Portal:Animals

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Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Animals form a single clade.

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.

Most living animal species belong to the infrakingdom Bilateria, a highly proliferative clade whose members have a bilaterally symmetric body plan. Extant bilaterians include the basal group Xenacoelomorpha, but the vast majority belong to two large superphyla: the protostomes, which include phyla such as arthropods, molluscs, flatworms, annelids and nematodes, etc.; and the deuterostomes, which include the three phyla echinoderms, hemichordates and chordates, the latter with the vertebrates being its most successful subphylum. Precambrian life forms interpreted as early complex animals were already present in the Ediacaran biota of the late Proterozoic, but fossils of primitive sponge and other speculative early animals have been dated to as early as the Tonian period. Nearly all modern animal phyla became clearly established 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. 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 Mya during the Cryogenian period. (Full article...)

Zoology (/zˈɒləi/) is the scientific study of animals. Its studies include the structure, embryology, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. Zoology is one of the primary branches of biology. The term is derived from Ancient Greek ζῷον, zōion ('animal'), and λόγος, logos ('knowledge', 'study'). (Full article...)

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R. s. sondaicus in the London Zoo from March 1874 until January 1885

The Javan rhinoceros (Rhinoceros sondaicus), Javan rhino, Sunda rhinoceros or lesser one-horned rhinoceros is a critically endangered member of the genus Rhinoceros, of the rhinoceros family, Rhinocerotidae, and one of the five remaining extant rhinoceros species across South Asia and Africa. The Javan rhinoceros is one of the smallest rhinoceros species, along with the Sumatran, or "hairy", rhinoceros. They are superficially similar to Indian one-horned rhinos, as they have plate-like, "armored" protective skin folds, but are slightly smaller in size, at just 3.1–3.2 m (10–10 ft) long and 1.4–1.7 m (4.6–5.6 ft) tall, on average. The heaviest specimens weigh around 2,300 kg/2.3 tonnes (2.54 short tons), similar to an African black rhinoceros. However, unlike the long and potentially lethal horns of the black or white rhinoceroses of Africa, the Javan species' single, somewhat blunted horn (only present on males) is usually shorter than 25 cm (9.8 in).

Up until the mid-19th to about the early 20th century, the Javan rhinoceros had ranged beyond the islands of Java and Sumatra and onto the mainland of Southeast Asia and Indochina, northwest into East India, Bhutan, and the south of China. Today, it is the rarest of all rhinoceros, and among the rarest of all living animal species, with only one currently known wild population, and no individuals successfully kept in captivity. It is among the rarest large mammals on the planet Earth, with a population of approximately 74 rhinos within Ujung Kulon National Park, at the far western tip of Java, Indonesia. The Javan rhinoceros population in Vietnam's Cat Tien National Park was declared locally extinct in 2011. (Full article...)

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A stack of elephant tusks burning in Kenya in April 2016

The destruction of ivory is a technique used by governments and conservation groups to deter the poaching of elephants for their tusks and to suppress the illegal ivory trade. , more than 263 tonnes (580,000 lb) of ivory have been destroyed, typically by burning or crushing, in these high-profile events in 21 countries around the world. Kenya held the first event in 1989, as well as the largest event in 2016, when a total of 105 tonnes (231,000 lb) of ivory were incinerated.

The conservationists, governments, and non-governmental organizations that endorse the strategy argue that it fosters public support for the protection of elephants and that it sends a message to poachers their work is futile. Critics contend that the technique may increase poaching by creating a perception of scarcity that increases ivory's value on the black market, and that evidence for the technique's effectiveness is insufficient to justify the opportunity cost for countries struggling with poverty. (Full article...)
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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]

Phylum Example No. of
Species
Land Sea Fresh
water
Free-
living
Parasitic
Annelids 17,000[1] Yes (soil)[3] Yes[3] 1,750[2] Yes 400[4]
Arthropods wasp 1,257,000[1] 1,000,000
(insects)[9]
>40,000
(Malac-
ostraca)[10]
94,000[2] Yes[3] >45,000[b][4]
Bryozoa 6,000[1] Yes[3] 60–80[2] Yes
Chordates green spotted frog facing right 65,000[1]
45,000[11]

23,000[11]

13,000[11]
18,000[2]
9,000[11]
Yes 40
(catfish)[12][4]
Cnidaria Table coral 16,000[1] Yes[3] Yes (few)[3] Yes[3] >1,350
(Myxozoa)[4]
Echinoderms 7,500[1] 7,500[1] Yes[3]
Molluscs snail 85,000[1]
107,000[13]

35,000[13]

60,000[13]
5,000[2]
12,000[13]
Yes[3] >5,600[4]
Nematodes 25,000[1] Yes (soil)[3] 4,000[5] 2,000[2] 11,000[5] 14,000[5]
Platyhelminthes 29,500[1] Yes[14] Yes[3] 1,300[2] Yes[3]

