HMS Fly (1831)
HMS Fly was an 18-gun sloop of the Royal Navy. She was responsible for the exploration and charting of much of Australia's north-east coast and nearby islands, she was converted to a coal hulk in 1855 and broken up in 1903. Fly was a development of the Orestes-class ship-sloop designed by Professor Inman of the School of Naval Architecture, she was 114 feet 4 inches long on the gundeck and 93 feet 6 1⁄8 inches at the keel. She had a beam of 31 feet 7 inches overall, a hold depth of 14 feet 5 inches, giving her a tonnage of 485 69/94 bm, her armament was made up of a pair of 9-pounder bow chasers. Fly and her three sister ships Harrier and Acorn were ordered on 30 January 1829, she was laid down in November 1829 and launched from Pembroke Dockyard on 25 August 1831. Argus and Acorn were cancelled on 27 April 1831, she was commissioned at Plymouth on 27 January 1832 under the command of Commander Peter M'Quhae and served on the North America and West Indies station, returning to Portsmouth on 30 September 1833.
After another two years on the same station she paid off at Portsmouth on 5 September 1835. By September 1836 she was fitting out for the South America station, including work in the Pacific Ocean, she was under the command of Commander Granville Gower Loch on that station from 1838 to 1840. She arrived at Spithead on 17 July 1840 from South America with 1,700,000 dollars and sailed for Plymouth to be paid off. In December 1841 she commissioned at Plymouth under the command of Francis Price Blackwood to survey the Torres Straits in company with the cutter Bramble. During the early to mid-1840s, she charted numerous routes through and from many locations around Australia's north-east coast and nearby islands, including Whitsunday Island and the Capricorn Islands. On 2 September 1844, she rescued the survivors of the British merchant ship Lady Grey, wrecked on Alert's Reef the previous day with the loss of a passenger whilst on a voyage from Sydney, New South Wales to Singapore. After being discovered during the survey of the Gulf of Papua, New Guinea, the Fly River was named after the ship.
Embarked during her voyages of exploration were the geologist and naturalist Joseph Jukes and the naturalist John MacGillivray. Fly returned to the United Kingdom, arriving at Spithead on 19 June 1846 and proceeded to Plymouth to pay off, she was commissioned again on 14 October 1847 under Commander Richard Oliver, was employed in surveying in the Pacific and New Zealand. After 4 years of work in the area she returned to the United Kingdom, arriving at Plymouth Sound on the evening of 4 December 1851 and paying off on 13 December, she was laid up as a coal hulk at Devonport in 1855. During this part of her career, she was renamed C2, C70, she was broken up in 1903. European and American voyages of scientific exploration Colledge, J. J.. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy. London: Chatham Publishing. ISBN 978-1-86176-281-8. OCLC 67375475. Jukes, J. Beete, Narrative of the surveying voyage of H. M. S. Fly commanded by Captain F. P. Blackwood, R. N. in Torres Strait, New Guinea, other islands of the Eastern Archipelago, during the year 1842-1846: together with an excursion into the interior of the eastern part of Java, London T. & W. Boone Laughton, John Knox.
"Loch, Granville Gower". In Lee, Sidney. Dictionary of National Biography. 34. London: Smith, Elder & Co. pp. 25, 26. Winfield, R.. The Sail and Steam Navy List: All the Ships of the Royal Navy 1815–1889. London: Chatham Publishing. ISBN 978-1-86176-032-6. Media related to HMS Fly at Wikimedia Commons
Anchisaurus is a genus of basal sauropodomorph dinosaur. It lived during the Early Jurassic Period, its fossils have been found in the red sandstone of the Portland Formation, deposited from the Hettangian age into the Sinemurian age, between about 200 and 195 million years ago; until it was classed as a member of Prosauropoda. The genus name Anchisaurus comes from the Greek αγχι/agkhi anchi-. Anchisaurus was coined as a replacement name for "Amphisaurus", itself a replacement name for Hitchcock's "Megadactylus", both of, used for other animals. Anchisaurus was a rather small dinosaur, with a length of just over 2 metres, which helps explain why it was once mistaken for human bones, it weighed around 27 kilograms. However, Marsh's species A. major was larger, from 2.5 to 4 metres and some estimates give it a weight of up to 70 pounds. Gregory S. Paul estimated its length at 2.2 meters and its weight at 20 kg in 2010. According to the presence of cf Otozum tracks on the Connecticut Valley the size of this animal can be bigger.
