Over 1.5 millionlivinganimalspecieshave beendescribed,of which around 1.05 million areinsects,over 85,000 aremolluscs,and around 65,000 arevertebrates.It has been estimated there are as many as 7.77 million animal species on Earth. Animal body lengths range from 8.5 μm (0.00033 in) to 33.6 m (110 ft). They have complexecologiesandinteractionswith each other and their environments, forming intricatefood webs.The scientific study of animals is known aszoology,and the study of animal behaviors is known asethology.
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Thekoala(Phascolarctos cinereus), sometimes called thekoala bear,is anarborealherbivorousmarsupialnative to Australia. It is the onlyextantrepresentative of thefamilyPhascolarctidae.Its closest living relatives are thewombats.The koala is found in coastal areas of the island's eastern and southern regions, inhabitingQueensland,New South Wales,Victoria,andSouth Australia.It is easily recognisable by its stout, tailless body and large head with round, fluffy ears and large, dark nose. The koala has a body length of 60–85 cm (24–33 in) and weighs 4–15 kg (8.8–33.1 lb).Furcolour ranges from silver grey to chocolate brown. Koalas from the northern populations are typically smaller and lighter in colour than their counterparts further south. These populations possibly are separatesubspecies,but this is disputed.
Koalas typically inhabit openEucalyptuswoodland, as the leaves of these trees make up most of their diet. This eucalypt diet has low nutritional and caloric content and contains toxic compounds that deter most other mammals from feeding on it. Koalas are largelysedentaryand sleep up to twenty hours a day. They are asocial, only mothersbondto dependent offspring. Adult malescommunicatewith bellows that intimidate rivals and attract mates. Males mark their presence with secretions fromscent glandslocated on their chests. Like other marsupials, koalas give birth to young known asjoeysat a very early stage of development. They crawl into their mothers'pouches,where they live for their first six to seven months. They are fullyweanedaround a year old. Koalas have few natural predators and parasites, but are threatened bypathogenssuch asChlamydiaceaebacteria andkoala retrovirus.(Full article...)
Theflatworms,flat worms,Platyhelminthes,orplatyhelminths(from theGreekπλατύ,platy,meaning "flat" and ἕλμινς (root: ἑλμινθ-),helminth-,meaning "worm") are aphylumof relatively simplebilaterian,unsegmented,soft-bodiedinvertebrates.Beingacoelomates(having nobody cavity), and having no specialisedcirculatoryandrespiratoryorgans,they are restricted to having flattened shapes that allowoxygenand nutrients to pass through their bodies bydiffusion.The digestive cavity has only one opening for both ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, thefoodcan not be processed continuously. (Full article...)
Theplains zebra(Equus quagga,subspeciesGrant's zebrapictured) is the most common and geographically widespread species ofzebra.It ranges from the south of Ethiopia through East Africa to as far south as Angola and eastern South Africa. The plains zebra is mid-sized, smaller on average than the other two zebra species, and thick-bodied with relatively short legs. Adults of both sexes can stand from 1.1 to 1.47 m (3.6 to 4.8 ft) high at the shoulder, are 2 to 2.5 m (6.6 to 8.2 ft) long (excluding the tail), and weigh 175 to 387 kg (386 to 853 lb), with males slightly heavier than females.
Amacroview of aGonia capitataflyfeeding onhoney,showing itsproboscisandpedipalps(the two appendages protruding from the proboscis), two types ofinsect mouthparts.The proboscis actually comprises the labium, a quadrupedal structure, and a sponge-like labellum at the end. Flies eat solid food by secretingsalivaand dabbing it over the food item. As the saliva dissolves the food, the solution is then drawn up into the mouth as a liquid. The labellum's surface is covered by minute food channels which form a tube leading to theesophagus,and food is drawn up the channels bycapillary action.
Cymbiola nobilisis a species ofsea snailin thefamilyVolutidae.Found in the Pacific Ocean, from Taiwan to Singapore, it averages 6 centimetres (2.4 in) in length; females arelarger than males.Because the shell is commonly collected, there has been an overharvesting of the snail, and it is now consideredvulnerable.
Thegolden toad(Bufo periglenes) is anextinctspecies oftrue toadthat was once abundant in a small region of high-altitude cloud-coveredtropical forests,about 30 km2(12 sq mi) in area, above the city ofMonteverde,Costa Rica. The last reported sighting of a golden toad was on15 May1989. Its sudden extinction may have been caused bychytrid fungusand extensivehabitat loss.
