An arthropod is an invertebrate animal having an exoskeleton, a segmented body, paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids and crustaceans; the term Arthropoda as proposed refers to a proposed grouping of Euarthropods and the phylum Onychophora. Arthropods are characterized by their jointed limbs and cuticle made of chitin mineralised with calcium carbonate; the arthropod body plan consists of each with a pair of appendages. The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Arthopods are bilaterally symmetrical and their body possesses an external skeleton; some species have wings. Their versatility has enabled them to become the most species-rich members of all ecological guilds in most environments, they have over a million described species, making up more than 80 per cent of all described living animal species, some of which, unlike most other animals, are successful in dry environments. Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab.
Arthropods' primary internal cavity is a haemocoel, which accommodates their internal organs, through which their haemolymph – analogue of blood – circulates. Like their exteriors, the internal organs of arthropods are built of repeated segments, their nervous system is "ladder-like", with paired ventral nerve cords running through all segments and forming paired ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, their brains are formed by fusion of the ganglia of these segments and encircle the esophagus; the respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong. Their vision relies on various combinations of compound eyes and pigment-pit ocelli: in most species the ocelli can only detect the direction from which light is coming, the compound eyes are the main source of information, but the main eyes of spiders are ocelli that can form images and, in a few cases, can swivel to track prey.
Arthropods have a wide range of chemical and mechanical sensors based on modifications of the many setae that project through their cuticles. Arthropods' methods of reproduction and development are diverse; the evolutionary ancestry of arthropods dates back to the Cambrian period. The group is regarded as monophyletic, many analyses support the placement of arthropods with cycloneuralians in a superphylum Ecdysozoa. Overall, the basal relationships of Metazoa are not yet well resolved; the relationships between various arthropod groups are still debated. Aquatic species use either external fertilization. All arthropods lay eggs, but scorpions give birth to live young after the eggs have hatched inside the mother. Arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and undergo a total metamorphosis to produce the adult form; the level of maternal care for hatchlings varies from nonexistent to the prolonged care provided by scorpions. Arthropods contribute to the human food supply both directly as food, more indirectly as pollinators of crops.
Some species are known to spread severe disease to humans and crops. The word arthropod comes from the Greek ἄρθρον árthron, "joint", πούς pous, i.e. "foot" or "leg", which together mean "jointed leg". Arthropods are invertebrates with jointed limbs; the exoskeleton or cuticles consists of a polymer of glucosamine. The cuticle of many crustaceans, beetle mites, millipedes is biomineralized with calcium carbonate. Calcification of the endosternite, an internal structure used for muscle attachments occur in some opiliones. Estimates of the number of arthropod species vary between 1,170,000 and 5 to 10 million and account for over 80 per cent of all known living animal species; the number of species remains difficult to determine. This is due to the census modeling assumptions projected onto other regions in order to scale up from counts at specific locations applied to the whole world. A study in 1992 estimated that there were 500,000 species of animals and plants in Costa Rica alone, of which 365,000 were arthropods.
They are important members of marine, freshwater and air ecosystems, are one of only two major animal groups that have adapted to life in dry environments. One arthropod sub-group, insects, is the most species-rich member of all ecological guilds in land and freshwater environments; the lightest insects weigh less than 25 micrograms. Some living crustaceans are much larger; the embryos of all arthropods are segmented, built from a series of repeated modules. The last common ancestor of living arthropods consisted of a series of undifferentiated segments, each with a pair of appendages that functioned as limbs. However, all known living and fossil arthropods have grouped segments into tagmata in which segments and their limbs are specialized in various ways; the three-
Natural History Museum, London
The Natural History Museum in London is a natural history museum that exhibits a vast range of specimens from various segments of natural history. It is one of three major museums on Exhibition Road in South Kensington, the others being the Science Museum and the Victoria and Albert Museum; the Natural History Museum's main frontage, however, is on Cromwell Road. The museum is home to life and earth science specimens comprising some 80 million items within five main collections: botany, mineralogy and zoology; the museum is a centre of research specialising in taxonomy and conservation. Given the age of the institution, many of the collections have great historical as well as scientific value, such as specimens collected by Charles Darwin; the museum is famous for its exhibition of dinosaur skeletons and ornate architecture—sometimes dubbed a cathedral of nature—both exemplified by the large Diplodocus cast that dominated the vaulted central hall before it was replaced in 2017 with the skeleton of a blue whale hanging from the ceiling.
