1. Evolution Review
Chapters 22-24

2. History of Evolution? Hutton: gradualism Malthus: population studies
Lamarck: theory of acquired characteristics (crop a dog’s ears…)
Lyell: geological studies
Then came…. Darwin (and Wallace)

3. Darwin
Descent with modification: all organisms descended from common ancestors… but have experienced small changes
The history of life is like a tree, with each branch representing a lineage of some organism

5. Natural Selection
Natural selection is differential reproductive success
Natural selection occurs through an interaction between environment and organisms with genetic variations
The product of natural selection is adaptation of populations to environment

7. Artificial selection
Some outside force (humans) choose organisms with certain characteristics
Breeding animals for certain traits

9. Evidence of Evolution
Biogeography: geographical distribution of species
Fossil record: dating fossils, making comparisons
Comparative anatomy: homologous structures (bat wing, bird wing, human arm, whale flipper)

13. Continued….
Vestigial structures: no or reduced function (appendix) remains from earlier ancestor who did use it
Comparative embryology: many organisms go through similar stages of development pointing to common ancestor
Molecular biology: DNA evidence shows species relatedness

17. Population genetics
Emphasizes the extensive genetic variation within populations
Population: same species, same place… capable of reproducing
Gene pool: all the genes in a population

18. Hardy-Weinberg
Frequencies of alleles in a population remain constant over time
Meiosis and genetic recombination have no net effect on frequency of alleles

19. Conditions Large population No gene flow No mutations Random mating
No natural selection
Describes idealized populations to allow for the study of real populations

20. Genetic drift
Changes in gene pool of a small population due to random chance
Bottleneck effect: a disaster wipes out most of population unselectively… survivors have limited genetic diversity and population goes through bottleneck
Founder effect: small group colonizes new area, whole population is only as diverse as founders

22. Types of Selection Stabilizing: acts against extreme phenotypes
Directional: selects one extreme or other
Diversifying: selects both extremes
Sexual: choose mates based on characteristics like size, color, behavior, etc.

26. Natural Selection revisited
It cannot make perfect organisms
It can only work with what genetic diversity is present
Not all evolution is adaptive, meaning some evolution is truly pointless…

27. Reproductive isolation… keeps species distinct
Prezygotic:
Habitat isolation
Behavioral isolation
Temporal isolation
Mechanical isolation
Gametic isolation
Postzygotic:
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown – when the hybrid offspring mate, it does not work!

28. Speciation Speciation: the creation of a new species
Allopatric speciation: “other homeland” a geographical barrier physically isolates populations until they become new species
Sympatric speciation: new species emerge within a population due to chromosomal changes or nonrandom mating

29. Models of evolutionary change
Gradualism: evolution is the result of tiny changes accumulating over long periods of time (see intermediate species)
Punctuated equilibrium: evolution occurs rapidly with big changes (no intermediate species seen)