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Ch. 24 - Speciation
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook
Chapter 24, Problem 2

Which of the following describes vicariance?
a. Small populations coalesce into one large population.
b. A population is fragmented into isolated subpopulations.
c. Individuals colonize a novel habitat.
d. Individuals disperse and found a new population.

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1
Understand the concept of vicariance: Vicariance refers to the process by which a population is split into separate groups due to a geographical barrier, leading to isolated subpopulations.
Analyze option a: 'Small populations coalesce into one large population.' This describes the merging of populations, which is the opposite of fragmentation.
Analyze option b: 'A population is fragmented into isolated subpopulations.' This directly describes vicariance, where a geographical barrier causes the division of a population.
Analyze option c: 'Individuals colonize a novel habitat.' This describes colonization, not fragmentation due to a barrier.
Analyze option d: 'Individuals disperse and found a new population.' This describes dispersal and founding, not fragmentation due to a barrier.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Vicariance

Vicariance is a biogeographical process where a species' range is split into isolated subpopulations due to a geographical barrier, such as a mountain range or river. This fragmentation can lead to genetic divergence and speciation as the separated groups adapt to their distinct environments. It contrasts with dispersal, where organisms move across barriers to new areas.
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Speciation

Speciation is the evolutionary process by which populations evolve to become distinct species. It often occurs when populations are isolated, such as through vicariance, leading to genetic differences over time. These differences can result in reproductive isolation, where the populations can no longer interbreed, solidifying their status as separate species.
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Geographical Barriers

Geographical barriers are physical features that divide populations, such as mountains, rivers, or oceans. These barriers prevent gene flow between separated groups, leading to genetic divergence. In the context of vicariance, these barriers are crucial as they create isolated environments where populations can evolve independently.
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