1. Developmental Biology and Evolution 佟超 浙江大学生命科学研究院

2. Outline Overview Preconditions for evolution Deep homology Mechanisms of evolutionary changes Developmental constrains on evolution Selectable epigenetic variation Summary

3. What is Evolution ?

4. Evolution is the change in the inherited characteristics of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organization, including species, individual organisms and molecules such as DNA and proteins.

5. Descent from a common ancestor Natural selection At the different level What is Evolution ?

6. Timeline of evolution theory 1735 biological classification 1809 Lamarckism 1858 0n the origin of species 1865 Mendel's laws 1896 Weismannism “germ cells vs Somatic cells” population genetics 1953 DNA structure

7. Galapagos

8. Summary of Darwin’s theory Every species is fertile enough that if all offspring survived to reproduce the population would grow (fact). Despite periodic fluctuations, populations remain roughly the same size (fact). Resources such as food are limited and are relatively stable over time (fact). A struggle for survival ensues (inference). Individuals in a population vary significantly from one another (fact). Much of this variation is inheritable (fact). Individuals less suited to the environment are less likely to survive and less likely to reproduce; individuals more suited to the environment are more likely to survive and more likely to reproduce and leave their inheritable traits to future generations, which produces the process of natural selection (inference). This slowly effected process results in populations changing to adapt to their environments, and ultimately, these variations accumulate over time to form new species (inference). Ernst Mayr

9. Why we need to understand evolution? "nothing in biology makes sense except in the light of evolution" Theodosius Dobzhansky

10. Basics of Biology Theory of evolution Mendelian inheritance The central dogma of molecular biology

11. How “far” away they are

12. How “close” they are

13. How does evolution work Preconditions for evolution: The developmental structure of genome Modularity Molecular parsimony The small tool kit

14. Modularity: Divergence through dissociation

15. Apterous

16. Molecular parsimony: gene duplication and divergence Some “tool kit” genes play the same roles in all animals Gene duplication provides opportunities for divergence. Paralogues Orthologues

17. Molecular parsimony: gene duplication and divergence

18. Deep Homology

19. Mechanisms of evolutionary change Evolution works with what it has: Change in location (Heterotopy) Change in time (Heterchrony) Change in amount (Heterometry) Change in kind (Heterotypy)

20. Heterotopy Fgf8 BMP apoptosis

21. Heterotopy Fgf10 attract ribs to enter the dermis BMP induce the bone formation

22. Heterchrony

23. Heterometry Darwin’s finches

24. Heterometry

25. Heterotypy Why insects have only six legs?

26. Developmental constraints on Evolution Physical constraints Morphogenetic constraints Phyletic constraints

27. Physical constraints

28. Morphogenetic constraints

29. Phyletic constraints

30. Selectable epigenetic variation: Environment cues Somatic cells VS germ cells What is wrong with lamarck? Epialleles Symbiont variation Genetic assimilation

31. Epialleles

32. Symbiont variation Interaction with an expected population of symbionts could result in phenotypic plasticity. When symbionts are transmitted through the germ line, the symbionts provide a second system of inheritance.

33. Symbiont variation

34. Genetic assimilation The environment could both “induce” and “select” a phenotype. Genetic assimilation happens both in labs and in nature. Fixation of environment induced phenotypes 1. The phenotype is not random. 2. The phenotype already exists in a large portion of population

35. Summary Variation-modularity, molecular parsimony, and duplication- enable changes in development without destroy the organism. Four modes of genetic changes act during development to produce new and large variation in morphology. Epigenetic inheritance provide selectable variations and aid their propagation through a population.