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UNIT, , 6, , Evolution, , CHAPTER, E h has iis own tree of ancestors. but at the fop, , Chapter Outline, 6.1 Origin of life- Evolution of lfe forms, 6.2, , Geological time scale, , 6.3, , Biological evolution, , 6.4, , Evidences for biologkcal evolution, , 6.5 Theories of biological evolution, 6.6, , Mechanism of evolution, , 6:7, , Hardy Weinberg principle, , 6.8, , Origin and evolution of man, , The term evolution is used to describe, heritable ofchanges in one, or more, ot, trom, , aracteristics, , a, , population, , species, , one generation to the otherne present state, , mankind on earth 1s thebutcome ot three, kinds of evolution chemical. organic and, ot, , social or cultural evolution., , Radiometric dating of meteorites yields, an estimated age tor the solar system and tor, , earth around 4.5 4.6 billion years. The, as, , eW Do, , -, , cartn remalned inhospitable, , for, , at, , least, , Learning, , Objectives, , Understands the evolutiom of bfe on earth, , Gains knowiedge on theories of evolution., nterprets evidences (anatomical., embryological and, , first, tew, hundred, millions, years., At, it, was too hot. This is because the collisions of, , the planetesimals that coalesced to form earth, released much heat to melt the entire planet., , Eventually outer surface, , of the earth cooled, , and solidified to form, , crust. Water, , a, , and condensed to form, , a ) of evolution., , vapour, , released from the planets interior cooled, oceans., , Hence origin, , Learns the principles of, , of life can be reconstructed using indirect, evidences. Consequently. biologists have, , biological evolution., , turned to gather disparate bits ot intormation, , Understarnds the, , GUPPG, LGDPPG, , tmportance of gene jrequecies in a, , population., Studies the geological time scale., , and, , ike, of jig, puzzle. Many theories have been proposed, , tiling them together, , pieces, , saw, , to explain the origin of life. Few have been, discussed in this chapter.

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6.1, , physical forces such, lightning. UV radiations,, as, , Origin of life Evolution of, -, , vocanic, , lite forms, , activities,, , Oparin, , etc., , (1924), , su88esied hat the organic compounds could, , that, creation, of, speclal, Theory, states, |ife, , was, , created by supernatural power,, a, , respecttully reterred to as "God. According, , Hindulsm, Lord Brahma, Christianity. Inlam and most religions beleve, that God created the universe, the plants and, , created the Earth., , to, , the animals.), , NAccordhg to the theory of spontaneous, tanisms, or AboB, , Qgenèration, , erials, , materials and, , Ortginated rom non-living, , and, occurredthrough, stepwise, chemical, evolutlon, over, milllons, of, molecular, years., , Thomas Huzley colned the term ablogenesis. ), B4g bang theory explalns the orgin, , of, in, , as a, universe terms., singular, , huge, , exploslon, , earth, no proper atmosphere, but consisted of, , phyalcal, , ammonla,, , The primitive, , methane,, , hydrogen, , had, , and, , water, , pour. The temperature of the earth, , was, , li, , extremely high. UV rays from the sun split, , up water molecules Into hydrogen and, oxygen. Gradually the temperature cooled, and the, , water vapour condensed to lorm raln., , Raln water filled all the, , to, , depressions torm, , Water bodles. Ammonia and methane in the, with, to, atmosphere, , combined, oxygen torm, carbon-dioxlde and other gases. ) ,, Coacervates (large colloidel partcles, that precipltate out In aqueoue medium), are the finst pre-cells whlch, , transformed Into lving oella, , gradualy, , ite arose from pre-existing life. The term, , process, , refers, , to the, , blochemical, , production of living organlsms, , This term was colned by Henry Bastlan., , According, evolution, , to the, , primitlve, , EVOID, , theory, , a, undergone, serics o reactionskading, to more complex molecules He proposed that, , the molecules formed colloidal aggregates or, , coacervates' in an aqueous environment., coacervates were able to absorb and assimilate, , The, , trom the environment., organc compounds, Haldane (1929) proposed, that the primordial, , sea served, , s, , a, , vast, , of chemical, , organisms, , In, , the, , chemical, , powered by solar energy, , laboralory, , The atmosphere, , was oxygen free and the combination ot CO, , NH,, , and, , compounds., , 