115-624: Sea Life is a chain of commercial sea life -themed aquarium attractions . As of April 2017 there are 53 Sea Life attractions (including standalone Sea Life centres, mini Sea Life features within resort theme parks, and Legoland submarine rides) around the world. The chain is owned by the British company Merlin Entertainments . Some of the aquariums now called Sea Life predate this rebrand and existed under different designations prior to their consolidation. The original named attraction
230-653: A disaster fauna , a group of survivor animals with low diversity and cosmopolitanism (wide geographic ranges). Temnospondyli recovered first and evolved into large aquatic predators during the Triassic. Other reptiles also diversified rapidly, with aquatic reptiles such as ichthyosaurs and sauropterygians proliferating in the seas. On land, the first true archosaurs appeared, including pseudosuchians (crocodile relatives) and avemetatarsalians (bird/dinosaur relatives). The Middle Triassic spans from 247 million to 237 million years ago. The Middle Triassic featured
345-476: A domain and kingdom of single-celled microorganisms . These microbes are prokaryotes , meaning they have no cell nucleus or any other membrane-bound organelles in their cells. Archaea were initially classified as bacteria , but this classification is outdated. Archaeal cells have unique properties separating them from the other two domains of life, Bacteria and Eukaryota . The Archaea are further divided into multiple recognized phyla . Classification
460-475: A negative feedback that arises from resource limitation, or both. The hyperbolic model implies a second-order positive feedback. The hyperbolic pattern of the human population growth arises from quadratic positive feedback, caused by the interaction of the population size and the rate of technological growth. The character of biodiversity growth in the Phanerozoic Eon can be similarly accounted for by
575-541: A body mass over 10 kilograms became extinct, and the Age of Dinosaurs came to an end. The Cenozoic featured the rise of mammals and birds as the dominant class of animals, as the end of the Age of Dinosaurs left significant open niches . There are three divisions of the Cenozoic: Paleogene, Neogene and Quaternary. The Paleogene spans from the extinction of the non-avian dinosaurs, some 66 million years ago, to
690-507: A cooling trend that would continue into the Cenozoic Era. Eventually, the tropical climate was restricted to the equator and areas beyond the tropic lines featured more seasonal climates. Dinosaurs still thrived as new species such as Tyrannosaurus , Ankylosaurus , Triceratops and hadrosaurs dominated the food web. Whether or not pterosaurs went into a decline as birds radiated is debated; however, many families survived until
805-476: A cooperative association called endosymbiosis . The engulfed bacteria and the host cell then underwent coevolution, with the bacteria evolving into either mitochondria or hydrogenosomes . Another engulfment of cyanobacterial -like organisms led to the formation of chloroplasts in algae and plants. The history of life was that of the unicellular eukaryotes, prokaryotes and archaea until about 610 million years ago when multicellular organisms began to appear in
920-476: A feedback between the diversity and community structure complexity. It has been suggested that the similarity between the curves of biodiversity and human population probably comes from the fact that both are derived from the superposition on the hyperbolic trend of cyclical and random dynamics. Across the Phanerozoic, the dominant driver of long-term climatic change was the concentration of carbon dioxide in
1035-510: A form of life or organic structures that interact with living organisms. They are considered by some to be a life form, because they carry genetic material, reproduce by creating multiple copies of themselves through self-assembly, and evolve through natural selection . However they lack key characteristics such as a cellular structure generally considered necessary to count as life. Because they possess some but not all such qualities, viruses have been described as replicators and as "organisms at
1150-668: A fundamental level, marine life affects the nature of the planet, and in part, shape and protect shorelines, and some marine organisms (e.g. corals ) even help create new land via accumulated reef -building. Marine life can be roughly grouped into autotrophs and heterotrophs according to their roles within the food web : the former include photosynthetic and the much rarer chemosynthetic organisms ( chemoautotrophs ) that can convert inorganic molecules into organic compounds using energy from sunlight or exothermic oxidation , such as cyanobacteria, iron-oxidizing bacteria , algae ( seaweeds and various microalgae ) and seagrass ;
1265-438: A hierarchy of nested groups—similar to a family tree. However, modern research has suggested that, due to horizontal gene transfer , this "tree of life" may be more complicated than a simple branching tree since some genes have spread independently between distantly related species. Past species have also left records of their evolutionary history. Fossils, along with the comparative anatomy of present-day organisms, constitute
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#17327657413821380-594: A lesser extent shelled cephalopods (such as orthocones ). Almost all phyla of marine animals evolved in this period. During this time, the super-continent Pannotia began to break up, most of which later recombined into the super-continent Gondwana . The Ordovician spans from 485 million to 444 million years ago. The Ordovician was a time in Earth's history in which many groups still prevalent today evolved or diversified, such as primitive nautiloids , vertebrates (then only jawless fish ) and corals . This process
1495-426: A result, the world was warm and partially tropical, though possibly with short colder intervals. Plesiosaurs , ichthyosaurs and ammonites dominated the seas, while dinosaurs, pterysaurs and other reptiles dominated the land, with species such as Dilophosaurus at the apex. Crocodylomorphs evolved into aquatic forms, pushing the remaining large amphibians to near extinction. True mammals were present during
