Podcast
Questions and Answers
What concept suggests that the simplest explanation with the fewest changes is the best hypothesis in evolutionary biology?
What concept suggests that the simplest explanation with the fewest changes is the best hypothesis in evolutionary biology?
Which type of data combines genetic information with fossil records to clarify relationships between species?
Which type of data combines genetic information with fossil records to clarify relationships between species?
What is the term for data that does not provide useful information for understanding evolutionary relationships?
What is the term for data that does not provide useful information for understanding evolutionary relationships?
Which type of changes in DNA sequences are more frequent according to recent studies?
Which type of changes in DNA sequences are more frequent according to recent studies?
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What methodological challenge is often faced in large phylogenetic reconstructions?
What methodological challenge is often faced in large phylogenetic reconstructions?
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How can the molecular clock be calibrated for estimating evolutionary timeframes?
How can the molecular clock be calibrated for estimating evolutionary timeframes?
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In genetic comparisons, how does a lesser number of sequence differences between two species affect their relationship?
In genetic comparisons, how does a lesser number of sequence differences between two species affect their relationship?
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What is a significant limitation of the molecular clock in evolutionary studies?
What is a significant limitation of the molecular clock in evolutionary studies?
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Which of the following represents a prezygotic isolation mechanism?
Which of the following represents a prezygotic isolation mechanism?
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What are the evolutionary transitions significant in vertebrates?
What are the evolutionary transitions significant in vertebrates?
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Which statement about genetic isolation is true?
Which statement about genetic isolation is true?
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Which of the following statements about mutations and polyploidy is accurate?
Which of the following statements about mutations and polyploidy is accurate?
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When females from one population mate with males from another but produce no viable offspring, this refers to what type of isolation?
When females from one population mate with males from another but produce no viable offspring, this refers to what type of isolation?
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What is a consequence of gradual changes in animals due to environmental gradients?
What is a consequence of gradual changes in animals due to environmental gradients?
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Which of the following describes a characteristic of coelomate animals?
Which of the following describes a characteristic of coelomate animals?
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Reproductive isolation mechanisms can be categorized into which two types?
Reproductive isolation mechanisms can be categorized into which two types?
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What is the primary effect of mutation on genetic diversity?
What is the primary effect of mutation on genetic diversity?
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What type of mutation changes a single base pair in the DNA sequence?
What type of mutation changes a single base pair in the DNA sequence?
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Which of the following statements about gene flow is true?
Which of the following statements about gene flow is true?
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In the study of E. coli, how did mutation impact relative fitness over generations?
In the study of E. coli, how did mutation impact relative fitness over generations?
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What is the effect of lateral gene transfer in pea aphids?
What is the effect of lateral gene transfer in pea aphids?
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Which type of mutation can change a codon into a stop codon?
Which type of mutation can change a codon into a stop codon?
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How does mutation primarily occur in bacteria and archaea?
How does mutation primarily occur in bacteria and archaea?
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What determines whether a mutation is beneficial, neutral, or deleterious?
What determines whether a mutation is beneficial, neutral, or deleterious?
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Which of the following is NOT a type of mutation at the chromosome level?
Which of the following is NOT a type of mutation at the chromosome level?
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What role does mutation play in the overall process of evolution?
What role does mutation play in the overall process of evolution?
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What effect does natural selection have on mutations that produce beneficial alleles?
What effect does natural selection have on mutations that produce beneficial alleles?
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Which of the following statements best describes genetic drift?
Which of the following statements best describes genetic drift?
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Which of the following is a characteristic of the mutations that occur in eukaryotes?
Which of the following is a characteristic of the mutations that occur in eukaryotes?
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Study Notes
Augmenting Wild Populations
- Captive bred fish can have positive and negative effects on wild populations.
- More fish can reduce the impact of fishing.
- Lower average fitness in captive bred fish can have negative impacts on wild populations.
- Natural gene flow does not reduce fitness.
- Gene flow can replenish lost alleles due to genetic drift, increasing genetic variation.
- Gene flow can increase or decrease fitness depending on the situation.
- Movement of alleles between populations reduces their genetic variation.
Mutation
- Evolutionary mechanisms like natural selection and genetic drift reduce genetic diversity.
- Mutation restores genetic diversity by creating new alleles.
- Point mutations change a single base pair of DNA.
- Point mutations can result in a different amino acid, change gene expression regulation, and are mostly neutral or deleterious.
- Chromosome level mutations include inversions, translocations, deletions, and duplications.
- Lateral gene transfer (horizontal gene transfer) is the transfer of genes between species.
