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For other uses, see Animal (disambiguation). Animal_sentence_0

"Animalia" redirects here. Animal_sentence_1

For other uses, see Animalia (disambiguation). Animal_sentence_2

Animals (also called Metazoa) are multicellular eukaryotic organisms that form the biological kingdom Animalia. Animal_sentence_3

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. Animal_sentence_4

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. Animal_sentence_5

Animals range in length from 8.5 micrometres (0.00033 in) to 33.6 metres (110 ft). Animal_sentence_6

They have complex interactions with each other and their environments, forming intricate food webs. Animal_sentence_7

The kingdom Animalia includes humans but in colloquial use the term animal often refers only to non-human animals. Animal_sentence_8

The scientific study of animals is known as zoology. Animal_sentence_9

Most living animal species are in Bilateria, a clade whose members have a bilaterally symmetric body plan. Animal_sentence_10

The Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes, arthropods, and molluscs—and the deuterostomes, containing both the echinoderms as well as the chordates, the latter containing the vertebrates. Animal_sentence_11

Life forms interpreted as early animals were present in the Ediacaran biota of the late Precambrian. Animal_sentence_12

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. Animal_sentence_13

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. Animal_sentence_14

Historically, Aristotle divided animals into those with blood and those without. Animal_sentence_15

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. Animal_sentence_16

In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa (now synonymous for Animalia) and the Protozoa, single-celled organisms no longer considered animals. Animal_sentence_17

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 taxa. Animal_sentence_18

Humans make use of many other animal species, such as for food (including meat, milk, and eggs), for materials (such as leather and wool), as pets, and as working animals including for transport. Animal_sentence_19

Dogs have been used in hunting, while many terrestrial and aquatic animals were hunted for sports. Animal_sentence_20

Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. Animal_sentence_21

Etymology Animal_section_0

The word "animal" comes from the Latin , meaning having breath, having soul or living being. Animal_sentence_22

The biological definition includes all members of the kingdom Animalia. Animal_sentence_23

In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animal_sentence_24

Characteristics Animal_section_1

Animals have several characteristics that set them apart from other living things. Animal_sentence_25

Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, and unlike protists, which are eukaryotic but unicellular. Animal_sentence_26

Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. Animal_sentence_27

With very few exceptions, animals respire aerobically. Animal_sentence_28

All animals are motile (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. Animal_sentence_29

The blastula is a stage in embryonic development that is unique to most animals, allowing cells to be differentiated into specialised tissues and organs. Animal_sentence_30

Structure Animal_section_2

All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. Animal_sentence_31

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. Animal_sentence_32

This may be calcified, forming structures such as shells, bones, and spicules. Animal_sentence_33

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. Animal_sentence_34

Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, and desmosomes. Animal_sentence_35

With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues. Animal_sentence_36

These include muscles, which enable locomotion, and nerve tissues, which transmit signals and coordinate the body. Animal_sentence_37

Typically, there is also an internal digestive chamber with either one opening (in Ctenophora, Cnidaria, and flatworms) or two openings (in most bilaterians). Animal_sentence_38

Reproduction and development Animal_section_3

See also: Sexual reproduction § Animals, and Asexual reproduction § Examples in animals Animal_sentence_39

Nearly all animals make use of some form of sexual reproduction. Animal_sentence_40

They produce haploid gametes by meiosis; the smaller, motile gametes are spermatozoa and the larger, non-motile gametes are ova. Animal_sentence_41

These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. Animal_sentence_42

In sponges, blastula larvae swim to a new location, attach to the seabed, and develop into a new sponge. Animal_sentence_43

In most other groups, the blastula undergoes more complicated rearrangement. Animal_sentence_44

It first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. Animal_sentence_45

In most cases, a third germ layer, the mesoderm, also develops between them. Animal_sentence_46

These germ layers then differentiate to form tissues and organs. Animal_sentence_47

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. Animal_sentence_48

Animals have evolved numerous mechanisms for avoiding close inbreeding. Animal_sentence_49

Some animals are capable of asexual reproduction, which often results in a genetic clone of the parent. Animal_sentence_50

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. Animal_sentence_51

Ecology Animal_section_4

Animals are categorised into ecological groups depending on how they obtain or consume organic material, including carnivores, herbivores, omnivores, detritivores, and parasites. Animal_sentence_52