1610-1029: A severe extinction of sauropods in northern continents, alongside many ichthyosaurs. However, the Jurassic-Cretaceous boundary did not strongly impact most forms of life. The Cretaceous is the Phanerozoic's longest period and the last period of the Mesozoic. It spans from 145 million to 66 million years ago, and is divided into two epochs: Early Cretaceous , and Late Cretaceous . The Early Cretaceous Epoch spans from 145 million to 100 million years ago. Dinosaurs continued to be abundant, with groups such as tyrannosauroids , avialans ( birds ), marginocephalians , and ornithopods seeing early glimpses of later success. Other tetrapods, such as stegosaurs and ichthyosaurs, declined significantly, and sauropods were restricted to southern continents. The Late Cretaceous Epoch spans from 100 million to 66 million years ago. The Late Cretaceous featured
1725-532: A supervolcano eruption in Sumatra 74,000 years ago caused a global population bottleneck of humans, a second wave of Homo sapiens migration successfully repopulated every continents except Antarctica. As the Pleistocene drew to a close, a major extinction wiped out much of the world's megafauna , including non- Homo sapiens human species such as Homo neanderthalensis and Homo floresiensis . All
1840-490: A trend of desiccation which resulted in the creation of the Sahara, Namib and Kalahari deserts. Mammoths , giant ground sloths , dire wolves , sabre-toothed cats and archaic humans such as Homo erectus were common and widespread during the Pleistocene. A more anatomically modern human , Homo sapiens , began migrating out of East Africa in at least two waves, the first being as early as 270,000 years ago. After
1955-429: Is a period in which grass spread further across, effectively dominating a large portion of the world, diminishing forests in the process. Kelp forests evolved, leading to the evolution of new species such as sea otters . During this time, perissodactyls thrived, and evolved into many different varieties. Alongside them were the apes , which evolved into 30 species. Overall, arid and mountainous land dominated most of
2070-616: Is a unique feature in the Solar System . Earth's hydrosphere consists chiefly of the oceans but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,000 metres (6,600 ft). The deepest underwater location is Challenger Deep of the Mariana Trench in the Pacific Ocean , having a depth of 10,900 metres (6.8 mi). Conventionally,
2185-600: Is because it was once believed that life began in the Cambrian , the first period of this eon, due to the lack of Precambrian fossil record back then. However, trace fossils of booming complex life from the Ediacaran period ( Avalon explosion ) of the preceding Proterozoic eon have since been discovered, and the modern scientific consensus now agrees that complex life (in the form of placozoans and primitive sponges such as Otavia ) has existed at least since
2300-538: Is debated. The Oligocene Epoch spans from 34 million to 23 million years ago. The Oligocene was an important transitional period between the tropical world of the Eocene and more modern ecosystems. This period featured a global expansion of grass which led to many new species taking advantage, including the first elephants , felines , canines , marsupials and many other species still prevalent today. Many other species of plants evolved during this epoch also, such as
2415-529: Is difficult because the majority have not been isolated in the laboratory and have only been detected by analysis of their nucleic acids in samples from their environment. Archaea and bacteria are generally similar in size and shape, although a few archaea have very strange shapes, such as the flat and square-shaped cells of Haloquadratum walsbyi . Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably
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#17327657413822530-447: Is diverse and still poorly understood, such as for the role of viruses in marine ecosystems. Most marine viruses are bacteriophages , which are harmless to plants and animals, but are essential to the regulation of saltwater and freshwater ecosystems. They infect and destroy bacteria in aquatic microbial communities, and are the most important mechanism of recycling carbon in the marine environment. The organic molecules released from
2645-540: Is found elsewhere in the Solar System. Europa , one of the moons orbiting Jupiter , is slightly smaller than the Earth's Moon . There is a strong possibility a large saltwater ocean exists beneath its ice surface. It has been estimated the outer crust of solid ice is about 10–30 km (6–19 mi) thick and the liquid ocean underneath is about 100 km (60 mi) deep. This would make Europa's ocean over twice
2760-509: Is known as the Great Ordovician Biodiversification Event or GOBE. Trilobites began to be replaced by articulate brachiopods , and crinoids also became an increasingly important part of the fauna. The first arthropods crept ashore to colonise Gondwana , a continent empty of animal life. A group of freshwater green algae , the streptophytes , also survived being washed ashore and began to colonize
2875-550: Is mostly a transitional recovery period between the desolate aftermath of the Permian Extinction and the lush Jurassic Period. It has three major epochs: Early Triassic , Middle Triassic , and Late Triassic . The Early Triassic lasted between 252 million to 247 million years ago, and was a hot and arid epoch in the aftermath of the Permian Extinction. Many tetrapods during this epoch represented
2990-439: Is no life without water. It has been described as the universal solvent for its ability to dissolve many substances, and as the solvent of life . Water is the only common substance to exist as a solid , liquid, and gas under conditions normal to life on Earth. The Nobel Prize winner Albert Szent-Györgyi referred to water as the mater und matrix : the mother and womb of life. The abundance of surface water on Earth
3105-399: Is that the complex biochemistry that makes up life came from simpler chemical reactions. The beginning of life may have included self-replicating molecules such as RNA and the assembly of simple cells. In 2016 scientists reported a set of 355 genes from the last universal common ancestor (LUCA) of all life , including microorganisms, living on Earth . Current species are a stage in
3220-509: Is the first period of the Paleozoic Era and ran from 539 million to 485 million years ago. The Cambrian sparked a rapid expansion in the diversity of animals, in an event known as the Cambrian explosion , during which the greatest number of animal body plans evolved in a single period in the history of Earth. Complex algae evolved, and the fauna was dominated by armoured arthropods (such as trilobites and radiodontids ) and to