The Natural History Museum Library contains extensive books, journals and artwork collections linked to the work and research of the scientific departments. The museum is recognised as the pre-eminent centre of natural history and research of related fields in the world. Although referred to as the Natural History Museum, it was known as British Museum until 1992, despite legal separation from the British Museum itself in 1963. Originating from collections within the British Museum, the landmark Alfred Waterhouse building was built and opened by 1881 and incorporated the Geological Museum; the Darwin Centre is a more recent addition designed as a modern facility for storing the valuable collections. Like other publicly funded national museums in the United Kingdom, the Natural History Museum does not charge an admission fee; the museum is an exempt charity and a non-departmental public body sponsored by the Department for Culture and Sport. Catherine, Duchess of Cambridge is a patron of the museum.
There are 850 staff at the Museum. The two largest strategic groups are Science Group; the foundation of the collection was that of the Ulster doctor Sir Hans Sloane, who allowed his significant collections to be purchased by the British Government at a price well below their market value at the time. This purchase was funded by a lottery. Sloane's collection, which included dried plants, animal and human skeletons, was housed in Montagu House, Bloomsbury, in 1756, the home of the British Museum. Most of the Sloane collection had disappeared by the early decades of the nineteenth century. Dr George Shaw sold many specimens to the Royal College of Surgeons and had periodic cremations of material in the grounds of the museum, his successors applied to the trustees for permission to destroy decayed specimens. In 1833 the Annual Report states that, of the 5,500 insects listed in the Sloane catalogue, none remained; the inability of the natural history departments to conserve its specimens became notorious: the Treasury refused to entrust it with specimens collected at the government's expense.
Appointments of staff were bedevilled by gentlemanly favoritism. J. E. Gray complained of the incidence of mental illness amongst staff: George Shaw threatened to put his foot on any shell not in the 12th edition of Linnaeus' Systema Naturae; the huge collection of the conchologist Hugh Cuming was acquired by the museum, Gray's own wife had carried the open trays across the courtyard in a gale: all the labels blew away. That collection is said never to have recovered; the Principal Librarian at the time was Antonio Panizzi. The general public was not encouraged to visit the Museum's natural history exhibits. In 1835 to a Select Committee of Parliament, Sir Henry Ellis said this policy was approved by the Principal Librarian and his senior colleagues. Many of these faults were corrected by the palaeontologist Richard Owen, appointed Superintendent of the natural history departments of the British Museum in 1856, his changes led Bill Bryson to write that "by making the Natural History Museum an institution for everyone, Owen transformed our expectations of what museums are for".
Owen saw that the natural history departments needed more space, that implied a separate building as the British Museum site was limited. Land in South Kensington was purchased, in 1864 a competition was held to design the new museum; the winning entry was submitted by the civil engineer Captain Francis Fowke, who died shortly afterwards. The scheme was taken over by Alfred Waterhouse who revised the agreed plans, designed the façades in his own idiosyncratic Romanesque style, inspired by his frequent visits to the Continent; the original plans included wings on either side of the main building, but these plans were soon abandoned for budgetary reasons. The space these would have occupied are now taken by the Earth Galleries and Darwin Centre. Work began in 1873 and was completed in 1880; the new museum opened in 1881, although the move from the old museum was not completed until 1883. Both the interiors and exteriors of the Waterhouse building make extensive use of
Bolivia the Plurinational State of Bolivia is a landlocked country located in western-central South America. The capital is Sucre; the largest city and principal industrial center is Santa Cruz de la Sierra, located on the Llanos Orientales a flat region in the east of Bolivia. The sovereign state of Bolivia is a constitutionally unitary state, divided into nine departments, its geography varies from the peaks of the Andes in the West, to the Eastern Lowlands, situated within the Amazon Basin. It is bordered to the north and east by Brazil, to the southeast by Paraguay, to the south by Argentina, to the southwest by Chile, to the northwest by Peru. One-third of the country is within the Andean mountain range. With 1,098,581 km2 of area, Bolivia is the fifth largest country in South America, the 27th largest in the world and the largest landlocked country in the Southern Hemisphere; the country's population, estimated at 11 million, is multiethnic, including Amerindians, Europeans and Africans.
