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Evidence of common descent

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Wikimedia Commons has media related to Ice cores. During the late s, Wisconsin was a major wheat trading state, with Milwaukee as the primary hub of commerce on the Great Lakes. The story relates how Du Kang stored some cooked Chinese sorghum seeds inside a hollow tree stump on a winter day. Carbon dating is a way of determining the age of archaeological artifacts of a biological origin up to about 50, years old.

The Decline of Heather Ale

It is an abstract thing in that it does not tell us the mechanism or the reason for the various formulas. Chromosome 2 thus presents strong evidence in favour of the common descent of humans and other apes. September 17, at For the experiment he added Crenicichla alta P. These tarweeds have sticky seeds that facilitate distribution by migrant birds. Three other expeditions in the s began ice coring work:

Wheat Triticum spp is a grass species from Western Asia that was originally domesticated least 10, years ago, yet is now cultivated worldwide. Milwaukee was one city in particular that was once at the forefront of the American and indeed global grain market. Completed in by the esteemed architect Edward Townsend Mix, it was inside this Italian Renaissance style building that the main trading rooms of the Milwaukee Grain Exchange were housed.

Sadly the octagonal pit no longer survives. However, restoration of the trading room in the early s resulted in preservation of one of best examples of mural-ornamented Victorian commercial interiors in North America. This region of southwestern Wisconsin saw the earliest influx of Europeans, who principally arrived from Cornwall, England and were employed in mining lead. Lagers would soon become the norm, once large numbers of German immigrants arrived in subsequent decades and opened their own breweries.

By the end of the s there were at least 22 breweries in Wisconsin. That number rose to at least breweries in Wisconsin by the end of the s. Towns and cities across Wisconsin would grow many industries, and breweries were no exception.

The most brewing companies in operation at any one time was during the s when at least 40 breweries were in the production of beer, ales, lagers and often distilled spirits. This kicked off a tidal wave of other brewing operations that ostensibly became family businesses and wherein certain families became extremely wealthy.

In a four story Federal-Style cream city brick saloon and boarding house was built fronting Chestnut St. By the s, the brewery was known principally for brewing weiss beer and was called the Charles Gipfel Whitebeer Brewery.

However in the brewery closed due to increased competition among local breweries. The building housed various businesses over the next century, until , when the building was jacked up and relocated from Juneau Ave. Today it is a pile of bricks in an architectural salvage yard along the Milwaukee River.

One other historic Milwaukee brewery that focused primarily on brewing wheat-based beer was Eugene Louis Husting. Like many brewers before and after him, Eugene began as a brewer at the Northwestern Brewery, which was owned by Phillip Altpeter.

Husting opened his own weiss beer brewery and soda factory on the east side of 5th St. By Husting was brewing weiss beer in an 8 barrel brew kettle and selling the product in stoneware bottles. In the Husting Brewery expanded inventory to include ginger ale, soda water, cream and orange soda, raspberry wine, and cider.

As a result of prohibition , brewing beer discontinued and instead soda was exclusively produced. Following prohibition the company evolved into a beer and soda distributor until when the plant shut down. Today, the main building is still intact and is now considered the oldest standing complete brewery in Milwaukee.

The resulting Wisconsin Weizen ale that we brewed fermented quickly and will be bottled on Thursday, February 17th. Currently, it has a delightful wheat aroma, slightly hazy with a nice hop finish. In keeping with historic tradition, this wheat ale will be bottle conditioned, whereby adding a small amount of sweet wheat malt to each bottle in order to promote final carbonation. It should be ready to drink in two weeks, but will only get better with age.

Interestingly, gruit gruut was the primary ale brewed in the lower Rhine Valley and the Low Countries of northern Europe Belgium, Netherlands, Denmark during the Medieval Period and earlier. Today it is all but forgotten, except for a recent resurgence in certain small craft breweries in Belgium. It was this historic brew that was the focus for the most recent and most well attended Ale through the Ages brewing seminar at Discovery World.

This high gravity O. En lieu of hops, gruit was a combination of a variety of herbs, which each brewery guarded with secret. Other later gruit additions often included: Cardamom, Caraway, Ginger, etc. Therefore, this all-grain recipe is true to the preth Century Belgian Gruit style, which combined bog myrtle, yarrow, wild rosemary and juniper berries. Like many ancient beer recipes, the exact origin of gruit and its first use remains lost to antiquity; however, the earliest references to it come from several written sources in Flanders Belgium and the Neatherlands more than 1, years ago.

By the ninth century, governments in northern Europe asserted the right to dispense of gruit in a gruuthuse gruit house under the imperial law known as gruitrecht. This was the exclusive authority to control the benefits from unused land, from which the bog myrtle came. This governmental right was often transferred to monasteries and nobles of Belgium, France and the Netherlands. For instance, in , emperor Otto II granted rights of toll, market, minting and gruitrecht to a certain Notker of Liege Belgium in the district of Namur.

A grant to the bishop of Utrecht Holland in also placed gruitrecht among those benefits granted by the emperor. Hornsey , Unger Legend tells that Arnold, the abbeys abbot, brewed gruit ale to heal ailing builders of the abbey. Soon his reputation grew and his gruit was widely sought after, leading to his eventual status as the patron saint of Belgian Brewers. Another small artisan brewery that focuses exclusively on producing gruit is the brewpub Gruut Gentse Stadsbrouwerij.

Located in Ghent Belgium, they brew four varieties of Gruit ale. In the Count of Flanders, vassal of the French king conquered Ename 50km west of Brussels and built a Benedictine abbey on the ruins. The abbey became a central socio-religious enterprise in Ename for more than years, until it was shuttered by the French revolutionary authorities and fell into disrepair.

