24 Questions
What is the result of a single generation of random mating in a population?
The population reaches equilibrium genotypic frequencies of p2, 2pq, and q2
What is the effect of natural selection on allele frequencies?
It increases the frequency of alleles that provide a reproductive advantage
What is genetic drift?
A random change in allele frequencies
What is the result of a population meeting the Hardy-Weinberg assumption?
The population cannot evolve
What is the effect of stabilizing selection?
It favors intermediate forms of a phenotype
What is the mechanism by which individuals near the center of a phenotype range have a higher fitness?
Stabilizing selection
What is the result of disruptive selection?
The rise of two distinct phenotypes
What is the effect of migration on a population?
It increases genetic variation
What is the result of mutation in a population?
An increase in genetic variation
What is the mechanism by which genetic variation is increased between generations within a species?
Mutation
What is the primary source of new alleles in a population?
Mutation
What can happen to a phenotype if it becomes too common in a population?
Its frequency declines
What is the result of a genetic variation that confers no competitive advantage to an individual?
Neutral variation
What is the effect of diploidy on genetic variation in a population?
It hides genetic variation from selection
What is the primary mechanism by which organisms adapt to their environment?
Natural selection
What is an example of balanced polymorphism?
Heterozygote advantage
Which process leads to adaptation due to differences in survival or reproduction?
Natural selection
What is the result of natural selection acting on a population over several generations?
The development of a new species
What is the role of mutation in the process of evolution?
It increases genetic variation
What is the main difference between genetic drift and natural selection?
Genetic drift is random, while natural selection is non-random
What is the result of a population experiencing genetic drift?
A decrease in genetic variation
Which of the following is an example of natural selection?
The development of antibiotic resistance in bacteria
What is the role of migration in the process of evolution?
It increases genetic variation
Which of the following is an example of genetic drift?
The random fixation of a certain allele in a population
Study Notes
Genetic Variation and Evolution
- Genetic variation occurs between generations within a species due to mechanisms such as Natural Selection, Sexual Selection, Artificial Selection, Genetic Drift, and Gene Flow.
Hardy-Weinberg Equilibrium
- A population in Hardy-Weinberg Equilibrium (HWE) has genotypic frequencies determined by allelic frequencies.
- In HWE, the heterozygote frequency never exceeds 0.5, and when a recessive allele is rare, most individuals who carry the allele are heterozygous.
Types of Natural Selection
- Directional Selection: favors individuals with extreme phenotypes, leading to an increase in the frequency of the favored allele.
- Stabilizing Selection: favors individuals with intermediate phenotypes, leading to a decrease in the frequency of extreme alleles.
- Disruptive Selection: favors individuals with extreme phenotypes, leading to an increase in the frequency of both extreme alleles.
Examples of Natural Selection
- Human babies at birth: stabilizing selection favors babies with average birth weights.
- Pesticide resistance: directional selection favors individuals with resistant phenotypes.
- Peppered moth: directional selection favors individuals with dark-colored wings.
- Finches in West Africa: directional selection favors individuals with large or small beak sizes, leading to specialization in seed cracking.
Limitations of Evolution
- Evolution is limited by historical constraints, such as the lack of certain mutations.
- Mutations are often neutral or harmful, and only beneficial in changing environments.
- Diploidy can hide genetic variation from selection, and dominant alleles can "hide" recessive alleles in heterozygotes.
Balanced Polymorphism
- Balanced polymorphism is the ability of natural selection to maintain stable frequencies of at least two phenotypes.
- Heterozygote advantage is an example of balanced polymorphism, where heterozygotes have a higher fitness than homozygotes.
Co-evolution
- Co-evolution occurs when there is a reciprocal evolutionary response between two species, such as in parasite-host relationships.
- Example: the survival of one phenotype declines if that form becomes too common, leading to the emergence of new resistant phenotypes.
Neutral Variation
- Neutral variation is a genetic variation that results in no competitive advantage to any individual.
- Neutral variation can be maintained in a population due to genetic drift or other mechanisms.
Natural Selection and Adaptation
- Natural selection is the only agent of microevolution that consistently works to adapt organisms to their environment.
- Natural selection leads to adaptation through the survival and reproduction of individuals with favored phenotypes.
Example of Natural Selection
- Resistance to antibacterial soap: natural selection leads to an increase in the frequency of the resistant allele over generations.
Understand the principles of genetics and evolution, including mutation, genetic drift, natural selection, and non-random mating. Learn how alleles combine to form genotypes and how these processes shape the evolution of species.
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