Lecture 11 BIO 311D 2nd Edition Outline of Last Lecture I Review II Reproductive isolating mechanisms III What is a phylogeny IV Interpreting cladograms Outline of Current Lecture I Macroevolution II Data for Phylogenetic Analysis III Human Evolution Current Lecture I Macroevolution New species forming A Pre zygotic barriers impeded mating or hinder fertilization if mating does occur 1 Habitat isolation 2 Temporal isolation 3 Behavioral isolation 4 Mechanical isolation 5 Gametic isolation B Post zygotic barriers prevent a hybrid zygote from developing into a viable fertile adult 1 Reduced Hybrid Viability 2 Reduced Hybrid Fertility 3 Hybrid breakdown C Hybrid Zone Three Possible Outcomes 1 Reinforcement hybrids die out hybridization decreases facilitates separation evolution of pre zygotic isolating mechanism temporal gametic behavioral etc 2 Fusion broke down barriers interbreed again 3 Stability Practice 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 analysis A 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 studying B What structures are most useful for interpreting evolutionary history Homologous structures derived from the same ancestral structures Embryo 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 related D 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 gene E A clade also called a monophyletic group is a grouping that includes a common ancestor and all the descendants living and extinct of that ancestor III Human Evolution A 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 patterns
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