Habitat destruction is the process by which natural habitat becomes incapable of supporting its native species. In this process, the organisms that used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity is for the purpose of harvesting natural resources for industrial production and urbanization. Clearing habitats for agriculture is the principal cause of habitat destruction. Other important causes of habitat destruction include mining, logging and urban sprawl. Habitat destruction is ranked as the primary cause of species extinction worldwide, it is a process of natural environmental change that may be caused by habitat fragmentation, geological processes, climate change or by human activities such as the introduction of invasive species, ecosystem nutrient depletion, other human activities. The terms habitat loss and habitat reduction are used in a wider sense, including loss of habitat from other factors, such as water and noise pollution. In the simplest term, when a habitat is destroyed, the plants and other organisms that occupied the habitat have a reduced carrying capacity so that populations decline and extinction becomes more likely.
The greatest threat to organisms and biodiversity is the process of habitat loss. Temple found that 82% of endangered bird species were threatened by habitat loss. Most amphibian species are threatened by habitat loss, some species are now only breeding in modified habitat. Endemic organisms with limited ranges are most affected by habitat destruction because these organisms are not found anywhere else within the world, thus have less chance of recovering. Many endemic organisms have specific requirements for their survival that can only be found within a certain ecosystem, resulting in their extinction. Extinction may take place long after the destruction of habitat, a phenomenon known as extinction debt. Habitat destruction can decrease the range of certain organism populations; this can result in the reduction of genetic diversity and the production of infertile youths, as these organisms would have a higher possibility of mating with related organisms within their population, or different species.
One of the most famous examples is the impact upon China's giant panda, once found across the nation. Now it is only found in fragmented and isolated regions in the southwest of the country, as a result of widespread deforestation in the 20th century. Biodiversity hotspots are chiefly tropical regions that feature high concentrations of endemic species and, when all hotspots are combined, may contain over half of the world’s terrestrial species; these hotspots are suffering from habitat destruction. Most of the natural habitat on islands and in areas of high human population density has been destroyed. Islands suffering extreme habitat destruction include New Zealand, the Philippines, Japan. South and East Asia — China, Malaysia and Japan — and many areas in West Africa have dense human populations that allow little room for natural habitat. Marine areas close to populated coastal cities face degradation of their coral reefs or other marine habitat; these areas include the eastern coasts of Asia and Africa, northern coasts of South America, the Caribbean Sea and its associated islands.
Regions of unsustainable agriculture or unstable governments, which may go hand-in-hand experience high rates of habitat destruction. Central America, Sub-Saharan Africa, the Amazonian tropical rainforest areas of South America are the main regions with unsustainable agricultural practices and/or government mismanagement. Areas of high agricultural output tend to have the highest extent of habitat destruction. In the U. S. less than 25 % of native vegetation remains in many parts of the Midwest. Only 15% of land area remains unmodified by human activities in all of Europe. Tropical rainforests have received most of the attention concerning the destruction of habitat. From the 16 million square kilometers of tropical rainforest habitat that existed worldwide, less than 9 million square kilometers remain today; the current rate of deforestation is 160,000 square kilometers per year, which equates to a loss of 1% of original forest habitat each year. Other forest ecosystems have suffered as more destruction as tropical rainforests.
