EvolutionLesson 1 of 1 in the course The Evolution of Populations

Natural Selection: Fitness, Selection Patterns, and Limits to Adaptation

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson explains how natural selection changes populations by affecting the reproductive success of whole organisms. It introduces adaptive evolution and distinguishes absolute fitness from relative fitness.

Natural selection acts on heritable traits—traits influenced by genetic variation that can be passed from parents to offspring. When a heritable trait helps organisms survive and reproduce in a particular environment, the alleles associated with it may become more common over generations. Alleles that reduce reproductive success may become less common.

All flashcards

What is evolutionary fitness?
An organism’s contribution of offspring to the next generation.
What does relative fitness compare?
An individual’s reproductive success with that of others in the same population.
What is sexual dimorphism?
Consistent differences between males and females beyond their reproductive organs.
What does the handicap principle propose?
A costly trait can honestly signal that its bearer is in good condition.
What is Fisherian runaway?
A process in which a trait and preference for it become linked and intensify over generations.

Quiz questions

  1. Which pattern of selection favors distinct phenotypes at two or more extremes while selecting against intermediates?Answer: Diversifying selection
  2. Under negative frequency-dependent selection, which phenotypes tend to gain a fitness advantage?Answer: Phenotypes that are relatively rare
  3. What does sexual selection arise from?Answer: Differences among individuals in success at obtaining mates
  4. How can a costly ornament benefit its bearer under the good genes hypothesis?Answer: It can signal genetic qualities that may benefit offspring.
  5. Why is evolution not necessarily adaptive?Answer: Forces such as genetic drift and gene flow can change allele frequencies without improving adaptation.

Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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