Portal:Animals

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Animal diversity.jpg

Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres (110 ft). They have complex interactions with each other and their environments, forming intricate food webs. The kingdom Animalia includes humans, but in colloquial use the term animal often refers only to non-human animals. The study of non-human animals is known as zoology.

Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan. The Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes, arthropods, and molluscs—and the deuterostomes, containing both the echinoderms as well as the chordates, the latter containing the vertebrates. Life forms interpreted as early animals were present in the Ediacaran biota of the late Precambrian. Many modern animal phyla became clearly established in the fossil record as marine species during the Cambrian explosion, which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified; these may have arisen from a single common ancestor that lived 650 million years ago.

Historically, Aristotle divided animals into those with blood and those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa (now synonymous with Animalia) and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa.

Humans make use of many other animal species for food, including meat, milk, and eggs; for materials, such as leather and wool; as pets; and as working animals for power and transport. Dogs have been used in hunting, while many terrestrial and aquatic animals are hunted for sport. Non-human animals have appeared in art from the earliest times and are featured in mythology and religion.

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Marcus Ward Lyon, Jr, sitting

Marcus Ward Lyon, Jr. (1875–1942) was an American mammalogist, bacteriologist, and pathologist. Born into a military family, he demonstrated an early interest in zoology by collecting local wildlife around his father's army posts. He graduated from Brown University in 1897, and continued his studies at George Washington University while working part-time at the United States National Museum. He received his Ph.D. in 1913. Lyon published many papers on mammalogy, formally describing six species, three genera, and one family. In 1919, he and his wife Martha moved to South Bend, Indiana, to join a newly opened clinic. He began to publish medical studies too, but continued his work in mammalogy, with a particular focus on the local fauna of Indiana. He published more than 160 papers during his career. Lyon acquired the rank of major in the Medical Reserve Corps during World War I, and was appointed president of the American Society of Mammalogists from 1931 to 1932. He was a member of Sigma Xi, the Society of American Bacteriologists, the Indiana Academy of Science, and the Biological Society of Washington. Lyon became a conservationist later in life.

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Lynx kitten
Credit: Bernard Landgraf

A Lynx is any of several medium-sized wild cats. Lynxes have short tails, and usually a tuft of hair on the tip of the ears. They have large paws padded for walking on snow, and long whiskers on the face. The lynx inhabits high altitude forests with dense cover of shrubs, reeds and grass.

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When the fox dies, fowls do not mourn.

—Anonymous

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A colour print of platypuses from 1863
The platypus (Ornithorhynchus anatinus) is a semiaquatic egg-laying mammal endemic to eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth. The animal is the sole living representative of its family (Ornithorhynchidae) and genus (Ornithorhynchus), though a number of related species have been found in the fossil record. The unusual appearance of this egg-laying, duck-billed, beaver-tailed, otter-footed mammal baffled European naturalists when they first encountered it, with some considering it an elaborate hoax. It is one of the few venomous mammals, the male platypus having a spur on the hind foot that delivers a venom capable of causing severe pain to humans. Until the early 20th century, it was hunted for its fur, but it is now protected throughout its range. Although captive breeding programs have had only limited success and the platypus is vulnerable to the effects of pollution, it is not under any immediate threat.

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