The indigo bunting is a small seed-eating bird in the cardinal family, Cardinalidae. It is migratory, ranging from southern Canada to northern Florida during the breeding season, from southern Florida to northern South America during the winter, it migrates by night, using the stars to navigate. Its habitat is farmland, brush areas, open woodland; the indigo bunting is related to the lazuli bunting and interbreeds with the species where their ranges overlap. The indigo bunting is a small bird, with a length of 11.5–13 cm. It displays sexual dimorphism in its coloration; the male displays brightly colored plumage during the breeding season to attract a mate. Nest-building and incubation are done by the female; the diet of the indigo bunting consists of insects during the summer months and seeds during the winter months. The indigo bunting is included in the family Cardinalidae, made up of passerine birds found in North and South America, is one of seven birds in the genus Passerina, it was described as Tanagra cyanea by Linnaeus in his 18th-century work, Systema Naturae.
The current genus name, Passerina, is derived from the Latin term passer for true sparrows and similar small birds, while the species name, cyanea, is from the Latin word meaning dark or sea blue. The indigo bunting is a close relative of the lazuli bunting and interbreeds with the species where their ranges overlap, in the Great Plains, they were declared to form a superspecies by the American Ornithologists' Union in 1983. However, according to sequencing of the mitochondrial cytochrome-b gene of members of the genus Passerina, it was determined that the indigo bunting and lazuli bunting are not, in fact, sister taxa; the indigo bunting is the sister of a "blue" and a "painted" clade. This genetic study shows these species diverged between 7.3 million years ago. This timing, consistent with fossil evidence, coincides with a late-Miocene cooling, which caused the evolution of a variety of western grassland habitats. Evolving to reduce size may have allowed buntings to exploit grass seeds as a food source.
The indigo bunting is a smallish songbird, around the size of a small sparrow. It measures 11.5–15 cm long, with a wingspan of 18–23 cm. Body mass averages 14.5 g, with a reported range of 11.2–21.4 g. During the breeding season, the adult male appears a vibrant cerulean blue. Only the head is indigo; the wings and tail are black with cerulean blue edges. In fall and winter plumage, the male has brown edges to the blue body and head feathers, which overlap to make the bird appear brown; the adult female is brown on lighter brown on the underparts. It is faintly streaked with darker markings underneath; the immature bird resembles the female in coloring, although a male may have hints of blue on the tail and shoulders and have darker streaks on the underside. The beak is conical. In the adult female, the beak is light brown tinged with blue, in the adult male the upper half is brownish-black while the lower is light blue; the feet and legs are gray. The habitat of the indigo bunting is brushy forest edges, open deciduous woods, second growth woodland, farmland.
The breeding range stretches from southern Canada to Maine, south to northern Florida and eastern Texas, westward to southern Nevada. The winter range begins in southern Florida and central Mexico and stretches south through the West Indies and Central America to northern South America, it has occurred as a vagrant in Antigua and Barbuda, Denmark, Germany, Ireland, the Netherlands Antilles, Saint Pierre and Miquelon and the United Kingdom. The indigo bunting communicates through visual cues. A sharp chip! Call is used by both sexes, is used as an alarm call if a nest or chick is threatened. A high-pitched, buzzed zeeep is used; the song of the male bird is a high-pitched buzzed sweet-sweet chew-chew sweet-sweet, lasting two to four seconds, sung to mark his territory to other males and to attract females. Each male has a single complex song, which he sings while perched on elevated objects, such as posts and bush-tops. In areas where the ranges of the lazuli bunting and the indigo bunting overlap, the males defend territories from each another.