8ave rse to organic, radiations, sea became a hot dilute, , The, , soup containing large populations of organic, monomers and polymers They envisaged that, groups of monomers and polymers acqulred, , iptd, membranes and further developed into, a mem, , the first living cell. Haldane coined the term, prebiotle soup and this became the powerful, , symbol, , of the, , Oparin-Haldane, , view, , t, , on, , origin of life (1924-1929)., , Oparin, , and, , Haldane, , independently, , suggested that if the primitlve atmosphere was, reducing and if there was appropriate supply, or energy such as lightning or UV light then, , wae range o 9rganic compounds, , be, , can, , synthesized. ) 5Y, , 6.2 Geological time scale, , The duration of the earths history has been, divided Into eras that include, t h e Paleozole, Mesozoic,, d, , According to the theory of blogenesis, , blogenesisof also, , have, , enozoic. Recent, , eras, , Into, , urther divided, A | periods, which are pn nto, LHDCIQG epochs. The geologcal tume, aare, , scale with the duration of the, eras and perlods with the dominant forms of, life is shown in Table 6.1., The Paleozoic, , era, , ts characterlzed, , by, , abundance of lossils of marlne invertebrates., , primordial environment of the carth evolved, , Towards the later halt, other vertebrates (marine, , spontaneously Irom inorganic substances and, , and terrestrial) except birds and mammals

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Jurassic (Dinosaurs were dominant on the, carth, fossil bird, , Archaeopterya) and, , Cretaceous (extinction of toothed birds and, , nosaurs, emergence of modern birds)., , enozoic, , era, , (Age, , into, , two, , mammals), , of, , Two major cell types that, time were, of the, earliest cell contained cumps of nucleoproteins, embedded in the cell substance. Such cells were, similar to the Monera. They are considered as, viruses., , Ppeared, signihcant.Oneform, , during this, , Tertiary and Quaternary. Tertiary period is, , ancestral to the modern bacteria and blue green, algae. The other form of earliest cells contalned, , characterized by abundant mammalilan fauna., , central mass surrounded bya thin membrane., , is, , subdivided, , period, , This, , is, , subdivided, , periods namely, into five, , epochs, , nucieoprotein, , clumps, , that, , condensed into, , a, , mammals,, , his, membrane separaled nuceoproteins from, the cell substances., , Eocene (Monotremes except duck billed, , to as Protista. When the natural sources ot, , namely., , Platypus, , Paleocene, , placental, , and Echidna, hooted mammals and, , carnivores),, Oligocene (thigher placental, mammals appeared), Miocene (origin ot, tirst man like apes) and Pliocene (origin of, man, , from, , man, , like, , apes).Quaternary period, , witnessed decline of mammals and beginning, , ohuman social life., , The age of fossils can be determined, sing two methods, , and absolute dating., , namely,, , relative, , dating, , Such, , food in the, , saprophytism, predator, , there was an increase in the tree O, in the sea, , CH+20, Co, +2H,0, 4NH,+30,- 2N,+6H,0, , dating is used to determine the precise age, , nitrogen., , atmospheric, oxygen combined with, ammonia, CO;, and, , The, , to torm, , presence of, , the, , and fre, , free 0, brought, , about the evolution of aerobic, , isotopes., , and, , and atmosphere., , The, , decay of, , or animalism, , chemosynthesis, photosynthesis. When the, number of photosynthetic organisms increased, , methane, , the, , of time, , or, , Absolute, , measure, , declined in course, , evove diferent methods for food procurement., These may be summarized as parasitism,, , used to, it to similar, , of a fossil by using radiometric dating to, , were reeTed, , the ancestors of Monera and Protista had to, , Relative dating is, , determine, a tossil by comparing, rocks and fossils of known age, , ocean, , cells, , respiration, , which could yield large amounts of energy, by oxidation of food stuffs. Thus Prokaryotes, and Eukaryotes evolved., , 6.3 Biological evolution, , Formation of protobionts, Abiotically, , produced molecules canExperimental approath to the origin, , spontaneously self assemble into droplets, that enclose a watery solution, and, a chemical environment different from, surroundings. Scientists call these spheres, , of life, , maintain/, their C ., , nderstanding the posible, , paved way, synthesis of, , as 'protobionts) Liposomes