Animal

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, and 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 (110 ft) 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 often 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, arthropods, and molluscs—and the deuterostomes, containing the echinoderms and chordates (including the vertebrates). Life forms interpreted as early animals were present in the Ediacaran biota of the late Precambrian. Many modern animal phyla became clearly 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; these may have arisen from a single common ancestor that lived 650 million years ago.

Aristotle divided animals into those with blood and 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 (now synonymous with Animalia) 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, milk, and eggs; for materials, such as leather and wool; as pets; and as working animals for power and transport. Dogs have been used in hunting, while many terrestrial and aquatic animals are hunted for sport. Non-human animals have appeared in art from the earliest times and are featured in mythology and religion.

Animals
Temporal range: Cryogenian – present, 665–0Ma
EchinodermCnidariaBivalveTardigradeCrustaceanArachnidSpongeInsectMammalBryozoaAcanthocephalaFlatwormCephalopodAnnelidTunicateFishBirdPhoronidaAnimal diversity.png
Scientific classification
Domain: Eukaryota
(unranked): Unikonta
(unranked): Obazoa
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Linnaeus, 1758
Superphyla
Synonyms
  • Metazoa

Etymology

The word "animal" comes from the Latin animalis, meaning having breath, having soul or living being.[1] The biological definition includes all members of the kingdom Animalia.[2] In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals.[3][4][5][6]

Characteristics

Blastulation
Animals are unique in having the ball of cells of the early embryo (1) develop into a hollow ball or blastula (2).

Animals have several characteristics that set them apart from other living things. Animals are eukaryotic and multicellular,[7][8] unlike bacteria, which are prokaryotic, and unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients[9] animals are heterotrophic,[8][10] feeding on organic material and digesting it internally.[11] With very few exceptions, animals breathe oxygen and respire aerobically.[12] All animals are motile[13] (able to spontaneously move their bodies) during at least part of their life cycle, but some animals, such as sponges, corals, mussels, and barnacles, later become sessile. The blastula is a stage in embryonic development that is unique to most animals,[14] allowing cells to be differentiated into specialised tissues and organs.

Structure

All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins.[15] During development, the animal extracellular matrix forms a relatively 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, bones, and spicules.[16] In contrast, the cells of other multicellular organisms (primarily algae, plants, and fungi) are held in place by cell walls, and so develop by progressive growth.[17] Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, and desmosomes.[18]

With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues.[19] These include muscles, which enable locomotion, and nerve tissues, which transmit signals and coordinate the body. Typically, there is also an internal digestive chamber with either one opening (in Ctenophora, Cnidaria, and flatworms) or two openings (in most bilaterians).[20]

Reproduction and development

Odonata copulation
Sexual reproduction is nearly universal in animals, such as these dragonflies.

Nearly all animals make use of some form of sexual reproduction.[21] They produce haploid gametes by meiosis; the smaller, motile gametes are spermatozoa and the larger, non-motile gametes are ova.[22] These fuse to form zygotes,[23] which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, and develop into a new sponge.[24] In most other groups, the blastula undergoes more complicated rearrangement.[25] It first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm.[26] In most cases, a third germ layer, the mesoderm, also develops between them.[27] These germ layers then differentiate to form tissues and organs.[28]

Repeated instances of mating with a close relative during sexual reproduction generally leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits.[29][30] Animals have evolved numerous mechanisms for avoiding close inbreeding.[31] In some species, such as the splendid fairywren (Malurus splendens), females benefit by mating with multiple males, thus producing more offspring of higher genetic quality.[32]

Some animals are capable of asexual reproduction, which often results in a genetic clone of the parent. This may take place through fragmentation; budding, such as in Hydra and other cnidarians; or parthenogenesis, where fertile eggs are produced without mating, such as in aphids.[33][34]

Ecology

Ultramarine Flycatcher (Ficedula superciliaris) Naggar, Himachal Pradesh, 2013 (cropped)
Predators, such as this ultramarine flycatcher (Ficedula superciliaris), feed on other organisms.

Animals are categorised into ecological groups depending on how they obtain or consume organic material, including carnivores, herbivores, omnivores, detritivores,[35] and parasites.[36] Interactions between animals form complex food webs. In carnivorous or omnivorous species, predation is a consumer-resource interaction where a predator feeds on another organism (called its prey).[37] Selective pressures imposed on one another lead to an evolutionary arms race between predator and prey, resulting in various anti-predator adaptations.[38][39] Almost all multicellular predators are animals.[40] Some consumers use multiple methods; for example, in parasitoid wasps, the larvae feed on the hosts' living tissues, killing them in the process,[41] but the adults primarily consume nectar from flowers.[42] Other animals may have very specific feeding behaviours, such as hawksbill sea turtles that primarily eat sponges.[43]

Expl0072 - Flickr - NOAA Photo Library
Hydrothermal vent mussels and shrimps

Most animals rely on the energy produced by plants through photosynthesis. Herbivores eat plant material directly, while carnivores, and other animals on higher trophic levels, typically acquire energy (in the form of reduced carbon) by eating other animals. The carbohydrates, lipids, proteins, and other biomolecules are broken down to allow the animal to grow and to sustain biological processes such as locomotion.[44][45][46] Animals living close to hydrothermal vents and cold seeps on the dark sea floor do not depend on the energy of sunlight.[47] Rather, archaea and bacteria in these locations produce organic matter through chemosynthesis (by oxidizing inorganic compounds, such as methane) and form the base of the local food web.[48]

Animals originally evolved in the sea. Lineages of arthropods colonised land around the same time as land plants, probably between 510–471 million years ago during the Late Cambrian or Early Ordovician.[49] Vertebrates such as the lobe-finned fish Tiktaalik started to move on to land in the late Devonian, about 375 million years ago.[50][51] Animals occupy virtually all of earth's habitats and microhabitats, including salt water, hydrothermal vents, fresh water, hot springs, swamps, forests, pastures, deserts, air, and the interiors of animals, plants, fungi and rocks.[52] Animals are however not particularly heat tolerant; very few of them can survive at constant temperatures above 50 °C (122 °F).[53] Only very few species of animals (mostly nematodes) inhabit the most extreme cold deserts of continental Antarctica.[54]

Diversity

Anim1754 - Flickr - NOAA Photo Library (1)
The blue whale is the largest animal that has ever lived.

