text:
Darwin's finches
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Darwin's finches
Large ground finch, Medium ground finch
Small tree finch, Green warbler-finch
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Thraupidae
Genera
Geospiza
Camarhynchus/Platyspiza
Certhidea
Pinaroloxias
Darwin's finches (also known as the Galápagos finches) are a group of about fifteen[1][2][3] species of passerine birds.[4] They are well known for their remarkable diversity in beak form and function.[5] They are often classified as the subfamily Geospizinae or tribe Geospizini. They belong to the tanager family and are not closely related to the true finches. The closest known relative of the Galápagos finches is Tiaris obscurus.[6] They were first collected by Charles Darwin on the Galápagos Islands during the second voyage of the Beagle. Apart from the Cocos finch, which is from Cocos Island, the others are found only on the Galápagos Islands.
The term "Darwin's finches" was first applied by Percy Lowe in 1936, and popularised in 1947 by David Lack in his book Darwin's Finches.[7][8] David Lack based his analysis on the large collection of museum specimens collected by the 1905–06 Galápagos expedition of the California Academy of Sciences, to whom Lack dedicated his 1947 book. The birds vary in size from 10 to 20 cm and weigh between 8 and 38 grams. The smallest are the warbler-finches and the largest is the vegetarian finch. The most important differences between species are in the size and shape of their beaks, which are highly adapted to different food sources. The birds are all dull-coloured.
A long-term study carried out for more than 40 years by the Princeton University researchers Peter and Rosemary Grant has documented micro-evolutionary changes in beak size affected by El Nino/La Nina cycles in the Pacific.[9]
Contents
[hide]
1 Darwin's theory
1.1 Text from The Voyage of the Beagle
1.2 Text from On the Origin of Species
2 Polymorphism in Darwin's finches
3 Taxonomy
3.1 Family
3.2 Species
4 Molecular basis of beak evolution
5 See also
6 Notes
7 References
8 External links
Darwin's theory[edit]
During the survey voyage of HMS Beagle, Darwin was unaware of the significance of the birds of the Galápagos. He had learned how to preserve bird specimens while at the University of Edinburgh and had been keen on shooting, but he had no expertise in ornithology and by this stage of the voyage concentrated mainly on geology.[10] In Galápagos he mostly left bird shooting to his servant Syms Covington.[11] Nonetheless, these birds were to play an important part in the inception of Darwin's theory of evolution by natural selection.
On the Galápagos Islands and afterward, Darwin thought in terms of "centres of creation" and rejected ideas concerning the transmutation of species.[12] From Henslow's teaching, he was interested in the geographical distribution of species, particularly links between species on oceanic islands and on nearby continents. On Chatham Island, he recorded that a mockingbird was similar to those he had seen in Chile, and after finding a different one on Charles Island he carefully noted where mockingbirds had been caught.[10] In contrast, he paid little attention to the finches. When examining his specimens on the way to Tahiti, Darwin noted that all of the mockingbirds on Charles Island were of one species, those from Albemarle of another, and those from James and Chatham Islands of a third. As they sailed home about nine months later, this, together with other facts, including what he had heard about Galápagos tortoises, made him wonder about the stability of species.[13][14]
Following his return from the voyage, Darwin presented the finches to the Zoological Society of London on 4 January 1837, along with other mammal and bird specimens that he had collected. The bird specimens, including the finches, were given to John Gould, the famous English ornithologist, for identification. Gould set aside his paying work and at the next meeting, on 10 January, reported that the birds from the Galápagos Islands that Darwin had thought were blackbirds, "gross-beaks" and finches were actually "a series of ground Finches which are so peculiar [as to form] an entirely new group, containing 12 species". This story made the newspapers.[15][16]
Darwin had been in Cambridge at that time. In early March, he met Gould again and for the first time got a full report on the findings, including the point that his Galápagos "wren" was another closely allied species of finch. The mockingbirds that Darwin had labelled by island were separate species rather than just varieties. Gould found more species than Darwin had expected,[17] and concluded that 25 of the 26 land birds were new and distinct forms, found nowhere else in the world but closely allied to those found on the South American continent.[16] Darwin now saw that, if the finch species were confined to individual islands, like the mockingbirds, this would help to account for the number of species on the islands, and he sought information from others on the expedition. Specimens had also been collected by Captain Robert FitzRoy, FitzRoy’s steward Harry Fuller and Darwin's servant Covington, who had labelled them by island.[18] From these, Darwin tried to reconstruct the locations from where he had collected his own specimens. The conclusions supported his idea of the transmutation of species.[16]
Seen here is adapted radiation of finch A. (Geospiza magnirostris) into three other species of finches found on the Galapagos Islands. Due to the absence of other species of birds, the finches adapted to new niches. The finches beaks and bodies changed allowing them to eat certain types of foods such as nuts, fruits, and insects.
Geospiza magnirostris
Geospiza parvula
Certhidea olivacea
Geospiza fortis
Text from The Voyage of the Beagle[edit]
At the time that he rewrote his diary for publication as Journal and Remarks (later The Voyage of the Beagle), he described Gould's findings on the number of birds, noting that "Although the species are thus peculiar to the archipelago, yet nearly all in their general structure, habits, colour of feathers, and even tone of voice, are strictly American".[19] In the first edition of The Voyage of the Beagle, Darwin said that "It is very remarkable that a nearly perfect gradation of structure in this one group can be traced in the form of the beak, from one exceeding in dimensions that of the largest gros-beak, to another differing but little from that of a warbler".[20]
By the time the first edition was published, the development of Darwin's theory of natural selection was in progress. For the 1845 second edition of The Voyage (now titled Journal of Researches), Darwin added more detail about the beaks of the birds, and two closing sentences which reflected his changed ideas: "Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends."[21][22]