3335-605: The Avalon Explosion . This was followed in the early Phanerozoic by a more prominent radiation event known as the Cambrian Explosion , where actively moving eumetazoan became prevalent. These marine life also expanded into fresh waters , where fungi and green algae that were washed ashore onto riparian areas started to take hold later during the Ordivician before rapidly expanding inland during
3450-743: The Eoarchean era after a geological crust started to solidify following the earlier molten Hadean Eon. Microbial mat fossils have been found in 3.48 billion-year-old sandstone in Western Australia . Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland as well as "remains of biotic life " found in 4.1 billion-year-old rocks in Western Australia. According to one of
3565-476: The Mariana Trench , the deepest spot in the Earth's oceans. Microorganisms live inside rocks 580 m (1,900 ft) below the sea floor under 2,590 m (8,500 ft) of ocean off the coast of the northwestern United States, as well as 2,400 m (7,900 ft; 1.5 mi) beneath the seabed off Japan. The greatest known temperature at which microbial life can exist is 122 °C (252 °F) ( Methanopyrus kandleri ). In 2014, scientists confirmed
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3680-569: The Marine Conservation Society calling a 30% per annum mortality rate "disturbing." The charity Freedom for Animals has criticised Sea Life over their conservation claims and also for the presence of Beluga whales at attractions. Marine life Marine life , sea life or ocean life is the collective ecological communities that encompass all aquatic animals , plants , algae , fungi , protists , single-celled microorganisms and associated viruses living in
3795-520: The Messinian salinity crisis . Along with these major geological events, Africa saw the appearance of Australopithecus , the ancestor of Homo . The Isthmus of Panama formed, and animals migrated between North and South America, wreaking havoc on the local ecology. Climatic changes brought savannas that are still continuing to spread across the world, Indian monsoons , deserts in East Asia, and
3910-632: The Ordovician–Silurian extinction , during which 60% of marine invertebrates and 25% of families became extinct. Though one of the deadliest mass extinctions in earth's history, the O–S extinction did not cause profound ecological changes between the periods. The Silurian spans from 444 million to 419 million years ago, which saw a warming from an icehouse Earth. This period saw the mass diversification of fish , as jawless fish became more numerous, and early jawed fish and freshwater species appeared in
4025-461: The Silurian and Devonian , paving the way for terrestrial ecosystems to develop. Today, marine species range in size from the microscopic phytoplankton , which can be as small as 0.02– micrometres ; to huge cetaceans like the blue whale , which can reach 33 m (108 ft) in length. Marine microorganisms have been variously estimated as constituting about 70% or about 90% of
4140-812: The Tethys Sea , and the Americas were separated by the Panamanic Seaway (as the Isthmus of Panama had not yet formed). This epoch featured a general warming trend that peaked at the Paleocene-Eocene Thermal Maximum , and the earliest modern jungles expanded, eventually reaching the poles. The oceans were dominated by sharks, as the large reptiles that had once ruled had become extinct. Mammals diversified rapidly, but most remained small. The largest tetrapod carnivores during
4255-511: The Tonian period and the earliest known life forms (in the form of simple prokaryotic microbial mats ) started in the ocean floor during the earlier Archean eon. The Proterozoic –Phanerozoic boundary is at 538.8 million years ago. In the 19th century, the boundary was set at time of appearance of the first abundant animal ( metazoan ) fossils , but trace fossils of several hundred groups ( taxa ) of complex soft-bodied metazoa from
4370-801: The enzymes involved in transcription and translation . Other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes , such as archaeols . Archaea use more energy sources than eukaryotes: these range from organic compounds , such as sugars, to ammonia , metal ions or even hydrogen gas . Salt-tolerant archaea (the Haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon ; however, unlike plants and cyanobacteria , no known species of archaea does both. Archaea reproduce asexually by binary fission , fragmentation , or budding ; unlike bacteria and eukaryotes, no known species forms spores . Archaea are particularly numerous in
4485-597: The flood plains and riparian zones , giving rise to primitive land plants . By the end of the Ordovician, Gondwana had moved from the equator to the South Pole , and Laurentia had collided with Baltica , closing the Iapetus Ocean . The glaciation of Gondwana resulted in a major drop in sea level, killing off all life that had established along its coast. Glaciation caused an icehouse Earth , leading to
4600-748: The marine biomass . A microorganism , or microbe, is a microscopic organism too small to be recognised with the naked eye. It can be single-celled or multicellular . Microorganisms are diverse and include all bacteria and archaea , most protozoa such as algae , fungi , and certain microscopic animals such as rotifers . Many macroscopic animals and plants have microscopic juvenile stages . Some microbiologists also classify viruses (and viroids ) as microorganisms, but others consider these as nonliving. Microorganisms are crucial to nutrient recycling in ecosystems as they act as decomposers . Some microorganisms are pathogenic , causing disease and even death in plants and animals. As inhabitants of
4715-524: The saline water of marine habitats , either the sea water of marginal seas and oceans , or the brackish water of coastal wetlands , lagoons , estuaries and inland seas . As of 2023 , more than 242,000 marine species have been documented, and perhaps two million marine species are yet to be documented. An average of 2,332 new species per year are being described. Marine life is studied scientifically in both marine biology and in biological oceanography . By volume, oceans provide about 90% of
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4830-496: The scientific classification changed after the discovery in the 1990s that prokaryotes consist of two very different groups of organisms that evolved from an ancient common ancestor. These evolutionary domains are called Bacteria and Archaea . The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, and bacteria and archaea were
