Animal

 

From Wikipedia, the free encyclopedia

 

 

 

For other uses, see Animal (disambiguation).

"Animalia" redirects here. For other uses, see Animalia (disambiguation).

 

 

Animals
Temporal range: Ediacaran – Recent

 

Scentific classification

Domain:Eukaryota

(Unranked)Opisthokonta

(Unranked)Holozoa

(Unranked)Filozoa

Kingdom:Animalia
Linnaeus, 1758

Phyla

• Subkingdom Parazoa

  • Porifera

  • Placozoa

• Subkingdom Eumetazoa

  • Radiata (unranked)

    • Ctenophora

    • Cnidaria

  • Bilateria (unranked)

    • Orthonectida

    • Rhombozoa

    • Acoelomorpha

    • Chaetognatha

    • SuperphylumDeuterostomia

      • Chordata

      • Hemichordata

      • Echinodermata

      • Xenoturbellida

      • Vetulicolia †

    • Protostomia(unranked)

      • SuperphylumEcdysozoa

        • Kinorhyncha

        • Loricifera

        • Priapulida

        • Nematoda

        • Nematomorpha

        • Onychophora

        • Tardigrada

        • Arthropoda

      • SuperphylumPlatyzoa

        • Platyhelminthes

        • Gastrotricha

        • Rotifera

        • Acanthocephala

        • Gnathostomulida

        • Micrognathozoa

        • Cycliophora

      • SuperphylumLophotrochozoa

        • Sipuncula

        • Hyolitha †

        • Nemertea

        • Phoronida

        • Bryozoa

        • Entoprocta

        • Brachiopoda

        • Mollusca

        • Annelida

Synonyms

• Metazoa Haeckel, 1874

Animals are multicellular, eukaryoticorganisms of the kingdom Animalia(also called Metazoa). Their body planeventually becomes fixed as theydevelop, although some undergo a process of metamorphosis later on in their lives. Most animals are motile, meaning they can move spontaneously and independently. All animals must ingest other organisms or their products for sustenance (see Heterotroph).

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);molluscs (clams, oysters, octopuses,squid, snails); arthropods (millipedes,centipedes, insects, spiders, scorpions,crabs, lobsters, shrimp); annelids(earthworms, leeches); sponges; andjellyfish.

 

 

 

Contents

  [hide] 

• 1 Etymology

• 2 Characteristics

  • 2.1 Structure

  • 2.2 Reproduction and development

  • 2.3 Food and energy sourcing

• 3 Origin and fossil record

• 4 Groups of animals

  • 4.1 Ctenophora, Porifera, Placozoa, Cnidaria and Bilateria

  • 4.2 Deuterostomes

  • 4.3 Ecdysozoa

  • 4.4 Platyzoa

  • 4.5 Lophotrochozoa

• 5 Model organisms

• 6 History of classification

• 7 See also

• 8 References

• 9 Bibliography

• 10 External links

 

Etymology

The word "animal" comes from theLatin word animalis, meaning "havingbreath".[1] In everyday non-scientific usage the word excludes humans – that is, "animal" is often used to refer only to non-human members of the kingdom Animalia. Sometimes, only closer relatives of humans such as mammalsand other vertebrates are meant in non-scientific use.[2] The biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges,jellyfish, insects, and humans.[3]

Characteristics

Animals have several characteristics that set them apart from other living things. Animals are eukaryotic andmulticellular,[4] which separates them from bacteria and most protists. They are heterotrophic,[5] generally digesting food in an internal chamber, which separates them from plants andalgae.[6] They are also distinguished from plants, algae, and fungi by lacking rigid cell walls.[7] All animals aremotile,[8] if only at certain life stages. In most animals, embryos pass through ablastula stage,[9] which is a characteristic exclusive to animals.