The remaining land-birds form a most singular group of finches, related to each other in the structure of their beaks, short tails, form of body and plumage: there are thirteen species, which Mr. Gould has divided into four subgroups. All these species are peculiar to this archipelago; and so is the whole group, with the exception of one species of the sub-group Cactornis, lately brought from Bow Island, in the Low Archipelago. Of Cactornis, the two species may be often seen climbing about the flowers of the great cactus-trees; but all the other species of this group of finches, mingled together in flocks, feed on the dry and sterile ground of the lower districts. The males of all, or certainly of the greater number, are jet black; and the females (with perhaps one or two exceptions) are brown. The most curious fact is the perfect gradation in the size of the beaks in the different species of Geospiza, from one as large as that of a hawfinch to that of a chaffinch, and (if Mr. Gould is right in including his sub-group, Certhidea, in the main group) even to that of a warbler. The largest beak in the genus Geospiza is shown in Fig. 1, and the smallest in Fig. 3; but instead of there being only one intermediate species, with a beak of the size shown in Fig. 2, there are no less than six species with insensibly graduated beaks. The beak of the sub-group Certhidea, is shown in Fig. 4. The beak of Cactornis is somewhat like that of a starling, and that of the fourth subgroup, Camarhynchus, is slightly parrot-shaped. Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends. In a like manner it might be fancied that a bird originally a buzzard, had been induced here to undertake the office of the carrion-feeding Polybori of the American continent.[23]
Text from On the Origin of Species[edit]
Darwin discussed the divergence of species of birds in the Galápagos more explicitly in his chapter on geographical distribution in On the Origin of Species:
The most striking and important fact for us in regard to the inhabitants of islands, is their affinity to those of the nearest mainland, without being actually the same species. [In] the Galapagos Archipelago... almost every product of the land and water bears the unmistakable stamp of the American continent. There are twenty-six land birds, and twenty-five of these are ranked by Mr. Gould as distinct species, supposed to have been created here; yet the close affinity of most of these birds to American species in every character, in their habits, gestures, and tones of voice, was manifest.... The naturalist, looking at the inhabitants of these volcanic islands in the Pacific, distant several hundred miles from the continent, yet feels that he is standing on American land. Why should this be so? why should the species which are supposed to have been created in the Galapagos Archipelago, and nowhere else, bear so plain a stamp of affinity to those created in America? There is nothing in the conditions of life, in the geological nature of the islands, in their height or climate, or in the proportions in which the several classes are associated together, which resembles closely the conditions of the South American coast: in fact there is a considerable dissimilarity in all these respects. On the other hand, there is a considerable degree of resemblance in the volcanic nature of the soil, in climate, height, and size of the islands, between the Galapagos and Cape de Verde Archipelagos: but what an entire and absolute difference in their inhabitants! The inhabitants of the Cape de Verde Islands are related to those of Africa, like those of the Galapagos to America. I believe this grand fact can receive no sort of explanation on the ordinary view of independent creation; whereas on the view here maintained, it is obvious that the Galapagos Islands would be likely to receive colonists, whether by occasional means of transport or by formerly continuous land, from America; and the Cape de Verde Islands from Africa; and that such colonists would be liable to modification;—the principle of inheritance still betraying their original birthplace.[24]
Polymorphism in Darwin's finches[edit]
Whereas Darwin spent just five weeks in the Galápagos, and David Lack spent three months, Peter and Rosemary Grant and their colleagues have made research trips to the Galápagos for about thirty years, particularly studying Darwin's finches. Here, we look briefly at the case of the large cactus finch Geospiza conirostris on Isla Genovesa (formerly Tower Island), which is formed from a shield volcano, and is home to a variety of birds. These birds, like all well-studied groups,[25] show various kinds of morphism.
Males are dimorphic in song type: songs A and B are quite distinct. Also, males with song A have shorter bills than B males. This is also a clear difference. With these beaks, males are able to feed differently on their favourite cactus, the prickly pear Opuntia. Those with long beaks are able to punch holes in the cactus fruit and eat the fleshy aril pulp, which surrounds the seeds, whereas those with shorter beaks tear apart the cactus base and eat the pulp and any insect larvae and pupae (both groups eat flowers and buds). This dimorphism clearly maximises their feeding opportunities during the non-breeding season when food is scarce.
If the population is panmixic,[26][27] then Geospiza conirostris exhibits a balanced genetic polymorphism and not, as originally supposed, a case of nascent sympatric speciation. The selection maintaining the polymorphism maximises the species' niche by expanding its feeding opportunity. The genetics of this situation cannot be clarified in the absence of a detailed breeding program, but two loci with linkage disequilibrium[28] is a possibility.
Another interesting dimorphism is for the bills of young finches, which are either 'pink' or 'yellow'. All species of Darwin's finches exhibit this morphism, which lasts for two months. No interpretation of this phenomenon is known.[29]
Taxonomy[edit]
Family[edit]
For some decades, taxonomists have placed these birds in the family Emberizidae along with the New World sparrows and Old World buntings (Sulloway 1982). However, the Sibley–Ahlquist taxonomy puts Darwin's finches with the tanagers (Monroe and Sibley 1993), and at least one recent work follows that example (Burns and Skutch 2003). The American Ornithologists' Union, in its North American check-list, places the Cocos finch in the Emberizidae but with an asterisk indicating that the placement is probably wrong (AOU 1998–2006); in its tentative South American check-list, the Galápagos species are incertae sedis, of uncertain place (Remsen et al. 2007).
Species[edit]
Genus Geospiza
Large cactus finch (Geospiza conirostris)
Sharp-beaked ground finch (Geospiza difficilis)
Vampire finch (Geospiza difficilis septentrionalis)
Medium ground finch (Geospiza fortis)
Small ground finch (Geospiza fuliginosa)
Large ground finch (Geospiza magnirostris)
Common cactus finch (Geospiza scandens)
Genus Camarhynchus
Large tree finch (Camarhynchus psittacula)
Medium tree finch (Camarhynchus pauper)
Small tree finch (Camarhynchus parvulus)
Woodpecker finch (Camarhynchus pallidus) – sometimes separated in Cactospiza
