THE THEORY ORY OF EVOLUTION UTION Evoluti tion on Process by - PDF document

2/18/2013 THE THEORY ORY OF EVOLUTION UTION Evoluti tion on Process by which living organisms descend from ancient ones by a series of changes resulting in some species becoming extinct and new species developing from previous ones. (change over time) Charl arles s Darwin: father of evolution “Origin of the Species thru Natural Selection” Why did some species s survive and flourish sh and others rs become extinct? t? 1

2/18/2013 POINTS THAT SUPPORT EVOLUTION 1. Varia iation ion exists within the genes of every population or species. (result of random mutation) Is evolutio tion n fact or theory ry? Both! 2. In a particular environment, some individuals of a population or species are better er suit ited ed to surviv ive (as a result of variation) and have more offspring. (natural selection) FACT: things change over time, documented in fossil record 3. Over time, the traits that make certain individuals of a population able to survive and reproduce tend to sprea ead in that popula lation ion. THEORY: evolution is a collection of carefully reasoned and tested hypotheses about 4. There is clear proof from fossils ls and many other sources that living species evolved from organisms that are extinct. how evolutionary change occurs HISTORY OF EVOLUTIONARY THEORY 1859: Charles s Darwin (English) Influences in Darwin’s theory of evolution: 1801: Jean Lamar arck ck (French) 1. Geolog ogy 1. Theor ory y of desire Lyell (geologist) said earth changed over time - organisms change due to inborn desire to change to become more fit for environment 2. Artifici cial al select ction on ex: ant eaters develop long snouts Process whereby with human intervention superior specimens are bred to produce superior offspring with desired traits 2. Theor ory y of use and disus suse ex: larger bulls cows that produce more milk - organs that are being used get large and strong larger ears of corn - organs that are not used shrink and eventually disappear ex: snakes- didn’t use legs so disappeared 3. Popul ulat ation on control ols whales- used to be land creatures, legs became fins Malthusian Doctrine (human population is controlled by famine, disease, and war) 3. Theor ory y of inheritance ance - applied even more to plants and animals - acquired traits were passed on to offspring - produce many more offspring than can survive. ex: snakes that lost legs passed trait weight lifters would produce muscular offspring Parts of Theo eory What factor determines which individuals survive and reproduce? 1. Overprod oduction ion - organisms produce more offspring than can survive 2. Struggle le to surviv ive Darwin’s Theory of Natural Selection - all organisms face constant struggle to survive (limited resources) ex: pond ecosystem – cattails compete with duckweed Natura ral selecti tion for surface of lake water 3. Genetic etic varia iatio ion Individuals that have physical or behavioral traits ts that - individuals in a given species vary by chance (due to gene better suit their r enviro ronment are more likely y to survive recombination)…………. this is normal. and will repro roduce more success ssfully than those exception: identical twins without traits. 4. Surviv ival of the e fittes est - Individuals best adapted to environment are more likely to survive and reproduce 2

2/18/2013 DIFFERENCE IN THEORIES Examples of Natural Selection 1. Industrial Melanism: Peppered Moths Lamarc arck: organisms change in order to survive in environment - occurs in the organism’s lifetime Darwin: environment determines which organisms survive through natural selection - occurs rs over many y generat rations Examples of Natural Selection, cont. Examples of Natural Selection, cont. 2. Antibiotic Resistance: T.B. and other bacteria 3. Pesticide resistance By sprayin ing g crops s with poiso sons s to kill l insect pests, s, humans s have favo vored d the reprodu ductio ion of insects s with inherit ited d resista stance to the poiso sons over those with no resista stance 3

2/18/2013 Nov. 1859: Darwin published book UPDATES ON DARWIN’S THEORY “Origin of the Species through Natural Selection” 1. Genes are carriers of characteristics and source of random variation. - at first people were very disturbed that they were related to apes (caused by mutations) - over time theory was accepted because of very convincing 2. Variat ation is the raw material for natural selection. arguments Natural selection can operate only thru phenoty typic variat ations. s. - new discoveries in genetics give new insights into how natural selection works (physical and behavioral characteristics produced by genotype and environment) - today we define fitness, adaptation, species and process of evolutionary change in genetic terms 4. Evolutionary fitness and adaptation depends on success of 3. Evolutionary change involves change in frequency of alleles in organism passing its genes (traits) to its offspring the gene pool of a population - adaptation ion: genetically controlled characteristics (physical or behavioral traits) that increase an Popula lation ion: collection of individual of same species in organisms fitness for its environment specific area that can successfully breed. 5. Formation of species - offspring share same gene pool - spec ecies ies: : group of organisms that breed and produce fertile offspring Gene e pool: common group of genes - variation within species is normal - members share a common gene pool Relativ ive e frequen ency: how often alleles show up - if beneficial gene is spread thru a population and increases fitness, members of a species can evolve - Since genes come in pairs (alleles), some together occur more frequently - As relative frequency changes, distribution - spec ecia iation ion: development of a new species thru of traits changes evolution FACTORS IN SPECIATION Examples s of Adaptation ions 1. Reprod oductiv ive e Isola olation ion: two populations of same species do not breed with each other due to geographic separation In this model, , arrows symbol olize e population ons that become e geog ographically separated ed, , then come toget ether er again at a later time. e. 4

2/18/2013 Repro roducti tive Isolat ation - Gene pools change thru natural selection to the point where same species becomes different over time and can no longer breed - Two populations now considered to be two different species - Can occur thru rivers, mts., roads, courtship behavior, different fertile periods ex: isolation by grand canyon Kaibob squirrel Abert squirrel 2. Migration ion (gen ene e flow) movement of large numbers of organisms of same species from one environment to another (immigration or emigration) 3. Adaptiv ive radia iation ion (div iver ergen ent evolu olutio ion): process by - eventually leads to adaptation from natural selection to environment which different species arise from one - results in change in gene frequency - if population breeds with existing population there is a change in common ancestor gene pool Ex: camels: originated in N America but migrated around the - organisms evolve new characteristics that enable world, ice age destroyed most except those in them to survive in different environments scattered areas Asian - over time it is difficult to tell which species are related African ex: Darwin’s finches Llama - Darwin visited Galapogos Islands (620 mi. off Equador) How Adaptive Radiation Occurs - noticed 14 species of finches - evolved from common ancestor in S.A. - each of 14 species had traits to allow them to survive in different niche he Adapt aptive radiat ation on on an island and chain n may lead to several al new bird speci cies s evolving ng from one found nding ng popul pulat ation. on. 5

2/18/2013 Examples of adaptive radiation, cont. Examples of adaptive radiation, cont. Homol olog ogous ous struct uctur ures: : structures which developed from a common ancestor, but have changed over time due platypus kangaroo to different purposes anteater similar ar struct uctur ures s  less ss similar ar struct uctur ures 4. Conv nvergent nt evolut ution on: process whereby organisms not closely related, EVOLUTION OF EVOLUTIONARY THEORIES independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. 1. Genetic etic Drif ift: chance changes in gene pool from generation to without natural selection - organisms with different ancestors become more alike because they share same environment - causes random change in frequency of a gene - result in: analog ogous ous struct uctur ures: similar in appearance and function, but different origins with different internal structures (each evolved independently) - unlike natural selection bat wing ng v.s. . bird wing ng - doesn't work to produce adaptations since random diss ssimilar ar struct uctur ures s  mor ore similar ar struct ctur ures 2. Unchan angi ging g gene pools: if species is very well 3. Gradualism 3. sm: adapted to environment and there is no evolutionary change competition, no change occurs occurs slowly and gradually over time ex: horseshoe crabs (living fossils) 6