The racial and social segregation that arose from Spanish colonialism has continued to the modern era. Spanish is the official and predominant language, although 36 indigenous languages have official status, of which the most spoken are Guarani and Quechua languages. Before Spanish colonization, the Andean region of Bolivia was part of the Inca Empire, while the northern and eastern lowlands were inhabited by independent tribes. Spanish conquistadors arriving from Cuzco and Asunción took control of the region in the 16th century. During the Spanish colonial period Bolivia was administered by the Royal Audiencia of Charcas. Spain built its empire in large part upon the silver, extracted from Bolivia's mines. After the first call for independence in 1809, 16 years of war followed before the establishment of the Republic, named for Simón Bolívar. Over the course of the 19th and early 20th century Bolivia lost control of several peripheral territories to neighboring countries including the seizure of its coastline by Chile in 1879.
Bolivia remained politically stable until 1971, when Hugo Banzer led a coup d'état which replaced the socialist government of Juan José Torres with a military dictatorship headed by Banzer. Banzer's regime cracked down on leftist and socialist opposition and other forms of dissent, resulting in the torture and deaths of a number of Bolivian citizens. Banzer was ousted in 1978 and returned as the democratically elected president of Bolivia from 1997 to 2001. Modern Bolivia is a charter member of the UN, IMF, NAM, OAS, ACTO, Bank of the South, ALBA and USAN. For over a decade Bolivia has had one of the highest economic growth rates in Latin America, it is a developing country, with a medium ranking in the Human Development Index, a poverty level of 38.6%, one of the lowest crime rates in Latin America. Its main economic activities include agriculture, fishing and manufacturing goods such as textiles, refined metals, refined petroleum. Bolivia is rich in minerals, including tin and lithium. Bolivia is named after Simón Bolívar, a Venezuelan leader in the Spanish American wars of independence.
The leader of Venezuela, Antonio José de Sucre, had been given the option by Bolívar to either unite Charcas with the newly formed Republic of Peru, to unite with the United Provinces of Rio de la Plata, or to formally declare its independence from Spain as a wholly independent state. Sucre opted to create a brand new state and on 6 August 1825, with local support, named it in honor of Simón Bolívar; the original name was Republic of Bolívar. Some days congressman Manuel Martín Cruz proposed: "If from Romulus comes Rome from Bolívar comes Bolivia"; the name was approved by the Republic on 3 October 1825. In 2009, a new constitution changed the country's official name to "Plurinational State of Bolivia" in recognition of the multi-ethnic nature of the country and the enhanced position of Bolivia's indigenous peoples under the new constitution; the region now known as Bolivia had been occupied for over 2,500 years. However, present-day Aymara associate themselves with the ancient civilization of the Tiwanaku culture which had its capital at Tiwanaku, in Western Bolivia.
The capital city of Tiwanaku dates from as early as 1500 BC when it was a small, agriculturally based village. The community grew to urban proportions between AD 600 and AD 800, becoming an important regional power in the southern Andes. According to early estimates, the city covered 6.5 square kilometers at its maximum extent and had between 15,000 and 30,000 inhabitants. In 1996 satellite imaging was used to map the extent of fossilized suka kollus across the three primary valleys of Tiwanaku, arriving at population-carrying capacity estimates of anywhere between 285,000 and 1,482,000 people. Around AD 400, Tiwanaku went from being a locally dominant force to a predatory state. Tiwanaku expanded its reaches into the Yungas and brought its culture and way of life to many other cultures in Peru and Chile. Tiwanaku was not a violent culture in many respects. In order to expand its reach, Tiwanaku exercised great political astuteness, creating colonies, fostering trade agree
South America is a continent in the Western Hemisphere in the Southern Hemisphere, with a small portion in the Northern Hemisphere. It may be considered a subcontinent of the Americas, how it is viewed in the Spanish and Portuguese-speaking regions of the Americas; the reference to South America instead of other regions has increased in the last decades due to changing geopolitical dynamics. It is bordered on the west on the north and east by the Atlantic Ocean, it includes twelve sovereign states, a part of France, a non-sovereign area. In addition to this, the ABC islands of the Kingdom of the Netherlands and Tobago, Panama may be considered part of South America. South America has an area of 17,840,000 square kilometers, its population as of 2016 has been estimated at more than 420 million. South America ranks fourth in fifth in population. Brazil is by far the most populous South American country, with more than half of the continent's population, followed by Colombia, Argentina and Peru. In recent decades Brazil has concentrated half of the region's GDP and has become a first regional power.