Largest and smallest

The blue whale (Balaenoptera musculus) is the largest animal that has ever lived, weighing up to 190 metric tonnes and measuring up to 33.6 metres (110 ft) long.[55][56][57] The largest extant terrestrial animal is the African bush elephant (Loxodonta africana), weighing up to 12.25 tonnes[55] and measuring up to 10.67 metres (35.0 ft) long.[55] The largest terrestrial animals that ever lived were titanosaur sauropod dinosaurs such as Argentinosaurus, which may have weighed as much as 73 tonnes.[58] Several animals are microscopic; some Myxozoa (obligate parasites within the Cnidaria) never grow larger than 20 µm,[59] and one of the smallest species (Myxobolus shekel) is no more than 8.5 µm when fully grown.[60]

Numbers and habitats

The following table lists estimated numbers of described extant species for the animal groups with the largest numbers of species,[61] along with their principal habitats (terrestrial, fresh water,[62] and marine),[63] and free-living or parasitic ways of life.[64] Species estimates shown here are based on numbers described scientifically; much larger estimates have been calculated based on various means of prediction, and these can vary wildly. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million.[65] Using patterns within the taxonomic hierarchy, the total number of animal species—including those not yet described—was calculated to be about 7.77 million in 2011.[66][67][a]

Phylum Example No. of
Species
Land Sea Fresh
water
Free-
living
Parasitic
Annelids Nerr0328 17,000[61] Yes (soil)[63] Yes[63] 1,750[62] Yes 400[64]
Arthropods European wasp white bg02 1,257,000[61] 1,000,000
(insects)[69]
>40,000
(Malac-
ostraca)[70]
94,000[62] Yes[63] >45,000[b][64]
Bryozoa Bryozoan at Ponta do Ouro, Mozambique (6654415783) 6,000[61] Yes[63] 60-80[62] Yes
Chordates Lithobates pipiens 65,000[61]
45,000[71]

23,000[71]

13,000[71]
18,000[62]
9,000[71]
Yes 40
(catfish)[72][64]
Cnidaria FFS Table bottom 16,000[61] Yes[63] Yes (few)[63] Yes[63] >1,350
(Myxozoa)[64]
Echinoderms Starfish, Caswell Bay - geograph.org.uk - 409413 7,500[61] 7,500[61] Yes[63]
Molluscs Grapevinesnail 01 85,000[61]
107,000[73]

35,000[73]

60,000[73]
5,000[62]
12,000[73]
Yes[63] >5,600[64]
Nematodes CelegansGoldsteinLabUNC 25,000[61] Yes (soil)[63] 4,000[65] 2,000[62] 11,000[65] 14,000[65]
Platyhelminthes Pseudoceros dimidiatus 29,500[61] Yes[74] Yes[63] 1,300[62] Yes[63] >40,000[64]
Rotifers 20090730 020239 Rotifer 2,000[61] >400[75] 2,000[62] Yes
Sponges A colourful Sponge on the Fathom 10,800[61] Yes[63] 200-300[62] Yes Yes[76]
Total number of described species as of 2013: 1,525,728[61]

Evolutionary origin

DickinsoniaCostata
Dickinsonia costata from the Ediacaran biota (c. 635–542 MYA) is one of the earliest animal species known.[77]

The first fossils that might represent animals appear in the 665-million-year-old rocks of the Trezona Formation of South Australia. These fossils are interpreted as most probably being early sponges.[78]

The oldest animals are found in the Ediacaran biota, towards the end of the Precambrian, around 610 million years ago. It had long been doubtful whether these included animals,[79][80][81] but the discovery of the animal lipid cholesterol in fossils of Dickinsonia establishes that these were indeed animals.[77] Animals are thought to have originated under low-oxygen conditions, suggesting that they were capable of living entirely by anaerobic respiration, but as they became specialized for aerobic metabolism they became fully dependent on oxygen in their environments.[82]

Anomalocaris NT small
Anomalocaris canadensis is one of the many animal species that emerged in the Cambrian explosion, starting some 542 million years ago, and found in the fossil beds of the Burgess shale.

Many animal phyla first appear in the fossil record during the Cambrian explosion, starting about 542 million years ago, in beds such as the Burgess shale. Extant phyla in these rocks include molluscs, brachiopods, onychophorans, tardigrades, arthropods, echinoderms and hemichordates, along with numerous now-extinct forms such as the predatory Anomalocaris. The apparent suddenness of the event may however be an artefact of the fossil record, rather than showing that all these animals appeared simultaneously.[83][84][85][86]

Some palaeontologists have suggested that animals appeared much earlier than the Cambrian explosion, possibly as early as 1 billion years ago.[87] Trace fossils such as tracks and burrows found in the Tonian period may indicate the presence of triploblastic worm-like animals, roughly as large (about 5 mm wide) and complex as earthworms.[88] However, similar tracks are produced today by the giant single-celled protist Gromia sphaerica, so the Tonian trace fossils may not indicate early animal evolution.[89][90] Around the same time, another line of evidence may indicate the appearance of grazing animals: the layered mats of microorganisms called stromatolites decreased in diversity, perhaps due to grazing.[91]

Phylogeny

Animals are monophyletic, meaning they are derived from a common ancestor. Animals are sister to the Choanoflagellata, with which they form the Choanozoa.[92] The most basal animals, the Porifera, Ctenophora, Cnidaria, and Placozoa, have body plans that lack bilateral symmetry. Their relationships are still disputed; the sister group to all other animals could be the Porifera or the Ctenophora, which like the Porifera lack hox genes, important in body plan development.[93]

These genes are found in the Placozoa[94][95] and the higher animals, the Bilateria.[96][97] 6,331 groups of genes common to all living animals have been identified; these may have arisen from a single common ancestor that lived 650 million years ago in the Precambrian. 25 of these are novel core gene groups, found only in animals; of those, 8 are for essential components of the Wnt and TGF-beta signalling pathways which may have enabled animals to become multicellular by providing a pattern for the body's system of axes (in three dimensions), and another 7 are for transcription factors including homeodomain proteins involved in the control of development.[98][99]

