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
A sense is a physiological capacity of organisms that provides data for perception. The senses and their operation and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology, philosophy of perception; the nervous system has a specific sensory nervous system, a sense organ, or sensor, dedicated to each sense. Humans have a multitude of sensors. Sight, taste and touch are the five traditionally recognized senses; the ability to detect other stimuli beyond those governed by these most broadly recognized senses exists, these sensory modalities include temperature, kinesthetic sense, balance and various internal stimuli. However, what constitutes a sense is a matter of some debate, leading to difficulties in defining what a distinct sense is, where the borders lie between responses to related stimuli. Other animals have receptors to sense the world around them, with degrees of capability varying between species. Humans have a comparatively weak sense of smell and a stronger sense of sight relative to many other mammals while some animals may lack one or more of the traditional five senses.
Some animals may intake and interpret sensory stimuli in different ways. Some species of animals are able to sense the world in a way that humans cannot, with some species able to sense electrical and magnetic fields, detect water pressure and currents. A broadly acceptable definition of a sense would be "A system that consists of a group of sensory cell types that responds to a specific physical phenomenon, that corresponds to a particular group of regions within the brain where the signals are received and interpreted." There is no firm agreement as to the number of senses because of differing definitions of what constitutes a sense. The senses are divided into exteroceptive and interoceptive: Exteroceptive senses are senses that perceive the body's own position and state, known as proprioceptive senses. External senses include the traditional five: sight, touch and taste, as well as thermoception and an additional weak magnetoception. Proprioceptive senses include nociception. Interoceptive senses are senses.
Non-human animals may possess senses that are absent in humans, such as electroreception and detection of polarized light. In Buddhist philosophy, Ayatana or "sense-base" includes the mind as a sense organ, in addition to the traditional five; this addition to the acknowledged senses may arise from the psychological orientation involved in Buddhist thought and practice. The mind considered by itself is seen as the principal gateway to a different spectrum of phenomena that differ from the physical sense data; this way of viewing the human sense system indicates the importance of internal sources of sensation and perception that complements our experience of the external world. Sight or vision is the capability of the eye to focus and detect images of visible light on photoreceptors in the retina of each eye that generates electrical nerve impulses for varying colors and brightness. There are two types of photoreceptors: cones. Rods are sensitive to light but do not distinguish colors. Cones are less sensitive to dim light.
There is some disagreement as to whether this constitutes two or three senses. Neuroanatomists regard it as two senses, given that different receptors are responsible for the perception of color and brightness; some argue that stereopsis, the perception of depth using both eyes constitutes a sense, but it is regarded as a cognitive function of the visual cortex of the brain where patterns and objects in images are recognized and interpreted based on learned information. This is called visual memory; the inability to see is called blindness. Blindness may result from damage to the eyeball to the retina, damage to the optic nerve that connects each eye to the brain, and/or from stroke. Temporary or permanent blindness can be caused by medications. People who are blind from degradation or damage to the visual cortex, but still have functional eyes, are capable of some level of vision and reaction to visual stimuli but not a conscious perception. People with blindsight are not aware that they are reacting to visual sources, instead just unconsciously adapt their behavior to the stimulus.
On February 14, 2013 researchers developed a neural implant that gives rats the ability to sense infrared light which for the first time provides living creatures with new abilities, instead of replacing or augmenting existing abilities. Hearing or audition is the sense of sound perception. Hearing is all about vibration. Mechanoreceptors turn motion into electrical nerve pulses. Since sound is vibration, propagating through a medium such as air, the detection of these vibrations, the sense of the hearing, is a mechanical sense because these vibrations are mechanically conducted from the eardrum through a series of tiny bones to hair-like fibers in the inner
Archaeopriapulida is a group of priapulid-like worms known from Cambrian lagerstätte. The group is related to, similar to, the modern Priapulids, it is unclear. Despite a remarkable morphological similarity to their modern cousins, they fall outside of the priapulid crown group, not unambiguously represented in the fossil record until the Carboniferous, they are closely related or paraphyletic to the palaeoscolecids.