Farming and logging have disturbed at least 94% of temperate broadleaf forests. Tropical deciduous dry forests are easier to clear and burn and are more suitable for agriculture and cattle ranching than tropical rainforests. Plains and desert areas have been degraded to a lesser extent. Only 10-20% of the world's drylands, which include temperate grasslands and shrublands, deciduous forests, have been somewhat degraded, but included in that 10-20% of land is the 9 million square kilometers of seasonally dry-lands that humans have converted to deserts through the process of desertification. The tallgrass prairies of North America, on the other hand, have less than 3% of natural habitat remaining that has not been converted to farmland. Wetlands and marine areas have endured high levels of habitat destruction. More than 50% of wetlands in the U. S. have been destroyed in just the last 200 years. Between 60% and 70% of European wetlands have been destroyed. In the United Kingdom, there has been an i
The turtle shell is a complicated shield for the ventral and dorsal parts of turtles and terrapins enclosing all the vital organs of the turtle and in some cases the head. It is constructed of modified bony elements such as the ribs, parts of the pelvis and other bones found in most reptiles; the bone of the shell consists of both skeletal and dermal bone, showing that the complete enclosure of the shell evolved by including dermal armor into the rib cage. The shell of the turtle is an important study, not just because of the obvious protection it provides for the animal, but as an identification tool, in particular with fossils as the shell is one of the parts of a turtle to survive fossilization. Hence understanding the structure of the shell in living species gives us comparable material with fossils; the shell of the hawksbill turtle, among other species, has been used as a material for a wide range of small decorative and practical items since antiquity, but is referred to as tortoiseshell.
The turtle shell is made up of numerous bony elements named after similar bones in other vertebrates, a series of keratinous scutes which are uniquely named. Some of those bones that make the top of the shell, evolved from the scapula rami of the clavicles along with the dorsal and superficial migration of the clecthra; the ventral surface is called the plastron. These are joined by an area called the bridge; the actual suture between the bridge and the plastron is called the anterior bridge strut. In Pleurodires the posterior pelvis is part of the carapace fused with it; this is not the case in Cryptodires. The anterior bridge strut and posterior bridge strut are part of the plastron, on the carapace are the sutures into which they insert, known as the Bridge carapace suture; the bones of the shell are named for standard vertebrate elements. As such the carapace is made up of 8 pleurals on each side, these are a combination of the ribs and fused dermal bone. Outside of this at the anterior of the shell is the single nuchal bone, a series of 12 paired periphals extend along each side.
At the posterior of the shell is the pygal bone and in front of this nested behind the eighth pleurals is the suprapygal. Between each of the pleurals are a series of neural bones, which although always present are not always visible, in many species of Pleurodire they are submerged below the pleurals. Beneath the neural bone is the Neural arch which forms the upper half of the encasement for the spinal chord. Below this the rest of the vertebral column; some species of turtles have some extra bones called mesoplastra, which are located between the carapace and plastron in the bridge area. They are present in most Pelomedusid turtles; the skeletal elements of the plastron are largely in pairs. Anteriorly there are two epiplastra, with the hyoplastra behind them; these enclose the singuar entoplastron. These make up the front half of the plastron and the hyoplastron contains the anterior bridge strut; the posterior half is made up of two hypoplastra and the rear is a pair of xiphiplastra. Overlying the boney elements are a series of scutes, which are made of keratin and are a lot like horn or nail tissue.
In the center of the carapace are 5 vertebral scutes and out from these are 4 pairs of costal scutes. Around the edge of the shell are 12 pairs of marginal scutes. All these scutes are aligned so that for the most part the sutures between the bones are in the middle of the scutes above. At the anterior of the shell there may be a cervical scute however the presence or absence of this scute is variable within species. On the plastron there are two gular scutes at the front, followed by a pair of pectorals abdominals and lastly anals. A particular variation is the Pleurodiran turtles have an intergular scute between the gulars at the front, giving them a total of 13 plastral scutes. Compared to the 12 in all Cryptodiran turtles; the carapace is the dorsal, convex part of the shell structure of a turtle, consisting of the animal's ossified ribs fused with the dermal bone. The spine and expanded ribs are fused through ossification to dermal plates beneath the skin to form a hard shell. Exterior to the skin the shell is covered by scutes, which are horny plates made of keratin that protect the shell from scrapes and bruises.