are lipids in a, , organic conpounds that led to the aPpearance, , olution that can sel assemble into a lipid, , of living organisms is depicted in the Fig 6.1., , Dilayer., , Some, , of the proteins, , acquired the p, , inside, , he, , ofs nzy, , posoe", resuing n fast multiplication of molecules.), e, , with, coacervates, nudeoprotein that, and, had, nutrients, limiting, surface, membrane, had the characters of a virus or free living genes., a, , Sub sequently number of genes united to form, proto viruses somewhat similar to present day, , Evolutlon, , Urey and Miller (1953),, , their experiment, a mixture of gases was, Aallowed to circulate over electric discharge, , In, from an tungsten electrode. Asmall flask was, , and the, from, boiling, steam, emanating, it was made to mix with the mixture of gases, , kept, , (ammonia, methane and hydrogen) n the large*, connected to the boling, water. The steam condensed to form waler, , chamber that, , was

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theory, , that, , of, , recapitulation", , history, , the ife, , of, , which, an, , states, , individual, , togeny) brielly repeats or recapitulates the, lutionary history of the race (phylogeny)., words, , In other, yol ac, , emb os, The, , appearance, , are some of the, , exampies g, , 09, , ogenetic law is not universai and t s, , Theories of biological, evolution, , 6.5.1 Lamarck's theory, , "Ontogeny recapitulates, , The embryonic stages, a, Pogeny, of, hieer animal resemble the adult stage of its, of pharyngeal gill slits,, and tors. Appearance, the, of tail in human, , and, , 6.5, , Jean Baptiste de Lamarck, was the hrst to, , postulate the theory of evolution in, book, , his famous, , in the year, of Lamarcklan theory, , "Philosophie Zoologigue, , 1809. The two, , principles, , are, . The theory of use and disusethat are used often will increase in size ana, , gans, , now pught that animals do not recapitulate, , those that are not used will degenerate. Neck in, , the adtstage of any ancestors. The human, , girafe is an example of use and absence of limbs, , embry recapitulates the embryonic history, and note adult history of the organisms., , in snakes is an example for disuse 1heory., , . The theory of inheritance of acquired, The, , pmparative study, , of the, , embryo o, , different imals shows structural similarities, among thmselves. The embryos of fish,, , salamande tortoise, chick and human start, life as a, and undergo, sine cell, the zYgote,, blastula,, , characters Characters that are developed, , during the, , life time of, , organism are called, acquired characters and these are then inherited, an, , The main objection to Lamarckismn, , to, , Lamarck's"Theory of Acquired characters", , This indicates, , was disproved by August Weismann who, , that all the ove said animals have evolved, , conducted experiments on mice tor twenty, , trom a commancestor., , generations by cutting their tails and breedling, , change, , to, , roduce the, gastrua anare triploblastic., Cieavage, , them. All mice born were with tail. Weismann, , Molecular dences, Molecular cvolution, , s, , the, , process, , ot change i n e sequence composition ot, , molecules, , such DNA, , across generati, , t, , RNA and, , proteins, , uses principles, , proved his germplasm theory that change in the, somatoplasm will not be transterred to the next, generation but changes in the germplasm will, be inherie, , of, , evolutlonary bioy and population genetics, to explain paterns the changes of molecules., in the, One of the, seful, advancement, of, lar, is, and, mo, , Neo-Lamarckism, ne, , Tolowers, , (Neo-Lamarckists) ike, tried to, , o, , amarck, , Cope, Osborn, Packard, , explain Lamarck's, , theory, , development, , mole, other molecules that, , blology proteins, ontrol lite processes are, , andSpencer, , conserved among sp, , es. A slight change that, , adaptations are unlversal.(Organisms acqulre, , occurs over time in the conserved molecules, , new structures due to their adaptat ions to, , (DNA, RNA and pr in) are often called, , the changed environmental conditions. They, , molecular docks. Molectúles that have been used, , argucd, , study evolution are cytochrome (respiratory, pathway) and rRNA (protein synthesis)., to, , c, , on a more scientihc basis. They considered that, , that external conditions stimulate the, , somatic cels to produce certain secretions', the sex cells, the, and, which, reach, through, blood, bring about variations, in he, , oprng8), , \