Otozoum tracks were made by a semibipedal to quadrupedal sauropodomorph close to or on the line leading toward eusauropods. Anchisaurus is one of the 2 Sauropodomorphs recognised in the zone. Based on the four known specimens of Anchisaurus, Yates estimated that this animal ranged up to 4.9 meters in length. This matches well with the estimated average size of the adult Eubrontes track-maker in the Hartford and Deerfield basins. Based on the largest known Eubrontes footprint, exceptionally large individuals of Anchisaurus ranged up to 6.0 meters in length. Sauropodomorph remains were first documented in North America in 1818, when some bones were uncovered by Mr. Solomon Ellsworth, Jr. while excavating a well with gunpowder in East Windsor, Connecticut. At the time of their discovery it was thought that the bones might be those of a human, but the presence of tail vertebrae falsified that idea, they are now recognized as those of an indeterminate sauropodomorph more related to the plateosaurian prosauropods.
In 1855, the original type specimen of Anchisaurus polyzelus, AM 41/109, housed at the Amherst College Museum of Natural History, was found by William Smith in Springfield, Massachusetts during blasting a well for the waterhouse at the Springfield Armory. Both the East Windsor and Springfield specimens were damaged due to the blasting at the construction sites where they were found, many of the bones were either accidentally thrown away by the workmen or kept by interested onlookers; as a result, these dinosaurs were only known from incomplete remains. In 1863, the son of the ichnologist Edward Hitchcock, Edward Hitchcock Jr, described the Springfield remains in a supplement to his father's work on fossil footprints, suggesting they could explain a certain mysterious kind of reptile tracks, he contacted the British paleontologist Richard Owen. Owen advised him to name the finds as a new genus. Owen suggested the name Megadactylus, "large finger" in Greek, in reference to the enormous thumb of the animal.
Hitchcock Jr himself chose the specific name polyzelus, "much sought for" in Greek, referring to the fact that his father had for many years vainly sought to discover the identity of the track-maker. In 1877, Professor Othniel Charles Marsh had noted that the name Megadactylus had been preoccupied by Megadactylus Fitzinger 1843, a subgenus of the lizard genus Stellio. In 1882, he replaced the name with Amphisaurus, "near saurian" referring to Marsh's interpretation of it as intermediate between primitive dinosaurs — at the time the British Palaeosaurus was an example of what was thought to be a primitive dinosaur — and more derived dinosaurs. In 1885, Marsh had discovered that this name had been preoccupied, by the athracosaurian Amphisaurus Barkas 1870, again replaced it by Anchisaurus, with the same meaning. Meanwhile, nearly complete specimens had been found in Connecticut. In 1884, a series of bridges was built over the Hop Creek. Sandstone blocks were sawed out of Wolcott's Quarry north of Buckland Station.
On 20 October, an amateur paleontologist, Charles H. Owen, observed that a block had been removed containing the hind part of a skeleton, he warned Marsh who, using T. A. Bostwick as an intermediary, acquired the piece from Charles O. Wolcott. Marsh tried to secure the front half of the skeleton but it had been used in a bridge abutment; the specimen, YPM 208, was named Anchisaurus major, "the larger one", by Marsh in 1889. When the bridge was demolished in August 1969, John Ostrom would save the front block. Subsequently, two other dinosaur fossils were located in the quarry. Six metres south of the original find, it was removed as a single block and given the inventory number YPM 1883. In Yale, the part containing the skull was split off and became specimen YPM 40313. In 1891, Marsh made Anchisaurus major a separate genus, the "sand saurian". In the same publication he named YPM 1883/YPM 40313 as a new species of Anchisaurus, Anchisaurus colurus, "the mangled one", they served as the templates from which O.
C. Marsh in 1893 restored the skeleton; the Manchester specimens are now considered conspecific with Anchisaurus polyzelus. The East Windsor and Manchester specimens are housed at the Peabody Museum of Natural History at Yale University; the type species is Hitchcock's A. polyzelus. Marsh's A. major, A. solus, A. colurus, have since been recognized as synonyms of A. polyzelus, the
Saurischia is one of the two basic divisions of dinosaurs. ‘Saurischia’ translates to lizard-hipped. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure, though today most paleontologists classify Saurischia as an unranked clade rather than an order. All carnivorous dinosaurs are traditionally classified as saurischians, as are all of the birds and one of the two primary lineages of herbivorous dinosaurs, the sauropodomorphs. At the end of the Cretaceous Period, all saurischians except the birds became extinct in the course of the Cretaceous–Paleogene extinction event. Birds, as direct descendants of one group of theropod dinosaurs, are a sub-clade of saurischian dinosaurs in phylogenetic classification. Saurischian dinosaurs are traditionally distinguished from ornithischian dinosaurs by their three-pronged pelvic structure, with the pubis pointed forward; the ornithischians' pelvis is arranged with the pubis rotated backward, parallel with the ischium also with a forward-pointing process, giving a four-pronged structure.