Structure

With a few exceptions, most notably the sponges (Phylum Porifera) andPlacozoa, animals have bodies differentiated into separate tissues. These include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals. Typically, there is also an internaldigestive chamber, with one or two openings.[10] Animals with this sort of organization are called metazoans, or eumetazoans when the former is used for animals in general.[11]

All animals have eukaryotic cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins.[12] This may be calcified to form structures like shells, bones, and spicules.[13] During development, it forms a relatively flexible framework[14] upon which cells can move about and be reorganized, making complex structures possible. In contrast, other multicellular organisms, like plants and fungi, have cells held in place by cell walls, and so develop by progressive growth.[10] Also, unique to animal cells are the following intercellular junctions: tight junctions, gap junctions, and desmosomes.[15]

Reproduction and development

See also: Sexual reproduction § Animals and Asexual reproduction § Examples in animals

 

 

 

 

A newt lung cell stainedwith fluorescent dyesundergoing the earlyanaphase stage of mitosis

Nearly all animals undergo some form of sexual reproduction.[16] They have a few specializedreproductive cells, which undergo meiosis to produce smaller, motile spermatozoa or larger, non-motile ova.[17] These fuse to form zygotes, which develop into new individuals.[18]

Many animals are also capable of asexual reproduction.[19] This may take place throughparthenogenesis, where fertile eggs are produced without mating, budding, or fragmentation.[20]

A zygote initially develops into a hollow sphere, called a blastula,[21] which undergoes rearrangement and differentiation. In sponges, blastula larvae swim to a new location and develop into a new sponge.[22] In most other groups, the blastula undergoes more complicated rearrangement.[23] It first invaginates to form a gastrula with a digestive chamber, and two separate germ layers — an external ectoderm and an internal endoderm.[24] In most cases, a mesodermalso develops between them.[25] These germ layers then differentiate to form tissues and organs.[26]

Food and energy sourcing

Main article: Animal nutrition

All animals are heterotrophs, meaning that they feed directly or indirectly on other living things.[27] They are often further subdivided into groups such ascarnivores, herbivores, omnivores, and parasites.[28]

Predation is a biological interaction where a predator (a heterotroph that is hunting) feeds on its prey (the organism that is attacked).[29] Predators may or may not kill their prey prior to feeding on them, but the act of predation almost always results in the death of the prey.[30] The other main category of consumption is detritivory, the consumption of dead organic matter.[31] It can at times be difficult to separate the two feeding behaviours, for example, whereparasitic species prey on a host organism and then lay their eggs on it for their offspring to feed on its decaying corpse. Selective pressures imposed on one another has led to an evolutionary arms race between prey and predator, resulting in various antipredator adaptations.[32]

Most animals indirectly use the energy of sunlight by eating plants or plant-eating animals. Most plants use light to convert inorganic molecules in their environment into carbohydrates, fats, proteins and other biomolecules, characteristically containing reduced carbon in the form of carbon-hydrogen bonds. Starting with carbon dioxide (CO2) and water (H2O), photosynthesis converts the energy of sunlight into chemical energy in the form of simple sugars (e.g., glucose), with the release of molecular oxygen. These sugars are then used as the building blocks for plant growth, including the production of other biomolecules.[10] When an animal eats plants (or eats other animals which have eaten plants), the reduced carbon compounds in the food become a source of energy and building materials for the animal.[33] They are either used directly to help the animal grow, or broken down, releasing stored solar energy, and giving the animal the energy required for motion.[34][35]

Animals living close to hydrothermal vents and cold seeps on the ocean floorare not dependent on the energy of sunlight.[36] Instead chemosyntheticarchaea and bacteria form the base of the food chain.[37]

Origin and fossil record

Further information: Urmetazoan

 

 

 

 

Dunkleosteus was a 10-metre-long (33 ft)prehistoric fish.[38]

Animals are generally considered to have evolvedfrom a flagellated eukaryote.[39] Their closest known living relatives are the choanoflagellates, collared flagellates that have a morphology similar to the choanocytes of certain sponges.[40]Molecular studies place animals in a supergroup called the opisthokonts, which also include the choanoflagellates, fungi and a few small parasiticprotists.[41] The name comes from the posterior location of the flagellum in motile cells, such as most animal spermatozoa, whereas other eukaryotes tend to have anterior flagella.[42]

