{"id":371,"date":"2019-03-27T09:45:17","date_gmt":"2019-03-27T09:45:17","guid":{"rendered":"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/?post_type=chapter&#038;p=371"},"modified":"2019-05-09T12:16:09","modified_gmt":"2019-05-09T12:16:09","slug":"evidences-of-evolution","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/chapter\/evidences-of-evolution\/","title":{"rendered":"Evidences of Evolution"},"content":{"raw":"<div><span style=\"float: right;\"><a href=\"https:\/\/youtu.be\/3rsSkWlaMUg\" target=\"_blank\" rel=\"noopener\"><img src=\"http:\/\/epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/2018\/11\/download.png\" alt=\"epgp books\" width=\"75px\" height=\"75px;\" \/><\/a>\r\n<\/span><\/div>\r\n\r\n<div>\r\n\r\n&nbsp;\r\n\r\n<strong>Contents:<\/strong>\r\n<ul>\r\n \t<li>Introduction<\/li>\r\n \t<li>The concept of Evolution<\/li>\r\n \t<li>How Do We Know That Evolution Has Occurred?: Evidences of evolution<\/li>\r\n \t<li>Case studies for evolution<\/li>\r\n \t<li><strong style=\"text-align: initial;font-size: 1em\">Summary<\/strong><\/li>\r\n<\/ul>\r\n<\/div>\r\n&nbsp;\r\n\r\n<strong style=\"text-align: initial;font-size: 1em\">INTRODUCTION<\/strong>\r\n<div>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">The Nobel Prize winning scientist Linus Pauling aptly described science as the search for truth. Science does this by continuously comparing its theories objectively with evidence in the natural world. When theories no longer conform to the evidence, they are modified or rejected in favor of new theories that do conform. In other words, science constantly tries to prove its assumptions to be false and rejects implausible explanations. In this way, scientific knowledge and understanding grow over time.<\/p>\r\n&nbsp;\r\n\r\n<strong>EVOLUTION: THE CONCEPT<\/strong>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Evolution is change in heritable traits of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organisation, including the level of species, individual organisms, and at the level of molecular eviolution.<\/p>\r\n&nbsp;\r\n\r\nThere are different theories of evolution\r\n\r\n&nbsp;\r\n\r\nLamarckism\r\n\r\n&nbsp;\r\n\r\nDarwinism\r\n\r\n&nbsp;\r\n\r\nPangenesis theory\r\n\r\n&nbsp;\r\n\r\nSynthetic theory of evolution\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">The synthetic theory synthesized various concepts such as Darwin\u2019s natural selection, Mendelian genetics, mutation theory and population genetics to understand the course and mechanism of evolution.<\/p>\r\n&nbsp;\r\n\r\n<strong>How Do We Know That Evolution Has Occurred?<\/strong>\r\n\r\n&nbsp;\r\n\r\nThe evidence for evolution has primarily come from four sources:\r\n\r\n&nbsp;\r\n\r\n1.\u00a0\u00a0\u00a0\u00a0\u00a0 fossil record of change in earlier species\r\n\r\n2.\u00a0\u00a0\u00a0\u00a0\u00a0 chemical and anatomical similarities of related life forms\r\n\r\n3.\u00a0\u00a0\u00a0\u00a0\u00a0 geographical distribution of related species\r\n\r\n4.\u00a0\u00a0\u00a0\u00a0\u00a0 recorded genetic changes in living organisms over many generations\r\n\r\n&nbsp;\r\n\r\n<strong>Fossil Record<\/strong>\r\n\r\n&nbsp;\r\n\r\n<span style=\"text-align: justify;font-size: 1em\">Remains of animals and plants found in <\/span><span style=\"text-align: justify;font-size: 1em\">sedimentary <\/span><span style=\"text-align: justify;font-size: 1em\">rock deposits give us an indisputable record of past changes through vast periods of time. This evidence attests to the fact that there has been a tremendous variety of living things. Some extinct species had traits that were transitional between major groups of organisms. Their existence confirms that species are not fixed but can evolve into other species over time.<\/span>\r\n\r\n<\/div>\r\n&nbsp;\r\n<p style=\"text-align: justify\">The evidence also shows that what have appeared to be gaps in the fossil record are due to incomplete data collection. The more that we learn about the evolution of specific species lines, the more that these so-called gaps or \"missing links in the chain of evolution\" are filled with transitional fossil specimens. One of the first of these gaps to be filled was between small bipedal dinosaurs and birds.<\/p>\r\n<img class=\"aligncenter size-full wp-image-374\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-180.png\" alt=\"\" width=\"207\" height=\"234\" \/>\r\n<p style=\"text-align: justify\">Just two years after Darwin published <em>On the Origin of Species<\/em>, a 150-145 million year old fossil of <em>Archaeopteryx<\/em> was found in southern Germany. It had jaws with teeth and a long bony tail like dinosaurs, broad wings and feathers like birds, and skeletal features of both. This discovery verified the assumption that\u00a0 birds\u00a0 had\u00a0 reptilian ancestors.<\/p>\r\n<img class=\"aligncenter size-full wp-image-375\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-181.png\" alt=\"\" width=\"580\" height=\"168\" \/>\r\n<div>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Since the discovery of <em>Archaeopteryx<\/em>, there have been many other crucial evolutionary gaps filled in the fossil record. Perhaps, the most important one, from our human perspective, was that between apes and <em>Homo sapiens<\/em>. Since the 1920's, there have been literally hundreds of well-dated intermediate fossils found in Africa that were transitional species leading from apes to humans over the last 6-7 million years.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">The fossil record also provides abundant evidence that the complex animals and plants of today were preceded by earlier simple ones. In addition, it shows that multicelled organisms evolved only after the first single-celled ones. This fits the predictions of evolutionary theory.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">Living things on earth are fundamentally similar in the way that their basic anatomical structures develop. No matter whether they are simple single-celled protozoa or highly complex organisms with billions of cells, they all begin as single cells that reproduce themselves by similar division processes. After a limited life span, they also all grow old and die.<\/span><\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\"><span style=\"font-size: 1em\">All living things on earth share the ability to create complex molecules out of carbon and a few other elements. In fact, 99% of the proteins, carbohydrates, fats, and other molecules of living things are made from only 6 of the 92 most common elements. This is not a mere coincidence.<\/span><\/p>\r\n\r\n<\/div>\r\n&nbsp;\r\n<p style=\"text-align: justify\">All plants and animals receive their specific characteristics from their parents by inheriting particular combinations of genes. Molecular biologists have discovered that genes are, in fact, segments of <a href=\"http:\/\/anthro.palomar.edu\/evolve\/glossary.htm#DNA\">DNA <\/a>molecules in our cells.<\/p>\r\n<img class=\"aligncenter size-full wp-image-376\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-182.png\" alt=\"\" width=\"210\" height=\"134\" \/>\r\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">These segments of DNA contain chemically coded recipes for creating proteins by linking together particular <\/span><span style=\"text-align: initial;font-size: 1em\">amino acids <\/span><span style=\"text-align: initial;font-size: 1em\">in specific sequences.<\/span><\/p>\r\n<img class=\"aligncenter size-full wp-image-377\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-183.png\" alt=\"\" width=\"171\" height=\"241\" \/>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">All of the tens of thousands of types of proteins in living things are mostly made of only 20 kinds of amino acids. Despite the great diversity of life on our planet, the simple language of the DNA code is the same for all living things. This is evidence of the fundamental molecular unity of life.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">In addition to molecular similarities, most living things are alike in that they either get the energy needed for growth,repair, and reproduction directly from sunlight, by photosynthesis , or they get it indirectly by consuming green plants and other organisms that eat plants.