Evolution

Chapters 15 - 17

Evolution is both Factual and the basis of broader theory

• What does this mean?

• What are some factual examples of evolution?

• What are some problems we apply evolutionary theory to solve?

15

Charles Darwin• He wasn’t the first to suggest

organisms change, so what was the major contribution?

• How did the work of other scientists influence him? – Lamarck? Lyell? Wallace?

• What were the “holes” in Darwin’s theory? Who helped fill these?

15

Mechanisms of Evolution

• Starts with variation in the population– How is variation established in a gene

pool?

• Selection– Artificial vs. Natural?– What effect does this have on

variation?

• Gene flow– How does it affect allele frequencies

in a population?

15

• Genetic drift– Do populations always evolve for the

better?

– What is a population bottleneck and how does this lead to the evolution of a population?

– How does the Founder effect relate to the effect of a bottleneck?

15

Mechanisms of Evolution

• Sexual Selection– Examples?

– Often explains characteristics that seem to have no adaptive value but stick in the population.

15

Measuring Allele Frequencies

• What is the significance of changing allele frequencies?

• What is the relationship between allele and genotypic frequencies?

15

Measuring Allele Frequencies

If p equals the frequency of the dominant allele (A) and q equals the frequency of the recessive allele (a), then:

1. p + q must equal 1. 2. P2 = frequency of homozygous dom. (AA)3. 2pq = frequency of heterozygous (Aa)4. q2 = frequency of homozygous rec. (aa)

Why? Know how this is derived using probability!

15

Hardy Weinberg Equilibrium

Populations only maintain genetic equilibrium under certain conditions. What are the five requirements for H-W Equilibrium?

15

Modes of Selection

- How do they differ?

- When might each occur in a population?

- Know examples!

15

Molecular Evolution• Why don’t all changes in DNA lead

to a change in protein?

• How does the rate of mutation compare between silent sites, missense sites and pseudogenes? Why is this significant?

• What are the conditions for positive and purifying selection?

15

Heterozygote advantage maintains polymorphic loci

• How does this help explain why deleterious mutations may stay in a population?

• Examples: cystic fibrosis or sickle cell anemia

15

Promoting Genomic Changes• What are the disadvantages of sexual

reproduction?

• So how did it manage to evolve?

• Examples of lateral gene transfer?

• What are the various outcomes of gene duplication?

15

Practical applications of Evo. Theory• How is it used for studying protein

function?

• In vitro evolution- how and why?

15

Practical applications of Evo. Theory• Agricultural

benefits?

• Assistance in studying human disease?

15

Phylogenetic Trees16

What can they tell us?

- nodes?

- lineage?

Be careful – lots of similar words. Know the nuances of their meaning!!!

Evidence for evolutionary relationships

16

• Homologous traits resulting from divergent evolution?

• Are all similar traits evidence of relatedness?

Building phylogenies16

• What sources of data can be used to build phylogenies?

• Do any have benefits over others?

• Can we test the accuracy of molecular methods?

Phylogenies compare, but can they also predict?

16

• What practical applications does constructing phylogenies have?

• How does the molecular clock assist in mapping evolutionary events?

Phylogeny as the basis for classification

16

• Remember your classification scheme!

• How has the Linnaean system been changed over the years?