Book cover for Biology

Biology

Sylvia S. Mader, Michael Windelspecht

ISBN #9780078024269

12th Edition

687 Questions

Group icon
153,501 Students Helped

Homework Questions

Right arrow
Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

Chapter 17 explores how new species evolve through macroevolution, emphasizing that species formation is a gradual process driven by the accumulation of microevolutionary changes. It discusses different species concepts, the mechanisms of reproductive isolation, and the modes of speciation—particularly allopatric and sympatric speciation. Insights from genetic studies, such as those on Darwin’s finches, reinforce the dynamic nature of evolution influenced by natural selection and environmental factors, highlighting that evolution is not goal-directed.

Learning Objectives

1

Describe the concept of macroevolution and how it arises from the accumulation of microevolutionary changes.

2

Explain various species concepts including morphological and phylogenetic approaches.

3

Differentiate between modes of speciation, particularly allopatric and sympatric speciation.

4

Analyze the role of reproductive isolation and genetic studies (e.g., Darwin’s finches) in species formation.

5

Discuss how natural selection and environmental pressures influence evolutionary processes without a predetermined direction.

Key Concepts

CONCEPT

DEFINITION

Macroevolution

The process of evolution that leads to the formation of new species through the gradual accumulation of microevolutionary changes.

Microevolution

Small-scale evolutionary changes within a species, such as mutations and genetic drift, that can eventually lead to macroevolution.

Species Concept

A set of criteria used to define a species, including morphological (form and structure) and phylogenetic (evolutionary relationships) concepts.

Reproductive Isolation

Mechanisms that prevent different species from interbreeding, contributing to the formation of new species.

Allopatric Speciation

Speciation that occurs when biological populations are physically isolated by geographic barriers.

Sympatric Speciation

Speciation that occurs without physical separation, often through genetic divergence within a shared habitat.

Natural Selection

A key mechanism of evolution where organisms better adapted to their environment tend to survive and reproduce.

Gene Expression Adjustments

Changes in the way genes are expressed that can lead to differences in morphological traits among species.

Example Problems

Example 1

Which of the following events is part of macroevolution? a. speciation b. mutation c. gene flow d. natural selection e. All of these are correct.

Example 2

A biological species a. always looks different from other species. b. always has a different chromosome number than that of other species. c. is reproductively isolated from other species. d. never occupies the same niche as other species. e. does not survive long in the wild.

Example 3

Which of these is a prezygotic isolating mechanism? a. habitat isolation b. temporal isolation c. hybrid sterility d. zygote mortality e. Both a and b are correct

Example 4

Male moths recognize females of their species by sensing chemical signals called pheromones. This is an example of a. gamete isolation. b. habitat isolation. c. behavorial isolation. d. mechanical isolation. e. temporal isolation.

Example 5

Which of these is an example of mechanical isolation? a. Sperm cannot reach or fertilize an egg. b. Courtship patterns differ. c. Organisms live in different locales. d. Organisms reproduce at different times of the year. e. Genitalia are unsuitable to each other.
Scroll left
Scroll right

Step-by-Step Explanations

QUESTION

How does the accumulation of microevolutionary changes lead to the formation of a new species?

STEP-BY-STEP ANSWER:

Step 1: Understand that microevolution involves small genetic changes within a population over time through mutation, genetic drift, and gene flow.
Step 2: Recognize that when these changes accumulate, they can significantly alter the genetic makeup of a population.
Step 3: Identify that reproductive isolation mechanisms, such as geographic separation (allopatric speciation) or ecological differences (sympatric speciation), prevent gene flow between populations.
Step 4: Conclude that due to the absence of genetic exchange, the isolated populations diverge further, eventually resulting in the formation of distinct species.
Final Answer: The gradual accumulation of microevolutionary changes, coupled with reproductive isolation, leads to speciation.

Speciation Process

QUESTION

What are the differences between allopatric and sympatric speciation?

STEP-BY-STEP ANSWER:

Step 1: Define allopatric speciation as the process where a population becomes geographically separated, leading to genetic divergence.
Step 2: Define sympatric speciation as the process where new species arise within the same geographic area, often due to ecological or behavioral differences.
Step 3: Note that in allopatric speciation, physical barriers such as mountains or rivers initiate isolation, whereas in sympatric speciation, factors like resource competition or differing mating preferences can drive divergence.
Step 4: Understand that both processes ultimately lead to reproductive isolation and the emergence of new species.
Final Answer: Allopatric speciation occurs due to physical geographic barriers, while sympatric speciation occurs within a shared habitat due to ecological or behavioral differences.

Modes of Speciation

QUESTION

How do genetic studies, such as those on Darwin’s finches, enhance our understanding of speciation?

STEP-BY-STEP ANSWER:

Step 1: Recognize that genetic studies analyze variations in gene expression and genetic makeup among populations.
Step 2: Observe that research on Darwin’s finches shows how genetic differences can lead to variations in beak shape and size which are adaptations to different ecological niches.
Step 3: Understand that these genetic changes are evidence of natural selection acting on microevolutionary traits.
Step 4: Conclude that genetic studies provide concrete examples of how small changes can accumulate and result in the formation of new species.
Final Answer: Genetic studies demonstrate that changes in gene expression contribute to morphological adaptations, thereby clarifying the process of speciation driven by natural selection.

Role of Genetic Studies in Evolution

Scroll left
Scroll right

Common Mistakes

  • Confusing microevolution with macroevolution, when the latter represents long-term, large-scale evolutionary changes.
  • Assuming that speciation is a directed or intentional process rather than a dynamic outcome of genetic and environmental interactions.
  • Overlooking the importance of reproductive isolation mechanisms in the formation of new species.
  • Failing to differentiate between the various species concepts and their implications for understanding biodiversity.