Unit 3 - Evolutions in Populations Flashcards
What is a population?
A group of individuals of the same species that live in the same area and interbreed.
____ are composed of populations of individuals.
Species
What is an allele?
Genetic variants on loci.
What is frequency?
The proportion of the population with that genotype of allele.
What is a gene pool?
It consists of all copies of every allele at the loci of interest in all members of the population.
What are polymorphic populations?
When a population or gene pool has more than one allele.
What are monomorphic populations?
When a population or gene pool has only one allele. Allele is “fixed”.
What is evolution at the scale of a population defined as?
A chance in allele frequency over generations.
What is allele frequency?
The proportion of a specific allele out of the total number of alleles in the gene pool.
In a gene pool, there are 20 B alleles and 80 b alleles. What is the frequency of the “b” allele?
0.8
What is evolution?
The change in allele frequency over generations.
What does the frequency of all alleles add up to?
One.
At a locus with two allele, p = 0.65. What is q?
0.35
What are the four processes that change allele frequencies?
Mutation, drift, migration, and selection.
In a population of 320 red flowers(CRCR), 20 white flowers(CWCW), and 160 pink flowers(CRCW), how many CW alleles are there?
200
When can you calculate expected genotype frequencies?
When the allele frequency is known in the parental population and when there is random mating in the parental population.
What is random mating?
When every individual has as equal and independent chance of mating with every other individual.
What is the rule of probability?
If samples are drawn at random, the probability of a given item being included in the samples equals the frequency of that item in the source population.
What does the Hardy-Weinberg equation predict?
Genotype frequencies from allele frequencies. (p^2 +2pq + q^2)
What type of population will genotype and allele frequencies will be constant under the Hardy-Weinberg model?
A population that is not evolving and randomly mating.
What can the Hardy-Weinberg equation test?
Whether a population is evolving or not.
When there is a significant deviation from HWE, what does it suggest?
One of the HWE assumptions were violated.
What do we assume with HWE?
There is no selection, no mutation, no migration, a large population, and random mating.
Approximately ___ of the US population carry PKU alleles.
2%
What are allele frequencies?
The proportion that allele makes up of the total.
What can genotype frequencies do?
They will rapidly achieve HWE for a given set of allele frequencies.
What is evolution?
A change in allele frequencies in a population over time.
What are random processes?
Processes that can have different outcomes, but cannot be predicted.
What is an example of a random process?
Flipping a coin.
What is genetic drift?
It is the random change of allele frequencies from one generation to the next due to random events.
What is a haploid?
An individual that has only a single copy of their genes.
What causes random sampling in real populations?
Any process that has the effect of randomly increasing or decreasing allele frequencies.
What is the meiosis lottery?
One large source of random sampling.
What are the two main facts about drift?
- It is the main driver of evolution at the genetic level.
- It is the null hypothesis when testing for other evolutionary processes.
Drift causes _____ changes from generation to generation in smaller populations.
Extreme
What is fixation?
When the allele frequency of one allele reaches 100%, also occurs more rapidly in small populations.
What are the two forms are genetic drift?
Founder effect and bottleneck effect.
What is the found effect?
Occurs when a small number of individuals become isolated from a larger population.
Island populations have much ____ genetic diversity vs. the mainland.
Lower
What is the bottleneck effect.
A magnification of the effect of genetic drift due to a reduction in size within a population.
Where does the bottleneck effect occur?
Within a single population.
What does genetic drift do to evolution?
- Makes the evolutionary process more random
- Reduces genetic variation
- Can result in the fixation of alleles.
What is gene flow?
The movement of alleles between populations due to migration.
What is migration?
The movement of an individual from one population to another.
Gene flow tends to make populations __________ over time.
more genetically similar
If all gene flow between two populations suddenly stopped, we would expect them to start becoming ___ different over time.
more
Isolation by distance is a pattern of _____ genetic differences with ____ geographic distance.
increasing; increasing
What is genetic swamping?
The reduction in a population’s ability to adapt due to gene flow from a maladapted population.
What is adaptive introgression?
The movement of beneficial alleles between populations, which facilitates adaptation.
What is FST?
A measure of genetic differences between populations. Ranges between 0 and 1.
What is natural selection?
The differential survival and reproduction of individuals/genotypes due to differences in phenotype.
True/False: No other evolutionary
process causes adaptation.
True.
What are the basic requirement for evolution via natural selection.
- There is phenotypic variation in the population.
- The variation is at least somewhat heritable.
- The variation results in differences in fitness.
What is fitness?
A quantitative measure of how much an individual with a particular phenotype or genotype will contribute to the next generation on average.
True/False: Strength, intelligence,
speed, etc. is not necessarily connected to evolutionary fitness.
True.
What are the three main forms of selection?
Directional selection, disruptive selection, and stabilizing selection.
What is directional selection?
An increase in the frequency of a trait or allele due to a fitness benefit.
Directional selection tends to ____ genetic variation.
reduce
What is disruptive selection?
Changes in population genetics in which extreme values for a trait are favored over intermediate values
What is stabilizing selection?
The population mean stabilizes on a particular non-extreme trait value.
What is balancing selection?
Selection that maintains two or more phenotypic forms in a populations.