The phylogenetic tree (of major lineages only) indicates approximately how many millions of years ago (mya) the lineages split.[100][101][102][103][104]

Choanozoa

Choanoflagellata Desmarella moniliformis

Animalia

Porifera Reef3859 - Flickr - NOAA Photo Library

Eumetazoa

Ctenophora Comb jelly

ParaHoxozoa

Placozoa Trichoplax adhaerens photograph

Cnidaria Cauliflour Jellyfish, Cephea cephea at Marsa Shouna, Red Sea, Egypt SCUBA

Bilateria

Xenacoelomorpha Proporus sp

Nephrozoa
Deuterostomia

Chordata Cyprinus carpio3

Ambulacraria Portugal 20140812-DSC01434 (21371237591)

Protostomia
Ecdysozoa

Scalidophora

Arthropoda and allies Long nosed weevil edit

Nematoda and allies CelegansGoldsteinLabUNC

>529 mya
Spiralia
Gnathifera

Rotifera and allies Bdelloid Rotifer (cropped).jpg

Chaetognatha Chaetoblack

Platytrochozoa

Platyhelminthes and allies Sorocelis reticulosa

Lophotrochozoa

Mollusca and allies Grapevinesnail 01

Annelida and allies Polychaeta (no)

550 mya
580 mya
610 mya
650 mya
Triploblasts
680 mya
760 mya
950 mya

Non-bilaterian animals

Elephant-ear-sponge
Non-bilaterians include sponges (centre) and corals (background).

Several animal phyla lack bilateral symmetry. Among these, the sponges (Porifera) probably diverged first, representing the oldest animal phylum.[105] Sponges lack the complex organization found in most other animal phyla;[106] their cells are differentiated, but in most cases not organised into distinct tissues.[107] They typically feed by drawing in water through pores.[108]

The Ctenophora (comb jellies) and Cnidaria (which includes jellyfish, sea anemones, and corals) are radially symmetric and have digestive chambers with a single opening, which serves as both mouth and anus.[109] Animals in both phyla have distinct tissues, but these are not organised into organs.[110] They are diploblastic, having only two main germ layers, ectoderm and endoderm.[111] The tiny placozoans are similar, but they do not have a permanent digestive chamber.[112][113]

Bilaterian animals

Bilaterian body plan
Idealised bilaterian body plan.[c] With an elongated body and a direction of movement the animal has head and tail ends. Sense organs and mouth form the basis of the head. Opposed circular and longitudinal muscles enable peristaltic motion.

The remaining animals, the great majority—comprising some 29 phyla and over a million species—form a clade, the Bilateria. The body is triploblastic, with three well-developed germ layers, and their tissues form distinct organs. The digestive chamber has two openings, a mouth and an anus, and there is an internal body cavity, a coelom or pseudocoelom. Animals with this bilaterally symmetric body plan and a tendency to move in one direction have a head end (anterior) and a tail end (posterior) as well as a back (dorsal) and a belly (ventral); therefore they also have a left side and a right side.[114][115]

Having a front end means that this part of the body encounters stimuli, such as food, favouring cephalisation, the development of a head with sense organs and a mouth. Many bilaterians have a combination of circular muscles that constrict the body, making it longer, and an opposing set of longitudinal muscles, that shorten the body;[115] these enable soft-bodied animals with a hydrostatic skeleton to move by peristalsis.[116] They also have a gut that extends through the basically cylindrical body from mouth to anus. Many bilaterian phyla have primary larvae which swim with cilia and have an apical organ containing sensory cells. However, there are exceptions to each of these characteristics; for example, adult echinoderms are radially symmetric (unlike their larvae), while some parasitic worms have extremely simplified body structures.[114][115]

Genetic studies have considerably changed zoologists' understanding of the relationships within the Bilateria. Most appear to belong to two major lineages, the protostomes and the deuterostomes.[117] The basalmost bilaterians are the Xenacoelomorpha.[118][119][120]

Protostomes and deuterostomes

Protovsdeuterostomes
The bilaterian gut develops in two ways. In many protostomes, the blastopore develops into the mouth, while in deuterostomes it becomes the anus.

Protostomes and deuterostomes differ in several ways. Early in development, deuterostome embryos undergo radial cleavage during cell division, while many protostomes (the Spiralia) undergo spiral cleavage.[121] Animals from both groups possess a complete digestive tract, but in protostomes the first opening of the embryonic gut develops into the mouth, and the anus forms secondarily. In deuterostomes, the anus forms first while the mouth develops secondarily.[122][123] Most protostomes have schizocoelous development, where cells simply fill in the interior of the gastrula to form the mesoderm. In deuterostomes, the mesoderm forms by enterocoelic pouching, through invagination of the endoderm.[124]

The main deuterostome phyla are the Echinodermata and the Chordata.[125] Echinoderms are exclusively marine and include starfish, sea urchins, and sea cucumbers.[126] The chordates are dominated by the vertebrates (animals with backbones),[127] which consist of fishes, amphibians, reptiles, birds, and mammals.[128] The deuterostomes also include the Hemichordata (acorn worms).[129][130]

Anax Imperator 2(loz)
Ecdysis: a dragonfly has emerged from its dry exuviae and is expanding its wings. Like other arthropods, its body is divided into segments.