Excavations at the medieval abbey during the s and s uncovered a bakery, brewery, slaughterhouse, and other workshop. This definitively proves the written documentation that at least 1, years ago, formalized brewing was taking place at a large scale in Belgium. This scale reached industrial proportions by the 14 th century, as evidenced by the medieval city of Bruges Brugge , located in northern Belgium.

By the late s the city was brewing around 1. With a population of ca. Today Belgium has around breweries and brewpubs 3rd most in the EU that produce about standard beer varieties. The total beer output for was 18 million hL By comparison MillerCoors produced ca.

The monastic Trappist brewing industry is minuscule by comparison. The combined output from the seven Trappist monastery breweries in Belgium and the Netherlands is about 0.

What it comes down to, is that Belgian produced beer focuses on quality not quantity and fortunately the preservation of centuries-old styles are still being preserved for future generations. So, for those of you who are not keen on hop flavored beer, perhaps you should put gruit gruut on your next shopping list.

University of Pennsylvania Press. A large crowd was on hand for the fifteenth brewing session of Ale Through the Ages at Discovery World on December 8 th , when the historic porter brewing traditions of Britain and Northeastern United States in the 18 th th Centuries was the topic of discussion and recreation.

Once again Northern Brewer generously donated a traditional English Ale for all to enjoy during the brewing session. This Colonial Porter recipe is derived from several written sources that recount the methods and ingredients for London-style porters that would have been available in New England during the late s. Therefore the grains, hops and yeast all pay tribute to their English origins with a distinct twist of colonial enterprise using molasses, corn and maple syrup for bottle conditioning.

The invention of porter as a distinct style of ale is often credited to a Mr. A rhyme written by a J. Gutteridge around recounts Mr. Whether Harwood was indeed the progenitor of porter remains open to speculation, due to the fact that porter had widespread popularity across Britain by s, meaning it either exploded with popularity within a couple of years, or its antecedents are older.

Small beer is what everyone drinks when thirsty; it is used even in the best houses and costs only a penny the pot. Another kind of beer is called porter, meaning carrier, because the greater quantity of this beer is consumed by the working classes.

It is a thick and strong beverage, and the effect it produces, if drunk in excess, is the same as that of wine; this porter costs threepence a pot…. Therefore, if porter was so widely enjoyed across Britain less than four years after its supposed invention, then perhaps it was being produced earlier than is commonly accepted. Nevertheless, these original 18th Century porters were likely not black, rather they were probably mahogany in color, well hopped, with an original gravity between 1.

However, by the late 19th Century the ABV decreased to 1. A particularly useful account of how porters were made in London during the early s comes from a German chemist named Frederick Accum in his book Treatise on the Art of Brewing , which was published in These proportions are not absolutely essential.

An eminent establishment in this metropolis London , the grist is composed of one-fifth of pale malt, a like quantity of amber coloured and three fifths of brown malt. From the earliest days of porter, it was being exported across England, Ireland and eventually to the English Colonies in America.

It was being brewed in Edinburgh Scotland in and by there were three porter breweries operating in Dublin, Ireland. Beer brewing in North America can be traced to the earliest days of European settlement ca. William Penn describes how beer was made in the s. Our Beer was mostly made of Molasses which well boyld, until it makes a very tolerable drink, but note they make Mault, and Mault Drink begins to be common, especially in the Ordinaries and the Houses of the more substantial People.

In our great Town there is an able Man William Frampton , that has set up a large Brew House, in order to furnish the People with good Drink, both there and up and down the River. It took nearly one hundred years after Penn established his brewery for porter to be brewed in Pennsylvania.

That credit is given to two London expatriates, Robert Hare Jr. Warren, when they began brewing porter in Philadelphia in This was likely the first porter ever made in America and soon became favored by George Washington. Hairs best bottled Porter. If the price is not much enhanced by the copious droughts you took of it at the late procession. In order to maintain a steady supply of ale and to generate revenue at his estate in Monticello NY, he enlisted the help of a shipwrecked English brewer, Captain Joseph Miller, to establish a brewery there in At the dawn of the 20th century, East Coast breweries continued manufacturing porter, in addition to breweries across the country.

Anheuser-Busch, Coors and at least 22 other breweries regularly produced porter west of the Mississippi by the early s. Meaning, we can all be thankful this distinct style of ale will be with us for generations to come.

In all, 12 gallons of Colonial Porter were brewed. Tipping a hat to the traditional method of combining the mash runnings, one 6gallon carboy contained the first running, with an original gravity of 1.

The second 6 gallon carboy contained 3 gallons of the first running and 3 gallons of a second mash rinsing, to produce a moderate strength porter, with an original gravity of 1. After adding one ounce of oak chips to the fermenters in the secondary fermentation stage, the resulting oak flavor should come through in the flavor profile as the porter ages in the bottle. This ought to be a very nice porter indeed and ideally an accurate rendition of the first porters brewed in North America, when the yoke of English colonialism was thrown off!

There was great crowd on hand to participate in this brewing session to learn about the origins of this enigmatic smoked wheat ale. Today this town is known as Grodzisk, located in the province of Wielkopolski in western Poland. Therefore, this style of smoked wheat ale is known as Grodziskie Grodzisz in Polish.

The history of brewing in Western Prussia is quite extensive. Indeed in the year , breweries were in operation Unger The other 57 breweries were lager breweries producing , hl. While several styles of beer were being produced in Grodzisk, the most distinct was the Grodziskie smoked wheat ale.

Sadly, in the large Grodziskie Brewery closed when it was bought by local rival Lech Brewery, which ostensibly ended the commercial production of this style of beer in Poland. After blessing a dried well in Grodzik, it eventually refilled, which allowed brewers to produce their famous Grodziskie smoked beer. Traditional Grodziskie is produced by smoking wheat malt with oak or beech wood. This I had to do myself on a grill, as smoked wheat malt is difficult to obtain.

