chem 160.1

• SALTATORY EVOLUTION - “Evolution occurred in rapid leaps as a result of radical phenotypic changes caused by mutations”
• Saltation - Phenotypic gaps in clusters of speciesL. Extinction of intermediate forms that once existed.
• Population genetics - It recognized the importance of quantitative inheritance. It reconciled Darwinism and Mendelism.
• Contributors of Modern Evolutionary Synthesis Theory:

  1. Dobzhansky (gen)
  2. Mayr (biogeo and taxo)
  3. Simpson (paleo)
  4. Stebbins (bot)
• Modern Synthesis Theory points:

  1. Mendel's inheritance
  2. populations
  3. natural selection
  4. gradualism
• Population - localized groups of organisms which belong to the same species
• Gene pool - the total aggregate of genes in a population at any one time. consists of all the alleles at all gene loci in all individuals of a population.
• Diploid has 2 copies of alleles
• Species - group of actually or potentially interbreeding individuals, which are reproductively isolated from other such groups.
• Allele frequency – the relative proportion of an allele (in a given locus) in a population.
• Genotypic frequency – the proportion of individuals bearing a given genotype (at a locus) in a population.
• microevolution - evolution that occurs at or below the level of species. includes such as a change in the gene frequencies of a population of organisms. process by which new species are created (speciation)
• Because microevolution can be observed directly, it is widely accepted (unlike macroevolution ~ garnered controversies)
• Hardy Weinberg Theorem - The frequencies of alleles in the gene pool will remain constant unless acted upon by some forces.
• Proponents ng Hardy Weinberg:

  • Hardy(math prof)
  • weiberg (german physician)
• Hardy-Weinberg principle describes a mathematical relationship between allele frequencies and genotype frequencies and allows the prediction of a population’s genotype frequencies from its allele frequencies.
• “In a large, randomly mating population, the allele frequencies p and q (for alleles A and a) will attain in one generation the frequencies p2, 2pq, and q2 for the three genotypes (AA, Aa, and aa), regardless of the initial genetic constitution, and will remain in these proportions in the absence of selection, mutation, and migration.”
• Population Genetics - the branch of biology that provides the mathematical structure for the study of the process of microevolution.
• The Hardy-Weinberg model... 29 • Describes the genetics of an ideal, NON- EVOLVING population
• • Genotype frequencies attain their H-W values after a single generation of random mating.
• assumpions ng H-W

  • random mating
  • The population is infinitely large
  • No gene flow (no outside genes)
  • no mutation
  • no natural selection (all equal reproduction and survival)
• non-adaptive are called non-Darwinian changes.
• Genetic drift

  • change in the gene pool of a small population due to chance
• • Genetic drift is a random process that can be important in the evolution of some populations.
• Genetic drift is the consequence of finite population size.
• genetic drift is not responsible for adaptation
• Genetic Drift • Sampling error can happen
• The larger the population, the less important is the effect of genetic drift.
• Causes of genetic drift:

  • bottleneck effect
  • founder effect
• Bottleneck effect - Genetic drift which results from drastic reduction in population size due to natural disasters
• Bottleneck Effect

  • The small surviving population is unlikely to represent the genetic make up of the original population.
• The bottleneck effect reduces the over-all genetic variability

  in a population since some alleles may be:

  1. under-represented
  2. over-represented
  3. totally absent
• Founder effect - Occurs when a few individuals colonize a new habitat. Genetic drift in a new colony.
• Founder effect - The smaller the founding population, the less likely its gene pool will be representative of the original population’s genetic make-up.
• The loss of genetic variation due to such an extreme bottleneck is called the founder effect
• Gene flow or Migration - the movement of fertile individuals between populations. the transfer of gametes (and the alleles they carry) between populations
• Gene flow tends to reduce the differences between populations because members of each population can inter breed and genes are essentially shared or transferred between the two populations.
• Mutation • change in the genetic material
• point mutation (base substitution, frameshift)
• change in chromosome structure (deletion, duplication, inversion, translocation)