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.
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
5.
Primate
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A primate is a mammal of the order Primates. In taxonomy, primates include two distinct lineages, strepsirrhines and haplorhines, Primates arose from ancestors that lived in the trees of tropical forests, many primate characteristics represent adaptations to life in this challenging three-dimensional environment. Most primate species remain at least partly arboreal, with the exception of humans, who inhabit every continent except for Antarctica, most primates live in tropical or subtropical regions of the Americas, Africa and Asia. Based on fossil evidence, the earliest known true primates, represented by the genus Teilhardina, an early close primate relative known from abundant remains is the Late Paleocene Plesiadapis, c. Molecular clock studies suggest that the branch may be even older. The order Primates was traditionally divided into two groupings, prosimians and anthropoids. Prosimians have characteristics more like those of the earliest primates, and include the lemurs of Madagascar, lorisoids, simians include monkeys, apes and hominins. Simians are divided into two groups, catarrhine monkeys and apes of Africa and Southeast Asia and platyrrhine or New World monkeys of South, catarrhines consist of Old World monkeys, gibbons and great apes, New World monkeys include the capuchin, howler and squirrel monkeys. Humans are the only extant catarrhines to have spread successfully outside of Africa, South Asia, New primate species are still being discovered. More than 25 species were described in the decade of the 2000s. Considered generalist mammals, primates exhibit a range of characteristics. Some primates are primarily terrestrial rather than arboreal, but all species possess adaptations for climbing trees, locomotion techniques used include leaping from tree to tree, walking on two or four limbs, knuckle-walking, and swinging between branches of trees. Primates are characterized by large brains relative to other mammals, as well as a reliance on stereoscopic vision at the expense of smell. These features are developed in monkeys and apes and noticeably less so in lorises. Three-color vision has developed in some primates, most also have opposable thumbs and some have prehensile tails. Many species are dimorphic, differences include body mass, canine tooth size. Primates have slower rates of development than other similarly sized mammals and reach maturity later, depending on the species, adults may live in solitude, in mated pairs, or in groups of up to hundreds of members. The relationships among the different groups of primates were not clearly understood until relatively recently, for example, ape has been used either as an alternative for monkey or for any tailless, relatively human-like primate
6.
Hominidae
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Several revisions in classifying the great apes have caused the use of the term hominid to vary over time. Its original meaning referred only to humans and their closest non-extant relatives and that restrictive meaning has now been largely assumed by the term hominin, which comprises all members of the human clade after the split from the chimpanzees. The current, 21st-century meaning of hominid includes all the great apes including humans, the most recent common ancestor of all Hominidae lived roughly 14 million years ago, when the ancestors of the orangutans speciated from the ancestral line of the other three genera. Those ancestors of the family Hominidae had already speciated from the family Hylobatidae, in the early Miocene, about 22 million years ago, there were many species of arboreally adapted primitive catarrhines from East Africa, the variety suggests a long history of prior diversification. Fossils at 20 million years ago include fragments attributed to Victoriapithecus, the most recent of these far-flung Miocene apes is Oreopithecus, from the fossil-rich coal beds in northern Italy and dated to 9 million years ago. Species close to the last common ancestor of gorillas, chimpanzees and humans may be represented by Nakalipithecus fossils found in Kenya and Ouranopithecus found in Greece. Molecular evidence suggests that between 8 and 4 million years ago, first the gorillas, and then the split off from the line leading to the humans. Human DNA is approximately 98. 4% identical to that of chimpanzees when comparing single nucleotide polymorphisms, the earliest fossils argued by some to belong to the human lineage are Sahelanthropus tchadensis and Orrorin tugenensis, followed by Ardipithecus, with species Ar. kadabba and Ar. ramidus. The classification of the apes has been revised several times in the last few decades. The original meaning of the referred to only humans and their closest relatives—what is now the modern meaning of the term hominin. And the meaning of the taxon Hominidae changed gradually, leading to a different usage of hominid that today all the great apes including humans. A hominid is a member of the family Hominidae, the apes, orangutans, gorillas, chimpanzees. A hominine is a member of the subfamily Homininae, gorillas, chimpanzees, a hominin is a member of the tribe Hominini, Chimpanzees and humans. A homininan is a member of the subtribe Hominina of the tribe Hominini, a human is a member of the genus Homo, of which Homo sapiens is the only extant species, and within that Homo sapiens sapiens is the only surviving subspecies. For each clade it is indicated approximately when newer extant clades emerged, some texts will refer to Homonini as the Hominina branch. Many scientists, including paleoanthropologists, continue to use the term hominid to mean humans, as mentioned, Hominidae was originally the name given to the family of humans and their close relatives, with the other great apes all being placed in a separate family, the Pongidae. However, that eventually made Pongidae paraphyletic because at least one great ape species proved to be more closely related to humans than to other great apes. Most taxonomists today encourage monophyletic groups—this would require, in this case, thus, many biologists now assign Pongo to the family Hominidae
7.