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">All of these major chemical and anatomical similarities between living things can be most logically accounted for by assuming that they either share a common ancestry or they came into existence as a result of similar natural processes.<\/p>\r\n&nbsp;\r\n\r\n<strong style=\"text-align: initial;font-size: 1em\">Geographical Distribution of the Related Species<\/strong>\r\n<div>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">The geographic distribution of related species is another example for the past evolution. This is also niw clear that many of the major isolated lands and group of islands hve evolved their distinctive plants and animals communities. For example, in Australia, before humans arrived their before 60-40,000 years ago, had no advanced terrestrial placental mammals like cats, dogs, bears, horses rather had more than 100 species of kangaroos, koalas, and other marsupials. It is also reported that the terrestrial mammals were entirely absent from the even more isolated islands that make up Hawaii and New Zealand. All of these had a larger number of plant, insect, and bird species that were found nowhere else in the world. This can be explained through evolution in isolation of Australia\u2019s, New Zealand\u2019s and Hawaii\u2019s biotic environment from the rest of the world for million of years<\/p>\r\n&nbsp;\r\n\r\n<strong>Genetic Changes over Generations<\/strong>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">The environment of earth is continuously changing, usually in subtle and complex ways. The changes when go beyond a threshold when it is beyond the toleration of a population of organisms mass deaths occur. This also goes with the observation of Chales Darwin that not all the organisms would peish after this. Fortunately, natural populations have genetic diversity. Only the organisms whose internal characteristics allow them to survive an environmental crisis are likely the only ones able to reproduce.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">Lately these traits will be more common in the next generation--evolution of the population will have occurred.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">The process of this selection (natural) resulting in evolution can be demonstrated over a 24 hour period in a laboratory Petri dish of bacteria living in a nutrient medium. Whenever higher or lethal dose of antibiotic is added, majority of the bacteria will die-off. While majority of these die only few of the bacteria usually are immune and survive. The next generation is mostly immune because they have inherited immunity from those who have survived. The purple bacteria in the Petri dishes shown below in the figure showing that the bacterial population has evolved.<\/p>\r\n\r\n<\/div>\r\n<img class=\"aligncenter size-full wp-image-378\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-184.png\" alt=\"\" width=\"322\" height=\"172\" \/>\r\n<p style=\"text-align: justify\">Similar phenomenon is observed in human bodies as well where the body reacts when an antibiotic drug is administered and its unable to completely eliminate a bacterial infection. Due to this the medical doctors recommend the antibiotic to be taken even after the disease doe not persists as a course. They do not want to allow any potentially antibiotic resistant bacteria to survive.<\/p>\r\n<img class=\"aligncenter size-full wp-image-379\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-185.png\" alt=\"\" width=\"157\" height=\"167\" \/>\r\n<p style=\"text-align: justify\">Selective breeding has paved way for the development of new species of planyts and animals. The process is similar to the bacterial experiment discussed above. The organisms are selected on the basis of the traits required for the development of particular breed. All those individuals who lack the desirable characteristics are not allowed to breed. Therefore, the following generations more commonly have the desired traits.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">Similar phenomenon is observed in human bodies as well where the body reacts when an antibiotic drug is administered and its unable to completely eliminate a bacterial infection. Due to this the medical doctors recommend the antibiotic to be taken even after the disease doe not persists as a course. They do not want to allow any potentially antibiotic resistant bacteria to survive.<\/span><\/p>\r\n\r\n<div>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Selective breeding has paved way for the development of new species of planyts and animals. The process is similar to the bacterial experiment discussed above. The organisms are selected on the basis of the traits required for the development of particular breed. All those individuals who lack the desirable characteristics are not allowed to breed. Therefore, the following generations more commonly have the desired traits.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">Species that mature and reproduce large numbers in a short amount of time have a potential for very fast evolutionary changes. Insects and microorganisms<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">often evolve at such rapid rates that our actions to combat them quickly lose their effectiveness. We must constantly develop new pesticides, antibiotics, and other measures in an ever escalating biological arms race with these creatures. Unfortunately, there are a few kinds of insects and microbes that are now significantly or completely resistant to our counter measures, and some of these species are responsible for devastating crop losses and deadly diseases.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">If evolution has occurred, there should be many anatomical similarities among varieties and species that have diverged from a common ancestor. Those species with the most recent common ancestor should share the most traits. For instance, the many anatomical similarities of wolves, dogs, and other members of the genus <em>Canis<\/em> are due to the fact that they are descended from the same ancient canine species and still share 99.8% of their genes. Wolves and dogs also share similarities with foxes, indicating a slightly more distant ancestor with them.<\/p>\r\n\r\n<\/div>\r\n<img class=\"aligncenter size-full wp-image-380\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-186.png\" alt=\"\" width=\"153\" height=\"137\" \/>\r\n\r\n<img class=\"aligncenter size-full wp-image-381\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-187.png\" alt=\"\" width=\"445\" height=\"192\" \/>\r\n<div>\r\n<p style=\"text-align: justify\">Evolution can be a very slow process. But actually we now have numerous examples where long term studies of populations document evolution happening within decades. Through meticulous measurement and attention to detail we can watch evolution in action. Evolution within populations is called microevolution and the changes are often small, but adding up these small differences through time is how evolution works.<\/p>\r\n&nbsp;\r\n\r\n<strong>Case study 1: Darwin\u2019s Finches<\/strong>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">One of the best studied examples of evolution in action comes from work done by Prof. Peter Grant and his wife Dr. Rosemary Grant on the beak size of Galapagos finches (aka Darwin\u2019s finches).<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">These birds live on the Galapagos Islands, off the coast of Ecuador, right on the equator. For almost 40 years researchers have been living on these islands and taking detailed measurements of the birds. They focus on a few islands in particular, one is called Daphne. Daphne is small enough to be able to count all the birds on the island, and catch them often enough to keep track of their growth and size.