Bio. 230 --- Evolution III

1. Bio. 230 --- Evolution III

2. Some History of Evolutionary Thought Empedocles (Greek, ~490 to 430 B.C.) 1st to propose a clear concept of biological evolution Abiogenesis Plants arose 1st; their buds gave rise to animals Gradual process

3. Some History of Evolutionary Thought Aristotle (Greek, 384-348 B.C.), student of Plato (~427-347 B.C.) Similar ideas Abiogenesis Acquired characteristics Species could hybridize

4. Some History of Evolutionary Thought Lamarck (French, 1744-1829) 1st in more modern times to put forth a comprehensive & logical evolutionary theory Acquired characteristics Pangenesis / pangenes Newer forms were more complex (and “perfect”) than their ancestors

5. Some History of Evolutionary Thought Charles Darwin (English, 1809-1882) Started out as a special creationist READ handout: “A comparison of views on variation and heredity” 1831-1836 --- voyage on the Beagle Then worked for more than 20 years 1838 – He read AN ESSAY ON THE PRINCIPLE OF POPULATION by Thomas Malthus Natural Selection

6. Some History of Evolutionary Thought Charles Darwin (English, 1809-1882) 1844 -- Put together a brief essay (unpublished) Early 1858 – Essay from Alfred Russel Wallace Later 1858 – Published Wallace’s essay and excerpts from his own 1844 essay in the Journal of the Linnaean Society 1859 – published THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION

7. Darwin’s Main Points Overproduction of offspring Variation within a species and at least some of it is hereditary Limits on resources; engenders a strugglefor existence Generally the fittest survive(= Natural Selection) Eliminating of unfavorable traits and accumulation of more favorable traitsgives rise to new forms of life

8. NeoDarwinism or The Modern Synthetic Theory Darwin did not have all the answers 1937 – Theodosius Dobzhansky (Genetics and the Origin of Species) began the MST 1950s to 1970s additional seminal workC. Leo Babcock (plant evolution),Edgar Anderson (Introgressive Hybridization),EarnstMayr (animal evolution),G. L. Stebbins (plant evolution),J. Watson & F. Crick (DNA structure), M. Nirenberg & J. H. Matthaei (genetic code)

9. Evolutionary Potpourri Evolution occurs in POPULATIONS* Populations can have a change in gene / allele frequency All populations are phenotypically polymorphic New gene / allele combinations can come about from CROSSINGOVER and RECOMBINATION during sexual reproduction New alleles / genes come about by some type of MUTATION Microevolution* vs. Macroevolution* Are the processes that drive each different? Gradualism vs. Punctuated Equilibrium* Are the processes that drive each different?

10. The Gene Pool (I) DEFINITION* -- ALL of the genes AND alleles in a population taking into account their frequency It is the total supply of genetic units available to form the next generation Not possible to study the whole gene pool Will look at a “mini” gene pool (for the gene “A”) Only two alleles: A and a 3 possible genotypes (AA, Aa, aa) We start a population with a certain frequency of A and a

11. The Gene Pool (II) What will happen to the allele (and genotype) frequencies over the generations?????????? Solved independently in early 20th century by: George Hardy & Wilhelm Weinberg Known by various aliases: Hardy-Weinberg Equilibrium Hardy-Weinberg Theorem Hardy-Weinberg Law

12. Hardy-Weinberg Equilibrium DEFINITION* -- Given certain conditions the allele frequencies remain constant from generation to generation AND after one generation of random mating even the genotype frequencies will remain constant and can be predicted from the equation (p + q)2 = p2 + 2pq + q2 p = the frequency (f) of A q = the frequency (f) of ap2 = f AA, 2pq = f Aa, q2 = faa

13. Hardy-Weinberg Conditions (I) Infinitely large PopulationEliminates chance fluctuations (genetic drift) Random MatingMeans no inbreeding; no positive (+) or negative (-) assortative mating No net mutationEliminates mutation pressure No net population movementEliminates net gene flow

14. Hardy-Weinberg Conditions (II) No natural selectionMeans no type is better than another; all types must survive at proportional rates ----------------------------------------------------------------- “Survival of the Fittest” does not mean that organisms fight or that organism have to die Death (real) vs. Genetic Death Natural Selection works on PHENOTYPE

15. Genetic Drift • A change in the allele frequencies in a gene pool due to random (chance) events • More likely to happen in small populations OR when a small sample is taken from a large population • Due to random sampling in a less than infinite population

16. Genetic Drift

17. Genetic Drift / Bottlenecking / Founder Effect

18. Some Species Concepts • Many concepts; none are ‘perfect’ • Morphospecies(= typological sp.) • Biological species (= reproductive sp.) (E. Mayr) • Phenetic species • Ecospecies • Phylogenetic species

19. Phyletic Speciation (Anagenesis) Number of extant species does not increase

20. Divergent Speciation (Dichotomous speciation or Cladogenesis) Number of extant species increases

21. Isolating Mechanisms • See handout

22. Autopolyploidy (Fig. 24.10) ???????????

23. Allopolyploidy (Fig. 24.11) ???????????

24. Allopolyploidy (MOST likely)(2 pathways --- many examples)(Primulakewensisand Tragopogonmirus)