EvolutionLesson 3 of 3 in the course Evolution and the Origin of Species

Hybrid-Zone Outcomes and Models of Speciation Rates

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

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Summary

Speciation takes place over evolutionary time. During the transition, closely related species may encounter one another and reproduce, while populations may also diverge at different rates. This lesson explains how interactions between newly diverged species can lead to reinforcement, fusion, or stability, and compares two models of the pace of speciation.

All flashcards

What is a hybrid zone?
An area where closely related species interact and reproduce, producing hybrid offspring.
What is reinforcement?
A process in which low-fitness hybrids favor stronger reproductive barriers, causing the parent species to diverge further and making hybridization less likely.
What are fusion and stability?
Fusion occurs when weakened reproductive barriers and interbreeding cause two species to merge. Stability occurs when species remain distinct while hybridization continues without major net change.
How do gradual speciation and punctuated equilibrium differ?
Gradual speciation involves divergence through small changes over time. Punctuated equilibrium describes relatively rapid change followed by long periods of comparatively little change.
How can environmental change influence speciation?
Environmental change can alter which traits improve survival and reproduction. If a population becomes isolated, helpful heritable variations may become more common and the population may diverge from others.

Quiz questions

  1. What is a hybrid zone?Answer: An area where closely related species interact and reproduce, producing hybrids.
  2. Which outcome can occur when low-fitness hybrids lead to selection for stronger reproductive barriers?Answer: Reinforcement, with greater divergence and less hybridization between the species.
  3. What characterizes fusion between two closely related species?Answer: Weakened reproductive barriers allow interbreeding and gene flow to merge the populations.
  4. Which pattern is described by punctuated equilibrium?Answer: Relatively rapid evolutionary change is followed by long periods of comparatively little change.
  5. What best describes gradual speciation?Answer: Populations diverge through many small changes accumulated over a long period.

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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