Hewan: Perbedaan antara revisi

'''Hewan''', '''binatang''', atau '''satwa''' adalah organisme [[eukariotik]] [[multiseluler]] yang membentuk [[Kerajaan (biologi)|kerajaan]] biologi Animalia. Dengan sedikit pengecualian, hewan [[Heterotrof|mengonsumsi bahan organik]], [[Respirasi seluler|menghirup oksigen]], [[Motilitas|dapat bergerak]], [[Reproduksi seksual|bereproduksi secara seksual]], dan tumbuh dari bola sel yang berongga, [[blastula]], selama fase [[Embriogenesis|perkembangan embrio]]. Lebih dari 1,5 juta [[spesies]] hewan [[Takson ekstan|yang masih hidup]] telah [[Deskripsi spesies|dideskripsikan]]—sekitar 1 juta di antaranya adalah [[serangga]]—tetapi diperkirakan ada lebih dari 7 juta spesies [[hewan]] secara keseluruhan. Hewan memiliki panjang dari 8,5 mikrometer sampai 33,6 meter dan memiliki [[Ekologi|interaksi yang kompleks]] dengan satu sama lain dan dengan lingkungannya, serta membentuk [[jaring-jaring makanan]] yang rumit. Studi tentang hewan disebut [[zoologi]].

Sebagian besar spesies hewan yang masih hidup diklasifikasikan dalam [[Bilateria]], [[klad]] yang anggotanya memiliki bangun tubuh [[Simetri di biologi#Simetri bilateral|simetris bilateral]]. Bilateria mencakup [[protostoma]], dan [[Deuterostomia|deuterostoma]]. Di dalam protostoma terdapat banyak kelompok invertebrata, seperti [[nematoda]], [[artropoda]], dan [[moluska]], sementara deuterostoma mencakup [[echinodermata]], dan [[chordata]] (termasuk [[vertebrata]]). Bentuk kehidupan yang ditafsirkan sebagai binatang purba diklasifikasikan dalam [[biota Ediakara]] yang hidup pada eon [[Prakambrium]] akhir. Filum hewan modern terbentuk jelas dalam [[catatan fosil]] sebagai [[Biota laut|spesies laut]] selama [[ledakan Kambrium]] sekitar 542 juta tahun yang lalu. Telah diidentifikasi 6.331 kelompok [[gen]] yang dimiliki semua hewan hidup; gen-gen ini mungkin muncul dari [[#Filogeni|nenek moyang]] tunggal yang hidup [[Kriogenium|650 juta tahun yang lalu]].

Perkataan "hewan" adalah pinjaman dari [[bahasa Arab]], حيوان (haiwandibaca: "hayawan") yang berarti binatang. Perkataan "satwa" adalah pinjaman dari [[bahasa Sanskerta]] yang berarti "makhluk". Sedangkan "binatang" merupakan kata asli [[bahasa Melayu]].{{fact}}

Dalam [[bahasa Inggris]], "hewan" disebut ''animal'', dari [[bahasa Latin]] yaitu "animalis", yang berarti "memiliki napas".<ref>{{cite book|last=Cresswell|first=Julia|title=The Oxford Dictionary of Word Origins|url=https://archive.org/details/oxforddictionary0000unse_p6k3|year=2010|publisher=Oxford University Press|location=New York|edition=2|isbn=9780199547937|quote= ‘having the breath of life’, from anima ‘air, breath, life’ .}}</ref> Dalam penggunaan nonformal sehari-hari, kata tersebut biasanya mengacu pada hewan bukan manusia.<ref name="Dictionary">{{cite web|url=http://www.yourdictionary.com/animal|author=Webster's|title=Animal Definition|accessdate=17 September 2009|archive-date=2011-11-04|archive-url=https://web.archive.org/web/20111104170554/http://www.yourdictionary.com/animal|dead-url=no}}</ref> Kadang-kadang, kerabat dekat manusia seperti [[mamalia]] dan [[vertebrata]] lainnya, ditujukan dalam penggunaan nonformal.<ref>{{cite web |url=http://m-w.com/dictionary/animals |title=Animals |publisher=Merriam-Webster's |quote=2 a : one of the lower animals as distinguished from human beings b : mammal; ''broadly'' : vertebrate |accessdate=16 May 2010 |archive-date=2007-11-12 |archive-url=https://web.archive.org/web/20071112125848/http://www.m-w.com/dictionary/animals |dead-url=no }}</ref> Definisi biologis dari kata tersebut mengacu pada semua anggota [[Kerajaan (biologi)|kingdom]] Animalia, meliputi makhluk yang beragam, seperti [[porifera|spons]], [[Cnidaria|ubur-ubur]], [[Insekta|serangga]], dan [[manusia]].<ref name="americanheritage_animal">{{cite encyclopedia |year=2006 |title=Animal |encyclopedia=The American Heritage Dictionary |publisher=Houghton Mifflin Company |edition=Forth }}</ref>

Hewan memiliki beberapa karakteristik yang membedakan mereka dari makhluk hidup lainnya. Hewan bersifat [[eukariotik]] (memiliki membran inti) dan multiseluler,<ref name="Avila1995">{{cite book |author=Avila, Vernon L. |title=Biology: Investigating Life on Earth |url=https://books.google.com/books?id=B_OOazzGefEC&pg=PA767 |year=1995 |publisher=Jones & Bartlett Learning |isbn=978-0-86720-942-6 |pages=767–}}</ref><ref name="palaeos">{{cite web |title=Palaeos:Metazoa |url=http://palaeos.com/metazoa/metazoa.html |website=Palaeos |accessdate=25 February 2018 |archive-date=2018-02-28 |archive-url=https://web.archive.org/web/20180228005641/http://palaeos.com/metazoa/metazoa.html |dead-url=no }}</ref> tidak seperti bakteri yang [[prokariotik]] dan tidak seperti [[protista]] yang bersifat eukariotik tetapi uniseluler. Tidak seperti tumbuhan dan [[alga]] yang [[Autotrof|menghasilkan nutrisinya sendiri]],<ref name=AnimalCells>{{cite web |last=Davidson |first=Michael W. |title=Animal Cell Structure |url=http://micro.magnet.fsu.edu/cells/animalcell.html |accessdate=20 September 2007 |archiveurl=https://web.archive.org/web/20070920235924/http://micro.magnet.fsu.edu/cells/animalcell.html |archivedate=20 September 2007 |deadurl=no}}</ref> hewan bersifat [[heterotrof]],<ref name="palaeos"/><ref name=Windows>{{cite web |last=Bergman |first=Jennifer |title=Heterotrophs |url=http://www.windows.ucar.edu/tour/link=/earth/Life/heterotrophs.html&edu=high |accessdate=30 September 2007 |archiveurl=https://web.archive.org/web/20070829051950/http://www.windows.ucar.edu/tour/link%3D/earth/Life/heterotrophs.html%26edu%3Dhigh |archivedate=29 August 2007 |deadurl=no}}</ref> artinya memakan bahan organik dan mencernanya secara internal.<ref>{{cite journal |last1=Douglas |first1=Angela E. |last2=Raven |first2=John A. |title=Genomes at the interface between bacteria and organelles |journal=Philosophical Transactions of the Royal Society B |volume=358 |issue=1429 |pages=5–17 |date=January 2003 |pmid=12594915 |pmc=1693093 |doi=10.1098/rstb.2002.1188}}</ref> Dengan sangat sedikit pengecualian, hewan menghirup oksigen dan [[Respirasi aerob|berespirasi secara aerobik]].<ref name="oxygen">{{cite journal |last1=Mentel |first1=Marek |last2=Martin |first2=William |title=Anaerobic animals from an ancient, anoxic ecological niche |journal=BMC Biology |volume=8 |pages=32 |year=2010 |doi=10.1186/1741-7007-8-32 |pmid=20370917 |pmc=2859860}}</ref> Semua hewan bersifat [[Motilitas|motil]]<ref name=Concepts>{{cite web |url=http://employees.csbsju.edu/SSAUPE/biol116/Zoology/digestion.htm |last=Saupe |first=S. G. |title=Concepts of Biology |accessdate=30 September 2007 |archive-date=2007-11-21 |archive-url=https://web.archive.org/web/20071121084100/http://employees.csbsju.edu/SSAUPE/biol116/Zoology/digestion.htm |dead-url=no }}</ref> (mampu secara spontan memindahkan tubuh) selama setidaknya sebagian dari siklus hidupnya, tetapi beberapa hewan, seperti [[spons]], [[koral]], [[kerang]], dan [[teritip]], kemudian menjadi [[Sesilitas (motilitas)|sesil]]. [[Blastula]] adalah tahap dalam perkembangan embrio yang unik untuk sebagian besar hewan,<ref>{{cite book |last=Minkoff |first=Eli C. |title=Barron's EZ-101 Study Keys Series: Biology |url=https://archive.org/details/biology0000mink |year=2008 |publisher=Barron's Educational Series |isbn=978-0-7641-3920-8 |edition=2nd, revised |page=[https://archive.org/details/biology0000mink/page/n48 48]}}</ref> yang memungkinkan [[Diferensiasi sel|sel untuk berdiferensiasi]] menjadi jaringan dan organ khusus.

Semua hewan terdiri dari sel, yang dikelilingi oleh [[matriks ekstraseluler]] yang khas dan terdiri dari [[kolagen]] dan [[glikoprotein]] elastis.<ref>{{cite book |last1=Alberts |first1=Bruce |last2=Johnson |first2=Alexander |last3=Lewis |first3=Julian |last4=Raff |first4=Martin |last5=Roberts |first5=Keith |last6=Walter |first6=Peter |title=Molecular Biology of the Cell |edition=4th |year=2002 |publisher=Garland Science |url=https://www.ncbi.nlm.nih.gov/books/NBK26810/ |isbn=0-8153-3218-1 |access-date=2018-05-05 |archive-date=2016-12-23 |archive-url=https://web.archive.org/web/20161223074013/https://www.ncbi.nlm.nih.gov/books/NBK26810/ |dead-url=no }}</ref> Selama perkembangan, matriks ekstraseluler hewan membentuk kerangka kerja yang relatif fleksibel sehingga sel-sel dapat bergerak dan direorganisasi; hal ini memungkinkan pembentukan struktur yang kompleks. Matriks ekstraseluler dapat mengalami kalsifikasi, membentuk struktur seperti [[Eksoskeleton|cangkang]], [[tulang]], dan [[Spikula (spons)|spikula]].<ref>{{cite book |last=Sangwal |first=Keshra |title=Additives and crystallization processes: from fundamentals to applications |url=https://archive.org/details/additivescrystal00sang |year=2007 |publisher=John Wiley and Sons |isbn=978-0-470-06153-4 |page=[https://archive.org/details/additivescrystal00sang/page/n228 212]}}</ref> Sebaliknya, sel-sel organisme multisel lain (terutama alga, tumbuhan, dan jamur) ditahan di tempatnya oleh dinding sel dan berkembang dengan pertumbuhan progresif.<ref>{{cite book |last=Becker |first=Wayne M. |title=The world of the cell |url=https://archive.org/details/worldofcell00beck_0 |year=1991 |publisher=Benjamin/Cummings |isbn=978-0-8053-0870-9}}</ref> Sel-sel hewan memiliki [[sambungan sel]] yang disebut [[sambungan ketat]], [[sambungan celah]], dan [[desmosom]].<ref>{{cite book |last=Magloire |first=Kim |title=Cracking the AP Biology Exam, 2004–2005 Edition |url=https://archive.org/details/crackingapbiolog00magl |year=2004 |publisher=The Princeton Review |isbn=978-0-375-76393-9 |page=[https://archive.org/details/crackingapbiolog00magl/page/45 45]}}</ref>