Migration takes place in April and May and again in September and October. The indigo bunting migrates during the night, using the stars to navigate. In captivity, since it cannot migrate, it experiences disorientation in April and May and in September and October if it cannot see the stars from its enclosure; these birds are monogamous but not always faithful to their partner. In the western part of their range, they hybridize with the lazuli bunting. Nesting sites are located in dense shrub or a low tree 0.3–1 m above the ground, but up to 9 m. The nest itself is constructed of leaves, coarse grasses and strips of bark, lined with soft grass or deer hair and is bound with spider web, it is constructed by the female. The clutch consists of one to four eggs, but contains three to four; the eggs are white and unmarked, though some may be marked with brownish spots, averaging 18.7 mm × 13.7 mm in size. The eggs are incubated for 12 to 13 days and the
Carotenoids called tetraterpenoids, are organic pigments that are produced by plants and algae, as well as several bacteria and fungi. Carotenoids give the characteristic color to carrots, corn and daffodils, as well as egg yolks, rutabagas and bananas. Carotenoids can be produced from fats and other basic organic metabolic building blocks by all these organisms; the only animals known to produce carotenoids are aphids and spider mites, which acquired the ability and genes from fungi or it is produced by endosymbiotic bacteria in whiteflies. Carotenoids from the diet are stored in the fatty tissues of animals, carnivorous animals obtain the compounds from animal fat. There are over 1100 known carotenoids. All are derivatives of tetraterpenes, meaning that they are produced from 8 isoprene molecules and contain 40 carbon atoms. In general, carotenoids absorb wavelengths ranging from 400–550 nanometers; this causes the compounds to be colored yellow, orange, or red. Carotenoids are the dominant pigment in autumn leaf coloration of about 15-30% of tree species, but many plant colors reds and purples, are due to other classes of chemicals.
Carotenoids serve two key roles in plants and algae: they absorb light energy for use in photosynthesis, they protect chlorophyll from photodamage. Carotenoids that contain unsubstituted beta-ionone rings have vitamin A activity, these and other carotenoids can act as antioxidants. In the eye, meso-zeaxanthin, zeaxanthin are present as macular pigments whose importance in visual function remains under clinical research in 2017; the basic building blocks of carotenoids are isopentenyl dimethylallyl diphosphate. These two isoprene isomers are used to create various compounds depending on the biological pathway used to synthesis the isomers. Plants are known to use two different pathways for IPP production: the cytosolic mevalonic acid pathway and the plastidic methylerythritol 4-phosphate. In animals, the production of cholesterol starts by creating IPP and DMAPP using the MVA. For carotenoid production plants use MEP to generate IPP and DMAPP; the MEP pathway results in a 5:1 mixture of IPP:DMAPP.
IPP and DMAPP undergo several reactions, resulting in the major carotenoid precursor, geranylgeranyl diphosphate. GGPP can be converted into carotenes or xanthophylls by undergoing a number of different steps within the carotenoid biosynthetic pathway. Glyceraldehyde 3-phosphate and pyruvate, intermediates of photosynthesis, are converted to deoxy-D-xylulose 5-phosphate using the catalyst DXP synthase. DXP reductoisomerase reduces and rearranges the molecules within DXP in the presence of NADPH, forming MEP. Next, MEP is converted to 4--2-C-methyl-D-erythritol in the presence of CTP via the enzyme MEP cytidylyltransferase. CDP-ME is converted, in the presence of ATP, to 2-phospho-4--2-C-methyl-D-erythritol; the conversion to CDP-ME2P is catalyzed by the enzyme CDP-ME kinase. Next, CDP-ME2P is converted to 2-C-methyl-D-erythritol 2,4-cyclodiphosphate; this reaction occurs when MECDP synthase catalyzes the reaction and CMP is eliminated from the CDP-ME2P molecule. MECDP is converted to -4-hydroxy-3-methylbut-2-en-1-yl diphosphate via HMBDP synthase in the presence of flavodoxin and NADPH.
HMBDP is reduced to NADPH by the enzyme HMBDP reductase. The last two steps involving HMBPD synthase and reductase can only occur in anaerobic environments. IPP is able to isomerize to DMAPP via IPP isomerase. Two GGPP molecules condense via phytoene synthase; the subsequent conversion into all-trans-lycopene depends on the organism. Bacteria and fungi employ the bacterial phytoene desaturase for the catalysis. Plants and cyanobacteria however utilize four enzymes for this process; the first of these enzymes is a plant-type phytoene desaturase which introduces two additional double bonds into 15-cis-phytoene by dehydrogenation and isomerizes two of its existing double bonds from trans to cis producing 9,15,9’-tri-cis-ζ-carotene. The central double bond of this tri-cis-ζ-carotene is isomerized by the zeta-carotene isomerase Z-ISO and the resulting 9,9'-di-cis-ζ-carotene is dehydrogenated again via a ζ-carotene desaturase; this again introduces two double bonds. CRTISO, a carotenoid isomerase, is needed to convert the cis-lycopene into an all-trans lycopene in the presence of reduced FAD.