Bryozoa(also known as thePolyzoa,Ectoproctaor commonly asmoss animals) are aphylumof simple,aquaticinvertebrateanimals, nearly all living in sedentarycolonies.Typically about0.5 millimetres (1⁄64in) long, they have a special feeding structure called alophophore,a "crown" of tentacles used forfilter feeding.Mostmarinebryozoans live in tropical waters, but a few are found inoceanic trenchesand polar waters. The bryozoans are classified as themarine bryozoans(Stenolaemata),freshwater bryozoans(Phylactolaemata), andmostly-marine bryozoans(Gymnolaemata), a few members of which preferbrackish water.5,869living species are known. Originally all of the crown group Bryozoa were colonial, but as an adaptation to a mesopsammal (interstitial spaces in marine sand) life or to deep-sea habitats, secondarily solitary forms have since evolved. Solitary species has been described in fourgenera;Aethozooides,Aethozoon,FranzenellaandMonobryozoon). The latter having a statocyst-like organ with a supposed excretory function. (Full article...)
Brittle stars,serpent stars,orophiuroids(fromLatinophiurus'brittle star'; fromAncient Greekὄφις(óphis)'serpent' andοὐρά(ourá)'tail'; referring to the serpent-like arms of the brittle star) areechinodermsin the classOphiuroidea,closely related tostarfish.They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60 cm (24 in) in length on the largest specimens. (Full article...)
Liguus virgineus,also known as the candy cane snail, is a species of snail in the familyOrthalicidae.It is native to the Caribbean island ofHispaniola,in the nations of Haiti and the Dominican Republic. There have also been at least three reports of living specimens being found in theFlorida Keysof the United States. The snail lives on trees and feeds on moss, fungi and microscopic algae covering the bark.
Theleopard shark(Triakis semifasciata) is a species ofhound sharkfound along thePacificcoast ofNorth Americafrom the U.S. state ofOregontoMazatlánin Mexico. Typically measuring 1.2–1.5 m (3.9–4.9 ft) long, this slender-bodied shark is characterized by black saddle-like markings and large spots over its back.
Representativedinosaursof theHadrosauroideasuperfamily.ThefamilyHadrosauridaecontains the dinosaurs commonly known as "duck-billed" dinosaurs. They were ubiquitousherbivoresduring theCretaceousperiod, and prey totheropodasuch asTyrannosaurus.The individual drawings represent typicalgenera.All these groups were alive in the late Cretaceous, and are generally known only from a single fossil site. Animals are shown to scale.
Thebrown pelican(Pelecanus occidentalis) is a bird of the pelican family,Pelecanidae,one of three species found in the Americas and one of two that feed by diving into water. This photograph shows a juvenile brown pelican gliding over the Pacific Ocean atBodega Head,California.
After hatching, the pelican chicks are fed onregurgitatedpredigested fish and take about two months to fledge. When they leave the nest, they are at first unable to fly and take wing several weeks later. When the parents cease to feed them, some six months later, each will have consumed around 70 kg (150 lb) of fish. The juvenile brown pelican does not acquire adult plumage until three years of age, when the feathers on the neck become paler, the upperparts striped, the wing feathers grayer, and the belly acquires dark spots.
TheCommon Brushtail Possum(Trichosurus vulpecula) is the largestpossumspecies and is perhaps the most widespreadmammalin Australia. It grows to about 32–58 cm (13–23 in) in length, with an additional 24–40 cm (9–16 in) for itsprehensiletail (seen here hanging below the branch). It is mainly afolivore,but has been known to eat small mammals such as rats. It is common in cities, having adapted well to human habitation.
Thepaddyfield pipit(Anthus rufulus) is apasserinebird in the familyMotacillidae,comprisingpipits,longclawsandwagtails.About 15 cm (6 in) in length and native to southern Asia, its plumage in both sexes is greyish-brown above and paler yellowish-brown below, with dark streaking on the breast. A bird of open country, pasture and cultivated fields, it sometimes makes short flights, but mostly runs on the ground, foraging for insects and other small invertebrates. The paddyfield pipit builds its cup-shaped nest in a concealed location on the ground, and may have two or more broods in a year. ThisA. r. rufulusindividual was photographed inKanha Tiger Reserve,in the Indian state ofMadhya Pradesh.