I cut out the base of an aluminum foil tray and stapled metal mesh screen to the bottom, in order to allow the smoke to filter through the grain bed. After letting the wheat malt soak in water overnight, it was ready to be placed in the smoker.

As an animal dies, the organic materials gradually decay, such that the bones become porous. If the animal is subsequently buried in mud , mineral salts infiltrate into the bones and gradually fill up the pores.

The bones harden into stones and are preserved as fossils. This process is known as petrification. If dead animals are covered by wind-blown sand , and if the sand is subsequently turned into mud by heavy rain or floods , the same process of mineral infiltration may occur. Apart from petrification, the dead bodies of organisms may be well preserved in ice , in hardened resin of coniferous trees figure 3a , in tar, or in anaerobic, acidic peat.

Fossilization can sometimes be a trace, an impression of a form. Examples include leaves and footprints, the fossils of which are made in layers that then harden. It is possible to decipher how a particular group of organisms evolved by arranging its fossil record in a chronological sequence. Such a sequence can be determined because fossils are mainly found in sedimentary rock. Sedimentary rock is formed by layers of silt or mud on top of each other; thus, the resulting rock contains a series of horizontal layers, or strata.

Each layer contains fossils typical for a specific time period when they formed. The lowest strata contain the oldest rock and the earliest fossils, while the highest strata contain the youngest rock and more recent fossils. A succession of animals and plants can also be seen from fossil discoveries. By studying the number and complexity of different fossils at different stratigraphic levels, it has been shown that older fossil-bearing rocks contain fewer types of fossilized organisms, and they all have a simpler structure, whereas younger rocks contain a greater variety of fossils, often with increasingly complex structures.

For many years, geologists could only roughly estimate the ages of various strata and the fossils found. They did so, for instance, by estimating the time for the formation of sedimentary rock layer by layer.

Today, by measuring the proportions of radioactive and stable elements in a given rock, the ages of fossils can be more precisely dated by scientists. This technique is known as radiometric dating.

Throughout the fossil record, many species that appear at an early stratigraphic level disappear at a later level. This is interpreted in evolutionary terms as indicating the times when species originated and became extinct.

Geographical regions and climatic conditions have varied throughout Earth's history. Since organisms are adapted to particular environments, the constantly changing conditions favoured species that adapted to new environments through the mechanism of natural selection. Despite the relative rarity of suitable conditions for fossilization, an estimated , fossil species have been named. An example of this occurs in South Africa's Beaufort Formation part of the Karoo Supergroup , which covers most of South Africa , which is rich in vertebrate fossils, including therapsids reptile-mammal transitional forms.

The fossil record is an important source for scientists when tracing the evolutionary history of organisms. However, because of limitations inherent in the record, there are not fine scales of intermediate forms between related groups of species. This lack of continuous fossils in the record is a major limitation in tracing the descent of biological groups.

When transitional fossils are found that show intermediate forms in what had previously been a gap in knowledge, they are often popularly referred to as "missing links".

There is a gap of about million years between the beginning of the Cambrian period and the end of the Ordovician period. The early Cambrian period was the period from which numerous fossils of sponges , cnidarians e. The first animal that possessed the typical features of vertebrates , the Arandaspis , was dated to have existed in the later Ordovician period.

Thus few, if any, fossils of an intermediate type between invertebrates and vertebrates have been found, although likely candidates include the Burgess Shale animal, Pikaia gracilens , [] and its Maotianshan shales relatives, Myllokunmingia , Yunnanozoon , Haikouella lanceolata , [] and Haikouichthys.

Due to an almost-complete fossil record found in North American sedimentary deposits from the early Eocene to the present, the horse provides one of the best examples of evolutionary history phylogeny. This evolutionary sequence starts with a small animal called Hyracotherium commonly referred to as Eohippus , which lived in North America about 54 million years ago then spread across to Europe and Asia.

Fossil remains of Hyracotherium show it to have differed from the modern horse in three important respects: The probable course of development of horses from Hyracotherium to Equus the modern horse involved at least 12 genera and several hundred species. The major trends seen in the development of the horse to changing environmental conditions may be summarized as follows:.

Fossilized plants found in different strata show that the marshy , wooded country in which Hyracotherium lived became gradually drier.

Survival now depended on the head being in an elevated position for gaining a good view of the surrounding countryside, and on a high turn of speed for escape from predators , hence the increase in size and the replacement of the splayed-out foot by the hoofed foot. The drier, harder ground would make the original splayed-out foot unnecessary for support.

The changes in the teeth can be explained by assuming that the diet changed from soft vegetation to grass. A dominant genus from each geological period has been selected see figure 3e to show the slow alteration of the horse lineage from its ancestral to its modern form. Prior to , paleontologists had found fossils of amphibians with necks, ears, and four legs, in rock no older than million years old.

In rocks more than million years old they could only find fish, without these amphibian characteristics. Evolutionary theory predicted that since amphibians evolved from fish, an intermediate form should be found in rock dated between and million years ago. Such an intermediate form should have many fish-like characteristics, conserved from million years ago or more, but also have many amphibian characteristics as well.

In , an expedition to islands in the Canadian arctic searching specifically for this fossil form in rocks that were million years old discovered fossils of Tiktaalik. Data about the presence or absence of species on various continents and islands biogeography can provide evidence of common descent and shed light on patterns of speciation.

All organisms are adapted to their environment to a greater or lesser extent. If the abiotic and biotic factors within a habitat are capable of supporting a particular species in one geographic area, then one might assume that the same species would be found in a similar habitat in a similar geographic area, e. This is not the case.

Plant and animal species are discontinuously distributed throughout the world:. Even greater differences can be found if Australia is taken into consideration, though it occupies the same latitude as much of South America and Africa. Marsupials like kangaroos , bandicoots , and quolls make up about half of Australia's indigenous mammal species.