This all-trans lycopene is cyclized. There can be either a beta ring or an epsilon ring, each generated by a different enzyme. Alpha-carotene is produced when the all-trans lycopene first undergoes reaction with epsilon-LCY a second reaction with beta-LCY. Alpha- and beta-carotene are the most common carotenoids in the plant photosystems but they can still be further converted into xanthophylls by using beta-hydrolase and epsilon-hydrolase, leading to a variety of xanthophylls, it is believed that both DXS and DXR are rate-determining enzymes, allowing them to regulate carotenoid levels. This was discovered in an experiment where DXS and DXR were genetic
The Gouldian finch known as the Lady Gouldian finch, Gould's finch or the rainbow finch, is a colourful passerine bird, native to Australia. The Gouldian finch was described by British ornithological artist John Gould in 1844 as Amadina gouldiae, in honour of his deceased wife Elizabeth, it is known as the rainbow finch, Gould's finch, or the Lady Gouldian finch and sometimes just Gould. It is a member of the estrildid-finch family Estrildidae, sometimes considered a subfamily of Passeridae, it had been placed in the genus Chloebia, as Chloebia gouldiae. A 2009 analysis of mitochondrial DNA by Antonio Arnaiz-Villena and colleagues confirmed its placement in the genus Erythrura. However, the IUCN still calls it Chloebia goldiae. Both sexes are brightly coloured with black, green and red markings; the females tend to be less brightly coloured. One major difference between the sexes is that the male's chest is purple, while the female's is a lighter mauve. Gouldian finches are about 125–140 mm long.
Gouldian finches' heads may be black, or yellow. Considered three different kinds of finches, it is now known that these are colour variants that exist in the wild. Selective breeding has developed mutations in both body and breast colour. There are several "prominent rounded tubercles" with an "opalescent lustre" at the back of the gape; these tubercles are described as phosphorescent in spite of much scientific evidence to the contrary. It is believed that these tubercles reflect light and are not luminescent. Prior to the Australian government's ban on the export of Australian fauna, Gouldian finches were exported worldwide; these birds have resulted in viable breeding populations being held in many countries. Captive breeding has resulted in several colour mutations. Mutations vary by country, with some existing only in Australia and others existing in greater number in the United States, such as the blue bodied Gouldian; the most common body mutations in the United States are blue, pastel green, pastel blue.
There is a lutino and albino mutation in the United States, established by Winnie McAlpin of Delmar Aviaries. The number of Gouldian finches has decreased quite during the 20th century, their habitat has been altered. Early research indicated a parasite called the air sac mite was responsible for the decline of the species; this is no longer considered to be a major factor. In general, Gouldian finches are susceptible to viral infections, their beautiful colours mean that they are caught by predators. Fires are listed as the primary threat to the natural populations. Outside the breeding season, Gouldian finches join mixed flocks consisting of long-tailed finches and masked finches. Flocks can consist of up to 1,000–2,000 individuals. During the breeding season, they are found on rough scree slopes where vegetation is sparse. In the dry season, they are much more nomadic and will move to wherever their food and water can be found. Like other finches, the Gouldian finch is a seed eater, they eat 30% of their bodyweight each day.
During the breeding season, Gouldian finches feed on ripe and half-ripe grass seeds of sorghum. During the dry season, they forage on the ground for seeds. During the wet season, spinifex grass seed is an important part of their diet. So far Gouldians have been recorded eating six different species of grass seed, but researchers have yet to find evidence of insect consumption. Gouldian finches will make their nests in tree-holes, they breed in the early part of the dry season, when there is plenty of food around. When a male is courting a female, he bobs about and ruffles his feathers in an attempt to show off his bright colors, he will expand his fluff out the feathers on his forehead. After mating, the female will lay a clutch of about 4–8 eggs. Both parents help brood the eggs during the daytime, it is the female who stays on the eggs at night; when the eggs hatch, both parents care for the young. Gouldian finches leave the nest after between 19 and 23 days and are independent at 40 days old. Gouldian finches have brightly coloured gapes and call loudly when the parent birds return so that they are able to find and feed their mouths in the dark nest.
