BEYOND NATURAL SELECTION



NATURAL SELECTIONBEYOND NATURAL SELECTIONWe now understand that natural selection is just ONE of a number of processes that can lead to evolution. This knowledge has resulted in the development of a more complex understanding of genetic change = THE SYNTHETIC THEORY OF EVOLUTION = a combo of Charles Darwin’s Natural Selection & Gregory Mendel’s Genetic Inheritance along with population genetics and molecular biology of the 20th centuryNATURAL SELECTIONGenes are the carriers of inheritable characteristicsThey are also the source of random variation upon which natural selection operates________________ causes some variation________________ is when most variation occurs during the copying, shuffling and dealing of genes to the gametes and crossing overRemember, ____________________________________________, it is not controlled or directed toward a goalHow Natural Selection WorksIn the struggle for survival, ____________________, not genes, either survive & reproduce, or do notNatural Selection operates on ______________________________ between individualsPhenotypic = physical & behavioral characteristics produced by the interaction of genotype & environmentMore “fit” individuals will have more success mating and will live longer therefore producing more offspring in the next generationIn essence, this is selection because individuals who are phenotypically fit will produce more offspring, thus causing a change in the genetics of the next generation EVOLUTION AS GENETIC CHANGE____________________________: individuals of the same species in an area who breed with one anotherGENE POOL: _________________________________________________________________________: number of times an allele appears in a population compared to the other alleles of the same geneEVOLUTIONARY CHANGE INVOLVES A CHANGE IN THE RELATIVE FREQUENCIES OF ALLELES IN THE GENE POOL OF A POPULATIONPOPULATION GENETICSStudy of genetic traits in individualsGenotype – actual allele inherited from each parent that the individual has (blue eyes, brown eyes)Phenotype – resulting observable characteristic from the interaction of the individuals genotype (brown eyes)Study of genetic traits in populationsGene Pool: combined genetic material of all the members of a populationAlleles: name for the 2 or more different forms of a gene. (gene = eye color, alleles = blue, brown, green) Allele Frequency: is a fraction that represents the frequency of a particular allele within a populationHARDY-WEINBERG PRINCIPLEIf a population is not evolving, allele frequencies are in Genetic EquilibriumUnder specific conditions allele frequency remain constantIf those conditions are not met the population may EVOLVEConditions required to maintain G.E. are:_________________________________________________________________________________________________________________________________________________________________________________________If all these conditions are met, and the allele frequencies are not changing between generations, then the population is in?Hardy-Weinberg equilibrium?and is not evolving.In nature, one or more of these assumptions is always being violated. Real populations are compared against the Hardy-Weinberg model to see if they are evolving MECHANISMS OF EVOLUTIONMECHANISMS OF EVOLUTION1 NATURAL SELECTION - Over-reproduction + Variation CompetitionCompetition for survival & REPRODUCTION = Survival of the Fittest Heredity to next generation Evolution2 MUTATIONchange in the DNA sequence within a ___________________________________________ of a living organism.Can be Neutral, Harmful or Beneficial to fitness of the individual_________________________?= gametes (eggs or sperm cells) can be pass on to offspring_________________________?= non-reproductive cells are not pass on to the following generation. 3 GENETIC DRIFTRandom change in allele frequency due to a random eventDoes not necessarily result in ADAPTIVE evolutionOccurs more/ Has more impact on SMALL populationsTwo main types or Genetic Drift = Bottle Neck Effect = ____________________________________________________________________Founders Effect = ______________________________________________________________________4 MIGRATIONthe transfer of genes from the gene pool of one population to anothermay change the frequency and/or the range of alleles in the The introduction of new alleles?increases variability within a population?and allows for new combinations of traits.40386008953500DISTRUBUTION & SELECTIONThe normal distribution of variations in a population can change by natural selectionEvolution results _________________________________STABALIZING SELECTIONThese curves are called normal distributions because the patterns is so common in natureThis is selection ____________________________and may result in reduced variability over timeDIRECTIONAL SELECTIONThis type of selection occurs when a change in the environment makes it infavorable to have ______________________________________________DISRUPTIVE SLELECTIONThis type of selection occurs when an environmental change makes it unfavorable to have the most ________________________________________CONCEPT OF A SPECIESA species is a group of interbreeding individuals or populations that are reproductively isolated from other such groupsSPECIATIONSpeciation involves environmental processes that lead to the splitting of a gene pool into two or more separate poolsMAJOR CAUSES:_______________________________________________________________________________________________________________SPECIATION - REPODUCTIVE ISOLATING MECHANISMSThe key event in speciation is Reproductive Isolation between two diverging populations Isolating mechanisms are all genetically based and can be either pre-zygotic or post-zygoticPRE-ZYGOTIC = ________________________________Seasonal/habitat barriers to mating, behavioral isolation, physical isolationPOST-ZYGOTIC = ________________________________Gamete mortality, hybrid non-viability, hybrid sterilitySPECIATION - GEOGRAPHIC ISOLATIONSimplest mechanism of isolationContinents collide, mountains are uplifted & suddenly a population finds that it is splintered into a large population as well a number of geographically isolated smaller populationMost of these small populations ____________________________SPECIATION - COURTSHIP BEHAVIORSOften the behaviors a male must engage in to convince the female of his proper species-hood are quite elaborate and cannot be reproduced by member of a different speciesVarious behavioral cues allow males & females to recognize their own speciesPUNCTUATED EQUILIBRIUM VS GRADUALISMDarwin saw evolution as a slow, continuous process, without sudden jumps (GRADUALSIM) however, if you study the fossil record, you will see long intervals in which nothing changed (EQUILLIBRIUM) punctuated by short, revolutionary transitions in which species became extinct and replaced by new forms (PUNCTUATED EQUILIBRIUM)Instead of a slow progression, evolution of life seems more like the life of a fire-fighter: long periods of boredom interrupted by rare moments of terror.TYPES OF EVOLUTIONThe basic evolutionary mechanisms-mutation, migration, genetic drift, and natural selection- can produce major evolutionary can change if given enough timeTHERE ARE 3 MAJOR TYPES OF EVOLUTION:_________________________________________________________DIVERGENT EVOLUTION= THE PROCESS OF 2+ RELATED SPECIES BECOMING MORE DISSIMILAREx. Red Fox (forests, red) and Kit Fox (prairies, tan)Similarities in structure show that they have a common ancestor, but as they adapted to different environments, they divergedCONVERGENT EVOLUTION= WHEN ORGANISMS THAT ARE NOT CLOSLY RELATED EVOLVE SIMILAR TRAITSEx. Antifreeze proteins in both Antarctic and Arctic fish Ex. Wings of a bat and birdCOEVOLUTION= JOINT CHANGE IN 2+ SPECIES IN CLOSE INTERACTIONOften occurs betweenPredators and preyParasites and hostsEx. Plants and the animals that pollinate themEXTINCTION99% of the species that have ever lived on earth have gone extinct! Present day biodiversity is a result of an accumulation of changes due to extinction events over millions of yearsEXTINCTION CONTAINS 3 KEY ELEMENTS:For geographically widespread species extinction is rareLarge mass extinctions produce major restructuring of the biosphere and allowing previously minor groups of expand and diversifyIt is generally impossible to predict which species will be victims of an extinction eventReview – Practice Questions – Critical Thinking Why is natural selection acting on Phenotype not genotype?Why are harmful alleles most often either recessive or late onset?Natural selection is not the only cause of evolution, explain?Why are smaller populations more vulnerable to extinction and genetic drift? ................
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