Hampir semua hewan menggunakan suatu bentuk reproduksi seksual.<ref>{{cite book |last=Knobil |first=Ernst |title=Encyclopedia of reproduction, Volume 1 |year=1998 |publisher=Academic Press |isbn=978-0-12-227020-8 |page=315}}</ref> Hewan menghasilkan [[gamet]] [[haploid]] melalui [[meiosis]]; gamet yang lebih kecil dan dapat bergerak adalah [[spermatozoa]] dan gamet yang lebih besar dan non-motil adalah [[ovum]].<ref>{{cite book |last=Schwartz |first=Jill |title=Master the GED 2011 |url=https://archive.org/details/petersonsmasterg0000stew_x3f1 |year=2010 |publisher=Peterson's |isbn=978-0-7689-2885-3 |page=[https://archive.org/details/petersonsmasterg0000stew_x3f1/page/371 371]}}</ref> Spermatozoa dan ovum bersatu untuk membentuk [[zigot]],<ref>{{cite book |last=Hamilton |first=Matthew B. |title=Population genetics |url=https://archive.org/details/populationgeneti00hami |year=2009 |publisher=Wiley-Blackwell |isbn=978-1-4051-3277-0 |page=[https://archive.org/details/populationgeneti00hami/page/n69 55]}}</ref> yang berkembang melalui [[mitosis]] menjadi bola berongga yang disebut [[blastula]]. Dalam spons, larva blastula berenang ke lokasi baru, menempel ke dasar laut, dan berkembang menjadi spons baru.<ref>{{cite book |last1=Ville |first1=Claude Alvin |last2=Walker |first2=Warren Franklin |last3=Barnes |first3=Robert D. |title=General zoology |url=https://archive.org/details/generalzoology0000vill_t4w4 |year=1984 |publisher=Saunders College Pub |isbn=978-0-03-062451-3 |page=[https://archive.org/details/generalzoology0000vill_t4w4/page/467 467]}}</ref> Pada sebagian besar kelompok lain, blastula mengalami penataan ulang yang lebih rumit.<ref>{{cite book |last1=Hamilton |first1=William James |last2=Boyd |first2=James Dixon |last3=Mossman |first3=Harland Winfield |title=Human embryology: (prenatal development of form and function) |year=1945 |publisher=Williams & Wilkins |page=330}}</ref> Blastula mengalami invaginasi (pelipatan tertentu) untuk membentuk [[gastrula]] yang memiliki ruang pencernaan dan dua [[lapisan germinal]] yang terpisah, yakni [[ektoderm]] eksternal dan [[endoderm]] internal.<ref>{{cite book |last=Philips |first=Joy B. |title=Development of vertebrate anatomy |url=https://archive.org/details/developmentofver0000phil |year=1975 |publisher=Mosby |isbn=978-0-8016-3927-2 |page=[https://archive.org/details/developmentofver0000phil/page/176 176]}}</ref> Dalam banyak hewan, lapisan germinal ketiga, [[mesoderm]], juga berkembang di antaranya.<ref>{{cite book |title=The Encyclopedia Americana: a library of universal knowledge, Volume 10 |year=1918 |publisher=Encyclopedia Americana Corp. |page=281}}</ref> Lapisan-lapisan germinal ini kemudian berdiferensiasi membentuk jaringan dan organ.<ref>{{cite book |last1=Romoser |first1=William S. |last2=Stoffolano |first2=J. G. |title=The science of entomology |year=1998 |publisher=WCB McGraw-Hill |isbn=978-0-697-22848-2 |page=156}}</ref>

Beberapa hewan mampu melakukan [[reproduksi aseksual]] yang sering menghasilkan klon genetik dari hewan induk. Hal ini mungkin terjadi melalui [[Fragmentasi (reproduksi)|fragmentasi]] dalam bentuk [[Tunas (reproduksi)|tunas]] seperti pada [[Hydra (genus)|''Hydra'']] dan [[cnidaria]] lainnya, atau [[partenogenesis]], ketika telur yang fertil diproduksi tanpa kawin, seperti pada [[kutu daun]].<ref>{{cite book |last1=Adiyodi |first1=K. G. |last2=Hughes |first2=Roger N. |last3=Adiyodi |first3=Rita G. |title=Reproductive Biology of Invertebrates, Volume 11, Progress in Asexual Reproduction |date=July 2002 |publisher=Wiley |page=116 |isbn=978-0-471-48968-9}}</ref><ref>{{cite web |last1=Schatz |first1=Phil |title=Concepts of Biology {{!}} How Animals Reproduce |url=http://philschatz.com/biology-concepts-book/contents/m45547.html |publisher=OpenStax College |accessdate=5 March 2018 |archive-date=2018-03-06 |archive-url=https://web.archive.org/web/20180306022745/http://philschatz.com/biology-concepts-book/contents/m45547.html |dead-url=no }}</ref>

Hewan dikategorikan ke dalam kelompok-kelompok [[ekologi]]s tergantung pada bagaimana mereka memperoleh atau mengonsumsi bahan organik, termasuk [[karnivora]], [[herbivora]], [[omnivora]], [[detritivor]],<ref>{{cite book |title=Geomorphology and environmental impact assessment |url=https://archive.org/details/geomorphologyenv0000unse |year=2001 |publisher=Taylor & Francis |isbn=978-90-5809-344-8 |last1=Marchetti |first1=Mauro |last2=Rivas |first2=Victoria |page=[https://archive.org/details/geomorphologyenv0000unse/page/84 84]}}</ref> dan [[parasit]].<ref>{{cite book |last=Levy |first=Charles K. |title=Elements of Biology |url=https://archive.org/details/elementsofbiolog0000levy |year=1973 |publisher=Appleton-Century-Crofts |isbn=978-0-390-55627-1 |page=[https://archive.org/details/elementsofbiolog0000levy/page/108 108]}}</ref> Interaksi di antara hewan membentuk [[jaring-jaring makanan]] yang rumit. Pada spesies karnivora atau omnivora, [[predasi]] adalah [[Sistem sumber daya-konsumen|interaksi sumber daya-konsumen]] yang terjadi ketika predator memakan organisme lain (disebut sebagai ''mangsa'').<ref name=Ecology>{{cite book |last1=Begon |first1=M. |last2=Townsend |first2=C. |last3=Harper |first3=J. |date=1996 |title=Ecology: Individuals, populations and communities |url=https://archive.org/details/ecology00mich |edition=Third |publisher=Blackwell Science |isbn=0-86542-845-X |pages= }}</ref> Tekanan selektif yang dikenakan pada satu sama lain mengarah pada [[perlombaan senjata evolusioner]] antara predator dan mangsa, yang menghasilkan berbagai [[adaptasi antipredator]].<ref>{{cite book |title=Ecology of marine fishes: California and adjacent waters |url=https://archive.org/details/ecologyofmarinef0000unse |year=2006 |publisher=University of California Press |isbn=978-0-520-24653-9 |last1=Allen |first1=Larry Glen |last2=Pondella |first2=Daniel J. |last3=Horn |first3=Michael H. |page=[https://archive.org/details/ecologyofmarinef0000unse/page/n443 428]}}</ref><ref>{{cite book |last=Caro |first=Tim |authorlink=Tim Caro |title=Antipredator Defenses in Birds and Mammals |url=https://archive.org/details/antipredatordefe0000caro |date=2005 |publisher=University of Chicago Press |pages=1–6[https://archive.org/details/antipredatordefe0000caro/page/1 1]–6 and passim}}</ref> Hampir semua predator multisel adalah hewan.<ref name="SimpsonCB">{{cite journal |doi=10.1016/j.cub.2004.08.038 |pmid=15341755 |title=The real 'kingdoms' of eukaryotes |journal=Current Biology |volume=14 |issue=17 |pages=R693 |year=2004 |last1=Simpson |first1=Alastair G.B |last2=Roger |first2=Andrew J}}</ref> Beberapa [[Konsumen (rantai makanan)|konsumen]] menggunakan beberapa metode; misalnya pada [[tawon parasitoid]], larva memakan jaringan hidup inang dan membunuhnya dalam proses ini,<ref>{{cite journal |last1=Stevens |first1=Alison N. P. |title=Predation, Herbivory, and Parasitism |journal=Nature Education Knowledge |date=2010 |volume=3 |issue=10 |page=36 |url=https://www.nature.com/scitable/knowledge/library/predation-herbivory-and-parasitism-13261134 |accessdate=12 February 2018 |archive-date=2017-09-30 |archive-url=https://web.archive.org/web/20170930230324/http://www.nature.com/scitable/knowledge/library/predation-herbivory-and-parasitism-13261134 |dead-url=no }}</ref> tetapi tawon dewasa umumnya mengonsumsi nektar dari bunga.<ref>{{Cite journal |last=Jervis |first=M. A. |last2=Kidd |first2=N. A. C |date=November 1986 |title=Host-Feeding Strategies in Hymenopteran Parasitoids |url=http://onlinelibrary.wiley.com/doi/10.1111/j.1469-185X.1986.tb00660.x/abstract |journal=Biological Reviews |volume=61 |issue=4 |pages=395–434 |doi=10.1111/j.1469-185x.1986.tb00660.x |access-date=2018-04-19 |archive-date=2017-10-03 |archive-url=https://web.archive.org/web/20171003031807/http://onlinelibrary.wiley.com/doi/10.1111/j.1469-185X.1986.tb00660.x/abstract |dead-url=no }}</ref> Hewan lainnya memiliki perilaku makan yang sangat spesifik, seperti [[penyu sisik]] yang utamanya [[Spongivor|memakan spons]].<ref name="ScienceSpongi">{{cite journal | last =Meylan | first =Anne | title =Spongivory in Hawksbill Turtles: A Diet of Glass | journal =Science | volume =239 | issue =4838 | pages =393–395 | publisher =American Association for the Advancement of Science | date =1988-01-22 | doi=10.1126/science.239.4838.393| id= | pmid =17836872 | jstor=1700236}}</ref>

Sebagian besar hewan mengandalkan energi yang dihasilkan oleh tumbuhan melalui [[fotosintesis]]. Herbivora mengonsumsi tumbuhan secara langsung, sementara karnivora dan hewan lain pada [[tingkat trofik]] yang lebih tinggi biasanya memperoleh energi (dalam bentuk karbon [[Redoks|tereduksi]]) dengan memakan hewan lain. [[Karbohidrat]], [[lipid]], [[protein]], dan biomolekul lainnya dipecah untuk memungkinkan hewan tumbuh dan mempertahankan proses biologis seperti [[Lokomosi hewan|lokomosi]].<ref>{{cite book |title=Understanding Science: Upper Primary |last=Clutterbuck |first=Peter |year=2000 |publisher=Blake Education |isbn=978-1-86509-170-9 |page=9}}</ref><ref>{{cite book |last=Gupta |first=P. K. |title=Genetics Classical To Modern |publisher=Rastogi Publications |isbn=978-81-7133-896-2 |page=26}}</ref><ref>{{cite book |last1=Garrett |first1=Reginald |last2=Grisham |first2=Charles M. |title=Biochemistry |url=https://archive.org/details/biochemistry00garr_360 |year=2010 |publisher=Cengage Learning |isbn=978-0-495-10935-8 |page=[https://archive.org/details/biochemistry00garr_360/page/n572 535]}}</ref> Hewan yang hidup di dekat [[ventilasi hidrotermal]] dan [[rembesan dingin]] di [[dasar laut]] yang gelap tidak bergantung pada energi sinar matahari.<ref>{{cite journal |title=none |year=1996 |journal=New Scientist |publisher=IPC Magazines |volume=152 |issue=2050–2055 |page=105}}</ref> Sebaliknya, [[arkea]] dan bakteri di tempat ini menghasilkan bahan organik melalui [[kemosintesis]] (dengan mengoksidasi senyawa anorganik seperti metana) dan membentuk dasar jaring-jaring makanan lokal.<ref>{{cite book |last1=Castro |first1=Peter |last2=Huber |first2=Michael E. |title=Marine Biology |url=https://archive.org/details/marinebiology0000pete |publisher=McGraw-Hill |year=2007 |edition=7th |page=[https://archive.org/details/marinebiology0000pete/page/376 376] |isbn=978-0-07-722124-9}}</ref>