It has been shown that female Gouldian finches from Northern Australia can control the sex of their offspring by choosing mates according to their head color. A certain amount of genetic incompatibility between black and red-headed birds can result in high mortality in female offspring when birds of different head colours mate. If the female mates with a finch of different head colour, this genetic incompatibility can be addressed by over-producing sons, up to a ratio of four males to one female; this is one of the first proven instances of birds biasing the sex of their offspring to overcome genetic weaknesses. Gouldian finches are a popular species in aviculture because of their striking colors and, like all finches, they are quite low maintenance. Gouldian finches get along well with other species of grass finch and some other docile species of bird, such as waxbills and parrot finches. In the Kimberley District of Western Australia, where most wild Gouldian finch were trapped for aviculture, it was reported as one of the more common of the eleven finch species.
Until 1977, it was trapped in greater numbers than any other finch. From 1897, when finch trapping started in the
Nightjars are medium-sized nocturnal or crepuscular birds in the subfamily Caprimulginae and in the family Caprimulgidae, characterised by long wings, short legs and short bills. They are sometimes called goatsuckers, due to the ancient folk tale that they sucked the milk from goats, or bugeaters, due to their insectivore diet; some New World species are called nighthawks. The English word'nightjar' referred to the European nightjar. Nightjars are found around the world except in some islands of Oceania, they are active in the late evening and in early morning or at night nest on the ground, feed predominantly on moths and other large flying insects. Most have small feet, of little use for walking, long pointed wings, their soft plumage leaves. Some species, unusual for birds, perch along a branch, rather than across it; this helps to conceal them during the day. The common poorwill, Phalaenoptilus nuttallii, is unique as a bird that undergoes a form of hibernation, becoming torpid and with a much reduced body temperature for weeks or months, although other nightjars can enter a state of torpor for shorter periods.
Nightjars lay two patterned eggs directly onto bare ground. It has been suggested that nightjars will move their eggs and chicks from the nesting site in the event of danger by carrying them in their mouths; this suggestion has been repeated many times in ornithology books, but surveys of nightjar research have found little evidence to support this idea. Traditionally, nightjars have been divided into three subfamilies: the Caprimulginae, or typical nightjars with 79 known species, the Chordeilinae, or nighthawks of the New World with 10 known species; the two groups are similar in most respects, but the typical nightjars have rictal bristles, longer bills, softer plumage. In their pioneering DNA-DNA hybridisation work and Ahlquist found that the genetic difference between the eared nightjars and the typical nightjars was, in fact, greater than that between the typical nightjars and the nighthawks of the New World. Accordingly, they placed the eared nightjars in a separate family: Eurostopodidae, but the family has not yet been adopted.
Subsequent work, both morphological and genetic, has provided support for the separation of the typical and the eared nightjars, some authorities have adopted this Sibley-Ahlquist recommendation, the more far-reaching one to group all the owls together in the Caprimulgiformes. The listing below retains a more orthodox arrangement, but recognise the eared nightjars as a separate group. For more detail and an alternative classification scheme, see Caprimulgiformes and Sibley-Ahlquist taxonomy. †Ventivorus Mourer-Chauviré 1988 Subfamily EurostopodinaeGenus Eurostopodus Genus Lyncornis Subfamily Caprimulginae Genus Gactornis – collared nightjar Genus Nyctipolus – Genus Nyctidromus – Genus Hydropsalis – Genus Siphonorhis – Genus Nyctiphrynus – Genus Phalaenoptilus – common poorwill Genus Antrostomus – Genus Caprimulgus – Genus Setopagis – Genus Uropsalis – Genus Macropsalis – long-trained nightjar Genus Eleothreptus – Genus Systellura – Subfamily Chordeilinae Genus Chordeiles Genus Nyctiprogne Genus Lurocalis Also see a list of nightjars, sortable by common and binomial names.
The nightjars have a global distribution. They are absent from some arid deserts, such as the Sahara Desert and the deserts of central Asia, polar regions of the far north, they are found in some island groups such as Madagascar, the Seychelles, New Caledonia and the islands of Caribbean. The nighthawks have a New World distribution, the eared nightjars are Asian and Australian, whereas the typical nightjars are global in distribution. Nightjars can occupy all elevations from sea-level to 4,200 m, a number of species are montane specialists, they occupy a wide range of habitats, from deserts to rainforest, but are most common in open country with some vegetation. A number of species undertake migrations, although the secretive nature of the family means these are poorly understood. Species that live in the far north, such as the European nightjar or the common nighthawk, will move south with the onset of winter. Geolocators placed on European nightjars in southern England found they wintered in the south of the Democratic Republic of the Congo.
