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Ch. 24 - The Origin of Species
Campbell - Campbell Biology 12th Edition
Urry12th EditionCampbell BiologyISBN: 9785794169850Not the one you use?Change textbook
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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1
Understand the concept of punctuated equilibria: This model suggests that species experience long periods of stability (equilibria) interrupted by brief periods of rapid change (punctuation).
Identify the key characteristics of punctuated equilibria: Rapid changes occur during speciation events, followed by long periods where species remain relatively unchanged.
Analyze option a: This describes gradualism, where species slowly evolve over time, which contrasts with the punctuated equilibria model.
Evaluate option b: This aligns with the punctuated equilibria model, as it describes rapid changes followed by stability.
Consider options c and d: Sympatric evolution and single mutations are not central to the punctuated equilibria model, which focuses on rapid changes during speciation events.

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Key Concepts

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

Punctuated Equilibria Model

The punctuated equilibria model, proposed by paleontologists Niles Eldredge and Stephen Jay Gould, suggests that species experience long periods of stasis, where little evolutionary change occurs, punctuated by brief, rapid events of speciation. This contrasts with the gradualism model, where species evolve continuously over time. Understanding this model is crucial for interpreting patterns of evolutionary change in the fossil record.
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Introduction to Population Growth Models

Speciation

Speciation is the process by which new species arise from existing ones. It can occur through various mechanisms, such as allopatric, sympatric, or parapatric speciation, often involving genetic divergence and reproductive isolation. In the context of punctuated equilibria, speciation is seen as a rapid event that contributes to the distinct features of new species, followed by periods of little change.
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Allopatric Speciation

Sympatric Populations

Sympatric populations refer to groups of organisms that live in the same geographic area and have the potential to interbreed. Sympatric speciation occurs when new species evolve from a single ancestral species while inhabiting the same region, often through mechanisms like polyploidy or disruptive selection. This concept is important for understanding how speciation can occur without geographic isolation, as mentioned in the question.
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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.

1236
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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

1526
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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.

1419
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Textbook Question

Which of the following factors would be the most likely to contribute to allopatric speciation?

a. The separated population is large, and genetic drift occurs.

b. Selection pressures in the isolated population are similar to those in the ancestral population.

c. Gene flow between the two populations is extensive.

d. Different mutations begin to distinguish the gene pools of the separated populations.

302
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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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