A keel, a ridge that runs from front to the back of the animal is present in some species, these may be single, paired or three rows of them. In most turtles the shell is uniform in structure, species variation in general shape and color being the main differences; however the soft shell turtles, pig-nose turtles and the leatherback sea turtle have lost the scutes and reduced the ossification of the shell. This leaves the shell covered only by skin; these are all aquatic forms. The evolution of the turtle's shell is unique because of how the carapace represents transformed vertebrae and ribs. While other tetrapods have their scapula, or shoulder blades, found outside of the ribcage, the scapula for turtles is found inside the ribcage; the shells of other tetrapods, such as armadillos, are not linked directly to the vertebral column or rib cage allowing the ribs to move with the surrounding intercostal muscle. However, analysis of the transitional fossil, Eunotosaurus africanus shows that early ancestors of turtles lost that intercostal muscle found between the ribs.
Recent breakthroughs in stem-turtle fossil records contribute to the study of the evolution of the turtle's shell. The first piece of fossil record discovered, essential for building the evolution a
Turtles are diapsids of the order Testudines characterized by a special bony or cartilaginous shell developed from their ribs and acting as a shield. "Turtle" may refer to fresh-water and sea-dwelling testudines. The order Testudines includes both extinct species; the earliest known members of this group date from 220 million years ago, making turtles one of the oldest reptile groups and a more ancient group than snakes or crocodilians. Of the 356 known species alive today, some are endangered. Turtles are ectotherms—animals called cold-blooded—meaning that their internal temperature varies according to the ambient environment. However, because of their high metabolic rate, leatherback sea turtles have a body temperature, noticeably higher than that of the surrounding water. Turtles are classified as amniotes, along with other reptiles and mammals. Like other amniotes, turtles breathe air and do not lay eggs underwater, although many species live in or around water; the study of turtles is called cheloniology, after the Greek word for turtle.
It is sometimes called testudinology, after the Latin name for turtles. Differences exist in usage of the common terms turtle and terrapin, depending on the variety of English being used; these terms do not reflect precise biological or taxonomic distinctions. Turtle may either refer to the order as a whole, or to particular turtles that make up a form taxon, not monophyletic, or may be limited to only aquatic species. Tortoise refers to any land-dwelling, non-swimming chelonian. Terrapin is used to describe several species of small, hard-shell turtles those found in brackish waters. In North America, all chelonians are called turtles. Tortoise is used only in reference to terrestrial turtles or, more narrowly, only those members of Testudinidae, the family of modern land tortoises. Terrapin may refer to small semi-aquatic turtles that live in fresh and brackish water, in particular the diamondback terrapin. Although the members of the genus Terrapene dwell on land, they are referred to as box turtles rather than tortoises.
The American Society of Ichthyologists and Herpetologists uses "turtle" to describe all species of the order Testudines, regardless of whether they are land-dwelling or sea-dwelling, uses "tortoise" as a more specific term for slow-moving terrestrial species. In the United Kingdom, the word turtle is used for water-dwelling species, including ones known in the US as terrapins, but not for terrestrial species, which are known only as tortoises; the word chelonian is popular among veterinarians and conservationists working with these animals as a catch-all name for any member of the superorder Chelonia, which includes all turtles living and extinct, as well as their immediate ancestors. Chelonia is based on the Greek word for χελώνη chelone. Testudines, on the other hand, is based on the Latin word for testudo. Terrapin comes from an Algonquian word for turtle; some languages do not have this distinction. For example, in Spanish, the word tortuga is used for turtles and terrapins. A sea-dwelling turtle is tortuga marina, a freshwater species tortuga de río, a tortoise tortuga terrestre.