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">Survival isn\u2019t easy on these islands; it\u2019s baking hot during the day, freezing cold at night and there isn\u2019t much food. Because of this, the birds have very specialised feeding behaviours. We see them now as 13 species all feeding on different things in different ways. But all these 13 species evolved from one common ancestor. Originally a South American finch colonised the island and became distinct from the mainland population (peripartic speciation). Different sub-populations of the birds also began to occupy new habitats and specialise on different ways of feeding. Selection kept these groups apart because hybrids were less fit (parapatric and sympatric speciation).<\/p>\r\n\r\n<\/div>\r\n<img class=\"aligncenter size-full wp-image-382\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-188.png\" alt=\"\" width=\"298\" height=\"288\" \/>\r\n<div>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Each ground finch species has evolved a beak adapted to target different categories of seeds. The small ground finch has a small beak (3-4mm deep) and eats mostly small seeds, the medium ground finch has a medium sized beak (5mm deep) and eats moderately sized seeds and the large ground finch targets larger seeds that the others can\u2019t crack open; it has a heavy duty beak (8mm deep) to allow it to do so.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">The weather affects the abundance of seeds on the island. When it's very hot and dry few seeds are produced and competition for food increases amongst the finches. The Grant\u2019s research team were on the island during one dry spell that lasted much longer than usual. The island became very dry, vegetation died back and plants stopped producing seeds. They watched and recorded measurements about the seeds and beak sizes as the birds ate their way through the last of the easily eaten nuts and many starved and died. After many months without rain only the biggest, toughest and most spine covered seeds were left.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">The researchers found that the lack of food had increased competition among the birds. The smaller beaked birds fared worst and amongst the large ground finch there was very strong selection for larger beaks, because the individuals with the largest beaks were the only ones able to eat. In fact, compared to the average depth of beak at the start of this dry period, by the end of it the average beak depth was 1mm bigger.<\/p>\r\n\r\n<\/div>\r\n<img class=\"aligncenter size-full wp-image-383\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-189.png\" alt=\"\" width=\"263\" height=\"196\" \/>\r\n<div>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Another example comes from Prof. David Reznick\u2019s work on guppies which live in rivers in a Caribbean Island called Trinidad. The guppies either live with or without the presence of a predator fish, a pike-like thing. So some populations grow up having to avoid being eaten, others don\u2019t. The presence of the predator changes the selective pressure acting on the guppies, so they have evolved different traits.<\/p>\r\n&nbsp;\r\n\r\nThe ones living with predators grow up faster, mature at smaller sizes and reproduce earlier; they need to breed as soon as possible because they could get eaten any time. In rivers without predators the guppies can grow up at a more leisurely pace and put more energy into their offspring.\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Prof. Reznick\u2019s team have done a series of experiments where they took fish from each population and put them into rivers which previously did not contain guppies. Some of these new rivers had predators in them, others didn\u2019t. The experiment was set up so populations from rivers with predators were moved to rivers without predators and vice versa. As a control they also moved populations from rivers with predators to different rivers with predators, and the same for populations from rivers lacking predators.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">The team left their fish in their new homes and came back after just ten years. Their prediction was that evolution should be replicated: the fish would evolve larger body sizes and delayed maturation in rivers without predators, and evolve smaller body sizes and earlier maturation in rivers with predators. Sure enough that\u2019s exactly what they found! This proved the natural populations were adapted to maximise their reproductive output by adopting different strategies depending on their circumstances.<\/p>\r\n\r\n<\/div>\r\n<img class=\"aligncenter size-full wp-image-384\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-190.png\" alt=\"\" width=\"310\" height=\"239\" \/>\r\n<div>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Another fish example is armor plating in sticklebacks. Since the last ice age, three-spined sticklebacks have been very successful, spreading from marine populations up into rivers and lakes across the world. As they have spread, sticklebacks have evolved a number of adaptations to help them evade predators.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">Some populations have large pelvic spines, which make them harder to swallow so protect them against big predator fish. Some populations lack the spines, these fish usually swim quite close to the bottom of the water bed, within reach of crustacean predators which can use their claws to reach up and grab the pelvic spines of the sticklebacks. For these populations, lacking the pelvic spines helps them to avoid a different sort of predator. Researchers have even been able to pinpoint the gene involved in pelvic reduction, it's called <em>Pitx1<\/em> and seems to be involved in multiple, independent evolutionary events when spines have been lost.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">Another defensive trait is armor plating. Sticklebacks which live in marine environments have a series of bony plates along either side of their body. These make it difficult for predators to eat the fish once they\u2019ve caught it, so often the stickleback will get away. The problem with armour plating is that it slows the fish down, but since in marine environments water tends to be quite clear it\u2019s unlikely the stickleback could escape it\u2019s predator by swimming away.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">In freshwater environments however the water can be a lot murkier and there could be selective pressure to bolt quickly when attacked so as to disappear into the murk. This would require the armour plates to be lost. In fresh water sticklebacks around the world this is what is seen. The number of plates is reduced, and sticklebacks go for a quick escape strategy of defence. Scientists have also pinpointed\u00a0<span style=\"text-align: initial;font-size: 1em\">the gene involved in this phenotypic change, its called <\/span><em style=\"text-align: initial;font-size: 1em\">ectodysplasin<\/em><span style=\"text-align: initial;font-size: 1em\">, and, like <\/span><em style=\"text-align: initial;font-size: 1em\">Pitx1<\/em><span style=\"text-align: initial;font-size: 1em\">, it's responsible for similar changes in multiple independent cases.<\/span><\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">The whole idea of natural selection rests on the gradual adaptation of organisms to their environment. If the environment changes, some individuals will have characteristics that make them better able to cope than others, and these individuals will be more likely to pass on their genes to future generations.<\/span><\/p>\r\n\r\n<\/div>\r\n<img class=\"aligncenter size-full wp-image-385\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-191.png\" alt=\"\" width=\"332\" height=\"239\" \/>\r\n<div>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">The environment is changing. It is now widely accepted that carbon dioxide levels are rising and that this is causing temperatures to increase via the greenhouse effect. Global warming is a reality, and it will have major effects on many aspects of our environment, including...