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
8.
Paleoanthropology
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Hominoids are a primate superfamily, the hominid family is currently considered to comprise both the great ape lineages and human lineages within the hominoid superfamily. The Homininae comprise both the human lineages and the African ape lineages, the term African apes refers only to chimpanzees and gorillas. The terminology of the biological family is currently in flux. The term hominin refers to any genus in the human tribe, since, the great apes were considered the closest relatives of human beings, based on morphological similarity. The science arguably began in the late 19th century when important discoveries occurred that led to the study of human evolution. The discovery of the Neanderthal in Germany, Thomas Huxleys Evidence as to Mans Place in Nature, the modern field of paleoanthropology began in the 19th century with the discovery of Neanderthal man, and with evidence of so-called cave men. Debates between Thomas Huxley and Richard Owen focused on the idea of human evolution, Huxley convincingly illustrated many of the similarities and differences between humans and apes in his 1863 book Evidence as to Mans Place in Nature. By the time Darwin published his own book on the subject, Descent of Man, even many of Darwins original supporters balked at the idea that human beings could have evolved their apparently boundless mental capacities and moral sensibilities through natural selection. Prior to todays general acceptance of Africa as the root of genus Homo, although Schlosser was very cautious, identifying the tooth only as “. Anthropoide g. et sp. indet. ”He was hopeful that future work would discover a new anthropoid in China. Eleven years later, the Swedish geologist Johan Gunnar Andersson was sent to China as a mining advisor and it was he who, in 1918, discovered the sites around Zhoukoudian, a village about 50 kilometers southwest of Beijing. However, because of the nature of the initial finds. Work did not resume until 1921, when the Austrian paleontologist, Otto Zdansky, fresh with his degree from Vienna. Zdansky conducted short-term excavations at Locality 1 in 1921 and 1923, with that done, Zdansky returned to Austria and suspended all fieldwork. News of the fossil hominin teeth delighted the scientific community in Beijing, at the epicenter of excitement was Davidson Black, a Canadian-born anatomist working at Peking Union Medical College. Black shared Andersson’s interest, as well as his view that central Asia was a home for early humankind. The Zhoukoudian Project came into existence in the spring of 1927, being the first institution of its kind, the Cenozoic Laboratory opened up new avenues for the study of paleogeology and paleontology in China. The Laboratory was the precursor of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Science, the first of the major project finds are attributed to the young Swedish paleontologist, Anders Birger Bohlin, then serving as the field advisor at Zhoukoudian. He recovered a left lower molar that Black identified as unmistakably human, the news was at first met with skepticism, and many scholars had reservations that a single tooth was sufficient to justify the naming of a new type of early hominin
9.
