Evoluti tion on THE THEORY ORY OF Very slow change in a species - PDF document

2/18/2013 Evoluti tion on THE THEORY ORY OF Very slow change in a species EVOLUTION UTION over vast periods of timem 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? HISTORY OF EVOLUTIONARY THEORY 1801: Jean Lamar arck ck (French) Is evolutio tion n fact or theory ry? 1. Theor ory y of desire Both! - organisms change due to inborn desire to change to become more fit for environment ex: ant eaters develop long snouts FACT: things change over time, documented in 2. Theor ory y of use and disus suse fossil record - organs that are being used get large and strong - organs that are not used shrink and eventually disappear ex: snakes- didn’t use legs so disappeared THEORY: evolution is a collection of carefully whales- used to be land creatures, legs became fins reasoned and tested hypotheses about 3. Theor ory y of inheritance ance how evolutionary change occurs - acquired traits were passed on to offspring ex: snakes that lost legs passed trait 1

2/18/2013 1859: Charles s Darwin (English) What factor determines which individuals survive and reproduce? Influences in Darwin’s theory of evolution: 1. Geolog ogy Lyell (geologist) said earth changed over time Darwin’s Theory of Natural Selection 2. Artifici cial al select ction on Process whereby with human intervention superior specimens are bred to produce superior offspring with desired traits Natura ral selecti tion ex: larger bulls cows that produce more milk Individuals that have physical or behavioral traits ts that larger ears of corn better suit their r enviro ronment are more likely y to survive 3. Popul ulat ation on control ols and will repro roduce more success ssfully than those Malthusian Doctrine (human population is controlled by famine, disease, and war) without traits. - applied even more to plants and animals Parts of Theo eory 1. Overprod oduction ion - organisms produce more offspring than can survive 2. Genetic etic varia iatio ion - individuals in a given species vary by chance (due to gene recombination)…………. this is normal. exception: identical twins 3. Struggle le to surviv ive - all organisms face constant struggle to survive (limited resources) ex: pond ecosystem – cattails compete with duckweed for surface of lake water 4. Surviv ival of the e fittes est - Individuals best adapted to environment are more likely to survive and reproduce DIFFERENCE IN THEORIES 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 2

2/18/2013 Examples of Natural Selection Examples of Natural Selection, cont. 1. Industrial Melanism: Peppered Moths 2. Antibiotic Resistance: T.B. and other bacteria natural selection video Examples of Natural Selection, cont. Nov. 1859: Darwin published book 3. Pesticide resistance “Origin of the Species through Natural Selection” 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 UPDATES ON DARWIN’S THEORY 3. Evolutionary change involves change in allel lele frequen ency in the gene pool of a population 1. Genes are carriers of characteristics and source of random variation. Popula lation ion: collection of individual of same species in specific area that can successfully breed. (caused by mutations) - offspring share same gene pool 2. Variat ation is the raw material for natural selection. Gene e pool: common group of genes - Natural selection can operate only thru phenoty typi pic variat ations. s. Relativ ive e frequen ency: how often alleles show up - Since genes come in pairs (alleles), some (physical and behavioral characteristics produced occur more frequently by genotype and environment) - As relative frequency changes, distribution of traits changes 3

2/18/2013 Examples s of Adaptation ions 4. Evolutionary fitness and adaptation depends on success of organism passing its genes (traits) to its offspring • adaptation ion: - genetically controlled characteristics (physical or behavioral traits) - increase an organisms fitness for its environment FACTORS IN SPECIATION 5. Formation of species -Gene pools change thru natural selection - spec ecies ies: : group of organisms that breed and 1. Reprod oduct uctive Isol olat ation on: two to the point where same species becomes populations of same species do produce fertile offspring different over time and can no not breed with each other due to longer breed geographic separation - normal -Two populations now considered to be two different species - members share a common gene pool - if beneficial gene- increases fitness - Can occur thru rivers, mts., roads, members of a species can evolve together courtship behavior, fertile periods ex: isolation by grand canyon - spec ecia iation ion: development of a new species through evolution Kaibob squirrel Abert squirrel 2. Migration ion (gen ene e flow) movement of large numbers of organisms of same species from one 3. Adaptiv ive radia iation ion (div iver ergen ent evolu olutio ion): process by environment to another (immigration or emigration) which different species arise from one - eventually leads to adaptation from natural selection to environment common ancestor - results in change in gene frequency - if population breeds with existing population there is a change in gene pool - organisms evolve new characteristics that enable them to survive in different environments Ex: camels: originated in N America but migrated around the world, ice age destroyed most except those in scattered areas - over time it is difficult to tell which species are related Asian ex: Darwin’s finches African Llama 4

2/18/2013 - 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. 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 diss ssimilar ar struct uctur ures s  mor ore similar ar struct ctur ures - doesn't work to produce adaptations since random 5

2/18/2013 2. Unchan angi ging g gene pools: if species is very well 3. 3. Gradualism 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) Horse Fossil Record - gradualism 4. Equilibr ilibriu ium: organism does not change every much over time ** explains gaps in the fossil record ** (60 million years) - punctuated ed equilibr ilibriu ium: long stable period interrupted by brief periods of change (sometimes events occur to disturb equilibrium) - causes rapid change in small groups of organisms - usually fills new niche - could cause mass extinctions Co Co-evo volu lution on Microe roevo volu lution ion • Evolution on a small scale within a single population • The mutual evolutionary influence between two species • Changes gene frequency within that population (the evolution of two species totally dependent on each other) • Each of the species involved exerts selective pressure on the other, so they evolve together • Extreme example of mutualism 6