Week 21 Jalia Flashcards
Define genetic drift and gene flow
Genetic drift is the changes in allele frequency in a population due to random variation in death and reproduction.
Gene flow is the process of alleles moving from one population to another
How can genetic drift and gene flow cause allele frequencies in a population to change overtime
Genetic drift: Allele frequencies change due to random chance, like mortality or reproduction, which has a larger effect in small populations
.
Gene flow: Allele frequencies change when individuals from one population introduce new alleles into another population
.
Contrast: Genetic drift is random and significant in small populations, whereas gene flow involves direct movement of alleles between populations, often homogenizing genetic variation.
What is the effect that genetic drift and gene flow have on average fitness and genetic variation in a population
Genetic drift:
Can reduce genetic variation over time as alleles are lost randomly
.
Effects on fitness depend on which alleles are lost (neutral vs. beneficial alleles)
.
Gene flow:
Can increase genetic variation within a population by introducing new alleles
.
May reduce fitness if maladaptive alleles are introduced
What is Natural selection in the evolutionnary processes
Allele frequencies in a population change due to
differences in survivorship and/or reproduction due differential success of different traits in a given environment.
Non-Random
Environmental selection and sexual selection
Genetic drift
Allele frequencies in a population change/ fluctuate due to chance (random process)
- Random Chance
Can random mortality change allele frequencies
yes
Why doesn’t genetic drift impact large populations as much as small populations?
Each individual counts more in a small population than in a large population.
Founder effect
New population likely to have different allele
frequencies than source population, by chance
Genetic Bottleneck
Results when most individuals in a large population die
Differentiate between genetic drift in a population vs. a founder effect or bottleneck event.
Genetic drift: Random changes in allele frequencies within any population, often due to random reproduction or mortality
.
Founder effect: Occurs when a small group establishes a new population, and their allele frequencies differ from the original population
.
Bottleneck event: Results from high mortality in a large population, leaving a small group with different allele frequencies
Recognize and explain examples of founder effects and bottleneck events.
Founder effect: Example includes the Old Order Amish population with polydactyly.
Bottleneck event: Example includes natural disasters like floods or droughts causing random mortality, leaving a small population.
Biologists are studying a population of beetles that are either brown or green. From previous research, the researchers know
that color is determined by a single allele and does not have an environmental influence. They track the population over time and observe an increase in the frequency of brown beetles in the population. What has definitely occurred?
EVOLUTION