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theory of recapitulation" which, that, , the, , life, , history, , of, , an, , states, , individual, , (ogeny) briefly repeats or recapltulates the, , lutionary history of the race phylogeny., , Inlother words Ontogeny recapitulates, a, The, hier animal resemble the adult stage of lts, , P ogeny, , embryonic stages of, , 6.5 Theories of biological, , evolution, 6.5.1 Lamarck's theory, , Jean Baptiste de lamarck, was the first to, , postulate the theory of evolution in his famous, , book "PhilosopBhie Zoologigue in the year, 1809. 1he two principles of 1L.amarckian theory, , ot, sints,, andtors.andAPpearance, pharyngeal, gll, yoll ac the appearance of tail in human re, T, h e, theory of use and disuse Organs, not, The ogenetic, thar are uscu oten will increase In size and, -, , now, , pught that animals do not recapitulate, , the a d s t a g e of any ancestors., , The human, , the, embry, ecapitulates, embryonic history, and not e adult history of the organisms., , The pmparative study of the embryo of, , those that are, giraffe, , is an, , not used will, , example, , of, , use, , ii The theory of inheritance of acquired, characters Characters that are, -, , during, , The embryos of tish, salamande tortoise, chick and human start, , acqulred characters and, , lite, , th nselves., , as a, , cleavage, , sie, , cel,, , to, , the zygote, and undergoto, , Neck in, , in snakes is an example for disuse theory, , ditferent i m a l s shows structural similarities, , among, , degenerate., , and absence of limbs, , the lite time of, , an, , organism, , developed, calied, are, , these are then inherited., , The main objection to Lamarckism, (Lamarck's Theory of Acquired characters", , roduce the blastula. change, gastrula and re triploblastic. This indicates, , was disproved by August Weismann who, , that all the ove said animals have evolved, , conducted experiments on mice tor twenty, generations by cutting their talls and breeding8, , rom a c o m m ancestor., , them. All mice born, , Molecular dences, Molecular cvolution, of change in e, , is, , the, , process, , sequence composition of, , molecules such DNA, RNA and proteins, , across generatis.t, , uses, , principles, , of, , evolutionary b i o y and population geneties, , somatoplasm, , generation, , development of molelar blology is proteins and, other, , molecules, , that o n t r o l, , conserveu among p e, , A, , ie, , Pprocesses, , will not be transferred to the next, , but changes, , in the, , germplasm, , will, , be inherited. ), , Neo-Lamarckism, , to explain patterns the changes of molecules., , One of the moserul advarncement in tne, , were with tal welsmann, , proved his germplasm theory that change in the, , followers, , he, , (Neo-Lamarckists) like, , of, , Lamarck, , Cope, Osborn, Packard, Lamarcks, , theory, explain, and, Spencer, on a more scientific basis. They considered that, tricd to, , are, , hat, , Sght change that, , adaptations, new, , are, , structures, , universal. Organisms acqulre, due, , to, , their, , adaptations, , to, , occurs over time in t h conserved molecules, (DNA,, , RNA and pr ein) are often called, , that, , They, , cxternal conditions stimulate the, , molecular clocks. Molecules that have been used, , argued, , to study evolution are cytochrome c (respiratory, , certain, somatle cells to, which reach the sex cells through the blood and, , pathway) and rRNA (protein synthesis),, , EVOIUIon, , the changed environmental conditions., , produce, , 'secrections, , bring about variations in the offspring n, , rN

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6.5.2 Darwin's theory of Natural, , found in, , Charles Darvin explained the theory of, evolutlonIn his book the Originof Species by_, Natural, Selection During his Journey around, the Earth, he made extensive observations of, plants and animals. He noted a huge variety, and remarkable similarities among, , organism, , and their adaptive features to cope up to their, environment., , proved that httest organlsms, He, and, than the, can survive, leave, more, progenies, unht ones through natural seiection., on several facts,, Darwins, theory, was, based, observations and intluences. They are!, 1. Over production, , (or), , organisms, , prodigality of, increase, , their, , population in larger number. For