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An Introduction to Evolution

An Introduction to Evolution. Dr. Chrisantha Fernando Systems Biology Centre University of Birmingham. What does Evolution explain?. To explain how different animals and plants have become adapted to different environmental conditions over many generations.

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An Introduction to Evolution

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  1. An Introduction to Evolution Dr. Chrisantha Fernando Systems Biology Centre University of Birmingham

  2. What does Evolution explain? • To explain how different animals and plants have become adapted to different environmental conditions over many generations. • Evolution is the process by which living things become adapted to their environment over many generations.

  3. What is Evolution? • Evolution occurs in populations of agents some of which produce offspring. The 'fitter' ones tend to produce more. • Over many generations, the make-up of the population changes without the need for any individual to change. Over successive generations, the 'species' changes, in some sense adapts to the conditions.

  4. Open country, ran from predators. One toe The Horse Muscles tend to be found at the upper part of the leg, later on. Lower part is less heavy. Easier acceleration and deceleration -> less energy on galloping.

  5. Karl Sims’ Artificial Evolution • Evolved virtual body plans in a simulated physical environment • Used artificial evolution in the computer • Show video.

  6. Evidence for Evolution • Selective breeding for phenotypic traits, e.g. cows for milk, chickens for eggs, dogs for friendliness, mice for better teeth. • Similarities between different species allows inference of an evolutionary tree. • Moths in Birmingham during the Industrial Revolution.

  7. Breeding

  8. Homology

  9. Moths in Birmingham 1996 1956

  10. Evolution by Natural Selection • Natural selection is an algorithm that works iff… • Multiplication. Entities should give rise to more entities of the same kind. • Like begets like: A type entities produce A type entities, B type entities produce B type entities, and so on. • Variability. Heredity is not exact; occasionally A type objects give rise to A' type objects. Undirected. • Entities of different types have a hereditary difference in their survival. Directed.

  11. ‘Natural’ Selection of Paper Gliders • 1.Generate 20 random sequences of folding instructions • 2.Fold each piece of paper according to instructions written on them. • 3.Throw them all out of the window • 4.Pick up the ones that went furthest, look at the instrns. • 5.Produce 20 new pieces of paper, writing on each bits of sequences from parent pieces of paper. • 6.Repeat from (2) on. • This is Inman Harvey’s example.

  12. Fold TL to BR towards you Fold horiz middle away Fold vertical middle towards Fold TR to BL towards you Fold horiz middle away Fold vertical middle away I. Harvey.

  13. Evolving Tables Hornby et al

  14. Natural Selection in the Lab • Sol Spiegelman’s experiment with Q-beta replicase enzyme. R R R RNA RNA RNA

  15. Serial Dilution, like with homeopathy

  16. Natural Selection in the CPU • Tierra (Tom Ray) and Avida. Red Starting Set Parasites Yellow Immune Hosts “Organisms compete for CPU time to replicate”. “A reaper randomly removes organisms”.

  17. An example Tierran Organism nop_1 ; 01 47 copy loop template COPY LOOP OF 80AAA nop_0 ; 00 48 copy loop template nop_1 ; 01 49 copy loop template nop_0 ; 00 50 copy loop template mov_iab ; 1a 51 move contents of [bx] to [ax] (copy instruction) dec_c ; 0a 52 decrement cx if_cz ; 05 53 if cx = 0 perform next instruction, otherwise skip it jmp ; 14 54 jump to template below (copy procedure exit) nop_0 ; 00 55 copy procedure exit compliment nop_1 ; 01 56 copy procedure exit compliment nop_0 ; 00 57 copy procedure exit compliment nop_0 ; 00 58 copy procedure exit compliment inc_a ; 08 59 increment ax (point to next instruction of daughter) inc_b ; 09 60 increment bx (point to next instruction of mother) jmp ; 14 61 jump to template below (copy loop) nop_0 ; 00 62 copy loop compliment nop_1 ; 01 63 copy loop compliment nop_0 ; 00 64 copy loop compliment nop_1 ; 01 65 copy loop compliment (10 instructions executed per loop)

  18. Evolutionary Dynamics in Tierra. • Smaller self-replicating mutants require less CPU time (energy/resource), so replicate faster. • Parasites appeared 45 instructions long, able to use the code of their neighbors. • Hyperparasites appear that are even smaller and faster at replicating.

  19. Natural Selection as movement over a fitness landscape. F Random Smooth

  20. Neutrality. ’Constant innovation’ -- You never get stuck !

  21. Examples of Neutrality of GP Map. • RNA Sequence --> RNA Structure. • Evolvable Hardware.

  22. William Paley and the Eye • People said evolution could not produce the eye by small improvements, but it can. • Computer experiments helped confirm this. • “To suppose that the eye… could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree,” (Darwin, The Origin of Species).

  23. Nilsson’s Computer Simulation

  24. The New Eye

  25. The Origin of Life • Chicken and Eggs, Catch 22’s and the Oroboros. • How did natural selection start without genes that could undergo natural selection in the first place? • How did the molecules that made genes come about in the first place?

  26. What was the first Self-Replicating Thing?

  27. The Major Transitions in Evolution (JMS & ES 1995) 1. Replicating molecules to Populations of molecules in compartments 2. Independent replicators (probably RNA) to Chromosomes 3. RNA as both genes and enzymes to DNA as genes, proteins as enzymes Prokaryotes to Eukaryotes 5. Asexualclones to sexualpopulations—evolution of sex 6. Protists to multicellular organisms—animals, plantsfungievolution of multicellularity 7. Solitary individuals to colonies with non-reproductive castes 8. Primate societies to Human societies with language, enabling memes Ammalgamation: e.g. Chromosomes, eukaryotes, sex multicellular colonies. Specialization: e.g. DNA & protein, organelles, anisogamy, tissues, castes Obligate Symbiosis: e.g. Organelles, tissues, castes Conflict Mediation: Meiotic drive (selfish non-Mendelian genes), parthenogenesis, cancers, coup d’état New Information Transmission Techniques. DNA-protein, cell heredity, epigenesis, universal grammar.

  28. What is Life? (Tibor Ganti,1971) • If you went to Mars and found a pink fluffy object, how would you work out if it was alive? • Boundary • Metabolism • Informational Control System • E.g. single cell, multi-cellular organism. Is a country alive?

  29. Problems in Evolution. • How could sex evolve? Why only two sexes not three or four? • How do new species come about? • How does the genotype-phenotype map evolve, i.e. the evolution of evolvability. • Can there be selection of groups or ecosystems in the wild? Chicken coops.

  30. Thanks to • Inman Harvey • Jon Rowe • All sources used for Images from the Internet. • QUESTIONS AND DISCUSSION if you like.

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