The first fossils that might represent animals appear in the Trezona Formation at Trezona Bore, West Central Flinders, South Australia.[43] These fossils are interpreted as being early sponges. They were found in 665-million-year-old rock.[43]

The next oldest possible animal fossils are found towards the end of thePrecambrian, around 610 million years ago, and are known as the Ediacaran or Vendian biota.[44] These are difficult to relate to later fossils, however. Some may represent precursors of modern phyla, but they may be separate groups, and it is possible they are not really animals at all.[45]

Aside from them, most known animal phyla make a more or less simultaneous appearance during the Cambrian period, about 542 million years ago.[46] It is still disputed whether this event, called the Cambrian explosion, is due to a rapid divergence between different groups or due to a change in conditions that made fossilization possible.

Some paleontologists suggest that animals appeared much earlier than the Cambrian explosion, possibly as early as 1 billion years ago.[47] Trace fossilssuch as tracks and burrows found in the Tonian era indicate the presence oftriploblastic worms, like metazoans, roughly as large (about 5 mm wide) and complex as earthworms.[48] During the beginning of the Tonian period around 1 billion years ago, there was a decrease in Stromatolite diversity, which may indicate the appearance of grazing animals, since stromatolite diversity increased when grazing animals went extinct at the End Permian and End Ordovician extinction events, and decreased shortly after the grazer populations recovered. However the discovery that tracks very similar to these early trace fossils are produced today by the giant single-celled protist Gromia sphaerica casts doubt on their interpretation as evidence of early animal evolution.[49][50]

Groups of animals

 

 

 

 

The relative number of species contributed to the total by each phylum of animals.

Ctenophora, Porifera, Placozoa, Cnidaria and Bilateria

Phylogenetic analysis suggests that thePorifera and Ctenophora diverged before a clade (ParaHoxozoa) that gave rise to the Bilateria, Cnidaria and Placozoa.[51]Another study based on the presence/absence of introns suggests that Cnidaria, Porifera and Placozoa may be a sister group of Bilateria and Ctenophora.[52] A December, 2013, study,[53] and a June, 2014, study[54] both concluded, using entirely distinct methodologies, that the cladogram of animals is:

  
 

Choanoflagellata

 

 

Animal

Ctenophora

 

  

Porifera

 

 

Placozoa

 

 

Cnidaria

 

 

Bilateria

 

 

 

 

 

 

 

 

 

 

 

Orange elephant ear sponge, Agelas clathrodes, in foreground. Two corals in the background: a sea fan, Iciligorgia schrammi, and a sea rod, Plexaurella nutans.

The sponges (Porifera) were long thought to have diverged from other animals early.[55] They lack the complex organization found in most other phyla.[56]Their cells are differentiated, but in most cases not organized into distinct tissues.[57] Sponges typically feed by drawing in water through pores.[58] Archaeocyatha, which have fused skeletons, may represent sponges or a separate phylum.[59] However, a phylogenomic study in 2008 of 150 genes in 29 animals across 21 phyla revealed that it is the Ctenophora or comb jellies which are the basal lineage of animals, at least among those 21 phyla. The authors speculate that sponges—or at least those lines of sponges they investigated—are not so primitive, but may instead be secondarily simplified.[60]

Among the other phyla, the Ctenophora and theCnidaria, which includes sea anemones, corals, andjellyfish, are radially symmetric and have digestive chambers with a single opening, which serves as both the mouth and the anus.[61] Both have distinct tissues, but they are not organized into organs.[62] There are only two main germ layers, the ectoderm and endoderm, with only scattered cells between them. As such, these animals are sometimes called diploblastic.[63] The tinyplacozoans are similar, but they do not have a permanent digestive chamber.

The remaining animals form a monophyletic group called the Bilateria. For the most part, they are bilaterally symmetric, and often have a specialized head with feeding and sensory organs. The body is triploblastic, i.e. all three germ layers are well-developed, and tissues form distinct organs. The digestive chamber has two openings, a mouth and an anus, and there is also an internal body cavity called a coelom or pseudocoelom. There are exceptions to each of these characteristics, however — for instance adult echinoderms are radially symmetric, and certain parasitic worms have extremely simplified body structures.