<\/p>\r\n&nbsp;\r\n<ul>\r\n \t<li>Temperature rises of between 2 and 12 \u00b0C by 2100<\/li>\r\n \t<li>Changes to rainfall and humidity levels<\/li>\r\n \t<li>The destruction of habitats due to flooding, droughts or extreme weather, plus secondary events like forest fires<\/li>\r\n \t<li>Changing disease patterns<\/li>\r\n \t<li>Ocean acidification (decreased pH of seawater due to the formation of carbonic acid when carbon dioxide dissolves in water)<\/li>\r\n \t<li>Changes in ocean currents and sea levels<\/li>\r\n<\/ul>\r\n<\/div>\r\n&nbsp;\r\n<p style=\"text-align: justify\">These changes will and are already affecting life on earth. We are already witnessing changes to the genomes of organisms resulting in shifts in metabolic rate, breeding season, migration patterns, disease dynamics and food availability. All of these changes will upset the delicate balance of ecosystems.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">Recent studies suggest the possibility of mass extinctions as a result of these changes \u2013 this is because rapid changes in the environment are likely to be challenging for organisms as they have adapted over thousands of years to suit particular niches (roles within the community). Some may be suited to the new environment but others will be forced to evolve in new ways to survive in the new environment. As a result there is a possibility that the rate of evolution may rise as selection pressure increases, and as a result large changes to biodiversity may result.<\/p>\r\n&nbsp;\r\n\r\n<img class=\"aligncenter size-full wp-image-386\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-192.png\" alt=\"\" width=\"320\" height=\"216\" \/>\r\n<div>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">The changing climate is already resulting in earlier springs, longer summers and milder winters. It is this, rather than direct temperature change, which many organisms are battling against.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">During the past forty years, scientists have observed species migrating, reproducing and developing earlier. A good example of this is the European great tit. European great tits are evolving different breeding times to ensure maximum food supplies to increase offspring survival. This is because Winter Moth caterpillars are maturing earlier in spring due to rising temperatures and these caterpillars are a staple food source for these birds. So individuals which can bring forward their egg-laying ensure greater food availability for their chicks and so these individuals are more successful. Research has shown that birds lay their eggs two weeks earlier than they did in the 1970s, a clear example of how organisms are altering in response to global warming. Similarly, Canadian red squirrels are breeding earlier allowing them to gather more pinecones to tide them over during winter.<\/p>\r\n\r\n<\/div>\r\n<div>\r\n<p style=\"text-align: justify\">Another example is the mosquito <em>Wyeomyia smithii<\/em>. In response to changes to length of day insects are developing later and gradually the genomes of northern individuals are coming to resemble more closely those of insects living near the equator.<\/p>\r\n&nbsp;\r\n<p style=\"text-align: justify\">In fact, several species depend on day length to tell them when to migrate, mate or go into hibernation. Other cues such as daily length of warmth (thermo period), rainfall and food availability are also crucial in allowing organisms to decide when to perform these tasks. Global warming is affecting all these cues except for day length.<\/p>\r\n&nbsp;\r\n\r\n<strong>Summary<\/strong>\r\n<ul>\r\n \t<li style=\"text-align: justify\">Evolution is change in heritable traits of biological populations over successive generations.<\/li>\r\n \t<li style=\"text-align: justify\">Evolutionary processes give rise to diversity at every level of biological organisation, including the level of species, individual organisms, and at the level of molecular evolution<\/li>\r\n \t<li>There are different theories of evolution<\/li>\r\n \t<li style=\"text-align: justify\">The evidence for evolution has primarily come from four sources: fossil record, chemical and anatomical similarities, geographical distribution and recorded genetic changes.<\/li>\r\n \t<li style=\"text-align: justify\">Evolution within populations is called microevolution and the changes are often small, but adding up these small differences through time is how evolution works.<\/li>\r\n \t<li>There is a tendency in all organisms to increase in geometric ratio.<\/li>\r\n \t<li style=\"text-align: justify\">Biological variations with regard to structural, physiological and behavioural traits occur among the individuals.<\/li>\r\n \t<li style=\"text-align: justify\">Those who have selective advantage tend to survive.<\/li>\r\n \t<li style=\"text-align: justify\">They reproduce more number of offspring than those who are less adaptive.<\/li>\r\n \t<li style=\"text-align: justify\">The accumulation of advantageous traits in future generations gradually bring changes in the species and eventually a new species may be evolved<\/li>\r\n<\/ul>\r\n<\/div>\r\n\r\n<table>\r\n<tbody>\r\n<tr>\r\n<td><strong>you can view video on Evidences of Evolution<\/strong><\/td>\r\n<td><a href=\"https:\/\/youtu.be\/3rsSkWlaMUg\" target=\"_blank\" rel=\"noopener\"><img class=\"alignnone wp-image-120\" src=\"http:\/\/epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/2018\/11\/download.png\" alt=\"\" width=\"36\" height=\"36\" \/><\/a><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n\r\n<strong>References &amp; Further Reading<\/strong>\r\n<ul>\r\n \t<li>The Beak of the Finch <em>by Jonathon Weiner,<\/em> <strong><em>Vintage Books<\/em><\/strong><em>: 1995<\/em><\/li>\r\n \t<li>Darwin's Dream Pond <em>by Tijs Goldschmidts,<\/em> <strong><em>MIT Press<\/em><\/strong><em>: 1997<\/em><\/li>\r\n \t<li>How and Why Species Multiply <em>by Peter &amp; Rosemary Grant,<\/em> <strong><em>Princeton<\/em><\/strong><em>: 2008<\/em><\/li>\r\n \t<li>The Making of the Fittest <em>by Sean B. Carroll,<\/em> <strong><em>Quercus<\/em><\/strong><em>: 2008<\/em><\/li>\r\n \t<li>Why Evolution is True <em>by Jerry Coyne,<\/em> <strong><em>OUP<\/em><\/strong><em>: 2009<\/em><\/li>\r\n \t<li>The Future of Life by <em>Edward O. Wilson, Abacus: 2002<\/em><\/li>\r\n<\/ul>","rendered":"<div><span style=\"float: right;\"><a href=\"https:\/\/youtu.be\/3rsSkWlaMUg\" target=\"_blank\" rel=\"noopener\"><img decoding=\"async\" src=\"http:\/\/epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/2018\/11\/download.png\" alt=\"epgp books\" width=\"75px\" height=\"75px;\" \/><\/a><br \/>\n<\/span><\/div>\n<div>\n<p>&nbsp;<\/p>\n<p><strong>Contents:<\/strong><\/p>\n<ul>\n<li>Introduction<\/li>\n<li>The concept of Evolution<\/li>\n<li>How Do We Know That Evolution Has Occurred?: Evidences of evolution<\/li>\n<li>Case studies for evolution<\/li>\n<li><strong style=\"text-align: initial;font-size: 1em\">Summary<\/strong><\/li>\n<\/ul>\n<\/div>\n<p>&nbsp;<\/p>\n<p><strong style=\"text-align: initial;font-size: 1em\">INTRODUCTION<\/strong><\/p>\n<div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The Nobel Prize winning scientist Linus Pauling aptly described science as the search for truth. Science does this by continuously comparing its theories objectively with evidence in the natural world. When theories no longer conform to the evidence, they are modified or rejected in favor of new theories that do conform. In other words, science constantly tries to prove its assumptions to be false and rejects implausible explanations. In this way, scientific knowledge and understanding grow over time.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>EVOLUTION: THE CONCEPT<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Evolution is change in heritable traits of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organisation, including the level of species, individual organisms, and at the level of molecular eviolution.<\/p>\n<p>&nbsp;<\/p>\n<p>There are different theories of evolution<\/p>\n<p>&nbsp;<\/p>\n<p>Lamarckism<\/p>\n<p>&nbsp;<\/p>\n<p>Darwinism<\/p>\n<p>&nbsp;<\/p>\n<p>Pangenesis theory<\/p>\n<p>&nbsp;<\/p>\n<p>Synthetic theory of evolution<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The synthetic theory synthesized various concepts such as Darwin\u2019s natural selection, Mendelian genetics, mutation theory and population genetics to understand the course and mechanism of evolution.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>How Do We Know That Evolution Has Occurred?