Animals first appeared in the fossil record in the late Cryogenian period and diversified in the subsequent Ediacaran period in what is known as the Avalon explosion. Earlier evidence of animals is still controversial; the sponge-like organism Otavia has been dated back to the Tonian period at the start of the Neoproterozoic, but its identity as an animal is heavily contested. Nearly all modern animal phyla first appeared in the fossil record as marine species during the Cambrian explosion, which began around 539 million years ago (Mya), and most classes during the Ordovician radiation 485.4 Mya. Common to all living animals, 6,331 groups of genes have been identified that may have arisen from a single common ancestor that lived about 650 Mya during the Cryogenian period. (Full article...)
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The impala or rooibok (Aepyceros melampus, lit. 'black-footed high-horn' in Ancient Greek) is a medium-sized antelope found in eastern and southern Africa. The onlyextant member of the genusAepyceros, and tribe Aepycerotini, it was first described to Europeans by German zoologist Hinrich Lichtenstein in 1812. Two subspecies are recognised—the grassland-dwelling common impala (sometimes referred to as the Kenyan impala), and the larger and darker black-faced impala, which lives in slightly more arid, scrubland environments. The impala reaches 70–92 cm (28–36 in) at the shoulder and weighs 40–76 kg (88–168 lb). It features a glossy, reddish brown coat. The male's slender, lyre-shaped horns are 45–92 cm (18–36 in) long.
Active mainly during the day, the impala may be gregarious or territorial depending upon the climate and geography. Three distinct social groups can be observed: the territorial males, bachelor herds and female herds. The impala is known for two characteristic leaps that constitute an anti-predator strategy. Browsers as well as grazers, impala feed on monocots, dicots, forbs, fruits and acacia pods (whenever available). An annual, three-week-long rut takes place toward the end of the wet season, typically in May. Rutting males fight over dominance, and the victorious male courts females in oestrus. Gestation lasts six to seven months, following which a single calf is born and immediately concealed in cover. Calves are suckled for four to six months; young males—forced out of the all-female groups—join bachelor herds, while females may stay back. (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 have been described in four genera; (Aethozooides, Aethozoon, Franzenella and Monobryozoon). The latter having a statocyst-like organ with a supposed excretory function. (Full article...)
Aplysina archeri is a species of sponge that has long tube-like structures of cylindrical shape. Many tubes are attached to one particular part of the organism; a single tube can grow up to 5 feet (1.5 m) high and 3 inches (7.6 cm) thick. These sponges mostly live in the Atlantic Ocean. These filter feeders eat food such as plankton or suspended detritus as it passes them.
Cymbiola nobilis is a species of sea snail in the familyVolutidae. Found in the Pacific Ocean, from Taiwan to Singapore, it averages 6 centimetres (2.4 in) in length; females are larger than males. Because the shell is commonly collected, there has been an overharvesting of the snail, and it is now considered vulnerable.
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 caterpillar of Lymantria dispar dispar, also known as the gypsy moth. First described by Carl Linnaeus in 1758, the gypsy moth is found throughout Eurasia, where it is considered a pest. The larvae emerge from egg masses in the spring, and then are dispersed by the wind and begin feeding on leaves. They are initially diurnal, but become nocturnal after their fourth molting.
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.
Bolinus cornutus is a predatory species of sea snail, a marine gastropodmollusk in the familyMuricidae. This species is common along the west coast of Africa, where it prefers moderately shallow waters. The shell of the snail is distinctively large, spiny, and club-shaped, usually pale brown or tan in colour, with an elongated and straight siphonal canal.
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.
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 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.
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 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.
Platyhelminthes (from the Greek πλατύ, platy, meaning "flat" and ἕλμινς (root: ἑλμινθ-), helminth-, meaning "worm") is a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates commonly called flatworms or flat worms. 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...)
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.
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 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.
In some countries, it is a legal, competitive activity in which dogs are tested on their ability to run, overtake and turn a hare, rather than a form of hunting aiming at the capture of game. It has a number of variations in its rules around the world. Coursing can also be a form of hunting or pest control. It is a long-established hunting technique, practiced historically in England, especially with greyhounds or sighthound breeds, or with lurchers which are crossbred sighthounds. The sport grew in popularity in Europe during the 19th century but has since experienced a decline due in part to the introduction of greyhound racing with betting, and laws passed that have banned the practice. (Full article...)
Image 6A clade representation of seven dog breeds in relation to wolves. (from Zoology)
Image 7Non-bilaterians include sponges (centre) and corals (background). (from Animal)
Image 8The 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 13The 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 24Idealised nephrozoan 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 28A 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 42Simplified schematic of an island's fauna – all its animal species, highlighted in boxes (from Fauna)
Image 43Squid chromatophores appear as black, brown, reddish and pink areas in this micrograph. (from Animal coloration)
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 45Butterfly wing at different magnifications reveals microstructured chitin acting as diffraction grating. (from Animal coloration)
Image 46This frog changes its skin colour to control its temperature. (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.
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