Mangrove finch (Camarhynchus heliobates)
Genus Certhidea
Green warbler-finch (Certhidea olivacea)
Grey warbler-finch (Certhidea fusca)
Genus Pinaroloxias
Cocos finch (Pinaroloxias inornata)
Genus Platyspiza
Vegetarian finch (Platyspiza crassirostris)
Molecular basis of beak evolution[edit]
Developmental research in 2004 found that bone morphogenetic protein 4 (BMP4), and its differential expression during development, resulted in variation of beak size and shape among finches. BMP4 acts in the developing embryo to lay down skeletal features, including the beak.[30] The same group showed that the development of the different beak shapes in Darwin's finches are also influenced by slightly different timing and spatial expressions of a gene called calmodulin (CaM).[31] Calmodulin acts in a similar way to BMP4, affecting some of the features of beak growth. The authors suggest that changes in the temporal and spatial expression of these two factors are possible developmental controls of beak morphology. In a recent study genome sequencing revealed a 240 kilobase haplotype encompassing the ALX1 gene that encodes a transcription factor affecting craniofacial development is strongly associated with beak shape diversity.[32][33] Moreover, these changes in the beak size have also altered vocalization in Darwin's finches.[5]
See also[edit]
Species flock[34]
Adaptive radiation
Notes[edit]
Jump up ^ http://www.nature.com/news/darwin-s-iconic-finches-join-genome-club-1.16896
Jump up ^ http://www.uu.se/en/media/news/article/?id=4166.
Jump up ^ http://rstb.royalsocietypublishing.org/content/365/1543/1093
Jump up ^ Grant & Grant 2008, p. 3
^ Jump up to: a b PODOS, JEFFREY; NOWICKI, STEPHEN. "Beaks, Adaptation, and Vocal Evolution in Darwin's Finches". BioScience. 54 (6). doi:10.1641/0006-3568(2004)054[0501:baavei]2.0.co;2.
Jump up ^ Sato, Akie (2001). "On the Origin of Darwin’s Finches" (PDF). Oxford.
Jump up ^ Lack, David. 1947. Darwin's Finches. Cambridge University Press (reissued in 1961 by Harper, New York, with a new preface by Lack; reissued in 1983 by Cambridge University Press with an introduction and notes by Laurene M. Ratcliffe and Peter T. Boag). ISBN 0-521-25243-1
Jump up ^ Steinheimer 2004, p. 300
Jump up ^ Lewitt, Dan. "Galapagos Finch Evolution – Dan Lewitt – HHMI (2013)". Retrieved 6 June 2017.
^ Jump up to: a b Grant, K. Thalia and Estes, Gregory B. 2009 "Darwin in Galapagos: Footsteps to a New World" Princeton University Press, Princeton.
Jump up ^ Steinheimer 2004, pp. 301–303
Jump up ^ Keynes 2000, p. xix.
Eldredge 2006
Jump up ^ Chancellor, Gordon; Keynes, Randal (October 2006), Darwin's field notes on the Galapagos: 'A little world within itself', Darwin Online
Jump up ^ Eldredge 2006
Jump up ^ Desmond & Moore 1991, pp. 208–209
^ Jump up to: a b c Sulloway 1982, pp. 57–58
Jump up ^ Desmond & Moore 1991, p. 248
Jump up ^ Sulloway 2006
Jump up ^ Darwin 1839, pp. 461–462
Jump up ^ Darwin 1839, p. 462.
Jump up ^ Darwin 1845, pp. 379–380
Jump up ^ Darwin 1887
Jump up ^ Darwin 1845, p. 380.
Jump up ^ Darwin 1859, pp. 397–398.
Jump up ^ Huxley J. 1955. Morphism in birds. 11th Int Ornith Cong (Basel 1954, p309-328) touches on this theme.
Jump up ^ B. Rosemary Grant and Peter R. Grant 1989. Evolutionary dynamics of a natural population: the large cactus finch of the Galápagos. Chicago, p241 first para.
Jump up ^ Grant, Peter R. 1999. Ecology and evolution of Darwin's finches. Princeton NJ, p428 in Afterword.
Jump up ^ Maynard Smith J. 1998. Evolutionary genetics. 2nd ed, Chapter 5, Oxford.
Jump up ^ Grant, Peter R. 1999. Ecology and evolution of Darwin's finches. Princeton NJ. (see plate 7)
Jump up ^ Abzhanov, Arhat; Protas, Meredith; Grant, B. Rosemary; Grant, Peter R.; Tabin, Clifford J. (September 3, 2004), "Bmp4 and Morphological Variation of Beaks in Darwin's Finches", Science, 305 (5689): 1462–1465, Bibcode:2004Sci...305.1462A, ISSN 0036-8075, OCLC 1644869, PMID 15353802, doi:10.1126/science.1098095
Jump up ^ Abzhanov, Arhat; Kuo, Winston P.; Hartmann, Christine; Grant, B. Rosemary; Grant, Peter R.; Tabin, Clifford J. (August 3, 2006), "The calmodulin pathway and evolution of elongated beak morphology in Darwin's finches", Nature, 442 (7102): 563–567, Bibcode:2006Natur.442..563A, ISSN 0028-0836, OCLC 1586310, PMID 16885984, doi:10.1038/nature04843
Jump up ^ Andersson, Leif; Lamichhaney, Sangeet; Berglund, Jonas; Almén, Markus Sällman; Maqbool, Khurram; Grabherr, Manfred; Martinez-Barrio, Alvaro; Promerová, Marta; Rubin, Carl-Johan; Wang, Chao; Zamani, Neda; Grant, B. Rosemary; Grant, Peter R.; Webster, Matthew T. (February 11, 2015), "Evolution of Darwin’s finches and their beaks revealed by genome sequencing", Nature, 518 (7102): 563–7, Bibcode:2006Natur.442..563A, ISSN 0028-0836, OCLC 1586310, PMID 25686609, doi:10.1038/nature14181
Jump up ^ 200 years after Darwin, this is how the iconic Galapagos finches are still evolving 2016 April 22
Jump up ^ Podos & Nowicki, Jeffrey & Stephen (2004). "Beaks, Adaptation, and Vocal Evolution in Darwin's Finches". Bioscience. 54: 501–510 – via Oxford academy.
References[edit]
Darwin, Charles (1839), Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle between the years 1826 and 1836, describing their examination of the southern shores of South America, and the Beagle's circumnavigation of the globe. Journal and remarks. 1832–1836, III, London: Henry Colburn
Darwin, Charles (1845), Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the Command of Capt. Fitz Roy, R.N (2nd. ed.), London: John Murray
Darwin, Charles (1859), On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (1st ed.), London: John Murray
Darwin, Francis (1887), "Chapter 1, The Foundations of the 'Origin of Species'", in Darwin, Francis, The life and letters of Charles Darwin, including an autobiographical chapter, 2, London: John Murray
Desmond, Adrian; Moore, James (1991), Darwin, London: Michael Joseph, Penguin Group, ISBN 0-7181-3430-3, OCLC 185764721
Eldredge, Niles (2006), "Confessions of a Darwinist", The Virginia Quarterly Review (Spring 2006), pp. 32–53, retrieved 2008-11-04
Grant, Peter R.; Grant, B. Rosemary (2008), How and Why Species Multiply: The Radiation of Darwin's Finches, Princeton University Press, ISBN 978-0-691-13360-7
Lack, David (1940), "Evolution of the Galapagos Finches", Nature (published 7 September 1940), 146 (3697), pp. 324–327, Bibcode:1940Natur.146..324L, doi:10.1038/146324a0, retrieved 2013-12-06
Check-list of North American Birds, American Ornithologists' Union, 1998–2006, archived from the original on April 4, 2007, retrieved 2007-04-09
Burns, Kevin J.; Skutch, Alexander F. (2003), "Tanagers and Tanager-Finches", in Christopher Perrins, ed., The Firefly Encyclopedia of Birds, Firefly Books, pp. 629–631, ISBN 1-55297-777-3, retrieved 2007-04-09 CS1 maint: Extra text: editors list (link) It is not clear whether this placement was made by Burns and Skutch or by Perrins.
Keynes, Richard (2000), Charles Darwin's zoology notes & specimen lists from H.M.S. Beagle, Cambridge University Press, retrieved 2008-12-08