The saurischian hip structure led Seeley to name them "lizard-hipped" dinosaurs, because they retained the ancestral hip anatomy found in modern lizards and other reptiles. He named ornithischians "bird-hipped" dinosaurs because their hip arrangement was superficially similar to that of birds, though he did not propose any specific relationship between ornithischians and birds. However, in the view which has long been held, this "bird-hipped" arrangement evolved several times independently in dinosaurs, first in the ornithischians in the lineage of saurischians including birds, lastly in the therizinosaurians; this would be an example of convergent evolution, therizinosaurians, ornithischian dinosaurs all developed a similar hip anatomy independently of each other as an adaptation to their herbivorous or omnivorous diets. In his paper naming the two groups, Seeley reviewed previous classification schemes put forth by other paleontologists to divide up the traditional order Dinosauria, he preferred one, put forward by Othniel Charles Marsh in 1878, which divided dinosaurs into four orders: Sauropoda, Theropoda and Stegosauria.
Seeley, wanted to formulate a classification that would take into account a single primary difference between major dinosaurian groups based on a characteristic that differentiated them from other reptiles. He found this in the configuration of the hip bones, found that all four of Marsh's orders could be divided neatly into two major groups based on this feature, he placed the Stegosauria and Ornithopoda in the Ornithischia, the Theropoda and Sauropoda in the Saurischia. Furthermore, Seeley used this major difference in the hip bones, along with many other noted differences between the two groups, to argue that "dinosaurs" were not a natural grouping at all, but rather two distinct orders that had arisen independently from more primitive archosaurs; this concept that "dinosaur" was an outdated term for two distinct orders lasted many decades in the scientific and popular literature, it was not until the 1960s that scientists began to again consider the possibility that saurischians and ornithischians were more related to each other than they were to other archosaurs.
Although his concept of a polyphyletic Dinosauria is no longer accepted by most paleontologists, Seeley's basic division of the two dinosaurian groups has stood the test of time, has been supported by modern cladistic analysis of relationships among dinosaurs. One alternative hypothesis challenging Seeley's classification was proposed by Robert T. Bakker in his 1986 book The Dinosaur Heresies. Bakker's classification separated the theropods into their own group and placed the two groups of herbivorous dinosaurs together in a separate group he named the Phytodinosauria; the Phytodinosauria hypothesis was based on the supposed link between ornithischians and prosauropods, the idea that the former had evolved directly from the latter by way of an enigmatic family that seemed to possess characters of both groups, the segnosaurs. However, it was found that segnosaurs were an unusual type of herbivorous theropod saurischian related to birds, the Phytodinosauria hypothesis fell out of favor. A 2017 study by Dr Matthew Grant Baron, Dr David B. Norman and Prof. Paul M. Barrett did not find support for a monophyletic Saurischia, according to its traditional definition.
Instead, the group was found to be paraphyletic, with Theropoda removed from the group and placed as the sister group to the Ornithischia in the newly defined clade Ornithoscelida. As a result, the authors redefined Saurischia as "the most inclusive clade that contains D. carnegii, but not T. horridus", resulting in a clade containing only the Sauropodomorpha and Herrerasauridae
A sloop is a sailing boat with a single mast and a fore-and-aft rig. A sloop has only one head-sail; the most common rig of modern sailboats is the Bermuda-rigged sloop. A modern sloop carries a mainsail on a boom aft of the mast, with a single loose-footed head-sail forward of the mast. Sloops are either fractional-rigged. On a masthead-rigged sloop, the forestay attaches at the top of the mast. On a fractional-rigged sloop, the forestay attaches to the mast at a point below the top 3/4 of the way to top, or 7/8 or some other fraction. Compared to a masthead-rigged sloop, the mast of a fractional-rigged sloop may be placed farther forward. After the cat rig which has only a single sail, the sloop rig is one of the simpler sailing rig configurations. A sloop has two sails, a mainsail and a headsail, while the cutter has a mainsail and two or more headsails. Next in complexity are the ketch, the yawl and the schooner, each of which has two masts and a minimum of three sails. A sloop has a simple system of mast rigging -- a backstay and shrouds.