Oldowan
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The Oldowan, sometimes spelled Olduwan, is the earliest widespread stone tool archaeological industry in prehistory. Oldowan tools were used during the Lower Paleolithic period,2.6 million years ago up until 1.7 million years ago, by ancient hominids across much of Africa, South Asia and this technological industry was followed by the more sophisticated Acheulean industry. The term Oldowan is taken from the site of Olduvai Gorge in Tanzania, classification of Oldowan tools is still somewhat contentious. Mary Leakey was the first to create a system to classify Oldowan assemblages, the system included choppers, scrapers, and pounders. However, more recent classifications of Oldowan assemblages have been made that focus primarily on manufacture due to the nature of assuming use from stone artefacts. An example is Isaac et al. s tri-modal categories of Flaked Pieces, Detached Pieces, Pounded Pieces, Oldowan tools are sometimes called pebble tools, so named because the blanks chosen for their production already resemble, in pebble form, the final product. It is not known for sure which hominin species actually created and used Oldowan tools and its emergence is often associated with the species Australopithecus garhi and its flourishing with early species of Homo such as H. habilis and H. ergaster. Early Homo erectus appears to inherit Oldowan technology and refines it into the Acheulean industry beginning 1.7 million years ago, the oldest known Oldowan tools have been found in Gona, Ethiopia, and are dated to about 2.6 mya. The use of tools by apes including chimpanzees and orangutans can be used to argue in favour of tool-use as a feature of the hominin family. Tools made from bone, wood, or other materials were therefore in all probability used before the Oldowan. Oldowan stone tools are simply the oldest recognisable tools which have preserved in the archaeological record. There is a flourishing of Oldowan tools in eastern Africa, spreading to southern Africa, at 1.7 mya. the first Acheulean tools appear even as Oldowan assemblages continue to be produced. Both technologies are found in the same areas, dating to the same time periods. This realisation required a rethinking of old cultural sequences in which the more advanced Acheulean was supposed to have succeeded the Oldowan. Sometime before 1.8 mya Homo erectus had spread outside of Africa, reaching as far east as Java by 1.8 mya, in these newly colonised areas, no Acheulean assemblages have been found. In China, only Mode 1 Oldowan assemblages were produced, while in Indonesia stone tools from this age are unknown, by 1.8 mya early Homo was present in Europe, as shown by the discovery of fossil remains and Oldowan tools in Dmanisi, Georgia. Remains of their activities have also excavated in Spain at sites in the Guadix-Baza basin. Most early European sites yield Mode 1 or Oldowan assemblages, the earliest Acheulean sites in Europe only appear around 0.5 mya
10.
Acheulean
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Acheulean, from the French acheuléen, is an archaeological industry of stone tool manufacture characterized by distinctive oval and pear-shaped hand-axes associated with early humans. Acheulean tools were produced during the Lower Palaeolithic era across Africa and much of West Asia, South Asia, and Europe, and are typically found with Homo erectus remains. It is thought that Acheulean technologies first developed in Africa out of the more primitive Oldowan technology as long ago as 1.76 million years ago, Acheulean tools were the dominant technology for the vast majority of human history. The type site for the Acheulean is Saint-Acheul, a suburb of Amiens, the capital of the Somme department in Picardy, john Frere is generally credited as being the first to suggest a very ancient date for Acheulean hand-axes. In 1797, he sent two examples to the Royal Academy in London from Hoxne in Suffolk and his ideas were, however, ignored by his contemporaries, who subscribed to a pre-Darwinian view of human evolution. Following visits to both Abbeville and Saint Acheul by the geologist Joseph Prestwich, the age of the tools was finally accepted, in 1872, Louis Laurent Gabriel de Mortillet described the characteristic hand-axe tools as belonging to LEpoque de St Acheul. The industry was renamed as the Acheulean in 1925, from the Konso Formation of Ethiopia, Acheulean hand-axes are dated to about 1.5 million years ago using radiometric dating of deposits containing volcanic ashes. Acheulean tools in South Asia have also found to be dated as far as 1.5 million years ago. However, the earliest accepted examples of the Acheulean currently known come from the West Turkana region of Kenya and were first described