4945-474: The thermophilic archaea, particularly the orders Sulfolobales and Thermoproteales . Viruses are an important natural means of transferring genes between different species, which increases genetic diversity and drives evolution. It is thought that viruses played a central role in the early evolution, before the diversification of bacteria, archaea and eukaryotes, at the time of the last universal common ancestor of life on Earth. Viruses are still one of
5060-512: The "Age of the Fish", the Devonian features a huge diversification in fish such as the jawless conodonts and ostracoderms , as well as jawed fish such as the armored placoderms (e.g. Dunkleosteus ), the spiny acanthodians and early bony fish . The Devonian also saw the primitive appearance of modern fish groups such as chondricthyans ( cartilaginous fish ) and osteichthyans (bony fish),
5175-472: The Age of Reptiles, Age of Dinosaurs or Age of Conifers, the Mesozoic featured the first time the sauropsids ascended to ecological dominance over the synapsids, as well as the diversification of many modern ray-finned fish , insects , molluscs (particularly the coleoids ), tetrapods and plants. The Mesozoic is subdivided into three periods: the Triassic, Jurassic and Cretaceous. The Triassic ranges from 252 million to 201 million years ago. The Triassic
5290-500: The Carboniferous as semiaquatic amphibians such as the temnospondyls , and one lineage developed extraembryonic membranes that allowed their eggs to survive outside of the water. These tetrapods, the amniotes , included the first sauropsids (which evolved the reptiles , dinosaurs and birds ) and synapsids (the ancestors of mammal ). Throughout the Carboniferous, there was a cooling pattern, which eventually led to
5405-617: The DNA or RNA of viruses and are a useful means of investigating how they arise. Viruses are now recognised as ancient and as having origins that pre-date the divergence of life into the three domains . But the origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids —pieces of DNA that can move between cells—while others may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer , which increases genetic diversity . Opinions differ on whether viruses are
5520-514: The Earth, and the large amounts of trees sequestered much of the carbon that became coal deposits (hence the name Carboniferous and the term " coal forest "). About 90% of all coal beds were deposited in the Carboniferous and Permian periods, which represent just 2% of the Earth's geologic history. The high oxygen levels caused by these wetland rainforests allowed arthropods, normally limited in size by their respiratory systems , to proliferate and increase in size. Tetrapods also diversified during
5635-599: The Jurassic but remained small, with average body masses of less than 10 kilograms (22 lb) until the end of the Cretaceous. The Middle and Late Jurassic Epochs span from 174 million to 145 million years ago. Conifer savannahs made up a large portion of the world's forests. In the oceans, plesiosaurs were quite common, and ichthyosaurs were flourishing. The Late Jurassic Epoch spans from 163 million to 145 million years ago. The Late Jurassic featured
5750-544: The Late Triassic, and pterosaurs evolved a bit later. Other large reptilian competitors to the dinosaurs were wiped out by the Triassic–Jurassic extinction event , in which most archosaurs (excluding crocodylomorphs , pterosaurs and dinosaurs), most therapsids (except cynodonts ) and almost all large amphibians became extinct, as well as 34% of marine life in the fourth mass extinction event. The cause of
5865-600: The Middle Devonian, shrub-like forests existed: lycophytes , horsetails and progymnosperm . This greening event also allowed the diversification of arthropods as they took advantage of the new habitat. Near the end of the Devonian, 70% of all species became extinct in a sequence of mass extinction events, collectively known as the Late Devonian extinction . The Carboniferous spans from 359 million to 299 million years ago. Tropical swamps dominated
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#17327657413825980-584: The Paleocene were reptiles, including crocodyliforms , choristoderans and snakes . Titanoboa , the largest known snake, lived in South America during the Paleocene. The Eocene Epoch ranged from 56 million to 34 million years ago. In the early Eocene, most land mammals were small and living in cramped jungles, much like the Paleocene. Among them were early primates , whales and horses along with many other early forms of mammals. The climate
6095-401: The Phanerozoic correlate much better with the hyperbolic model (widely used in demography and macrosociology ) than with exponential and logistic models (traditionally used in population biology and extensively applied to fossil biodiversity as well). The latter models imply that changes in diversity are guided by a first-order positive feedback (more ancestors, more descendants) or
6210-463: The Phanerozoic starts with the sudden appearance of fossilised evidence of a number of animal phyla ; the evolution of those phyla into diverse forms; the evolution of plants ; the evolution of fish , arthropods and molluscs ; the terrestrial colonization and evolution of insects , chelicerates , myriapods and tetrapods ; and the development of modern flora dominated by vascular plants . During this time span, tectonic forces which move
6325-540: The accumulation of oxygen in the atmosphere from photosynthesis. About 500 million years ago, plants and fungi started colonising the land. Evidence for the appearance of the first land plants occurs in the Ordovician , around 450 million years ago , in the form of fossil spores. Land plants began to diversify in the Late Silurian , from around 430 million years ago . The colonisation of
6440-812: The ancestors of modern mammals. The first conifers evolved during this period, then dominated the terrestrial landscape. The Permian ended with at least one mass extinction , an event sometimes known as " the Great Dying ", caused by large floods of lava (the Siberian Traps in Russia and the Emeishan Traps in China). This extinction was the largest in Earth's history and led to the loss of 95% of all species of life. The Mesozoic ranges from 252 million to 66 million years ago. Also referred to as
6555-699: The archaeal/eukaryotic lineage. Bacteria were also involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea . This involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes , which are still found in all known Eukarya. Later on, some eukaryotes that already contained mitochondria also engulfed cyanobacterial-like organisms. This led to