Hewan awalnya berevolusi di laut. Beberapa garis keturunan artropoda mengolonisasi daratan kurang lebih pada waktu yang sama dengan [[tumbuhan darat]], mungkin antara 510–471 juta tahun yang lalu selama periode [[Kambrium Akhir]] atau [[Ordovisium]] Awal.<ref name="Rota-Stabelli2013">{{cite journal |doi=10.1016/j.cub.2013.01.026 |pmid=23375891 |title=Molecular Timetrees Reveal a Cambrian Colonization of Land and a New Scenario for Ecdysozoan Evolution |journal=Current Biology |volume=23 |issue=5 |pages=392 |year=2013 |last1=Rota-Stabelli |first1=Omar |last2=Daley |first2=Allison&nbsp;C. |last3=Pisani |first3=Davide |url=https://ac.els-cdn.com/S0960982213000298/1-s2.0-S0960982213000298-main.pdf?_tid=spdf-12ada42b-5734-42d3-a41d-53fb216a2e22&acdnat=1519922052_eb0f92cfa2dd11e76e33cfe22ef4a312 |access-date=1 March 2018 }}{{Pranala mati|date=Mei 2021 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> [[Vertebrata]] seperti [[Sarcopterygii|ikan bersirip daging]] ''[[Tiktaalik]]'' mulai pindah ke tanah pada periode [[Devon (periode)|Devon]] akhir, sekitar 375 juta tahun yang lalu.<ref>{{cite journal |journal=[[Nature (journal)|Nature]] |volume=440 |pages=757–763 |date=6 April 2006 |doi=10.1038/nature04639 |title=A Devonian tetrapod-like fish and the evolution of the tetrapod body plan |url=http://www.nature.com/nature/journal/v440/n7085/abs/nature04639.html |last1=Daeschler |first1=Edward B. |last2=Shubin |first2=Neil H. |last3=Jenkins |first3=Farish A., Jr. |pmid=16598249 |issue=7085 |access-date=2018-04-19 |archive-date=2017-05-27 |archive-url=https://web.archive.org/web/20170527134006/http://www.nature.com/nature/journal/v440/n7085/abs/nature04639.html |dead-url=no }}</ref><ref>{{cite journal |authorlink=Jennifer A. Clack |author=Clack, Jennifer A. |journal=Scientific American |url=http://www.scientificamerican.com/article.cfm?id=getting-a-leg-up-on-land |title=Getting a Leg Up on Land |date=21 November 2005 |access-date=2015-06-30 |archive-date=2013-12-07 |archive-url=https://web.archive.org/web/20131207181953/http://www.scientificamerican.com/article.cfm?id=getting-a-leg-up-on-land |dead-url=no }}</ref> Hewan menempati hampir semua habitat dan mikrohabitat di Bumi, termasuk air asin, ventilasi hidrotermal, air tawar, mata air panas, rawa, hutan, padang rumput, gurun, udara, hingga bagian dalam hewan, tumbuhan, jamur dan batu.<ref name="Margulis">{{cite book |author1=Margulis, Lynn |author1link=Lynn Margulis |author2=Schwartz, Karlene V. |author3=Dolan, Michael |title=Diversity of Life: The Illustrated Guide to the Five Kingdoms |url=https://books.google.com/books?id=8wJXWBMsEOkC&pg=PA115 |year=1999 |publisher=Jones & Bartlett Learning |isbn=978-0-7637-0862-7 |pages=115–116}}</ref> Namun, hewan tidak terlalu [[Termofili|tahan panas]]; sangat sedikit hewan yang dapat bertahan hidup pada suhu konstan di atas {{convert|50|°C|0|abbr=on}}.<ref name="Clarke2014">{{cite journal|doi=10.1017/S1473550413000438|title=The thermal limits to life on Earth |journal=International Journal of Astrobiology |volume=13 |issue=2 |pages=141 |year=2014|last1=Clarke|first1=Andrew|bibcode=2014IJAsB..13..141C}}</ref> Hanya sedikit spesies hewan (kebanyakan [[nematoda]]) yang menghuni gurun paling dingin di benua [[Antartika]].<ref name="bas-land">{{cite web|title=Land animals|url=https://www.bas.ac.uk/about/antarctica/wildlife/land-animals/|publisher=British Antarctic Survey|accessdate=7 March 2018|archive-date=2018-11-06|archive-url=https://web.archive.org/web/20181106225451/https://www.bas.ac.uk/about/antarctica/wildlife/land-animals/|dead-url=no}}</ref>

[[Paus biru]] (''Balaenoptera musculus'') adalah hewan terbesar yang pernah hidup, dengan berat mencapai 190 metrik [[ton]] dan panjang mencapai {{convert|33,6|m|ft}}.<ref name=Wood>Wood, Gerald ''The Guinness Book of Animal Facts and Feats'' (1983) {{ISBN|978-0-85112-235-9}}</ref><ref>{{cite web |last1=Davies |first1=Ella |title=The longest animal alive may be one you never thought of |url=http://www.bbc.com/earth/story/20160420-the-longest-animal-alive-may-not-be-the-blue-whale |website=BBC Earth |accessdate=1 March 2018 |date=20 April 2016 |archive-date=2018-03-19 |archive-url=https://web.archive.org/web/20180319073808/http://www.bbc.com/earth/story/20160420-the-longest-animal-alive-may-not-be-the-blue-whale |dead-url=no }}</ref><ref>{{Cite web|url=https://www.guinnessworldrecords.com/world-records/largest-mammal|title=Largest mammal|website=Guinness World Records|access-date=2020-04-14|archive-date=2018-01-31|archive-url=https://web.archive.org/web/20180131024019/https://www.guinnessworldrecords.com/world-records/largest-mammal|dead-url=no}}</ref> Hewan darat terbesar yang masih ada adalah [[gajah semak afrika]] (''Loxodonta africana''), dengan berat mencapai 12,25 ton<ref name="Wood"/> dan panjang hingga {{convert|10,67|m|ft}}.<ref name=Wood/> Hewan darat terbesar yang pernah hidup adalah [[Sauropoda|dinosaurus sauropoda]] [[titanosaurus]] seperti ''[[Argentinosaurus]]'', yang mungkin beratnya mencapai 73 ton.<ref name="Mazzettaetal2004">{{cite journal |last=Mazzetta |first=Gerardo V. |author2=Christiansen, Per |author3=Fariña, Richard A. |year=2004 |title=Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs |journal=Historical Biology |volume=16 |issue= 2–4 |pages=71–83 |doi=10.1080/08912960410001715132}}</ref> Beberapa hewan bersifat mikroskopik; beberapa [[Myxozoa]] ([[parasit obligat]] yang termasuk dalam Cnidaria) tidak pernah tumbuh lebih besar dari 20&nbsp;[[Mikrometer|μm]],<ref>{{cite web |url=http://tolweb.org/Myxozoa/2460/2008.07.10 |title=Myxozoa |author=Fiala, Ivan |date=10 July 2008 |publisher=Tree of Life Web Project |accessdate=4 March 2018 |archive-date=2018-03-01 |archive-url=https://web.archive.org/web/20180301225416/http://tolweb.org/Myxozoa/2460/2008.07.10 |dead-url=no }}</ref> dan salah satu spesies terkecil (''Myxobolus shekel'') tidak lebih dari 8,5&nbsp;μm saat tumbuh dewasa.<ref>{{cite journal|title=Two new species of Myxobolus (Myxozoa: Myxosporea: Bivalvulida) infecting an Indian major carp and a cat fish in wetlands of Punjab, India | pmc=3235390 | pmid=23024499 | doi=10.1007/s12639-011-0061-4 | volume=35 | year=2011 | journal=J Parasit Dis | pages=169–76 | last1=Kaur | first1=H. | last2=Singh | first2=R.}}</ref>