example,, , Salmon ish produces about 28 million eggs, during, , brecding, , season, , and if all of them, , hatch,, , the seas, generations. Elephant, the slowest breeder that, can produce six young ones in its life time can, , would be hled with salmon in tew, , produce 6 million descendants at the end of 750, years in the absence of any check., , hem, , 0, , oVercome, , Organisms struggle, , next generation., , 4. Origin of species by Natural Selection, According to Darwin, nature is the most, , powerful selective force. He compared origin, of, , species, , by, , natural selection to a small, , solated group. Darwin belleved that the, , struggle for existence resulted in the survival, of the fittest. Such organiams become better, adapted to the changed environment.), , Objections to Darwinism, Some objections ralsed against Darwinism, were-, , Darwin falled to explain the mechanism, of variation., Darwinism, , explains, , the survival, , of the, , fittest but not the arrival of the fittest., , He focused on small fluctuating variations, that are mostly non-heritable., , He did not distinguish between somatic, and germinal variations., He could not explaln the occurrence ot, , strugge for existence, lor, , tood, space, , and, , matc., , As hese oecome a mng 1actor, competition, eriss among the members o, ne populatbon. Darwin denoted struggle for, existence in three, , organism hep, , struggle and such variations are passed on to the, , Selection, , All, All iving, , an, , ways, , vestigial, , organs,, , over, , specialization, , of, , some organs like large tusks in extinct, mammoths, oversized antlers in the, extinct Irish deer, etc.,, , Neo Darwinism, , Intra specific struggle between the same, species for food, space and mate., , Neo Darwinism is the Interpretatlon, , Inter speciic struggle with diferent species, for food and space, , of Darwinian evolution through Natural, Selection as has been modified since it, was proposed) New facts and discoveries, , Struggle with the environment to cope, with the dimatic variations, flood, earthquakes,, , drought, etc.), 3. Ualversal occurrènce, No two, , of varlations, individiuals are allke. There are, , parents difter, , led, , to, , modifications, , Aof Darwinism and is supported by wallace. | M, Heinrich, Haeckel, Weiamann and Mendel., , variations even in identical twins. Even the, ot the same, in colour., helght, behavior, etc. The useful varlations, , children born, , about evolution have, , This theory emphasizes the change In the, , frequency, , of genes in, , population arises due, , o mutation, variation, isolation and Natural, , selection.), EVOluion

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ii. Chromosomal, , 6.53 Mutation theory, , go, , ,, , theoy., , Vries, , de, , Mutations, , that occur in, , an, , put forth, , are, , changes, , the Mutation, , due, , sudden random changes, , experiments the Evening, , too, , about genetic variations in the individuals, , origin ot new, Darwin believed, , of the same species and leads to heritable, variations., , in gradual accumulation of all variations as the, , causative factors in the origin ot new species., , This, , Genetic, recombination is due to crossing, over ot genes during melosls. This brings, , ii., , variations were responsible ior the, Lamarrk and, , translocation., , or, , produces varlations in their offspring8, , According to de Vries, sudden and large, , Species whereas, , addition, duplication., , deletion,, , alters the phenotype of an organism and, , in, , Primose, plant (Oenothera lamarckiarand, observed varlatlons in them due to mutation., , the, , in the structure ot chromosomes, , inversion, , organisn that is not heritableDe, , Vries carried out his, , to, , mutation refers to, , iv. Natural selection does not produce any, , are random and directionless, but Darwinian, , genetic variations but once such variations, occur it favours, , variations are small and directional., , while rejecting others (driving force of, , Hugo, , de, , Mutations, , Vries believed that, , some genctic changes, , evolution)., , Hugo de Vnlen beleved that upeciation, are due to Mutation and alled ualtatlon, ainge step large Mutation), , transmitted, , discontinuous, v, generations., , or, to, , preventing, , 6.5.5 Evolution by anthropogenic, sOurccs, , Y/Natural Selection (Industrial melanisn, , other, , I n naturally breeding populations, mutations, occur from