Genetic studies have considerably changed our understanding of the relationships within the Bilateria. Most appear to belong to two major lineages: the deuterostomes and the protostomes, the latter of which includes theEcdysozoa, Platyzoa, and Lophotrochozoa. In addition, there are a few small groups of bilaterians with relatively similar structure that appear to have diverged before these major groups. These include the Acoelomorpha,Rhombozoa, and Orthonectida. The Myxozoa, single-celled parasites that were originally considered Protozoa, are now believed to have developed from the Medusozoa as well.

Deuterostomes

 

 

 

 

Superb Fairy-wren,Malurus cyaneus

Deuterostomes differ from the other Bilateria, called protostomes, in several ways. In both cases there is a complete digestive tract. However, in protostomes, the first opening of the gut to appear in embryological development (the archenteron) develops into the mouth, with the anus forming secondarily. In deuterostomes the anus forms first, with the mouth developing secondarily.[64] In most protostomes, cells simply fill in the interior of the gastrula to form the mesoderm, called schizocoelous development, but in deuterostomes, it forms through invagination of the endoderm, called enterocoelic pouching.[65]Deuterostome embryos undergo radial cleavage during cell division, while protostomes undergo spiral cleavage.[66]

All this suggests the deuterostomes and protostomes are separate, monophyletic lineages. The main phyla of deuterostomes are theEchinodermata and Chordata.[67] The former are radially symmetric and exclusively marine, such as starfish, sea urchins, and sea cucumbers.[68] The latter are dominated by the vertebrates, animals with backbones.[69] These include fish, amphibians, reptiles, birds, and mammals.[70]

In addition to these, the deuterostomes also include the Hemichordata, or acorn worms.[71] Although they are not especially prominent today, the important fossil graptolites may belong to this group.[72]

The Chaetognatha or arrow worms may also be deuterostomes, but more recent studies suggest protostome affinities.

Ecdysozoa

 

 

 

 

Yellow-winged darter,Sympetrum flaveolum

The Ecdysozoa are protostomes, named after the common trait of growth by moulting or ecdysis.[73]The largest animal phylum belongs here, theArthropoda, including insects, spiders, crabs, and their kin. All these organisms have a body divided into repeating segments, typically with paired appendages. Two smaller phyla, the Onychophoraand Tardigrada, are close relatives of the arthropods and share these traits.

The ecdysozoans also include the Nematoda or roundworms, perhaps the second largest animal phylum. Roundworms are typically microscopic, and occur in nearly every environment where there is water.[74] A number are important parasites.[75] Smaller phyla related to them are the Nematomorphaor horsehair worms, and the Kinorhyncha, Priapulida, and Loricifera. These groups have a reduced coelom, called a pseudocoelom.

The remaining two groups of protostomes are sometimes grouped together as the Spiralia, since in both embryos develop with spiral cleavage.

Platyzoa

 

 

 

 

Pseudobiceros bedfordi, (Bedford's flatworm)

The Platyzoa include the phylum Platyhelminthes, the flatworms.[76] These were originally considered some of the most primitive Bilateria, but it now appears they developed from more complex ancestors.[77] A number of parasites are included in this group, such as the flukes andtapeworms.[76] Flatworms are acoelomates, lacking a body cavity, as are their closest relatives, the microscopic Gastrotricha.[78]

The other platyzoan phyla are mostly microscopic and pseudocoelomate. The most prominent are the Rotifera or rotifers, which are common in aqueous environments. They also include the Acanthocephala or spiny-headed worms, the Gnathostomulida, Micrognathozoa, and possibly the Cycliophora.[79] These groups share the presence of complex jaws, from which they are called theGnathifera.

