Questions and Answers
Which of the following are necessary for natural selection to occur? (Select all that apply)
What is directional selection?
An extreme phenotype is favored over others, leading to a shift in allele frequency.
Provide an example of directional selection.
Darwin's finches and beak depth during drought conditions.
What is an example of disruptive selection?
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What is stabilizing selection?
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Give an example of stabilizing selection.
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What defines disruptive selection?
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Study Notes
Natural Selection Requirements
- Variation in traits within a population is essential for natural selection to occur.
- Heritability of traits ensures that variations can be passed down to offspring.
- Certain variations enhance fitness, making them more favorable for survival.
- More offspring are produced than can survive, leading to competition.
- Survivors tend to possess advantageous traits that contribute to their survival.
Directional Selection
- Directional selection occurs when an extreme phenotype is favored, causing a shift in allele frequency within a population.
- This selection type can result in significant evolutionary changes over time.
Directional Selection Example
- The beak depth of Darwin's finches serves as a classic example of directional selection, particularly during drought periods when only large, hard seeds were available, favoring birds with deeper beaks.
Disruptive Selection Example
- In spadefoot toads, tadpoles exhibit disruptive selection through varied diets, where some consume detritus while others prey on small organisms, leading to distinct feeding strategies.
Stabilizing Selection
- Stabilizing selection operates by promoting average phenotypes while selecting against extremes, thereby reducing variation in traits within the population.
Example of Stabilizing Selection
- Birth weight in humans is influenced by stabilizing selection, where infants of average weight have higher survival rates compared to those who are significantly lighter or heavier.
Disruptive Selection
- Disruptive selection favors extreme phenotypes while selecting against average ones, leading to increased diversity within a population by promoting distinct trait variations.
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Description
Explore the fundamental concepts of natural selection, including variation, heritability, and fitness. This quiz also covers types of selection such as directional and disruptive selection, illustrated with examples like Darwin's finches and spadefoot toads. Test your understanding of how these processes contribute to evolutionary changes.
