Natural Selection Flashcards
What two things are needed for evolution to occur
Needs to be a variation in traits within a population
Needs to be a variation in reproductive success among individuals
What % of behavioural traits are inherited
30
What % of physiological traits are inherited
33
What % of morphological traits are inherited
46
What things define fitness
Number of copies of allele passed on to next generation
Lifetime reproductive success
What is micro evolution
When natural selection causes changes in the relative frequencies of alleles in a population
Why is reproductive success more important than advantageous alleles
No point having advantageous alleles if can not reproduce as they are not passed on
Eg sparrows with long wings is more advantageous but short winged sparrows reproduce more often - short wing allele passed on so more short wings than long
What year did Darwin visit the Galapagos
1835
What species of finches was studied by Darwin
Geospiza fortis
Why did 1976-1977 drought on Isla Daphne Major cause
A decline in the population of geospiza fortis
Why did the number of seeds decrease during the drought
Plants focused on surviving rather than reproducing so produced less seeds
Why did long beaked geospiza birds eat more than small beaked geospiza birds during the drought
The seeds of plants hardened (thin in rainy season) meaning only long beaked birds were able to crack them and eat them
Why did bill depth of geospiza fortis increase after the drought
As the birds with the bigger bills were the only ones that could eat during the drought, they survived and reproduced meaning the offspring were born with bigger bills
Across how many generations did the microevolution of bill size
1
Directional selection
Shift in one direction either left or right
Diversifying selection
Extremes successful so dip in the middle
Stabilising selection
Middle successful so mostly middle
What a the three components of natural selection
Survival selection
Sexual selection
Kin selection
What is survival selection
Selection for traits that maximises survival
What is sexual selection
Selection for traits that enhance reproductive success
What is kin selection
Selection for traits that maximise the fitness of close kin
Why did Darwin consider sexual selection to be separate from natural selection
Sexual traits can increase fitness but reduce the individuals survival
Eg male peacocks have big tales to attract females - increases reproductive success and fitness - but makes them easy targets for predators - reduces individual survival
What are the two types of sexual selection
Intra sexual selection
Inter sexual selection
What is intra sexual selection between
Two males
What does intra sexual selection lead to
Evolution of weapons and size dimorphism
What is size dimorphism
One gender is bigger than the other
What does inter sexual selection lead to and why
Leads to evolution of elaborate male ornaments that advertise male quality because inter sexual selection maximises traits that maximises the chances of breeding with females
Why might Traits that lower the individuals survival rate be favourable
It increases the fitness of close kin
Kin selection
When does adaptive evolution occur
When variation in heritable traits is correlated with differential reproductive success