Tabel berikut mencantumkan perkiraan jumlah spesies yang ada yang masih ada untuk kelompok-kelompok hewan dengan jumlah spesies terbesar,<ref name="Zhang2013">{{cite journal | last=Zhang | first=Zhi-Qiang | title=Animal biodiversity: An update of classification and diversity in 2013. In: Zhang, Z.-Q. (Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013) | journal=Zootaxa | volume=3703 | issue=1 | date=2013-08-30 | doi=10.11646/zootaxa.3703.1.3 | url=https://biotaxa.org/Zootaxa/article/download/zootaxa.3703.1.3/4273 | page=5 | access-date=2018-03-15 | archive-date=2019-04-24 | archive-url=https://web.archive.org/web/20190424154926/https://biotaxa.org/Zootaxa/article/download/zootaxa.3703.1.3/4273 | dead-url=yes }}</ref> dengan habitat utama mereka (darat, air tawar,<ref name=Balian2008>{{cite book|last1=Balian |first1=E.V. |last2=Lévêque |first2=C. |last3=Segers|first3=H.|first4=K. |last4=Martens |title=Freshwater Animal Diversity Assessment |url=https://books.google.com/books?id=Dw4H6DBHnAgC&pg=PA628 |year=2008 |publisher=Springer |isbn=978-1-4020-8259-7 |page=628}}</ref> dan laut),<ref name="Hogenboom2016">{{cite web|last1=Hogenboom |first1=Melissa |title=There are only 35 kinds of animal and most are really weird|url=http://www.bbc.co.uk/earth/story/20150325-all-animal-life-in-35-photos|publisher=BBC earth|access-date=2018-03-15|archive-date=2018-08-10|archive-url=https://web.archive.org/web/20180810141811/http://www.bbc.co.uk/earth/story/20150325-all-animal-life-in-35-photos|dead-url=no}}</ref> dan cara hidup bebas atau parasit.<ref name=Poulin2007>{{cite book | last=Poulin | first=Robert |authorlink=Robert Poulin (zoologis) | title=Evolutionary Ecology of Parasites | url=https://archive.org/details/evolutionaryecol0000poul | publisher=Princeton University Press | year=2007 | isbn=978-0-691-12085-0 |page=[https://archive.org/details/evolutionaryecol0000poul/page/6 6]}}</ref> Perkiraan spesies yang ditunjukkan di sini didasarkan pada angka yang dideskripsikan secara ilmiah; perkiraan yang jauh lebih besar telah dihitung berdasarkan berbagai cara prediksi, dan ini bisa sangat bervariasi. Misalnya, sekitar 25.000–27.000 spesies nematoda telah dideskripsikan, sementara perkiraan jumlah nematoda yang dipublikasikan mencakup 10.000–20.000; 500.000; 10 juta; dan 100 juta.<ref name=Felder2009>{{cite book |last1=Felder |first1=Darryl L. |last2=Camp |first2=David K. |title=Gulf of Mexico Origin, Waters, and Biota: Biodiversity |url=https://books.google.com/books?id=CphA8hiwaFIC&pg=RA1-PA1111 |year=2009 |publisher=Texas A&M University Press |isbn=978-1-60344-269-5 |page=1111}}</ref> Dengan menggunakan pola dalam hierarki [[taksonomi]], jumlah spesies hewan—termasuk yang belum dideskripsikan—dihitung menjadi sekitar 7,77 juta pada tahun 2011.<ref>{{cite web |title=How many species on Earth? About 8.7 million, new estimate says |url=https://www.sciencedaily.com/releases/2011/08/110823180459.htm |accessdate=2 March 2018 |date=24 August 2011 |archive-date=2018-07-01 |archive-url=https://web.archive.org/web/20180701164954/https://www.sciencedaily.com/releases/2011/08/110823180459.htm |dead-url=no }}</ref><ref name="Mora2011">{{cite journal | last=Mora | first=Camilo | last2=Tittensor | first2=Derek P. | last3=Adl | first3=Sina | last4=Simpson | first4=Alastair G. B. | last5=Worm | first5=Boris | editor-last=Mace | editor-first=Georgina M. | title=How Many Species Are There on Earth and in the Ocean? | journal=PLoS Biology | volume=9 | issue=8 | date=2011-08-23 | doi=10.1371/journal.pbio.1001127 | page=e1001127 | pmid=21886479 | pmc=3160336}}</ref>{{efn|Aplikasi [[kode batang DNA]] pada taksonomi semakin memperrumit hal ini; sebuah analisis kode batang DNA pada 2016 memperkirakan bahwa terdapat 100.000 spesies [[serangga]] di [[Kanada]] saja, dan mengekstrapolasikan bahwa fauna serangga global seharusnya lebih dari 10 juta spesies, hampir 2 juta di dalam satu famili lalat yang disebut ''gall midge'' ([[Cecidomyiidae]]).<ref>{{cite journal |last1=Hebert |first1=Paul D. N. |last2=Ratnasingham |first2=Sujeevan |last3=Zakharov |first3=Evgeny V. |last4=Telfer |first4=Angela C. |last5=Levesque-Beaudin |first5=Valerie |last6=Milton |first6=Megan A. |last7=Pedersen |first7=Stephanie |last8=Jannetta |first8=Paul |last9=deWaard |first9=Jeremy R. |title=Counting animal species with DNA barcodes: Canadian insects |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |date=1 August 2016 |volume=371 |issue=1702 |pages=20150333 |doi=10.1098/rstb.2015.0333 |pmid=27481785 |url=http://rstb.royalsocietypublishing.org/content/371/1702/20150333.long |pmc=4971185 |access-date=2018-05-04 |archive-date=2018-04-29 |archive-url=https://web.archive.org/web/20180429155232/http://rstb.royalsocietypublishing.org/content/371/1702/20150333.long |dead-url=no }}</ref>}}

[[Fosil]] pertama yang mungkin mewakili hewan muncul di bebatuan berusia 665 juta tahun di [[Formasi Trezona]] di [[Australia Selatan]]. Fosil-fosil ini ditafsirkan sebagai spons awal.<ref name=roseMaloof>{{cite journal |title=Possible animal-body fossils in pre-Marinoan limestones from South Australia |journal=Nature Geoscience |volume=3 |pages=653–659 |date=17 August 2010 |url=http://www.nature.com/ngeo/journal/v3/n9/full/ngeo934.html |doi=10.1038/ngeo934 |issue=9 |bibcode=2010NatGe...3..653M |last1=Maloof |first1=Adam C. |last2=Rose |first2=Catherine V. |last3=Beach |first3=Robert |last4=Samuels |first4=Bradley M. |last5=Calmet |first5=Claire C. |last6=Erwin |first6=Douglas H. |last7=Poirier |first7=Gerald R. |last8=Yao |first8=Nan |last9=Simons |first9=Frederik J. |access-date=2018-04-15 |archive-date=2011-08-28 |archive-url=https://web.archive.org/web/20110828152648/http://www.nature.com/ngeo/journal/v3/n9/full/ngeo934.html |dead-url=no }}</ref>

Hewan-hewan tertua ditemukan di [[biota Ediakara]], menjelang akhir Prakambrium, sekitar 610 juta tahun yang lalu. Apakah biota Ediakara merupakan hewan telah lama diragukan,<ref>{{cite journal | last1=Shen | first1=Bing | last2=Dong | first2=Lin | last3=Xiao | first3=Shuhai | last4=Kowalewski | first4=Michał | year=2008 | title=The Avalon Explosion: Evolution of Ediacara Morphospace | url=http://www.sciencemag.org/content/319/5859/81.short | journal=Science | volume=319 | issue=5859 | pages=81–84 | doi=10.1126/science.1150279 | pmid=18174439 | bibcode=2008Sci...319...81S | access-date=2018-04-15 | archive-date=2015-09-24 | archive-url=https://web.archive.org/web/20150924154348/http://www.sciencemag.org/content/319/5859/81.short | dead-url=no }}</ref><ref>{{cite journal |url=http://advances.sciencemag.org/content/4/6/eaao6691 |title=Late Ediacaran trackways produced by bilaterian animals with paired appendages |first1=Zhe |last1=Chen |first2=Xiang |last2=Chen |first3=Chuanming |last3=Zhou |first4=Xunlai |last4=Yuan |first5=Shuhai |last5=Xiao |date=1 June 2018 |journal=Science Advances |volume=4 |issue=6 |pages=eaao6691 |doi=10.1126/sciadv.aao6691 |pmid=29881773 |pmc=5990303 |access-date=2018-10-08 |archive-date=2018-06-29 |archive-url=https://web.archive.org/web/20180629102734/http://advances.sciencemag.org/content/4/6/eaao6691 |dead-url=no }}</ref><ref>{{cite book |last=Schopf |first=J. William |title=Evolution!: facts and fallacies |url=https://archive.org/details/evolutionfactsfa0000unse |year=1999 |publisher=Academic Press |isbn=978-0-12-628860-5 |page=[https://archive.org/details/evolutionfactsfa0000unse/page/7 7]}}</ref> tetapi penemuan lipid hewan [[kolesterol]] pada fosil ''[[Dickinsonia]]'' menetapkan bahwa biota Ediakara benar-benar merupakan hewan.<ref name="Bobrovskiy Hope Ivantsov Nettersheim pp. 1246–1249"/>

[[Invertebrata]] (atau Avertebrata) adalah hewan yang termasuk kedalam jenis hewan yang tidak memiliki [[tulang punggung]] antar ruas-ruas tulang belakang. Hewan avertebrata ini terbagi atas beberapa golongan yaitu filum [[Protozoa]], [[Porifera]], [[Artropoda]], [[Platyhelminthes]], [[Nemathelminthes]], [[Annelida]], [[Coelenterata]], [[Moluska]], dan [[Echinodermata]].<ref>{{Cite journal|last=Alwi, D., Muhammad, M.H., dan Bisi, S.|first=|date=2018|title=Inventarisasi organisme avertebrata terumbu karang di perairan Tanjung Dehegila Kabupaten Pulau Morotai|url=https://ejournal.unkhair.ac.id/index.php/kelautan/article/download/683/490|journal=Jurnal Ilmu Kelautan Kepulauan|volume=1|issue=1|pages=72|doi=|access-date=2021-01-31|archive-date=2020-07-13|archive-url=https://web.archive.org/web/20200713150025/http://ejournal.unkhair.ac.id/index.php/kelautan/article/download/683/490|dead-url=no}}</ref>

Gen-gen ini ditemukan di Placozoa<ref>{{Cite web |url=https://emb.carnegiescience.edu/sites/emb.carnegiescience.edu/files/evodevo12.pdf |title=Evolution and Development |date=1 May 2012 |website=Carnegie Institution for Science Department of Embryology |page=38 |archive-url=https://web.archive.org/web/20140302084415/http://emb.carnegiescience.edu/sites/emb.carnegiescience.edu/files/evodevo12.pdf |archive-date=2 March 2014 |dead-url=yes |access-date=4 March 2018}}</ref><ref name="Dellaporta2004">{{cite journal | last=Dellaporta | first=Stephen | last2=Holland | first2=Peter | last3=Schierwater | first3=Bernd | last4=Jakob | first4=Wolfgang | last5=Sagasser | first5=Sven | last6=Kuhn | first6=Kerstin | title=The Trox-2 Hox/ParaHox gene of Trichoplax (Placozoa) marks an epithelial boundary | journal=Development Genes and Evolution | volume=214 | issue=4 | date=April 2004 | doi=10.1007/s00427-004-0390-8 | pages=170–175}}</ref> dan hewan yang lebih tinggi, yaitu Bilateria.<ref name="Peterson2001">{{cite journal |doi=10.1046/j.1525-142x.2001.003003170.x |pmid=11440251 |url=http://onlinelibrary.wiley.com/doi/10.1046/j.1525-142x.2001.003003170.x/full |accessdate=25 February 2018 |title=Animal phylogeny and the ancestry of bilaterians: Inferences from morphology and 18S rDNA gene sequences |journal=Evolution and Development |volume=3 |issue=3 |pages=170 |year=2001 |last1=Peterson |first1=Kevin J. |last2=Eernisse |first2=Douglas J |archive-date=2018-02-26 |archive-url=https://web.archive.org/web/20180226033729/http://onlinelibrary.wiley.com/doi/10.1046/j.1525-142x.2001.003003170.x/full |dead-url=no }}</ref><ref name="KraemerEis2016">{{cite journal |doi=10.1101/041806 |url=https://www.biorxiv.org/content/biorxiv/early/2016/03/19/041806.full.pdf |accessdate=25 February 2018 |title=A catalogue of Bilaterian-specific genes - their function and expression profiles in early development |year=2016 |last1=Kraemer-Eis |first1=Andrea |last2=Ferretti |first2=Luca |last3=Schiffer |first3=Philipp |last4=Heger |first4=Peter |last5=Wiehe |first5=Thomas |archive-date=2018-02-26 |archive-url=https://web.archive.org/web/20180226032414/https://www.biorxiv.org/content/biorxiv/early/2016/03/19/041806.full.pdf |dead-url=no }}</ref> Ada 6.331 kelompok [[gen]] yang dimiliki semua hewan hidup telah diidentifikasi; gen-gen ini mungkin muncul dari satu nenek moyang bersama yang hidup [[Kriogenium|650 juta tahun yang lalu]] pada masa [[Prakambrium]]. Sebanyak 25 di antaranya merupakan kelompok gen inti baru yang hanya ditemukan pada hewan; dari 25 kelompok gen tersebut, delapan di antaranya merupakan komponen penting dari jalur pensinyalan [[jalur pensinyalan Wnt|Wnt]] dan [[TGF-beta]] yang mungkin telah memungkinkan hewan menjadi multiseluler dengan menyediakan pola untuk sistem sumbu tubuh (dalam tiga dimensi), dan tujuh kelompok gen lainnya untuk [[faktor transkripsi]], termasuk protein [[homeodomain]] yang terlibat dalam [[Peralatan gen evo-devo|kontrol perkembangan]].<ref name="NYT-20180504">{{cite news |last=Zimmer |first=Carl |authorlink=Carl Zimmer |title=The Very First Animal Appeared Amid an Explosion of DNA |url=https://www.nytimes.com/2018/05/04/science/first-animal-genes-evolution.html |date=4 May 2018 |work=[[The New York Times]] |accessdate=4 May 2018 |archive-date=2019-05-28 |archive-url=https://web.archive.org/web/20190528103558/https://www.nytimes.com/2018/05/04/science/first-animal-genes-evolution.html |dead-url=no }}</ref><ref name="NC-20150430">{{cite journal |last1=Paps |first1=Jordi |last2=Holland |first2=Peter W. H. |title=Reconstruction of the ancestral metazoan genome reveals an increase in genomic novelty |url=https://www.nature.com/articles/s41467-018-04136-5 |date=30 April 2018 |journal=[[Nature Communications]] |volume=9 |number=1730 (2018) |doi=10.1038/s41467-018-04136-5 |accessdate=4 May 2018 |archive-date=2019-05-24 |archive-url=https://web.archive.org/web/20190524170040/https://www.nature.com/articles/s41467-018-04136-5 |dead-url=no }}</ref>

