Descent with Modification A Darwinian View of Life CHAPTER 22 What is Evolution and Adaptation cid 120 Evolution two main ideas o Change over time of the genetic composition of a population o Decent of modern organisms with modification from preexisting organisms cid 120 Evolutionary adaptation o Accumulation of inherited characteristics that enhance organisms ability to survive in specific environments cid 131 Survival of the fittest Pre Darwinian Theory of Evolution cid 120 Lamarck cid 120 Use and disuse 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 got a little longer Inheritance of acquired characteristics o These modifications are inherited by offspring cid 120 These ideas turned out to be wrong Evolution by Natural Selection cid 120 Darwin and Wallace developed the theory independently cid 120 Darwin voyage of the Beagle cid 120 Wallace naturalist in Indonesia Natural Selection cid 120 The unequal survival and reproduction of organisms due to environmental forces resulting in the preservation of favorable adaptations cid 120 Process selects from what is available in the gene pool cid 120 New characteristics are not created on demand cid 120 Mechanism behind Natural Selection cid 120 o cid 131 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 cid 131 Handicapped cheetah etc Artificial Selection cid 120 Selective breeding of organisms to encourage the occurrence of desirable traits cid 120 Analogous to natural selection cid 120 cid 120 the environment has obviously a large impact on this Concept 22 3 Evolution is supported by an overwhelming amount of Scientific Evidence cid 120 Examples of Natural Selection o Fig 22 13 cid 120 The Rise of MRSA o Homologous Analogous Structures cid 120 Homologous Structures o Structures or other attributes in difference species that resemble each other because of common ancestry o o Vertebrate Embryos cid 131 All vertebrates share similar developmental genes cid 131 Differences arise by some genes being switched on or off at varying times during development cid 120 o Biochemistry and Molecular biology cid 131 DNA is universal genetic material cid 131 All life forms use approximately the same 20 amino acids to make proteins cid 131 All use ATP as the primary form of cellular energy cid 131 All use RNA and ribosomes to make protein o Homologies and Tree Thinking cid 131 cid 120 Ladder of nature see pg 453 o Trees vs Scala Naturae cid 131 Scala Naturae cid 131 Evolution not about climbing ladder of nature from lower to higher cid 131 Evolution is a bush with lineages branching from one another cid 120 Analogous o Structures that are similar in function but not in structure and developmental and evolutionary origin Convergent Evolution cid 120 Convergent evolution o Similarity b n 2 organisms structures or molecules due to independent evolution along similar lines rather than descent from a common ancestor cid 131 Fossil Record cid 120 Show change in organisms through time cid 120 Change in types of organisms o Past organisms differ from present day organisms o Many species have become extinct cid 120 Not only provides evidence of small scale changes but of origin of major groups o EG The cetaceans o CHAPTER 23 The Evolution of Populations Clicker homology is least likely in legs of a bird and an insect The Smallest Unit of Evolution cid 120 One misconception about evolution is that individual organisms evolve during their lifetime cid 120 Evolutionary processing natural selection act on individuals but populations evolve cid 120 Concept 23 1 Genetic variation makes evolution possible o EG X MEN Mutation cid 120 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 cid 120 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 cid 120 Discrete characters classified on an either or basis o EG flower color in pea plants cid 120 Quantitative characters vary along a continuum within a population o EG height and weight Concept 23 2 The Hardy Wienberg equation can be used to test whether a population is evolving Populations o cid 120 Population a group of individuals of the same species living in a certain defined area Hardy Wienberg Equilibrium cid 120 H W equilibrium describes a population that is not evolving ie allele frequencies don t change cid 120 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 cid 120 P frequency of allele 1 q frequency of allele 2 cid 120 P Q 1 Genotype Frequencies cid 120 P2 frequency of homozygous dominant cid 120 Q2 frequency of homozygous recessive cid 120 2PQ frequency of heterozygotes cid 120 P2 2PQ Q2 1 H W equation H W Equilibrium Population Genetics And Human Health cid 120 H W equation can be used to estimate of the human population carrying the allele for an inherited disease cid 120 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 cid 198 q 0001 01 cid 198 P Q 1 cid 198 P 01 1 cid 198 P 99 P2 2pq q2 1 cid 198 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 cid 198 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 cid 120 Statistically the smaller a sample the greater the chance of deviation from a predicted result cid
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