Interactions between animals form complex food webs. Animal_sentence_53

In carnivorous or omnivorous species, predation is a consumer-resource interaction where a predator feeds on another organism (called its prey). Animal_sentence_54

Selective pressures imposed on one another lead to an evolutionary arms race between predator and prey, resulting in various anti-predator adaptations. Animal_sentence_55

Almost all multicellular predators are animals. Animal_sentence_56

Some consumers use multiple methods; for example, in parasitoid wasps, the larvae feed on the hosts' living tissues, killing them in the process, but the adults primarily consume nectar from flowers. Animal_sentence_57

Other animals may have very specific feeding behaviours, such as hawksbill sea turtles primarily eating sponges. Animal_sentence_58

Most animals rely on the biomass and energy produced by plants through photosynthesis. Animal_sentence_59

Herbivores eat plant material directly, while carnivores, and other animals on higher trophic levels typically acquire it indirectly by eating other animals. Animal_sentence_60

Animals oxidize carbohydrates, lipids, proteins, and other biomolecules to unlock the chemical energy of molecular oxygen, which allows the animal to grow and to sustain biological processes such as locomotion. Animal_sentence_61

Animals living close to hydrothermal vents and cold seeps on the dark sea floor consume organic matter of archaea and bacteria produced in these locations through chemosynthesis (by oxidizing inorganic compounds, such as hydrogen sulfide). Animal_sentence_62

Animals originally evolved in the sea. Animal_sentence_63

Lineages of arthropods colonised land around the same time as land plants, probably between 510 and 471 million years ago during the Late Cambrian or Early Ordovician. Animal_sentence_64

Vertebrates such as the lobe-finned fish Tiktaalik started to move on to land in the late Devonian, about 375 million years ago. Animal_sentence_65

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. Animal_sentence_66

Animals are however not particularly heat tolerant; very few of them can survive at constant temperatures above 50 °C (122 °F). Animal_sentence_67

Only very few species of animals (mostly nematodes) inhabit the most extreme cold deserts of continental Antarctica. Animal_sentence_68

Diversity Animal_section_5

Largest and smallest Animal_section_6

Further information: Largest organisms and Smallest organisms Animal_sentence_69

The blue whale (Balaenoptera musculus) is the largest animal that has ever lived, weighing up to at least 190 tonnes and measuring up to 33.6 metres (110 ft) long. Animal_sentence_70

The largest extant terrestrial animal is the African bush elephant (Loxodonta africana), weighing up to 12.25 tonnes and measuring up to 10.67 metres (35.0 ft) long. Animal_sentence_71

The largest terrestrial animals that ever lived were titanosaur sauropod dinosaurs such as Argentinosaurus, which may have weighed as much as 73 tonnes. Animal_sentence_72

Several animals are microscopic; some Myxozoa (obligate parasites within the Cnidaria) never grow larger than 20 µm, and one of the smallest species (Myxobolus shekel) is no more than 8.5 µm when fully grown. Animal_sentence_73

Numbers and habitats Animal_section_7

The following table lists estimated numbers of described extant species for the animal groups with the largest numbers of species, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. Animal_sentence_74

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. Animal_sentence_75

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. Animal_sentence_76

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. Animal_sentence_77


PhylumAnimal_header_cell_0_0_0 ExampleAnimal_header_cell_0_0_1 No. of


LandAnimal_header_cell_0_0_3 SeaAnimal_header_cell_0_0_4 Fresh waterAnimal_header_cell_0_0_5 Free-


AnnelidsAnimal_cell_0_1_0 Animal_cell_0_1_1 17,000Animal_cell_0_1_2 Yes (soil)Animal_cell_0_1_3 YesAnimal_cell_0_1_4 1,750Animal_cell_0_1_5 YesAnimal_cell_0_1_6 400Animal_cell_0_1_7
ArthropodsAnimal_cell_0_2_0 Animal_cell_0_2_1 1,257,000Animal_cell_0_2_2 1,000,000



(Malac- ostraca)Animal_cell_0_2_4

94,000Animal_cell_0_2_5 YesAnimal_cell_0_2_6 >45,000Animal_cell_0_2_7
BryozoaAnimal_cell_0_3_0 Animal_cell_0_3_1 6,000Animal_cell_0_3_2 Animal_cell_0_3_3 YesAnimal_cell_0_3_4 60–80Animal_cell_0_3_5 YesAnimal_cell_0_3_6 Animal_cell_0_3_7
ChordatesAnimal_cell_0_4_0 Animal_cell_0_4_1 65,000