The only living representatives of primitive egg-laying mammals monotremes are the echidnas and the platypus. The short-beaked echidna Tachyglossus aculeatus and its subspecies populate Australia, Tasmania , New Guinea , and Kangaroo Island while the long-beaked echidna Zaglossus bruijni lives only in New Guinea.

The platypus lives in the waters of eastern Australia. These Monotremes are totally absent in the rest of the world. Other animal distribution examples include bears , located on all continents excluding Africa, Australia and Antarctica, and the polar bear solely in the Arctic Circle and adjacent land masses. Families of sirenians are distributed around the earth's waters, where manatees are located in western Africa waters, northern South American waters, and West Indian waters only while the related family, the dugongs , are located only in Oceanic waters north of Australia, and the coasts surrounding the Indian Ocean.

The now extinct Steller's sea cow resided in the Bering Sea. The same kinds of fossils are found from areas known to be adjacent to one another in the past but that, through the process of continental drift , are now in widely divergent geographic locations. For example, fossils of the same types of ancient amphibians, arthropods and ferns are found in South America, Africa, India, Australia and Antarctica, which can be dated to the Paleozoic Era, when these regions were united as a single landmass called Gondwana.

Evidence from island biogeography has played an important and historic role in the development of evolutionary biology. For purposes of biogeography , islands are divided into two classes. Continental islands are islands like Great Britain , and Japan that have at one time or another been part of a continent. Helena , on the other hand are islands that have formed in the ocean and never been part of any continent.

Oceanic islands have distributions of native plants and animals that are unbalanced in ways that make them distinct from the biotas found on continents or continental islands. Oceanic islands do not have native terrestrial mammals they do sometimes have bats and seals , amphibians, or fresh water fish. This is despite the fact that when species such as rats, goats, pigs, cats, mice, and cane toads , are introduced to such islands by humans they often thrive.

Starting with Charles Darwin , many scientists have conducted experiments and made observations that have shown that the types of animals and plants found, and not found, on such islands are consistent with the theory that these islands were colonized accidentally by plants and animals that were able to reach them.

Such accidental colonization could occur by air, such as plant seeds carried by migratory birds, or bats and insects being blown out over the sea by the wind, or by floating from a continent or other island by sea for example, by some kinds of plant seeds like coconuts that can survive immersion in salt water , and reptiles that can survive for extended periods on rafts of vegetation carried to sea by storms.

Many of the species found on remote islands are endemic to a particular island or group of islands, meaning they are found nowhere else on earth. Examples of species endemic to islands include many flightless birds of New Zealand , lemurs of Madagascar , the Komodo dragon of Komodo , [] the dragon's blood tree of Socotra , [] Tuatara of New Zealand, [] [] and others.

Other types of endemism do not have to include, in the strict sense, islands. Islands can mean isolated lakes or remote and isolated areas. Examples of these would include the highlands of Ethiopia , Lake Baikal , fynbos of South Africa , forests of New Caledonia , and others. Examples of endemic organisms living in isolated areas include the kagu of New Caledonia, [] cloud rats of the Luzon tropical pine forests of the Philippines , [] [] the boojum tree Fouquieria columnaris of the Baja California peninsula , [] the Baikal seal [] and the omul of Lake Baikal.

Oceanic islands are frequently inhabited by clusters of closely related species that fill a variety of ecological niches , often niches that are filled by very different species on continents. Helena are called adaptive radiations because they are best explained by a single species colonizing an island or group of islands and then diversifying to fill available ecological niches.

Such radiations can be spectacular; species of the fruit fly family Drosophila , nearly half the world's total, are endemic to the Hawaiian islands. Another illustrative example from Hawaii is the silversword alliance , which is a group of thirty species found only on those islands. Members range from the silverswords that flower spectacularly on high volcanic slopes to trees, shrubs, vines and mats that occur at various elevations from mountain top to sea level, and in Hawaiian habitats that vary from deserts to rainforests.

Their closest relatives outside Hawaii, based on molecular studies, are tarweeds found on the west coast of North America.

These tarweeds have sticky seeds that facilitate distribution by migrant birds. A ring species is a connected series of populations, each of which can interbreed with its neighbors, with at least two "end" populations which are too distantly related to interbreed, though with the potential for gene flow between all the populations.

They illustrate what happens over time as populations genetically diverge, specifically because they represent, in living populations, what normally happens over time between long deceased ancestor populations and living populations, in which the intermediates have become extinct.

Richard Dawkins says that ring species "are only showing us in the spatial dimension something that must always happen in the time dimension". The combination of continental drift and evolution can sometimes be used to predict what will be found in the fossil record. Glossopteris is an extinct species of seed fern plants from the Permian.

Glossopteris appears in the fossil record around the beginning of the Permian on the ancient continent of Gondwana. Present day Glossopteris fossils are found in Permian strata in southeast South America, southeast Africa, all of Madagascar, northern India, all of Australia, all of New Zealand, and scattered on the southern and northern edges of Antarctica.

During the Permian, these continents were connected as Gondwana see figure 4c in agreement with magnetic striping, other fossil distributions, and glacial scratches pointing away from the temperate climate of the South Pole during the Permian. The history of metatherians the clade containing marsupials and their extinct, primitive ancestors provides an example of how evolutionary theory and the movement of continents can be combined to make predictions concerning fossil stratigraphy and distribution.

The oldest metatherian fossils are found in present-day China. Marsupials reached Australia via Antarctica about 50 mya, shortly after Australia had split off suggesting a single dispersion event of just one species. Geologic evidence suggests that between 30 and 40 million years ago South America and Australia were still part of the Southern Hemisphere super continent of Gondwana and that they were connected by land that is now part of Antarctica. Therefore, when combining the models, scientists could predict that marsupials migrated from what is now South America, through Antarctica, and then to present-day Australia between 40 and 30 million years ago.

