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Ch. 24 - The Origin of Species
Chapter 24, Problem 3

According to the punctuated equilibria model, a. given enough time, most existing species will branch gradually into new species. b. most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species. c. most evolution occurs in sympatric populations. d. speciation is usually due to a single mutation.

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The punctuated equilibria model is a concept in evolutionary biology that proposes that once a species appears in the fossil record, the population will become stable, showing little evolutionary change for most of its geological history. This process is called stasis. When significant evolutionary change occurs, the theory proposes that it is generally restricted to rare and geologically rapid events of branching speciation.
Option a is incorrect. The punctuated equilibria model does not suggest that most existing species will branch gradually into new species. Instead, it proposes that changes happen in quick, rare events rather than gradually over time.
Option b is correct. According to the punctuated equilibria model, most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.
Option c is incorrect. The punctuated equilibria model does not specifically state that most evolution occurs in sympatric populations. Sympatric speciation is a concept in evolution that refers to the process through which new species evolve from a single ancestral species while inhabiting the same geographic region.
Option d is incorrect. The punctuated equilibria model does not suggest that speciation is usually due to a single mutation. Instead, it proposes that speciation occurs rapidly in a geologically short period.

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Key Concepts

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

Punctuated Equilibria

Punctuated equilibria is a theory in evolutionary biology that suggests species remain relatively stable for long periods, punctuated by brief, rapid changes during speciation events. This model contrasts with gradualism, which posits that evolution occurs slowly and steadily over time. The punctuated equilibria model emphasizes the role of environmental changes and isolated populations in driving rapid evolutionary changes.
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Speciation

Speciation is the evolutionary process by which populations evolve to become distinct species. It can occur through mechanisms such as allopatric speciation, where geographic barriers lead to reproductive isolation, or sympatric speciation, where new species arise within the same geographic area. Understanding speciation is crucial for grasping how biodiversity arises and evolves over time.
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Evolutionary Change

Evolutionary change refers to the alterations in the genetic composition of populations over generations, leading to adaptations and the emergence of new species. This change can be gradual or occur in bursts, as suggested by the punctuated equilibria model. Factors influencing evolutionary change include natural selection, genetic drift, and mutations, which can introduce new traits into a population.
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Related Practice
Textbook Question

The largest unit within which gene flow can readily occur is a a. population. b. species. c. genus. d. hybrid.

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Textbook Question

Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other males and making stylized movements that attract females. What type of reproductive isolation does this represent? a. habitat isolation b. temporal isolation c. behavioral isolation d. gametic isolation

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Textbook Question

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification? a. The two forms interbreed often in nature, and their offspring survive and reproduce well. b. The two forms live in similar habitats and have similar food requirements. c. The two forms have many genes in common. d. The two forms are very similar in appearance.

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Textbook Question

Which of the following factors would not contribute to allopatric speciation? a. The separated population is small, and genetic drift occurs. b. The isolated population is exposed to different selection pressures than the ancestral population. c. Different mutations begin to distinguish the gene pools of the separated populations. d. Gene flow between the two populations is extensive.

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Textbook Question

Plant species A has a diploid chromosome number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be a. 14. b. 16. c. 28. d. 56.

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