<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>The evidence for evolution has primarily come from four sources:<\/p>\n<p>&nbsp;<\/p>\n<p>1.\u00a0\u00a0\u00a0\u00a0\u00a0 fossil record of change in earlier species<\/p>\n<p>2.\u00a0\u00a0\u00a0\u00a0\u00a0 chemical and anatomical similarities of related life forms<\/p>\n<p>3.\u00a0\u00a0\u00a0\u00a0\u00a0 geographical distribution of related species<\/p>\n<p>4.\u00a0\u00a0\u00a0\u00a0\u00a0 recorded genetic changes in living organisms over many generations<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Fossil Record<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"text-align: justify;font-size: 1em\">Remains of animals and plants found in <\/span><span style=\"text-align: justify;font-size: 1em\">sedimentary <\/span><span style=\"text-align: justify;font-size: 1em\">rock deposits give us an indisputable record of past changes through vast periods of time. This evidence attests to the fact that there has been a tremendous variety of living things. Some extinct species had traits that were transitional between major groups of organisms. Their existence confirms that species are not fixed but can evolve into other species over time.<\/span><\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The evidence also shows that what have appeared to be gaps in the fossil record are due to incomplete data collection. The more that we learn about the evolution of specific species lines, the more that these so-called gaps or &#8220;missing links in the chain of evolution&#8221; are filled with transitional fossil specimens. One of the first of these gaps to be filled was between small bipedal dinosaurs and birds.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-374\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-180.png\" alt=\"\" width=\"207\" height=\"234\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-180.png 207w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-180-65x73.png 65w\" sizes=\"auto, (max-width: 207px) 100vw, 207px\" \/><\/p>\n<p style=\"text-align: justify\">Just two years after Darwin published <em>On the Origin of Species<\/em>, a 150-145 million year old fossil of <em>Archaeopteryx<\/em> was found in southern Germany. It had jaws with teeth and a long bony tail like dinosaurs, broad wings and feathers like birds, and skeletal features of both. This discovery verified the assumption that\u00a0 birds\u00a0 had\u00a0 reptilian ancestors.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-375\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-181.png\" alt=\"\" width=\"580\" height=\"168\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-181.png 580w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-181-300x87.png 300w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-181-65x19.png 65w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-181-225x65.png 225w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-181-350x101.png 350w\" sizes=\"auto, (max-width: 580px) 100vw, 580px\" \/><\/p>\n<div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Since the discovery of <em>Archaeopteryx<\/em>, there have been many other crucial evolutionary gaps filled in the fossil record. Perhaps, the most important one, from our human perspective, was that between apes and <em>Homo sapiens<\/em>. Since the 1920&#8217;s, there have been literally hundreds of well-dated intermediate fossils found in Africa that were transitional species leading from apes to humans over the last 6-7 million years.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The fossil record also provides abundant evidence that the complex animals and plants of today were preceded by earlier simple ones. In addition, it shows that multicelled organisms evolved only after the first single-celled ones. This fits the predictions of evolutionary theory.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">Living things on earth are fundamentally similar in the way that their basic anatomical structures develop. No matter whether they are simple single-celled protozoa or highly complex organisms with billions of cells, they all begin as single cells that reproduce themselves by similar division processes. After a limited life span, they also all grow old and die.<\/span><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\"><span style=\"font-size: 1em\">All living things on earth share the ability to create complex molecules out of carbon and a few other elements. In fact, 99% of the proteins, carbohydrates, fats, and other molecules of living things are made from only 6 of the 92 most common elements. This is not a mere coincidence.<\/span><\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">All plants and animals receive their specific characteristics from their parents by inheriting particular combinations of genes. Molecular biologists have discovered that genes are, in fact, segments of <a href=\"http:\/\/anthro.palomar.edu\/evolve\/glossary.htm#DNA\">DNA <\/a>molecules in our cells.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-376\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-182.png\" alt=\"\" width=\"210\" height=\"134\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-182.png 210w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-182-65x41.png 65w\" sizes=\"auto, (max-width: 210px) 100vw, 210px\" \/><\/p>\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">These segments of DNA contain chemically coded recipes for creating proteins by linking together particular <\/span><span style=\"text-align: initial;font-size: 1em\">amino acids <\/span><span style=\"text-align: initial;font-size: 1em\">in specific sequences.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-377\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-183.png\" alt=\"\" width=\"171\" height=\"241\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-183.png 171w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-183-65x92.png 65w\" sizes=\"auto, (max-width: 171px) 100vw, 171px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">All of the tens of thousands of types of proteins in living things are mostly made of only 20 kinds of amino acids. Despite the great diversity of life on our planet, the simple language of the DNA code is the same for all living things. This is evidence of the fundamental molecular unity of life.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">In addition to molecular similarities, most living things are alike in that they either get the energy needed for growth,repair, and reproduction directly from sunlight, by photosynthesis , or they get it indirectly by consuming green plants and other organisms that eat plants.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">All of these major chemical and anatomical similarities between living things can be most logically accounted for by assuming that they either share a common ancestry or they came into existence as a result of similar natural processes.<\/p>\n<p>&nbsp;<\/p>\n<p><strong style=\"text-align: initial;font-size: 1em\">Geographical Distribution of the Related Species<\/strong><\/p>\n<div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The geographic distribution of related species is another example for the past evolution. This is also niw clear that many of the major isolated lands and group of islands hve evolved their distinctive plants and animals communities. For example, in Australia, before humans arrived their before 60-40,000 years ago, had no advanced terrestrial placental mammals like cats, dogs, bears, horses rather had more than 100 species of kangaroos, koalas, and other marsupials. It is also reported that the terrestrial mammals were entirely absent from the even more isolated islands that make up Hawaii and New Zealand. All of these had a larger number of plant, insect, and bird species that were found nowhere else in the world. This can be explained through evolution in isolation of Australia\u2019s, New Zealand\u2019s and Hawaii\u2019s biotic environment from the rest of the world for million of years<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Genetic Changes over Generations<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The environment of earth is continuously changing, usually in subtle and complex ways. The changes when go beyond a threshold when it is beyond the toleration of a population of organisms mass deaths occur. This also goes with the observation of Chales Darwin that not all the organisms would peish after this. Fortunately, natural populations have genetic diversity. Only the organisms whose internal characteristics allow them to survive an environmental crisis are likely the only ones able to reproduce.