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Endangered species
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An endangered species is a species which has been categorized as likely to become extinct. In 2012, the IUCN Red List featured 3079 animal and 2655 plant species as endangered worldwide, the figures for 1998 were, respectively,1102 and 1197. Many nations have laws that protect conservation-reliant species, for example, population numbers, trends and species conservation status can be found in the lists of organisms by population. The conservation status of a species indicates the likelihood that it will become extinct, the IUCN Red List of Threatened Species is the best-known worldwide conservation status listing and ranking system. Over 40% of the species are estimated to be at risk of extinction. Internationally,199 countries have signed an accord to create Biodiversity Action Plans that will protect endangered, in the United States, such plans are usually called Species Recovery Plans. Those species of Near Threatened and Least Concern status have been assessed and found to have relatively robust and healthy populations, though these may be in decline. The IUCN categories, with examples of animals classified by them, include, Extinct Extinct in the wild Captive individuals survive, critically endangered Faces an extremely high risk of extinction in the immediate future. Endangered Faces a high risk of extinction in the near future, vulnerable Faces a high risk of endangerment in the medium term. Near-threatened May be considered threatened in the near future, Least concern No immediate threat to species survival. A population size reduction of ≥ 50%, projected or suspected to be met within the next 10 years or three generations, whichever is the longer, based on any of to under A1. E) Quantitative analysis showing the probability of extinction in the wild is at least 20% within 20 years or five generations, there is data from the United States that shows a correlation between human populations and threatened and endangered species. Under the Endangered Species Act in the United States, species may be listed as endangered or threatened, the Salt Creek tiger beetle is an example of an endangered subspecies protected under the ESA. Some endangered species laws are controversial, also lobbying from hunters and various industries like the petroleum industry, construction industry, and logging, has been an obstacle in establishing endangered species laws. The Bush administration lifted a policy that required federal officials to consult an expert before taking actions that could damage endangered species. Under the Obama administration, this policy has been reinstated, being listed as an endangered species can have negative effect since it could make a species more desirable for collectors and poachers. This effect is potentially reducible, such as in China where commercially farmed turtles may be reducing some of the pressure to poach endangered species. Another problem with the species is its effect of inciting the use of the shoot, shovel
2.
Endangered Species Act of 1973
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The U. S. Supreme Court found that the plain intent of Congress in enacting the ESA was to halt and reverse the trend toward species extinction, whatever the cost. The Act is administered by two agencies, the United States Fish and Wildlife Service and the National Oceanic and Atmospheric Administration. Experimental, nonessential populations of endangered species are treated as threatened species on land, for consultation purposes. The near-extinction of the bison and the disappearance of the passenger pigeon helped drive the call for wildlife conservation starting in the 1900s, the public was introduced to a new concept, extinction. Market hunting for the trade and for the table was one aspect of the problem. The early naturalists also killed birds and other wildlife for study, personal curio collections, while habitat losses continued as communities and farmland grew, the widespread use of pesticides and the introduction of non-native species also affected wildlife. One species in particular received widespread attention—the whooping crane, the species historical range extended from central Canada South to Mexico, and from Utah to the Atlantic coast. It would be eight years before the first national law regulating wildlife commerce was signed. The whooping crane population by 1941 was estimated at about only 16 birds still in the wild, the Lacey Act of 1900 was the first federal law that regulated commercial animal markets. It prohibited interstate commerce of animals killed in violation of state game laws, other legislation followed, including the Migratory Bird Conservation Act of 1929, a 1937 treaty prohibiting the hunting of right and gray whales, and the Bald Eagle Protection Act of 1940. These later laws had a low cost to society–the species were relatively little opposition was raised. Whereas the Lacey Act dealt with game management and market commerce species. The predecessor of the ESA was the Endangered Species Preservation Act of 1966, passed by Congress, this act permitted the listing of native U. S. animal species as endangered and for limited protections upon those animals. It also directed federal agencies to preserve habitat on their lands. The Act also consolidated and even expanded authority for the Secretary of the Interior to manage, other public agencies were encouraged, but not required, to protect species. The act did not address the commerce in endangered species and parts, in March,1967 the first list of endangered species was issued under the act. It included 14 mammals,36 birds,6 reptiles and amphibians and 22 fish and it included only vertebrates because the Department of Interiors definition of fish and wildlife was limited to vertebrates. However, with time, researchers noticed that the animals on the species list still were not getting enough protection
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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
4.
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
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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
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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
7.