A first marsupial fossil of the extinct family Polydolopidae was found on Seymour Island on the Antarctic Peninsula in The history of the camel provides an example of how fossil evidence can be used to reconstruct migration and subsequent evolution. The fossil record indicates that the evolution of camelids started in North America see figure 4e , from which, six million years ago, they migrated across the Bering Strait into Asia and then to Africa, and 3.

Once isolated, they evolved along their own lines, giving rise to the Bactrian camel and dromedary in Asia and Africa and the llama and its relatives in South America.

Camelids then became extinct in North America at the end of the last ice age. Examples for the evidence for evolution often stem from direct observation of natural selection in the field and the laboratory.

This section is unique in that it provides a narrower context concerning the process of selection. All of the examples provided prior to this have described the evidence that evolution has occurred, but has not provided the major underlying mechanism: This section explicitly provides evidence that natural selection occurs, has been replicated artificially, and can be replicated in laboratory experiments.

Scientists have observed and documented a multitude of events where natural selection is in action. The most well known examples are antibiotic resistance in the medical field along with better-known laboratory experiments documenting evolution's occurrence. Natural selection is tantamount to common descent in that long-term occurrence and selection pressures can lead to the diversity of life on earth as found today.

All adaptations—documented and undocumented changes concerned—are caused by natural selection and a few other minor processes. It is well established that, " The examples below are only a small fraction of the actual experiments and observations. Artificial selection demonstrates the diversity that can exist among organisms that share a relatively recent common ancestor. In artificial selection, one species is bred selectively at each generation, allowing only those organisms that exhibit desired characteristics to reproduce.

These characteristics become increasingly well developed in successive generations. Artificial selection was successful long before science discovered the genetic basis. Examples of artificial selection include dog breeding , genetically modified food , flower breeding, and the cultivation of foods such as wild cabbage , [] and others.

Experimental evolution uses controlled experiments to test hypotheses and theories of evolution. In one early example, William Dallinger set up an experiment shortly before , subjecting microbes to heat with the aim of forcing adaptive changes. His experiment ran for around seven years, and his published results were acclaimed, but he did not resume the experiment after the apparatus failed. A large-scale example of experimental evolution is Richard Lenski 's multi-generation experiment with Escherichia coli.

Lenski observed that some strains of E. That's just what creationists say can't happen. A study of species of Daphnia and lead pollution in the 20th century predicted that an increase in lead pollution would lead to strong selection of lead tolerance.

Researchers were able to use "resurrection ecology", hatching decades-old Daphnia eggs from the time when lakes were heavily polluted with lead. The hatchlings in the study were compared to current-day Daphnia , and demonstrated "dramatic fitness differences between old and modern phenotypes when confronted with a widespread historical environmental stressor".

Essentially, the modern-day Daphnia were unable to resist or tolerate high levels of lead this is due to the huge reduction of lead pollution in 21st century lakes. The old hatchlings, however, were able to tolerate high lead pollution. The authors concluded that "by employing the techniques of resurrection ecology, we were able to show clear phenotypic change over decades A classic example was the phenotypic change, light-to-dark color adaptation, in the peppered moth , due to pollution from the Industrial Revolution in England.

The development and spread of antibiotic -resistant bacteria is evidence for the process of evolution of species. Thus the appearance of vancomycin -resistant Staphylococcus aureus , and the danger it poses to hospital patients, is a direct result of evolution through natural selection.

The rise of Shigella strains resistant to the synthetic antibiotic class of sulfonamides also demonstrates the generation of new information as an evolutionary process. All classes of microbes develop resistance: This is to be expected when considering that all life exhibits universal genetic code and is therefore subject to the process of evolution through its various mechanisms. Another example of organisms adapting to human-caused conditions are Nylon-eating bacteria: There is scientific consensus that the capacity to synthesize nylonase most probably developed as a single-step mutation that survived because it improved the fitness of the bacteria possessing the mutation.

This is seen as a good example of evolution through mutation and natural selection that has been observed as it occurs and could not have come about until the production of nylon by humans.

Both subspecies Mimulus aurantiacus puniceus red-flowered and Mimulus aurantiacus australis yellow-flowered of monkeyflowers are isolated due to the preferences of their hummingbird and hawkmoth pollinators. The radiation of M. Phylogenetic analysis suggests two independent origins of red-colored flowers that arose due to cis -regulatory mutations in the gene MaMyb2 that is present in all M.

Further research suggested that two independent mutations did not take place, but one MaMyb2 allele was transferred via introgressive hybridization. Gene isolation and cis -regulatory functions; phylogenetic analysis; geographic location and pollinator preference; and species hybridization and speciation are just some of the areas in which data can be obtained to document the occurrence of evolution.

Like the codfish, human-caused pollution can come in different forms. Radiotrophic fungi is a perfect example of natural selection taking place after a chemical accident. Radiotrophic fungi appears to use the pigment melanin to convert gamma radiation into chemical energy for growth [] [] and were first discovered in as black molds growing inside and around the Chernobyl Nuclear Power Plant. While studying guppies Poecilia reticulata in Trinidad , biologist John Endler detected selection at work on the fish populations.

To rule out alternative possibilities, Endler set up a highly controlled experiment to mimic the natural habitat by constructing ten ponds within a laboratory greenhouse at Princeton University. Each pond contained gravel to exactly match that of the natural ponds. After capturing a random sample of guppies from ponds in Trinidad , he raised and mixed them to create similar genetically diverse populations and measured each fish spot length, spot height, spot area, relative spot length, relative spot height, total patch area, and standard body lengths.

For the experiment he added Crenicichla alta P. After 10 generations, comparisons were made between each pond's guppy populations and measurements were taken again.