In Greek mythology, Priapus was a minor rustic fertility god, protector of livestock, fruit plants and male genitalia. Priapus is marked by his oversized, permanent erection, which gave rise to the medical term priapism, he became a popular figure in Roman erotic art and Latin literature, is the subject of the humorously obscene collection of verse called the Priapeia. Priapus was described as the son of Aphrodite by Dionysus, or the son of Dionysus and Chione as the father or son of Hermes, the son of Zeus or Pan, depending on the source. According to legend, Hera cursed him with inconvenient impotence and foul-mindedness while he was still in Aphrodite's womb, in revenge for the hero Paris having the temerity to judge Aphrodite more beautiful than Hera; the other gods refused to allow him to live on Mount Olympus and threw him down to Earth, leaving him on a hillside. He was found by shepherds and was brought up by them. Priapus joined Pan and the satyrs as a spirit of fertility and growth, though he was perennially frustrated by his impotence.
In a ribald anecdote told by Ovid, he attempted to rape the goddess Hestia but was thwarted by an ass, whose braying caused him to lose his erection at the critical moment and woke Hestia. The episode gave him a lasting hatred of asses and a willingness to see them destroyed in his honour; the emblem of his lustful nature was his large penis. Another myth states that he pursued the nymph Lotis until the gods took pity on her and turned her into a lotus plant; the first extant mention of Priapus is in the eponymous comedy Priapus, written in the 4th century BC by Xenarchus. Worshipped by Greek colonists in Lampsacus in Asia Minor, the cult of Priapus spread to mainland Greece and to Italy during the 3rd century BC. Lucian tells that in Bithynia Priapus was accounted as a warlike god, a rustic tutor to the infant Ares, "who taught him dancing first and war only afterwards," Karl Kerenyi observed. Arnobius is aware of the importance accorded Priapus in this region near the Hellespont. Pausanias notes: This god is worshipped where goats and sheep pasture or there are swarms of bees.
In antiquity, his worship meant little more than a cult of sophisticated pornography. Outside his "home" region in Asia Minor, Priapus was regarded as something of a joke by urban dwellers. However, he played a more important role in the countryside, he was regarded as the patron god of sailors and fishermen and others in need of good luck, his presence was believed to avert the evil eye. Priapus does not appear to have had an organized cult and was worshiped in gardens or homes, though there are attestations of temples dedicated to the god, his sacrificial animal was the ass, but agricultural offerings were very common. Long after the fall of Rome and the rise of Christianity, Priapus continued to be invoked as a symbol of health and fertility; the 13th century Lanercost Chronicle, a history of northern England and Scotland, records a "lay Cistercian brother" erecting a statue of Priapus in an attempt to end an outbreak of cattle disease. In the 1980s, D. F. Cassidy founded the St. Priapus Church as a modern church centred on worship of the phallus.
Priapus' iconic attribute was his priapism. He was represented in a variety of ways, most as a misshapen gnome-like figure with an enormous erect phallus. Statues of Priapus were common in ancient Rome, standing in gardens; the Athenians conflated Priapus with Hermes, the god of boundaries, depicted a hybrid deity with a winged helmet and huge erection. Another attribute of Priapus was the sickle which he carries in his right hand; this too was used to threaten thieves, doubtless with castration: Horace writes: Olim truncus eram ficulnus, inutile lignum,cum faber, incertus scamnum faceretne Priapum,maluit esse deum. deus inde ego, furum aviumquemaxima formido. "Once I was a trunk of fig, a useless piece of wood,when a carpenter, unsure whether he should make a bench or a Priapus,decided to make a god. So I am a god, of thieves and birdsa great scarer. In these, Priapus threatens sexual assault against potential thieves: Percidere, moneo. "I warn you, you will be screwed. "If a woman steals from me, or a man, or a boy, let the first give me her cunt, the second his head, the third his buttocks."per medios ibit pueros mediasque puellas mentula.
"My dick will go through the middle of boys and the middle of girls, but with bearded men it will aim only for the top."A number of Roman paintings of Priapus have survived. One of the most fam
Priapulus caudatus is a marine invertebrate belonging to the phylum Priapulida, the penis worms. It is a unsegmented worm which burrows in soft sediment on the seabed, it has a circumpolar distribution. Priapulus caudatus is one of only nineteen known species in the phylum Priapulida. French naturalist Jean-Baptiste Lamarck first described it in 1816. Phylogenetic studies have indicated that scalidophorans, to which priapulids belong, are a basal clade of ecdysozoans, thus a sister group to all other ecdysozoans, an assortment including nematodes and arthropods. Priapulids were abundant and widespread in the Early Cambrian period and their tunnelling activities in soft sediment created many trace fossils. P. caudatus is to be similar to the animals existing at that time. A cylindrical unsegmented worm, P. caudatus grows to a length of 15 cm. The body is divided into two distinct regions; the mouth is surrounded by seven rows, each with five teeth. The introvert is retractable into the trunk, a longer and broader region with transverse, ring-like markings.