Sibley, Charles G. (1993), A World Checklist of Birds, New Haven, Conn.: Yale University Press, ISBN 0-300-07083-7, retrieved 2013-12-06 Monroe and Sibley consider the tanagers to be a tribe (Thraupini) of a big family Fringillidae rather than a family of their own (Thraupidae).
Zimmer, J. (2007-04-05), A classification of the bird species of South America, American Ornithologists' Union, archived from the original on 2009-03-02, retrieved 2007-04-09
Steinheimer, F. D. (2004), "Charles Darwin's bird collection and ornithological knowledge during the voyage of H.M.S. Beagle, 1831–1836", Journal of Ornithology, 145 (4), pp. 300–320, doi:10.1007/s10336-004-0043-8, retrieved 2008-12-08
Sulloway, Frank J. (1982), "The Beagle collections of Darwin's finches (Geospizinae)", Bulletin of the British Museum (Natural History), Historical Series, 43 (2), pp. 49–94, retrieved 2008-12-08
Sulloway, Frank J. (Spring 1982), "Darwin and His Finches: The Evolution of a Legend" (PDF), Journal of the History of Biology, 15 (1), pp. 1–53, doi:10.1007/BF00132004, retrieved 2008-12-09
Sulloway, Frank J. (2006), "Why Darwin Rejected Intelligent Design" (PDF), in Brockman, John, Intelligent Thought: Science versus the Intelligent Design Movement, New York: Vintage, pp. 107–126
External links[edit]
Wikimedia Commons has media related to Darwin's finches.
Grant, K.T. and Estes, G. B. 2009. "Darwin in Galapagos: Footsteps to a New World" Princeton University Press, Princeton. [1]
Sulloway, F.J. (1982): "Darwin and his finches: the evolution of a legend". J. Hist. Biol. 15: p. 1–53
Different bills and song melodies
Genetics and the Origin of Birds Species, Grant and Grant in PNAS
Sato et al. Phylogeny of Darwin's finches as revealed by mtDNA sequences in PNAS
Sato A, Tichy H, O'hUigin C, Grant PR, Grant BR, Klein J (March 2001), "On the origin of Darwin's finches", Mol. Biol. Evol., 18 (3): 299–311, PMID 11230531
Galápagos Online. Darwin's Finches.
Galapagos Online. List of birds of the Galapagos Islands.
Darwin's Finches Evolve Before Scientists' Eyes: new developments reported 13 July 2006
Fink F.A.Q. Darwin's finches inspired the naming of the Fink project, a collaborative initiative for porting open source software to the Darwin platform to enable its use and evolution in the Apple Mac OS X environment. "Fink" is the German name for "finch."
Aug 2006 Nature Article that shows how modulation of a certain gene during development can account for the differences seen in beak shape.
Speciation Kimball's Biology Pages
[hide]
v
t
e
Birds (class: Aves)
Anatomy
Bird anatomy
Flight
Eggs
Feathers
Plumage
Beak
Vision
Dactyly
Preen gland
Behaviour
Singing
Intelligence
Migration
Sexual selection
Lek mating
Seabird breeding
Incubation
Brood parasites
Nesting
Hybrids
Evolution
Origin of birds
Origin of flight
Evolution of birds
Darwin's finches
Seabirds
Fossil birds
Archaeopteryx
Omnivoropterygiformes
Confuciusornithiformes
Enantiornithes
Chaoyangiiformes
Patagopterygiformes
Ambiortiformes
Songlingornithiformes
Apsaraviformes
Gansuiformes
Ichthyornithiformes
Hesperornithes
Lithornithiformes
Dinornithiformes
Aepyornithiformes
Gastornithiformes
Human interaction
Ringing
Ornithology
Bird collections
Birdwatching
Bird feeding
Conservation
Aviculture
Waterfowl hunting
Cockfighting
Pigeon racing
Falconry
Pheasantry
Egg collecting
Ornithomancy
Lists
Families and orders
Genera
Glossary of bird terms
List by population
Lists by region
Recently extinct birds
Late Quaternary prehistoric birds
Sibley–Ahlquist taxonomy
Historical & Fictional
Neornithes
Palaeognathae
Struthioniformes (ostriches)
Rheiformes (rheas)
Tinamiformes (tinamous)
Apterygiformes (kiwis)
Casuariiformes (emus and cassowaries)
Neognathae
Galloanserae
(fowls)
Anseriformes
(waterfowls)
Anatidae
Anatinae
Anserinae
swans
true geese
Aythyinae
Dendrocygninae
Merginae
Oxyurinae
Plectropterinae
Stictonettinae
Tadorninae
Thalassorninae
Anhimidae
Anhima
Chauna
Anseranatidae
Anatalavis
Anseranas
Galliformes
(landfowls-
gamebirds)
Cracidae
Cracinae
Oreophasinae
Penelopinae
Megapodidae
Aepypodius
Alectura
Eulipoa
Leipoa
Macrocephalon
Megapodius
Talegalla
Numididae
Acryllium
Agelastes
Guttera
Numida
Odontophoridae
Callipepla
Colinus
Cyrtonyx
Dactylortyx
Dendrortyx
Odontophorus
Oreortyx
Philortyx
Rhynchortyx
Phasianidae
Meleagridinae
Perdicinae
Phasianinae (pheasants and relatives)
Tetraoninae
Neoaves
Columbea
Columbimorphae
Columbiformes (doves and pigeons)
Mesitornithiformes (mesites)
Pteroclidiformes (sandgrouses)
Mirandornithes
Phoenicopteriformes (flamingos)
Podicipediformes (grebes)
Passerea
Otidimorphae
Cuculiformes (cuckoos)
Musophagiformes (turacos)
Otidiformes (bustards)
Strisores
Caprimulgiformes (nightjars and relatives)
Steatornithiformes
Podargiformes
Apodiformes (swifts and hummingbirds)
Opisthocomiformes
Opisthocomiformes (hoatzin)
Cursorimorphae
Charadriiformes (gulls and relatives)
Gruiformes (cranes and relatives)
Phaethontimorphae
Phaethontiformes (tropicbirds)
Eurypygiformes (kagu and sunbittern)
Aequornithes
Gaviiformes (loons or divers)
Sphenisciformes (penguins)
Procellariiformes (albatrosses and petrels)
Ciconiiformes (storks)
Suliformes (cormorants and relatives)
Pelecaniformes (pelicans and relatives)
Australaves
Cariamiformes (seriemas and relatives)
Falconiformes (falcons and relatives)
Psittaciformes (parrots)
Passeriformes (perching birds)
Afroaves
Cathartiformes (New World vultures and condors)
Accipitriformes (eagles and hawks)
Strigiformes (owls)
Coliiformes (mousebirds)
Trogoniformes (trogons and quetzals)
Leptosomatiformes (cuckoo roller)
Bucerotiformes (hornbills and hoopoes)
Coraciiformes (kingfishers and rollers)
Piciformes (woodpeckers and relatives)
Category
Portal
Outline
Retrieved from "https://en.wikipedia.org/w/index.php?title=Darwin%27s_finches&oldid=807869375"
Categories:
Charles Darwin
Endemic birds of the Galápagos Islands
Evolution of birds
Finches
Geospizini
History of evolutionary biology
Polymorphism (biology)
Hidden categories:
Articles with 'species' microformats
CS1 maint: Extra text: editors list
Navigation menu
Personal tools
Not logged in
Talk
Contributions
Create account
Log in
Namespaces
Article
Talk
Variants
Views
Read
Edit
View history
More
Search
Navigation
Main page
Contents
Featured content
Current events
Random article
Donate to Wikipedia
Wikipedia store
Interaction
Help
About Wikipedia
Community portal
Recent changes
Contact page
Tools
What links here
Related changes
Upload file
Special pages
Permanent link
Page information
Wikidata item
Cite this page
Print/export
Create a book
Download as PDF
Printable version
In other projects
Wikimedia Commons
Languages
العربية
Български
Català
Čeština
Deutsch
Español
فارسی
Français
Gaeilge
Galego
한국어
Italiano
עברית
Magyar
Nederlands
日本語
Norsk
Norsk nynorsk
Polski
Português
Русский
Simple English
Suomi
Svenska
Türkçe
Українська
Tiếng Việt
中文
Edit links
This page was last edited on 30 October 2017, at 15:34.
Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.
Privacy policy
About Wikipedia
Disclaimers
Contact Wikipedia
Developers
Cookie statement
Mobile view
Enable previews