Endler found that the populations had evolved dramatically different color patterns in the control and non-predator pools and drab color patterns in the predator pool.

Predation pressure had caused a selection against standing out from background gravel. In parallel, during this experiment, Endler conducted a field experiment in Trinidad where he caught guppies from ponds where they had predators and relocated them to ponds upstream where the predators did not live.

After 15 generations, Endler found that the relocated guppies had evolved dramatic and colorful patterns. Essentially, both experiments showed convergence due to similar selection pressures i. In a later study by David Reznick, the field population was examined 11 years later after Endler relocated the guppies to high streams. The study found that the populations has evolved in a number of different ways: Natural selection is observed in contemporary human populations, with recent findings demonstrating that the population at risk of the severe debilitating disease kuru has significant over-representation of an immune variant of the prion protein gene GV versus non-immune alleles.

Scientists postulate one of the reasons for the rapid selection of this genetic variant is the lethality of the disease in non-immune persons. A well known example of selection occurring in human populations is lactose tolerance.

Lactose intolerance is the inability to metabolize lactose , because of a lack of the required enzyme lactase in the digestive system. The normal mammalian condition is for the young of a species to experience reduced lactase production at the end of the weaning period a species-specific length of time.

This appears to be an evolutionarily recent around 10, years ago [and 7, years ago in Europe] [] adaptation to dairy consumption, [] and has occurred independently in both northern Europe and east Africa in populations with a historically pastoral lifestyle. Both islands lie in the Adriatic Sea near Lastovo , where the lizards founded a new bottlenecked population. While mitochondrial DNA analyses have verified that P.

A similar study was also done regarding the polycyclic aromatic hydrocarbons PAHs that pollute the waters of the Elizabeth River in Portsmouth, Virginia. This chemical is a product of creosote , a type of tar. This particular study focused on the resistance to "acute toxicity and cardiac teratogenesis" caused by PAHs. An example involving the direct observation of gene modification due to selection pressures is the resistance to PCBs in codfish.

After General Electric dumped polychlorinated biphenyls PCBs in the Hudson River from through , tomcods Microgadus tomcod living in the river were found to have evolved an increased resistance to the compound's toxic effects. Genetic samples were taken from the cods from 8 different rivers in the New England region: Genetic analysis found that in the population of tomcods in the four southernmost rivers, the gene AHR2 aryl hydrocarbon receptor 2 was present as an allele with a difference of two amino acid deletions.

Urban wildlife is a broad and easily observable case of human-caused selection pressure on wildlife. With the growth in human habitats, different animals have adapted to survive within these urban environments.

These types of environments can exert selection pressures on organisms, often leading to new adaptations. For example, the weed Crepis sancta , found in France, has two types of seed, heavy and fluffy. The heavy ones land nearby to the parent plant, whereas fluffy seeds float further away on the wind. In urban environments, seeds that float far often land on infertile concrete. Within about 5—12 generations, the weed evolves to produce significantly heavier seeds than its rural relatives. Studies have been conducted and have found striking changes to animals' more specifically mammals' behavior and physical brain size due to their interactions with human-created environments.

Animals that exhibit ecotonal variations allow for research concerning the mechanisms that maintain population differentiation. A wealth of information about natural selection, genotypic, and phenotypic variation; [] [] adaptation and ecomorphology ; [] and social signaling [] has been acquired from the studies of three species of lizards located in the White Sands desert of New Mexico.

Holbrookia maculata , Aspidoscelis inornata , and Sceloporus undulatus exhibit ecotonal populations that match both the dark soils and the white sands in the region. Research conducted on these species has found significant phenotypic and genotypic differences between the dark and light populations due to strong selection pressures. New Mexico's White Sands are a recent geologic formation approximately years old [] to possibly years old [].

This recent origin of the sands suggests that species exhibiting lighter-colored variations have evolved in a relatively short time frame. The three lizard species previously mentioned have been found to display variable social signal coloration in coexistence with their ecotonal variants.

When dark morphs were placed on white sands, their startle response was significantly diminished. This result could be due to varying factors relating to sand temperature or visual acuity; however, regardless of the cause, "…failure of mismatched lizards to sprint could be maladaptive when faced with a predator". Speciation is the evolutionary process by which new biological species arise. Biologists research species using different theoretical frameworks for what constitutes a species see species problem and species complex and there exists debate with regard to delineation.

Instances of speciation have been observed in both nature and the laboratory. Research documenting speciation is abundant. Biologists have documented numerous examples of speciation in nature—with evolution having produced far more species than any observer would consider necessary. For example, there are well over , described species of beetles. Evidence of common descent can also be found through paleontological studies of speciation within geologic strata.

The examples described below represent different modes of speciation and provide strong evidence for common descent. It is important to acknowledge that not all speciation research directly observes divergence from "start-to-finish". This is by virtue of research delimitation and definition ambiguity, and occasionally leads research towards historical reconstructions.

In light of this, examples abound, and the following are by no means exhaustive—comprising only a small fraction of the instances observed. Once again, take note of the established fact that, " Limitations exist within the fossil record when considering the concept of what constitutes a species. Paleontologists largely rely on a different framework: In addition, incidences of speciation can be interpreted from the data and numerous studies have been conducted documenting both morphological evolution and speciation.

Extensive research on the planktonic foraminifer Globorotalia truncatulinoides has provided insight into paleobiogeographical and paleoenvironmental studies alongside the relationship between the environment and evolution. In an extensive study of the paleobiogeography of G.

Cores taken of the sediment containing the three species G. A speciation event occurred at that time, whereby intermediate forms existed for quite some time. This record of the fossils also matched the already existing phylogeny constructed by morphological characters of the three species.