6670-458: The atmosphere, though some studies have suggested a decoupling of carbon dioxide and palaeotemperature, particularly during cold intervals of the Phanerozoic. Phanerozoic carbon dioxide concentrations have been governed partially by a 26 million year oceanic crustal cycle. Since the Devonian, large swings in carbon dioxide of 2,000 ppm or more were uncommon over short timescales. Variations in global temperature were limited by negative feedbacks in
6785-402: The average virus is about one one-hundredth that of the average bacterium . Most viruses cannot be seen with an optical microscope so electron microscopes are used instead. Viruses are found wherever there is life and have probably existed since living cells first evolved. The origin of viruses is unclear because they do not form fossils, so molecular techniques have been used to compare
6900-697: The beginnings of the Sahara Desert . The Earth's continents and seas moved into their present shapes. The world map has not changed much since, save for changes brought about by the Quaternary glaciation such as Lake Agassiz (precursor of the Great Lakes ). The Quaternary spans from 2.58 million years ago to present day, and is the shortest geological period in the Phanerozoic Eon . It features modern animals, and dramatic changes in
7015-887: The beginnings of the break-up of Pangaea as rifting commenced in north Pangaea. The northern part of the Tethys Ocean , the Paleotethys Ocean, had become a passive basin, but a spreading center was active in the southern part of the Tethys Ocean, the Neotethys Ocean. Phytoplankton , coral, crustaceans and many other marine invertebrates recovered from the Permian extinction by the end of the Middle Triassic. Meanwhile, on land, reptiles continued to diversify, conifer forests flourished, as well as
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#17327657413827130-627: The boundaries of the Holocene epoch. Human activity is blamed for an ongoing mass extinction that began roughly 10,000 years ago, though the species becoming extinct have only been recorded since the Industrial Revolution . This is sometimes referred to as the " Sixth Extinction " with hundreds of species gone extinct due to human activities such as overhunting , habitat destruction and introduction of invasive species . It has been demonstrated that changes in biodiversity through
7245-564: The climate. It is divided into two epochs: the Pleistocene and the Holocene . The Pleistocene lasted from 2.58 million to 11,700 years ago. This epoch was marked by a series of glacial periods ( ice ages ) as a result of the cooling trend that started in the mid-Eocene. There were numerous separate glaciation periods marked by the advance of ice caps as far south as 40 degrees N latitude in mountainous areas. Meanwhile, Africa experienced
7360-533: The continents had collected them into a single landmass known as Pangaea (the most recent supercontinent ), which then separated into the current continental landmasses. The term "Phanerozoic" was coined in 1930 by the American geologist George Halcott Chadwick (1876–1953), deriving from the Ancient Greek words φανερός ( phanerós ), meaning "visible"; and ζωή ( zōḗ ), meaning "life". This
7475-416: The continents were affected, but Africa was impacted to a lesser extent and retained many large animals such as elephants, rhinoceros and hippopotamus . The extent to which Homo sapiens were involved in this megafaunal extinction is debated. The Holocene began 11,700 years ago at the end of Younger Dryas and lasts until the present day. All recorded history and so-called " human history " lies within
7590-406: The cooling climate even as more archaic forms died out. By the end of the Eocene, whales such as Basilosaurus had become fully aquatic. The late Eocene Epoch saw the rebirth of seasons, which caused the expansion of savanna-like areas with the earliest substantial grasslands . At the transition between the Eocene and Oligocene epochs there was a significant extinction event , the cause of which
7705-519: The dawn of the Neogene 23 million years ago. It features three epochs : Paleocene , Eocene and Oligocene . The Paleocene Epoch began with the K–Pg extinction event, and the early part of the Paleocene saw the recovery of the Earth from that event. The continents began to take their modern shapes, but most continents (and India) remained separated from each other: Africa and Eurasia were separated by
7820-594: The dead bacterial cells stimulate fresh bacterial and algal growth. Viral activity may also contribute to the biological pump , the process whereby carbon is sequestered in the deep ocean. A stream of airborne microorganisms circles the planet above weather systems but below commercial air lanes. Some peripatetic microorganisms are swept up from terrestrial dust storms, but most originate from marine microorganisms in sea spray . In 2018, scientists reported that hundreds of millions of viruses and tens of millions of bacteria are deposited daily on every square meter around
7935-450: The deep portions of Earth's crust . Bacteria also live in symbiotic and parasitic relationships with plants and animals. Once regarded as plants constituting the class Schizomycetes , bacteria are now classified as prokaryotes . Unlike cells of animals and other eukaryotes , bacterial cells do not contain a nucleus and rarely harbour membrane-bound organelles . Although the term bacteria traditionally included all prokaryotes,
8050-410: The dominant forms of life. Although bacterial fossils exist, such as stromatolites , their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species. However, gene sequences can be used to reconstruct the bacterial phylogeny , and these studies indicate that bacteria diverged first from
8165-498: The early Proterozoic significantly altered the marine chemistry , which likely caused a widespread anaerobe extinction event but also led to the evolution of eukaryotes through symbiogenesis between surviving anaerobes and aerobes . Complex life eventually arose out of marine eukaryotes during the Neoproterozoic , and which culminated in a large evolutionary radiation event of mostly sessile macrofaunae known as
8280-399: The edge of life". Bacteriophages , often just called phages , are viruses that parasite bacteria and archaea. Marine phages parasite marine bacteria and archaea, such as cyanobacteria . They are a common and diverse group of viruses and are the most abundant biological entity in marine environments, because their hosts, bacteria, are typically the numerically dominant cellular life in