values: mw-page-base noprint

values: mw-head-base noprint

values: firstHeading firstHeading en

values: siteSub noprint

values: jump-to-nav mw-jump

value: th

attrs: colspan style

values: text-align: center; background-color: rgb(235,235,210)

value: tr

value: img

attrs: href class

value: td

values: text-align: left; width: 200px; font-size: 100%

values:
/wiki/Isabela_Island_(Ecuador)
mw-redirect
Isabela Island (Ecuador)

attrs: alt src width height class srcset data-file-width data-file-height

values: Edit section: Text from The Voyage of the Beagle

values: Edit section: Text from On the Origin of Species

values: Edit section: Polymorphism in Darwin's finches

values:
/wiki/Geospiza_conirostris
mw-redirect
Geospiza conirostris

values:
/wiki/American_Ornithologists%27_Union
mw-redirect
American Ornithologists' Union

values:
/wiki/Vampire_finch
mw-redirect
Vampire finch

values: Edit section: Molecular basis of beak evolution

values:
/wiki/Species_flock
mw-redirect
Species flock

values:
/wiki/Darwin_Online
mw-redirect
Darwin Online

values:
nofollow
external text
//www.worldcat.org/issn/0036-8075

values:
nofollow
external text
//www.worldcat.org/oclc/1644869

values:
/wiki/PubMed_Identifier
mw-redirect
PubMed Identifier

values:
nofollow
external text
//www.ncbi.nlm.nih.gov/pubmed/15353802

values:
nofollow
external text
//doi.org/10.1126%2Fscience.1098095

values:
nofollow
external text
//www.worldcat.org/issn/0028-0836

values:
nofollow
external text
//www.worldcat.org/oclc/1586310

values:
nofollow
external text
//www.ncbi.nlm.nih.gov/pubmed/16885984

values:
nofollow
external text
//doi.org/10.1038%2Fnature04843

values:
nofollow
external text
https://dx.doi.org/10.1038/nature14181

values:
nofollow
external text
//www.ncbi.nlm.nih.gov/pubmed/25686609

values:
nofollow
external text
//doi.org/10.1038%2Fnature14181

values: -moz-column-width: 30em; -webkit-column-width: 30em; column-width: 30em; list-style-type: decimal;

values:
nofollow
external text
//www.worldcat.org/oclc/185764721

values:
nofollow
external text
//doi.org/10.1038%2F146324a0

values:
nofollow
external text
http://www.aou.org/checklist/index.php3

values:
/wiki/Christopher_Perrins
mw-redirect
Christopher Perrins

values: Category:CS1 maint: Extra text: editors list

values:
nofollow
external text
http://www.sulloway.org/Finches.pdf

values:
nofollow
external text
//doi.org/10.1007%2FBF00132004

values:
nofollow
external autonumber
http://www.darwiningalapagos.com

values:
nofollow
external text
//www.ncbi.nlm.nih.gov/pubmed/11230531

values:
/wiki/Avian_incubation
mw-redirect
Avian incubation

values: Songlingornithiformes (page does not exist)

values:
/wiki/List_of_recently_extinct_birds
mw-redirect
List of recently extinct birds

values:
/wiki/Late_Quaternary_prehistoric_birds
mw-redirect
Late Quaternary prehistoric birds

values:
/wiki/Modern_birds
mw-redirect
Modern birds

attrs: alt src title width height srcset data-file-width data-file-height

values: nowraplinks hlist collapsible autocollapse navbox-inner

values: Category:Endemic birds of the Galápagos Islands

values: Category:History of evolutionary biology

values: Category:Articles with 'species' microformats

values: Discussion about edits from this IP address [ctrl-alt-n]

values: A list of edits made from this IP address [ctrl-alt-y]

values: You are encouraged to create an account and log in; however, it is not mandatory

values: You're encouraged to log in; however, it's not mandatory. [ctrl-alt-o]

values:
/wiki/Darwin%27s_finches
View the content page [ctrl-alt-c]
c

values: Discussion about the content page [ctrl-alt-t]

values: p-namespaces navigation vectorTabs p-namespaces-label

values:
p-variants
navigation
vectorMenu emptyPortlet
p-variants-label

values: Past revisions of this page [ctrl-alt-h]

values: p-views navigation vectorTabs p-views-label

values:
p-cactions
navigation
vectorMenu emptyPortlet
p-cactions-label

values:
mw-wiki-logo
/wiki/Main_Page
Visit the main page

values:
/wiki/Main_Page
Visit the main page [ctrl-alt-z]
z

values: Featured content – the best of Wikipedia

values: Find background information on current events

values:
/wiki/Special:Random
Load a random article [ctrl-alt-x]
x

values: portal navigation p-wikibase-otherprojects p-wikibase-otherprojects-label

values:
uls-settings-trigger
Language settings
0
button
true

values: عصافير داروين – Arabic

values: Галапагоски чинки – Bulgarian

values: interlanguage-link interwiki-bg badge-Q17437796 badge-featuredarticle

values: سهره‌های داروین – Persian

values: 다윈의 핀치 – Korean

values: פרושי דרווין – Hebrew

values: ダーウィンフィンチ類 – Japanese

values: Галапагосские вьюрки – Russian

values: Зяблики Дарвіна – Ukrainian

values: /static/images/wikimedia-button-1.5x.png 1.5x, /static/images/wikimedia-button-2x.png 2x

values: /static/images/poweredby_mediawiki_132x47.png 1.5x, /static/images/poweredby_mediawiki_176x62.png 2x

values:
suggestions
display: none; font-size: 13px;

values: mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject page-Darwin_s_finches rootpage-Darwin_s_finches vector-experimental-print-styles vector-nav-directionality skin-vector action-view