The Ecdysozoa are protostomes, named after their shared trait of ecdysis, growth by moulting.[131] They include the largest animal phylum, the Arthropoda, which contains insects, spiders, crabs, and their kin. All of these have a body divided into repeating segments, typically with paired appendages. Two smaller phyla, the Onychophora and Tardigrada, are close relatives of the arthropods and share these traits. The ecdysozoans also include the Nematoda or roundworms, perhaps the second largest animal phylum. Roundworms are typically microscopic, and occur in nearly every environment where there is water;[132] some are important parasites.[133] Smaller phyla related to them are the Nematomorpha or horsehair worms, and the Kinorhyncha, Priapulida, and Loricifera. These groups have a reduced coelom, called a pseudocoelom.[134]

Spiral cleavage in Trochus
Spiral cleavage in a sea snail embryo

The Spiralia are a large group of protostomes that develop by spiral cleavage in the early embryo.[135] The Spiralia's phylogeny has been disputed, but it contains a large clade, the superphylum Lophotrochozoa, and smaller groups of phyla such as the Rouphozoa which includes the gastrotrichs and the flatworms. All of these are grouped as the Platytrochozoa, which has a sister group, the Gnathifera, which includes the rotifers.[136][137]

The Lophotrochozoa includes the molluscs, annelids, brachiopods, nemerteans, bryozoa and entoprocts.[136][138][139] The molluscs, the second-largest animal phylum by number of described species, includes snails, clams, and squids, while the annelids are the segmented worms, such as earthworms, lugworms, and leeches. These two groups have long been considered close relatives because they share trochophore larvae.[140][141]

History of classification

Jean-Baptiste de Lamarck
Jean-Baptiste de Lamarck led the creation of a modern classification of invertebrates, breaking up Linnaeus's "Vermes" into 9 phyla by 1809.[142]

In the classical era, Aristotle divided animals,[d] based on his own observations, into those with blood (roughly, the vertebrates) and those without. The animals were then arranged on a scale from man (with blood, 2 legs, rational soul) down through the live-bearing tetrapods (with blood, 4 legs, sensitive soul) and other groups such as crustaceans (no blood, many legs, sensitive soul) down to spontaneously-generating creatures like sponges (no blood, no legs, vegetable soul). Aristotle was uncertain whether sponges were animals, which in his system ought to have sensation, appetite, and locomotion, or plants, which did not: he knew that sponges could sense touch, and would contract if about to be pulled off their rocks, but that they were rooted like plants and never moved about.[143]

In 1758, Carl Linnaeus created the first hierarchical classification in his Systema Naturae.[144] In his original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, the Chordata, while his Insecta (which included the crustaceans and arachnids) and Vermes have been renamed or broken up. The process was begun in 1793 by Jean-Baptiste de Lamarck, who called the Vermes une espèce de chaos (a chaotic mess)[e] and split the group into three new phyla, worms, echinoderms, and polyps (which contained corals and jellyfish). By 1809, in his Philosophie Zoologique, Lamarck had created 9 phyla apart from vertebrates (where he still had 4 phyla: mammals, birds, reptiles, and fish) and molluscs, namely cirripedes, annelids, crustaceans, arachnids, insects, worms, radiates, polyps, and infusorians.[142]

In his 1817 Le Règne Animal, Georges Cuvier used comparative anatomy to group the animals into four embranchements ("branches" with different body plans, roughly corresponding to phyla), namely vertebrates, molluscs, articulated animals (arthropods and annelids), and zoophytes (radiata) (echinoderms, cnidaria and other forms).[146] This division into four was followed by the embryologist Karl Ernst von Baer in 1828, the zoologist Louis Agassiz in 1857, and the comparative anatomist Richard Owen in 1860.[147]

In 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms: Metazoa (multicellular animals, with five phyla: coelenterates, echinoderms, articulates, molluscs, and vertebrates) and Protozoa (single-celled animals), including a sixth animal phylum, sponges.[148][147] The protozoa were later moved to the former kingdom Protista, leaving only the Metazoa as a synonym of Animalia.[149]

In human culture

Carni bovine macellate
Sides of beef in a slaughterhouse

The human population exploits a large number of other animal species for food, both of domesticated livestock species in animal husbandry and, mainly at sea, by hunting wild species.[150][151] Marine fish of many species are caught commercially for food. A smaller number of species are farmed commercially.[150][152][153] Invertebrates including cephalopods, crustaceans, and bivalve or gastropod molluscs are hunted or farmed for food.[154] Chickens, cattle, sheep, pigs and other animals are raised as livestock for meat across the world.[151][155][156] Animal fibres such as wool are used to make textiles, while animal sinews have been used as lashings and bindings, and leather is widely used to make shoes and other items. Animals have been hunted and farmed for their fur to make items such as coats and hats.[157][158] Dyestuffs including carmine (cochineal),[159][160] shellac,[161][162] and kermes[163][164] have been made from the bodies of insects. Working animals including cattle and horses have been used for work and transport from the first days of agriculture.[165]

Animals such as the fruit fly Drosophila melanogaster serve a major role in science as experimental models.[166][167][168][169] Animals have been used to create vaccines since their discovery in the 18th century.[170] Some medicines such as the cancer drug Yondelis are based on toxins or other molecules of animal origin.[171]

Hebbuz
A gun dog retrieving a duck during a hunt

People have used hunting dogs to help chase down and retrieve animals,[172] and birds of prey to catch birds and mammals,[173] while tethered cormorants have been used to catch fish.[174] Poison dart frogs have been used to poison the tips of blowpipe darts.[175][176] A wide variety of animals are kept as pets, from invertebrates such as tarantulas and octopuses, insects including praying mantises,[177] reptiles such as snakes and chameleons,[178] and birds including canaries, parakeets, and parrots[179] all finding a place. However, the most kept pet species are mammals, namely dogs, cats, and rabbits.[180][181][182] There is a tension between the role of animals as companions to humans, and their existence as individuals with rights of their own.[183] A wide variety of terrestrial and aquatic animals are hunted for sport.[184]

Alexander Coosemans - Still Life with Lobster and Oysters
Artistic vision: Still Life with Lobster and Oysters by Alexander Coosemans, c. 1660

Animals have been the subjects of art from the earliest times, both historical, as in Ancient Egypt, and prehistoric, as in the cave paintings at Lascaux. Major animal paintings include Albrecht Dürer's 1515 The Rhinoceros, and George Stubbs's c. 1762 horse portrait Whistlejacket.[185] Insects, birds and mammals play roles in literature and film,[186] such as in giant bug movies.[187][188][189] Animals including insects[190] and mammals[191] feature in mythology and religion. In both Japan and Europe, a butterfly was seen as the personification of a person's soul,[190][192][193] while the scarab beetle was sacred in ancient Egypt.[194] Among the mammals, cattle,[195] deer,[191] horses,[196] lions,[197] bats,[198] bears,[199] and wolves[200] are the subjects of myths and worship. The signs of the Western and Chinese zodiacs are based on animals.[201][202]