Ctenophora (ubur-ubur sisir) dan Cnidaria (yang mencakup ubur-ubur, [[anemon laut]], dan koral) memiliki simetri radial dan memiliki rongga pencernaan dengan bukaan tunggal, yang berfungsi baik sebagai mulut maupun anus.<ref>{{cite book |title=A Living Bay: The Underwater World of Monterey Bay |year=2000 |publisher=University of California Press |isbn=978-0-520-22149-9 |last1=Langstroth |first1=Lovell |last2=Langstroth |first2=Libby |editor-last=Newberry |editor-first=Todd |page=244}}</ref> Hewan di kedua filum tersebut memiliki jaringan yang berbeda, tetapi jaringan-jaringan ini tidak diatur dalam organ.<ref>{{cite book |last=Safra |first=Jacob E. |title=The New Encyclopædia Britannica, Volume 16 |year=2003 |publisher=Encyclopædia Britannica |isbn=978-0-85229-961-6 |page=523}}</ref> Mereka bersifat [[diploblastik]], yaitu hanya memiliki dua lapisan germinal utama, ektoderm dan endoderm.<ref>{{cite book |last=Kotpal |first=R. L. |title=Modern Text Book of Zoology: Invertebrates |publisher=Rastogi Publications |isbn=978-81-7133-903-7 |page=184}}</ref> [[Placozoa]] yang berukuran kecil mirip dengan kedua filum di atas, tetapi mereka tidak memiliki rongga pencernaan permanen.<ref>{{cite book |author= Barnes, Robert D. |year=1982 |title=Invertebrate Zoology |publisher=Holt-Saunders International |pages=84–85 |isbn=0-03-056747-5}}</ref><ref>{{cite web |author=<!--"A.G.C."--> |title=Introduction to Placozoa |url=http://www.ucmp.berkeley.edu/phyla/placozoa/placozoa.html |publisher=UCMP Berkeley |accessdate=10 March 2018 |archive-date=2018-03-25 |archive-url=https://web.archive.org/web/20180325202849/http://www.ucmp.berkeley.edu/phyla/placozoa/placozoa.html |dead-url=no }}</ref>

Memiliki ujung depan berarti bahwa bagian tubuh ini mengalami rangsangan, seperti makanan, mendukung [[sefalisasi]], perkembangan kepala dengan [[organ indera]] dan mulut. Banyak bilateria memiliki kombinasi [[otot|otot-otot]] melingkar yang menyempitkan tubuh, membuatnya lebih panjang, dan satu set otot memanjang (longitudinal), yang memendekkan tubuh;<ref name=Brusca2016/> ini memungkinkan hewan bertubuh lunak dengan [[kerangka hidrostatik]] bergerak dengan [[peristalsis]].<ref name=Quillin>{{cite journal |author=Quillin, K. J. |title=Ontogenetic scaling of hydrostatic skeletons: geometric, static stress and dynamic stress scaling of the earthworm lumbricus terrestris |journal=The Journal of Experimental Biology |volume=201 |issue=12 |pages=1871–83 |date=May 1998 |pmid=9600869 |url=http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=9600869 |access-date=2018-04-16 |archive-date=2020-06-17 |archive-url=https://web.archive.org/web/20200617135617/https://jeb.biologists.org/content/201/12/1871.long |dead-url=yes }}</ref> Mereka juga memiliki usus sepanjang tubuh yang pada dasarnya silinder dari mulut ke anus. Banyak filum bilateria memiliki [[larva]] primer yang berenang dengan [[silia]] dan memiliki organ apikal yang mengandung sel-sel sensorik. Namun, ada pengecualian untuk masing-masing karakteristik ini; misalnya, echinodermata dewasa bersifat simetris radial (tidak seperti larvanya), sementara beberapa cacing parasit memiliki struktur tubuh yang sangat disederhanakan.<ref name="Minelli2009">{{cite book|author=Minelli, Alessandro |title=Perspectives in Animal Phylogeny and Evolution |url=https://books.google.com/books?id=jIASDAAAQBAJ&pg=PA53 |year=2009 |publisher=Oxford University Press |isbn=978-0-19-856620-5 |page=53}}</ref><ref name=Brusca2016>{{Cite book |url=http://www.sinauer.com/media/wysiwyg/samples/Brusca3e_Chapter_9.pdf |title=Introduction to the Bilateria and the Phylum Xenacoelomorpha {{!}} Triploblasty and Bilateral Symmetry Provide New Avenues for Animal Radiation |work=Invertebrates |last=Brusca |first=Richard C. |date=2016 |publisher=Sinauer Associates |pages=345–372 |isbn=978-1605353753 |access-date=2018-04-16 |archive-date=2019-04-24 |archive-url=https://web.archive.org/web/20190424155137/https://www.sinauer.com/media/wysiwyg/samples/Brusca3e_Chapter_9.pdf |dead-url=no }}</ref>

Studi genetika telah banyak mengubah pemahaman para ahli zoologi tentang hubungan dalam Bilateria. Kebanyakan filum termasuk dalam dua garis keturunan utama, [[Protostomia]] dan [[Deuterostomia]].<ref name="Telford 2008 pp. 457–459">{{cite journal | last=Telford | first=Maximilian J. | title=Resolving Animal Phylogeny: A Sledgehammer for a Tough Nut? | journal=Developmental Cell | volume=14 | issue=4 | year=2008 | doi=10.1016/j.devcel.2008.03.016 | pages=457–459 | pmid=18410719}}</ref> Bilateria paling basal adalah [[Xenacoelomorpha]].<ref name="Philippe2011">{{cite journal |last1=Philippe |first1=H. |last2=Brinkmann |first2=H. |last3=Copley |first3=R. R. |last4=Moroz |first4=L. L. |last5=Nakano |first5=H. |last6=Poustka |first6=A. J. |last7=Wallberg |first7=A. |last8=Peterson |first8=K. J. |last9=Telford |first9=M. J. |title=Acoelomorph flatworms are deuterostomes related to ''Xenoturbella'' |journal=Nature |volume=470 |pages=255–258 |year=2011 |pmid=21307940 |doi=10.1038/nature09676 |bibcode=2011Natur.470..255P |issue=7333 |pmc=4025995}}</ref><ref name="Perseke2007">{{cite journal |last1=Perseke |first1=M. |last2=Hankeln |first2=T. |last3=Weich |first3=B. |last4=Fritzsch |first4=G. |last5=Stadler |first5=P.F. |last6=Israelsson |first6=O. |last7=Bernhard |first7=D. |last8=Schlegel |first8=M. |title=The mitochondrial DNA of Xenoturbella bocki: genomic architecture and phylogenetic analysis |journal=Theory Biosci |volume=126 |issue=1 |date=August 2007 |pages=35–42 | url=http://www.bioinf.uni-leipzig.de/Publications/PREPRINTS/07-009.pdf |pmid=18087755 |doi=10.1007/s12064-007-0007-7 |access-date=2018-04-16 |archive-date=2019-04-24 |archive-url=https://web.archive.org/web/20190424154927/http://www.bioinf.uni-leipzig.de/Publications/PREPRINTS/07-009.pdf |dead-url=no }}</ref><ref name="Cannon 2016">{{cite journal |last=Cannon |first=Johanna T. |last2=Vellutini |first2=Bruno C. |last3=Smith III |first3=Julian. |last4=Ronquist |first4=Frederik |last5=Jondelius |first5=Ulf |last6=Hejnol |first6=Andreas |date=3 February 2016 |title=Xenacoelomorpha is the sister group to Nephrozoa |url=http://www.nature.com/nature/journal/v530/n7588/full/nature16520.html |journal=Nature |publisher= |volume=530 |issue=7588 |pages=89–93 |doi=10.1038/nature16520 |access-date=3 February 2016 |pmid=26842059 |bibcode=2016Natur.530...89C}}</ref>

Protostoma dan deuterostoma berbeda dalam beberapa hal. Pada awal perkembangan, embrio deuterostoma menjalani [[Penyibakan (embrio)|penyibakan]] radial selama pembelahan sel, sementara banyak protostoma ([[Spiralia]]) mengalami penyibakan spiral.<ref>{{cite journal |last=Valentine |first=James W. |date=July 1997 |title=Cleavage patterns and the topology of the metazoan tree of life |journal=PNAS |publisher=The National Academy of Sciences |volume=94 |pages=8001–8005 |bibcode=1997PNAS...94.8001V |doi=10.1073/pnas.94.15.8001 |pmid=9223303 |pmc=21545 |issue=15}}</ref> Hewan dari kedua kelompok memiliki saluran pencernaan yang lengkap, tetapi dalam protostoma pembukaan pertama [[Arkenteron|usus embrio]] berkembang menjadi mulut, dan anus terbentuk sekunder. Dalam deuterostoma, anus terbentuk pertama dan mulut berkembang secara sekunder.<ref>{{cite book |last1=Peters |first1=Kenneth E. |last2=Walters |first2=Clifford C. |last3=Moldowan |first3=J. Michael |title=The Biomarker Guide: Biomarkers and isotopes in petroleum systems and Earth history |volume=2 |year=2005 |publisher=Cambridge University Press |isbn=978-0-521-83762-0 |page=717}}</ref><ref name=Hejnol2009>{{cite book |last1=Hejnol |first1=A. |last2=Martindale |first2=M.Q. |url=https://www.researchgate.net/publication/230766195_The_mouth_the_anus_and_the_blastopore_-_open_questions_about_questionable_openings |title=The mouth, the anus, and the blastopore–open questions about questionable openings| |work=Animal Evolution—Genomes, Fossils, and Trees |veditors=Telford MJ, Littlewood DJ |date=2009 |publisher=Oxford University Press |isbn=978-0199570300 |pages=33–40 |access-date=2018-04-17 |archive-date=2018-06-15 |archive-url=https://web.archive.org/web/20180615190611/https://www.researchgate.net/publication/230766195_The_mouth_the_anus_and_the_blastopore_-_open_questions_about_questionable_openings |dead-url=no }}</ref> Kebanyakan protostoma memiliki perkembangan [[Schizocoely|schizocoelous]], di mana sel-sel hanya mengisi bagian dalam gastrula untuk membentuk mesoderm. Dalam deuterostom, mesoderm terbentuk oleh kantong [[Enteroseli|enterocoelous]], melalui invaginasi endoderm.<ref>{{cite book |last=Safra |first=Jacob E. |title=The New Encyclopædia Britannica, Volume 1; Volume 3 |year=2003 |publisher=Encyclopædia Britannica |isbn=978-0-85229-961-6 |page=767}}</ref>