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Lately these traits will be more common in the next generation&#8211;evolution of the population will have occurred.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The process of this selection (natural) resulting in evolution can be demonstrated over a 24 hour period in a laboratory Petri dish of bacteria living in a nutrient medium. Whenever higher or lethal dose of antibiotic is added, majority of the bacteria will die-off. While majority of these die only few of the bacteria usually are immune and survive. The next generation is mostly immune because they have inherited immunity from those who have survived. The purple bacteria in the Petri dishes shown below in the figure showing that the bacterial population has evolved.<\/p>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-378\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-184.png\" alt=\"\" width=\"322\" height=\"172\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-184.png 322w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-184-300x160.png 300w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-184-65x35.png 65w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-184-225x120.png 225w\" sizes=\"auto, (max-width: 322px) 100vw, 322px\" \/><\/p>\n<p style=\"text-align: justify\">Similar phenomenon is observed in human bodies as well where the body reacts when an antibiotic drug is administered and its unable to completely eliminate a bacterial infection. Due to this the medical doctors recommend the antibiotic to be taken even after the disease doe not persists as a course. They do not want to allow any potentially antibiotic resistant bacteria to survive.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-379\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-185.png\" alt=\"\" width=\"157\" height=\"167\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-185.png 157w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-185-65x69.png 65w\" sizes=\"auto, (max-width: 157px) 100vw, 157px\" \/><\/p>\n<p style=\"text-align: justify\">Selective breeding has paved way for the development of new species of planyts and animals. The process is similar to the bacterial experiment discussed above. The organisms are selected on the basis of the traits required for the development of particular breed. All those individuals who lack the desirable characteristics are not allowed to breed. Therefore, the following generations more commonly have the desired traits.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">Similar phenomenon is observed in human bodies as well where the body reacts when an antibiotic drug is administered and its unable to completely eliminate a bacterial infection. Due to this the medical doctors recommend the antibiotic to be taken even after the disease doe not persists as a course. They do not want to allow any potentially antibiotic resistant bacteria to survive.<\/span><\/p>\n<div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Selective breeding has paved way for the development of new species of planyts and animals. The process is similar to the bacterial experiment discussed above. The organisms are selected on the basis of the traits required for the development of particular breed. All those individuals who lack the desirable characteristics are not allowed to breed. Therefore, the following generations more commonly have the desired traits.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Species that mature and reproduce large numbers in a short amount of time have a potential for very fast evolutionary changes. Insects and microorganisms<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">often evolve at such rapid rates that our actions to combat them quickly lose their effectiveness. We must constantly develop new pesticides, antibiotics, and other measures in an ever escalating biological arms race with these creatures. Unfortunately, there are a few kinds of insects and microbes that are now significantly or completely resistant to our counter measures, and some of these species are responsible for devastating crop losses and deadly diseases.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">If evolution has occurred, there should be many anatomical similarities among varieties and species that have diverged from a common ancestor. Those species with the most recent common ancestor should share the most traits. For instance, the many anatomical similarities of wolves, dogs, and other members of the genus <em>Canis<\/em> are due to the fact that they are descended from the same ancient canine species and still share 99.8% of their genes. Wolves and dogs also share similarities with foxes, indicating a slightly more distant ancestor with them.<\/p>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-380\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-186.png\" alt=\"\" width=\"153\" height=\"137\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-186.png 153w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-186-65x58.png 65w\" sizes=\"auto, (max-width: 153px) 100vw, 153px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-381\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-187.png\" alt=\"\" width=\"445\" height=\"192\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-187.png 445w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-187-300x129.png 300w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-187-65x28.png 65w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-187-225x97.png 225w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-187-350x151.png 350w\" sizes=\"auto, (max-width: 445px) 100vw, 445px\" \/><\/p>\n<div>\n<p style=\"text-align: justify\">Evolution can be a very slow process. But actually we now have numerous examples where long term studies of populations document evolution happening within decades. Through meticulous measurement and attention to detail we can watch evolution in action. Evolution within populations is called microevolution and the changes are often small, but adding up these small differences through time is how evolution works.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Case study 1: Darwin\u2019s Finches<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">One of the best studied examples of evolution in action comes from work done by Prof. Peter Grant and his wife Dr. Rosemary Grant on the beak size of Galapagos finches (aka Darwin\u2019s finches).<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">These birds live on the Galapagos Islands, off the coast of Ecuador, right on the equator. For almost 40 years researchers have been living on these islands and taking detailed measurements of the birds. They focus on a few islands in particular, one is called Daphne. Daphne is small enough to be able to count all the birds on the island, and catch them often enough to keep track of their growth and size.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Survival isn\u2019t easy on these islands; it\u2019s baking hot during the day, freezing cold at night and there isn\u2019t much food. Because of this, the birds have very specialised feeding behaviours. We see them now as 13 species all feeding on different things in different ways. But all these 13 species evolved from one common ancestor. Originally a South American finch colonised the island and became distinct from the mainland population (peripartic speciation). Different sub-populations of the birds also began to occupy new habitats and specialise on different ways of feeding. Selection kept these groups apart because hybrids were less fit (parapatric and sympatric speciation).