- Mutation can produce beneficial alleles, increasing fitness.
- Mutation can produce neutral alleles with no effect on fitness.
- Mutation mostly results in deleterious alleles, decreasing fitness.
- Mutations are random with respect to fitness.
- Mutation alone is usually inconsequential in changing allele frequencies over a short time period.
- Mutation can be a significant evolutionary process in bacteria and archaea because of their short generation times and high mutation rates.
Mutation Rates
- Human germline mutation rate is 1.2 x 10^-8 per base pair per generation.
- Human genome size is 3 billion base pairs (haploid).
- Number of mutations per generation in a diploid human is 37.
- Mutation is slow compared to selection, genetic drift, and gene flow.
E. coli - Mutation and Evolution
- Richard Lenski studied 12 populations of E. coli over 10,000 generations.
- E. coli reproduces asexually, so mutation is its only source of genetic variation.
- Relative fitness of descendant generations increased dramatically over time in jumps.
- This pattern resulted from novel mutations conferring fitness benefits under selection.
- After a beneficial mutation occurred, fitness changed little until another random mutation produced an increase in fitness.
- The experiment demonstrated the combination of mutation and natural selection.
Pea Aphids
- Pea aphids feed on sap.
- Two phenotypes - red and green - are maintained by balancing selection.
- Ladybird beetles prey on red aphids, and wasps lay eggs on green aphids.
- The color comes from carotenoid pigments, not from their food.
- Aphids are the first animals discovered to generate their own carotenoids.
- The genes for the metabolic pathway came from lateral gene transfer from a fungal symbiont.
- Additional point mutations occurred after lateral gene transfer, allowing aphids to synthesize yellow, red, and green carotenoids.
- A deletion produced green aphids, demonstrating that a loss of function allele can be adaptive.
Importance of Mutation
- Mutation is the ultimate source of genetic variation.
- Crossing over and independent assortment shuffle existing alleles into new combinations, but only mutation creates new alleles.
- Mutation happens randomly, not because organisms want or need it.
- Without mutations, evolution would stop.
Evolutionary Mechanisms and Genetic Diversity
- All four evolutionary mechanisms (mutation, natural selection, genetic drift, and gene flow) have different consequences for allele frequencies.
- All violate Hardy-Weinberg assumptions.
- The ultimate result of these mechanisms is genetic diversity.
The Principle of Parsimony
- The simplest explanation is often the best explanation.
- Used to find the most parsimonious tree in phylogeny.
- Requires a way to count changes on any given phylogeny.
- Involves searching among all possible phylogenies to minimize changes.
Using DNA Sequences to Create Phylogenies
- Most biologists rely on RNA and DNA sequences from different organisms to create phylogenies.
- Compare homologous sequences of nucleotides.
- Fewer sequence differences between two species suggest a closer relationship.
Difficulties of Large Phylogenetic Reconstructions
- Often greater than 500bp of sequence per gene.
- Aligning genes is challenging and requires algorithms.
- More complex models are needed for DNA evolution, as certain types of DNA evolution occur more often than others.
Molecular Clock
- DNA and protein sequences evolve at a relatively constant rate over time.
- Most changes are neutral.
- Can be used to date nodes on a tree.
- Not perfect, as it relies on neutral theory.
- Some DNA sequences evolve rapidly and will not tick in a clock-like manner.
Calibrating the Molecular Clock
- Compare DNA sequences of species that diverged as a result of geological events.
- Use fossils of known age to date nodes and calibrate the clock.
Vertebrate Evolutionary Transitions
- Key transitions in vertebrate evolution include the evolution of jaws, lungs, limbs, amniotic eggs, and endothermy (warm-bloodedness).
Reproductive Isolation
- Prezygotic isolation prevents fertilization.
- Postzygotic isolation occurs when mating occurs, but there is no viable offspring production.
Evolutionary Change
- Mutation is necessary for creating new genetic diversity.
- Polyploidy is not necessary for evolutionary change, but it can occur in plants.
Genetic Isolation
- Genetic isolation happens when populations are separated by barriers to gene flow.
Geographic Gradients
- Gradual changes can be observed in animals as both elevation and latitude increase, often due to environmental gradients.
Reproductive Isolation
- Reproductive isolation includes any mechanism that stops gene flow between two populations.
- It can be prezygotic or postzygotic.
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Description
Explore the impacts of captive breeding on wild fish populations and understand the role of mutations in restoring genetic diversity. This quiz covers key concepts such as gene flow, natural selection, and the effects of point and chromosome-level mutations on evolution. Test your knowledge on these important evolutionary mechanisms!