The largest living chelonian is the leatherback sea turtle, which reaches a shell length of 200 cm and can reach a weight of over 900 kg. Freshwater turtles are smaller, but with the largest species, the Asian softshell turtle Pelochelys cantorii, a few individuals have been reported up to 200 cm; this dwarfs the better-known alligator snapping turtle, the largest chelonian in North America, which attains a shell length of up to 80 cm and weighs as much as 113.4 kg. Giant tortoises of the genera Geochelone and others were widely distributed around the world into prehistoric times, are known to have existed in North and South America and Africa, they became extinct at the same time as the appearance of man, it is assumed humans hunted them for food. The only surviving giant tortoises are on the Seychelles and Galápagos Islands and can grow to over 130 cm in length, weigh about 300 kg; the largest chelonian was Archelon ischyros, a Late Cretaceous sea turtle known to have been up to 4.6 m long.
The smallest turtle is the speckled padloper tortoise of South Africa. It weighs about 140 g. Two other species of small turtles are the American mud turtles and musk turtles that live in an area that ranges from Canada to South America; the shell length of many species in this group is less than 13 cm in length. Turtles are divided according to how they retract their necks into their shells; the mechanism of neck retraction differs phylogenetically: the suborder Pleurodira retracts laterally to the side, anterior to shoulder girdles, while the suborder Cryptodira retracts straight back, between shoulder girdles. These motions are due to the morphology and arrangement of cervical vertebrae. Of all recent turtles, the cervical column consists of nine joints and eight vertebrae, which are individually independent. Since these vertebrae are not fused and are rounded, the neck is more flexible, being able to bend in the backwards and sideways directions; the primary function and evolutionary implicastion of neck retraction is thought to
Constantine Samuel Rafinesque
Constantine Samuel Rafinesque-Schmaltz, as he is known in Europe, was a nineteenth-century polymath born near Constantinople in the Ottoman Empire and self-educated in France. He traveled as a young man in the United States settling in Ohio in 1815, where he made notable contributions to botany and the study of prehistoric earthworks in North America, he contributed to the study of ancient Mesoamerican linguistics, in addition to work he had completed in Europe. Rafinesque was eccentric, is portrayed as an erratic genius, he was an autodidact who excelled in various fields of knowledge, as a zoologist, botanist and polyglot. He wrote prolifically on such diverse topics as anthropology, biology and linguistics, but was honored in none of these fields during his lifetime. Among his theories were that ancestors of Native Americans had migrated by the Bering Sea from Asia to North America, that the Americas were populated by numerous black indigenous peoples at the time of European contact. Rafinesque was born on October 1783 in Galata, a suburb of Constantinople.
His father F. G. Rafinesque was a French merchant from Marseilles, his father died in Philadelphia about 1793. Rafinesque spent his youth in Marseilles, was self-educated. By the age of twelve, he had begun collecting plants for a herbarium. By fourteen, he taught himself perfect Greek and Latin because he needed to follow footnotes in the books he was reading in his paternal grandmother's libraries. In 1802, at the age of nineteen, Rafinesque sailed to Philadelphia in the United States with his younger brother, they traveled through Pennsylvania and Delaware, where he made the acquaintance of most of the young nation's few botanists. In 1805 Rafinesque returned to Europe with his collection of botanical specimens, settled in Palermo, where he learned Italian, he became so successful in trade that he retired by age twenty-five and devoted his time to natural history. For a time Rafinesque worked as secretary to the American consul. During his stay in Sicily, he studied fishes, naming many new discovered species of each.
He was elected a Fellow of the American Academy of Arts and Sciences in 1808. Rafinesque had a common-law wife. After their son died in 1815, he returned to the United States; when his ship Union foundered near the coast of Connecticut, he lost all his books and all his specimens. Settling in New York, Rafinesque became a founding member of the newly established "Lyceum of Natural History." In 1817 his book Florula Ludoviciana or A Flora of the State of Louisiana was criticized by fellow botanists, which caused his writings to be ignored. By 1818, he had named more than 250 new species of plants and animals, he was rebuilding his collection of objects from nature. In the summer of 1818, in Henderson, Rafinesque made the acquaintance of fellow naturalist John James Audubon, in fact stayed in Audubon's home for some three weeks. Audubon, although enjoying Rafinesque's company, took advantage of him in practical jokes involving fantastic, made-up species. In 1819 Rafinesque became professor of botany at Transylvania University in Lexington, where he gave private lessons in French and Spanish.