<\/p>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-382\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-188.png\" alt=\"\" width=\"298\" height=\"288\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-188.png 298w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-188-65x63.png 65w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-188-225x217.png 225w\" sizes=\"auto, (max-width: 298px) 100vw, 298px\" \/><\/p>\n<div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Each ground finch species has evolved a beak adapted to target different categories of seeds. The small ground finch has a small beak (3-4mm deep) and eats mostly small seeds, the medium ground finch has a medium sized beak (5mm deep) and eats moderately sized seeds and the large ground finch targets larger seeds that the others can\u2019t crack open; it has a heavy duty beak (8mm deep) to allow it to do so.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The weather affects the abundance of seeds on the island. When it&#8217;s very hot and dry few seeds are produced and competition for food increases amongst the finches. The Grant\u2019s research team were on the island during one dry spell that lasted much longer than usual. The island became very dry, vegetation died back and plants stopped producing seeds. They watched and recorded measurements about the seeds and beak sizes as the birds ate their way through the last of the easily eaten nuts and many starved and died. After many months without rain only the biggest, toughest and most spine covered seeds were left.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The researchers found that the lack of food had increased competition among the birds. The smaller beaked birds fared worst and amongst the large ground finch there was very strong selection for larger beaks, because the individuals with the largest beaks were the only ones able to eat. In fact, compared to the average depth of beak at the start of this dry period, by the end of it the average beak depth was 1mm bigger.<\/p>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-383\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-189.png\" alt=\"\" width=\"263\" height=\"196\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-189.png 263w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-189-65x48.png 65w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-189-225x168.png 225w\" sizes=\"auto, (max-width: 263px) 100vw, 263px\" \/><\/p>\n<div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Another example comes from Prof. David Reznick\u2019s work on guppies which live in rivers in a Caribbean Island called Trinidad. The guppies either live with or without the presence of a predator fish, a pike-like thing. So some populations grow up having to avoid being eaten, others don\u2019t. The presence of the predator changes the selective pressure acting on the guppies, so they have evolved different traits.<\/p>\n<p>&nbsp;<\/p>\n<p>The ones living with predators grow up faster, mature at smaller sizes and reproduce earlier; they need to breed as soon as possible because they could get eaten any time. In rivers without predators the guppies can grow up at a more leisurely pace and put more energy into their offspring.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Prof. Reznick\u2019s team have done a series of experiments where they took fish from each population and put them into rivers which previously did not contain guppies. Some of these new rivers had predators in them, others didn\u2019t. The experiment was set up so populations from rivers with predators were moved to rivers without predators and vice versa. As a control they also moved populations from rivers with predators to different rivers with predators, and the same for populations from rivers lacking predators.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The team left their fish in their new homes and came back after just ten years. Their prediction was that evolution should be replicated: the fish would evolve larger body sizes and delayed maturation in rivers without predators, and evolve smaller body sizes and earlier maturation in rivers with predators. Sure enough that\u2019s exactly what they found! This proved the natural populations were adapted to maximise their reproductive output by adopting different strategies depending on their circumstances.<\/p>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-384\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-190.png\" alt=\"\" width=\"310\" height=\"239\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-190.png 310w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-190-300x231.png 300w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-190-65x50.png 65w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-190-225x173.png 225w\" sizes=\"auto, (max-width: 310px) 100vw, 310px\" \/><\/p>\n<div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Another fish example is armor plating in sticklebacks. Since the last ice age, three-spined sticklebacks have been very successful, spreading from marine populations up into rivers and lakes across the world. As they have spread, sticklebacks have evolved a number of adaptations to help them evade predators.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Some populations have large pelvic spines, which make them harder to swallow so protect them against big predator fish. Some populations lack the spines, these fish usually swim quite close to the bottom of the water bed, within reach of crustacean predators which can use their claws to reach up and grab the pelvic spines of the sticklebacks. For these populations, lacking the pelvic spines helps them to avoid a different sort of predator. Researchers have even been able to pinpoint the gene involved in pelvic reduction, it&#8217;s called <em>Pitx1<\/em> and seems to be involved in multiple, independent evolutionary events when spines have been lost.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Another defensive trait is armor plating. Sticklebacks which live in marine environments have a series of bony plates along either side of their body. These make it difficult for predators to eat the fish once they\u2019ve caught it, so often the stickleback will get away. The problem with armour plating is that it slows the fish down, but since in marine environments water tends to be quite clear it\u2019s unlikely the stickleback could escape it\u2019s predator by swimming away.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">In freshwater environments however the water can be a lot murkier and there could be selective pressure to bolt quickly when attacked so as to disappear into the murk. This would require the armour plates to be lost. In fresh water sticklebacks around the world this is what is seen. The number of plates is reduced, and sticklebacks go for a quick escape strategy of defence. Scientists have also pinpointed\u00a0<span style=\"text-align: initial;font-size: 1em\">the gene involved in this phenotypic change, its called <\/span><em style=\"text-align: initial;font-size: 1em\">ectodysplasin<\/em><span style=\"text-align: initial;font-size: 1em\">, and, like <\/span><em style=\"text-align: initial;font-size: 1em\">Pitx1<\/em><span style=\"text-align: initial;font-size: 1em\">, it&#8217;s responsible for similar changes in multiple independent cases.<\/span><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">The whole idea of natural selection rests on the gradual adaptation of organisms to their environment. If the environment changes, some individuals will have characteristics that make them better able to cope than others, and these individuals will be more likely to pass on their genes to future generations.