Over 1.5 million
living animal
species have been
described, of which around 1.05 million are
insects, over 85,000 are
molluscs, and around 65,000 are
vertebrates. 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 complex
ecologies and
interactions with each other and their environments, forming intricate
food webs. The scientific study of animals is known as
zoology, and the study of animal behaviors is known as
ethology.
The thylacine (/ˈθaɪləsiːn/;
binomial nameThylacinus cynocephalus), also commonly known as the Tasmanian tiger or Tasmanian wolf, is an
extinct carnivorous
marsupial that was native to the
Australian mainland and the islands of
Tasmania and
New Guinea. The thylacine died out in New Guinea and mainland Australia around 3,600–3,200 years ago, prior to the arrival of Europeans, possibly because of the introduction of the
dingo, whose earliest record dates to around the same time, but which never reached Tasmania. Prior to European settlement, around 5,000 remained in the wild on Tasmania. Beginning in the nineteenth century, they were perceived as a threat to the livestock of farmers and
bounty hunting was introduced. The last known of its species died in 1936 at
Hobart Zoo in Tasmania. The thylacine is widespread in popular culture and is a
cultural icon in Australia.
The thylacine was known as the Tasmanian tiger because of the dark transverse stripes that radiated from the top of its back, and it was called the Tasmanian wolf because it resembled a medium- to large-sized
canid. The name thylacine is derived from thýlakos meaning "pouch" and ine meaning "pertaining to", and refers to the
marsupial pouch. Both sexes had a pouch. The females used theirs for rearing young, and the males used theirs as a protective sheath, covering the
external reproductive organs. The animal had a stiff tail and could open its jaws to an unusual extent. Recent studies and anecdotal evidence on its predatory behaviour suggest that the thylacine was a solitary
ambush predator specialised in hunting small to medium-sized prey. Accounts suggest that in the wild, it fed on small birds and mammals. It was the only member of the genus Thylacinus and family
Thylacinidae to have survived until modern times. Its closest living relatives are the other members of
Dasyuromorphia including the
Tasmanian devil, from which it is estimated to have split 42–36 million years ago. (Full article...)
An illustration of various Pulmonata (and one predator
arthropod in the lower right), an informal group of
snails and
slugs characterized by the ability to breathe air, by virtue of having a
pallial lung instead of a
gill, or gills. Pulmonata was previously a formal
taxon but lost its status as one in 2010. The group includes many land and freshwater families, and several marine families. Most species have a shell, but no
operculum, although the group does also include several shell-less slugs. Pulmonates are
hermaphroditic, and some groups possess
love darts.
Haliotis laevigata is a species of marine
mollusc in the family
Haliotidae,
endemic to Tasmania and the southern and western coasts of Australia. This picture shows five views of a green H. laevigata shell, 7.5 centimetres (3.0 in) in length. The holes in the shell, characteristic of
abalones, are respiratory apertures for venting water from the gills and for releasing sperm and eggs into the
water column.
Anatomical diagram of an adult female
chambered nautilus, the best known species of nautilus, a "
living fossil" related to the octopuses. The animal has a primitive brain that forms a ring around its
oesophagus, has four gills (all other
cephalopods have only two), and can only move shell-first (seemingly "backwards") by pumping water out through its funnel. The shell and tentacles are shown here as shadows.
The bird-cherry ermine (Yponomeuta evonymella) is a species of moth in the family
Yponomeutidae, native to Europe and parts of Asia. The caterpillars are gregarious and feed on the leaves of the
bird cherry tree, forming silken webbing for their own protection. They create further webbing on the trunk and near the base of the tree, which hides them as they
pupate. This photograph shows one of many bird-cherry ermine caterpillar nests on a tree in
Lahemaa National Park, Estonia. In some years, they are so numerous that they can completely strip a tree of its foliage.
The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the
Greek πλατύ, platy, meaning "flat" and ἕλμινς (root: ἑλμινθ-), helminth-, meaning "worm") are a
phylum of relatively simple
bilaterian,
unsegmented, soft-bodied
invertebrates. Being
acoelomates (having no
body cavity), and having no specialised
circulatory and
respiratoryorgans, they are restricted to having flattened shapes that allow
oxygen and nutrients to pass through their bodies by
diffusion. The digestive cavity has only one opening for both ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food cannot be processed continuously. (Full article...)
Velodona togata is the only species in the
octopus genus Velodona; the genus and species names come from the large membranes that connect its arms. It was first described by
Carl Chun in his book Die Cephalopoden (from which this illustration is taken) in 1915. A second subspecies was described by
Guy Coburn Robson in 1924.
Plate 5 from
Ernst Haeckel's Kunstformen der Natur, showing a variety of calcareous sponges, a
class of about 400 marine
sponges that are found mostly in shallow tropical waters worldwide. Calcareous sponges vary from radially symmetrical vase-shaped body types to colonies made up of a meshwork of thin tubes, or irregular massive forms. The skeleton has either a mesh or honeycomb structure.
Eutropis macularia, the bronze grass skink, is a species of lizard in the
skink family, Scincidae, native to South and Southeast Asia. It lives in both deciduous and evergreen forests, in plantations, in grasslands, and in rocky areas with scattered trees. The species is active in both the day and the night, feeding on insects and other invertebrates. This bronze grass skink was photographed on a tree trunk on the island of
Don Det in Laos.
The golden toad (Bufo periglenes) is an
extinct species of
true toad that was once abundant in a small region of high-altitude cloud-covered
tropical forests, about 30 km2 (12 sq mi) in area, above the city of
Monteverde, Costa Rica. The last reported sighting of a golden toad was on 15 May 1989. Its sudden extinction may have been caused by
chytrid fungus and extensive
habitat loss.
Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a
phylum of simple,
aquaticinvertebrate animals, nearly all living in sedentary
colonies. Typically about 0.5 millimetres (1⁄64 in) long, they have a special feeding structure called a
lophophore, a "crown" of tentacles used for
filter feeding. Most
marine bryozoans live in tropical waters, but a few are found in
oceanic trenches and polar waters. The bryozoans are classified as the
marine bryozoans (Stenolaemata),
freshwater bryozoans (Phylactolaemata), and
mostly-marine bryozoans (Gymnolaemata), a few members of which prefer
brackish 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 four
genera; Aethozooides, Aethozoon, Franzenella and Monobryozoon). The latter having a statocyst‐like organ with a supposed excretory function. (Full article...)
A soybean cyst nematode (Heterodera glycines), together with an egg, as viewed through a low-temperature
scanning electron microscope at 1000x magnification. This
nematode infects the roots of soybeans, and the female nematode eventually becomes a
cyst. Infection causes various symptoms that may include
chlorosis of the leaves and stems, root necrosis, loss in seed yield and suppression of root and shoot growth.
Brittle stars, serpent stars, or ophiuroids (from
Latin ophiurus 'brittle star'; from
Ancient Greekὄφις (óphis) 'serpent', and οὐρά (ourá) 'tail'; referring to the serpent-like arms of the brittle star) are
echinoderms in the class Ophiuroidea, closely related to
starfish. 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...)
The paddyfield pipit (Anthus rufulus) is a
passerine bird in the family
Motacillidae, comprising
pipits,
longclaws and
wagtails. 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. This A. r. rufulus individual was photographed in
Kanha Tiger Reserve, in the Indian state of
Madhya Pradesh.
Entries here consist of
Good and
Featured articles, which meet a core set of high editorial standards.
Mustelidae is a
family of
mammals in the
orderCarnivora, which includes
weasels,
badgers,
otters,
ferrets,
martens,
minks, and
wolverines, and many other
extant and
extinctgenera. A member of this family is called a mustelid; Mustelidae is the largest family in Carnivora, and its extant species are divided into eight
subfamilies. They are found on all continents except Antarctica and Australia, and are a diverse family; sizes range, including tails, from the widespread 17 cm (7 in)
least weasel to the 1.8-meter (6 ft)
giant otter of Amazonian South America. Habitats vary widely as well, from the
arborealmarten to the
fossorialEuropean badger to the
marinesea otter. Population sizes are largely unknown, though two species, the
sea mink and
Japanese otter, were hunted to extinction in 1894 and 1979, respectively, and several other species are
endangered. Some species have been domesticated, e.g. the
ferret and some populations of the South American
tayra. Mustelidae is one of the oldest families in Carnivora; early mustelids first appeared around 28–33 million years ago.
The 23 genera and 63 extant species of Mustelidae are split into 8 subfamilies:
Guloninae, martens and wolverines;
Helictidinae, ferret-badgers;
Ictonychinae, African polecats and
grisons;
Lutrinae, otters;
Melinae, Eurasian badgers;
Mellivorinae, the
honey badger;
Mustelinae, weasels and minks; and
Taxidiinae, the
American badger. In addition to the extant subfamilies, Mustelidae includes three extinct subfamilies designated as Leptarctinae, Mustelavinae, and
Oligobuninae. Extinct species have also been placed into all of the extant subfamilies besides Helictidinae, in both extant and extinct genera; around 200 extinct Mustelidae species have been found, as well as fossil genera not given a species name, though due to ongoing research and discoveries the exact number and categorization is not fixed. (Full article...)
Image 4Simplified schematic of an island's fauna – all its animal species, highlighted in boxes (from Fauna)
Image 5The red
pigment in a flamingo's plumage comes from its diet of shrimps, which get it from microscopic algae. (from Animal coloration)
Image 6Non-bilaterians include sponges (centre) and corals (background). (from Animal)
Image 7The microscopic cave snail Zospeum tholussum, found at depths of 743 to 1,392 m (2,438 to 4,567 ft) in the
Lukina Jama–Trojama cave system of
Croatia, is completely blind with a translucent shell (from Fauna)
Image 8A brilliantly-coloured
oriental sweetlips fish (Plectorhinchus vittatus) waits while two boldly-patterned
cleaner 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 the
cleaner fish signal their availability for
cleaning service, rather than as prey (from Animal coloration)
Image 9The bilaterian gut develops in two ways. In many
protostomes, the blastopore develops into the mouth, while in
deuterostomes it becomes the anus. (from Animal)
Image 39The
hawk-cuckoo resembles a predatory
shikra, giving the cuckoo time to lay eggs in a songbird's nest unnoticed (from Animal coloration)
Image 40A
praying mantis in
deimatic or threat pose displays conspicuous patches of colour to startle potential predators. This is not warning coloration as the insect is palatable. (from Animal coloration)
Image 42Idealised
bilaterian body plan. With an elongated body and a direction of movement the animal has head and tail ends. Sense organs and mouth form the
basis of the head. Opposed circular and longitudinal muscles enable
peristaltic motion. (from Animal)
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 the
taxonomic hierarchy, 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 of
DNA barcoding to taxonomy further complicates this; a 2016 barcoding analysis estimated a total count of nearly 100,000
insect species for
Canada alone, and extrapolated that the global insect fauna must be in excess of 10 million species, of which nearly 2 million are in a single fly family known as gall midges (
Cecidomyiidae).[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.