9: Intro to evolution Flashcards
What are the main forms of evidence for selection powering change?
Natural selection is evidenced by…
1) Artifical selection (e.g. plant breeding).
2) Observation of nat. selec in action (e.g. rabbit tolerance to 1080 and calici virus).
3) Biogeography (e.g. comparing fauna of islands)
4) The fossil record + chronological sequencing
5) Comparitive anatomy (homology and analogy).
6) Molecular biology and genetics (the best evidence).
- -> E.g. comparing genome of mice and fruit fly.
What is evolution?
Evolution of the change in genetic composition of popiulations over time.
What were some of the main historical developments in the study of evolution?
1700s: Linnaeus (1707-1778) invents taxonomy
George Cuvier (1769-1862) describes succession of fossil species and derives the first theory of extinction.
James Hutton (1726-1797) Gradualism + theory of the Earth
Charles Lyell (1797-1875) uniformitarianism.
1809: Lamark’s theory of evolution
1831-1836: voyage of the beagle.
1844: Darwin’s unpublished essay on origin of species
1858: Alfred Russel Wallace proposes theory of nat. selec.
1859: Darwin published “on the origin of natural selection”
What are Russels three prepositions?
Russel’s Three major prepositions are that…
1) Species are not immutable: they change over time.
2) Divergent species share a common ancestor and have diverged from one another gradually.
- -> Descent with modification.
3) Nat. selec. explains changes in species over time: increases survival and reproductive success of some individuals based off differences in traits.
What is the origin of genetic variation?
Genetic variation is caused by mutation.
What is population genetics?
Population genetics is the study of allele frequency in a gene pool.
What is the gene frequency?
The gene frequency describes the proportion of alleles in a population.
At what level does evolution occur?
Evolution occurs at the population level as a result of selection on individuals.
What is gene flow and what is its effect?
Gene flow describes movement of alleles between populations.
- Reduces differences between populations
- Potential accumulated as a result of adaptation/genetic drift.
- changes allele frequency and may prevent evolution.
It’s like having a sand timer that’s half full on each side bc its lying on its side, then you tilt it up, reconnect populations, and then they merge to become more like one entity again.
What’s the hardy-weinberg theorem?
The hardy-weinburg theorem describes how a population in equilibrium will not experience any changes in allele frequency over time thus is non-evolving, unless acted on by an outside force.
Sort of Newton’s First Law of Biology. An object at rest will remain at rest unless acted on by an external force.
- in a non-evolving population, shuffling of genes due to recombination + segregation have no effect.
1 = proportion of AA + proportion of Aa + proportion of aa = p^2 + 2pq + q^2
What are the assumptions of the Hardy-Weinburg theorem?
The hardy-weinburg theorem has 5 assumptions…
1) Large pop. size (reduces effect of genetic drift)
2) No net gene flow
3) No net mutation
4) Random mating
5) No nat. selection.