Lophotrochozoa

 

 

 

 

Roman snail, Helix pomatia

The Lophotrochozoa, evolved within Protostomia, include two of the most successful animal phyla, the Mollusca and Annelida.[80][81] The former, which is the second-largest animal phylum by number of described species, includes animals such as snails, clams, and squids, and the latter comprises the segmented worms, such asearthworms and leeches. These two groups have long been considered close relatives because of the common presence of trochophore larvae, but the annelids were considered closer to the arthropods because they are both segmented.[82] Now, this is generally considered convergent evolution, owing to many morphological and genetic differences between the two phyla.[83]

The Lophotrochozoa also include the Nemertea or ribbon worms, theSipuncula, and several phyla that have a ring of ciliated tentacles around the mouth, called a lophophore.[84] These were traditionally grouped together as the lophophorates.[85] but it now appears that the lophophorate group may beparaphyletic,[86] with some closer to the nemerteans and some to the molluscs and annelids.[87][88] They include the Brachiopoda or lamp shells, which are prominent in the fossil record, the Entoprocta, the Phoronida, and possibly theBryozoa or moss animals.[89]

Model organisms

Main articles: Model organism and Animal testing

Because of the great diversity found in animals, it is more economical for scientists to study a small number of chosen species so that connections can be drawn from their work and conclusions extrapolated about how animals function in general. Because they are easy to keep and breed, the fruit flyDrosophila melanogaster and the nematode Caenorhabditis elegans have long been the most intensively studied metazoan model organisms, and were among the first life-forms to be genetically sequenced. This was facilitated by the severely reduced state of their genomes, but as many genes, introns, andlinkages lost, these ecdysozoans can teach us little about the origins of animals in general. The extent of this type of evolution within the superphylum will be revealed by the crustacean, annelid, and molluscan genome projectscurrently in progress. Analysis of the starlet sea anemone genome has emphasised the importance of sponges, placozoans, and choanoflagellates, also being sequenced, in explaining the arrival of 1500 ancestral genes unique to the Eumetazoa.[90]

An analysis of the homoscleromorph sponge Oscarella carmela also suggests that the last common ancestor of sponges and the eumetazoan animals was more complex than previously assumed.[91]

Other model organisms belonging to the animal kingdom include the house mouse (Mus musculus) and zebrafish (Danio rerio).

 

 

 

 

Carolus Linnaeus, known as the father of modern taxonomy

History of classification

Aristotle divided the living world between animals and plants, and this was followed by Carolus Linnaeus (Carl von Linné), in the first hierarchical classification.[92]Since then biologists have begun emphasizing evolutionary relationships, and so these groups have been restricted somewhat. For instance, microscopicprotozoa were originally considered animals because they move, but are now treated separately.

In Linnaeus's original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia,Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, the Chordata, whereas the various other forms have been separated out. The above lists represent our current understanding of the group, though there is some variation from source to source.

See also

• Book: Animal

• Animal coloration

• Ethology

• Fauna

• List of animal names

• Lists of animals

• List of animals by number of neurons

• Lists of organisms by population

• Zoology

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• Jump up^ Hamilton, Gina. Kingdoms of Life – Animals (ENHANCED eBook). Lorenz Educational Press. p. 9. ISBN 978-1-4291-1610-7.

• ^ Jump up to:a b Maloof, Adam C.; Rose, Catherine V.; Beach, Robert; Samuels, Bradley M.; Calmet, Claire C.; Erwin, Douglas H.; Poirier, Gerald R.; Yao, Nan; Simons, Frederik J. (17 August 2010). "Possible animal-body fossils in pre-Marinoan limestones from South Australia". Nature Geoscience 3 (9): 653.Bibcode:2010NatGe...3..653M. doi:10.1038/ngeo934.

• Jump up^ Costa, James T.; Darwin, Charles (2009). The annotated Origin: a facsimile of the first edition of On the origin of species. Harvard University Press. p. 308.ISBN 978-0-674-03281-1.

• Jump up^ Schopf, J. William (1999). Evolution!: facts and fallacies. Academic Press. p. 7. ISBN 978-0-12-628860-5.

• Jump up^ Milsom, Clare; Rigby, Sue (2009). Fossils at a Glance. John Wiley and Sons.ISBN 978-1-4051-9336-8.