8395-461: The emergence of these first multicellular organisms, a remarkable amount of biological diversity appeared over a span of about 10 million years, in an event called the Cambrian explosion . Here, the majority of types of modern animals appeared in the fossil record, as well as unique lineages that subsequently became extinct. Various triggers for the Cambrian explosion have been proposed, including
8510-428: The end of the Cretaceous, alongside new forms such as the gigantic Quetzalcoatlus . Mammals diversified despite their small sizes, with metatherians ( marsupials and kin) and eutherians ( placentals and kin) coming into their own. In the oceans, mosasaurs diversified to fill the role of the now-extinct ichthyosaurs, alongside huge plesiosaurs such as Elasmosaurus . Also, the first flowering plants evolved. At
8625-600: The end of the Cretaceous, the Deccan Traps and other volcanic eruptions were poisoning the atmosphere. As this was continued, it is thought that a large meteor smashed into Earth, creating the Chicxulub Crater and causing the event known as the K–Pg extinction , the fifth and most recent mass extinction event, during which 75% of life on Earth became extinct, including all non-avian dinosaurs. Every living thing with
8740-584: The evergreen trees. The long term cooling continued and seasonal rain patterns established. Mammals continued to grow larger. Paraceratherium , one of the largest land mammals to ever live, evolved during this epoch, along with many other perissodactyls . The Neogene spans from 23.03 million to 2.58 million years ago. It features two epochs: the Miocene and the Pliocene . The Miocene spans from 23.03 million to 5.333 million years ago and
8855-486: The evolution of the three most prominent animal phyla, arthropods , molluscs and chordates , the last of which includes fish , amphibians and the fully terrestrial amniotes ( synapsids and sauropsids ). The Mesozoic features the evolution of crocodilians , turtles , dinosaurs (including birds ), lepidosaurs ( lizards and snakes ) and mammals . The Cenozoic begins with the extinction of all non-avian dinosaurs , pterosaurs and marine reptiles , and features
8970-463: The evolution of these large animals, smaller organisms similar to the types that evolved early in this process continue to be highly successful and dominate the Earth, with the majority of both biomass and species being prokaryotes. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. Microorganisms make up about 70% of
9085-546: The existence of microorganisms living 800 m (2,600 ft) below the ice of Antarctica . According to one researcher, "You can find microbes everywhere — they're extremely adaptable to conditions, and survive wherever they are." Viruses are small infectious agents that do not have their own metabolism and can replicate only inside the living cells of other organisms . Viruses can infect all types of life forms , from animals and plants to microorganisms , including bacteria and archaea . The linear size of
9200-460: The extinction is debated, but likely resulted from eruptions of the CAMP large igneous province . The Jurassic ranges from 201 million to 145 million years ago, and features three major epochs: Early Jurassic , Middle Jurassic and Late Jurassic . The Early Jurassic epoch spans from 201 million to 174 million years ago. The climate was much more humid than during the Triassic, and as
9315-468: The few areas where they differ helps shed light on when the common ancestor of these species existed. Prokaryotes inhabited the Earth from approximately 3–4 billion years ago. No obvious changes in morphology or cellular organisation occurred in these organisms over the next few billion years. The eukaryotic cells emerged between 1.6 and 2.7 billion years ago. The next major change in cell structure came when bacteria were engulfed by eukaryotic cells, in
9430-550: The first flies. The Late Triassic spans from 237 million to 201 million years ago. Following the bloom of the Middle Triassic, the Late Triassic was initially warm and arid with a strong monsoon climate and with most precipitation limited to coastal regions and high latitudes. This changed late in the Carnian period with a 2 million years-long wet season which transformed the arid continental interior into lush alluvial forests . The first true dinosaurs appeared early in
9545-481: The formation of chloroplasts in algae and plants. There are also some algae that originated from even later endosymbiotic events. Here, eukaryotes engulfed a eukaryotic algae that developed into a "second-generation" plastid. This is known as secondary endosymbiosis . The largest known bacterium, the marine Thiomargarita namibiensis , can be visible to the naked eye and sometimes attains 0.75 mm (750 μm). The archaea (Greek for ancient ) constitute
9660-718: The fossil record. Arthropods remained abundant, and some groups, such as eurypterids , became apex predators in the ocean. Fully terrestrial life established itself on land, including early fungi , arachnids , hexapods and myriapods . The evolution of vascular plants (mainly spore -producing ferns such as Cooksonia ) allowed land plants to gain a foothold further inland as well. During this time, there were four continents: Gondwana (Africa, South America, Australia, Antarctica, India), Laurentia (North America with parts of Europe), Baltica (the rest of Europe), and Siberia (Northern Asia). The Devonian spans from 419 million to 359 million years ago. Also informally known as
9775-609: The glaciation of Gondwana as much of it was situated around the South Pole . This event was known as the Permo-Carboniferous Glaciation and resulted in a major loss of coal forests, known as the Carboniferous rainforest collapse . The Permian spans from 299 million to 251 million years ago and was the last period of the Paleozoic era. At its beginning, all landmasses came together to form
9890-523: The great diversification in birds and mammals. Humans appeared and evolved during the most recent part of the Cenozoic. The Paleozoic is a time in Earth's history when active complex life forms evolved, took their first foothold on dry land, and when the forerunners of all multicellular life on Earth began to diversify. There are six periods in the Paleozoic era: Cambrian , Ordovician , Silurian , Devonian , Carboniferous and Permian . The Cambrian