Filum deuterostoma utama adalah Echinodermata dan Chordata.<ref>{{cite book |last=Hyde |first=Kenneth |title=Zoology: An Inside View of Animals |year=2004 |publisher=Kendall Hunt |isbn=978-0-7575-0997-1 |page=345}}</ref> Echinodermata secara eksklusif hidup di laut dan termasuk [[bintang laut]], [[bulu babi]], dan [[teripang]].<ref>{{cite book |last=Alcamo |first=Edward |title=Biology Coloring Workbook |year=1998 |publisher=The Princeton Review |isbn=978-0-679-77884-4 |page=220}}</ref> Chordata didominasi oleh vertebrata (hewan dengan [[Columna vertebralis|tulang punggung]]),<ref>{{cite book |last=Holmes |first=Thom |title=The First Vertebrates |url=https://archive.org/details/firstvertebrates00holm |publisher=Infobase Publishing |year=2008 |isbn=978-0-8160-5958-4 |p=[https://archive.org/details/firstvertebrates00holm/page/64 64]}}</ref> yang terdiri dari [[ikan]], [[amfibi]], [[reptil]], [[burung]], dan [[mamalia]].<ref>{{cite book |last=Rice |first=Stanley A. |title=Encyclopedia of evolution |url=https://archive.org/details/encyclopediaofev0000rice |publisher=Infobase Publishing |year=2007 |page=[https://archive.org/details/encyclopediaofev0000rice/page/75 75] |isbn=978-0-8160-5515-9}}</ref> Deuterostoma juga mencakup [[Hemichordata]] (cacing acorn).<ref>{{cite book |last1=Tobin |first1=Allan J. |last2=Dusheck |first2=Jennie |title=Asking about life |year=2005 |publisher=Cengage Learning |isbn=978-0-534-40653-0 |page=497}}</ref><ref>{{cite journal |title=Hemichordate genomes and deuterostome origins |url=http://www.nature.com/nature/journal/v527/n7579/full/nature16150.html |journal=Nature |date=26 November 2015 |pages=459–465 |volume=527 |issue=7579 |doi=10.1038/nature16150 |first=Oleg |last=Simakov |first2=Takeshi |last2=Kawashima |first3=Ferdinand |last3=Marlétaz |first4=Jerry |last4=Jenkins |first5=Ryo |last5=Koyanagi |first6=Therese |last6=Mitros |first7=Kanako |last7=Hisata |first8=Jessen |last8=Bredeson |first9=Eiichi |last9=Shoguchi |pmid=26580012 |pmc=4729200 |bibcode=2015Natur.527..459S |access-date=2018-04-17 |archive-date=2015-12-01 |archive-url=https://web.archive.org/web/20151201043718/http://www.nature.com/nature/journal/v527/n7579/full/nature16150.html |dead-url=no }}</ref>

Ecdysozoa adalah protostoma, dinamai berdasarkan [[Sifat fenotipik|sifat]] yang dimiliki bersama yaitu [[ekdisis]], pertumbuhan dengan ''moulting'' (berganti kulit).<ref>{{cite book |last=Dawkins |first=Richard |authorlink=Richard Dawkins |title=The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution |url=https://archive.org/details/ancestorstale00rich_0 |year=2005 |publisher=Houghton Mifflin Harcourt |isbn=978-0-618-61916-0 |page=[https://archive.org/details/ancestorstale00rich_0/page/381 381]}}</ref> Ecdysozoa mencakup filum hewan terbesar, Artropoda, yang mencakup serangga, laba-laba, kepiting, dan kerabatnya. Semua ini memiliki tubuh yang dibagi menjadi [[Segmentasi (biologi)|segmen berulang]], biasanya dengan ''appendage'' (anggota badan) yang berpasangan. Dua filum yang lebih kecil, [[Onychophora]] dan [[Tardigrada]], adalah kerabat dekat artropoda dan berbagi sifat-sifat tersebut. Ecdysozoa juga mencakup [[Nematoda]] atau cacing gilig, mungkin merupakan filum hewan terbesar kedua. Nematoda biasanya mikroskopis, dan terdapat di hampir setiap lingkungan di mana ada air;<ref>{{cite book |last1=Prewitt |first1=Nancy L. |last2=Underwood |first2=Larry S. |last3=Surver |first3=William |title=BioInquiry: making connections in biology |year=2003 |publisher=John Wiley |isbn=978-0-471-20228-8 |page=289}}</ref> beberapa merupakan parasit yang penting.<ref>{{cite book |title=Parasites in social insects |url=https://archive.org/details/parasitesinsocia0000schm |year=1998 |publisher=Princeton University Press |isbn=978-0-691-05924-2 |last=Schmid-Hempel |first=Paul |page=[https://archive.org/details/parasitesinsocia0000schm/page/n90 75]}}</ref> Filum yang lebih kecil yang berkerabat dengannya adalah [[Nematomorpha]] atau cacing bulu kuda, serta [[Kinorhyncha]], [[Priapulida]], dan [[Loricifera]]. Kelompok-kelompok ini memiliki selom tereduksi, yang disebut pseudoselom.<ref>{{cite book|author1=Miller, Stephen A. |author2=Harley, John P.|title=Zoology |url=https://books.google.com/books?id=BWZFAQAAIAAJ |year=2006 |publisher=McGraw-Hill Higher Education |page=173}}</ref>

Spiralia adalah kelompok besar protostoma yang berkembang dengan penyibakan spiral pada embrio awal.<ref name=Shankland>{{cite journal |pmid=10781038 |pmc=34316 |jstor=122407 |bibcode=2000PNAS...97.4434S |doi=10.1073/pnas.97.9.4434 |title = Evolution of the bilaterian body plan: What have we learned from annelids? |journal=Proceedings of the National Academy of Sciences |volume=97 |issue=9 |pages=4434–7 |year = 2000|last1 = Shankland |first1 = M. |last2=Seaver |first2=E. C. }}</ref> Filogeni Spiralia telah diperdebatkan, tetapi kelompok ini mengandung klad besar, superfilum [[Lophotrochozoa]], dan kelompok-kelompok filum yang lebih kecil seperti [[Rouphozoa]] yang mencakup [[Gastrotricha]] dan [[cacing pipih]]. Lophotrochozoa dan Rouphozoa dikelompokkan sebagai [[Platytrochozoa]], yang memiliki kelompok saudari, [[Gnathifera (klad)|Gnathifera]], yang mencakup [[rotifera]].<ref name=Struck2014>{{cite journal | last=Struck | first=Torsten H. | last2=Wey-Fabrizius | first2=Alexandra R. | last3=Golombek | first3=Anja | last4=Hering | first4=Lars | last5=Weigert | first5=Anne | last6=Bleidorn | first6=Christoph | last7=Klebow | first7=Sabrina | last8=Iakovenko | first8=Nataliia | last9=Hausdorf | first9=Bernhard | last10=Petersen | first10=Malte | last11=Kück | first11=Patrick | last12=Herlyn | first12=Holger | last13=Hankeln | first13=Thomas | title=Platyzoan Paraphyly Based on Phylogenomic Data Supports a Noncoelomate Ancestry of Spiralia | journal=Molecular Biology and Evolution | volume=31 | issue=7 | date=2014 | doi=10.1093/molbev/msu143 | pages=1833–1849 | pmid=24748651}}</ref><ref>{{Cite journal |last=Fröbius |first=Andreas C. |last2=Funch |first2=Peter |date=April 2017 |title=Rotiferan Hox genes give new insights into the evolution of metazoan bodyplans |url=http://www.nature.com/articles/s41467-017-00020-w |journal=Nature Communications |volume=8 |issue=1 |doi=10.1038/s41467-017-00020-w |access-date=2018-04-17 |archive-date=2017-05-21 |archive-url=https://web.archive.org/web/20170521081229/https://www.nature.com/articles/s41467-017-00020-w |dead-url=no }}</ref>

Pada [[era klasik]], [[Aristoteles]] [[Biologi Aristoteles|membagi hewan]],{{efn|Dalam karyanya ''[[Sejarah Hewan]]'' dan ''[[Bagian-Bagian Hewan]]''.}} berdasarkan pengamatannya sendiri, menjadi hewan dengan darah (kira-kira, vertebrata) dan hewan yang tidak berdarah. Hewan-hewan itu kemudian [[Scala naturae|diatur pada skala]] dari manusia (dengan darah, 2 kaki, jiwa rasional) turun ke tetrapoda yang melahirkan (dengan darah, 4 kaki, jiwa sensitif) dan kelompok lain seperti krustasea (tidak ada darah, banyak kaki, jiwa sensitif) turun ke makhluk yang mengalami [[generasi spontan]] seperti spons (tanpa darah, tanpa kaki, jiwa tumbuhan). Aristoteles tidak yakin apakah spons adalah hewan, yang dalam sistemnya harus memiliki sensasi, nafsu makan, dan pergerakan, atau tumbuhan, yang jelas bukan: dia tahu bahwa spons bisa merasakan sentuhan, dan akan berkontraksi jika hendak ditarik dari bebatuan mereka, tetapi bahwa spons berakar seperti tumbuhan dan tidak pernah bergerak.<ref>{{cite book |last=Leroi |first=Armand Marie |authorlink=Armand Marie Leroi |title=The Lagoon: How Aristotle Invented Science |titlelink=Aristotle's Lagoon |publisher=Bloomsbury |date=2014 |isbn=978-1-4088-3622-4 |pages=111–119[https://archive.org/details/lagoonhowaristot0000lero_m5a9/page/n126 111]–119, 270–271}}</ref>

