18 Questions
What is the primary mechanism responsible for the adaptation of organisms to their environment?
Natural selection
What is the result of a population experiencing a bottleneck, in terms of genetic variation?
Loss of allelic variation
What is the term for the random change in allele frequencies in a population over time?
Genetic drift
What is the term for the transfer of alleles from one population to another?
Gene flow
What is the primary source of genetic variation in a population, according to the text?
Mutation and sexual reproduction
What was the key concept missing from Darwin's explanation of evolution, according to the text?
Understanding of inheritance
What is the primary effect of a bottleneck on a population's genetic variation?
Loss of allelic variation due to the reduction in population size
What is the primary mechanism responsible for the change in the average beak size of the finch population following the drought?
Natural selection acting on the individual finches
What is the main consequence of a reduction in population size on the population's genetic variation?
Loss of genetic variation due to the reduction in population size
What is the role of genetic drift in conservation biology?
It leads to the loss of genetic variation in a population
What is the effect of the influx of new alleles from other populations on the population's genetic variation?
It increases genetic variation in the population
What is the primary difference between genetic drift and natural selection?
Genetic drift is a random change in allele frequencies, while natural selection is a non-random change
What is the primary reason why mutations have a small effect on allele frequencies from one generation to the next?
Mutations are rare
What is the term for the change in allele frequencies that occurs when a new population is established from a small group of individuals?
Genetic drift
In a population that is not undergoing genetic drift, what is the primary mechanism by which allele frequencies can change over time?
Natural selection
What is the term for the movement of individuals with different alleles into a population, which can increase genetic variation?
Gene flow
In the context of conservation biology, why is genetic drift a concern?
It can lead to the loss of allelic variation
What is the term for the random change in allele frequencies that occurs when a population undergoes a bottleneck event?
Genetic drift
Study Notes
Microevolution
- Microevolution is the change in allele frequencies in a population over time
- Three mechanisms cause allele frequency changes: natural selection, genetic drift, and gene flow
Natural Selection
- Only mechanism of adaptive evolution, improving the match between organisms and their environment
- Acts on individuals, affecting their survival and reproductive success relative to others in the population
- Individuals with variations better suited to the environment tend to produce more offspring
- Examples: finches with larger beaks surviving drought on Galápagos Islands, Drosophila melanogaster developing insecticide resistance
Evolution and Inheritance
- Mutation and sexual reproduction produce genetic variation, making evolution possible
- Charles Darwin proposed a mechanism for species change over time, but lacked understanding of inheritance
- Gregor Mendel's particulate hypothesis of inheritance stated that parents pass on discrete heritable units (genes) that retain their identities in offspring
Evolution at the Population Level
- Populations, not individuals, evolve
- Evolutionary impact of natural selection is apparent only in changes in a population over time
- Individual traits do not change during their lifetime, but populations can evolve through natural selection
Mechanisms of Evolution
- Mutation can ultimately have a large effect on allele frequencies when producing new alleles that strongly influence fitness
- Nonrandom mating affects frequencies of homozygous and heterozygous genotypes, but usually has no effect on allele frequencies
- Three mechanisms directly alter allele frequencies: natural selection, genetic drift, and gene flow
Test your understanding of microevolution, including the mechanisms that cause allele frequencies to change, such as natural selection, genetic drift, and gene flow. Learn how these processes shape the evolution of populations over time.
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