10005-480: The land by plants was soon followed by arthropods and other animals. Insects were particularly successful and even today make up the majority of animal species. Amphibians first appeared around 364 million years ago, followed by early amniotes and birds around 155 million years ago (both from " reptile "-like lineages), mammals around 129 million years ago, homininae around 10 million years ago and modern humans around 250,000 years ago. However, despite
10120-527: The largest environment on Earth, microbial marine systems drive changes in every global system. Microbes are responsible for virtually all the photosynthesis that occurs in the ocean, as well as the cycling of carbon , nitrogen , phosphorus , other nutrients and trace elements. Viruses [REDACTED] Bacteria [REDACTED] Archaea [REDACTED] Protists [REDACTED] Microfungi [REDACTED] Microanimals [REDACTED] Microscopic life undersea
10235-442: The largest reservoirs of unexplored genetic diversity on Earth. Bacteria constitute a large domain of prokaryotic microorganisms . Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth , and are present in most of its habitats . Bacteria inhabit soil, water, acidic hot springs , radioactive waste , and
10350-453: The latter include all that are not considered vertebrates . Generally, marine vertebrates are much more nektonic and metabolically demanding of oxygen and nutrients, often suffering distress or even mass dyings (a.k.a. " fish kills ") during anoxic events , while marine invertebrates are a lot more hypoxia -tolerant and exhibit a wide range of morphological and physiological modifications to survive in poorly oxygenated waters . There
10465-427: The latter include all the rest that must feed on other organisms to acquire nutrients and energy, which include animals, fungi, protists and non-photosynthetic microorganisms. Marine animals are further informally divided into marine vertebrates and marine invertebrates , both of which are polyphyletic groupings with the former including all saltwater fish , marine mammals , marine reptiles and seabirds , and
10580-536: The latter of which include two clades — the actinopterygians ( ray-finned fish ) and sarcopterygians ( lobe-finned fish ). One lineage of sarcopterygians, Rhipidistia , evolved the first four-limbed vertebrates , which would eventually become tetrapods . On land, plant groups diversified after the Silurian-Devonian Terrestrial Revolution ; the first woody ferns and the earliest seed plants evolved during this period. By
10695-504: The living space on Earth , and served as the cradle of life and vital biotic sanctuaries throughout Earth's geological history . The earliest known life forms evolved as anaerobic prokaryotes ( archaea and bacteria ) in the Archean oceans around the deep sea hydrothermal vents , before photoautotrophs appeared and allowed the microbial mats to expand into shallow water marine environments . The Great Oxygenation Event of
10810-633: The marine biomass. It is estimated viruses kill 20% of this biomass each day and that there are 15 times as many viruses in the oceans as there are bacteria and archaea. Viruses are the main agents responsible for the rapid destruction of harmful algal blooms , which often kill other marine life. The number of viruses in the oceans decreases further offshore and deeper into the water, where there are fewer host organisms. There are also archaeal viruses which replicate within archaea : these are double-stranded DNA viruses with unusual and sometimes unique shapes. These viruses have been studied in most detail in
10925-492: The morphological, or anatomical, record. By comparing the anatomies of both modern and extinct species, paleontologists can infer the lineages of those species. However, this approach is most successful for organisms that had hard body parts, such as shells, bones or teeth. Further, as prokaryotes such as bacteria and archaea share a limited set of common morphologies, their fossils do not provide information on their ancestry. More recently, evidence for common descent has come from
11040-559: The oceanic temperature distribution can cause significant weather shifts, such as the El Niño-Southern Oscillation . Altogether the ocean occupies 71 percent of the world surface, averaging nearly 3.7 kilometres (2.3 mi) in depth. By volume, the ocean provides about 90 percent of the living space on the planet. The science fiction writer Arthur C. Clarke has pointed out it would be more appropriate to refer to planet Earth as planet Ocean. However, water
11155-442: The oceans in the Ediacaran period. The evolution of multicellularity occurred in multiple independent events, in organisms as diverse as sponges , brown algae , cyanobacteria , slime moulds and myxobacteria . In 2016 scientists reported that, about 800 million years ago, a minor genetic change in a single molecule called GK-PID may have allowed organisms to go from a single cell organism to one of many cells. Soon after
11270-423: The oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are a major part of Earth's life and may play roles in both the carbon cycle and the nitrogen cycle . Phanerozoic The Phanerozoic is the current and the latest of the four geologic eons in the Earth 's geologic time scale , covering the time period from 538.8 million years ago to
11385-514: The phosphorus cycle, wherein increased phosphorus input into the ocean would increase surficial biological productivity that would in turn enhance iron redox cycling and thus remove phosphorus from seawater; this maintained a relatively stable rate of removal of carbon from the atmosphere and ocean via organic carbon burial. The climate also controlled the availability of phosphate through its regulation of rates of continental and seafloor weathering. Major global temperature variations of >7 °C during
11500-403: The planet is divided into five separate oceans, but these oceans all connect into a single world ocean . The mass of this world ocean is 1.35 × 10 metric tons or about 1/4400 of Earth's total mass. The world ocean covers an area of 3.618 × 10 km with a mean depth of 3682 m , resulting in an estimated volume of 1.332 × 10 km . If all of Earth's crustal surface was at
11615-443: The planet. Microscopic organisms live throughout the biosphere . The mass of prokaryote microorganisms — which includes bacteria and archaea, but not the nucleated eukaryote microorganisms — may be as much as 0.8 trillion tons of carbon (of the total biosphere mass , estimated at between 1 and 4 trillion tons). Single-celled barophilic marine microbes have been found at a depth of 10,900 m (35,800 ft) in
