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 dire wolf (Aenocyon dirus/iːˈnɒsaɪ.ɒnˈdaɪrəs/) is an extinct canine. The dire wolf lived in the Americas (with a possible single record also known from East Asia) during the Late Pleistocene and Early Holocene epochs (125,000–9,500 years ago). The species was named in 1858, four years after the first specimen had been found. Two subspecies are recognized: Aenocyon dirus guildayi and Aenocyon dirus dirus. The largest collection of its fossils has been obtained from the Rancho La Brea Tar Pits in Los Angeles.
Dire wolf remains have been found across a broad range of habitats including the plains, grasslands, and some forested mountain areas of North America, the arid savanna of South America. The sites range in elevation from sea level to 2,255 meters (7,400 ft). Dire wolf fossils have rarely been found north of 42°N latitude; there have been only five unconfirmed reports above this latitude. This range restriction is thought to be due to temperature, prey, or habitat limitations imposed by proximity to the Laurentide and Cordilleran ice sheets that existed at the time. (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.
The rock hyrax (Procavia capensis), also known as the dassie, is one of four living species of the order Hyracoidea, and the only living species in its genus. Like all hyraxes, it is a medium-sized terrestrial mammal between 4 kilograms (9 lb) and 5 kilograms (11 lb) in mass, with short ears and tail. The rock hyrax is found across Africa and the Middle East, at elevations up to 4,200 metres (13,800 ft). It resides in habitats with rock crevices which it uses to escape from predators. Along with the other hyrax species and the manatee, these are the animals most closely related to the elephant.
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.
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 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...)
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...)
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...)
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.
The Atlantic spadefish is a species of marine fish endemic to the shallow waters off the coast of the southeastern United States and in the Caribbean Sea. They are similar in appearance to fresh waterangelfish, but much larger, reaching up to three feet (0.9 m) in length. Due to their reputation as strong fighters, they are popular game fish, especially during the summer months when they are most active.
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.
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.
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.
A lateral (left side) anatomical diagram of an adult-stage nematode hermaphroditeCaenorhabditis elegans (full size) with emphasis on the digestive and reproductive systems. C. elegans is a free-living, transparent nematode (roundworm) which measures about 1 millimetre (0.039 in) in length. The hermaphrodite form, as seen here, is the most common, although a male form is also found. When self-inseminated, the species will lay about 300 eggs, but when the hermaphrodite is inseminated by a male, the number of progeny can exceed 1,000.
The Peacock flounder (Bothus mancus) is a species of lefteye flounder found widely in relatively shallow waters in the Indo-Pacific. This photomontage shows four separate views of the same fish, each several minutes apart, starting from the top left. Over the course of the photos, the fish changes its colors to match its new surroundings, and then finally (bottom right) buries itself in the sand, leaving only the eyes protruding.
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The use of horses in World War I marked a transitional period in the evolution of armed conflict. Cavalry units were initially considered essential offensive elements of a military force, but over the course of the war, the vulnerability of horses to modern machine gun, mortar, and artillery fire reduced their utility on the battlefield. This paralleled the development of tanks, which ultimately replaced cavalry in shock tactics. While the perceived value of the horse in war changed dramatically, horses still played a significant role throughout the war.
All of the major combatants in World War I (1914–1918) began the conflict with cavalry forces. Imperial Germany stopped using them on the Western Front soon after the war began, but continued with limited use on the Eastern Front, well into the war. The Ottoman Empire used cavalry extensively during the war. On the Allied side, the United Kingdom used mounted infantry and cavalry charges throughout the war, but the United States used cavalry only briefly. Although not particularly successful on the Western Front, Allied cavalry had some success in the Middle Eastern theatre due to the open nature of the front, allowing a more traditional war of movement, in addition to the lower concentration of artillery and machine guns. Russia used cavalry forces on the Eastern Front but with limited success. (Full article...)
...that Caecillians, an order of amphibians resembling snakes or worms, possess a pair of tentacles, located between their eyes and nostrils which are probably used for olfaction?
Image 21The black and yellow warning colours of the cinnabar moth caterpillar, Tyria jacobaeae, are avoided by some birds. (from Animal coloration)
Image 22The 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 23This frog changes its skin colour to control its temperature. (from Animal coloration)
Image 26Animals are unique in having the ball of cells of the early embryo (1) develop into a hollow ball or blastula (2). (from Animal)
Image 27Bright coloration of orange elephant ear sponge, Agelas clathrodes signals its bitter taste to predators (from Animal coloration)
Image 28The 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 29Linnaeus's table of the animal kingdom from the first edition of Systema Naturae (1735) (from Zoology)
Image 35A 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 37Idealised 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 38Non-bilaterians include sponges (centre) and corals (background). (from Animal)
Image 39Squid chromatophores appear as black, brown, reddish and pink areas in this micrograph. (from Animal coloration)
Image 41A 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 42Fish and frog melanophores are cells that can change colour by dispersing or aggregating pigment-containing bodies. (from Animal coloration)
Image 43A gun dog retrieving a duck during a hunt (from Animal)
Image 44Simplified schematic of an island's fauna – all its animal species, highlighted in boxes (from Fauna)
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.