Manusia mengeksploitasi sejumlah besar spesies hewan lain untuk makanan, baik dari spesies [[hewan ternak]] yang [[domestikasi|didomestikasi]] dan, terutama di laut, dengan berburu spesies liar.<ref name=FAOFish>{{cite web |url=http://www.fao.org/fishery/ |title=Fisheries and Aquaculture |publisher=FAO |accessdate=8 July 2016 |archive-date=2009-05-13 |archive-url=https://web.archive.org/web/20090513075213/http://www.fao.org/fishery |dead-url=no }}</ref><ref name=Economist/> Banyak spesies ikan laut [[Penangkapan ikan|ditangkap secara komersial]] untuk makanan. Sejumlah kecil spesies ikan [[Budi daya ikan|diternakkan secara komersial]].<ref name=FAOFish/><ref>{{cite book |last1=Helfman |first1=Gene S. |title=Fish Conservation: A Guide to Understanding and Restoring Global Aquatic Biodiversity and Fishery Resources |url=https://archive.org/details/fishconservation00helf |date=2007 |publisher=Island Press |isbn=1-59726-760-0 |page=[https://archive.org/details/fishconservation00helf/page/11 11]}}</ref><ref>{{cite web |title=World Review of Fisheries and Aquaculture |url=http://www.fao.org/docrep/016/i2727e/i2727e01.pdf |website=fao.org |publisher=FAO |accessdate=13 August 2015 |archive-date=2015-08-28 |archive-url=https://web.archive.org/web/20150828131307/http://www.fao.org/docrep/016/i2727e/i2727e01.pdf |dead-url=no }}</ref> Invertebrata termasuk [[sefalopoda]], [[krustasea]], dan moluska [[bivalvia]] atau [[gastropoda]] diburu atau dibudidayakan untuk dimakan.<ref>{{cite web | title=Shellfish climbs up the popularity ladder | url=http://www.highbeam.com/doc/1G1-85675992.html | publisher=HighBeam Research | accessdate=8 July 2016 | archive-date=2012-11-05 | archive-url=https://web.archive.org/web/20121105143157/http://www.highbeam.com/doc/1G1-85675992.html | dead-url=yes }}</ref> Ayam, sapi, domba, babi dan hewan lainnya dibesarkan sebagai hewan ternak di seluruh dunia.<ref name=Economist>{{cite web |title=Graphic detail Charts, maps and infographics. Counting chickens |url=https://www.economist.com/blogs/dailychart/2011/07/global-livestock-counts |publisher=[[The Economist]] |accessdate=23 June 2016 |date=27 July 2011 |archive-date=2016-07-15 |archive-url=https://web.archive.org/web/20160715181213/http://www.economist.com/blogs/dailychart/2011/07/global-livestock-counts |dead-url=no }}</ref><ref>{{cite web |author=Cattle Today |url=http://cattle-today.com/ |title=Breeds of Cattle at CATTLE TODAY |publisher=Cattle-today.com |accessdate=15 October 2013 |archive-date=2011-07-15 |archive-url=https://web.archive.org/web/20110715234745/http://cattle-today.com/ |dead-url=no }}</ref><ref>{{cite web |last1=Lukefahr |first1=S.D. |last2=Cheeke |first2=P.R. |title=Rabbit project development strategies in subsistence farming systems |url=http://www.fao.org/docrep/U4900T/u4900T0m.htm |publisher=[[Food and Agriculture Organization]] |accessdate=23 June 2016 |archive-date=2016-05-06 |archive-url=https://web.archive.org/web/20160506105314/http://www.fao.org/docrep/U4900T/u4900T0m.htm |dead-url=no }}</ref> Serat hewan seperti wol digunakan untuk membuat tekstil, sedangkan [[tendon]] binatang digunakan sebagai pengikat, dan kulit banyak digunakan untuk membuat sepatu dan barang-barang lainnya. Hewan diburu dan dibudidayakan untuk bulunya untuk membuat barang-barang seperti mantel dan topi.<ref>{{cite web |title=Animals Used for Clothing |url=http://www.peta.org/issues/animals-used-for-clothing/ |publisher=PETA |accessdate=8 July 2016 |archive-date=2016-06-29 |archive-url=https://web.archive.org/web/20160629152315/http://www.peta.org/issues/animals-used-for-clothing/ |dead-url=no }}</ref><ref>{{cite web |title=Ancient fabrics, high-tech geotextiles |url=http://www.naturalfibres2009.org/en/fibres/ |publisher=Natural Fibres |accessdate=8 July 2016 |archive-date=2019-05-15 |archive-url=https://web.archive.org/web/20190515155212/http://www.naturalfibres2009.org/en/fibres/ |dead-url=yes }}</ref> Zat warna termasuk [[carmine]] ([[cochineal]]),<ref>{{cite web |url=http://www.fao.org/docrep/v8879e/v8879e09.htm |title=Cochineal and Carmine |work=Major colourants and dyestuffs, mainly produced in horticultural systems |publisher=FAO |accessdate=June 16, 2015 |archive-date=2018-03-06 |archive-url=https://web.archive.org/web/20180306060330/http://www.fao.org/docrep/v8879e/V8879e09.htm |dead-url=no }}</ref><ref>{{cite web |url=http://www.fda.gov/ForIndustry/ColorAdditives/GuidanceComplianceRegulatoryInformation/ucm153038.htm |title=Guidance for Industry: Cochineal Extract and Carmine |publisher=FDA |accessdate=6 July 2016 |archive-date=2019-04-24 |archive-url=https://web.archive.org/web/20190424155253/https://www.fda.gov/ForIndustry/ColorAdditives/GuidanceComplianceRegulatoryInformation/ucm153038.htm |dead-url=no }}</ref> [[shellac]],<ref>{{cite news |title=How Shellac Is Manufactured |url=http://nla.gov.au/nla.news-article55073762 |accessdate=17 July 2015 |publisher=The Mail (Adelaide, SA : 1912–1954) |date=18 Dec 1937}}</ref><ref>{{cite journal |author1=Pearnchob, N. |author2=Siepmann, J. |author3=Bodmeier, R. |year=2003 |title=Pharmaceutical applications of shellac: moisture-protective and taste-masking coatings and extended-release matrix tablets |journal=Drug Development and Industrial Pharmacy |volume=29 |issue=8 |pages=925–938 |pmid=14570313 |doi=10.1081/ddc-120024188}}</ref> dan [[kermes]]<ref>{{cite book |last=Barber |first=E. J. W. |title=Prehistoric Textiles |url=https://archive.org/details/prehistorictexti0000barb |year=1991 |publisher=Princeton University Press |isbn=0-691-00224-X |pages=[https://archive.org/details/prehistorictexti0000barb/page/230 230]–231}}</ref><ref name="Munro214">{{cite book |author=Munro, John H. |title=Medieval Woollens: Textiles, Technology, and Organisation |url=https://archive.org/details/cambridgehistory0000unse_l9b6 |editor=Jenkins, David |year=2003 |work=The Cambridge History of Western Textiles |publisher=Cambridge University Press |isbn=0-521-34107-8 |pages=[https://archive.org/details/cambridgehistory0000unse_l9b6/page/214 214]–215}}</ref> dibuat dari tubuh serangga. [[Hewan pekerja]] termasuk sapi dan kuda digunakan untuk bekerja dan transportasi dari hari-hari pertama pertanian.<ref name="Pond2004">{{cite book |last=Pond |first=Wilson G. |title=Encyclopedia of Animal Science |url=https://books.google.com/books?id=1SQl7Ao3mHoC&pg=PA248 |year=2004 |publisher=CRC Press |isbn=978-0-8247-5496-9 |pages=248–250 |access-date=2018-03-23 |archive-date=2023-01-23 |archive-url=https://web.archive.org/web/20230123110032/https://books.google.com/books?id=1SQl7Ao3mHoC&pg=PA248 |dead-url=no }}</ref>

Hewan seperti lalat buah ''[[Drosophila melanogaster]]'' berperan besar dalam sains sebagai [[Organisme model|model eksperimental]].<ref>{{cite web |title=Genetics Research |url=http://www.aht.org.uk/cms-display/genetics.html |publisher=Animal Health Trust |accessdate=24 June 2016 |archive-date=2017-12-12 |archive-url=https://web.archive.org/web/20171212193051/http://www.aht.org.uk/cms-display/genetics.html |dead-url=yes }}</ref><ref>{{cite web |title=Drug Development |url=http://www.animalresearch.info/en/drug-development/ |publisher=Animal Research.info |accessdate=24 June 2016 |archive-date=2016-06-08 |archive-url=https://web.archive.org/web/20160608124406/http://www.animalresearch.info/en/drug-development/ |dead-url=no }}</ref><ref>{{cite web |title=Animal Experimentation |url=http://www.bbc.co.uk/ethics/animals/using/experiments_1.shtml |publisher=BBC |accessdate=8 July 2016 |archive-date=2019-12-31 |archive-url=https://web.archive.org/web/20191231222705/http://www.bbc.co.uk/ethics/animals/using/experiments_1.shtml |dead-url=no }}</ref><ref name="EUstatistics2013">{{cite web |title=EU statistics show decline in animal research numbers |url=http://speakingofresearch.com/2013/12/12/eu-statistics-show-decline-in-animal-research-numbers/ |publisher=Speaking of Research |year=2013 |accessdate=January 24, 2016 |archive-date=2017-10-06 |archive-url=https://web.archive.org/web/20171006162448/https://speakingofresearch.com/2013/12/12/eu-statistics-show-decline-in-animal-research-numbers/ |dead-url=no }}</ref> Hewan telah digunakan untuk membuat [[vaksin]] sejak penemuannya pada abad ke-18.<ref>{{cite web |title=Vaccines and animal cell technology |url=http://www.actip.org/library/vaccines-and-animal-cell-technology/ |publisher=Animal Cell Technology Industrial Platform |accessdate=9 July 2016 |archive-date=2016-07-13 |archive-url=https://web.archive.org/web/20160713184805/http://www.actip.org/library/vaccines-and-animal-cell-technology/ |dead-url=no }}</ref> Beberapa obat seperti obat kanker [[Yondelis]] didasarkan pada [[toksin]] atau molekul lain dari hewan.<ref>{{cite web |title=Medicines by Design |url=https://publications.nigms.nih.gov/medbydesign/chapter3.html |publisher=National Institute of Health |accessdate=9 July 2016 |archive-date=2016-06-04 |archive-url=https://web.archive.org/web/20160604214644/https://publications.nigms.nih.gov/medbydesign/chapter3.html |dead-url=yes }}</ref>