By having only two sails, the individual sails of a sloop are larger than those of an equivalent cutter, yawl or ketch. Until the advent of lightweight sailcloth and modern sail-handling systems, the larger sails of a sloop could be a handful. So, until the 1950s, sailboats over 10 metres length overall would use a cutter rig or a two-mast rig. After the advent of modern winches and light sailcloth, the sloop became the dominant sailing rig type for all but the largest sailboats. No rig type is perfect for all conditions. Sloops, with their paucity of spars and control lines, tend to impart less aerodynamic drag. Compared to other rigs, sloops tend to perform well when sailing close hauled to windward and offer a sound overall compromise of abilities on all points of sail. Cutters and yawls are preferred to sloops when venturing far offshore, because it is easier to reef small sails as the wind increases, while still keeping the boat balanced. To maximize the amount of sail carried, the classic sloop may use a bowsprit, a spar that projects forward from the bow.
The foresail may be a jib, which does not overlap the mast more than 10 to 20 percent, or a much larger genoa. The genoa's large overlap behind the mainsail helps to guide the airflow and thereby makes the mainsail more effective. For downwind sailing, the jib or genoa may be replaced by larger curved sails known as spinnakers or gennakers. Nowadays, by far the most common sloop rig, for yachts and dinghies, is the Bermuda rig, the optimal rig for upwind sailing. Originating from the island of Bermuda in the 17th century, the Bermuda rig is simple, yet may be tuned to be maneuverable and fast; the main disadvantage is the large size of the sails on larger vessels. It is less successful sailing downwind, when the addition of a spinnaker becomes necessary for faster progress in all but the strongest winds. However, the spinnaker is an intrinsically unstable sail requiring continuous trimming. An alternative downwind sailplan, more stable but slower, is the "wing on wing". Here, the main is swung wide to lee while the jib is swung wide to windward.
However the "wing on wing" configuration tends to dip the bow, requiring crew to move aft to counterbalance the dip. The wing on wing configuration cannot be heeled over to decrease waterline whereas the spinnaker configuration can be. If not tended the main can go slack to the point of being dangerously close to jibing; the jib will have that same tendency and being to windward, will snap a-lee but with no boom and being forward of the mast will make for a far less dangerous move than that of the main. A slack main when to leeward can be brought back under control by hauling on the mainsheet to bring it back in contact with the wind when on the aft quarter to windward but if the wind comes around onto the aft quarter of what had been to lee, the boat must be brought further a-lee to keep the wind strong on the main. Jamaican sloops had beams that were narrower than ocean-going Bermuda sloops, could attain a speed of around 12 knots, they carried gaff rig. The keel of Jamaican sloops would be between 50–75 feet, but could be built longer.
Jamaican sloops were built near the shore and out of cedar trees, for much the same reasons that Bermudian shipwrights favoured the Bermuda cedar: these were resistant to rot, grew fast and tall, had a taste displeasing to marine borers. Cedar was favoured over oak as the latter would rot in about 10 years, while cedar would last for nigh on 30 years and was lighter than oak. Since piracy was a significant threat in Caribbean waters, merchants sought ships that could outrun pursuers; that same speed and maneuverability made them prized and more targeted by the pirates they were designed to avoid. When the ships needed to be de-fouled from seaweed and barnacles, pirates needed a safe haven on which to car
The Neogene is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago to the beginning of the present Quaternary Period 2.58 Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the Pliocene; some geologists assert that the Neogene cannot be delineated from the modern geological period, the Quaternary. The term "Neogene" was coined in 1853 by the Austrian palaeontologist Moritz Hörnes. During this period and birds continued to evolve into modern forms, while other groups of life remained unchanged. Early hominids, the ancestors of humans, appeared in Africa near the end of the period; some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama, late in the Pliocene. This cut off the warm ocean currents from the Pacific to the Atlantic Ocean, leaving only the Gulf Stream to transfer heat to the Arctic Ocean; the global climate cooled over the course of the Neogene, culminating in a series of continental glaciations in the Quaternary Period that follows.
In ICS terminology, from upper to lower: The Pliocene Epoch is subdivided into 2 ages: Piacenzian Age, preceded by Zanclean AgeThe Miocene Epoch is subdivided into 6 ages: Messinian Age, preceded by Tortonian Age Serravallian Age Langhian Age Burdigalian Age Aquitanian AgeIn different geophysical regions of the world, other regional names are used for the same or overlapping ages and other timeline subdivisions. The terms Neogene System and upper Tertiary System describe the rocks deposited during the Neogene Period; the continents in the Neogene were close to their current positions. The Isthmus of Panama formed, connecting South America; the Indian subcontinent continued forming the Himalayas. Sea levels fell, creating land bridges between Africa and Eurasia and between Eurasia and North America; the global climate became seasonal and continued an overall drying and cooling trend which began at the start of the Paleogene. The ice caps on both poles began to grow and thicken, by the end of the period the first of a series of glaciations of the current Ice Age began.
