Natural Selection Flashcards
What are the three basis/conditions for natural selection?
Variation
Heritability
Competition and fitness
What are the types of variation? Give an example
Continuous - colour morphs in moths, body size
Discrete - banding intensity on snail shells
Is variation completely random?
No
Has deterministic genetic basis
What does Mendelian inheritance not produce?
A directional change in gene frequency
What is ecological competition due to?
Limited amounts of resources
Direct relationship between amount of resource captured and fitness
What is the definition of fitness in relation to natural selection?
A measure of reproductive success of an individual
When would fitness = 1.0?
When individuals pass on 100% of their genes to the next generation
For diploid organisms, need to produce at least 2 organisms to get a fitness of 1.0
Why is colour important for mushrooms?
Darker mushrooms absorb heat faster and so create spores faster
What is fecundity and fertility?
The amount of offspring produced every reproductive event
What is selection?
A change in gene frequency
When does selection occur?
When genotypes differ in their ability to pass genes on to the next generation
What happens if a genotype is (un)successful?
Unsuccessful - its genes will decrease in frequency
Successful - its genes will increase in frequency
What are the types of natural selection?
Directional - selection generates a long-term change in a trait
Stabilising - selection against extreme trait values
Disruptive - selection for multiple optimum trait values
What is an example of stabilising selection?
*Bicyclus anynana
Has eyespots that provide defence against predators
Selection against eyespots that are too large or too small
