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 behaviour is known as ethology.
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Bats are flying mammals of the orderChiroptera (/kaɪˈrɒptərə/). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out digits covered with a thin membrane or patagium. The smallest bat, and arguably the smallest extant mammal, is Kitti's hog-nosed bat, which is 29–34 millimetres (1+1⁄8–1+3⁄8 inches) in length, 150 mm (6 in) across the wings and 2–2.6 g (1⁄16–3⁄32 oz) in mass. The largest bats are the flying foxes, with the giant golden-crowned flying fox (Acerodon jubatus) reaching a weight of 1.6 kg (3+1⁄2 lb) and having a wingspan of 1.7 m (5 ft 7 in).
The second largest order of mammals after rodents, bats comprise about 20% of all classified mammal species worldwide, with over 1,400 species. These were traditionally divided into two suborders: the largely fruit-eating megabats, and the echolocatingmicrobats. But more recent evidence has supported dividing the order into Yinpterochiroptera and Yangochiroptera, with megabats as members of the former along with several species of microbats. Many bats are insectivores, and most of the rest are frugivores (fruit-eaters) or nectarivores (nectar-eaters). A few species feed on animals other than insects; for example, the vampire batsfeed on blood. Most bats are nocturnal, and many roost in caves or other refuges; it is uncertain whether bats have these behaviours to escape predators. Bats are present throughout the world, with the exception of extremely cold regions. They are important in their ecosystems for pollinatingflowers and dispersing seeds; many tropical plants depend entirely on bats for these services. (Full article...)
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.
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 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.
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...)
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 maxima clam (Tridacna maxima) is a species of bivalve found throughout the Indo-Pacific. It is found on the surface of reefs or sand, or partly embedded in coral (as with this specimen), in the oceans surrounding east Africa, India, China, Australia, Southeast Asia and the islands of the Pacific. This clam is much sought after in the aquarium trade, as its often striking coloration—the result of crystalline pigment—mimics that of the true giant clam.
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.
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 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...)
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...)
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.
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.
A cross section of a post-clitellum segment of an annelid (ringed worm); almost all segments of an annelid contain the same set of organs and parts, a pattern called metamerism. Annelids have no lungs, but rather exchange carbon dioxide and oxygen directly through the moist skin when blood reaches the extremely fine capillaries of the body walls; a dry worm cannot breathe and will die of suffocation. The worm's red blood, which does not consist of platelets or red cells but mostly of a liquid containing suspended hemoglobin, makes a circuit up and down the animal in its closed circulatory systems.
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.
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.
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.
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One hundred sixteen species of mammals are known to inhabit, or have recently inhabited, the American state of Florida and its surrounding waters. This includes a few species, such as the black-tailed jackrabbit and red deer, that were introduced after the arrival of Europeans. It also includes the extinct Caribbean monk seal and Florida black wolf. Rodents account for roughly one quarter of all species, followed closely by mammals from the families Cetacea and Carnivora.
The species included in this list are drawn from the work of the American Society of Mammalogists (ASM), which compiled information from five different publications. Information on the international conservation status of species has been drawn from the IUCN Red List. (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?
The following are images from various animal-related articles on Wikipedia.
Image 1The 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 2A 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 22The 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 23Kelp gull chicks peck at red spot on mother's beak to stimulate the regurgitating reflex. (from Zoology)
Image 35Idealised 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 44A 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 45This frog changes its skin colour to control its temperature. (from Animal coloration)
Image 46Bright coloration of orange elephant ear sponge, Agelas clathrodes signals its bitter taste to predators (from Animal coloration)
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.