time to time., , There are, , no, , intermediate torms, as they are, , fuly fledged., They, , are, , strictly, , subjected, , to, , natural, , selection. ), , Natural selection can be explained, , chearly through, , melanism., , industrial, , Industrial melanism is a classical case of, Natural selection, by the, moth, Biston betularia. These were avallable, , exhibited, , peppered, , in two colours, white and black Before, , 6.54 Modern synthetic theory, , Sewell Weight, Fisher, Mayer, Huxley,, Dobzhansky, Simpson and Haeckel explained, Natural Selection in the light of Post.Darwinian, discoverie According to this theory gene, mutations/ chromosomal mutations, genetic, , industrialization, , peppered, , moth, , both, , white and black coloured were common in, England., , Pre-industrialization witnessed, background of the wall of, , white coloured hence, , the buildings, , noths escaped trom, industrialization, the, , the, their, tree, , white, , coloured, , predators., trunks, , Post, , becamne, , recombinations, natural selection and, reproductive isolation are the five basic factors, , dark due to smoke and soot let out from the, , involved in the process of organic evolution., , industries., The black moths camouflaged on, the dark bark of the trees and the white moths, , Gene mutatlon refers to the changes in the, structure of the, , gene., , It is also, , point mutation. It alters the, , an organism, , and, , neir oftapng, , produces, , called gene, phenotype of, variations in, , were easily identified by their predators., Hence the dark coloured moth, was, when, , selected, , and, , compared, , offered, Evolution, , isolationbetween, helpsrelatedin, , interbreeding, , organisms. K, , Salient features of Mutation Theory, Mutations, , Reproductive, , ., , positive, , their, , number, , population, increased, , to the white moths., , selection, , pressure, , Nature, to, , the

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black coloured moths. The above proof shows, , that time, Darwin's finches have evolved into, , that in a population, organisms that can adapt, , 14 recognized species differing in body size,, , will, , beak, , survive, , and, , produce, , progenles, , more, , resulting in increase in population through, , the, , atural sclection., , ia, human, , different, , selectios a byproduct of, , exploltation, , ot, , forests,, , variants, , single species, , of, , cactus, , oceans and, , dog., , have enabled, , the, , to, , speces, , behavior. Changes in, beak, , uze, , dierent 1ood, , resources such as insects, seda, nectar from, , Tsheries or thehundreds, use of pesticldes, herbicides, bave, or, drugs., For, of, years, humans, selected various types of dogs, all of which are, of the, , shape and feeding, , size and form of, , driven, , tlowers, , and, , blood, , from, , iguanas,, , all, , by Natural election. Fig.6.5 represents, , some of the finches observed by Darwin., , Genetic, variation in the ALXI gene in the, DNA of Darwin finches is associated with, , lf human, , beings can produce new varieties in short, , variation in the beak shape. Mild mutation in, , period, then "nature" with its vast resources, , the ALXI gene leads to phenotypic change in, , and long duration can easily produce new, , the shape of the beak of the Darwin finches., , specles by selection, , Marsupials in Australa and placental, , %, , 6.5.6 Adaptive Radiation, , mammals, , short time., , Darwins, , tinches, , ALBtralan marsupials are best, tor, , adaptive, , radiation., , When, , than 100 million, , in, , continued, , and, , in, , uneB, each line, independently. Despite, , year ago, , evolve, , to, , empora, marsupials, , and, , examples, , more, , and, , geographicaland separation,, placental, , Australia, , mammals in North America have, produced, varieties of species living in similar habitats, , than, , one adaptive radiation occurs in an lsolated, , geographical area, having the same structural, , w n m a r ways ot te., , and, , resemblance, , functional, , similarity is referred, , to, , two, , separated Irom the common ancestor more, , closely relaled groups that have evolved, relatively, , are, , a, , radiation, , exemplified, , America, , similar way, inlocomotory, to particular food resource., skill or climate. They were, , ancestral torm becomes adapted to newy, invaded habitats is called adaptive, best, , Norih, , subclasses ot mammals they have adapted, , The