• Jump up^ Campbell, Neil A.; Reece, Jane B. (2005). Biology (7th ed.). Pearson, Benjamin Cummings. p. 526. ISBN 978-0-8053-7171-0.

• Jump up^ Seilacher, Adolf; Bose, Pradip K.; Pfluger, Friedrich (1998). "Animals More Than 1 Billion Years Ago: Trace Fossil Evidence from India". Science 282(5386): 80–83. Bibcode:1998Sci...282...80S.doi:10.1126/science.282.5386.80. PMID 9756480.

• Jump up^ Matz, Mikhail V.; Frank, Tamara M.; Marshall, N. Justin; Widder, Edith A.; Johnsen, Sönke (2008). "Giant Deep-Sea Protist Produces Bilaterian-like Traces". Current Biology 18 (23): 1–6. doi:10.1016/j.cub.2008.10.028.PMID 19026540. Archived from the original on 16 December 2008. Retrieved 2008-12-05.

• Jump up^ Reilly, Michael (20 November 2008). "Single-celled giant upends early evolution". MSNBC. Retrieved 2008-12-05.

• Jump up^ Ryan, JF; Pang, K; Comparative Sequencing Program, Nisc; Mullikin, James C; Martindale, Mark Q; Baxevanis, Andreas D (2010). "The homeodomain complement of the ctenophore Mnemiopsis leidyi suggests that Ctenophora and Porifera diverged prior to the ParaHoxozoa". Evodevo 1 (1): 9.doi:10.1186/2041-9139-1-9. PMC 2959044. PMID 20920347.

• Jump up^ Lehmann J, Stadler PF, Krauss V (2012) Near intron pairs and the metazoan tree. Mol Phylogenet Evol doi:10.1016/j.ympev.2012.11.012

• Jump up^ "The Genome of the Ctenophore Mnemiopsis leidyi and its Implications for Cell Type Evolution". Science 342 (6164). 13 December 2013.doi:10.1126/science.1242592.

• Jump up^ "The ctenophorre genome and the evolutionary origins of neural systems".Nature 510 (7503). 5 June 2014. doi:10.1038/nature.13400.

• Jump up^ Bhamrah, H. S.; Juneja, Kavita (2003). An Introduction to Porifera. Anmol Publications PVT. LTD. p. 58. ISBN 978-81-261-0675-2.

• Jump up^ Sumich, James L. (2008). Laboratory and Field Investigations in Marine Life. Jones & Bartlett Learning. p. 67. ISBN 978-0-7637-5730-4.

• Jump up^ Jessop, Nancy Meyer (1970). Biosphere; a study of life. Prentice-Hall. p. 428.

• Jump up^ Sharma, N. S. (2005). Continuity And Evolution Of Animals. Mittal Publications. p. 106. ISBN 978-81-8293-018-6.

• Jump up^ McGraw-Hill encyclopedia of science & technology: MET-NIC., Volume 11(8th ed.). McGraw-Hill. 1997. p. 59. ISBN 978-0-07-911504-1. Retrieved 19 March 2011.

• Jump up^ Dunn, Casey W. et al. (April 2008). "Broad phylogenomic sampling improves resolution of the animal tree of life". Nature 452 (7188): 745–9.Bibcode:2008Natur.452..745D. doi:10.1038/nature06614. PMID 18322464.

• Jump up^ Langstroth, Lovell; Langstroth, Libby (2000). Newberry, Todd, ed. A Living Bay: The Underwater World of Monterey Bay. University of California Press. p. 244. ISBN 978-0-520-22149-9.

• Jump up^ Safra, Jacob E. (2003). The New Encyclopædia Britannica, Volume 16. Encyclopædia Britannica. p. 523. ISBN 978-0-85229-961-6.

• Jump up^ Kotpal, R. L. Modern Text Book of Zoology: Invertebrates. Rastogi Publications. p. 184. ISBN 978-81-7133-903-7.

• Jump up^ Peters, Kenneth E.; Walters, Clifford C.; Moldowan, J. Michael (2005). The Biomarker Guide: Biomarkers and isotopes in petroleum systems and Earth history 2. Cambridge University Press. p. 717. ISBN 978-0-521-83762-0.