23,000Animal_cell_0_4_3 13,000Animal_cell_0_4_4 18,000


YesAnimal_cell_0_4_6 40


CnidariaAnimal_cell_0_5_0 Animal_cell_0_5_1 16,000Animal_cell_0_5_2 Animal_cell_0_5_3 YesAnimal_cell_0_5_4 Yes (few)Animal_cell_0_5_5 YesAnimal_cell_0_5_6 >1,350


EchinodermsAnimal_cell_0_6_0 Animal_cell_0_6_1 7,500Animal_cell_0_6_2 Animal_cell_0_6_3 7,500Animal_cell_0_6_4 Animal_cell_0_6_5 YesAnimal_cell_0_6_6 Animal_cell_0_6_7
MolluscsAnimal_cell_0_7_0 Animal_cell_0_7_1 85,000


35,000Animal_cell_0_7_3 60,000Animal_cell_0_7_4 5,000


YesAnimal_cell_0_7_6 >5,600Animal_cell_0_7_7
NematodesAnimal_cell_0_8_0 Animal_cell_0_8_1 25,000Animal_cell_0_8_2 Yes (soil)Animal_cell_0_8_3 4,000Animal_cell_0_8_4 2,000Animal_cell_0_8_5 11,000Animal_cell_0_8_6 14,000Animal_cell_0_8_7
PlatyhelminthesAnimal_cell_0_9_0 Animal_cell_0_9_1 29,500Animal_cell_0_9_2 YesAnimal_cell_0_9_3 YesAnimal_cell_0_9_4 1,300Animal_cell_0_9_5 Yes




RotifersAnimal_cell_0_10_0 Animal_cell_0_10_1 2,000Animal_cell_0_10_2 Animal_cell_0_10_3 >400Animal_cell_0_10_4 2,000Animal_cell_0_10_5 YesAnimal_cell_0_10_6 Animal_cell_0_10_7
SpongesAnimal_cell_0_11_0 Animal_cell_0_11_1 10,800Animal_cell_0_11_2 Animal_cell_0_11_3 YesAnimal_cell_0_11_4 200-300Animal_cell_0_11_5 YesAnimal_cell_0_11_6 YesAnimal_cell_0_11_7
Total number of described extant species as of 2013: 1,525,728Animal_header_cell_0_12_0

Evolutionary origin Animal_section_8

Further information: Urmetazoan Animal_sentence_78

The first fossils that might represent animals appear in the 665-million-year-old rocks of the Trezona Formation of South Australia. Animal_sentence_79

These fossils are interpreted as most probably being early sponges. Animal_sentence_80

The oldest animals are found in the Ediacaran biota, towards the end of the Precambrian, around 610 million years ago. Animal_sentence_81

It had long been doubtful whether these included animals, but the discovery of the animal lipid cholesterol in fossils of Dickinsonia establishes that these were indeed animals. Animal_sentence_82

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. Animal_sentence_83

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. Animal_sentence_84

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. Animal_sentence_85

The apparent suddenness of the event may however be an artefact of the fossil record, rather than showing that all these animals appeared simultaneously. Animal_sentence_86

Some palaeontologists have suggested that animals appeared much earlier than the Cambrian explosion, possibly as early as 1 billion years ago. Animal_sentence_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. Animal_sentence_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. Animal_sentence_89

Around the same time, the layered mats of microorganisms called stromatolites decreased in diversity, perhaps due to grazing by newly evolved animals. Animal_sentence_90

Phylogeny Animal_section_9

Further information: Lists of animals Animal_sentence_91

Animals are monophyletic, meaning they are derived from a common ancestor. Animal_sentence_92

Animals are sister to the Choanoflagellata, with which they form the Choanozoa. Animal_sentence_93

The most basal animals, the Porifera, Ctenophora, Cnidaria, and Placozoa, have body plans that lack bilateral symmetry. Animal_sentence_94

Their relationships are still disputed; the sister group to all other animals could be the Porifera or the Ctenophora, both of which lack hox genes, important in body plan development. Animal_sentence_95

These genes are found in the Placozoa and the higher animals, the Bilateria. Animal_sentence_96