evolutionary process which, Prduces new species diverged from a single, Adaptive radiations are, , in, , as, , in, , shape,, , Their overall, , locomotory, , mode,, , convergent evolution., , feeding and foraging are superimposed, , Darwin's finches, , leature relects thelr distinctive, , upon ditterent modes of reproduction. This, evolutionaryY, , relatíonships., , Their common ancestor arrived on the, , Over 200 species of marsupials live in, , Galapagos about 2 million years ago. During8, , along with many, Australia, tewer, species of placenta, , ch ground tndh, , mammais ibe marsuplals, , Cankalna, , h a v e under8one adaptive, radiation, , me, , the, , Australla,, u, , occupy, , habitats, , Just, , as, , in, , the, , placental mammals have, radiated, , nnne, , to, , diverse, , across, , North, , America., , merica., , Fig 6.5 Darwin's finches, Evolution

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black coloured moths. The above proof shows, that in a population, organisms that can adapt, will survive and produce more progenies, , that time, Darwin's finches have evolved into, 14 recognized species differing in body size,, beak shape and feeding behavior. Changes in, , resulting in increase in population through, , the size and torm ot the beak have enabled, , natural selection., , different, , riclal, , selection. s a byproduct of, , human exploltation ot, , foresd,, , Oceans anu, , fisheries or the use of pesticides, herbicides, , or druga. For bundreds of years humans have, selected various types of dogs, all of which are, variants of the single specles of dog. If human, , beings, , produce, , can, , new, , varieties in short, , period, then "nature" with its vast resources, and, long duration can easily produce new, , species by selkctiond, Adaptive, , C, , The, , A, , Radiation, , evolutionary, , process, , which, , produces new species diverged from a single, , ancestral, , invaded, , form, , becomes adapicu to, y, habitats ls called adaptive, raaaton, best, in, , exemplified, Adaptive rad iations are, closely related groups that have evolved in, short, relatively, Australian, , time. Darwin's finches and, , marsupials, , are, , best, , examples, , tor adaptive radiation. When more than, one adaptive radiation occurs in an isolated, geographical area, having the same structural, and functional similarity is referred to as, , to utilize, species, different food, resources such as insects, seeds, nectar irom, , cactus flowers and blood from iguanas, all, driven, , by Natural selection. Fig. 6.5 represents, some of the finches observed by Darwin., Genetic variation in the ALXI gene in the, DNA of Darwin finches is associated with, variation in the beak shape. Mild mutation in, , SM, , in, the ALXI ofgene, leads, to, phenotypic, change, the beak of the Darwin finches., , theshape, , Marsuplals in Australia and placental, , are, mammals, In North America, subclasses of mammals, have, , they, , two, , adapted, , in similar way to a particular food resource,, skill or climate. They, from the common ancestor, , locomotory, , separated, , and each, than 100 million year ago and, each, o, year, , to, , were, , more, , lineage, Despite, , continued andevolve, independently., geographical separation,, , temporal, , marsuplals, , n, , mammals, , North, , uin, , Australla, , and, , placental, , America have produced, , varieties of species living in similar habitats, , with similar ways of life. Their overall, resemblance in shape, locomotory mode,, , feeding and toragingofare superimposed, This, , convergent evolution., , upon ditferent their, modes, , Darwin's finches, , teature retlects, , T h e i r common ancestor arrived on the, , Galapagos about 2 millon years ago. During, , reproduction., , distinctive, , evolutionary, , relationships., , Over 200 species of marsupials live in, , Australia along with many, species of placental, , fewer, , Certids, oac), , mammals. The marsupials, CaoloqM, , have undergone adaptive, radiation, nch (de, , CainatvnGhe, , a t in, , radiated, , (, , occupy, , the diverse habitats in, Australla, just as the, , iapiabrPaen, h, , to, , mammais, , have, , across, , America., , Fig 6.5 Darwins finches, EWOUiOn, , 1NCOTXH 2eog. a

