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Darwin: “embryology is to me by far the strongest

Developmental Biology Influence in Evolutionary Biology. 1860. Darwin: “embryology is to me by far the strongest single class of facts in favor of a change of forms”. 1900. Rise of experimental embryology vs genetics. Development shown to depend upon gene expression. 2000.

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Darwin: “embryology is to me by far the strongest

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  1. Developmental Biology Influence in Evolutionary Biology 1860 Darwin: “embryology is to me by far the strongest single class of facts in favor of a change of forms”. 1900 Rise of experimental embryology vs genetics Development shown to depend upon gene expression 2000 Molecular approaches allow study of developmental mechanisms within comparative evolutionary context

  2. Ontogeny recapitulates phylogeny How to Make an Organism Agnathan Fish Amphibian Reptile 0 325 500 600 Millions Years Ago

  3. Haeckel: Development is a guide to understanding Evolution - Descendants pass through the developmental stages of their ancestors - New stages are added on to the end of ontogeny - Earlier stages are condensed or lost over time

  4. Bad Theory Can Kill: Case of the Emperor Penguin (Robert Scott’s Expedition to South Pole)

  5. Karl Ernst von Baer’s Law Features common to a group of related taxa often appear in development before the specific characters of the more recently evolved taxa of the group.

  6. Heterochrony: Dissociation of the relative timing of events in development between ancestral and descendant ontogenies.

  7. Heterochronies can be defined at all levels Global Heterochronies: At the level of the organism - Classical heterochrony relating development of somatic tissue to germ tissue Local Heterochronies: At the level of individual traits - Isometric Growth - Allometric Growth - Molecular heterochronies

  8. Two general types of Heterochrony: 1) Paedomorphosis 2) Peramorphosis

  9. Paedomorphosis Peramorphosis A D A D progenesis hypermorphosis D A Somatic acceleration neoteny A D A D D A post-displacement predisplacement Reproductive

  10. Peramorphosis: Developmental extension/elaboration of the adult stage of the ancestral species, in the descendant.

  11. Allometry of skull and brain

  12. Paedomorphosis: Expression of juvenile, ancestral features in the adult stage of a descendent species.

  13. Richard Goldschmidt (1878-1958) Macromutational Hypothesis A. mexicanum

  14. Questions Do alternate life cycle modes evolve via genetic changes in developmental timing? 2. What is the relationship between discrete and continuous variation in developmental timing?

  15. Evolution of developmental timing: metamorphosis vs paedomorphosis Hatching Metamorphosis Time Paedomorphosis

  16. Interspecific crosses using A. t. tigrinum and A. mexicanum

  17. 1.00 0.75 0.50 0.25 0.00 metamorph paedomorph 571 Proportion 82 73 57 Lab Strain Wild Strain

  18. Segregation of contig325 genotypes • Cross TypeLCM Het Hom • Lab Met 52 5 • Paed 2 39 • Wild 1 Met 60 35 • Paed 1 16 • Wild 2 Met 219 196 • Paed 1 41

  19. Continuous variation in metamorphic timing Wild 2 Cross

  20. contig325 contributes to continuous variation Wild 2 Cross

  21. Contig325: also contributes to continuous variation. Hatching Metamorphosis Time Paedomorphosis

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