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. Animal_sentence_97

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. Animal_sentence_98

The phylogenetic tree (of major lineages only) indicates approximately how many millions of years ago (mya) the lineages split. Animal_sentence_99

Non-bilaterian animals Animal_section_10

Several animal phyla lack bilateral symmetry. Animal_sentence_100

Among these, the sponges (Porifera) probably diverged first, representing the oldest animal phylum. Animal_sentence_101

Sponges lack the complex organization found in most other animal phyla; their cells are differentiated, but in most cases not organised into distinct tissues. Animal_sentence_102

They typically feed by drawing in water through pores. Animal_sentence_103

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. Animal_sentence_104

Animals in both phyla have distinct tissues, but these are not organised into organs. Animal_sentence_105

They are diploblastic, having only two main germ layers, ectoderm and endoderm. Animal_sentence_106

The tiny placozoans are similar, but they do not have a permanent digestive chamber. Animal_sentence_107

Bilaterian animals Animal_section_11

Main articles: Bilateria and Symmetry (biology) § Bilateral symmetry Animal_sentence_108

The remaining animals, the great majority—comprising some 29 phyla and over a million species—form a clade, the Bilateria. Animal_sentence_109

The body is triploblastic, with three well-developed germ layers, and their tissues form distinct organs. Animal_sentence_110

The digestive chamber has two openings, a mouth and an anus, and there is an internal body cavity, a coelom or pseudocoelom. Animal_sentence_111

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. Animal_sentence_112

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. Animal_sentence_113

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; these enable soft-bodied animals with a hydrostatic skeleton to move by peristalsis. Animal_sentence_114

They also have a gut that extends through the basically cylindrical body from mouth to anus. Animal_sentence_115

Many bilaterian phyla have primary larvae which swim with cilia and have an apical organ containing sensory cells. Animal_sentence_116

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. Animal_sentence_117

Genetic studies have considerably changed zoologists' understanding of the relationships within the Bilateria. Animal_sentence_118

Most appear to belong to two major lineages, the protostomes and the deuterostomes. Animal_sentence_119

The basalmost bilaterians are the Xenacoelomorpha. Animal_sentence_120

Protostomes and deuterostomes Animal_section_12

Further information: Embryological origins of the mouth and anus Animal_sentence_121

Main articles: Protostome and Deuterostome Animal_sentence_122

Protostomes and deuterostomes differ in several ways. Animal_sentence_123

Early in development, deuterostome embryos undergo radial cleavage during cell division, while many protostomes (the Spiralia) undergo spiral cleavage. Animal_sentence_124

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. Animal_sentence_125

In deuterostomes, the anus forms first while the mouth develops secondarily. Animal_sentence_126

Most protostomes have schizocoelous development, where cells simply fill in the interior of the gastrula to form the mesoderm. Animal_sentence_127

In deuterostomes, the mesoderm forms by enterocoelic pouching, through invagination of the endoderm. Animal_sentence_128

The main deuterostome phyla are the Echinodermata and the Chordata. Animal_sentence_129

Echinoderms are exclusively marine and include starfish, sea urchins, and sea cucumbers. Animal_sentence_130

The chordates are dominated by the vertebrates (animals with backbones), which consist of fishes, amphibians, reptiles, birds, and mammals. Animal_sentence_131

The deuterostomes also include the Hemichordata (acorn worms). Animal_sentence_132

Ecdysozoa Animal_section_13

Main article: Ecdysozoa Animal_sentence_133

The Ecdysozoa are protostomes, named after their shared trait of ecdysis, growth by moulting. Animal_sentence_134

They include the largest animal phylum, the Arthropoda, which contains insects, spiders, crabs, and their kin. Animal_sentence_135

All of these have a body divided into repeating segments, typically with paired appendages. Animal_sentence_136

Two smaller phyla, the Onychophora and Tardigrada, are close relatives of the arthropods and share these traits. Animal_sentence_137

The ecdysozoans also include the Nematoda or roundworms, perhaps the second largest animal phylum. Animal_sentence_138

Roundworms are typically microscopic, and occur in nearly every environment where there is water; some are important parasites. Animal_sentence_139

Smaller phyla related to them are the Nematomorpha or horsehair worms, and the Kinorhyncha, Priapulida, and Loricifera. Animal_sentence_140

