1. Bio 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, B.C.), student of Plato (~ B.C.)
Similar ideas
Abiogenesis
Acquired characteristics
Species could hybridize

4. Some History of Evolutionary Thought
Lamarck (French, )
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, )
Started out as a special creationist
READ handout: “A comparison of views on variation and heredity”
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, )
Put together a brief essay (unpublished)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 struggle for existence
Generally the fittest survive (= Natural Selection)
Eliminating of unfavorable traits and accumulation of more favorable traits gives 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 work C. Leo Babcock (plant evolution), Edgar Anderson (Introgressive Hybridization), Earnst Mayr (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*

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 = p pq + q2
p = the frequency (f) of A q = the frequency (f) of a p2 = f AA, 2pq = f Aa, q2 = f aa

13. Hardy-Weinberg Conditions (I)
Infinitely large Population Eliminates chance fluctuations (genetic drift)
Random Mating Means no inbreeding; no positive (+) or negative (-) assortative mating
No net mutation Eliminates mutation pressure
No net population movement Eliminates net gene flow

14. Hardy-Weinberg Conditions (II)
No natural selection Means 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. Many concepts; none are ‘perfect’ Morphospecies (= typological sp.)
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 ) ???????????

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

24. Allopolyploidy (MOST likely) (2 pathways --- many examples) (Primula kewensis and Tragopogon mirus)