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TCoTXlZmyD, , ndl 101, , f a population is in Hardy Weinberg, , 6.6.4 Mutation, Although mutation is the original source, , equilibrium, the genotype frequency can, , of all genetic variation, mutation rate for, , be estimated by Hardy Weinberg equation., P+=P+ pq*q, p= frequency of AA, , most organsms is low. Hence new mutations, on an allele trequencies trom one generation, to the next is usually not large., , 2pq- frequency of Aa, , 6 . 7 Hardy - Weinberg Principle, , 9, , I n nature, populations are usually, evolving such as the grass in an open meadow., , P-0.3,9- 0.7 then,, , pP-(0.3), , wolves in a forest and bactería in a persons, , likely, , to, , be, , evolving, , the population is moving towards perection, , makeup over generations. For example in, , wol population,, , there, , may, , be, , a, , a, , shift in the, , of gene, frequency, variant for black fur than, grey fur. Sometimes, this type of change is, a, , due to natural selection or due to migration, Or aue to random events., , Hence the beetle population appears to, , be in Hardy- Weinberg equilibrium. When, beetles in Hardy- Weinberg equilibrium, reproduce, the allele and genotype requency, , the, , in the next generation, would be:, Lets assume, ot, a allele in the, , that, the trequency Aand, pool of gameles that make the next generation, would be the same, then there would be, no variation in the, progeny. n e, , 8enoYPE, , First we will see the set of conditions, required for a population not to evolve( Hardy, , reguencies of the parent appears in the next, generation. (iLe. 9*% AA, 42% Aa and 49% aa)., , of, UK and Weinberg of Germany stated that, the allele trequencies in a population are, , randomly, , stable and are constant trom generation to, , generation in the absence of gene tlow. genetic, , fwe assume that the beetles mate, (selection, , temale gamete, , in the, , ot, , male 8amete and, , poolo gametes), the, , probabiity ot getting the ofspring genotype, , drift, mutation, recombination and natural, , depends on the genotype of the combining8, , selectionf a population is in a state of Hardy, or, , parental gametes., \, Hardy Weinberg's asaumptions include, , Evolution is a change in the allele trequencies, , by mutation nor the genes get duplicated or, , n, , deleted., , Weinberg equilibrlum, the, , trequencles of, , and, alleles, genotypes sets of alleles in that, population will remain same over generations., a population over time. Hence population, , in Hardy Weinberg i, , No mutation - No new alleles are generated, , Random, , not evovng), , large Population o, Suppose, "beetles, (infinitely large) and appear in two, we, , have a, , mating, , -Every, , organism, , gets, , a, , chance to mate and the mating is random, with each other with no prelerences tor a, , colours, dark grey (black) and light grey, and, their colour is determined by 'A' gene. AA, , particular 8enotype., , and 'Aa' beetles are dark grey and 'aa' beetles, , their gametes enter (immigration) or exit, (emigration ) the population., , are light grey. In a, , 'A, say, allele has frequency (p) of 0.3 and 's' allele has, , population lets, , that, , a frequency (q) of 0.7. Then p+q=l., Evolutlon, , % AA, , q- (0.7) 0.49 49 % aa, , some, , of their genes. Evolation does not mean that, rather the Population s changing ts genenc, , 0.09 9, , 2pq- 220.3) (0.7) - 0.42 42 % Aa, , body are all natural populations. All of these, , populations are, , requency ot aa, , No gene flow Neither individuals nor, , Very large population size - The population, should be intinite in size., , 102, , No natural selection- Al alleles are fit to, , Australian ape man. He was about 1.5 meters, , survive and reproduce., , tall, , lf any one of these asumptions were not, met. the population wil not be in, rdy-, , semi erect, and lived In caves. Low torehead., , Weinberg equilibrium. Only if the allele, , lack of chin, kow brain capacity of about 3>u, , frequencies changes from one generationA, the other, evolution will take place:, , 50 cc human like denttion, lumbar curve in, the vertebral column were his distinguishing, , 6.8 Origin and Evolution ofMan, , teatures., , Mammals evolved in the, , In Aia and Africa Hominids, , bipedal, , locomotion. omnivorous,, , brow ridges over the eyes,, , protruding tace,, , Homo habilis lived about 2 mya. Their, brain capacity was between 650 -, , early Jurassic period, about, 210 million years ago (mya)., Hominid evolution occurred, , with, , 800cC, and, , was probably vegetarian. They had bipedal, locomotion and used tools made of chipped, , 5Y, , stones., . .