Most of the population lives near the continent's western or eastern coasts while the interior and the far south are sparsely populated. The geography of western South America is dominated by the Andes mountains. Most of the continent lies in the tropics; the continent's cultural and ethnic outlook has its origin with the interaction of indigenous peoples with European conquerors and immigrants and, more locally, with African slaves. Given a long history of colonialism, the overwhelming majority of South Americans speak Portuguese or Spanish, societies and states reflect Western traditions. South America occupies the southern portion of the Americas; the continent is delimited on the northwest by the Darién watershed along the Colombia–Panama border, although some may consider the border instead to be the Panama Canal. Geopolitically and geographically all of Panama – including the segment east of the Panama Canal in the isthmus – is included in North America alone and among the countries of Central America.
All of mainland South America sits on the South American Plate. South America is home to Angel Falls in Venezuela. South America's major mineral resources are gold, copper, iron ore and petroleum; these resources found in South America have brought high income to its countries in times of war or of rapid economic growth by industrialized countries elsewhere. However, the concentration in producing one major export commodity has hindered the development of diversified economies; the fluctuation in the price of commodities in the international markets has led to major highs and lows in the economies of South American states causing extreme political instability. This is leading to efforts to diversify production to drive away from staying as economies dedicated to one major export. South America is one of the most biodiverse continents on earth. South America is home to many interesting and unique species of animals including the llama, piranha, vicuña, tapir; the Amazon rainforests possess high biodiversity, containing a major proportion of the Earth's species.
Brazil is the largest country in South America, encompassing around half of the continent's land area and population. The remaining countries and territories are divided among three regions: The Andean States, the Guianas and the Southern Cone. Traditionally, South America includes some of the nearby islands. Aruba, Curaçao, Trinidad and the federal dependencies of Venezuela sit on the northerly South American continental shelf and are considered part of the continent. Geo-politically, the island states and overseas territories of the Caribbean are grouped as a part or subregion of North America, since they are more distant on the Caribbean Plate though San Andres and Providencia are politically part of Colombia and Aves Island is controlled by Venezuela. Other islands that are included with South America are the Galápagos Islands that belong to Ecuador and Easter Island, Robinson Crusoe Island, Chiloé and Tierra del Fuego. In the Atlantic, Brazil owns Fernando de Noronha and Martim Vaz, the Saint Peter and Saint Paul Archipelago, while the Falkland Islands are governed by the United Kingdom, whose sovereignty over the islands is disputed by Argentina.
South Georgia and the South Sandwich Islands may be associate
The Hepialidae are a family of insects in the lepidopteran order. Moths of this family are referred to as swift moths or ghost moths; the Hepialidae constitute by far the most diverse group of the infraorder Exoporia. The 60 genera contain at least 587 recognised species of these primitive moths worldwide; the genera Fraus, Gazoryctra and Antihepialus are considered to be the most primitive, containing four genera and about 51 species with a relictual southern Gondwanan distribution and are separated from the Hepialidae sensu stricto which might form a natural, derived group. The most diverse genera are Oxycanus with 73 species, Endoclita with 60 species, Thitarodes with 51 species and Cibyra with 50 species following a comprehensive catalogue of Exoporia; the relationships of the many genera are not yet well established. The family Hepialidae is considered to be primitive, with a number of structural differences to other moths including short antennae and the lack of a functional proboscis or frenulum.