See also

Notes

  1. ^ The application of DNA barcoding to taxonomy further complicates this; a 2016 barcoding analysis estimated a total count of nearly 100,000 insect species for Canada alone, and extrapolated that the global insect fauna must be in excess of 10 million species, of which nearly 2 million are in a single fly family known as gall midges (Cecidomyiidae).[68]
  2. ^ Not including parasitoids.[64]
  3. ^ Compare File:Annelid redone w white background.svg for a more specific and detailed model of a particular phylum with this general body plan.
  4. ^ In his History of Animals and Parts of Animals.
  5. ^ The prefix une espèce de is pejorative.[145]

References

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External links

Animal Crossing

Animal Crossing is a social simulation video game series developed and published by Nintendo and was created by Katsuya Eguchi. In Animal Crossing, the player character is a human who lives in a village inhabited by anthropomorphic animals, carrying out various activities including fishing, bug catching, fossil hunting, etc. The series is notable for its open-ended gameplay and extensive use of the video game consoles' internal clock and calendar to simulate real passage of time.

Four Animal Crossing games have been released worldwide, one each for the Nintendo 64/IQue Player (enhanced and reissued for the GameCube) Nintendo DS, Wii, and the Nintendo 3DS. A fifth game, for the Nintendo Switch, is scheduled for a 2020 release. The series has been both critically and commercially successful and has sold over 30 million units worldwide. Three spin-off games have also been released: Animal Crossing: Happy Home Designer for Nintendo 3DS, Animal Crossing: Amiibo Festival for Wii U, and Animal Crossing: Pocket Camp for mobile devices.

Animal Farm

Animal Farm is an allegorical novella by George Orwell, first published in England on 17 August 1945. According to Orwell, the fable reflects events leading up to the Russian Revolution of 1917 and then on into the Stalinist era of the Soviet Union. Orwell, a democratic socialist, was a critic of Joseph Stalin and hostile to Moscow-directed Stalinism, an attitude that was critically shaped by his experiences during the Spanish Civil War. The Soviet Union, he believed, had become a brutal dictatorship, built upon a cult of personality and enforced by a reign of terror. In a letter to Yvonne Davet, Orwell described Animal Farm as a satirical tale against Stalin ("un conte satirique contre Staline"), and in his essay "Why I Write" (1946), wrote that Animal Farm was the first book in which he tried, with full consciousness of what he was doing, "to fuse political purpose and artistic purpose into one whole".The original title was Animal Farm: A Fairy Story, but U.S. publishers dropped the subtitle when it was published in 1946, and only one of the translations during Orwell's lifetime kept it. Other titular variations include subtitles like "A Satire" and "A Contemporary Satire". Orwell suggested the title Union des républiques socialistes animales for the French translation, which abbreviates to URSA, the Latin word for "bear", a symbol of Russia. It also played on the French name of the Soviet Union, Union des républiques socialistes soviétiques.Orwell wrote the book between November 1943 and February 1944, when the UK was in its wartime alliance with the Soviet Union against Nazi Germany and the British people and intelligentsia held Stalin in high esteem, a phenomenon Orwell hated. The manuscript was initially rejected by a number of British and American publishers, including one of Orwell's own, Victor Gollancz, which delayed its publication. It became a great commercial success when it did appear partly because international relations were transformed as the wartime alliance gave way to the Cold War.Time magazine chose the book as one of the 100 best English-language novels (1923 to 2005); it also featured at number 31 on the Modern Library List of Best 20th-Century Novels. It won a Retrospective Hugo Award in 1996 and is included in the Great Books of the Western World selection.

Animal husbandry

Animal husbandry is the branch of agriculture concerned with animals that are raised for meat, fibre, milk, eggs, or other products. It includes day-to-day care, selective breeding and the raising of livestock.

Husbandry has a long history, starting with the Neolithic revolution when animals were first domesticated, from around 13,000 BC onwards, antedating farming of the first crops. By the time of early civilisations such as ancient Egypt, cattle, sheep, goats and pigs were being raised on farms.

Major changes took place in the Columbian Exchange when Old World livestock were brought to the New World, and then in the British Agricultural Revolution of the 18th century, when livestock breeds like the Dishley Longhorn cattle and Lincoln Longwool sheep were rapidly improved by agriculturalists such as Robert Bakewell to yield more meat, milk, and wool.

A wide range of other species such as horse, water buffalo, llama, rabbit and guinea pig are used as livestock in some parts of the world. Insect farming, as well as aquaculture of fish, molluscs, and crustaceans, is widespread.

Modern animal husbandry relies on production systems adapted to the type of land available. Subsistence farming is being superseded by intensive animal farming in the more developed parts of the world, where for example beef cattle are kept in high density feedlots, and thousands of chickens may be raised in broiler houses or batteries. On poorer soil such as in uplands, animals are often kept more extensively, and may be allowed to roam widely, foraging for themselves.

Most livestock are herbivores, except for pigs and chickens which are omnivores. Ruminants like cattle and sheep are adapted to feed on grass; they can forage outdoors, or may be fed entirely or in part on rations richer in energy and protein, such as pelleted cereals. Pigs and poultry cannot digest the cellulose in forage, and require cereals and other high-energy foods.

Animal rights

Animal rights is the idea in which some, or all, non-human animals are entitled to the possession of their own existence and that their most basic interests—such as the need to avoid suffering—should be afforded the same consideration as similar interests of human beings.Its advocates oppose the assignment of moral value and fundamental protections on the basis of species membership alone—an idea known since 1970 as speciesism, when the term was coined by Richard D. Ryder—arguing that it is a prejudice as irrational as any other. They maintain that animals should no longer be viewed as property or used as food, clothing, research subjects, entertainment, or beasts of burden. Multiple cultural traditions around the world such as Jainism, Taoism, Hinduism, Buddhism and Animism also espouse some forms of animal rights.

