Ch. 24 - Speciation

Freeman - Biological Science 8th Edition

Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook

Freeman 8th Edition

Ch. 24 - Speciation

Problem 5

Chapter 24, Problem 5

When the ranges of two different species meet, a stable 'hybrid zone' occupied by hybrid individuals may form. How is this possible?
a. Two diverged populations are capable of mating and producing viable and fertile offspring.
b. Hybrid individuals are always allopolyploid and are thus unable to mate with either of the original species.
c. Hybrid individuals may have reduced fitness and thus be strongly selected against.
d. One species has a selective advantage, so as hybridization continues, the other species will go extinct.

Verified step by step guidance

Understand the concept of a hybrid zone: A hybrid zone is a region where two different species meet and interbreed, producing hybrid offspring. This occurs when the ranges of the two species overlap.

Consider option a: Two diverged populations are capable of mating and producing viable and fertile offspring. This suggests that the hybrid individuals are able to survive and reproduce, maintaining the hybrid zone.

Evaluate option b: Hybrid individuals are always allopolyploid and are thus unable to mate with either of the original species. Allopolyploidy refers to having multiple sets of chromosomes from different species, which can affect the ability to reproduce with parent species.

Analyze option c: Hybrid individuals may have reduced fitness and thus be strongly selected against. Reduced fitness means hybrids might not survive or reproduce as well as purebred individuals, potentially limiting the hybrid zone.

Consider option d: One species has a selective advantage, so as hybridization continues, the other species will go extinct. This implies that hybridization could lead to the dominance of one species over the other, affecting the stability of the hybrid zone.

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Key Concepts

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

Hybrid Zone

A hybrid zone is a geographic area where two distinct species meet and interbreed, producing hybrid offspring. These zones are often stable and can persist over time if the hybrids have some level of fitness that allows them to survive and reproduce. The stability of a hybrid zone depends on various factors, including the relative fitness of the hybrids compared to the parent species.

Hybrid Fitness

Hybrid fitness refers to the ability of hybrid individuals to survive and reproduce in their environment. In a hybrid zone, hybrids may have reduced fitness compared to their parent species, which can lead to strong selection against them. However, if hybrids possess certain advantageous traits, they may thrive, contributing to the stability of the hybrid zone.

Allopolyploidy

Allopolyploidy is a condition in which an organism contains two or more sets of chromosomes derived from different species. This can occur in hybrids, making them unable to mate with either parent species due to differences in chromosome number. While allopolyploid hybrids are often sterile, they can sometimes undergo genetic changes that restore fertility, allowing them to establish as a new species.

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Polyploidy

Related Practice

Textbook Question

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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Textbook Question

Select True or False to indicate which of the following groups could be identified using the biological species concept.

T/F lizard species living today

T/F sunflower species living today

T/F extinct dinosaurs

T/F bacteria living today

Textbook Question

Evaluate this statement: Gene flow increases the genetic divergence of populations.

Textbook Question

Sexual selection favors individuals with traits that increase their ability to obtain mates, such as mating calls in crickets. Using this example, propose a scenario where sexual selection could contribute to divergence in sympatric speciation.

Textbook Question

If one species (2n = 10) crosses with another species (2n = 18), producing an allopolyploid offspring, what is the ploidy of the offspring?

a. 2n = 10

b. 2n = 18

c. 2n = 10+18 = 28

d. 4n = 36 +20 = 56

Textbook Question

True or false? Speciation is a slow process. Justify your answer.