Like other Exoporia the sperm is transferred to the egg by an external channel between the ostium and the ovipore. Other nonditrysian moths have a common cloaca; the moths are homoneurous with similar forewings and hindwings, are sometimes included as'honorary' members of the Macrolepidoptera, though archaic they are. Speaking, they are phylogenetically too basal and constitute Microlepidoptera, although hepialids range from small moths to a wingspan record of 250 mm in Zelotypia; because of their sometimes large size and striking colour patterns, they have received more popular and taxonomic attention than most "micros". Many species display strong sexual dimorphism, with males smaller but more boldly marked than females, or at high elevation, females of Pharmacis and Aoraia show "brachypterous" wing reduction. Hepialidae are distributed on ancient landmasses worldwide except Antarctica but with the surprising exceptions of Madagascar, the Caribbean islands and in Africa, tropical West Africa.
It remains to be borne out if these absences are real as Aenetus cohici was not long ago discovered in New Caledonia. In the Oriental and Neotropical regions hepialids have diversified in rainforest environments, but this not the case in the Afrotropics. Hepialids have low dispersive powers and do not occur on oceanic islands with the exception of Phassodes on Fiji and Western Samoa and a few species in Japan and Kurile Islands. Whilst the type locality of Eudalaca sanctahelena is from the remote island of St Helena, this is thought to be an error for South Africa. Swift moths are crepuscular and some species form leks thought to have arisen independently in the genus Ogygioses. In most genera, males fly swiftly to virgin females. In other genera, virgin females "assemble" upwind to displaying males, which emit a musky pheromone from scales on the metathoracic tibiae. In such cases of sex role reversal, there may be visual cues also: males of the European ghost swift are the most noticed species, being white and conspicuous when forming a lek at dusk.
Sometimes they hover singly as if flying in a figure of eight motion. The chemical structures of some pheromones have been analysed; the female does not lay its eggs in a specific location but scatters them while in flight, sometimes in huge numbers. The maggot-like larvae feed in a variety of ways. All Exoporia have concealed larvae, making silken tunnels in all manner of substrates; some species feed on leaf litter, mosses, decaying vegetation, gymnosperms and a wide span of monocot and dicot plants. There is little evidence of hostplant specialisation. A few feed on foliage. Most feed underground on fine roots, at least in early instars and some feed internally in tunnels in the stem or trunk of their hostplants; the pupa has rows of dorsal spines on the abdominal segments as in other lower members of the Heteroneura. Chinese medicine makes considerable use of the "mummies" collected of the caterpillar-attacking fungi Ophiocordyceps sinensis, these can form an expensive ingredient; the Witchetty grub is a popular food source among aboriginal Australians.
In Central America and South America, hepialid larvae are eaten. However, some species of Wiseana, Oxycanus and Dalaca are considered pests of pastures in Australia, New Zealand, South America. Source and identification Gazoryctra fuscoargenteus O. Bang-Haas 1927 - Northern Scandinavia Gazoryctra ganna - Alps, northern Scandinavia, northern Russia Hepialus humuli Linnaeus 1758 - Europe Korscheltellus lupulina Linnaeus 1758 - Europe Pharmacis aemiliana Costantini 1911 - Italy Pharmacis anselminae Teobaldelli 1977- Italy Pharmacis bertrandi Le Cerf 1936 - France Pharmacis carna Denis & Schiffermüller 1775 - Central and Eastern Europe Pharmacis castillana Oberthür 1883 - Spain Pharmacis claudiae Kristal & Hirneisen 1994 - Italy Pharmacis fusconebulosa De Geer 1778 - Europe Pharmacis pyrenaicus Donzel 1838 - Pyrenees Phymatopus hecta Linnaeus 1758 - Central and no
Lepidoptera is an order of insects that includes butterflies and moths. About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 per cent of the total described species of living organisms, it is one of the most widespread and recognizable insect orders in the world. The Lepidoptera show many variations of the basic body structure that have evolved to gain advantages in lifestyle and distribution. Recent estimates suggest the order may have more species than earlier thought, is among the four most speciose orders, along with the Hymenoptera and Coleoptera. Lepidopteran species are characterized by more than three derived features; the most apparent is the presence of scales that cover the bodies, a proboscis. The scales are modified, flattened "hairs", give butterflies and moths their wide variety of colors and patterns. All species have some form of membranous wings, except for a few that have reduced wings or are wingless. Mating and the laying of eggs are carried out by adults near or on host plants for the larvae.