In a large study of five species of radiolarians Calocycletta caepa , Pterocanium prismatium , Pseudoculous vema , Eucyrtidium calvertense , and Eucyrtidium matuyamai , the researchers documented considerable evolutionary change in each lineage. Alongside this, trends with the closely related species E. The stratigraphy of this species clearly shows that this isolated population evolved into E.

It then reinvaded the region of the still-existing and static E. Eventually the invader E. From that point on, the change in size leveled to a constant. The authors suggest competition-induced character displacement. Researchers conducted measurements on 5, Rhizosolenia a planktonic diatom specimens from eight sedimentary cores in the Pacific Ocean. The core samples spanned two million years and were chronologized using sedimentary magnetic field reversal measurements. All the core samples yielded a similar pattern of divergence: The parameters used to measure the samples were consistent throughout each core.

A recent study was conducted involving the planktonic foraminifer Turborotalia. The authors extracted "51 stratigraphically ordered samples from a site within the oceanographically stable tropical North Pacific gyre ".

Two hundred individual species were examined using ten specific morphological traits size, compression index, chamber aspect ratio, chamber inflation, aperture aspect ratio, test height, test expansion, umbilical angle, coiling direction, and the number of chambers in the final whorl. Utilizing multivariate statistical clustering methods , the study found that the species continued to evolve non-directionally within the Eocene from 45 Ma to about 36 Ma. However, from 36 Ma to approximately 34 Ma, the stratigraphic layers showed two distinct clusters with significantly defining characteristics distinguishing one another from a single species.

The authors concluded that speciation must have occurred and that the two new species were ancestral to the prior species. There exists evidence for vertebrate speciation despite limitations imposed by the fossil record.

Studies have been conducted documenting similar patterns seen in marine invertebrates. A study of four mammalian genera: Hyopsodus , Pelycodus , Haplomylus three from the Eocene , and Plesiadapis from the Paleocene found that—through a large number of stratigraphic layers and specimen sampling—each group exhibited, "gradual phyletic evolution, overall size increase, iterative evolution of small species, and character divergence following the origin of each new lineage".

In another study concerning morphological trends and rates of evolution found that the European arvicolid rodent radiated into 52 distinct lineages over a time frame of 5 million years while documenting examples of phyletic gradualism, punctuation, and stasis.

Rice and George W. Salt found experimental evidence of sympatric speciation in the common fruit fly. They collected a population of Drosophila melanogaster from Davis, California and placed the pupae into a habitat maze. Newborn flies had to investigate the maze to find food. The flies had three choices to take in finding food.

Light and dark phototaxis , up and down geotaxis , and the scent of acetaldehyde and the scent of ethanol chemotaxis were the three options. This eventually divided the flies into 42 spatio-temporal habitats. They then cultured two strains that chose opposite habitats. One of the strains emerged early, immediately flying upward in the dark attracted to the acetaldehyde.

The other strain emerged late and immediately flew downward, attracted to light and ethanol. Pupae from the two strains were then placed together in the maze and allowed to mate at the food site. They then were collected. A selective penalty was imposed on the female flies that switched habitats.

This entailed that none of their gametes would pass on to the next generation. After 25 generations of this mating test, it showed reproductive isolation between the two strains. They repeated the experiment again without creating the penalty against habitat switching and the result was the same; reproductive isolation was produced. A study of the gall-forming wasp species Belonocnema treatae found that populations inhabiting different host plants Quercus geminata and Q.

Virginiana exhibited different body size and gall morphology alongside a strong expression of sexual isolation. The study hypothesized that B. The researchers sampled gall wasp species and oak tree localities, measured body size right hand tibia of each wasp , and counted gall chamber numbers. In addition to measurements, they conducted mating assays and statistical analyses. Genetic analysis was also conducted on two mtDNA sites base pairs from cytochrome C and base pairs from cytochrome oxidase to "control for the confounding effects of time since divergence among allopatric populations ".

In an additional study, the researchers studied two gall wasp species B. This study further confounded prerequisites to speciation. One example of evolution at work is the case of the hawthorn fly, Rhagoletis pomonella , also known as the apple maggot fly, which appears to be undergoing sympatric speciation.

A distinct population emerged in North America in the 19th century some time after apples , a non-native species, were introduced. This apple-feeding population normally feeds only on apples and not on the historically preferred fruit of hawthorns. The current hawthorn feeding population does not normally feed on apples. The London Underground mosquito is a species of mosquito in the genus Culex found in the London Underground.

It evolved from the overground species Culex pipiens. This mosquito, although first discovered in the London Underground system, has been found in underground systems around the world.

It is suggested that it may have adapted to human-made underground systems since the last century from local above-ground Culex pipiens , [] although more recent evidence suggests that it is a southern mosquito variety related to Culex pipiens that has adapted to the warm underground spaces of northern cities. The two species have very different behaviours, [] are extremely difficult to mate, [] and with different allele frequency, consistent with genetic drift during a founder event.

When the two varieties were cross-bred the eggs were infertile suggesting reproductive isolation. The genetic data indicates that the molestus form in the London Underground mosquito appears to have a common ancestry, rather than the population at each station being related to the nearest aboveground population i. Byrne and Nichols' working hypothesis was that adaptation to the underground environment had occurred locally in London only once.

These widely separated populations are distinguished by very minor genetic differences, which suggest that the molestus form developed: Debate exists determining when the isthmus of Panama closed. Much of the evidence supports a closure approximately 2. The botanist Verne Grant pioneered the field of plant speciation with his research and major publications on the topic. Debate exists in the field concerning which framework should be applied in the research.

Both hybridization and polyploidy have also been found to be major contributors to plant speciation. Furthermore, recent research suggests that sexual selection , epigenetic drivers, and the creation of incompatible allele combinations caused by balancing selection also contribute to the formation of new species. Studies have also suggested that, due to "the sessile nature of plants Hybridization between two different species sometimes leads to a distinct phenotype.