In parallel to the debate about moral rights, animal law is now widely taught in law schools in North America, and several prominent legal scholars support the extension of basic legal rights and personhood to at least some animals. The animals most often considered in arguments for personhood are bonobos and chimpanzees. This is supported by some animal rights academics because it would break through the species barrier, but opposed by others because it predicates moral value on mental complexity, rather than on sentience alone.Critics of animal rights argue that nonhuman animals are unable to enter into a social contract, and thus cannot be possessors of rights, a view summed up by the philosopher Roger Scruton, who writes that only humans have duties, and therefore only humans have rights. Another argument, associated with the utilitarian tradition, is that animals may be used as resources so long as there is no unnecessary suffering; they may have some moral standing, but they are inferior in status to human beings, and any interests they have may be overridden, though what counts as "necessary" suffering or a legitimate sacrifice of interests varies considerably. Certain forms of animal rights activism, such as the destruction of fur farms and animal laboratories by the Animal Liberation Front, have also attracted criticism, including from within the animal rights movement itself, as well as prompted reaction from the U.S. Congress with the enactment of laws allowing these activities to be prosecuted as terrorism, including the Animal Enterprise Terrorism Act.

Animal testing

Animal testing, also known as animal experimentation, animal research and in vivo testing, is the use of non-human animals in experiments that seek to control the variables that affect the behavior or biological system under study. This approach can be contrasted with field studies in which animals are observed in their natural environments or habitats. Experimental research with animals is usually conducted in universities, medical schools, pharmaceutical companies, defense establishments and commercial facilities that provide animal-testing services to industry. The focus of animal testing varies on a continuum from pure research, focusing on developing fundamental knowledge of an organism, to applied research, which may focus on answering some question of great practical importance, such as finding a cure for a disease. Examples of applied research include testing disease treatments, breeding, defense research and toxicology, including cosmetics testing. In education, animal testing is sometimes a component of biology or psychology courses. The practice is regulated to varying degrees in different countries.

It is estimated that the annual use of vertebrate animals—from zebrafish to non-human primates—ranges from tens to more than 100 million. In the European Union, vertebrate species represent 93% of animals used in research, and 11.5 million animals were used there in 2011. By one estimate the number of mice and rats used in the United States alone in 2001 was 80 million. Mice, rats, fish, amphibians and reptiles together account for over 85% of research animals.Most animals are euthanized after being used in an experiment. Sources of laboratory animals vary between countries and species; most animals are purpose-bred, while a minority are caught in the wild or supplied by dealers who obtain them from auctions and pounds. Supporters of the use of animals in experiments, such as the British Royal Society, argue that virtually every medical achievement in the 20th century relied on the use of animals in some way. The Institute for Laboratory Animal Research of the United States National Academy of Sciences has argued that animal research cannot be replaced by even sophisticated computer models, which are unable to deal with the extremely complex interactions between molecules, cells, tissues, organs, organisms and the environment. Animal rights organizations—such as PETA and BUAV—question the need for and legitimacy of animal testing, arguing that it is cruel and poorly regulated, that medical progress is actually held back by misleading animal models that cannot reliably predict effects in humans, that some of the tests are outdated, that the costs outweigh the benefits, or that animals have the intrinsic right not to be used or harmed in experimentation.

Anthropomorphism

Anthropomorphism is the attribution of human traits, emotions, or intentions to non-human entities. It is considered to be an innate tendency of human psychology.Personification is the related attribution of human form and characteristics to abstract concepts such as nations, emotions, and natural forces, such as seasons and weather.

Both have ancient roots as storytelling and artistic devices, and most cultures have traditional fables with anthropomorphized animals as characters. People have also routinely attributed human emotions and behavioral traits to wild as well as domesticated animals.

Carnivore

A carnivore , meaning "meat eater" (Latin, caro, genitive carnis, meaning "meat" or "flesh" and vorare meaning "to devour"), is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging. Animals that depend solely on animal flesh for their nutrient requirements are called obligate carnivores while those that also consume non-animal food are called facultative carnivores. Omnivores also consume both animal and non-animal food, and, apart from the more general definition, there is no clearly defined ratio of plant to animal material that would distinguish a facultative carnivore from an omnivore. A carnivore at the top of the food chain, not preyed upon by other animals, is termed an apex predator.

"Carnivore" also may refer to the mammalian order Carnivora, but this is somewhat misleading: many, but not all, Carnivora are meat eaters, and even fewer are true obligate carnivores (see below). For example, while the Arctic polar bear eats meat almost exclusively (more than 90% of its diet is meat), most species of bears are actually omnivorous, and the giant panda is exclusively herbivorous. There are also many carnivorous species that are not members of Carnivora.

Outside the animal kingdom, there are several genera containing carnivorous plants (predominantly insectivores) and several phyla containing carnivorous fungi (preying mostly on microscopic invertebrates such as nematodes, amoebae and springtails).

Carnivores are sometimes characterized by their type of prey. For example, animals that eat mainly insects and similar invertebrates are called insectivores, while those that eat mainly fish are called piscivores. The first tetrapods, or land-dwelling vertebrates, were piscivorous amphibians known as labyrinthodonts. They gave rise to insectivorous vertebrates and, later, to predators of other tetrapods.Carnivores may alternatively be classified according to the percentage of meat in their diet. The diet of a hypercarnivore consists of more than 70% meat, that of a mesocarnivore 30–70%, and that of a hypocarnivore less than 30%, with the balance consisting of non-animal foods such as fruits, other plant material, or fungi.

Cattle

Cattle—colloquially cows—are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos taurus.

Cattle are commonly raised as livestock for meat (beef or veal, see beef cattle), for milk (see dairy cattle), and for hides, which are used to make leather. They are used as riding animals and draft animals (oxen or bullocks, which pull carts, plows and other implements). Another product of cattle is dung, which can be used to create manure or fuel. In some regions, such as parts of India, cattle have significant religious meaning. Cattle, mostly small breeds such as the Miniature Zebu, are also kept as pets.