text:
Aggregate demand
From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about a concept in macroeconomics. For the microeconomic demand aggregated over consumers, see Demand curve.
In macroeconomics, aggregate demand (AD) or domestic final demand (DFD) is the total demand for final goods and services in an economy at a given time.[1] It specifies the amounts of goods and services that will be purchased at all possible price levels.[2] This is the demand for the gross domestic product of a country. It is often called effective demand, though at other times this term is distinguished.
The aggregate demand curve is plotted with real output on the horizontal axis and the price level on the vertical axis. It is downward sloping as a result of three distinct effects: Pigou's wealth effect, Keynes' interest rate effect and the Mundell–Fleming exchange-rate effect. The Pigou effect states that a higher price level implies lower real wealth and therefore lower consumption spending, giving a lower quantity of goods demanded in the aggregate. The Keynes effect states that a higher price level implies a lower real money supply and therefore higher interest rates resulting from financial market equilibrium, in turn resulting in lower investment spending on new physical capital and hence a lower quantity of goods being demanded in the aggregate.
The Mundell–Fleming exchange-rate effect is an extension of the IS–LM model. Whereas the traditional IS-LM Model deals with a closed economy, Mundell–Fleming describes a small open economy. The Mundell–Fleming model portrays the short-run relationship between an economy's nominal exchange rate, interest rate, and output (in contrast to the closed-economy IS–LM model, which focuses only on the relationship between the interest rate and output)
The aggregate demand curve illustrates the relationship between two factors: the quantity of output that is demanded and the aggregate price level. Aggregate demand is expressed contingent upon a fixed level of the nominal money supply. There are many factors that can shift the AD curve. Rightward shifts result from increases in the money supply, in government expenditure, or in autonomous components of investment or consumption spending, or from decreases in taxes.
According to the aggregate demand-aggregate supply model, when aggregate demand increases, there is movement up along the aggregate supply curve, giving a higher level of prices.[3]
Contents
[hide]
1 History
2 Components
3 Aggregate demand curves
3.1 Keynesian cross
3.2 Aggregate demand-aggregate supply model
4 Debt
5 Criticisms
6 See also
7 References
8 External links
History[edit]
Main article: The General Theory of Employment, Interest and Money
John Maynard Keynes in The General Theory of Employment, Interest and Money argued during the Great Depression that the loss of output by the private sector as a result of a systemic shock (the Wall Street Crash of 1929) ought to be filled by government spending. First, he argued that with a lower ‘effective aggregate demand’, or the total amount of spending in the economy (lowered in the Crash), the private sector could subsist on a permanently reduced level of activity and involuntary unemployment, unless there were active intervention. Business lost access to capital, so it had dismissed workers. This meant workers had less to spend as consumers, consumers bought less from business, which because of additionally reduced demand, had found the need to dismiss workers. The downward spiral could only be halted and rectified by external action. Second, people with higher incomes have a lower marginal propensity to consume their incomes. People with lower incomes are inclined to spend their earnings immediately to buy housing, food, transport and so forth, while people with much higher incomes cannot consume everything. They save instead, which means that the velocity of money, meaning the circulation of income through different hands in the economy, is decreased. This lowered the rate of growth. Spending should therefore target public works programmes on a large enough scale to speed up growth to its previous levels.
Components[edit]
An aggregate demand curve is the sum of individual demand curves for different sectors of the economy. The aggregate demand is usually described as a linear sum of four separable demand sources:[4]
A D = C + I + G + ( X − M ) {\displaystyle AD=C+I+G+(X-M)}
where
C {\displaystyle C} is consumption (may also be known as consumer spending), which is given by a c + b c ( Y − T ) {\displaystyle a_{c}+b_{c}(Y-T)} where Y {\displaystyle Y} is consumers' income and T {\displaystyle T} the taxes paid by consumers,
I {\displaystyle I} is investment,
G {\displaystyle G} is government spending,
N X = X − M {\displaystyle NX=X-M} is net exports, where
X {\displaystyle X} is total exports, and
M {\displaystyle M} total imports, given by a m + b m ( Y − T ) {\displaystyle a_{m}+b_{m}(Y-T)} .
These four major parts, which can be stated in either 'nominal' or 'real' terms, are:
personal consumption expenditures ( C {\displaystyle C} ) or "consumption," demand by households and unattached individuals; its determination is described by the consumption function. A basic conception is that it is the total consumption expenditures of the domestic economy. The consumption function is C = a + M P C × ( Y − T ) {\displaystyle C=a+MPC\times (Y-T)} , where
a {\displaystyle a} is autonomous consumption, M P C {\displaystyle MPC} the marginal propensity to consume, and ( Y − T ) {\displaystyle (Y-T)} the disposable income.
gross private domestic investment ( I {\displaystyle I} ), such as spending by business firms on factory construction. This is conceived as all private sector spending aimed at the production of some future consumable.
In Keynesian economics, not all of gross private domestic investment counts as part of aggregate demand. Much or most of the investment in inventories can be due to a short-fall in demand (unplanned inventory accumulation or "general over-production"). The Keynesian model forecasts a decrease in national output and income when there is unplanned investment. (Inventory accumulation would correspond to an excess supply of products; in the National Income and Product Accounts, it is treated as a purchase by its producer.) Thus, only the planned or intended or desired part of investment ( I p {\displaystyle I_{p}} ) is counted as part of aggregate demand. (So, I {\displaystyle I} does not include the 'investment' in running up or depleting inventory levels.)
Investment is affected by the output and the interest rate ( i {\displaystyle i} ). Consequently, we can write it as, I ( Y , i ) {\displaystyle I(Y,i)} , a function I which takes total income and interest rate as parameters. Investment has positive relationship with the output and negative relationship with the interest rate. Thus, an increase in the interest rate will cause aggregate demand to decline. Interest costs are part of the cost of borrowing and as they rise, both firms and households will cut back on spending. This shifts the aggregate demand curve to the left. This lowers equilibrium GDP below potential GDP.
gross government investment and consumption expenditures ( G {\displaystyle G} ), also determined as G − T {\displaystyle G-T} , the difference of government expenditures and taxes. An increase in government expenditures or decrease in taxes, therefore leads to an increase in GDP as government expenditures are a component of aggregate demand.
net exports ( N X {\displaystyle NX} and sometimes ( X − M {\displaystyle X-M} )), net demand by the rest of the world for the country's output. This contributes to the current account.
In sum, for a single country at a given time, aggregate demand ( D {\displaystyle D} or A D {\displaystyle AD} ) is given by C + I p + G + ( X − M ) {\displaystyle C+I_{p}+G+(X-M)} .
These macroeconomic variables are constructed from varying types of microeconomic variables from the price of each, so these variables are denominated in (real or nominal) currency terms.
Aggregate demand curves[edit]
Understanding of the aggregate demand curve depends on whether it is examined based on changes in demand as income changes, or as price change.
Keynesian cross[edit]
Main article: Keynesian cross
Aggregate demand-aggregate supply model[edit]
Main article: AD–AS model
Sometimes, especially in textbooks, "aggregate demand" refers to an entire demand curve that looks like that in a typical Marshallian supply and demand diagram.
Aggregate supply/demand graph
Thus, we could refer to an "aggregate quantity demanded" ( Y d = C + I p + G + N X {\displaystyle Y^{d}=C+I_{p}+G+NX} in real or inflation-corrected terms) at any given aggregate average price level (such as the GDP deflator), P {\displaystyle P} .
In these diagrams, typically the Y d {\displaystyle Y^{d}} rises as the average price level ( P {\displaystyle P} ) falls, as with the A D {\displaystyle AD} line in the diagram. The main theoretical reason for this is that if the nominal money supply (Ms) is constant, a falling P {\displaystyle P} implies that the real money supply ( M s P {\displaystyle {\frac {M^{s}}{P}}} )rises, encouraging lower interest rates and higher spending. This is often called the "Keynes effect."
Carefully using ideas from the theory of supply and demand, aggregate supply can help determine the extent to which increases in aggregate demand lead to increases in real output or instead to increases in prices (inflation). In the diagram, an increase in any of the components of A D {\displaystyle AD} (at any given P {\displaystyle P} ) shifts the A D {\displaystyle AD} curve to the right. This increases both the level of real production ( Y {\displaystyle Y} ) and the average price level ( P {\displaystyle P} ).
But different levels of economic activity imply different mixtures of output and price increases. As shown, with very low levels of real gross domestic product and thus large amounts of unemployed resources, most economists of the Keynesian school suggest that most of the change would be in the form of output and employment increases. As the economy gets close to potential output ( Y ∗ {\displaystyle Y^{*}} ), we would see more and more price increases rather than output increases as A D {\displaystyle AD} increases.