• Jump up^ Safra, Jacob E. (2003). The New Encyclopædia Britannica, Volume 1; Volume 3. Encyclopædia Britannica. p. 767. ISBN 978-0-85229-961-6.

• Jump up^ Valentine, James W. (July 1997). "Cleavage patterns and the topology of the metazoan tree of life". PNAS (The National Academy of Sciences) 94 (15): 8001–8005. Bibcode:1997PNAS...94.8001V. doi:10.1073/pnas.94.15.8001.PMC 21545. PMID 9223303.

• Jump up^ Hyde, Kenneth (2004). Zoology: An Inside View of Animals. Kendall Hunt. p. 345. ISBN 978-0-7575-0997-1.

• Jump up^ Alcamo, Edward (1998). Biology Coloring Workbook. The Princeton Review. p. 220. ISBN 978-0-679-77884-4.

• Jump up^ Holmes, Thom (2008). The First Vertebrates. Infobase Publishing. p. 64.ISBN 978-0-8160-5958-4.

• Jump up^ Rice, Stanley A. (2007). Encyclopedia of evolution. Infobase Publishing. p. 75.ISBN 978-0-8160-5515-9.

• Jump up^ Tobin, Allan J.; Dusheck, Jennie (2005). Asking about life. Cengage Learning. p. 497. ISBN 978-0-534-40653-0.

• Jump up^ Safra, Jacob E. (2003). The New Encyclopædia Britannica, Volume 19. Encyclopædia Britannica. p. 791. ISBN 978-0-85229-961-6.

• Jump up^ Dawkins, Richard (2005). The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution. Houghton Mifflin Harcourt. p. 381. ISBN 978-0-618-61916-0.

• Jump up^ Prewitt, Nancy L.; Underwood, Larry S.; Surver, William (2003). BioInquiry: making connections in biology. John Wiley. p. 289. ISBN 978-0-471-20228-8.

• Jump up^ Schmid-Hempel, Paul (1998). Parasites in social insects. Princeton University Press. p. 75. ISBN 978-0-691-05924-2.

• ^ Jump up to:a b Gilson, Étienne (2004). El espíritu de la filosofía medieval. Ediciones Rialp. p. 384. ISBN 978-84-321-3492-0.

• Jump up^ Ruiz-Trillo, Iñaki; Riutort, Marta; Littlewood, D. Timothy J.; Herniou, Elisabeth A.; Baguña, Jaume (1999). "Acoel Flatworms: Earliest Extant Bilaterian Metazoans, Not Members of Platyhelminthes". Science 283 (5409): 1919–1923.Bibcode:1999Sci...283.1919R. doi:10.1126/science.283.5409.1919.PMID 10082465.

• Jump up^ Todaro, Antonio. "Gastrotricha: Overview". Gastrotricha: World Portal. University of Modena & Reggio Emilia. Retrieved 2008-01-26.

• Jump up^ Kristensen, Reinhardt Møbjerg (2002). "An Introduction to Loricifera, Cycliophora, and Micrognathozoa". Integrative and Comparative Biology 42 (3): 641–651. doi:10.1093/icb/42.3.641. PMID 21708760.

• Jump up^ "Biodiversity: Mollusca". The Scottish Association for Marine Science. Archived from the original on 8 July 2006. Retrieved 2007-11-19.

• Jump up^ Russell, Bruce J. (Writer), Denning, David (Writer) (2000). Branches on the Tree of Life: Annelids (VHS). BioMEDIA ASSOCIATES.

• Jump up^ Eernisse, Douglas J.; Albert, James S.; Anderson, Frank E. (1 September 1992). "Annelida and Arthropoda are not sister taxa: A phylogenetic analysis of spiralean metazoan morphology". Systematic Biology 41 (3): 305–330.doi:10.2307/2992569. JSTOR 2992569.