Like most other insects and moths are holometabolous, meaning they undergo complete metamorphosis. The larvae are called caterpillars, are different from their adult moth or butterfly forms, having a cylindrical body with a well-developed head, mandible mouth parts, three pairs of thoracic legs and from none up to five pairs of prolegs; as they grow, these larvae change in appearance, going through a series of stages called instars. Once matured, the larva develops into a pupa. A few butterflies and many moth species spin a silk case or cocoon prior to pupating, while others do not, instead going underground. A butterfly pupa, called a chrysalis, has a hard skin with no cocoon. Once the pupa has completed its metamorphosis, a sexually mature adult emerges; the Lepidoptera have, over millions of years, evolved a wide range of wing patterns and coloration ranging from drab moths akin to the related order Trichoptera, to the brightly colored and complex-patterned butterflies. Accordingly, this is the most recognized and popular of insect orders with many people involved in the observation, collection, rearing of, commerce in these insects.
A person who collects or studies this order is referred to as a lepidopterist. Butterflies and moths play an important role in the natural ecosystem as pollinators and as food in the food chain. In many species, the female may produce from 200 to 600 eggs, while in others, the number may approach 30,000 eggs in one day; the caterpillars hatching from these eggs can cause damage to large quantities of crops. Many moth and butterfly species are of economic interest by virtue of their role as pollinators, the silk they produce, or as pest species; the term was coined by Linnaeus in 1735 and is derived from Greek λεπίς, gen. λεπίδος and πτερόν. Sometimes, the term Rhopalocera is used for the clade of all butterfly species, derived from the Ancient Greek ῥόπαλον and κέρας meaning "club" and "horn" coming from the shape of the antennae of butterflies; the origins of the common names "butterfly" and "moth" are varied and obscure. The English word butterfly is with many variations in spelling. Other than that, the origin is unknown, although it could be derived from the pale yellow color of many species' wings suggesting the color of butter.
The species of Heterocera are called moths. The origins of the English word moth are more clear, deriving from the Old English moððe" from Common Germanic, its origins are related to Old English maða meaning "maggot" or from the root of "midge", which until the 16th century was used to indicate the larva in reference to devouring clothes. The etymological origins of the word "caterpillar", the larval form of butterflies and moths, are from the early 16th century, from Middle English catirpel, catirpeller an alteration of Old North French catepelose: cate, cat + pelose, hairy; the Lepidoptera are among the most successful groups of insects. They are found on all continents, except Antarctica, inhabit all terrestrial habitats ranging from desert to rainforest, from lowland grasslands to mountain plateaus, but always associated with higher plants angiosperms. Among the most northern dwelling species of butterflies and moths is the Arctic Apollo, found in the Arctic Circle in northeastern Yakutia, at an altitude of 1500 m above sea level.
In the Himalayas, various Apollo species such as Parnassius epaphus have been recorded to occur up to an altitude of 6,000 m above sea level. Some lepidopteran species exhibit symbiotic, phoretic, or parasitic lifestyles, inhabiting the bodies of organisms rather than the environment. Coprophagous pyralid moth species, called sloth moths, such as Bradipodicola hahneli and Cryptoses choloepi, are unusual in that they are found inhabiting the fur of sloths, mammals found in Central and South America. Two species of Tinea moths have been recorded as feeding on horny tissue and have been bred from the horns of cattle; the larva of Zenodochium coccivorella is an internal parasite of the coccid Kermes species. Many species have been recorded as breeding in natural materials or refuse such as owl pellets, bat caves, honeycombs or diseased fruit; as of 2007, there was 174,250 lepi
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