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45 Cards in this Set
- Front
- Back
Natural Selection |
increase the freq of certain alleles (i.e. the ones that contribute to reproductive success in a particular environment) |
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Genetic Drift |
causes allele frequencies to change randomly
may cause alleles that decrease fitness to increase in fitness |
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Gene flow |
when individuals leave one population, join another, and breed.
Movement of alleles between populations. -it equalizes allele frequencies between the source population and the recipient population
-Random with respect to fitness |
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Mutation |
modifies allele frequencies by continually introducing new alleles
-increases genetic diversity in population (ultimate source) |
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Hardy-Weinberg |
Important null hypothesis that can show that no other evolutionary processes are taking place (mating was random with respect to the gene)
Key: is a theoretical approach – this almost never happens! |
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State the two equations for the Hardy-Weinberg Principle |
Allele freq: p+q=1
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What five assumptions must be met for the Hardy-Weinberg Principle? |
1) Random mating - picking gamete from gene pool at random |
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Gene pool |
single group of alleles from gametes in each generation |
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Inbreeding |
-mating between relatives
Two points 1) increase in homozygosity, decreases heterozygosity |
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How can inbreeding speed up the rate of evolutionary change? |
it gets rid of recessive deleterious alleles(alleles that lower fitness) from a population. |
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Inbreeding Depression |
the decline in average fitness that takes place when homozygosity increases and heterozygosity decreases in a population |
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Heterozygote advantage |
Heterozygous individuals have higher fitness than homozygous individuals do.
Example: Sickle cell trait in people with sickle cell trait, the red blood cells are resistant to malaria infection. That means people with the trait are protected from the disease, and have an advantage over people without sickle cell trait. |
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Sexual selection |
courtship success
Sexual selection can take the form of: Intersexual selection---- or mate choice Intrasexual selection---- where individuals compete for mates
mechanism of evolutionary change |
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Genetic variation |
the number and relative frequencies of alleles that are present in a particular population, decreases genetic drift |
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Directional selection |
avors one extreme phenotype, causing average phenotype in pop to change in one direction, genetic variation is reduced |
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Stabilizing selection |
favors phenotypes near the middle of the range of phenotypic variation, maintaining average phenotype, genetic variation is reduced |
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Disruptive selection |
favors extreme phenotypes at both ends of range of phenotypic variation, genetic variation increases |
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Balancing selection |
no single phenotype is favored in all populations of a species at all times, genetic variation is maintained |
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Purifying selection |
when the disadvantageous alleles decline in frequency |
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Intersexual selection |
one mate choosing to mate with another mate of different genders |
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Intrasexual selection |
mates of the same gender fighting over the opposite gender |
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Fundamental asymmetry of sex |
females invest much more in their offspring than males |
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Sexual dimorphism |
refers to traits that differ between male and female |
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Genetic drift |
change in allele frequencies in a population due to chance
-more impactful on small populations |
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Gene flow |
The movement and exchange of genes or alleles from one population of species to another
Gene flow homogenizes (makes similar) populations |
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Sampling error |
The deviation of a result in a scientific experiment from the true result. As a rule of thumb, larger scale experiments have a lower sampling error (all things being equal bar the differentiating factor of the experiment). A larger scale represents a more apparent trend when the data has been collected to back a hypothesis or prove it wrong. |
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Genetic markers |
specific alleles that cause a distinctive phenotype |
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Founder event |
occurs when a group starts a new population in a new area
in small groups, allele frequencies probably differ from the source population |
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Founder effects |
change in allele frequencies with the creation of a population that follows a founder event.
-equalizes frequencies between source and recipient populations |
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Population Bottleneck |
A sudden decrease in population size
Caused by? -disease outbreaks or natural catastrophes
lead to genetic bottlenecks |
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genetic bottlenecks |
a sudden reduction in the number of alleles in a population.
Drift occurs during genetic bottlenecks and causes a change in allele frequencies |
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Deleterious alleles |
alleles that lower fitness |
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genetic isolation |
is population of organisms that has little genetic mixing with other organisms within the same species. This may result in speciation, but this is not necessarily the case. |
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What is the difference between genetic drift and gene flow? |
Genetic drift - causes allele frequencies to change randomly, not selection of fitness
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Does nonrandom mating change both genotype frequency and allele frequency? |
it only changes genotype frequency |
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What are the three key points for genetic drift? Where does genetic drift impact the most? |
1) it is random with respect to fitness |
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What are two examples of genetic drift? |
1) founder effect = immigrants establish new population
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What would happen to evolution if there was no mutation? |
Evolution would eventually stop because there would be no variation for selection and drift to act on. |
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How did diversity come to be? |
mutation, natural selection (change in allele frequencies) |
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What should happen.. if no evolution? |
allele frequency would stay the same |
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If genetic drift decreases, what happens to genetic variation within the population and between the population? |
genetic drift decreases genetic variation within population and increase genetic differences between populations |
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Movement of alleles between populations tends to reduce their what? |
genetic differences |
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Explain why genetic drift leases to a random loss or fixation of alleles |
when allele frequencies fluctuate randomly up and down, sooner or later the frequency of an allele will hit 0. that allele is lost from the population, and the other allele is fixed |
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Explain why genetic drift is particularly important as an evolutionary force in small populations. |
in small populations, sampling error is large. The accidental death of a few individuals would have a large impact on allele frequencies |
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Why does natural selection violate the Hardy-Weinberg principle? |
the hardy-weinberg principle predicts that allele frequencies will stay the same over time. natural selection favors some allele over others causing the frequency of those alleles to increase |