Portal:Animals

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Animal diversity October 2007 for thumbnail.jpg

Animals are multicellular, eukaryotic organisms of the kingdom Animalia (also called Metazoa). Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their lives. Most animals are motile, meaning they can move spontaneously and independently. Most all animals must ingest other organisms or their products for sustenance, with the exception of those that form symbiotic relationships with photosynthetic organisms.

Most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals are divided into various sub-groups, some of which are: vertebrates (birds, mammals, amphibians, reptiles, fish); mollusks (clams, oysters, octopuses, squid, snails); arthropods (millipedes, centipedes, insects, spiders, scorpions, crabs, lobsters, shrimp); annelids (earthworms, leeches); sponges; and jellyfish.

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Barentsia discreta

Entoprocta is a phylum of mostly sessile aquatic animals, ranging from 0.1 to 7 millimetres (0.0039 to 0.28 in) long. Mature individuals are goblet-shaped, on relatively long stalks. They have a "crown" of solid tentacles whose cilia generate water currents that draw food particles towards the mouth, and both the mouth and anus lie inside the "crown". The superficially similar Bryozoa (Ectoprocta) have the anus outside a "crown" of hollow tentacles. Most families of entoprocts are colonial, and all but 2 of the 150 species are marine. A few solitary species can move slowly. Some species eject unfertilized ova into the water while others keep their ova in brood chambers until they hatch, and some of these species use placenta-like organs to nourish the developing eggs. After hatching, the larvae swim for a short time and then settle on a surface. There they metamorphose, and the larval gut generally rotates by up to 180°, so that the mouth and anus face upwards. Both colonial and solitary species also reproduce by cloning – solitary species grow clones in the space between the tentacles and then release them when developed, while colonial ones produce new members from the stalks or from corridor-like stolons. Some species of nudibranchs ("sea slugs") and turbellarian flatworms prey on entoprocts. A few entoproct species have been found living in close association with other animals. It is uncertain whether any are invasive species.

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Golden toad
Credit: Charles H. Smith, USFWS

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.

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A male Tasmanian devil in an aggressive posture
The Tasmanian Devil is a carnivorous marsupial found exclusively on the Australian island of Tasmania. At the size of a small dog, but stocky and muscular, the Tasmanian Devil is the largest carnivorous marsupial in the world. The devil is characterised by its black fur, offensive odour when stressed, extremely loud and disturbing screech, and vicious temperament when feeding. Known to hunt, as well as to scavenge carrion, communal eating is one of the few social activities in which the usually solitary devil participates. The Tasmanian Devil became extinct on the Australian mainland about 400 years prior to European settlement in 1788. The people of Tasmania saw devils as a threat to livestock and hunted them until 1941, when the animals were officially protected. Since the late 1990s devil facial tumour disease has reduced the devil population significantly and threatens the survival of the species. The impact of the disease on devil population may lead to listing of the devil as an endangered species.

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