 1970s and 1980s, Ethiopia suffered from civil wars, the country has begun to recover recently however, and now has the largest economy in East Africa and Central Africa. According to Global Fire Power, Ethiopia has the 42nd most powerful military in the world, the origin of the word Ethiopia is uncertain
9.
Somalia
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Somalia, officially the Federal Republic of Somalia, is a country located in the Horn of Africa. It is bordered by Ethiopia to the west, Djibouti to the northwest, the Gulf of Aden to the north, the Indian Ocean to the east, Somalia has the longest coastline on Africas mainland, and its terrain consists mainly of plateaus, plains and highlands. Climatically, hot conditions prevail year-round, with monsoon winds. Somalia has an population of around 12.3 million. Around 85% of its residents are ethnic Somalis, who have inhabited the northern part of the country. Ethnic minorities are largely concentrated in the southern regions, the official languages of Somalia are Somali and Arabic, both of which belong to the Afroasiatic family. Most people in the country are Muslim, with the majority being Sunni, in antiquity, Somalia was an important commercial centre. It is among the most probable locations of the fabled ancient Land of Punt, during the Middle Ages, several powerful Somali empires dominated the regional trade, including the Ajuran Empire, the Adal Sultanate, the Warsangali Sultanate, and the Geledi Sultanate. The toponym Somalia was coined by the Italian explorer Luigi Robecchi Bricchetti, Italian occupation lasted until 1941, yielding to British military administration. British Somaliland would remain a protectorate, while Italian Somaliland in 1949 became a United Nations Trusteeship under Italian administration, in 1960, the two regions united to form the independent Somali Republic under a civilian government. The Supreme Revolutionary Council seized power in 1969 and established the Somali Democratic Republic, led by Mohamed Siad Barre, this government later collapsed in 1991 as the Somali Civil War broke out. Various armed factions began competing for influence in the power vacuum, during this period, due to the absence of a central government, Somalia was a failed state, and residents returned to customary and religious law in most regions. A few autonomous regions, including the Somaliland and Puntland administrations emerged in the north, the early 2000s saw the creation of fledgling interim federal administrations. The Transitional National Government was established in 2000, followed by the formation of the Transitional Federal Government in 2004, in 2006, the TFG, assisted by Ethiopian troops, assumed control of most of the nations southern conflict zones from the newly formed Islamic Courts Union. The ICU subsequently splintered into more radical groups such as Al-Shabaab, by mid-2012, the insurgents had lost most of the territory that they had seized. In 2011–2012, a political process providing benchmarks for the establishment of permanent democratic institutions was launched, within this administrative framework a new provisional constitution was passed in August 2012, which reformed Somalia as a federation. Somalia has maintained an informal economy, mainly based on livestock, remittances from Somalis working abroad, Somalia has been inhabited since at least the Paleolithic. During the Stone Age, the Doian and Hargeisan cultures flourished here, the oldest evidence of burial customs in the Horn of Africa comes from cemeteries in Somalia dating back to the 4th millennium BCE
10.
Ecology
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Ecology is the scientific analysis and study of interactions among organisms and their environment. It is a field that includes biology, geography. Ecology includes the study of interactions that organisms have with other, other organisms. Ecosystems are composed of dynamically interacting parts including organisms, the communities make up. Ecosystem processes, such as production, pedogenesis, nutrient cycling. These processes are sustained by organisms with specific life history traits, biodiversity, which refers to the varieties of species, genes, and ecosystems, enhances certain ecosystem services. Ecology is not synonymous with environment, environmentalism, natural history and it is closely related to evolutionary biology, genetics, and ethology. An important focus for ecologists is to improve the understanding of how biodiversity affects ecological function, Ecology is a human science as well. For example, the Circles of Sustainability approach treats ecology as more than the environment out there and it is not treated as separate from humans. Organisms and resources compose ecosystems which, in turn, maintain biophysical feedback mechanisms that moderate processes acting on living and non-living components of the planet, the word ecology was coined in 1866 by the German scientist Ernst Haeckel. Ecological thought is derivative of established currents in philosophy, particularly from ethics and politics, ancient Greek philosophers such as Hippocrates and Aristotle laid the foundations of ecology in their studies on natural history. Modern ecology became a more rigorous science in the late 19th century. Evolutionary concepts relating to adaptation and natural selection became the cornerstones of modern ecological theory, the scope of ecology contains a wide array of interacting levels of organization spanning micro-level to a planetary scale phenomena. Ecosystems, for example, contain abiotic resources and interacting life forms, an ecosystems area can vary greatly, from tiny to vast. A single tree is of consequence to the classification of a forest ecosystem. Several generations of a population can exist over the lifespan of a single leaf. Each of those aphids, in turn, support diverse bacterial communities, biodiversity describes the diversity of life from genes to ecosystems and spans every level of biological organization. The term has several interpretations, and there are ways to index, measure, characterize
11.