<\/span><\/p>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-385\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-191.png\" alt=\"\" width=\"332\" height=\"239\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-191.png 332w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-191-300x216.png 300w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-191-65x47.png 65w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-191-225x162.png 225w\" sizes=\"auto, (max-width: 332px) 100vw, 332px\" \/><\/p>\n<div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The environment is changing. It is now widely accepted that carbon dioxide levels are rising and that this is causing temperatures to increase via the greenhouse effect. Global warming is a reality, and it will have major effects on many aspects of our environment, including&#8230;<\/p>\n<p>&nbsp;<\/p>\n<ul>\n<li>Temperature rises of between 2 and 12 \u00b0C by 2100<\/li>\n<li>Changes to rainfall and humidity levels<\/li>\n<li>The destruction of habitats due to flooding, droughts or extreme weather, plus secondary events like forest fires<\/li>\n<li>Changing disease patterns<\/li>\n<li>Ocean acidification (decreased pH of seawater due to the formation of carbonic acid when carbon dioxide dissolves in water)<\/li>\n<li>Changes in ocean currents and sea levels<\/li>\n<\/ul>\n<\/div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">These changes will and are already affecting life on earth. We are already witnessing changes to the genomes of organisms resulting in shifts in metabolic rate, breeding season, migration patterns, disease dynamics and food availability. All of these changes will upset the delicate balance of ecosystems.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Recent studies suggest the possibility of mass extinctions as a result of these changes \u2013 this is because rapid changes in the environment are likely to be challenging for organisms as they have adapted over thousands of years to suit particular niches (roles within the community). Some may be suited to the new environment but others will be forced to evolve in new ways to survive in the new environment. As a result there is a possibility that the rate of evolution may rise as selection pressure increases, and as a result large changes to biodiversity may result.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-386\" src=\"http:\/\/antp08.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/189\/2019\/03\/2-192.png\" alt=\"\" width=\"320\" height=\"216\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-192.png 320w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-192-300x203.png 300w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-192-65x44.png 65w, https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-content\/uploads\/sites\/189\/2019\/03\/2-192-225x152.png 225w\" sizes=\"auto, (max-width: 320px) 100vw, 320px\" \/><\/p>\n<div>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">The changing climate is already resulting in earlier springs, longer summers and milder winters. It is this, rather than direct temperature change, which many organisms are battling against.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">During the past forty years, scientists have observed species migrating, reproducing and developing earlier. A good example of this is the European great tit. European great tits are evolving different breeding times to ensure maximum food supplies to increase offspring survival. This is because Winter Moth caterpillars are maturing earlier in spring due to rising temperatures and these caterpillars are a staple food source for these birds. So individuals which can bring forward their egg-laying ensure greater food availability for their chicks and so these individuals are more successful. Research has shown that birds lay their eggs two weeks earlier than they did in the 1970s, a clear example of how organisms are altering in response to global warming. Similarly, Canadian red squirrels are breeding earlier allowing them to gather more pinecones to tide them over during winter.<\/p>\n<\/div>\n<div>\n<p style=\"text-align: justify\">Another example is the mosquito <em>Wyeomyia smithii<\/em>. In response to changes to length of day insects are developing later and gradually the genomes of northern individuals are coming to resemble more closely those of insects living near the equator.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">In fact, several species depend on day length to tell them when to migrate, mate or go into hibernation. Other cues such as daily length of warmth (thermo period), rainfall and food availability are also crucial in allowing organisms to decide when to perform these tasks. Global warming is affecting all these cues except for day length.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Summary<\/strong><\/p>\n<ul>\n<li style=\"text-align: justify\">Evolution is change in heritable traits of biological populations over successive generations.<\/li>\n<li style=\"text-align: justify\">Evolutionary processes give rise to diversity at every level of biological organisation, including the level of species, individual organisms, and at the level of molecular evolution<\/li>\n<li>There are different theories of evolution<\/li>\n<li style=\"text-align: justify\">The evidence for evolution has primarily come from four sources: fossil record, chemical and anatomical similarities, geographical distribution and recorded genetic changes.<\/li>\n<li style=\"text-align: justify\">Evolution within populations is called microevolution and the changes are often small, but adding up these small differences through time is how evolution works.<\/li>\n<li>There is a tendency in all organisms to increase in geometric ratio.<\/li>\n<li style=\"text-align: justify\">Biological variations with regard to structural, physiological and behavioural traits occur among the individuals.<\/li>\n<li style=\"text-align: justify\">Those who have selective advantage tend to survive.<\/li>\n<li style=\"text-align: justify\">They reproduce more number of offspring than those who are less adaptive.<\/li>\n<li style=\"text-align: justify\">The accumulation of advantageous traits in future generations gradually bring changes in the species and eventually a new species may be evolved<\/li>\n<\/ul>\n<\/div>\n<table>\n<tbody>\n<tr>\n<td><strong>you can view video on Evidences of Evolution<\/strong><\/td>\n<td><a href=\"https:\/\/youtu.be\/3rsSkWlaMUg\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-120\" src=\"http:\/\/epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/2018\/11\/download.png\" alt=\"\" width=\"36\" height=\"36\" \/><\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>References &amp; Further Reading<\/strong><\/p>\n<ul>\n<li>The Beak of the Finch <em>by Jonathon Weiner,<\/em> <strong><em>Vintage Books<\/em><\/strong><em>: 1995<\/em><\/li>\n<li>Darwin&#8217;s Dream Pond <em>by Tijs Goldschmidts,<\/em> <strong><em>MIT Press<\/em><\/strong><em>: 1997<\/em><\/li>\n<li>How and Why Species Multiply <em>by Peter &amp; Rosemary Grant,<\/em> <strong><em>Princeton<\/em><\/strong><em>: 2008<\/em><\/li>\n<li>The Making of the Fittest <em>by Sean B. Carroll,<\/em> <strong><em>Quercus<\/em><\/strong><em>: 2008<\/em><\/li>\n<li>Why Evolution is True <em>by Jerry Coyne,<\/em> <strong><em>OUP<\/em><\/strong><em>: 2009<\/em><\/li>\n<li>The Future of Life by <em>Edward O. Wilson, Abacus: 2002<\/em><\/li>\n<\/ul>\n","protected":false},"author":3,"menu_order":31,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["dr-subhendu-k-acharya"],"pb_section_license":""},"chapter-type":[],"contributor":[64],"license":[],"class_list":["post-371","chapter","type-chapter","status-publish","hentry","contributor-dr-subhendu-k-acharya"],"part":3,"_links":{"self":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/pressbooks\/v2\/chapters\/371","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/wp\/v2\/users\/3"}],"version-history":[{"count":7,"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/pressbooks\/v2\/chapters\/371\/revisions"}],"predecessor-version":[{"id":484,"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/pressbooks\/v2\/chapters\/371\/revisions\/484"}],"part":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/pressbooks\/v2\/chapters\/371\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/wp\/v2\/media?parent=371"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/pressbooks\/v2\/chapter-type?post=371"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/wp\/v2\/contributor?post=371"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/antp08\/wp-json\/wp\/v2\/license?post=371"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}