• Jump up^ Kim, Chang Bae; Moon, Seung Yeo; Gelder, Stuart R.; Kim, Won (1996). "Phylogenetic Relationships of Annelids, Molluscs, and Arthropods Evidenced from Molecules and Morphology". Journal of Molecular Evolution (New York: Springer) 43 (3): 207–215. doi:10.1007/PL00006079. PMID 8703086.

• Jump up^ Collins, Allen G. (1995). The Lophophore. University of California Museum of Paleontology.

• Jump up^ Adoutte, André; Balavoine, Guillaume; Lartillot, Nicolas; Lespinet, Olivier; Prud'Homme, Benjamin; De Rosa, Renaud (2000). "The new animal phylogeny: Reliability and implications". Proceedings of the National Academy of Sciences of the United States of America 97 (9): 4453–4456.Bibcode:2000PNAS...97.4453A. doi:10.1073/pnas.97.9.4453. PMC 34321.PMID 10781043.

• Jump up^ Passamaneck, Yale J. (2003). "Woods Hole Oceanographic Institution"(PDF). Molecular Phylogenetics of the Metazoan Clade Lophotrochozoa. p. 124.

• Jump up^ Sundberg, Per; Turbeville, J. M.; Lindh, Susanne (2001). "Phylogenetic relationships among higher nemertean (Nemertea) taxa inferred from 18S rDNA sequences". Molecular Phylogenetics and Evolution 20 (3): 327–334.doi:10.1006/mpev.2001.0982. PMID 11527461.

• Jump up^ Boore, Jeffrey L.; Staton, Joseph L. (2002). "The mitochondrial genome of the Sipunculid Phascolopsis gouldii supports its association with Annelida rather than Mollusca" (PDF). Molecular Biology and Evolution 19 (2): 127–137.doi:10.1093/oxfordjournals.molbev.a004065. PMID 11801741. Archivedfrom the original on 28 November 2007. Retrieved 2007-11-19.

• Jump up^ Nielsen, Claus (2001). "Bryozoa (Ectoprocta: 'Moss' Animals)". Encyclopedia of Life Sciences (John Wiley & Sons, Ltd). doi:10.1038/npg.els.0001613.ISBN 0-470-01617-5. Retrieved 2008-01-19.

• Jump up^ Putnam, Nicholas H. et al. (2007). "Sea anemone genome reveals ancestral eumetazoan gene repertoire and genomic organization". Science 317 (5834): 86–94. Bibcode:2007Sci...317...86P. doi:10.1126/science.1139158.PMID 17615350.

• Jump up^ Xiujuan Wang; Lavrov, Dennis V. (27 October 2006). "Mitochondrial Genome of the homoscleromorph Oscarella carmela (Porifera, Demospongiae) Reveals Unexpected Complexity in the Common Ancestor of Sponges and Other Animals". Molecular Biology and Evolution 24 (2): 363–373.doi:10.1093/molbev/msl167. PMID 17090697.

• Jump up^ Linnaeus, Carolus (1758). Systema naturae per regna tria naturae :secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. (in Latin) (10th ed.). Holmiae (Laurentii Salvii). Archived from the original on 10 October 2008. Retrieved 22 September 2008.

Bibliography

• Claus Nielsen Animal Evolution: Interrelationships of the Living Phyla. — 3rd ed. — New York: Oxford University Press, 2012. — 402 p. — ISBN 978-0-19960602-3

• Knut Schmidt-Nielsen. Animal Physiology: Adaptation and Environment. (5th edition). Cambridge University Press, 1997.

External links

Find more aboutAnimalia at Wikipedia'ssister projects

Definitions and translations from Wiktionary

Media from Commons

Quotations from Wikiquote

Source texts from Wikisource

Textbooks from Wikibooks

Learning resourcesfrom Wikiversity

•  Data related to Animalia at Wikispecies

• Animal at the Encyclopedia of Life

• Tree of Life Project

• Animal Diversity Web – University of Michigan's database of animals, showingtaxonomic classification, images, and other information.

• ARKive – multimedia database of worldwide endangered/protected species and common species of UK.

• The Animal Kingdom

• Scientific American Magazine (December 2005 Issue) – Getting a Leg Up on Land About the evolution of four-limbed animals from fish.