Lecture 4 Flashcards
What is Evolution?
The process that results in changes in the proportion of heritable traits within populations from one generation to another
What is Natural Selection
The only evolutionary mechanism that leads to adaptions
What are the four forces/mechanisms included in Evolution that drives changes?
- Natural selection
- Mutation
- Genetic Drift
- Gene Flow
What are adaptions?
Traits that provide a “fit” between an organism and its environment
What are Medium ground finches and their characteristics?
- One of two finch species living on Daphne island
- Have stubby beaks
- Primarily eat seeds
What are medium ground finches with deeper beaks better at?
Better at eating large/hard seeds than finches with shallow beaks
Who tracked finches?
Peter and Rosemary Grant tracked finches on Daphne Island since 1973
What happened in 1976 on Daphne Island?
A major drought hit the island and the distribution of seeds changed over time (there was fewer small/soft seeds than large/hard seeds
What did researchers establish in regards to the finch population?
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
What are Darwin’s 3 Postulates?
- Phenotypic Variation Exists within a Population
- Differential reproduction/survival occurs based on that phenotypic variation.
- Variation is genetically heritable
What does “Fitness” mean?
A term most often used by biologists to explain the evolutionary success of certain organisms.
What is Fitness a measure of?
A measure of how many surviving offspring one produces.
What are traits that increase reproduction?
Adaptive
What is Directional Selection?
Distribution of a trait moves in a single direction
(Example with finches during the drought shows directional selection)
What is Stabilizing Selection?
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