17.3 The Process of Speciation

Key Questions

  • What types of isolation lead to the formation of new species?

  • What is a current hypothesis about Galápagos finch speciation?

Vocabulary

  • species

  • speciation

  • reproductive isolation

  • behavioral isolation

  • geographic isolation

  • temporal isolation

Taking Notes

Compare/Contrast Table In a compare/contrast table, describe the three mechanisms of reproductive isolation.

MYSTERY CLUE

A tin box containing cough drops.

A population of viruses inside a host's body is isolated from other viral populations. How might this isolation affect viral evolution?

THINK ABOUT IT How does one species become two? Natural selection and genetic drift can change allele frequencies, causing a population to evolve. But a change in allele frequency by itself does not lead to the development of a new species.

Isolating Mechanisms

What types of isolation lead to the formation of new species?

Biologists define a species as a population or group of populations whose members can interbreed and produce fertile offspring. Given this genetic definition of species, what must happen for one species to divide or give rise to a new species? The formation of a new species is called speciation.

Interbreeding links members of a species genetically. Any genetic changes can spread throughout the population over time. But what happens if some members of a population stop breeding with other members? The gene pool can split. Once a population has thus split into two groups, changes in one of those gene pools cannot spread to the other. Because these two populations no longer interbreed, reproductive isolation has occurred. When populations become reproductively isolated, they can evolve into two separate species. Reproductive isolation can develop in a variety of ways, including behavioral isolation, geographic isolation, and temporal isolation.

An illustration of diverging gene pools.

FIGURE 17–11 Diverging Gene Pools If two populations of a species become reproductively isolated, their gene pools can diverge, producing new species.

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End ofPage 494

Table of Contents

Miller & Levine Biology
About the Authors
Changing the World of Biology Education
Contents
Diversity of Life: A Visual Guide DOL•1–DOL•64
Labs and Activities
Features
UNIT 1 The Nature of Life
1 The Science of Biology
2 The Chemistry of Life
Unit Project
UNIT 2 Ecology
3 The Biosphere
4 Ecosystems and Communities
5 Populations
6 Humans in the Biosphere
Unit Project
UNIT 3 Cells
7 Cell Structure and Function
8 Photosynthesis
9 Cellular Respiration and Fermentation
10 Cell Growth and Division
Unit Project
UNIT 4 Genetics
11 Introduction to Genetics
12 DNA
13 RNA and Protein Synthesis
14 Human Heredity
15 Genetic Engineering
Unit Project
UNIT 5 Evolution
16 Darwin's Theory of Evolution
17 Evolution of Populations
18 Classification
19 History of Life
Unit Project
UNIT 6 From Microorganisms to Plants
20 Viruses and Prokaryotes
21 Protists and Fungi
22 Introduction to Plants
23 Plant Structure and Function
24 Plant Reproduction and Response
Unit Project
UNIT 7 Animals
25 Introduction to Animals
26 Animal Evolution and Diversity
27 Animal Systems I
28 Animal Systems II
29 Animal Behavior
Unit Project
UNIT 8 The Human Body
30 Digestive and Excretory Systems
31 Nervous System
32 Skeletal, Muscular, and Integumentary Systems
33 Circulatory and Respiratory Systems
34 Endocrine and Reproductive Systems
35 Immune System and Disease
Unit Project
A Visual Guide to The Diversity of Life
HOW TO USE THIS GUIDE
THE TREE OF LIFE
Bacteria
Protists
Fungi
Plants
Animals
Appendices
Appendix A Science Skills
Appendix B Lab Skills
Appendix C Technology & Design
Appendix D Math Skills
Appendix E Periodic Table
Glossary
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q, R
S
T
U
V
W
X, Y, Z
Index
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Credits
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