Marine and continental flora and fauna have a modern appearance. The reptile group Choristodera became extinct in the early part of the period, while the amphibians known as Allocaudata disappeared at the end. Mammals and birds continued to be the dominant terrestrial vertebrates, took many forms as they adapted to various habitats; the first hominins, the ancestors of humans, may have appeared in southern Europe and migrated into Africa. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones and grasslands replaced many forests. Grasses therefore diversified, herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses and bison. Eucalyptus fossil leaves occur in the Miocene of New Zealand, where the genus is not native today, but have been introduced from Australia; the Neogene traditionally ended at the end of the Pliocene Epoch, just before the older definition of the beginning of the Quaternary Period. However, there was a movement amongst geologists to include ongoing geological time in the Neogene, while others insist the Quaternary to be a separate period of distinctly different record.
The somewhat confusing terminology and disagreement amongst geologists on where to draw what hierarchical boundaries is due to the comparatively fine divisibility of time units as time approaches the present, due to geological preservation that causes the youngest sedimentary geological record to be preserved over a much larger area and to reflect many more environments than the older geological record. By dividing the Cenozoic Era into three periods instead of seven epochs, the periods are more comparable to the duration of periods in the Mesozoic and Paleozoic eras; the International Commission on Stratigraphy once proposed that the Quaternary be considered a sub-era of the Neogene, with a beginning date of 2.58 Ma, namely the start of the Gelasian Stage. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs; the International Union for Quaternary Research counterproposed that the Neogene and the Pliocene end at 2.58 Ma, that the Gelasian be transferred to the Pleistocene, the Quaternary be recognized as the third period in the Cenozoic, citing key changes in Earth's climate and biota that occurred 2.58 Ma and its correspondence to the Gauss-Matuyama magnetostratigraphic boundary.
In 2006 ICS and INQUA reached a compromise that made Quaternary a subera, subdividing Cenozoic into the old classical Tertiary and Quaternary, a compromise, rejected by International Union of Geological Sciences because it split both Neogene and Pliocene in two. Following formal discussions at the 2008 International Geological Congress in Oslo, the ICS decided in May 2009 to make the Quaternary the youngest period of the Cenozoic Era with its base at 2.58 Mya and including the Gelasian age, considered part of the Neogene Period and Pliocene Epoch. Thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya. "Digital Atlas of Neogene Life for the Southeastern United States". San Jose State University. Archived from the original on 2013-04-23. Retrieved 21 September 2018
The matrix or groundmass of a rock is the finer-grained mass of material in which larger grains, crystals or clasts are embedded. The matrix of an igneous rock consists of finer-grained microscopic, crystals in which larger crystals are embedded; this porphyritic texture is indicative of multi-stage cooling of magma. For example, porphyritic andesite will have large phenocrysts of plagioclase in a fine-grained matrix. In South Africa, diamonds are mined from a matrix of weathered clay-like rock called "yellow ground"; the matrix of sedimentary rocks is finer-grained sedimentary material, such as clay or silt, in which larger grains or clasts are embedded. It is used to describe the rock material in which a fossil is embedded. All sediments are at first in an incoherent condition, they may remain in this state for an indefinite period. Millions of years have elapsed since some of the early Tertiary strata gathered on the ocean floor, yet they are quite friable and differ little from many recent accumulations.
There are few exceptions, however, to the rule that with increasing age sedimentary rocks become more and more indurated, the older they are the more it is that they will have the firm consistency implied in the term "rock". The pressure of newer sediments on underlying masses is one cause of this change, though not in itself a powerful one. More efficiency is ascribed to the action of percolating water, which takes up certain soluble materials and redeposits them in pores and cavities; this operation is accelerated by the increased pressure produced by superincumbent masses, to some extent by the rise of temperature which takes place in rocks buried to some depth beneath the surface. The rise of temperature, however, is never great; the redeposited cementing material is most calcareous or siliceous. Limestones, which were a loose accumulation of shells, etc. become compacted into firm rock in this manner. The cementing substance may be deposited in crystalline continuity on the original grains, where these were crystalline, in sandstones, a crystalline matrix of calcite envelops the sand grains.
The change of aragonite to calcite and of calcite to dolomite, by forming new crystalline masses in the interior of the rock also accelerates consolidations. Silica is less soluble in ordinary waters, but this ingredient of rocks is dissolved and redeposited with great frequency. Many sandstones are held together by an infinitesimal amount of cryptocrystalline silica. Others contain fine scales of mica. Argillaceous materials may be compacted by mere pressure, like graphite and other scaly minerals
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results