11730-586: The preceding Ediacaran period of the Proterozoic eon, known as the Avalon Explosion , have been identified since the systematic study of those forms started in the 1950s. The transition from the largely sessile Precambrian biota to the active mobile Cambrian biota occurred early in the Phanerozoic. The Phanerozoic is divided into three eras : the Paleozoic , Mesozoic and Cenozoic , which are further subdivided into 12 periods . The Paleozoic features
11845-574: The present. It is the eon during which abundant animal and plant life has proliferated , diversified and colonized various niches on the Earth's surface , beginning with the Cambrian period when animals first developed hard shells that can be clearly preserved in the fossil record . The time before the Phanerozoic, collectively called the Precambrian , is now divided into the Hadean , Archaean and Proterozoic eons. The time span of
11960-569: The process of evolution, with their diversity the product of a long series of speciation and extinction events. The common descent of organisms was first deduced from four simple facts about organisms: First, they have geographic distributions that cannot be explained by local adaptation. Second, the diversity of life is not a set of unique organisms, but organisms that share morphological similarities . Third, vestigial traits with no clear purpose resemble functional ancestral traits and finally, that organisms can be classified using these similarities into
12075-424: The researchers, "If life arose relatively quickly on Earth … then it could be common in the universe ." All organisms on Earth are descended from a common ancestor or ancestral gene pool . Highly energetic chemistry is thought to have produced a self-replicating molecule around 4 billion years ago, and half a billion years later the last common ancestor of all life existed. The current scientific consensus
12190-424: The salt in the ocean comes from the weathering and erosion of rocks on land. Some salts are released from volcanic activity or extracted from cool igneous rocks . The oceans are also a reservoir of dissolved atmospheric gases, which are essential for the survival of many aquatic life forms. Sea water has an important influence on the world's climate, with the oceans acting as a large heat reservoir . Shifts in
12305-428: The same elevation as a smooth sphere, the depth of the resulting world ocean would be about 2.7 kilometres (1.7 mi). About 97.5% of the water on Earth is saline ; the remaining 2.5% is fresh water . Most fresh water – about 69% – is present as ice in ice caps and glaciers . The average salinity of Earth's oceans is about 35 grams (1.2 oz) of salt per kilogram of seawater (3.5% salt). Most of
12420-541: The sea. Generally there are about 1 million to 10 million viruses in each mL of seawater, or about ten times more double-stranded DNA viruses than there are cellular organisms, although estimates of viral abundance in seawater can vary over a wide range. Tailed bacteriophages appear to dominate marine ecosystems in number and diversity of organisms. Bacteriophages belonging to the families Corticoviridae , Inoviridae and Microviridae are also known to infect diverse marine bacteria. Microorganisms make up about 70% of
12535-461: The study of biochemical similarities between organisms. For example, all living cells use the same basic set of nucleotides and amino acids . The development of molecular genetics has revealed the record of evolution left in organisms' genomes: dating when species diverged through the molecular clock produced by mutations. For example, these DNA sequence comparisons have revealed that humans and chimpanzees share 98% of their genomes and analysing
12650-424: The supercontinent Pangaea , surrounded by one expansive ocean called Panthalassa . The Earth was relatively dry compared to the Carboniferous, with harsh seasons , as the climate of the interior of Pangaea was not moderated by large bodies of water. Amniotes still flourished and diversified in the new dry climate, particularly synapsids such as Dimetrodon , Edaphosaurus and therapsids , which gave rise to
12765-483: The total marine biomass . Marine primary producers , mainly cyanobacteria and chloroplastic algae , produce oxygen and sequester carbon via photosynthesis , which generate enormous biomass and significantly influence the atmospheric chemistry . Migratory species, such as oceanodromous and anadromous fish , also create biomass and biological energy transfer between different regions of Earth, with many serving as keystone species of various ecosystems. At
12880-524: The volume of the Earth's ocean. There has been speculation Europa's ocean could support life , and could be capable of supporting multicellular microorganisms if hydrothermal vents are active on the ocean floor. Enceladus , a small icy moon of Saturn, also has what appears to be an underground ocean which actively vents warm water from the moon's surface. The Earth is about 4.54 billion years old. The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago, during
12995-654: The world, as did grazers. The Tethys Sea finally closed with the creation of the Arabian Peninsula and in its wake left the Black , Red , Mediterranean and Caspian seas. This only increased aridity. Many new plants evolved, and 95% of modern seed plants evolved in the mid-Miocene. The Pliocene lasted from 5.333 million to 2.58 million years ago. The Pliocene featured dramatic climatic changes, which ultimately led to modern species and plants. The Mediterranean Sea dried up for hundreds of thousand years in
13110-689: Was Sea Life Centre in Oban , Scotland, which opened in 1979. By 1992, nine other Sea Life units were opened. In November 2015, Merlin Entertainments announced that over the next 10 years it would invest £50 million in India, some of which will be used to open Sea Life centres. In January 2017, Merlin Entertainments Indian subsidiary stated that it was in discussion with real estate firms to open Sea Life centres in multiple cities in India. Sea Life centres have been criticised over animal welfare, with
13225-635: Was warm and humid, with little temperature gradient from pole to pole. In the Middle Eocene Epoch, the Antarctic Circumpolar Current formed when South America and Australia both separated from Antarctica to open up the Drake Passage and Tasmanian Passage , disrupting ocean currents worldwide, resulting in global cooling and causing the jungles to shrink. More modern forms of mammals continued to diversify with
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