He was loosely associated with John D. Clifford, a merchant, interested in the ancient earthworks which remained throughout the Ohio Valley. Clifford conducted archival research, seeking the origins of these mounds, Rafinesque measured and mapped them; some had been lost to American development. He was elected a member of the American Antiquarian Society in 1820. Rafinesque started recording all the new species of plants and animals he encountered in travels throughout the state, he was considered an erratic student of higher plants. In the spring of 1826, he left the university after quarreling with its president, he traveled and lectured in various places, endeavored to establish a magazine and a botanic garden, but without success. He moved to a center of publishing and research, without employment, he published The Atlantic Journal and Friend of Knowledge, a Cyclopædic Journal and Review, of which only eight issues were printed. He gave public lectures and continued publishing at his own expense.
Rafinesque died of stomach and liver cancer in Philadelphia on September 18, 1840. It has been speculated that the cancer may have been induced by Rafinesque's self-medication years before with a mixture containing maidenhair fern, he was buried in a plot in. In March 1924 what were thought to be his remains were transported to Transylvania University and reinterred in a tomb under a stone inscribed, "Honor to whom honor is overdue." Rafinesque published 6,700 binomial names of plants, many of which have priority over more familiar names. The quantity of new taxa he produced, both plants and animals, has made Rafinesque memorable or notorious among biologists. Rafinesque applied to join the Lewis and Clark Expedition, but was twice turned down by Thomas Jefferson. After studying the specimens collected by the expedition, he assigned scientific names to the black-tailed prairie dog, the white-footed mouse and the mule deer. Rafinesque was one of the first to use the term "evolution" in the context of biological speciation.
Rafinesque proposed a theory of evolution before Charles Darwin. In a letter in 1832, Rafinesque wrote: The truth is that Species and Genera are forming i
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period, 419.2 Mya. The Silurian is the shortest period of the Paleozoic Era; as with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by several million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when 60% of marine species were wiped out. A significant evolutionary milestone during the Silurian was the diversification of jawed fish and bony fish. Multi-cellular life began to appear on land in the form of small, bryophyte-like and vascular plants that grew beside lakes and coastlines, terrestrial arthropods are first found on land during the Silurian. However, terrestrial life would not diversify and affect the landscape until the Devonian; the Silurian system was first identified by British geologist Roderick Murchison, examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s.
He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick, who had named the period of his study the Cambrian, from the Latin name for Wales. This naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. In 1835 the two men presented a joint paper, under the title On the Silurian and Cambrian Systems, Exhibiting the Order in which the Older Sedimentary Strata Succeed each other in England and Wales, the germ of the modern geological time scale; as it was first identified, the "Silurian" series when traced farther afield came to overlap Sedgwick's "Cambrian" sequence, provoking furious disagreements that ended the friendship. Charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was "Gotlandian" after the strata of the Baltic island of Gotland; the French geologist Joachim Barrande, building on Murchison's work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge.
He divided the Silurian rocks of Bohemia into eight stages. His interpretation was questioned in 1854 by Edward Forbes, the stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the original groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils; the Llandovery Epoch lasted from 443.8 ± 1.5 to 433.4 ± 2.8 mya, is subdivided into three stages: the Rhuddanian, lasting until 440.8 million years ago, the Aeronian, lasting to 438.5 million years ago, the Telychian. The epoch is named for the town of Llandovery in Wales; the Wenlock, which lasted from 433.4 ± 1.5 to 427.4 ± 2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in England. During the Wenlock, the oldest-known tracheophytes of the genus Cooksonia, appear; the complexity of later Gondwana plants like Baragwanathia, which resembled a modern clubmoss, indicates a much longer history for vascular plants, extending into the early Silurian or Ordovician.