Around 10,500 years ago, cattle were domesticated from as few as 80 progenitors in central Anatolia, the Levant and Western Iran. According to an estimate from 2011, there are 1.4 billion cattle in the world. In 2009, cattle became one of the first livestock animals to have a fully mapped genome. Some consider cattle the oldest form of wealth, and cattle raiding consequently one of the earliest forms of theft.

Cruelty to animals

Cruelty to animals, also called animal abuse, animal neglect or animal cruelty, is the infliction by omission (animal neglect) or by commission by humans of suffering or harm upon any non-human. More narrowly, it can be the causing of harm or suffering for specific achievement, such as killing animals for food, for their fur or even their tusks; opinions differ about the extent of cruelty associated with a given method of slaughter. Cruelty to animals sometimes encompasses inflicting harm or suffering as an end in itself, defined as zoosadism. With approximately 65 billion animals killed annually for food, farm animals are the most numerous animals subjected to cruelty.Divergent approaches to laws concerning animal cruelty occur in different jurisdictions throughout the world. For example, some laws govern methods of killing animals for food, clothing, or other products, and other laws concern the keeping of animals for entertainment, education, research, or pets. There are a number of conceptual approaches to the issue of cruelty to animals.

For example, the animal welfare position holds that there is nothing inherently wrong with using animals for human purposes, such as food, clothing, entertainment, fun and research, but that it should be done in a way that minimizes unnecessary pain and suffering, sometimes referred to as "humane" treatment.

Utilitarian advocates argue from the position of costs and benefits and vary in their conclusions as to the allowable treatment of animals. Some utilitarians argue for a weaker approach which is closer to the animal welfare position, whereas others argue for a position that is similar to animal rights. Animal rights theorists criticize these positions, arguing that the words "unnecessary" and "humane" are subject to widely differing interpretations, and that animals have basic rights. They say that the only way to ensure protection for animals is to end their status as property and to ensure that they are never used as a substance or as a non-living thing.

Dog

The domestic dog (Canis lupus familiaris when considered a subspecies of the wolf or Canis familiaris when considered a distinct species) is a member of the genus Canis (canines), which forms part of the wolf-like canids, and is the most widely abundant terrestrial carnivore. The dog and the extant gray wolf are sister taxa as modern wolves are not closely related to the wolves that were first domesticated, which implies that the direct ancestor of the dog is extinct. The dog was the first species to be domesticated and has been selectively bred over millennia for various behaviors, sensory capabilities, and physical attributes.Their long association with humans has led dogs to be uniquely attuned to human behavior and they are able to thrive on a starch-rich diet that would be inadequate for other canid species. Dogs vary widely in shape, size and colors. They perform many roles for humans, such as hunting, herding, pulling loads, protection, assisting police and military, companionship and, more recently, aiding disabled people and therapeutic roles. This influence on human society has given them the sobriquet of "man's best friend".

Feces

Feces (or faeces) are the solid or semisolid remains of food that could not be digested in the small intestine. Bacteria in the large intestine further break down the material. Feces contain a relatively small amount of metabolic waste products such as bacterially altered bilirubin, and the dead epithelial cells from the lining of the gut.Feces are discharged through the anus or cloaca during defecation.

Feces can be used as fertilizer or soil conditioner in agriculture. It can also be burned as fuel or dried and used for construction. Some medicinal uses have been found. In the case of human feces, fecal transplants or fecal bacteriotherapy are in use. Urine and feces together are called excreta.

Livestock

Livestock is commonly defined as domesticated animals raised in an agricultural setting to produce labor and commodities such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to those that are bred for consumption, while other times it refers only to farmed ruminants, such as cattle and goats. Horses are considered livestock in the United States. The USDA uses livestock similarly to some uses of the term “red meat”, in which it specifically refers to all the mammal animals kept in this setting to be used as commodities. The USDA mentions pork, veal, beef, and lamb are all classified as livestock and all livestock is considered to be red meats. Poultry and fish are not included in the category.The breeding, maintenance, and slaughter of livestock, known as animal husbandry, is a component of modern agriculture that has been practiced in many cultures since humanity's transition to farming from hunter-gatherer lifestyles. Animal husbandry practices have varied widely across cultures and time periods. Originally, livestock were not confined by fences or enclosures, but these practices have largely shifted to intensive animal farming, sometimes referred to as "factory farming". Now, over 99% of livestock are raised on factory farms. These practices increase yield of the various commercial outputs, but have also led to negative impacts on animal welfare and the environment. Livestock production continues to play a major economic and cultural role in numerous rural communities.

Omnivore

An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutrients and energy of the sources absorbed. Often, they have the ability to incorporate food sources such as algae, fungi, and bacteria into their diet.Omnivores come from diverse backgrounds that often independently evolved sophisticated consumption capabilities. For instance, dogs evolved from primarily carnivorous organisms (Carnivora) while pigs evolved from primarily herbivorous organisms (Artiodactyla). What this means is that physical characteristics are often not reliable indicators of whether an animal has the ability to obtain energy and nutrients from both plant and animal matter. Owing to the wide range of entirely unrelated organisms independently evolving the capability to obtain energy and nutrients from both plant and animal materials, no generalizations about the anatomical features of all omnivores can realistically be made.The variety of different animals that are classified as omnivores can be placed into further sub-categories depending on their feeding behaviors. Frugivores include maned wolves and orangutans; insectivores include swallows and pink fairy armadillos; granivores include large ground finches and mice.

All of these animals are omnivores, yet still fall into special niches in terms of feeding behavior and preferred foods. Being omnivores gives these animals more food security in stressful times or makes possible living in less consistent environments.

