o Change over time of the genetic composition of a population o Decent of modern organisms with modification from preexisting organisms o Accumulation of inherited characteristics that enhance organisms ability to survive in o Bodies of living organisms are modified through the use or disuse of parts o IE Giraffes ancestors had short legs and short necks and they stretched all their life so they CHAPTER 22 Descent with Modification A Darwinian View of Life What is Evolution and Adaptation Evolution two main ideas Evolutionary adaptation specific environments Survival of the fittest Pre Darwinian Theory of Evolution Lamarck Use and disuse got a little longer Inheritance of acquired characteristics o These modifications are inherited by offspring These ideas turned out to be wrong Evolution by Natural Selection Darwin and Wallace developed the theory independently Darwin voyage of the Beagle Wallace naturalist in Indonesia Natural Selection preservation of favorable adaptations Process selects from what is available in the gene pool New characteristics are not created on demand Mechanism behind Natural Selection The unequal survival and reproduction of organisms due to environmental forces resulting in the o Considering perfect conditions plenty of food space water etc o Think of the 100 m dash track and field competition How can we change this race to reflect the process of natural selection Handicapped cheetah etc Artificial Selection Selective breeding of organisms to encourage the occurrence of desirable traits Analogous to natural selection the environment has obviously a large impact on this Concept 22 3 Evolution is supported by an overwhelming amount of Scientific Evidence Examples of Natural Selection o Fig 22 13 The Rise of MRSA o Homologous Analogous Structures Homologous Structures common ancestry o Structures or other attributes in difference species that resemble each other because of o o Vertebrate Embryos development All vertebrates share similar developmental genes Differences arise by some genes being switched on or off at varying times during o Biochemistry and Molecular biology DNA is universal genetic material All life forms use approximately the same 20 amino acids to make proteins All use ATP as the primary form of cellular energy All use RNA and ribosomes to make protein o Homologies and Tree Thinking o Trees vs Scala Naturae Scala Naturae Analogous evolutionary origin Convergent Evolution Convergent evolution Ladder of nature see pg 453 Evolution not about climbing ladder of nature from lower to higher Evolution is a bush with lineages branching from one another o Structures that are similar in function but not in structure and developmental and o Similarity b n 2 organisms structures or molecules due to independent evolution along similar lines rather than descent from a common ancestor Fossil Record Show change in organisms through time Change in types of organisms o Past organisms differ from present day organisms o Many species have become extinct Not only provides evidence of small scale changes but of origin of major groups o EG The cetaceans Clicker homology is least likely in legs of a bird and an insect CHAPTER 23 The Evolution of Populations The Smallest Unit of Evolution One misconception about evolution is that individual organisms evolve during their lifetime Evolutionary processing natural selection act on individuals but populations evolve Concept 23 1 Genetic variation makes evolution possible o EG X MEN Mutation Mutations changes in the nucleotide sequence of DNA o Source of new alleles and genes o Point mutation change in one nucleotide base in a gene o Chromosomal mutations delete disrupt or rearrange many loci on a chromosome o Gene duplications duplication of whole segments of a chromosome o Mutation rate average 1 in every 100 000 genes per generation Sexual Reproduction In sexually reproducing organisms sexual recombination produces most of the variability in each generation o IE crossing over in prophase 1 o IE independent assortment during metaphase 1 Variation within a population Discrete characters classified on an either or basis o EG flower color in pea plants Quantitative characters vary along a continuum within a population o EG height and weight o not in notes Concept 23 2 The Hardy Wienberg equation can be used to test whether a population is evolving Populations not in notes Population a group of individuals of the same species living in a certain defined area Hardy Wienberg Equilibrium H W equilibrium describes a population that is not evolving ie allele frequencies don t change Five assumptions behind the H W Equilibrium o No Mutations o Large Population Size o No Gene Flow o No Natural Selection o Random Mating Allele and genotype Frequencies P frequency of allele 1 q frequency of allele 2 P Q 1 Genotype Frequencies P2 frequency of homozygous dominant Q2 frequency of homozygous recessive 2PQ frequency of heterozygotes P2 2PQ Q2 1 H W equation H W Equilibrium H W equation can be used to estimate of the human population carrying the allele for an Population Genetics And Human Health inherited disease PKU is a recessive genetic disorder o Frequency of homozygotes with this disorder is Q2 0001 Clicker What is the frequency of the dominant and recessive alleles P Q P 99 Q 1 because p q 1 Clicker The frequency of carriers heterozygous people who do not have PKU is 0198 because Q2 0001 q 0001 01 P Q 1 P 01 1 P 99 P2 2pq q2 1 2 99 01 0198 Clicker If a population has the following genotype frequencies AA 42 Aa 46 aa 12 what are the allele frequencies A 65 a 35 AA 42 p2 2pq 12 Clicker If the frequency of the recessive allele is 30 the frequency of the heterozygous carriers would be 42 because q 3 p 7 2pq 2 7 3 42 or 42 Concept 23 3 Natural Selection genetic drift and gene flow can alter allele frequencies in a population Genetic Drift Statistically the smaller a sample the greater the chance of deviation from a predicted result With small population sizes allele frequencies can fluctuate unpredictably from one generation to the next Tends to reduce genetic variation o Gene Flow Genetic additions to or subtractions from a population resulting from the movement of fertile individuals or gametes Migration among populations Tends to reduce variations among populations over time o High Migration little genetic variation between populations o Low Migration more genetic variations between populations Concept 23 4 Natural Selection is