The first terrestrial animals appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ± 1.5 to 423 ± 2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, the Ludfordian stage. It is named for the town of Ludlow in England; the Přídolí, lasting from 423 ± 1.5 to 419.2 ± 2.8 mya, is the final and shortest epoch of the Silurian. It is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a cadastral field area. In North America a different suite of regional stages is sometimes used: Cayugan Lockportian Tonawandan Ontarian Alexandrian In Estonia the following suite of regional stages is used: Ohessaare stage Kaugatuma stage Kuressaare stage Paadla stage Rootsiküla stage Jaagarahu stage Jaani stage Adavere stage Raikküla stage Juuru stage With the supercontinent Gondwana covering the equator and much of the southern hemisphere, a large ocean occupied most of the northern half of the globe.
The high sea levels of the Silurian and the flat land resulted in a number of island chains, thus a rich diversity of environmental settings. During the Silurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late-Ordovician glaciation; the southern continents remained united during this period. The melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity; the continents of Avalonia and Laurentia drifted together near the equator, starting the formation of a second supercontinent known as Euramerica. When the proto-Europe coll
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals have mouthparts adapted to rasping or grinding. Horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, other tough plant material. A large percentage of herbivores have mutualistic gut flora that help them digest plant matter, more difficult to digest than animal prey; this flora is made up of cellulose-digesting bacteria. Herbivore is the anglicized form of a modern Latin coinage, cited in Charles Lyell's 1830 Principles of Geology. Richard Owen employed the anglicized term in an 1854 work on fossil skeletons. Herbivora is derived from the Latin herba meaning a small plant or herb, vora, from vorare, to eat or devour. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants and photosynthesizing bacteria.
More organisms that feed on autotrophs in general are known as primary consumers. Herbivory is limited to animals that eat plants. Fungi and protists that feed on living plants are termed plant pathogens, while fungi and microbes that feed on dead plants are described as saprotrophs. Flowering plants that obtain nutrition from other living plants are termed parasitic plants. There is, however, no single exclusive and definitive ecological classification of consumption patterns. In zoology, an herbivore is an animal, adapted to eat plant matter. Our understanding of herbivory in geological time comes from three sources: fossilized plants, which may preserve evidence of defence, or herbivory-related damage. Although herbivory was long thought to be a Mesozoic phenomenon, fossils have shown that within less than 20 million years after the first land plants evolved, plants were being consumed by arthropods. Insects fed on the spores of early Devonian plants, the Rhynie chert provides evidence that organisms fed on plants using a "pierce and suck" technique.
During the next 75 million years, plants evolved a range of more complex organs, such as roots and seeds. There is no evidence of any organism being fed upon until the middle-late Mississippian, 330.9 million years ago. There was a gap of 50 to 100 million years between the time each organ evolved and the time organisms evolved to feed upon them. Further than their arthropod status, the identity of these early herbivores is uncertain. Hole feeding and skeletonisation are recorded in the early Permian, with surface fluid feeding evolving by the end of that period. Herbivory among four-limbed terrestrial vertebrates, the tetrapods developed in the Late Carboniferous. Early tetrapods were large amphibious piscivores. While amphibians continued to feed on fish and insects, some reptiles began exploring two new food types and plants; the entire dinosaur order ornithischia was composed with herbivores dinosaurs. Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation.
In contrast, a complex set of adaptations was necessary for feeding on fibrous plant materials. Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities. Tetrapod herbivores made their first appearance in the fossil record of their jaws near the Permio-Carboniferous boundary 300 million years ago; the earliest evidence of their herbivory has been attributed to dental occlusion, the process in which teeth from the upper jaw come in contact with teeth in the lower jaw is present. The evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns. Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores; this suggests that evolution and spread occurred within various lineages. Herbivores form an important link in the food chain because they consume plants in order to digest the carbohydrates photosynthetically produced by a plant.
