Evolution Flashcards
evolution
change in allele frequencies in populations over successive generations
gene
“locus” (region) of DNA
Alleles
alternative forms of the same gene
Biological fitness
ability of an organism to produce surviving offspring
Adaptation
heritable trait that increases the fitness of an individual in a particular environment compared to other individuals that don’t have this trait
the 5 key mechanisms of evolution
- mutation
- genetic drift
- natural selection
- sexual selection
- gene flow
what is the ultimate source of all genetic variation?
mutations
effects of mutations
by changing the genetic code new alleles are generated which can…
- change amino acid sequences or alter gene expressions
most mutations decrease
fitness
genetic drift
random changes in allele frequency
genetic drift is stronger in
smaller populations
example of genetic drift
walking and randomly stepping and killing a bunch of bugs
when do you expect strong effects of genetic drift?
population bottlenecks - when species go close to extinction
when do you expect strong effects of genetic drift?
founder effect: new island - first few animals arrive on island and repopulate
Natural selection was discovered by
Charles Darwin and Alfred Wallace
Natural selection is the idea that
traits that improve survival/reproduction should increase in frequency through time
Example of natural selection in nature
Daphne Major drought
Daphne major drought
- drastic ecological changes led to a decrease in seed abundance
- little soft seeds dried out and only the hard large seeds were left
- high mortality of darwin finches because all their food was gone
- finches with larger beaks were more likely to survive
- traits are heritable: relationships between beak size of parents and off spring
intra-sexual
male-male competition
inter sexual
female choice
natural and sexual selection often act in…
opposition to each other
Gene flow
movements of genes among populations
gene flow tends to oppose divergent
natural selection
