Lecture 11 BIO 311D 2nd EditionOutline of Last Lecture I. ReviewII. Reproductive isolating mechanismsIII. What is a phylogeny?IV. Interpreting cladogramsOutline of Current Lecture I. MacroevolutionII. Data for Phylogenetic AnalysisIII. Human Evolution Current LectureI. Macroevolution (New species forming)A. Pre-zygotic barriers: impeded mating or hinder fertilization if mating does occur1. Habitat isolation2. Temporal isolation3. Behavioral isolation 4. Mechanical isolation5. Gametic isolationB. Post-zygotic barriers: prevent a hybrid zygote from developing into a viable, fertile adult1. Reduced Hybrid Viability2. Reduced Hybrid Fertility 3. Hybrid breakdownC. Hybrid ZoneThree Possible Outcomes:1. Reinforcement: hybrids die out;hybridization decreases; facilitatesseparation; evolution of pre-zygoticisolating mechanism (temporal, gametic,behavioral, etc.) 2. Fusion: broke down barriers, interbreedagain 3. StabilityPractice Problem: Evolutionary “reinforcement” refers to the natural selection of more pre-zygotic reproductive barriers. What is the result of reinforcement? Less parental energy will be invested in producing hybrids.II. Data for Phylogenetic analysisA. Phylogeny: a “family tree” that represents evolutionary history of a group. There is always a time line. When a lineage splits, it is represented as branching on a phylogeny. Each lineage has ancestors that are unique to that lineage and common ancestors that are shared with other lines. We build a phylogeny by comparing traits that are present or absent in the groups we’re studyingB. What structures are most useful for interpreting evolutionary history?- Homologous structures, derived from the same ancestral structuresEmbryo structures can be just as informative as adult structures, or even more so- All embryos have a post anal tail - Homologous genes from gene duplication events- Homologous: come from same ancestral gene C. Analogous structures:- Wing of insect, wing of a bat analogous structure (same function) - Convergent evolution: unrelated organisms look the same: old world and new world vultures; cactus and euphorbia, flight in reptiles, bats, birds - Prior to the origin of recent groups of mammals, the continent of Australia was isolated. Marsupial mammals evolving in Australia superficially resemble eutherian mammals that evolved elsewhere, even though each pair is closely relatedD. The globin gene family is the product of numerous gene duplications and mutations over evolutionary time - DNA sequence data, in a phylogeny of globin proteins (in the multi-gene family)- These genes in a multi-gene family are homologous, why? The genes are derived from the same ancestral geneE. A clade, also called a monophyletic group, is a grouping that includes a common ancestor andall the descendants (living and extinct) of that ancestorIII. Human EvolutionA. How can we apply phylogenetic analyses to the study of human evolution?Measure height traits, teeth, nuclear DNA sequences, traits, fossil records, DNA protein common, mitochondria DNA, embryos, etc. B. Evolution of Humans: - Human and chimpanzee genomes 99% similar- Karyotypes almost same- No significant difference in gene function- How can so few changes account for so much apparent difference? – Many new traits are not simply due to a new gene for a new structure. Many are due to changes in the control of gene expression (old genes, new control
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