Even-toed ungulate
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The even-toed ungulates are ungulates whose weight is borne equally by the third and fourth toes. By contrast, odd-toed ungulates, such as horses, bear their weight primarily on their third toe, the aquatic cetaceans evolved from within even-toed ungulates, and therefore modern taxonomic classification sometimes combines Artiodactyla and Cetacea into Cetartiodactyla. The oldest fossils of even-toed ungulates date back to the early Eocene, since these findings almost simultaneously appeared in Europe, Asia, and North America, it is very difficult to accurately determine the origin of artiodactyls. The fossils are classified as belonging to the family Dichobunidae, their best-known and these were small animals, some as small as a hare, with a slim build, lanky legs, and a long tail. The hind legs were longer than the front legs. The early to middle Eocene saw the emergence of the ancestors of most of todays mammals, two formerly widespread, but now extinct, families of even-toed ungulates were Enteledontidae and Anthracotheriidae. Entelodonts existed from the middle Eocene to the early Miocene in Eurasia and they had a stocky body with short legs and a massive head, which was characterized by two humps on the lower jaw bone. Anthracotheres had a large, porcine build, with short legs and this group appeared in the middle Eocene up until the Pliocene, and spread throughout Eurasia, Africa, and North America. Anthracothereres are thought to be the ancestors of hippos, and, likewise, hippopotamuses appeared in the late Miocene and occupied Africa and Asia – they never got to the Americas. The camels were, during parts of the Cenozoic, limited to North America. Among the North American camels were groups like the stocky, short-legged Merycoidodontidae and they first appeared in the late Eocene and developed a great diversity of species in North America. Only in the late Miocene or early Pliocene did they migrate from North America into Eurasia, the North American varieties became extinct around 10,000 years ago. Suina have been around since the Eocene, in the late Eocene or the Oligocene, two families stayed in Eurasia and Africa, the peccaries, which became extinct in the Old World, exist today only in the Americas. South America was settled by even-toed ungulates only in the Pliocene, with only the peccaries, lamoids, and various species of capreoline deer, South America has comparatively fewer artiodactyl families than other continents. The classification of artiodactyls was hotly debated because the ocean-dwelling cetaceans evolved from the land-dwelling even-toed ungulates, some semiaquatic even-toed ungulates are more closely related to the ocean-dwelling cetaceans than to the other even-toed ungulates. This makes the Artiodactyla as traditionally defined an invalid paraphyletic taxon, since it includes animals descended from a common ancestor, phylogenetic classification only recognizes monophyletic taxa, that is, groups that descend from a common ancestor and include all its descendants. To address this problem, the traditional order Artiodactyla and infraorder Cetacea are sometimes subsumed into the more inclusive Cetartiodactyla taxon, an alternative approach is to include both land-land dwelling even toed ungulates and ocean-dwelling cetaceans in a revised Artiodactyla taxon. Order Artiodactyla/Clade CetartiodactylaSuborder Tylopoda Family †Anoplotheriidae, molecular biology involves sequencing an organisms DNA and RNA and comparing the sequence with that of other living beings – the more similar they are, the more closely they are related
8.
Bovidae
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The Bovidae are the biological family of cloven-hoofed, ruminant mammals that includes bison, African buffalo, water buffalo, antelopes, gazelles, sheep, goats, muskoxen, and domestic cattle. A member of family is called a bovid. With 143 extant species and 300 known extinct species, the family Bovidae consists of eight major subfamilies apart from the disputed Peleinae and Pantholopinae, the family evolved 20 million years ago, in the early Miocene. The bovids show great variation in size and pelage colouration, excepting some domesticated forms, all male bovids have two or more horns, and in many species females possess horns, too. Most bovids bear 30 to 32 teeth, social activity and feeding usually peak during dawn and dusk. Bovids typically rest before dawn, during midday, and after dark and they have various methods of social organisation and social behaviour, which are classified into solitary and gregarious behaviour. Bovids use different forms of vocal, olfactory, and tangible communication, most species alternately feed and ruminate throughout the day. While small bovids forage in dense and closed habitat, larger species feed on vegetation in open grasslands. Mature bovids mate at least once a year and smaller species may even mate twice, the greatest diversities of bovids occur in Africa. The maximum concentration of species is in the savannas of eastern Africa, other bovid species also occur in Europe, Asia, and North America. Bovidae includes three of the five domesticated mammals whose use has spread outside their original ranges, namely cattle, sheep, dairy products such as milk, butter, and cheese are manufactured largely from domestic cattle. Bovids also provide leather, meat, and wool, the name Bovidae was given by the British zoologist John Edward Gray in 1821. The word Bovidae is the combination of the prefix bov- and the suffix -idae, the family Bovidae is placed in the order Artiodactyla. It includes 143 extant species, accounting for nearly 55% of the ungulates, molecular studies have supported monophyly in the family Bovidae. The number of subfamilies in Bovidae is disputed, with suggestions of as many as ten, in addition, three extinct subfamilies are known, Hypsodontinae, Oiocerinae and the subfamily Tethytraginae, which contains Tethytragus. In 1992, Alan W. Boodonts have somewhat primitive teeth, resembling those of oxen, a controversy exists about the recognition of Peleinae and Patholopinae, comprising the genera Pelea and Pantholops respectively, as subfamilies. Pantholops, earlier classified in the Antilopinae, was placed in its own subfamily. However, molecular and morphological analysis supports the inclusion of Pantholops in Caprinae, below is a cladogram based on Gatesy et al. and Gentry et al
