Quantative Traits Flashcards
What is the difference between adaptation and acclimatization in the context of genetic and physiological changes?
Adaptation involves genetic changes in a species over generations, while acclimatization refers to short-term physiological or behavioral adjustments to environmental conditions, such as sweating to cool off.
What is thermal tolerance, and what are its defining characteristics?
Thermal tolerance is the maximum temperature an individual can survive for more than 2 hours. It varies among individuals and is influenced by both genetic and environmental factors, often exhibiting a normal distribution.
What are the three conditions required for the evolution of thermal tolerance by natural selection?
Variation in thermal tolerance among individuals.
Thermal tolerance must affect fitness.
Thermal tolerance must be heritable.
What happens to thermal tolerance if it has no genetic basis?
If thermal tolerance has no genetic basis, natural selection in one generation will not result in changes to the mean thermal tolerance in the next generation.
What are quantitative traits, and how are they influenced?
Quantitative traits show continuous variation and are best described using a mean and variance. They are influenced by the combined activity of multiple genes (polygenic) and environmental factors.
How do genetic and environmental factors contribute to the normal distribution of quantitative traits?
Multiple genetic and environmental influences smooth out the variation, creating a normal distribution of the trait within a population.
What are the three forms of selection, and how do they impact trait variation?
Directional Selection: Favors one extreme trait value, shifting the mean.
Stabilizing Selection: Favors intermediate trait values, reducing variation.
Disruptive Selection: Favors extreme trait values, increasing variation.
How can graphs help recognize the form of selection?
Directional selection shows a shift toward one extreme, stabilizing selection peaks at the intermediate value, and disruptive selection shows reduced frequency of intermediate values with increased extremes.
Can parents pass their entire phenotype to their offspring? Why or why not?
No, parents only pass half their genes to offspring. The phenotype also depends on environmental and cultural influences, resulting in offspring traits being an average of the parental contributions.
What is a breeding value, and how is it estimated?
Breeding value (A) measures the average contribution of an individual’s genes to its offspring’s trait mean. It is estimated by examining the trait values of offspring relative to the population mean.
Why are additive genetic effects (A) emphasized in evolutionary studies?
Additive effects are predictably passed to offspring, unlike dominance (D) and interaction (I) effects, which are disrupted each generation.
How does artificial selection differ from natural selection?
Artificial selection involves humans choosing individuals with desirable traits for breeding to shift population means. Natural selection relies on differential reproductive success based on trait values in the wild.
Why must population-level variation be considered in selection studies?
Selection impacts the trait mean at the population level, requiring an understanding of phenotypic and genetic variance across the population rather than focusing solely on individuals.
What are the components of phenotypic variance (VP)?
G: Genetic variance
VA: Additive genetic variance
VD: Dominance variance
VI: Interaction (epistatic) variance
VE: Environmental variance
Why is additive genetic variance (VA) important for selection?
VA determines how much of the phenotypic variation can respond to selection and contribute to changes in the population mean across generations.