Orang-orang menggunakan [[anjing pemburu]] untuk membantu mengejar dan mengambil hewan,<ref>{{cite book |author=Fergus, Charles |title=Gun Dog Breeds, A Guide to Spaniels, Retrievers, and Pointing Dogs |url=https://archive.org/details/gundogbreedsguid0000ferg_d8w4 |publisher=The Lyons Press |date=2002 |isbn=1-58574-618-5}}</ref> dan [[burung pemangsa]] untuk menangkap burung dan mamalia,<ref>{{cite web |title=History of Falconry |url=http://www.thefalconrycentre.co.uk/bird-info/conservation/nocturnal-raptors/history-falconry/ |publisher=The Falconry Centre |accessdate=22 April 2016 |archive-date=2016-05-29 |archive-url=https://web.archive.org/web/20160529023926/http://thefalconrycentre.co.uk/bird-info/conservation/nocturnal-raptors/history-falconry/ |dead-url=yes }}</ref> sementara burung ''[[cormorant]]'' yang ditambatkan digunakan untuk menangkap ikan.<ref name="King2013">{{cite book |author=King, Richard J. |title=The Devil's Cormorant: A Natural History |url=https://books.google.com/books?id=ucGyAAAAQBAJ&pg=PA9 |date=2013 |publisher=University of New Hampshire Press |isbn=978-1-61168-225-0 |page=9}}</ref> [[Katak beracun]] digunakan untuk meracuni ujung [[Sumpit (senjata)|sumpit]].<ref name="amphibiaweb1">{{cite web |url=http://amphibiaweb.org/lists/Dendrobatidae.shtml |title=AmphibiaWeb–Dendrobatidae |publisher=AmphibiaWeb |accessdate=2008-10-10 |archive-date=2011-08-10 |archive-url=https://web.archive.org/web/20110810090554/http://amphibiaweb.org/lists/Dendrobatidae.shtml |dead-url=no }}</ref><ref>{{cite web | url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Dendrobatidae.html | title=Dendrobatidae | accessdate=9 July 2016 | author=Heying, H. | year=2003 | publisher=Animal Diversity Web | archive-date=2011-02-12 | archive-url=https://web.archive.org/web/20110212005358/http://animaldiversity.ummz.umich.edu/site/accounts/information/Dendrobatidae.html | dead-url=no }}</ref> Berbagai macam hewan dimanfaatkan sebagai hewan peliharaan, dari invertebrata seperti tarantula dan gurita, serangga termasuk [[belalang sembah]],<ref>{{cite web |title=Other bugs |url=http://www.keepinginsects.com/cockroaches-locusts-ants/ |publisher=Keeping Insects |accessdate=8 July 2016 |archive-date=2016-07-07 |archive-url=https://web.archive.org/web/20160707170022/http://www.keepinginsects.com/cockroaches-locusts-ants/ |dead-url=no }}</ref> reptil seperti [[ular]] dan [[bunglon]],<ref>{{cite web |last1=Kaplan |first1=Melissa |title=So, you think you want a reptile? |url=http://www.anapsid.org/parent.html |publisher=Anapsid.org |accessdate=8 July 2016 |archive-date=2016-07-03 |archive-url=https://web.archive.org/web/20160703115141/http://www.anapsid.org/parent.html |dead-url=no }}</ref> hingga burung, termasuk [[burung kenari]], [[parkit]] dan [[Bayan (burung)|bayan]].<ref>{{cite web |title=Pet Birds |url=http://www.humanesociety.org/animals/pet_birds/ |publisher=PDSA |accessdate=8 July 2016 |archive-date=2016-07-07 |archive-url=https://web.archive.org/web/20160707053516/http://www.humanesociety.org/animals/pet_birds/ |dead-url=yes }}</ref> Namun, spesies hewan peliharaan yang paling sering dipelihara adalah mamalia, yaitu [[anjing]], [[kucing]], dan [[kelinci]].<ref>{{cite web |url=http://www.shea-online.org/Portals/0/PDFs/Animals%20in%20Healthcare%20Facilities.pdf |title=Animals in Healthcare Facilities |year=2012 |deadurl=yes |archiveurl=https://web.archive.org/web/20160304102728/http://www.shea-online.org/Portals/0/PDFs/Animals%20in%20Healthcare%20Facilities.pdf |archivedate=4 March 2016 }}</ref><ref>{{cite web |last=The Humane Society of the United States |title=U.S. Pet Ownership Statistics |url=http://www.humanesociety.org/issues/pet_overpopulation/facts/pet_ownership_statistics.html |accessdate=27 April 2012 |archive-date=2012-04-07 |archive-url=https://web.archive.org/web/20120407193941/http://www.humanesociety.org/issues/pet_overpopulation/facts/pet_ownership_statistics.html |dead-url=yes }}</ref><ref>{{cite web |last=USDA |title=U.S. Rabbit Industry profile |url=http://www.aphis.usda.gov/animal_health/emergingissues/downloads/RabbitReport1.pdf |accessdate=10 July 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20131020161216/http://www.aphis.usda.gov/animal_health/emergingissues/downloads/RabbitReport1.pdf |archivedate=20 October 2013 |df= }}</ref> Ada ketegangan antara peran hewan sebagai sahabat manusia, dan keberadaan mereka sebagai [[Hak asasi hewan|individu dengan hak]] mereka sendiri.<ref>{{cite journal |title=The Role of Animals in Human Society |author=Plous, S. |date=1993 |doi=10.1111/j.1540-4560.1993.tb00906.x |journal=Journal of Social Issues |volume=49 |issue=1 |pages=1–9}}</ref> Berbagai macam hewan darat dan akuatik diburu [[Hewan dalam olahraga|untuk olahraga]].<ref>{{cite book |last1=Hummel |first1=Richard |title=Hunting and Fishing for Sport: Commerce, Controversy, Popular Culture |url=https://archive.org/details/huntingfishingfo0000humm |date=1994 |publisher=Popular Press |isbn=978-0-87972-646-1}}</ref>

Hewan telah menjadi [[Animal style|subyek seni]] dari zaman paling awal, baik sejarah, seperti di [[Mesir Kuno]], dan prasejarah, seperti dalam [[Gua Lascaux|lukisan gua di Lascaux]]. Lukisan hewan yang utama termasuk ''[[The Rhinoceros]]'' oleh [[Albrecht Dürer]] pada 1515, dan potret kuda ''[[Whistlejacket]]'' oleh [[George Stubbs]] pada [[Circa|c.]] 1762.<ref name="Jones">{{cite news |last1=Jones |first1=Jonathan |title=The top 10 animal portraits in art |url=https://www.theguardian.com/artanddesign/jonathanjonesblog/2014/jun/27/top-10-animal-portraits-in-art |accessdate=24 June 2016 |agency=[[The Guardian]] |date=27 June 2014 |archive-date=2016-05-18 |archive-url=https://web.archive.org/web/20160518105922/http://www.theguardian.com/artanddesign/jonathanjonesblog/2014/jun/27/top-10-animal-portraits-in-art |dead-url=no }}</ref> [[Artropoda dalam film|Serangga]], burung dan mamalia memainkan peran dalam sastra dan film,<ref>{{cite web |last1=Paterson |first1=Jennifer |title=Animals in Film and Media |url=http://www.oxfordbibliographies.com/view/document/obo-9780199791286/obo-9780199791286-0044.xml |publisher=Oxford Bibliographies |accessdate=24 June 2016 |date=29 October 2013 |doi=10.1093/obo/9780199791286-0044 |archive-date=2016-06-14 |archive-url=https://web.archive.org/web/20160614200642/http://www.oxfordbibliographies.com/view/document/obo-9780199791286/obo-9780199791286-0044.xml |dead-url=no }}</ref> seperti dalam film serangga raksasa.<ref name="GregersdotterHöglund2016">{{cite book |last1=Gregersdotter |first1=Katarina |last2=Höglund |first2=Johan |last3=Hållén |first3=Nicklas |title=Animal Horror Cinema: Genre, History and Criticism |url=https://books.google.com/books?id=hV-hCwAAQBAJ&pg=PA147 |date=2016 |publisher=Springer |isbn=978-1-137-49639-3 |page=147}}</ref><ref name="WarrenThomas2009">{{cite book |last1=Warren |first1=Bill |last2=Thomas |first2=Bill |title=Keep Watching the Skies!: American Science Fiction Movies of the Fifties, The 21st Century Edition |url=https://books.google.com/books?id=B7kUCwAAQBAJ&pg=PT32 |date=2009 |publisher=McFarland |isbn=978-1-4766-2505-8 |page=32}}</ref><ref name="Crouse2008">{{cite book |last=Crouse |first=Richard |title=Son of the 100 Best Movies You've Never Seen |url=https://books.google.com/books?id=B5alnowvF3sC&pg=PT200 |year=2008 |publisher=ECW Press |isbn=978-1-55490-330-6 |page=200}}</ref> Hewan, termasuk [[Serangga dalam mitologi|serangga]]<ref name=Hearn/> dan mamalia<ref name=TFL/> berperan dalam mitologi dan agama. Baik di Jepang maupun Eropa, [[kupu-kupu]] dilihat sebagai personifikasi jiwa seseorang,<ref name=Hearn>{{cite book | last=Hearn | first=Lafcadio | authorlink=Lafcadio Hearn | year=1904 | title=Kwaidan: Stories and Studies of Strange Things | titlelink=Kwaidan: Stories and Studies of Strange Things | publisher=Dover | isbn=0-486-21901-1}}</ref><ref>{{cite web | url=http://quod.lib.umich.edu/cgi/t/text/text-idx?c=did;cc=did;rgn=main;view=text;idno=did2222.0001.694 | title=Butterfly | work=Encyclopedia of Diderot and D'Alembert | accessdate=10 July 2016 | archive-date=2016-08-11 | archive-url=https://web.archive.org/web/20160811042437/http://quod.lib.umich.edu/cgi/t/text/text-idx?c=did;cc=did;rgn=main;view=text;idno=did2222.0001.694 | dead-url=no }}</ref><ref>Hutchins, M., Arthur V. Evans, Rosser W. Garrison and Neil Schlager (Eds) (2003) Grzimek's Animal Life Encyclopedia, 2nd edition. Volume 3, Insects. Gale, 2003.</ref> sementara [[Scarabaeidae|kumbang scarab]] dianggap sakral di Mesir kuno.<ref>{{cite book |author=Ben-Tor, Daphna |title=Scarabs, A Reflection of Ancient Egypt |location=Jerusalem |publisher= |date=1989 |isbn=965-278-083-9 |page=8}}</ref> Di antara mamalia, [[Sapi dalam agama dan mitologi|sapi]],<ref>{{cite web |last1=Biswas |first1=Soutik |title=Why the humble cow is India's most polarising animal |url=http://www.bbc.co.uk/news/world-asia-india-34513185 |publisher=BBC |accessdate=9 July 2016 |archive-date=2019-10-30 |archive-url=https://web.archive.org/web/20191030140248/https://www.bbc.co.uk/news/world-asia-india-34513185 |dead-url=no }}</ref> [[Rusa dalam mitologi|rusa]],<ref name=TFL>{{cite web |title=Deer |url=http://treesforlife.org.uk/forest/mythology-folklore/deer/ |publisher=[[Trees for Life (Scotland)|Trees for Life]] |accessdate=23 June 2016 |archive-date=2016-06-14 |archive-url=https://web.archive.org/web/20160614200842/http://treesforlife.org.uk/forest/mythology-folklore/deer/ |dead-url=no }}</ref> [[Pemujaan kuda|kuda]],<ref>{{cite book |title=Hayagrīva: The Mantrayānic Aspect of Horse-cult in China and Japan |publisher=Brill Archive |page=9 |author=Robert Hans van Gulik}}</ref> [[Penggambaran budaya dari singa|singa]],<ref>{{cite web |last1=Grainger |first1=Richard |title=Lion Depiction across Ancient and Modern Religions |url=https://lionalert.org/page/Lion_Depiction_Across_Ancient_and_Modern_Religions |publisher=ALERT |accessdate=6 July 2016 |date=24 June 2012 |deadurl=yes |archiveurl=https://web.archive.org/web/20160923134807/https://lionalert.org/page/Lion_Depiction_Across_Ancient_and_Modern_Religions |archivedate=23 September 2016 }}</ref> [[Kelelawar#Makna dalam budaya|kelelawar]]<ref name=ReadGonzalez>{{cite book |last1=Read |first1=Kay Almere |last2=Gonzalez |first2=Jason J. |year=2000 |title=Mesoamerican Mythology |publisher=Oxford University Press |pages=132–134}}</ref> dan [[Serigala dalam folklor, agama dan mitologi|serigala]]<ref>{{cite book |author=McCone, Kim R. |title=Hund, Wolf, und Krieger bei den Indogermanen |editor=Meid, W. |work=Studien zum indogermanischen Wortschatz |publisher= |location=Innsbruck |date=1987 |pages=101–154}}</ref> adalah subjek mitos dan pemujaan. [[Zodiak|Tanda-tanda zodiak Barat]] dan [[Shio|Cina]] didasarkan pada hewan.<ref>Lau, Theodora, ''The Handbook of Chinese Horoscopes'', pp. 2–8, 30–5, 60–4, 88–94, 118–24, 148–53, 178–84, 208–13, 238–44, 270–78, 306–12, 338–44, Souvenir Press, New York, 2005</ref><ref name="Tester1987">{{cite book |last=Tester |first=S. Jim |title=A History of Western Astrology |url=https://books.google.com/books?id=L0HSvH96alIC&pg=PA31 |year=1987 |publisher=Boydell & Brewer |isbn=978-0-85115-446-6 |pages=31–33 and passim}}</ref>

* {{cite book|last=Solomon, et. al.|date=1993|title=Biology, 3rd ed.|publisher=Saunders-College Publishing,|location=ForthFort Worth}}