It is terminated on the ventral side by a tail-like appendage. The front of the tail is sometimes obscured by a swelling of the trunk; the whole animal is a pinkish-brown colour. This species has a widespread, northerly circumpolar distribution, being present in New England, eastern Canada, Iceland and Scandinavia, as well as eastern Russia and western United States, sporadically further south, it is found in the subtidal zone. It is plentiful in Juneau, in Alaska, where a research study was undertaken in the 1980s. Here it occurred in the depth range of 16 to 187 m but elsewhere it has been found as deep as 7,500 m. P. caudatus has been little studied and its ecology is poorly known. It is believed to be carnivorous while other related species are thought to be deposit feeders and detritivores; the sexes are separate and fertilisation is external. Eggs are small and yolky, cleavage is holoblastic and equal; the larvae live on the seabed and have an introvert, a trunk enclosed by a thick cuticle into which the introvert can be retracted
The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period, 298.9 Mya. The name Carboniferous means "coal-bearing" and derives from the Latin words carbō and ferō, was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the modern'system' names to be employed, reflects the fact that many coal beds were formed globally during that time; the Carboniferous is treated in North America as two geological periods, the earlier Mississippian and the Pennsylvanian. Terrestrial animal life was well established by the Carboniferous period. Amphibians were the dominant land vertebrates, of which one branch would evolve into amniotes, the first terrestrial vertebrates. Arthropods were very common, many were much larger than those of today. Vast swaths of forest covered the land, which would be laid down and become the coal beds characteristic of the Carboniferous stratigraphy evident today.
The atmospheric content of oxygen reached its highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. The half of the period experienced glaciations, low sea level, mountain building as the continents collided to form Pangaea. A minor marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred at the end of the period, caused by climate change. In the United States the Carboniferous is broken into Mississippian and Pennsylvanian subperiods; the Mississippian is about twice as long as the Pennsylvanian, but due to the large thickness of coal-bearing deposits with Pennsylvanian ages in Europe and North America, the two subperiods were long thought to have been more or less equal in duration. In Europe the Lower Carboniferous sub-system is known as the Dinantian, comprising the Tournaisian and Visean Series, dated at 362.5-332.9 Ma, the Upper Carboniferous sub-system is known as the Silesian, comprising the Namurian and Stephanian Series, dated at 332.9-298.9 Ma.
The Silesian is contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, the Westphalian as the Coal Measures and Pennant Sandstone; the International Commission on Stratigraphy faunal stages from youngest to oldest, together with some of their regional subdivisions, are: A global drop in sea level at the end of the Devonian reversed early in the Carboniferous. There was a drop in south polar temperatures; these conditions had little effect in the deep tropics, where lush swamps to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major marine extinction, one that hit crinoids and ammonites hard; this sea level drop and the associated unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation.
The Carboniferous was a time of active mountain-building as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America; this continental collision resulted in the Hercynian orogeny in Europe, the Alleghenian orogeny in North America. In the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural Mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, South China continents were still separated from Laurasia; the Late Carboniferous Pangaea was shaped like an "O." There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, inside the "O" in the Carboniferous Pangaea. Other minor oceans were shrinking and closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean. Average global temperatures in the Early Carboniferous Period were high: 20 °C.
However, cooling during the Middle Carboniferous reduced average global temperatures to about 12 °C. Lack of growth rings of fossilized trees suggest a lack of seasons of a tropical climate. Glaciations in Gondwana, triggered by Gondwana's southward movement, continued into the Permian and because of the lack of clear markers and breaks, the deposits of this glacial period are referred to as Permo-Carboniferous in age; the cooling and drying of the climate led to the Carboniferous Rainforest Collapse during the late Carboniferous. Tropical rainforests fragmented and were devastated by climate change. Carboniferous rocks in Europe and eastern North America consist of a repeated sequence of limestone, sandstone and coal beds. In North America, the early Carboniferous is marine
Hydrogen sulfide is the chemical compound with the formula H2S. It is a colorless chalcogen hydride gas with the characteristic foul odor of rotten eggs, it is poisonous and flammable. Hydrogen sulfide is produced from the microbial breakdown of organic matter in the absence of oxygen gas, such as in swamps and sewers. H2S occurs in volcanic gases, natural gas, in some sources of well water; the human body uses it as a signaling molecule. Swedish chemist Carl Wilhelm Scheele is credited with having discovered hydrogen sulfide in 1777; the British English spelling of this compound is hydrogen sulphide, but this spelling is not recommended by the International Union of Pure and Applied Chemistry or the Royal Society of Chemistry. Hydrogen sulfide is denser than air. Hydrogen sulfide burns in oxygen with a blue flame to form sulfur water. In general, hydrogen sulfide acts as a reducing agent in the presence of base, which forms SH−. At high temperatures or in the presence of catalysts, sulfur dioxide reacts with hydrogen sulfide to form elemental sulfur and water.
