1. Infer A road built through a forest splits a population of frogs into two large groups. The allele frequencies of the two groups are identical. Has genetic drift occurred? Why or why not?

  2. Form a Hypothesis DDT is an insecticide that was first used in the 1940s to kill mosquitoes and stop the spread of malaria. As time passed, people began to notice that DDT became less effective. Explain, in genetic terms, how the insects became resistant to the pesticide.

17.3 The Process of Speciation

Understand Key Concepts

  1. Temporal isolation occurs when two different populations

    1. develop different mating behaviors.

    2. become geographically separated.

    3. reproduce at different times.

    4. interbreed.

  2. When two populations no longer interbreed, what is the result?

    1. genetic equilibrium

    2. reproductive isolation

    3. stabilizing selection

    4. artificial selection

  3. Explain how the different species of Galápagos finches may have evolved.

Think Critically

  1. Relate Cause and Effect Explain why reproductive isolation usually must occur before a population splits into two distinct species.

  2. Form a Hypothesis A botanist identifies two distinct species of violets growing in a field, as shown in the left of the illustration below. Also in the field are several other types of violets that, although somewhat similar to the two known species, appear to be new species. Develop a hypothesis explaining how the new species may have originated.

A two-part diagram showing species of violets growing in a field. The first part shows two species of violets 'Viola pedatifida' and 'Viola sagittata'. The second part shows three other species of violets.

solve the CHAPTER MYSTERY

A tin box containing cough drops.

EPIDEMIC

The genes of flu viruses mutate often, and different strains can swap genes if they infect the same host at the same time. These characteristics produce genetic diversity that enables the virus to evolve. Flu viruses also undergo natural selection. Think of our bodies as the environment for viruses. Our immune system attacks viruses by “recognizing” proteins on the surface of the viruses. Viruses whose proteins our bodies can recognize and destroy have low fitness. Viruses our bodies can't recognize have higher fitness. Viral evolution regularly produces slightly different surface proteins that our immune systems can't recognize right away. These strains evade the immune system long enough to make people sick. That's why you can catch the flu every winter, and why new flu vaccines must be made every year.

An influenza virus.

But now and then, influenza evolution produces radically new molecular “disguises” that our immune systems can't recognize at all. These can be deadly, like the 1918 strain. If a strain like that were to appear today, it could kill many people. That's why researchers are worried about “bird flu”—a strain of flu that can pass from birds, such as chickens, to humans.

  1. Connect to the Explain why mutation and natural selection make developing new flu vaccines necessary every year.

  2. Infer People do not need to receive a new measles vaccination every year. What does this suggest about a difference between flu viruses and the measles virus?

  3. Apply Concepts Can you think of any other issues in public health that relate directly to evolutionary change?

End ofPage 505

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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