People for the Ethical Treatment of Animals

People for the Ethical Treatment of Animals (PETA ; stylized PeTA) is an American animal rights organization based in Norfolk, Virginia, and led by Ingrid Newkirk, its international president. A nonprofit corporation with nearly 400 employees, it claims that it has 6.5 million members and supporters, in addition to claiming that it is the "largest animal rights group in the world." Its slogan is "Animals are not ours to eat, wear, experiment on, use for entertainment, or abuse in any other way."Founded in March 1980 by Ingrid Newkirk and fellow animal rights activist Alex Pacheco, the organization first caught the public's attention in the summer of 1981 during what became known as the Silver Spring monkeys case, a widely publicized dispute about experiments conducted on 17 macaque monkeys inside the Institute of Behavioral Research in Silver Spring, Maryland. The case lasted 10 years, involved the only police raid on an animal laboratory in the United States, triggered an amendment in 1985 to that country's Animal Welfare Act, and established PETA as an internationally known organization. Today, it focuses on four core issues—opposition to factory farming, fur farming, animal testing, and the use of animals in entertainment. It also campaigns for a vegan lifestyle and against eating meat, fishing, the killing of animals regarded as pests, the keeping of chained backyard dogs, cock fighting, dog fighting, and bullfighting.The group is the focus of controversy, both inside and outside the animal rights movement and around the world. Newkirk, and formerly Pacheco, are seen as the leading exporters of animal rights to the more traditional animal-protection groups in the United States, but sections of the movement nonetheless say that PETA is not radical enough—law professor Gary Francione lists the group among what he calls "the new welfarists," arguing that its work with industries to achieve reform, which continues in the tradition of Henry Spira, makes it an animal welfare group, not an animal rights group. Newkirk told Salon in 2001 that PETA works toward the ideal but tries in the meantime to provide carrot-and-stick incentives. There has also been criticism from feminists within the movement about the use of scantily clad women in PETA's anti-fur campaigns and others, but as Norm Phelps notes, "Newkirk has been consistent in her response. No one, she says, is being exploited. Everyone ... is an uncoerced volunteer. Sexual attraction is a fact of life, and if it can advance the animals' cause, she makes no apologies for using it." Also, Phelps notes that some activists believe that the group's media stunts trivialize animal rights, but he qualifies this by saying, "[I]t's hard to argue with success and PETA is far and away the most successful cutting-edge animal rights organization in the world." Newkirk's view is that PETA has a duty to be "press sluts." She argues, "It is our obligation. We would be worthless if we were just polite and didn't make any waves."

Physiology

Physiology (; from Ancient Greek φύσις (physis), meaning 'nature, origin', and -λογία (-logia), meaning 'study of') is the scientific study of the functions and mechanisms which work within a living system.As a sub-discipline of biology, the focus of physiology is on how organisms, organ systems, organs, cells, and biomolecules carry out the chemical and physical functions that exist in a living system.Central to an understanding of physiological functioning is the investigation of the fundamental biophysical and biochemical phenomena, the coordinated homeostatic control mechanisms, and the continuous communication between cells.The physiologic state is the condition occurring from normal body function, while the pathological state is centered on the abnormalities that occur in animal diseases, including humans.According to the type of investigated organisms, the field can be divided into, animal physiology (including that of humans), plant physiology, cellular physiology and microbial physiology.The Nobel Prize in Physiology or Medicine is awarded to those who make significant achievements in this discipline by the Royal Swedish Academy of Sciences.

Slipper

Slippers are light footwear that are easy to put on and off and are intended to be worn indoors, particularly at home.

Veganism

Veganism is the practice of abstaining from the use of animal products, particularly in diet, and an associated philosophy that rejects the commodity status of animals. A follower of the diet or the philosophy is known as a vegan ( VEE-gən). Distinctions may be made between several categories of veganism. Dietary vegans (also known as strict vegetarians) refrain from consuming animal products, not only meat but also eggs, dairy products and other animal-derived substances. The term ethical vegan is often applied to those who not only follow a vegan diet but extend the philosophy into other areas of their lives, and oppose the use of animals for any purpose. Another term is environmental veganism, which refers to the avoidance of animal products on the premise that the industrial farming of animals is environmentally damaging and unsustainable.Well-planned vegan diets are regarded as appropriate for all stages of life, including during infancy and pregnancy, by the American Academy of Nutrition and Dietetics, Dietitians of Canada, Australian National Health and Medical Research Council, New Zealand Ministry of Health, Harvard Medical School, and the British Dietetic Association. The German Society for Nutrition does not recommend vegan diets for children or adolescents, or during pregnancy and breastfeeding. In preliminary clinical research, vegan diets lowered the risk of type 2 diabetes, high blood pressure, obesity, and ischemic heart disease. Vegan diets tend to be higher in dietary fiber, magnesium, folic acid, vitamin C, vitamin E, iron, and phytochemicals; and lower in dietary energy, saturated fat, cholesterol, long-chain omega-3 fatty acids, vitamin D, calcium, zinc, and vitamin B12. As with any poorly-planned diet, unbalanced vegan diets may lead to nutritional deficiencies that nullify any beneficial effects and may cause serious health issues. Some of these deficiencies can only be prevented through the choice of fortified foods or the regular intake of dietary supplements. Vitamin B12 supplementation is especially important because its deficiency causes blood disorders and potentially irreversible neurological damage.Donald Watson coined the term vegan in 1944 when he co-founded the Vegan Society in England. At first he used it to mean "non-dairy vegetarian", but from 1951 the Society defined it as "the doctrine that man should live without exploiting animals". Interest in veganism increased in the 2010s, especially in the latter half. More vegan stores opened and vegan options became increasingly available in supermarkets and restaurants in many countries.

Zoology

Zoology () is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. The term is derived from Ancient Greek ζῷον, zōion, i.e. "animal" and λόγος, logos, i.e. "knowledge, study".

Zoophilia

Zoophilia is a paraphilia involving a sexual fixation on non-human animals. Bestiality is cross-species sexual activity between human and non-human animals. The terms are often used interchangeably, but some researchers make a distinction between the attraction (zoophilia) and the act (bestiality).Although sex with animals is not outlawed in some countries, in most countries, bestiality is illegal under animal abuse laws or laws dealing with buggery or crimes against nature.

Major animal taxa
Extant Animal phyla
Diaphoretickes
Discoba
Loukozoa
Podiata
Hemimastigophora
Incertae sedis
Elements of nature
Universe
Earth
Weather
Natural environment
Life
Extant Life phyla/divisions by domain

Languages

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