Lecture 3 Flashcards
(29 cards)
Natural selection consists of:
- Phenotypic selection
- Selection gradient
- Genetic response
Which type of individual does better in terms of fitness in Stabilizing selection
The average individual with intermediate trait size
What happens to the mean trait “size from one generation to the next in stabilizing selection?
The mean does not change
What happens to the variation around the mean trait size from one generation to the next in Stabilizing selection?
Decreases: less fitness on either side of the curve
What are some examples of stabilizing selection?
Bird clutch size
Mice coat color
Describe which ‘type’ of individual does better in terms of fitness in Directional selection?
Extreme phenotype, small trait size
What happens to the mean trait ‘size’ from one generation to the next in Directional selection?
It will move to the left, it moves in the direction of the highest fitness
What happens to the variation around the mean trait size from one generation to the next in Directional selection?
It decreases
Think of some examples where directional selection may occur?e
Beak Size
Antibiotic resistance
Describe which ‘type’ of individual does better in terms of fitness?Describe which ‘type’ of individual does better in terms of fitness in Disruptive selection?
Extreme phenotypes in both sides, big or small
What happens tp the mean trait “size” from one generation to the next in Disruptive selection?
It has a bimodal distribution
What happens to the variation around the mean trait size from one generation to the next in Disruptive selection?
It increases
Examples of disruptive selection
Male salmon size: large ones are strong, small ones are sneaky
When does frequency dependent selection occurs?
When the fitness of an individual depends on the relative frequency of other phenotypes in the population
How is the fitness in negative frequency dependent selection?
The fitness of a phenotype decreases a becomes less common, unique
In the example shown in lecture, what mode of selection is acting on swallow body mass? (It goes to a side)
Directional selection
In the example shown in lecture, what mode of selection is acting on human birth weight? (most individuals are in average size)
Stabilizing selection
In the example shown in lecture, what mode of selection is acting on the phenotypes of the goldenrod gall fly? (Extreme phenotypes are more common)
Disruptive selection
In the example shown in lecture, which mode of selection is acting on the colour morph of the rewardless orchid?
Frequency Dependent
What happens when a single specie results in two daughter species?
It speciates
Speciation
Interruption of gene flow between populations that formerly interbred. Physical and ecological processes interact with selection and drift to produce a new species. It results in cladogenesis
Which three types of speciation are there?
- Allopatric
- Parapatric
- Sympatric
Separation of populations is large relative to dispersal distances, large barrier
Allopatric speciation
Characteristics of allopatric speciation
- Prevents gene flow, populations can evolve independently
- Adaptation to different local environments
- Reproductive isolation “tested” if barrier disappears