Beyond Y ∗ {\displaystyle Y^{*}} , this gets more intense, so that price increases dominate. Worse, output levels greater than Y ∗ {\displaystyle Y^{*}} cannot be sustained for long. The A S {\displaystyle AS} is a short-term relationship here. If the economy persists in operating above potential, the A S {\displaystyle AS} curve will shift to the left, making the increases in real output transitory.
At low levels of Y {\displaystyle Y} , the world is more complicated. First, most modern industrial economies experience few if any falls in prices. So the A S {\displaystyle AS} curve is unlikely to shift down or to the right. Second, when they do suffer price cuts (as in Japan), it can lead to disastrous deflation.
Debt[edit]
A post-Keynesian theory of aggregate demand emphasizes the role of debt, which it considers a fundamental component of aggregate demand;[5] the contribution of change in debt to aggregate demand is referred to by some as the credit impulse.[6] Aggregate demand is spending, be it on consumption, investment, or other categories. Spending is related to income via:
Income – Spending = Net Savings
Rearranging this yields:
Spending = Income – Net Savings = Income + Net Increase in Debt
In words: What you spend is what you earn, plus what you borrow. If you spend $110 and earned $100, then you must have net borrowed $10. Conversely if you spend $90 and earn $100, then you have net savings of $10, or have reduced debt by $10, for a net change in debt of –$10.
If debt grows or shrinks slowly as a percentage of GDP, its impact on aggregate demand is small. Conversely, if debt is significant, then changes in the dynamics of debt growth can have significant impact on aggregate demand. Change in debt is tied to the level of debt:[5] if the overall debt level is 10% of GDP and 1% of loans are not repaid, this impacts GDP by 1% of 10% = 0.1% of GDP, which is statistical noise. Conversely, if the debt level is 300% of GDP and 1% of loans are not repaid, this impacts GDP by 1% of 300% = 3% of GDP, which is significant: a change of this magnitude will generally cause a recession.
Similarly, changes in the repayment rate (debtors paying down their debts) impact aggregate demand in proportion to the level of debt. Thus, as the level of debt in an economy grows, the economy becomes more sensitive to debt dynamics, and credit bubbles are of macroeconomic concern. Since write-offs and savings rates both spike in recessions, both of which result in shrinkage of credit, the resulting drop in aggregate demand can worsen and perpetuate the recession in a vicious cycle.
This perspective originates in, and is intimately tied to, the debt-deflation theory of Irving Fisher, and the notion of a credit bubble (credit being the flip side of debt), and has been elaborated in the Post-Keynesian school.[5] If the overall level of debt is rising each year, then aggregate demand exceeds Income by that amount. However, if the level of debt stops rising and instead starts falling (if "the bubble bursts"), then aggregate demand falls short of income, by the amount of net savings (largely in the form of debt repayment or debt writing off, such as in bankruptcy). This causes a sudden and sustained drop in aggregate demand, and this shock is argued to be the proximate cause of a class of economic crises, properly financial crises. Indeed, a fall in the level of debt is not necessary – even a slowing in the rate of debt growth causes a drop in aggregate demand (relative to the higher borrowing year).[7] These crises then end when credit starts growing again, either because most or all debts have been repaid or written off, or for other reasons as below.
From the perspective of debt, the Keynesian prescription of government deficit spending in the face of an economic crisis consists of the government net dis-saving (increasing its debt) to compensate for the shortfall in private debt: it replaces private debt with public debt. Other alternatives include seeking to restart the growth of private debt ("reflate the bubble"), or slow or stop its fall; and debt relief, which by lowering or eliminating debt stops credit from contracting (as it cannot fall below zero) and allows debt to either stabilize or grow – this has the further effect of redistributing wealth from creditors (who write off debts) to debtors (whose debts are relieved).
Criticisms[edit]
Austrian theorist Henry Hazlitt argued that aggregate demand is "a meaningless concept" in economic analysis.[8] Friedrich Hayek, another Austrian, wrote that Keynes' study of the aggregate relations in an economy is "fallacious," arguing that recessions are caused by micro-economic factors.[9]
See also[edit]
Aggregate supply
Aggregation problem
Disequilibrium
Economic surplus
Effective demand
Excess demand
Excess demand function
Excess supply
Induced demand
Reproduction
Scarcity
Supply and demand
Supply shock
References[edit]
Jump up ^ Sexton, Robert; Fortura, Peter (2005). Exploring Economics. ISBN 0-17-641482-7. This is the sum of the demand for all final goods and services in the economy. It can also be seen as the quantity of real GDP demanded at different price levels.
Jump up ^ O'Sullivan, Arthur; Steven M. Sheffrin (2003). Economics: Principles in action. Upper Saddle River, New Jersey 07458: Pearson Prentice Hall. p. 307. ISBN 0-13-063085-3.
Jump up ^ Mankiw, N. Gregory, and William M. Scarth. Macroeconomics. Canadian ed., 4th ed. New York: Worth Publishers, 2011. Print.
Jump up ^ "aggregate demand (AD)". Archived from the original on 9 November 2007. Retrieved 2007-11-04.
^ Jump up to: a b c Debtwatch No 41, December 2009: 4 Years of Calling the GFC, Steve Keen, December 1, 2009
Jump up ^ Credit and Economic Recovery: Demystifying Phoenix Miracles, Michael Biggs, Thomas Mayer, Andreas Pick, March 15, 2010
Jump up ^ "However much you borrow and spend this year, if it is less than last year, it means your spending will go into recession." Dhaval Joshi, RAB Capital, quoted in Noughty boys on trading floor led us into debt-laden fantasy
Jump up ^ Hazlitt, Henry (1959). The Failure of the 'New Economics': An Analysis of the Keynesian Fallacies (PDF). D. Van Nostrand. [page needed]
Jump up ^ Hayek, Friedrich (1989). The Collected Works of F.A. Hayek. University of Chicago Press. p. 202. ISBN 978-0-226-32097-7.
External links[edit]
Elmer G. Wiens: Classical & Keynesian AD-AS Model - An on-line, interactive model of the Canadian Economy.
[show]
v
t
e
Economics
Economic theory
Econometrics
Applied economics
Macroeconomics
Adaptive expectations
Aggregate demand
Balance of payments
Business cycle
Capacity utilization
Capital flight
Central bank
Consumer confidence
Currency
Demand shock
Depression (Great Depression)
DSGE
Economic growth
Economic indicator
Economic rent
Effective demand
General Theory of Keynes
Hyperinflation
Inflation
Interest
Interest rate
Investment
IS–LM model
Microfoundations
Monetary policy
Money
NAIRU
National accounts
PPP
Rate of profit
Rational expectations
Recession
Saving
Shrinkflation
Stagflation
Supply shock
Unemployment
Macroeconomics publications
Microeconomics
Aggregation problem
Budget set
Consumer choice
Convexity
Cost–benefit analysis
Deadweight loss
Distribution
Duopoly
Economic equilibrium
Economic shortage
Economic surplus
Economies of scale
Economies of scope
Elasticity
Expected utility hypothesis
Externality
General equilibrium theory
Indifference curve
Intertemporal choice
Marginal cost
Market failure
Market structure
Monopoly
Monopsony
Non-convexity
Oligopoly
Opportunity cost
Preference
Production set
Profit
Public good
Returns to scale
Risk aversion
Scarcity
Social choice theory
Sunk costs
Supply and demand
Theory of the firm
Trade
Transaction cost
Value
Uncertainty
Utility
Microeconomics publications
Applied fields
Agricultural
Business
Demographic
Development
Economic history
Education
Environmental
Financial
Health
Industrial organization
International
Knowledge
Labour
Law and economics
Monetary
Natural resource
Public
Service
Urban
Welfare
Methodology
Behavioral economics
Computational economics
Econometrics
Economic systems
Experimental economics
Mathematical economics
Methodological publications
Economic thought
Ancient economic thought
Austrian school of economics
Chicago school of economics
Classical economics
Feminist economics
Heterodox economics
Institutional economics
Keynesian economics
Mainstream economics
Marxian economics
Neoclassical economics
Post-Keynesian economics
Schools overview
Notable economists and
thinkers within economics
Kenneth Arrow
Gary Becker
Francis Ysidro Edgeworth
Milton Friedman
Ragnar Frisch
Friedrich Hayek
Harold Hotelling
John Maynard Keynes
Tjalling Koopmans
Paul Krugman
Robert Lucas Jr.
Jacob Marschak
Alfred Marshall
Karl Marx
John von Neumann
Vilfredo Pareto
David Ricardo
Paul Samuelson
Joseph Schumpeter
Amartya Sen
Herbert A. Simon
Adam Smith
Robert Solow
Léon Walras
more
International organizations
Asia-Pacific Economic Cooperation
Economic Cooperation Organization
European Free Trade Association
International Monetary Fund
Organisation for Economic Co-operation and Development
World Bank
World Trade Organization
Category
Index
Lists
Outline
Publications
Business and economics portal
Retrieved from "https://en.wikipedia.org/w/index.php?title=Aggregate_demand&oldid=806039487"
Categories:
Demand
Macroeconomic aggregates
Mathematical and quantitative methods (economics)
Hidden categories:
Wikipedia articles needing page number citations from November 2010
Navigation menu
Personal tools
Not logged in
Talk
Contributions
Create account
Log in
Namespaces
Article
Talk
Variants
Views
Read
Edit
View history
More
Search
Navigation
Main page
Contents
Featured content
Current events
Random article
Donate to Wikipedia
Wikipedia store
Interaction
Help
About Wikipedia
Community portal
Recent changes
Contact page
Tools
What links here
Related changes
Upload file
Special pages
Permanent link
Page information
Wikidata item
Cite this page
Print/export
Create a book
Download as PDF
Printable version
Languages
العربية
Asturianu
Català
Čeština
Deutsch
Español
فارسی
Français
Galego
한국어
Italiano
עברית
Қазақша
ລາວ
Latviešu
Lietuvių
Bahasa Melayu
Nederlands
日本語
Oʻzbekcha/ўзбекча
Polski
Português
Русский
Svenska
ไทย
Türkçe
Українська
Tiếng Việt
中文
Edit links
This page was last edited on 19 October 2017, at 07:59.
Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.
Privacy policy
About Wikipedia
Disclaimers
Contact Wikipedia
Developers
Cookie statement
Mobile view
Enable previews

