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.
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Adult female red back spider
The redback spider (Latrodectus hasselti), also known as the Australian black widow, is a species of highly venomous spider believed to originate in South Australia or adjacent Western Australian deserts, but now found throughout Australia, Southeast Asia and New Zealand, with colonies elsewhere outside Australia. It is a member of the cosmopolitan genus Latrodectus, the widow spiders. The adult female is easily recognised by her spherical black body with a prominent red stripe on the upper side of her abdomen and an hourglass-shaped red/orange streak on the underside. Females usually have a body length of about 10 millimetres (0.4 in), while the male is much smaller, being only 3–4 mm (0.12–0.16 in) long.
Mainly nocturnal, the female redback lives in an untidy web in a warm sheltered location, commonly near or inside human residences. It preys on insects, spiders and small vertebrates that become ensnared in its web. It kills its prey by injecting a complex venom through its two fangs when it bites, before wrapping them in silk and sucking out the liquefied insides. Often, it first squirts its victim with what resembles 'superglue' from its spinnerets, immobilising the prey by sticking the victim's limbs and appendages to its own body. The redback spider then trusses the victim with silk. Once its prey is restrained, it is bitten repeatedly on the head, body and leg segments and is then hauled back to the redback spider's retreat. Sometimes a potentially dangerous victim can be left to struggle for hours until it is exhausted enough to approach safely. Male spiders and spiderlings often live on the periphery of the female spiders' web and steal leftovers. Other species of spider and parasitoid wasps prey on this species. The redback is one of a number of arachnids that usually display sexual cannibalism while mating. (Full article...)
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 sperm whale is the largest toothed animal on Earth. The species was hunted extensively by humans throughout history, until protected by a worldwide moratorium on whaling starting in 1985–86.
A macro view of a Gonia capitatafly feeding on honey, showing its proboscis and pedipalps (the two appendages protruding from the proboscis), two types of insect mouthparts. The proboscis actually comprises the labium, a quadrupedal structure, and a sponge-like labellum at the end. Flies eat solid food by secreting saliva and 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 the esophagus, and food is drawn up the channels by capillary action.
The Common Brushtail Possum (Trichosurus vulpecula) is the largest possum species and is perhaps the most widespread mammal in Australia. It grows to about 32–58 cm (13–23 in) in length, with an additional 24–40 cm (9–16 in) for its prehensile tail (seen here hanging below the branch). It is mainly a folivore, but has been known to eat small mammals such as rats. It is common in cities, having adapted well to human habitation.
The leopard shark (Triakis semifasciata) is a species of hound shark found along the Pacific coast of North America from the U.S. state of Oregon to Mazatlán in 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.
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 can not be processed continuously. (Full article...)
The common clam worm (Alitta succinea) is a widely distributed species of marine polychaete worm. The photograph shows an epitoke specimen, the worm having turned into a form capable of reproduction. After releasing its sperm or eggs, the animal will die.
Representative dinosaurs of the Hadrosauroideasuperfamily. The familyHadrosauridae contains the dinosaurs commonly known as "duck-billed" dinosaurs. They were ubiquitous herbivores during the Cretaceous period, and prey to theropoda such as Tyrannosaurus. The individual drawings represent typical genera. All these groups were alive in the late Cretaceous, and are generally known only from a single fossil site. Animals are shown to scale.
The coconut octopus (Amphioctopus marginatus) is a medium-sized cephalopod found in tropical waters of the western Pacific Ocean. It commonly preys upon shrimp, crabs, and clams, and displays unusual behaviour, including bipedal walking and gathering and using coconut shells and seashells for shelter.
A female Calliope Hummingbird (Stellula calliope), the smallest bird found in Canada and the United States, feeding insects to chicks. Found mostly in western North America (although vagrants have been found in New York and Connecticut), it is migratory and winters in southwestern Mexico.
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...)
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 Osprey (Pandion haliaetus) is a medium large raptor which is a specialist fish-eater with a worldwide distribution. It is often known by other colloquial names such as Fish Hawk, Sea Hawk or Fish Eagle.
The Osprey is particularly well adapted to its diet, with reversible outer toes, closable nostrils to keep out water during dives, and backwards facing scales on the talons which act as barbs to help catch fish.
The brown 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 at Bodega Head, California.
After hatching, the pelican chicks are fed on regurgitated predigested 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.
Corals are marine invertebrates that typically live in compact colonies of many identical individual polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in length. Corals are major contributors to the physical structure of the coral reefs such as the Great Barrier Reef, where this photograph was taken. Coral reefs are under threat globally from ocean acidification and climate change.
Generally seen as a pioneering work of zoology, Aristotle frames his text by explaining that he is investigating the what (the existing facts about animals) prior to establishing the why (the causes of these characteristics). The book is thus an attempt to apply philosophy to part of the natural world. Throughout the work, Aristotle seeks to identify differences, both between individuals and between groups. A group is established when it is seen that all members have the same set of distinguishing features; for example, that all birds have feathers, wings, and beaks. This relationship between the birds and their features is recognized as a universal. (Full article...)
...that the Southern Giant Petrel is the leading predator to the Emperor 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 as myotonia congenita, and have thus been dubbed "fainting goats"?
Image 9The 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 11Idealised 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)
Image 12Animals are unique in having the ball of cells of the early embryo (1) develop into a hollow ball or blastula (2). (from Animal)
Image 13Bright coloration of orange elephant ear sponge, Agelas clathrodes signals its bitter taste to predators (from Animal coloration)
Image 27A 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 28The blue whale is the largest animal that has ever lived. (from Animal)
Image 29Squid chromatophores appear as black, brown, reddish and pink areas in this micrograph. (from Animal coloration)
Image 30Non-bilaterians include sponges (centre) and corals (background). (from Animal)
Image 35A 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 44Linnaeus's table of the animal kingdom from the first edition of Systema Naturae (1735) (from Zoology)
Image 45Animal anatomical engraving from Handbuch der Anatomie der Tiere für Künstler. (from Zoology)
Image 46Simplified schematic of an island's fauna – all its animal species, highlighted in boxes (from Fauna)
Image 47The bilaterian gut develops in two ways. In many protostomes, the blastopore develops into the mouth, while in deuterostomes it becomes the anus. (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.