This reaction is exploited in the Claus process, an important industrial method to dispose of hydrogen sulfide. Hydrogen sulfide is soluble in water and acts as a weak acid, giving the hydrosulfide ion HS−. Hydrogen sulfide and its solutions are colorless; when exposed to air, it oxidizes to form elemental sulfur, not soluble in water. The sulfide anion S2− is not formed in aqueous solution. Hydrogen sulfide reacts with metal ions to form metal sulfides, which are insoluble dark colored solids. Lead acetate paper is used to detect hydrogen sulfide because it converts to lead sulfide, black. Treating metal sulfides with strong acid liberates hydrogen sulfide. At pressures above 90 GPa, hydrogen sulfide becomes a metallic conductor of electricity; when cooled below a critical temperature this high-pressure phase exhibits superconductivity. The critical temperature increases with pressure. If hydrogen sulfide is pressurized at higher temperatures cooled, the critical temperature reaches 203 K, the highest accepted superconducting critical temperature as of 2015.
By substituting a small part of sulfur with phosphorus and using higher pressures, it has been predicted that it may be possible to raise the critical temperature to above 0 °C and achieve room-temperature superconductivity. Hydrogen sulfide is most obtained by its separation from sour gas, natural gas with high content of H2S, it can be produced by treating hydrogen with molten elemental sulfur at about 450 °C. Hydrocarbons can serve as a source of hydrogen in this process. Sulfate-reducing bacteria generate usable energy under low-oxygen conditions by using sulfates to oxidize organic compounds or hydrogen. A standard lab preparation is to treat ferrous sulfide with a strong acid in a Kipp generator: FeS + 2 HCl → FeCl2 + H2SFor use in qualitative inorganic analysis, thioacetamide is used to generate H2S: CH3CNH2 + H2O → CH3CNH2 + H2SMany metal and nonmetal sulfides, e.g. aluminium sulfide, phosphorus pentasulfide, silicon disulfide liberate hydrogen sulfide upon exposure to water: 6 H2O + Al2S3 → 3 H2S + 2 Al3This gas is produced by heating sulfur with solid organic compounds and by reducing sulfurated organic compounds with hydrogen.
Water heaters can aid the conversion of sulfate in water to hydrogen sulfide gas. This is due to providing a warm environment sustainable for sulfur bacteria and maintaining the reaction which interacts between sulfate in the water and the water heater anode, made from magnesium metal. Hydrogen sulfide can be generated in cells via non enzymatic pathway. H2S in the body acts as a gaseous signaling molecule, known to inhibit Complex IV of the mitochondrial electron transport chain which reduces ATP generation and biochemical activity within cells. Three enzymes are known to synthesize H2S: cystathionine γ-lyase, cystathionine β-synthetase and 3-mercaptopyruvate sulfurtransferase; these enzymes have been identified in a breadth of biological cells and tissues, their activity has been observed to be induced by a number of disease states. It is becoming clear that H2S is an important mediator of a wide range of cell functions in health and in disease. CBS and CSE are the main proponents of H2S biogenesis.
These enzymes are characterized by the transfer of a sulfur atom from methionine to serine to form a cysteine molecule. 3-MST contributes to hydrogen sulfide production by way of the cysteine catabolic pathway. Dietary amino acids, such as methionine and cysteine serve as the primary substrates for the transulfuration pathways and in the production of hydrogen sulfide. Hydrogen sulfide can be synthesized by non-enzymatic pathway, derived from proteins such as ferredoxins and Rieske proteins. H2S has been shown to be involved in physiological processes like vasoconstriction in animals, increasing seed germination and stress responses in plants. Hydrogen sulfide signaling is innately intertwined with physiological processes that are known to be moderated by reactive oxygen species and reactive nitrogen species. H2S has been shown to interact with NO resulting in severa