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Questions and Answers
What does heritability measure in the context of phenotypic variation?
What does heritability measure in the context of phenotypic variation?
Which of the following best describes phenotypic variation?
Which of the following best describes phenotypic variation?
Which factor primarily contributes to the variance in phenotypes observed in a population?
Which factor primarily contributes to the variance in phenotypes observed in a population?
What does the Breeder's Equation predict in evolutionary biology?
What does the Breeder's Equation predict in evolutionary biology?
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In the context of sexual selection, what typically occurs among males?
In the context of sexual selection, what typically occurs among males?
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What does heritability (h²) represent in quantitative genetics?
What does heritability (h²) represent in quantitative genetics?
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Which of the following best describes phenotypic plasticity?
Which of the following best describes phenotypic plasticity?
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How does the environment interact with genetics in determining phenotypes?
How does the environment interact with genetics in determining phenotypes?
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What role does heritability play in predicting evolutionary changes?
What role does heritability play in predicting evolutionary changes?
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In the context of the breeder's equation, what does 'V_G' stand for?
In the context of the breeder's equation, what does 'V_G' stand for?
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What does a higher heritability value indicate about a trait?
What does a higher heritability value indicate about a trait?
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In the breeders equation R = hS, what does 'S' represent?
In the breeders equation R = hS, what does 'S' represent?
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If a trait has a heritability (h²) of 0.5 and the selection differential (S) is 0.5, what is the response to selection (R)?
If a trait has a heritability (h²) of 0.5 and the selection differential (S) is 0.5, what is the response to selection (R)?
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What is the primary influence on phenotypic variation when heritability is low?
What is the primary influence on phenotypic variation when heritability is low?
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Which of the following statements best describes the relationship between heritability and evolutionary change?
Which of the following statements best describes the relationship between heritability and evolutionary change?
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What does a heritability value of 1 indicate?
What does a heritability value of 1 indicate?
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When calculating the expected response to selection, what is considered as the initial mean trait value in the parent generation?
When calculating the expected response to selection, what is considered as the initial mean trait value in the parent generation?
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What is the outcome when a trait demonstrates both high heritability and high environmental variability?
What is the outcome when a trait demonstrates both high heritability and high environmental variability?
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Study Notes
BioL2X: Genomes to Ecosystems (G2E)
- This course covers the development, and effects of evolution on ecosystems.
Lecture Structure
- Pattern and process: evolution and selection
- Principals of natural selection
- Natural selection and the modern synthesis
- How selection acts on phenotypes
- Quantitative genetics and heritability
- Special cases: sexual selection
Evolution: Pattern and Process
- Pattern refers to the changes observable in the fossil record throughout time.
- Evolutionary relationships are inferred between fossil organisms and their living descendants.
- Extinct and extant organisms are related in some way.
Evolution: Pattern and Process (Inferring Ancestry)
- Homology demonstrates ancestry.
- Evolutionary change is driven by various processes, including selection.
Keeping on your toes...
- Question: Which of the following is true about Pakicetus?
- Answer: B. Pakicetus is more closely related to modern whales than it is to hippos.
- Pakicetus is an early ancestor to modern whales.
Evolution: Pattern and Process (Ecological Opportunities)
- Ecological opportunity: shallow equatorial Tethys ocean provided abundant marine food sources, driving whales into the ocean.
Evolution: Pattern and Process (Summary)
- Evolution's pattern is observable in the fossil record.
- Relationships are inferred between fossils and living organisms.
- All organisms are assumed to be related in some way.
Natural Selection and the Modern Synthesis
- Every species is fertile, but populations remain stable.
- Resources are limited. A struggle for survival follows.
- Individuals vary, and much of this variation is heritable.
- Individuals less suited to the environment are less likely to survive and reproduce.
- Individuals better suited to the environment have higher survival and reproduction rates passing on their traits.
Natural Selection and the Modern Synthesis: Mendel Meets Darwin
- Darwin recognized inter-individual variations were heritable, and developed pangenesis (gemmules produced by all tissues).
- Mendel studied inheritance with seven phenotypic traits.
- Mendel's work described two rules for inheritance: segregation and independent assortment.
- Mendel's observations defined genes as factors.
Natural Selection and the Modern Synthesis: Modern Synthesis is Born
- Malthusian competition, variation, and natural selection are crucial elements that contribute to the modern synthesis.
How Does Selection Act on Phenotypes?
- Selection pressures act on phenotypes, not genotypes.
- Stabilizing (purifying) selection: Selection against extreme trait values. Reduces phenotypic variation and maintains a stable trait mean.
- Directional selection: Mean trait value shifts in response to the direction and intensity of selection.
- Disruptive selection: Selection against the mean. Results in a multimodal trait distribution.
Special Cases: Sexual Selection
- Darwin observed characteristics in sexually dimorphic species (differences between male and female in a species) that could not be readily explained by natural selection.
- Intrasexual selection: Competition within the same sex for mates.
- Intersexual selection: Mate choice.
- Reproductive success is influenced by sexual selection.
Quantitative Genetics and Heritability
- Heritability is the ratio of genetic variation to total phenotypic variation in a population, and it is important because it connects selection pressures to evolutionary consequences.
- The bigger the heritability of a trait, the faster selection will cause evolutionary changes in this trait.
- Evolutionary changes can be predicted based on heritability.
Quantitative Genetics and Heritability (Example- Giraffes)
- G1 generation: Average giraffe height = 4 m
- G1 after selection: Average giraffe height = 4.5 m
- Calculate R (response to selection): R = h²S
- S = the selection differential (G2 generation height- G1 height)
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Description
Test your understanding of the principles of evolution and natural selection as discussed in the BioL2X course. This quiz covers key topics such as evolutionary processes, heritability, and the relationship between extinct and extant species. Prepare to explore how these concepts shape ecosystems.