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The PDSA Dickin Medal (obverse)
ThePDSA Dickin Medalwas instituted in 1943 in the United Kingdom byMaria Dickinto honour the work of animals in World War II. It is a bronzemedallion,bearing the words "For Gallantry" and "We Also Serve" within alaurel wreath,carried on a ribbon of striped green, dark brown, and pale blue. It is awarded to animals that have displayed "conspicuous gallantry or devotion to duty while serving or associated with any branch of the Armed Forces or Civil Defence Units". The award is commonly referred to as "the animals'Victoria Cross".
Maria Dickin was the founder of thePeople's Dispensary for Sick Animals(PDSA), a Britishveterinarycharity. She established the award for any animal displaying conspicuous gallantry and devotion to duty whilst serving withBritish Empirearmed forces or civil emergency services. The medal was awarded 54 times between 1943 and 1949 – to 32pigeons,18dogs,3horses,and aship's cat– to acknowledge actions of gallantry or devotion during theSecond World Warand subsequent conflicts. (Full article...)
...that theSouthern Giant Petrelis the leading predator to theEmperor Penguin,and may be responsible for up to 34% of chick deaths in some colonies?
...that some goats freeze for ten seconds whenever startled due to the genetic condition known asmyotonia congenita,and have thus been dubbed "fainting goats"?
Image 2This frog changes its skin colour to control its temperature. (fromAnimal coloration)
Image 3Apraying mantisindeimaticor threat pose displays conspicuous patches of colour to startle potential predators. This is not warning coloration as the insect is palatable. (fromAnimal coloration)
Image 4Theblue whaleis the largest animal that has ever lived. (fromAnimal)
Image 5Kelp gullchicks peck at red spot on mother's beak to stimulate the regurgitating reflex. (fromZoology)
Image 11A brilliantly-colouredoriental sweetlipsfish (Plectorhinchus vittatus) waits while two boldly-patternedcleaner wrasse(Labroides dimidiatus) pick parasites from its skin. The spotted tail and fin pattern of the sweetlips signals sexual maturity; the behaviour and pattern of thecleaner fishsignal their availability forcleaning service,rather than as prey (fromAnimal coloration)
Image 24The bilaterian gut develops in two ways. In manyprotostomes,the blastopore develops into the mouth, while indeuterostomesit becomes the anus. (fromAnimal)
Image 41Idealisedbilaterianbody plan. With an elongated body and a direction of movement the animal has head and tail ends. Sense organs and mouth form thebasis of the head.Opposed circular and longitudinal muscles enableperistaltic motion.(fromAnimal)
Image 42The microscopic cave snailZospeum tholussum,found at depths of 743 to 1,392 m (2,438 to 4,567 ft) in theLukina Jama–Trojamacave system ofCroatia,is completely blind with a translucent shell (fromFauna)
Image 43Animals are unique in having the ball of cells of the earlyembryo(1) develop into a hollow ball orblastula(2). (fromAnimal)
Image 44Linnaeus's table of the animal kingdom from the first edition ofSystema Naturae(1735) (fromZoology)
Image 45Agun dogretrieving a duck during a hunt (fromAnimal)
The following table lists estimated numbers of described extant species for the animal groups with the largest numbers of species,[1]along with their principal habitats (terrestrial, fresh water,[2]and marine),[3]and free-living or parasitic ways of life.[4]Species estimates shown here are based on numbers described scientifically; much larger estimates have been calculated based on various means of prediction, and these can vary wildly. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million.[5]Using patterns within thetaxonomichierarchy, the total number of animal species—including those not yet described—was calculated to be about 7.77 million in 2011.[6][7][a]
^The application ofDNA barcodingto taxonomy further complicates this; a 2016 barcoding analysis estimated a total count of nearly 100,000insectspecies forCanadaalone, and extrapolated that the global insect fauna must be in excess of 10 million species, of which nearly 2 million are in a single fly family known as gall midges (Cecidomyiidae).[8]
^Stork, Nigel E. (January 2018). "How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth?".Annual Review of Entomology.63(1): 31–45.doi:10.1146/annurev-ento-020117-043348.PMID28938083.S2CID23755007.Stork notes that 1m insects have been named, making much larger predicted estimates.
^abcdNicol, David (June 1969). "The Number of Living Species of Molluscs".Systematic Zoology.18(2): 251–254.doi:10.2307/2412618.JSTOR2412618.
^Sluys, R. (1999). "Global diversity of land planarians (Platyhelminthes, Tricladida, Terricola): a new indicator-taxon in biodiversity and conservation studies".Biodiversity and Conservation.8(12): 1663–1681.doi:10.1023/A:1008994925673.S2CID38784755.
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