Chapter 22 Review In order to decide whether this is either an evolutionary change or an environmental impact you need to look at the DNA sequence If the DNA has actually changed then it would be an evolutionary change if the DNA has not changed than it would just be an environmental effect on gene expression Possible experiment to determine whether it is an environmental or genetic change move the lizards back to the original island and if they change back to normal within one generation then it is probably an environmental impact Otherwise it is evolutionary Evolution A change in the genetic composition Evolution explains why we can have an enormous diversity of species Natural selection is not evolution natural selection causes evolution to happen Requirements for Natural Selection variation in the phenotype heritable traits and environmental factor that causes an associate between the phenotype and fitness Evolution produces allele frequency changes inherited phenotypic changes differences among populations new phenotypes and new species and phylogenetic relationships Darwin came up with his ideas after voyage on the Beagle Galapagos animals were influential Wallace independently came up with same idea Lamark If one strives hard enough and has a large enough inner need then they can cause physical changes in the genotype and phenotype incorrect Darwin s Five Theories a Evolution has happened b All life has a common ancestor c The diversity of life is the result of a series of splits in the lineage family tree of living things d Natural selection is the primary mechanism driving evolutionary change Evolution occurs gradually over time e Different types of evidence for evolution f Fossil Record Nonrandom change in form over time that occurs in a consistent pattern g Homology Comparative Morphology Different species have same structures modified in different ways due to common ancestry h Convergence similar form due to action of natural selection and environment rather than common ancestry Island Species Similar to mainland but unique endemic Selective Breeding or Artificial Selection i j k Natural Selection and Species Formation in Nature Darwin incorrectly proposed that natural selection would take to long to occur in nature for him to be able to observe l Molecular Evolution Random changes in non coding DNA reflect ancestry since natural selection cannot affect non coding DNA m Genetic Homology Looking at the same gene in different species n Development and Evolution Detailed understanding of how differences in genes can lead to different developmental pathways Chapter 22 Vocabulary 1 Evolution Descent with modification the idea that living species are descendants of ancestral species that were different from the present day ones Also defined more narrowly as the change in the genetic composition of a population from generation to generation 2 Natural selection A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits 3 Adaptation Inherited characteristic of an organism that enhances its survival and reproduction in a specific environment 4 Homology Similarity in characteristics resulting from a shared ancestry 5 Endemic Referring to a species that is confined to a specific geographic area 6 Convergence The evolution of similar features in independent evolutionary lineage homology 7 Analagous Having similar characteristics due to convergent evolution not 8 Phylogeny The evolutionary history of a species or group of related species Chapter 23 Review In sexually reproducing organisms three processes lead to most genetic variation independent orientation of chromosome in meiosis a b crossing over of chromosomes in meiosis c random fertilization Evolutionary change means genetic change Not all variation is due to genetics some variation is due to the environment Evolutionary Forces If no environmental factors are involved then evolution will not occur a Genetic Drift random events occur affecting the population assume that the population is infinitely large no migration and no genetic mutations b Gene Flow migration the movement of alleles from one population to another this can take form via individuals that physically move or via mobile gametes c Natural Selection already existent traits that are inherited and help with survival and reproduction will tend to increase and spread in populations d Mutation not covered Bottleneck Effect Genetic drift that occurs when the size of the population is reduced as by a natural disaster or human actions Typically the surviving population is no longer genetically representative of the original population Frequency dependent selection how frequent the allele is depends on how many individuals have the allele in the population since both alleles have equal fitness the allele frequency fluctuates by nature since the currently preferred allele gets preyed on more causing it to decrease and the other allele to increase Conditions for Hardy Weinberg e No mutations f Random mating g No natural selection h Extremely large population size infinite i No gene flow Natural selection is the evolutionary force producing adaptive change Natural selection can be stabilizing disruptive or directional j Directional Selection Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals k Disruptive Selection Natural selection in which individuals on both l extremes of the phenotypic range survive or reproduce more successfully than do the individuals with intermediate phenotypes Stabilizing Selection Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes Chapter 23 Vocabulary 1 Cline A graded change in a character along a geographic axis 2 Hardy Weinberg Principle The principle that frequencies of alleles and genotypes in a population remain constant from generation to generation provided only that Mendelian segregation and recombination of alleles are at work 3 Balancing Selection Natural selection that maintains two or more phenotypic forms in a population Chapter 24 Review Natural Selection can only act where there are fitness differences if the allele is linked to the environment the evolutionary force is natural selection Drift and Migration can act on any locus Mutation and Drift are much more powerful forces in
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