by a French-led archaeology team. These particular Acheulean tools were dated through the method of magnetostratigraphy to about 1.76 million years ago, making them the oldest not only in Africa. The earliest user of Acheulean tools was Homo ergaster, who first appeared about 1.8 million years ago, not all researchers use this formal name, and instead prefer to call these users early Homo erectus. In individual regions, this dating can be refined, in Europe for example. However more recent research demonstrated that hand-axes from Spain were made more than 900,000 years ago, the enormous geographic spread of Acheulean techniques also makes the name unwieldy as it represents numerous regional variations on a similar theme. The term Acheulean does not represent a culture in the modern sense. The very earliest Acheulean assemblages often contain numerous Oldowan-style flakes and core forms and these industries are known as the Developed Oldowan and are almost certainly transitional between the Oldowan and Acheulean. The Mode 1 industries created rough flake tools by hitting a stone with a hammerstone. The resulting flake that broke off would have a sharp edge for cutting. These early toolmakers may also have worked the stone they took the flake from to create chopper cores although there is debate over whether these items were tools or just discarded cores
11.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
12.
Unicellular organism
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A unicellular organism, also known as a single-celled organism, is an organism that consists of only one cell, unlike a multicellular organism that consists of more than one cell. Historically, simple unicellular organisms have been referred to as monads, though this term is used more specifically to describe organisms of the genus Monas. The main groups of organisms are bacteria, archaea, protozoa, unicellular algae. Unicellular organisms fall into two categories, prokaryotic organisms and eukaryotic organisms. Unicellular organisms are thought to be the oldest form of life, prokaryotes, most Protista, and some fungi are unicellular. Although some of these live in colonies, they dont exhibit specialization. These organisms live together, and each cell in the colony is the same, however, each individual cell must carry out all life processes to survive. In contrast, even the simplest multicellular organisms have cells that depend on each other to survive, most multicellular organisms have a unicellular life-cycle stage. Gametes, for example, are reproductive unicells for multicellular organisms, additionally, multicellularity appears to have evolved independently many times in the history of life. Some organisms are partially uni- and multicellular, like Dictyostelium discoideum, additionally, unicellular organisms can be multinucleate, like Myxogastria and Plasmodium. Candidatus Magnetoglobus multicellular, related to Deltaproteobacteria, is a multicellular prokaryote and it is neither unicellular, nor a colony. Primitive cells, often referred to as protocells, are the precursors to todays unicellular organisms, the RNA world hypothesis assumes that RNA molecules could form in abiotic conditions, which would require nucleic acids and ribose to be present. Theoretical and experimental findings show that nucleic acids and sugars could have been synthesized in early prebiotic conditions, compartmentalization was necessary for chemical reactions to be more likely as well as to differentiate reactions with the external environment. For example, an early RNA replicator ribozyme may have replicated other replicator ribozymes of different RNA sequences if not kept separate, when amphiphiles like lipids are placed in water, the hydrophobic tails aggregate to form micelles and vesicles, with the hydrophilic ends facing outwards. Primitive cells likely used self-assembling fatty-acid vesicles to separate chemical reactions, because of their simplicity and ability to self-assemble in water, its likely that these simple membranes predated other forms of early biological molecules. Prokaryotes lack membrane-bound organelles, such as mitochondria or a nucleus, instead, most prokaryotes have an irregular region that contains DNA, known as the nucleoid. Most prokaryotes have a single, circular chromosome, which is in contrast to eukaryotes, nutritionally, prokaryotes have the ability to utilize a wide range of organic and inorganic material for use in metabolism, including sulfur, cellulose, ammonia, or nitrite. Prokaryotes as a whole are ubiquitous in the environment and exist in extreme environments as well, bacteria are one of the world’s oldest forms of life, and are found virtually everywhere in nature
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