Other species make shorter migrations. Some species of nightjar are threatened with extinction, it has been suggested that road-kills of this species by cars is a major cause of mortality for many members of the family. This is because of their habit of roosting on roads. Working out conservation strategies for some species of nightjar presents a particular challenge common to other hard-to-see families of birds; this has nothing to do with any lack of effort. It reflects, the difficulty in locating and identifying a small number of those species of birds among the 10,000 or so that exist in the world, given the limitations of human beings. A perfect example is the Vaurie's nightjar in China's south-western Xinjiang, it has been seen for certain only once, in 1929, a specimen, held in the hand. Surveys in the 1970s and 1990s failed to find it, it is possible that it has evolved as a species that can be identified in the wild
The birds-of-paradise are members of the family Paradisaeidae of the order Passeriformes. The majority of species are found in eastern Indonesia, Papua New Guinea, eastern Australia; the family has 42 species in 15 genera. The members of this family are best known for the plumage of the males of the sexually dimorphic species, in particular the elongated and elaborate feathers extending from the beak, tail or head. For the most part they are confined to dense rainforest habitat; the diet of all species is dominated to a lesser extent arthropods. The birds-of-paradise have a variety of breeding systems, ranging from monogamy to lek-type polygamy. A number of species are threatened by habitat loss. For many years the birds-of-paradise were treated as being related to the bowerbirds. Today while both are treated as being part of the Australasian lineage Corvida, the two are now thought to be only distantly related; the closest evolutionary relatives of the birds-of-paradise are the crow and jay family Corvidae, the monarch flycatchers Monarchidae and the Australian mudnesters Struthideidae.
A 2009 study examining the mitochondrial DNA of all species to examine the relationships within the family and to its nearest relatives estimated that the family emerged 24 million years ago, older than previous estimates. The study identified five clades within the family, placed the split between the first clade, which contains the monogamous manucodes and paradise-crow, all the other birds-of-paradise, to be 10 million years ago; the second clade includes the King of Saxony bird-of-paradise. The third clade provisionally contains several genera, including Seleucidis, the Drepanornis sicklebills, Semioptera and Lophorina, although some of these are questionable; the fourth clade includes the Epimachus sicklebills and the astrapias. The final clade includes the Paradisaea birds-of-paradise; the exact limits of the family have been the subject of revision as well. The three species of satinbird were treated as a subfamily of Cnemophilinae. In spite of differences in the mouth, foot morphology and nesting habits they remained in the family until a 2000 study moved them to a separate family closer to the berrypeckers and longbills.
The same study found that the Macgregor's bird-of-paradise was a member of the large Australasian honeyeater family. In addition to these three species, a number of systematically enigmatic species and genera have been considered potential members of this family; the two species in the genus Melampitta from New Guinea, have been linked with the birds-of-paradise, but their relationships remain uncertain, more being linked with the Australian mudnesters. The silktail of Fiji has been linked with the birds-of-paradise many times since its discovery, but never formally assigned to the family. Recent molecular evidence now places the species with the fantails. Hybrid birds-of-paradise may occur when individuals of different species, that look similar and have overlapping ranges, confuse each other for their own species and crossbreed; when Erwin Stresemann realised that hybridisation among birds-of-paradise might be an explanation as to why so many of the described species were so rare, he examined many controversial specimens and, during the 1920s and 1930s, published several papers on his hypothesis.
Many of the species described in the late 19th and early 20th centuries are now considered to be hybrids, though some are still subject to dispute. Birds-of-paradise are related to the corvids. Birds-of-paradise range in size from the king bird-of-paradise at 50 g and 15 cm to the curl-crested manucode at 44 cm and 430 g; the male black sicklebill, with its long tail, is the longest species at 110 cm. In most species, the tails of the males are larger and longer than the female, the differences ranging from slight to extreme; the wings are rounded and in some species structurally modified on the males in order to make sound. There is considerable variation in the family with regard to bill shape. Bills may be long and decurved, as in the sicklebills and riflebirds, or small and slim like the Astrapias; as with body size bill size varies between the sexes, although species where the females have larger bills than the male are more common in the insect eating species. Plumage variation between the sexes is related to breeding system.