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Caprinae
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Subfamily Caprinae is part of the ruminant family Bovidae, consisting of mostly medium-sized bovids. A member of this subfamily is called a caprine, within this subfamily Caprinae, a prominent tribe Caprini includes sheep, goat, and ibex. Some earlier taxonomies considered Caprinae a separate family called Capridae, but now it is considered a subfamily within the Bovidae family. The European mouflon is thought to be the ancestor of the domestic sheep. Many species have become extinct since the last ice age, probably largely because of human interaction, of the survivors, Five are classified as endangered, Eight as vulnerable, Seven as of concern and needing conservation measures, but at lower risk, and Seven species are secure. Members of the group vary considerably in size, from just over 1 m long for a full-grown grey goral, to almost 2.5 m long for a musk ox, musk oxen in captivity have reached over 650 kg. The resource-defenders are the primitive group, they tend to be smaller in size, dark in colour, males and females fairly alike, have long, tassellated ears, long manes. They tend to be larger, highly social, and rather than mark territory with scent glands, no sharp line divides the groups, but a continuum varies from the serows at one end of the spectrum to sheep, true goats, and musk oxen at the other. The goat-antelope, or caprid, group is known from as early as the Miocene, when members of the group resembled the modern serow in their general body form
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Ovis
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This article refers to the sheep genus. For the species referred to as sheep, see sheep. Ovis is a genus of mammals, part of the subfamily of the ruminant family Bovidae. Its five or more highly sociable species are known as sheep, the domestic sheep is one member of the genus, and is thought to be descended from the wild mouflon of central and southwest Asia. Female sheep are called ewes, males are called rams, the adjective applying to sheep is ovine, and the collective term for sheep is flock or mob. The term herd is also used in this sense. Many specialist terms relating to sheep are used. Sheep are usually stockier than most other bovines, and their horns are usually divergent, Sheep have scent glands on their faces and feet. Communication through the scent glands is not well understood, but is thought to be important for sexual signaling, males can smell females that are fertile and ready to mate, and rams mark their territories by rubbing scent on rocks. Like other ruminants, they have four-chambered stomachs, which play a role in digesting food, they eructate. Domestic sheep are used for their wool, milk, and meat, six species and numerous subspecies of sheep are currently recognised, although some subspecies have also been considered full species. These are the ones, Wild sheep are mostly found in hilly or mountainous habitats. They are fairly small compared to other ungulates, in most species and their diets consist mainly of grasses, as well as other plants and lichens. Like other bovids, their digestive systems enable them to digest and live on low-quality, Sheep conserve water well and can live in fairly dry environments. The bodies of wild sheep are covered by a coat of hair to protect them from cold. This coat contains long, stiff hairs, called kemps, over a short, woolly undercoat and this woolly undercoat has been developed in many domestic sheep breeds into a fleece of long wool, with selection against kemp hairs in these breeds. The fleece covers the body and is used for fibre, Sheep are social animals and live in groups, called flocks. This helps them to avoid predators and stay warm in bad weather by huddling together, flocks of sheep need to keep moving to find new grazing areas and more favourable weather as the seasons change
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Bighorn sheep
