Book cover for Campbell Biology Concepts & Connections

Campbell Biology Concepts & Connections

Martha R. Taylor, Jean L. Dickey, Eric J. Simon, Kelly Hogan, Jane B. Reece

ISBN #9780134296012

9th Edition

631 Questions

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82,520 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This chapter delves into the origin of species, emphasizing evolution by natural selection as the foundational process driving biological diversity. It distinguishes between microevolution, which involves small changes within populations, and speciation, where new species emerge through mechanisms like allopatric and sympatric speciation. The chapter further explores how reproductive barriers and sexual selection contribute to divergent evolution, while real-world examples such as Darwin's finches, cichlid fishes, laboratory experiments, and fossil evidence underscore both gradual and punctuated patterns of evolutionary change.

Learning Objectives

1

Explain evolution by natural selection and its role in generating biological diversity.

2

Differentiate between microevolution and speciation and understand how small genetic changes can lead to new species.

3

Identify and analyze the mechanisms of allopatric and sympatric speciation, including the role of geographic isolation, ecological niches, and sexual selection.

4

Evaluate the evidence for evolutionary processes using real-world examples such as Darwin's finches, cichlid fishes, laboratory experiments, and fossil records.

5

Understand the importance of reproductive barriers in maintaining species distinctions and facilitating divergent evolution.

Key Concepts

CONCEPT

DEFINITION

Evolution

A process in which heritable traits in populations change over generations, leading to the diversity of life.

Natural Selection

A mechanism of evolution where organisms with advantageous traits tend to survive and reproduce, passing those traits on to the next generation.

Microevolution

Small-scale genetic changes within a population that may result in variations over time.

Speciation

The process by which populations evolve to become distinct species, often as a result of reproductive isolation.

Allopatric Speciation

A mode of speciation that occurs when populations of a species become geographically isolated, leading to the evolution of reproductive barriers.

Sympatric Speciation

A type of speciation that occurs without geographic separation, often driven by genetic, ecological, or behavioral differences within a population.

Adaptive Radiation

The rapid evolution of diversely adapted species from a common ancestor, usually in response to new environmental opportunities.

Reproductive Barriers

Biological features or behaviors that prevent different species from interbreeding, thereby maintaining their distinctiveness.

Sexual Selection

A mechanism of evolution where traits that affect an organism’s ability to attract and mate with partners become more common in a population.

Example Problems

Example 1

Name the two types of speciation represented by this diagram. For each type, describe how reproductive barriers may develop between the new species. (FIGURE CAN'T COPY)

Example 2

Fill in the blanks in the following concept map. (FIGURE CAN'T COPY)

Example 3

Which concept of species would be most useful to a field biologist identifying new plant species in a tropical forest? a. biological b. ecological c. morphological d. phylogenetic

Example 4

According to the biological species concept, species are defined by their a. particular roles in a biological community. b. ability to interbreed and produce viable, fertile offspring. c. reproductive isolation from nearby populations. d. common ancestry.

Example 5

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species that lived side by side in parts of their ranges. However, recent books show them as eastern and western forms of a single species, the yellow-rumped warbler. Most likely, it has been found that these two kinds of warblers a. live in similar habitats and eat similar foods. b. interbreed often in nature, and the offspring are viable and fertile. c. are almost identical in appearance. d. have many genes in common.
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Step-by-Step Explanations

QUESTION

How does geographic isolation lead to allopatric speciation?

STEP-BY-STEP ANSWER:

Step 1: Identify a geographic barrier (e.g., mountains, rivers, islands) that separates a population into distinct groups.
Step 2: Recognize that this isolation prevents gene flow between the separated groups.
Step 3: Observe that each group undergoes independent genetic changes (microevolution) due to mutation, genetic drift, and natural selection.
Step 4: Over time, these genetic changes accumulate, eventually leading to reproductive isolation and the formation of new species.
Final Answer: Geographic isolation results in distinct evolutionary paths for separated populations, eventually leading to speciation.

Allopatric Speciation

QUESTION

How can new species form without geographic isolation?

STEP-BY-STEP ANSWER:

Step 1: Understand that within the same geographical area, different subgroups may exploit different ecological niches or resources.
Step 2: Recognize that genetic variations, possibly due to mutations and variations in mating behavior, can lead to reproductive isolation.
Step 3: Note that sexual selection and ecological factors can further reinforce these differences over time.
Final Answer: Sympatric speciation occurs when reproductive isolation develops within a single population, leading to the formation of distinct species without geographic separation.

Sympatric Speciation

QUESTION

What role do reproductive barriers play in speciation?

STEP-BY-STEP ANSWER:

Step 1: Identify various types of reproductive barriers like behavioral, temporal, mechanical, and gametic isolation.
Step 2: Explain that these barriers prevent interbreeding between populations or individuals even if they live in the same area.
Step 3: Show that when such barriers are in place, even genetically similar populations become reproductively isolated.
Final Answer: Reproductive barriers maintain species boundaries by preventing gene flow between divergent populations, thereby facilitating speciation.

Reproductive Barriers

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Common Mistakes

  • Confusing microevolution (small genetic changes) with speciation (the formation of new species).
  • Assuming that geographic isolation is the only way new species can form, thus overlooking sympatric speciation.
  • Underestimating the role of reproductive barriers and sexual selection in maintaining species differences.
  • Overlooking the significance of laboratory experiments and fossil records as concrete evidence for both gradual and punctuated evolutionary changes.