Lecture 4

Question 1

What is Evolution?

Answer 1

The process that results in changes in the proportion of heritable traits within populations from one generation to another

Question 2

What is Natural Selection

Answer 2

The only evolutionary mechanism that leads to adaptions

Question 2

What are the four forces/mechanisms included in Evolution that drives changes?

Answer 2

• Natural selection
• Mutation
• Genetic Drift
• Gene Flow

Question 3

What are adaptions?

Answer 3

Traits that provide a “fit” between an organism and its environment

Question 4

What are Medium ground finches and their characteristics?

Answer 4

• One of two finch species living on Daphne island
• Have stubby beaks
• Primarily eat seeds

Question 5

What are medium ground finches with deeper beaks better at?

Answer 5

Better at eating large/hard seeds than finches with shallow beaks

Question 6

Who tracked finches?

Answer 6

Peter and Rosemary Grant tracked finches on Daphne Island since 1973

Question 7

What happened in 1976 on Daphne Island?

Answer 7

A major drought hit the island and the distribution of seeds changed over time (there was fewer small/soft seeds than large/hard seeds

Question 8

What did researchers establish in regards to the finch population?

Answer 8

Variation existed in the finch population (beak depth)

Beak depth is a heritable trait

Finches with deeper beaks were more likely to survive and reproduce

Question 9

What are Darwin’s 3 Postulates?

Answer 9

1. Phenotypic Variation Exists within a Population
2. Differential reproduction/survival occurs based on that phenotypic variation.
3. Variation is genetically heritable

Question 10

What does “Fitness” mean?

Answer 10

A term most often used by biologists to explain the evolutionary success of certain organisms.

Question 11

What is Fitness a measure of?

Answer 11

A measure of how many surviving offspring one produces.

Question 12

What are traits that increase reproduction?

Answer 12

Adaptive

Question 13

What is Directional Selection?

Answer 13

Distribution of a trait moves in a single direction
(Example with finches during the drought shows directional selection)

Question 14

What is Stabilizing Selection?

Answer 14

Genetic variants that lead to ‘extremes’
(e.g., deep beaks OR shallow beaks)
become less common in the population
over time
* This can happen when there are trade-offs

• Reduce/Maintain Variation

Question 15

What is Disruptive Selection?

Answer 15

• Genetic variants that lead to average beak depth become less common in the population over time – selection favours genetic variants that lead to the ‘extremes’
• This can happen when it is beneficial to be a specialist
• Favour more ‘extreme values’