The manucodes and paradise-crow, which are monogamous, are sexually monomorphic. So are the two species of Paradigalla, which are polygamous. All these species have black plumage with varying amounts of green and blue iridescence; the female plumage of the dimorphic species is drab to blend in with their habitat, unlike the bright attractive colors found on the males. Younger males of these species have female-like plumage, sexual maturity takes a long time, with the full adult plumage not being obtained for up to seven years; this affords the younger males the protection from predators of more subdued colours, reduces hostility from adult males. The centre of bird-of-paradise diversity is the large island of New Guinea; the two that are not are the monotypic genera Lycocorax and Semioptera, both of which are endemic to the Maluku Islands, to the west of New Guinea. Of the riflebirds in the genus Ptiloris, two are endemic to the coastal forests of eastern Australia, one occurs in both Australia and New Guinea, one is only found in New Guinea.
Polymorphism in biology and zoology is the occurrence of two or more different morphs or forms referred to as alternative phenotypes, in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population; the term polyphenism can be used to clarify. Genetic polymorphism is a term used somewhat differently by geneticists and molecular biologists to describe certain mutations in the genotype, such as single nucleotide polymorphisms that may not always correspond to a phenotype, but always corresponds to a branch in the genetic tree. See below. Polymorphism is common in nature. Polymorphism functions to retain variety of form in a population living in a varied environment; the most common example is sexual dimorphism. Other examples are mimetic forms of butterflies, human hemoglobin and blood types. According to the theory of evolution, polymorphism results from evolutionary processes, as does any aspect of a species, it is modified by natural selection.
In polyphenism, an individual's genetic makeup allows for different morphs, the switch mechanism that determines which morph is shown is environmental. In genetic polymorphism, the genetic makeup determines the morph; the term polymorphism refers to the occurrence of structurally and functionally more than two different types of individuals, called zooids, within the same organism. It is a characteristic feature of cnidarians. For example, Obelia has the gastrozooids. Although in general use, polymorphism is a broad term. In biology, polymorphism has been given a specific meaning. A more specific term, when only two forms occur, is dimorphism; the term omits characteristics showing continuous variation. Polymorphism deals with forms in which the variation is discrete or bimodal or polymodal. Morphs must occupy the same habitat at the same time; the use of the words "morph" or "polymorphism" for what is a visibly different geographical race or variant is common, but incorrect. The significance of geographical variation is in that it may lead to allopatric speciation, whereas true polymorphism takes place in panmictic populations.
The term was first used to describe visible forms, but nowadays it has been extended to include cryptic morphs, for instance blood types, which can be revealed by a test. Rare variations are not classified as polymorphisms, mutations by themselves do not constitute polymorphisms. To qualify as a polymorphism, some kind of balance must exist between morphs underpinned by inheritance; the criterion is that the frequency of the least common morph is too high to be the result of new mutations or, as a rough guide, that it is greater than 1%. Polymorphism crosses several discipline boundaries, including ecology and genetics, evolution theory, taxonomy and biochemistry. Different disciplines may give the same concept different names, different concepts may be given the same name. For example, there are the terms established in ecological genetics by E. B. Ford, for classical genetics by John Maynard Smith; the shorter term morphism may be more accurate than polymorphism, but is not used. It was the preferred term of the evolutionary biologist Julian Huxley.
Various synonymous terms exist for the various polymorphic forms of an organism. The most common are morpha, while a more formal term is morphotype. Form and phase are sometimes used, but are confused in zoology with "form" in a population of animals, "phase" as a color or other change in an organism due to environmental conditions. Phenotypic traits and characteristics are possible descriptions, though that would imply just a limited aspect of the body. In the taxonomic nomenclature of zoology, the word "morpha" plus a Latin name for the morph can be added to a binomial or trinomial name. However, this invites confusion with geographically variant ring species or subspecies if polytypic. Morphs have no formal standing in the ICZN. In botanical taxonomy, the concept of morphs is represented with the terms "variety", "subvariety" and "form", which are formally regulated by the ICN. Horticulturists sometimes confuse this usage of "variety" both with cultivar and with the legal concept "plant variety".
Three mechanisms may cause polymorphism: Genetic polymorphism – where the phenotype of each individual is genetically determined A conditional development strategy, where the phenotype of each individual is set by environmental cues A mixed development strategy, where the phenotype is randomly assigned during development Selection, whether natural or artificial, changes the frequency of morphs within a population. A genetic polymorphism persists over many generations, maintained by two or more opposed and powerful selection pressures. Diver found banding morphs in Cepaea nemoralis could be seen in prefossil shells going back to t