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  1. 1. Emma Rodelius
  2. 2. • Evolutionary developmental biology• Compares the development of different organisms to try to understand ancestral relationships between them and the developmental mechanisms that cause evolutionary change• Involves the discovery of genes that control development
  3. 3. • Genetic changes, also called genetic innovations, cause structural changes in organisms • Advantageous innovations can result in species development• Proteins control developmental changes • Promote morphological changes during evolution
  4. 4. • Genes that play a role in development may influence cell division, cell migration, cell differentiation, and cell death• Interaction among these 4 processes produces an organism with a specific body pattern, or a pattern formation• Developmental genes play a key role in the evolution of certain traits and affect and organisms phenotype• Variation in their expression can result in new traits that promote speciation
  5. 5. • Chicken foot & Duck foot Comparison • Due to differences in expression of 2 cell-signaling proteins • BMP4: causes cells to undergo apoptosis and die • Gremlin: inhibits the function of BMP4 and allows cell to survive
  6. 6. • Mutations on the expression of BMP4 and gremlin provided variation• Terrestrial settings: nonwebbed feet are an advantage • Enable individual to hold onto perches, run easily, catch prey • Natural selection favors nonwebbed feet• Aquatic environments: webbed feet are an advantage • Act as paddles for swimming • Natural selection favors webbed feet
  7. 7. • Found in all animals• Variation in the Hox genes may have spawned the formation of many new body plans• Number and arrangement of Hox genes varies among different types of animals• Increases in the number of Hox genes may have led to greater complexity in body structure
  8. 8. • Encode transcription factors that act as ‘master control’ proteins which direct the formation of certain body regions• Each Hox gene controls a group of regulatory genes, which in turn regulate the expression genes that ultimately affect an organism’s morphology• Different Hox genes are expressed at different regions along anteroposterior axis
  9. 9. • Three lines of evidence support the idea that Hox gene complexity has contributed to the evolution and speciation of animals with different body patterns:1. Hox genes control the fate of regions along the anteroposterior axis2. Organisms with more Hox genes and Hox clusters tend to have greater body complexity3. Hox gene evolution and animal evolution bear striking parallels
  10. 10. • Genetic variation can influence morphology by controlling the relative growth rates of different parts of the body during development• Heterochrony: evolutionary changes in the rate or timing of developmental events • Compare growth of head between human and chimpanzee• Paedomorphosis: sexually mature organism retains traits typical of the juvenile stage of the organism’s ancestor
  11. 11. • Explaining how a complex organ comes into existence is a major challenge• Researchers have discovered many different types of eyes• Thought that eyes may have independently arisen many different times during evolution• Pax6 is a master control gene that controls the expression of many other genes and influences eye development • Present in rodents and humans• Eyeless gene is found in Drosophila, fruit flies, and induces eye development
  12. 12. • Eyes of Drosophila and mammals are evolutionarily derived from a modification of an eye that arose once during evolution• If Drosophila and mammalian eyes had arisen independently, the Pax6 gene from mice would not be expected to induce the formation of eyes in Drosophila• Recall: Darwin hypothesized that the eyes from many different species all evolved from a common ancestral form consisting of one photoreceptor cell and one pigment cell• Over time, simple eyes evolved into complex eyes by modifications that resulted in additional cell types • Lens cells, muscle cells• Others argue that Pax6 only controls eye development up to a certain extent and that different types of eyes evolved independently