Grazing
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Grazing is a method of feeding in which a herbivore feeds on plants such as grasses, or other multicellular organisms such as algae. In agriculture, grazing is one method used whereby domestic livestock are used to convert grass and other forage into meat, milk, many small selective herbivores follow larger grazers, who skim off the highest, tough growth of plants, exposing tender shoots. For terrestrial animals, grazing is normally distinguished from browsing in that grazing is eating grass or forbs, Grazing differs from true predation because the organism being grazed upon is not generally killed. Grazing differs from parasitism as the two live together in a constant state of physical externality. Water animals that feed for example on algae found on stones are called grazers-scrapers, grazers-scrapers feed also on microorganisms and dead organic matter on various substrates. Grazing is a method of feeding in which a herbivore feeds on such as grasses. In zoology, graminivory is a form of grazing, a graminivore is an herbivorous animal that feeds primarily on grass. The word is derived from Latin graminis, meaning grass, and vorare, horses, cattle, capybara, hippopotamuses, grasshoppers, geese, and giant pandas are examples of graminivores. Some carnivores, such as dogs and cats, are known to eat grass occasionally, giant pandas have evolved to be obligate bamboo grazers, and 99% of their diet consists of sub-alpine bamboo species. Rabbits are herbivores that feed by grazing on grass, forbs and they graze heavily and rapidly for about the first half-hour of a grazing period, followed by about half an hour of more selective feeding. If the environment is relatively non-threatening, the rabbit will remain outdoors for many hours and their diet contains large amounts of cellulose, which is hard to digest. Rabbits solve this problem by using a form of hindgut fermentation and they pass two distinct types of feces, hard droppings and soft black viscous pellets, the latter of which are known as caecotrophs and are immediately eaten. Rabbits reingest their own droppings to digest their food further and extract sufficient nutrients, capybara are herbivores that graze mainly on grasses and aquatic plants, as well as fruit and tree bark. As with other grazers, they can be selective and will feed on the leaves of one species. They eat a variety of plants during the dry season. While they eat grass during the wet season, they have to switch to more abundant reeds during the dry season, the capybaras jaw hinge is not perpendicular and therefore they chew food by grinding back-and-forth rather than side-to-side. Capybara are coprophagous, as a source of gut flora, to help digest the cellulose in the grass that forms their normal diet. They may also regurgitate food to masticate again, similar to cud-chewing by a cow, as with other rodents, the front teeth of capybara grow continually to compensate for the constant wear from eating grasses, their cheek teeth also grow continuously
12.
Savanna
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A savanna or savannah is a mixed woodland grassland ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support a herbaceous layer consisting primarily of grasses. Savannas maintain an open canopy despite a high tree density and it is often believed that savannas feature widely spaced, scattered trees. However, in savannas, tree densities are higher and trees are more regularly spaced than in forests. Savanna covers approximately 20% of the Earths land area, the word originally entered English in 1555 as the Latin Zauana, equivalent in the orthography of the times to zavana. Peter Martyr reported it as the name for the plain around Comagre. The accounts are inexact, but this is placed in present-day Madugandí or at points on the nearby Guna Yala coast opposite Ustupo or on Point Mosquitos. These areas are now given over to modern cropland or jungle. The common usage meaning to describe vegetation now conflicts with a simplified yet widespread climatic concept meaning, the divergence has sometimes caused areas such as extensive savannas north and south of the Congo and Amazon Rivers to be excluded from mapped savanna categories. Barrens has been used almost interchangeably with savanna in different parts of North America, sometimes midwestern savanna were described as grassland with trees. Different authors have defined the limits of savanna tree coverage as 5–10%. Two factors common to all environments are rainfall variations from year to year. In the Americas, e. g. in Belize, Central America, savanna vegetation is similar from Mexico to South America, savannas are subject to regular wildfires and the ecosystem appears to be the result of human use of fire. For example, Native Americans created the Pre-Columbian savannas of North America by periodically burning where fire-resistant plants were the dominant species, pine barrens in scattered locations from New Jersey to coastal New England are remnants of these savannas. Aboriginal burning appears to have responsible for the widespread occurrence of savanna in tropical Australia and New Guinea. The maquis shrub savannas of the Mediterranean region were created and maintained by anthropogenic fire. These fires are usually confined to the layer and do little long term damage to mature trees. However, these either kill or suppress tree seedlings, thus preventing the establishment of a continuous tree canopy which would prevent further grass growth
