Lecture 23: evolutionary process

Question 1

Mutation

Answer 1

Changes genetic codes which alter phenotypic response

ex. Drosphilia
- mutation decreased eyes, wings and overall fitness

Question 2

What do most mutations do?

Answer 2

decrease fitness (by about 2%) (considered deleterious)
- there are some beneficial mutations, but they are very rare (called, hopeful monsters)

Question 3

Genetic drift

Answer 3

• causes RANDOM changes in allele frequency
• is stronger in smaller populations
  • ex. D. Melanogaster (fruit flies)
• two neutral eye colours (wild type and bw75)
• allele frequencies basically spread out until it was about 50:50

Question 4

Natural Selection

Answer 4

• all organisms will grow exponentially, but yet most populations remain stable (implies high mortality rate in nature)
  • Prediction: traits that improve survival should increase in frequency over time
  ex. pigeons
• Daphne major drought caused birds to have a difficult time finding food since the vegetation wouldn’t grow
• changes in the drought included: seed size, abundance and hardness
• during the drought about 90% of finches died
• but the ones who survived had larger beaks (allowed them to eat the smaller, harder seeds)

Question 5

Sexual Selection

Answer 5

Comes in two forms:

1. Intrasexual- male-male competition or female-female competition
2. Intersexual- male vs. female (typically female choice)
   ex. widow birds:
   - had long tail that didn’t seem necessary for survival
   - when they cut it off, they then had poor sexual sucsess
   - therefore, the long tails returned since it favoured their sexual selection

Question 6

Gene Flow

Answer 6

• the interaction of genes moving among population
• tends to oppose natural selection
• causes allele frequencies in two populations to be more alike