key: html

type: local

value: div

attrs: id class

values: mw-page-base noprint

values: mw-head-base noprint

value: a

attrs: id class lang

values: firstHeading firstHeading en

values: siteSub noprint

values: jump-to-nav mw-jump

attrs: href title

attrs: role class

values:
note
hatnote navigation-not-searchable

value: b

value: sup

value: p

values:
/wiki/Government_expenditure
mw-redirect
Government expenditure

values: vertical-align: -0.838ex; width:29.27ex; height:2.843ex;

values: vertical-align: -0.338ex; width:1.777ex; height:2.176ex;

values: vertical-align: -0.838ex; width:15.114ex; height:2.843ex;

values: vertical-align: -0.338ex; width:1.784ex; height:2.176ex;

values: vertical-align: -0.338ex; width:1.647ex; height:2.176ex;

values: vertical-align: -0.338ex; width:1.182ex; height:2.176ex;

values: vertical-align: -0.338ex; width:1.837ex; height:2.176ex;

values: vertical-align: -0.338ex; width:14.467ex; height:2.176ex;

values: vertical-align: -0.338ex; width:1.99ex; height:2.176ex;

values: vertical-align: -0.338ex; width:2.453ex; height:2.176ex;

values: vertical-align: -0.838ex; width:16.575ex; height:2.843ex;

values:
/wiki/Real_vs._nominal_in_economics
mw-redirect
Real vs. nominal in economics

values: vertical-align: -0.838ex; width:25.924ex; height:2.843ex;

values: vertical-align: -0.338ex; width:1.24ex; height:1.676ex;

values: vertical-align: -0.338ex; width:5.985ex; height:2.176ex;

values: vertical-align: -0.838ex; width:8.112ex; height:2.843ex;

values: vertical-align: -1.005ex; width:2.1ex; height:2.843ex;

values: vertical-align: -0.338ex; width:0.813ex; height:2.176ex;

values: vertical-align: -0.838ex; width:6.653ex; height:2.843ex;

values: vertical-align: -0.338ex; width:6.335ex; height:2.176ex;

values: vertical-align: -0.338ex; width:4.065ex; height:2.176ex;

values: vertical-align: -0.338ex; width:7.294ex; height:2.176ex;

values: vertical-align: -0.338ex; width:1.935ex; height:2.176ex;

values: vertical-align: -0.338ex; width:3.688ex; height:2.343ex;

values: vertical-align: -1.005ex; width:23.391ex; height:3.009ex;

values: Edit section: Aggregate demand-aggregate supply model

values:
/wiki/Marshallian_demand
mw-redirect
Marshallian demand

values: vertical-align: -1.005ex; width:24.45ex; height:3.343ex;

values: vertical-align: -0.338ex; width:1.756ex; height:2.176ex;

values: vertical-align: -0.338ex; width:3.01ex; height:2.676ex;

values: vertical-align: -2.005ex; width:4.356ex; height:5.509ex;

values: vertical-align: -0.338ex; width:2.972ex; height:2.343ex;

values: vertical-align: -0.338ex; width:3.263ex; height:2.343ex;

values:
/wiki/Deflation_(economics)
mw-redirect
Deflation (economics)

values:
/wiki/Vicious_cycle
mw-redirect
Vicious cycle

values:
/wiki/Credit_bubble
mw-redirect
Credit bubble

values:
/wiki/Financial_crises
mw-redirect
Financial crises

values:
nofollow
external text
http://ssrn.com/paper=1595980

values: This citation requires a reference to the specific page or range of pages in which the material appears. (November 2010)

values:
reflist mw-references-wrap
list-style-type: decimal;

values:
/wiki/Economic_theory
mw-redirect
Economic theory

values: List of important publications in economics

values:
/wiki/Austrian_school_of_economics
mw-redirect
Austrian school of economics

values: nowraplinks hlist collapsible collapsed navbox-inner

values: Category:Mathematical and quantitative methods (economics)

values: Category:Wikipedia articles needing page number citations from November 2010

values: Discussion about edits from this IP address [ctrl-alt-n]

values: A list of edits made from this IP address [ctrl-alt-y]

values: You are encouraged to create an account and log in; however, it is not mandatory

values: You're encouraged to log in; however, it's not mandatory. [ctrl-alt-o]

values:
/wiki/Aggregate_demand
View the content page [ctrl-alt-c]
c

values: Discussion about the content page [ctrl-alt-t]

values: p-namespaces navigation vectorTabs p-namespaces-label

values: portal navigation p-navigation p-navigation-label

values: Guidance on how to use and edit Wikipedia

values: About the project, what you can do, where to find things

values: A list of recent changes in the wiki [ctrl-alt-r]

values: portal navigation p-interaction p-interaction-label

values: List of all English Wikipedia pages containing links to this page [ctrl-alt-j]

values: Recent changes in pages linked from this page [ctrl-alt-k]

values:
/wiki/Wikipedia:File_Upload_Wizard
Upload files [ctrl-alt-u]
u

values: A list of all special pages [ctrl-alt-q]

values: Permanent link to this revision of the page

values: Link to connected data repository item [ctrl-alt-g]

values: Printable version of this page [ctrl-alt-p]

values: طلب إجمالي – Arabic

values: Gesamtwirtschaftliche Nachfrage – German

values: تقاضای کل – Persian

values: ביקוש מצרפי – Hebrew

values: Жиынтық сұраныс – Kazakh

values: ຍອດຄວາມຕ້ອງການ – Lao

values: Совокупный спрос – Russian

values: อุปสงค์มวลรวม – Thai

values: Сукупний попит – Ukrainian

values: mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject page-Aggregate_demand rootpage-Aggregate_demand skin-vector action-view