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The bighorn sheep is a species of sheep native to North America named for its large horns. These horns can weigh up to 14 kilograms, while the sheep themselves weigh up to 140 kg, recent genetic testing indicates three distinct subspecies of Ovis canadensis, one of which is endangered, O. c. sierrae. By 1900, the population had crashed to several thousand, due to diseases introduced through European livestock, divergence from their closest Asian ancestor occurred about 600,000 years ago. In North America, wild sheep diverged into two extant species—Dall sheep, which occupy Alaska and northwestern Canada, and bighorn sheep, which range from southern Canada to Mexico. However, the status of species is questionable given that hybridization has occurred between them in their recent evolutionary history. This subspecies has been extinct since 1925, California bighorn sheep, O. c. californiana, are found from British Columbia south to California and east to North Dakota. The definition of this subspecies has been updated, nelsons bighorn sheep, O. c. nelsoni, the most common desert bighorn sheep, ranges from California through Arizona. Mexican bighorn sheep, O. c. mexicana, range from Arizona and New Mexico south to Sonora and Chihuahua. Peninsular bighorn sheep O. c. cremnobates, occur in the Peninsular Ranges of California and Baja California Rocky Mountain bighorn sheep, weems bighorn sheep, O. c. weemsi, also are found in Baja California. However, starting in 1993, Ramey and colleagues, using DNA testing, have shown this division into seven subspecies is largely illusory, most scientists currently recognize three subspecies of bighorn. Thus the three subspecies of Ovis canadensis, Rocky Mountain bighorn sheep – occupying the U. S. and Canadian Rocky Mountains, Sierra Nevada bighorn sheep – formerly California bighorn sheep, a genetically distinct subspecies that only occurs in the Sierra Nevada in California. However, historic observer records suggest that bighorn sheep may have ranged as far west as the California Coastal Ranges which are contiguous to the Sierra Nevada via the Transverse Ranges. An account of sheep in the vicinity of the Mission San Antonio near Jolon, California. Desert bighorn sheep – occurring throughout the regions of the Southwestern United States. The 2016 genetics study suggested more modest divergence of this desert bighorn sheep into three lineages consistent with the work of Cowan, Nelson, Mexican, and Peninsular. These three lineages occupy desert biomes that vary significantly in climate, suggesting exposure to different selection regimes, Bighorn sheep are named for the large, curved horns borne by the rams. Ewes also have horns, but they are shorter with less curvature and they range in color from light brown to grayish or dark, chocolate brown, with a white rump and lining on the backs of all four legs. Males typically weigh 58–143 kg, are 90–105 cm tall at the shoulder, females are typically 34–91 kg, 75–90 cm tall, and 1. 28–1.58 m long
12.
Southwestern United States
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The population of the area is around 11 million people, with over half that in Arizona, the most populous cities are Phoenix, El Paso, Las Vegas, Albuquerque, and Tucson. Most of the area was part of the Viceroyalty of New Spain in the Spanish Empire before becoming part of Mexico and it became part of the United States through the Treaty of Guadalupe Hidalgo and the Gadsden Purchase. The deserts dominate the southern and western reaches of the area, the two major rivers of the region are the Colorado River, running in the northern and western areas, and the Rio Grande, running in the south. Formed approximately 8000 years ago, the Chihuahuan Desert is a dry desert. The Chihuahuan Desert spreads across the portion of the region, covering from southeastern Arizona, across southern New Mexico. While it is the second largest desert in the United States, only a third of the desert is within the United States, El Paso is the major city in this desert, with other smaller cities being Las Cruces and Roswell in New Mexico. The Chihuahuan is a rain shadow desert, formed two mountain ranges which block oceanic precipitation from reaching the area. The most prolific plants in this region are agave, yucca and creosote bushes, when people think of the desert southwest, the landscape of the Sonoran Desert is what mostly comes to mind. Rainfall averages between 4–12 inches per year, and the deserts most widely known inhabitant is the saguaro cactus and it is bounded on the northwest by the Mojave Desert, to the north by the Colorado Plateau and to the east by the Arizona Mountains forests and the Chihuahuan Desert. The portion of the Sonora Desert which lies in the Southwestern United States is the most populated area within the region. Six of the top ten major population centers of the region are found within its borders, Phoenix, Tucson, Mesa, Chandler, Glendale, also within its borders are Yuma and Prescott Arizona. The most northwest portion of the American Southwest is covered by the Mojave Desert, bordered on the south by the Sonoran Desert and the east by the Colorado Plateau, its range within the region makes up the southeast tip of Nevada, and the northwestern corner of Arizona. In terms of topography, the Mojave is very similar to the Great Basin Desert, the Mojave is the smallest, driest and hottest desert within the United States. The Mojave gets less than six inches of rain annually, the most prolific vegetation is the tall Joshua tree, which grow as tall as 40 feet, and are thought to live almost 1000 years. Other major vegetation includes the Parry saltbush and the Mojave sage, the Colorado Plateau varies from the large stands of forests in the west, including the largest stand of ponderosa pine trees in the world, to the Mesas to the east. Although not called a desert, the Colorado Plateau is mostly made up of high desert, the Plateau is characterized by a series of plateaus and mesas, interspersed with canyons. The most dramatic example is the Grand Canyon, but that is one of many dramatic vistas included within the Plateau, which includes spectacular lava formations, painted deserts, sand dunes, and badlands. One of the most distinctive features of the Plateau is its longevity, the Plateau can be divided into six sections, three of which fall into the Southwest region