3,000–6,500[15]

>40,000[4]

4,000–25,000[15]

Rotifers 2,000[1] >400[16] 2,000[2] Yes
Sponges 10,800[1] Yes[3] 200-300[2] Yes Yes[17]
Total number of described extant species as of 2013: 1,525,728[1]

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References

  1. ^ 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]
  2. ^ Not including parasitoids.[4]
  1. ^ a b c d e f g h i j k l m n Zhang, Zhi-Qiang (2013-08-30). "Animal biodiversity: An update of classification and diversity in 2013. In: Zhang, Z.-Q. (Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013)". Zootaxa. 3703 (1): 5. doi:10.11646/zootaxa.3703.1.3. Archived from the original on 24 April 2019. Retrieved 2 March 2018.
  2. ^ a b c d e f g h i j Balian, E. V.; Lévêque, C.; Segers, H.; Martens, K. (2008). Freshwater Animal Diversity Assessment. Springer. p. 628. ISBN 978-1-4020-8259-7.
  3. ^ a b c d e f g h i j k l m n Hogenboom, Melissa. "There are only 35 kinds of animal and most are really weird". BBC Earth. Archived from the original on 10 August 2018. Retrieved 2 March 2018.
  4. ^ a b c d e f g h Poulin, Robert (2007). Evolutionary Ecology of Parasites. Princeton University Press. p. 6. ISBN 978-0-691-12085-0.
  5. ^ a b c d Felder, Darryl L.; Camp, David K. (2009). Gulf of Mexico Origin, Waters, and Biota: Biodiversity. Texas A&M University Press. p. 1111. ISBN 978-1-60344-269-5.
  6. ^ "How many species on Earth? About 8.7 million, new estimate says". 24 August 2011. Archived from the original on 1 July 2018. Retrieved 2 March 2018.
  7. ^ Mora, Camilo; Tittensor, Derek P.; Adl, Sina; Simpson, Alastair G.B.; Worm, Boris (2011-08-23). Mace, Georgina M. (ed.). "How Many Species Are There on Earth and in the Ocean?". PLOS Biology. 9 (8): e1001127. doi:10.1371/journal.pbio.1001127. PMC 3160336. PMID 21886479.
  8. ^ Hebert, Paul D.N.; Ratnasingham, Sujeevan; Zakharov, Evgeny V.; Telfer, Angela C.; Levesque-Beaudin, Valerie; Milton, Megan A.; Pedersen, Stephanie; Jannetta, Paul; deWaard, Jeremy R. (1 August 2016). "Counting animal species with DNA barcodes: Canadian insects". Philosophical Transactions of the Royal Society B: Biological Sciences. 371 (1702): 20150333. doi:10.1098/rstb.2015.0333. PMC 4971185. PMID 27481785.
  9. ^ 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. PMID 28938083. S2CID 23755007. Stork notes that 1m insects have been named, making much larger predicted estimates.
  10. ^ Poore, Hugh F. (2002). "Introduction". Crustacea: Malacostraca. Zoological catalogue of Australia. Vol. 19.2A. CSIRO Publishing. pp. 1–7. ISBN 978-0-643-06901-5.
  11. ^ a b c d Reaka-Kudla, Marjorie L.; Wilson, Don E.; Wilson, Edward O. (1996). Biodiversity II: Understanding and Protecting Our Biological Resources. Joseph Henry Press. p. 90. ISBN 978-0-309-52075-1.
  12. ^ Burton, Derek; Burton, Margaret (2017). Essential Fish Biology: Diversity, Structure and Function. Oxford University Press. pp. 281–282. ISBN 978-0-19-878555-2. Trichomycteridae ... includes obligate parasitic fish. Thus 17 genera from 2 subfamilies, Vandelliinae; 4 genera, 9spp. and Stegophilinae; 13 genera, 31 spp. are parasites on gills (Vandelliinae) or skin (stegophilines) of fish.
  13. ^ a b c d Nicol, David (June 1969). "The Number of Living Species of Molluscs". Systematic Zoology. 18 (2): 251–254. doi:10.2307/2412618. JSTOR 2412618.
  14. ^ 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. S2CID 38784755.
  15. ^ a b Pandian, T. J. (2020). Reproduction and Development in Platyhelminthes. CRC Press. pp. 13–14. ISBN 9781000054903.
  16. ^ Fontaneto, Diego. "Marine Rotifers | An Unexplored World of Richness" (PDF). JMBA Global Marine Environment. pp. 4–5. Archived (PDF) from the original on 2 March 2018. Retrieved 2 March 2018.
  17. ^ Morand, Serge; Krasnov, Boris R.; Littlewood, D. Timothy J. (2015). Parasite Diversity and Diversification. Cambridge University Press. p. 44. ISBN 978-1-107-03765-6. Archived from the original on 12 December 2018. Retrieved 2 March 2018.