Carnivores in turn consume herbivores for the same reason, while omnivores can obtain their nutrients from either plants or animals. Due to a herbivore's ability to survive on tough and fibrous plant matter, they are termed the primary consumers in the food cycle. Herbivory and omnivory can be regarded as special cases of Consumer-Resource Systems. Herbivores come in all sizes in the animal kingdom, they include aquatic and non-aquatic vertebrates. They can be large, like an elephant. Many herbivores found living in close proximity to humans, such as rodents, cows and camels. Two herbivore feeding strategies are browsing. For a terrestrial mammal to be called a grazer, at least 90% of the forage has to be grass, for a browser at least 90% tree leaves and/or twigs. An intermediate feeding strategy is called "mixed-feeding". In their daily need to take up energy from forage, herbivores of different body mass may be selective in choosing their food. "Selective" means that herbivores may choose their forage source depending on, e.g. season or food avail
The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period, 298.9 Mya. The name Carboniferous means "coal-bearing" and derives from the Latin words carbō and ferō, was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the modern'system' names to be employed, reflects the fact that many coal beds were formed globally during that time; the Carboniferous is treated in North America as two geological periods, the earlier Mississippian and the Pennsylvanian. Terrestrial animal life was well established by the Carboniferous period. Amphibians were the dominant land vertebrates, of which one branch would evolve into amniotes, the first terrestrial vertebrates. Arthropods were very common, many were much larger than those of today. Vast swaths of forest covered the land, which would be laid down and become the coal beds characteristic of the Carboniferous stratigraphy evident today.
The atmospheric content of oxygen reached its highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. The half of the period experienced glaciations, low sea level, mountain building as the continents collided to form Pangaea. A minor marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred at the end of the period, caused by climate change. In the United States the Carboniferous is broken into Mississippian and Pennsylvanian subperiods; the Mississippian is about twice as long as the Pennsylvanian, but due to the large thickness of coal-bearing deposits with Pennsylvanian ages in Europe and North America, the two subperiods were long thought to have been more or less equal in duration. In Europe the Lower Carboniferous sub-system is known as the Dinantian, comprising the Tournaisian and Visean Series, dated at 362.5-332.9 Ma, the Upper Carboniferous sub-system is known as the Silesian, comprising the Namurian and Stephanian Series, dated at 332.9-298.9 Ma.
The Silesian is contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, the Westphalian as the Coal Measures and Pennant Sandstone; the International Commission on Stratigraphy faunal stages from youngest to oldest, together with some of their regional subdivisions, are: A global drop in sea level at the end of the Devonian reversed early in the Carboniferous. There was a drop in south polar temperatures; these conditions had little effect in the deep tropics, where lush swamps to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major marine extinction, one that hit crinoids and ammonites hard; this sea level drop and the associated unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation.
The Carboniferous was a time of active mountain-building as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America; this continental collision resulted in the Hercynian orogeny in Europe, the Alleghenian orogeny in North America. In the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural Mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, South China continents were still separated from Laurasia; the Late Carboniferous Pangaea was shaped like an "O." There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, inside the "O" in the Carboniferous Pangaea. Other minor oceans were shrinking and closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean. Average global temperatures in the Early Carboniferous Period were high: 20 °C.
However, cooling during the Middle Carboniferous reduced average global temperatures to about 12 °C. Lack of growth rings of fossilized trees suggest a lack of seasons of a tropical climate. Glaciations in Gondwana, triggered by Gondwana's southward movement, continued into the Permian and because of the lack of clear markers and breaks, the deposits of this glacial period are referred to as Permo-Carboniferous in age; the cooling and drying of the climate led to the Carboniferous Rainforest Collapse during the late Carboniferous. Tropical rainforests fragmented and were devastated by climate change. Carboniferous rocks in Europe and eastern North America consist of a repeated sequence of limestone, sandstone and coal beds. In North America, the early Carboniferous is marine