12.1 Study Guide Flashcards
(10 cards)
What is natural selection?
The process where the environment impacts an organism’s ability to survive and pass on their successful traits. Organisms may be selected against and die if their traits do not help them survive.
What is genetic drift?
Genetic drift is caused by random, chance events. The organism’s that survive these chance events pass on their traits to the next generation. The allele frequency changes because some of the alleles die out with the organisms.
What is variation?
The diversity of alleles and the combinations of alleles in a population. Diversity is caused by mutations.
What is fitness?
Fitness is an organism’s ability to survive and reproduce. Fitness is measured by the amount of fertile offspring/descendants of an organism.
What is differential reproduction?
The phenomenon where some organisms in a population leave more offspring than others. This is often due to specific traits that enhance the chance of an organism surviving and reproducing.
What is adaptation?
A genetic variation that increases fitness.
What are the five fingers of evolution and how can they cause changes in allele frequencies?
Pinky=The population can decrease: The population can decrease in size, changing the allele frequency.
Ring finger=Mating: If individuals mate with other individuals, they will create offspring with different alleles, changing the allele frequency.
Middle finger=Mutation: Causes new alleles and genes.
Index finger=Movement: Immigration (gene flow), new genes in a population change the allele frequency.
Thumb=Natural Selection: Some alleles do not code for successful traits, but some do. Successful traits are passed on, adapting populations.
Compare the causes and the effect of natural selection vs. genetic drift.
Natural Selection: Natural selection is caused by adaptive change due to the environment’s effect on the organisms. The effect is that organisms with successful traits survive and pass on their traits, which changes the allele frequency.
Genetic Drift: Genetic drift is caused by chance events, making it a random change. Similarly to natural selection, the organisms that survive these events pass on their traits, creating a variation in allele frequency.
Describe graphs of how allele frequencies may change during natural selection under different amounts of selective pressure.
In a graph with high selective pressure against an allele. The successful alleles frequency would increase to a high level, while the selected against allele would decrease. They would both increase/decrease at the same intervals because their combined frequency must be 1.0.
In a graph with low selective pressure against an allele, the frequencies of the alleles would be similar and would increase and decrease at the same interval.
The allele frequencies would either go up or down and would not change because one is successful while the other does not survive.
Describe graphs of how allele frequencies may change due to genetic drift in smaller vs. larger populations.
In a small population, the allele frequency would change very quickly. The allele frequencies would go up and down together as the random change events occur. However, eventually, one would have a much higher frequency than the other because the organisms were able to survive the random chance events. In a large population, the allele frequencies would go up and down but remain relatively similar to each other. This means that smaller populations are more susceptible to genetic drift.