This phenotype can also be fitter than the parental lineage and as such, natural selection may then favor these individuals. Eventually, if reproductive isolation is achieved, it may lead to a separate species. However, reproductive isolation between hybrids and their parents is particularly difficult to achieve and thus hybrid speciation is considered a rare event. However, hybridization resulting in reproductive isolation is considered an important means of speciation in plants, [] since polyploidy having more than two copies of each chromosome is tolerated in plants more readily than in animals.

Polyploidy is important in hybrids as it allows reproduction, with the two different sets of chromosomes each being able to pair with an identical partner during meiosis. It is considered very rare but has been shown in Heliconius butterflies [] and sunflowers.

Polyploid speciation, which involves changes in chromosome number, is a more common phenomenon, especially in plant species. Polyploidy is a mechanism that has caused many rapid speciation events in sympatry because offspring of, for example, tetraploid x diploid matings often result in triploid sterile progeny. It has been suggested that many of the existing plant and most animal species have undergone an event of polyploidization in their evolutionary history.

Rare instances of polyploid mammals are known, but most often result in prenatal death. Researchers consider reproductive isolation as key to speciation. Botanists often consider the zoological classifications of prezygotic and postzygotic barriers as inadequate. The creation of a new allopolyploid species Mimulus peregrinus was observed on the banks of the Shortcleuch Water—a river in Leadhills, South Lanarkshire, Scotland. Parented from the cross of the two species Mimulus guttatus containing 14 pairs of chromosomes and Mimulus luteus containing pairs from a chromosome duplication , M.

Due to the nature of these species, they have the ability to self-fertilize. Because of its number of chromosomes it is not able to pair with M. Raphanobrassica includes all intergeneric hybrids between the genera Raphanus radish and Brassica cabbages, etc.

Plants of this parentage are now known as radicole. Two other fertile forms of Raphanobrassica are known. Raparadish, an allopolyploid hybrid between Raphanus sativus and Brassica rapa is grown as a fodder crop. The Raphanobrassica is a fascinating plant, because in spite of its hybrid nature , it is not sterile. This has led some botanists to propose that the accidental hybridization of a flower by pollen of another species in nature could be a mechanism of speciation common in higher plants.

The Welsh groundsel is an allopolyploid, a plant that contains sets of chromosomes originating from two different species. Sometime in the early 20th century, an accidental doubling of the number of chromosomes in an S. The York groundsel Senecio eboracensis is a hybrid species of the self-incompatible Senecio squalidus also known as Oxford ragwort and the self-compatible Senecio vulgaris also known as common groundsel.

It resulted from a backcrossing of the F1 hybrid of its parents to S. Other hybrids descended from the same two parents are known. Some are infertile, such as S. Other fertile hybrids are also known, including S. Morphological and genetic evidence support the status of S. Kirsten Bomblies et al. When the genes are passed down, it ignites a reaction in the hybrid plant that turns its own immune system against it.

In the parents, the genes were not detrimental, but they evolved separately to react defectively when combined.

Along with allocating the same indicators, the 20 plants also shared a comparable collection of genetic activity in a group of 1, genes. In almost all of the cases, Bomblies discovered that only two genes were required to cause the autoimmune response. Bomblies looked at one hybrid in detail and found that one of the two genes belonged to the NB-LRR class , a common group of disease resistance genes involved in recognizing new infections.

When Bomblies removed the problematic gene, the hybrids developed normally. Tragopogon is one example where hybrid speciation has been observed. In the early 20th century, humans introduced three species of salsify into North America.

These species, the western salsify Tragopogon dubius , the meadow salsify Tragopogon pratensis , and the oyster plant Tragopogon porrifolius , are now common weeds in urban wastelands. In the s, botanists found two new species in the regions of Idaho and Washington , where the three already known species overlapped.

One new species, Tragopogon miscellus , is a tetraploid hybrid of T. The other new species, Tragopogon mirus , is also an allopolyploid, but its ancestors were T. These new species are usually referred to as "the Ownbey hybrids" after the botanist who first described them. A study published in March found that when these two plants were introduced to North America in the s, they mated and doubled the number of chromosomes in there hybrid Tragopogon miscellus allowing for a "reset" of its genes, which in turn, allows for greater genetic variation.

Professor Doug Soltis of the University of Florida said, "We caught evolution in the act…New and diverse patterns of gene expression may allow the new species to rapidly adapt in new environments".

The hybridizations have been reproduced artificially in laboratories from to present day. The bird species, Sylvia atricapilla , commonly referred to as blackcaps, lives in Germany and flies southwest to Spain while a smaller group flies northwest to Great Britain during the winter.

Gregor Rolshausen from the University of Freiburg found that the genetic separation of the two populations is already in progress. The differences found have arisen in about 30 generations. Stuart Bearhop from the University of Exeter reported that birds wintering in England tend to mate only among themselves, and not usually with those wintering in the Mediterranean.

The shortfin molly Poecilia mexicana is a small fish that lives in the Sulfur Caves of Mexico. Years of study on the species have found that two distinct populations of mollies—the dark interior fish and the bright surface water fish—are becoming more genetically divergent.

Tobler collected the bug and both types of mollies, placed them in large plastic bottles, and put them back in the cave.

After a day, it was found that, in the light, the cave-adapted fish endured the most damage, with four out of every five stab-wounds from the water bugs sharp mouthparts. In the dark, the situation was the opposite. The mollies' senses can detect a predator's threat in their own habitats, but not in the other ones.

Moving from one habitat to the other significantly increases the risk of dying. Tobler plans on further experiments, but believes that it is a good example of the rise of a new species. A remarkable example of natural selection, geographic isolation, and speciation in progress is the relationship between the polar bear Ursus maritimus and the brown bear Ursus arctos.

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