These groups have a reduced coelom, called a pseudocoelom. Animal_sentence_141

Spiralia Animal_section_14

Main article: Spiralia Animal_sentence_142

The Spiralia are a large group of protostomes that develop by spiral cleavage in the early embryo. Animal_sentence_143

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. Animal_sentence_144

All of these are grouped as the Platytrochozoa, which has a sister group, the Gnathifera, which includes the rotifers. Animal_sentence_145

The Lophotrochozoa includes the molluscs, annelids, brachiopods, nemerteans, bryozoa and entoprocts. Animal_sentence_146

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. Animal_sentence_147

These two groups have long been considered close relatives because they share trochophore larvae. Animal_sentence_148

History of classification Animal_section_15

Further information: Taxonomy (biology), History of zoology (through 1859), and History of zoology since 1859 Animal_sentence_149

In the classical era, Aristotle divided animals, based on his own observations, into those with blood (roughly, the vertebrates) and those without. Animal_sentence_150

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). Animal_sentence_151

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. Animal_sentence_152

In 1758, Carl Linnaeus created the first hierarchical classification in his Systema Naturae. Animal_sentence_153

In his original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Animal_sentence_154

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. Animal_sentence_155

The process was begun in 1793 by Jean-Baptiste de Lamarck, who called the Vermes une espèce de chaos (a chaotic mess) and split the group into three new phyla, worms, echinoderms, and polyps (which contained corals and jellyfish). Animal_sentence_156

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. Animal_sentence_157

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). Animal_sentence_158

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. Animal_sentence_159

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. Animal_sentence_160

The protozoa were later moved to the former kingdom Protista, leaving only the Metazoa as a synonym of Animalia. Animal_sentence_161

In human culture Animal_section_16

Main article: Animals in culture Animal_sentence_162

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. Animal_sentence_163

Marine fish of many species are caught commercially for food. Animal_sentence_164

A smaller number of species are farmed commercially. Animal_sentence_165

Invertebrates including cephalopods, crustaceans, and bivalve or gastropod molluscs are hunted or farmed for food. Animal_sentence_166

Chickens, cattle, sheep, pigs and other animals are raised as livestock for meat across the world. Animal_sentence_167

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. Animal_sentence_168

Animals have been hunted and farmed for their fur to make items such as coats and hats. Animal_sentence_169

Dyestuffs including carmine (cochineal), shellac, and kermes have been made from the bodies of insects. Animal_sentence_170

Working animals including cattle and horses have been used for work and transport from the first days of agriculture. Animal_sentence_171

Animals such as the fruit fly Drosophila melanogaster serve a major role in science as experimental models. Animal_sentence_172

Animals have been used to create vaccines since their discovery in the 18th century. Animal_sentence_173

Some medicines such as the cancer drug Yondelis are based on toxins or other molecules of animal origin. Animal_sentence_174

People have used hunting dogs to help chase down and retrieve animals, and birds of prey to catch birds and mammals, while tethered cormorants have been used to catch fish. Animal_sentence_175

Poison dart frogs have been used to poison the tips of blowpipe darts. Animal_sentence_176

A wide variety of animals are kept as pets, from invertebrates such as tarantulas and octopuses, insects including praying mantises, reptiles such as snakes and chameleons, and birds including canaries, parakeets, and parrots all finding a place. Animal_sentence_177

However, the most kept pet species are mammals, namely dogs, cats, and rabbits. Animal_sentence_178

There is a tension between the role of animals as companions to humans, and their existence as individuals with rights of their own. Animal_sentence_179

A wide variety of terrestrial and aquatic animals are hunted for sport. Animal_sentence_180

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. Animal_sentence_181

Major animal paintings include Albrecht Dürer's 1515 The Rhinoceros, and George Stubbs's c. 1762 horse portrait Whistlejacket. Animal_sentence_182

Insects, birds and mammals play roles in literature and film, such as in giant bug movies. Animal_sentence_183

Animals including insects and mammals feature in mythology and religion. Animal_sentence_184

In both Japan and Europe, a butterfly was seen as the personification of a person's soul, while the scarab beetle was sacred in ancient Egypt. Animal_sentence_185

Among the mammals, cattle, deer, horses, lions, bats, bears, and wolves are the subjects of myths and worship. Animal_sentence_186

The signs of the Western and Chinese zodiacs are based on animals. Animal_sentence_187

See also Animal_section_17


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