Ch. 15.3 WS

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Name______________________________ Class__________________ Date ______________
Section 15–3 Darwin Presents His Case (pages 378–386)
This section explains the concepts of artificial selection, natural selection,
and fitness. It also describes evidence for evolution.
Publication of On the Origin of Species (pages 378–379)
1. Is the following sentence true or false? When Darwin returned to England, he rushed
to publish his thoughts about evolution.
2. The naturalist whose essay gave Darwin an incentive to publish his own work was
.
3. Circle the letter of each sentence that is true about Darwin’s book, On the Origin
of Species.
a. It was published in 1869.
b. It was ignored when it was first published.
c. It contained evidence for evolution.
d. It described natural selection.
Inherited Variation and Artificial Selection (page 379)
4. Differences among individuals of a species are referred to as .
5. Is the following sentence true or false? Genetic variation is found only in wild
organisms in nature.
6. Circle the letter of each sentence that is true about artificial selection.
a. It is also called selective breeding.
b. It occurs when humans select natural variations they find useful.
c. It produces organisms that look very different from their ancestors.
d. It is no longer used today.
Evolution by Natural Selection (pages 380–382)
7. What was Darwin’s greatest contribution? His greatest contribution was developing a
scientific hypothesis to explain how evolution occurs.
Match each term with its definition.
Terms
c 8. fitness
a 9. adaptation
b 10. natural selection
false
variation
Alfred Russel Wallace
false
Definitions
a. Any inherited characteristic that increases an
organism’s chance of survival
b. Survival of the fittest
c. The ability of an individual to survive and
reproduce in its specific environment
BIO_ALL IN1_StGd_tese_ch15 8/7/03 5:14 PM Page 321

Name______________________________ Class__________________ Date ______________
11. What does the phrase struggle for existence mean? It means that members of each
species compete regularly to obtain food, living space, and other necessities of life.
12. Is the following sentence true or false? Adaptations can be physical characteristics but
not more complex features such as behavior.
13. Explain what Darwin meant by the phrase survival of the fittest. Individuals that are
better suited to their environment survive and reproduce most successfully.
14. Circle the letter of each sentence that is true about natural selection.
a. It selects traits that increase fitness.
b. It takes place without human control.
c. It can be observed directly in nature.
d. It leads to an increase in a species’ fitness.
15. The principle that living species descend, with changes, from other species over time is
referred to as .
16. The principle that all species were derived from common ancestors is known as
.
Evidence of Evolution (pages 382–385)
17. Is the following sentence true or false? Darwin argued that living things have been
evolving on Earth for thousands of years.
18. Complete the concept map.
false
common descent
descent with modification
false
19. How do fossils that formed in different rock layers provide evidence of evolution?
They document the fact that life on Earth has changed over time.
Evidence for
Evolution
can be found in
The fossil record
The geographic
distribution of living
species
Homologous
structures of living
organisms
Similarities in
embryology

Name______________________________ Class__________________ Date ______________
20. Circle the letter of the way Darwin explained the distribution of finch species on the
Galápagos Islands.
a. They had descended with modification from a common mainland ancestor.
b. They had descended with modification from several different mainland ancestors.
c. They had remained unchanged since arriving on the Galápagos from the mainland.
d. They had become more similar to one another after arriving on the Galápagos.
21. How did Darwin explain the existence of similar but unrelated species?
Darwin thought that such species evolved features in common because they were
exposed to similar pressures of natural selection.
22. Structures that have different mature forms but develop from the same embryonic
tissues are called .
23. Is the following sentence true or false? Homologous structures provide strong evidence
that all four-limbed vertebrates have descended, with modifications, from common
ancestors.
24. Organs that are so reduced in size that they are just vestiges, or traces, of homologous
organs in other species are called .
Summary of Darwin’s Theory (page 386)
25. Circle the letter of each idea that is part of Darwin’s theory of evolution.
a. There is variation in nature.
b. Fewer organisms are produced than can survive.
c. There is a struggle for existence.
d. Species change over time.
26. According to Darwin’s theory, what happens to individuals whose characteristics are
not well suited to their environment? Such individuals die or leave fewer offspring.
27. Darwin believed that all organisms on Earth are united into a single tree of life by
.
Evolutionary Theory Since Darwin (page 386)
28. What is the status of Darwin’s hypotheses today? They have been confirmed and
expanded by scientific advances in biology, geology, and physics.
descent with modification
vestigial organs
true
homologous structures

a r t i f i c i a l
o
f i t n e s s s
h s
e v o l u t i o n
o l a v
r s t e
y u s
r t
c a i
h o m o l o g o u s
m i
m a
o l
a d a p t a t i o n
Name______________________________ Class__________________ Date ______________
WordWise
Test your knowledge of vocabulary terms from Chapter 15 by completing this
crossword puzzle.
Clues across:
1. The type of selection that humans
control
3. The ability to survive and reproduce in
a specific environment
5. Change over time
9. The kind of structures that have
different mature forms but develop
from the same embryonic tissues
10. Any inherited characteristic that
increases an organism’s chance of
survival
Clues down:
2. The preserved remains of ancient
organisms
4. A well-supported explanation of
phenomena that have occurred in the
natural world
6. The type of selection that increases an
organism’s fitness in its environment
7. The kind of organs that are so reduced in
size they are just traces of homologous
organs in other species
8. The type of descent that explains why all
species are linked in a single tree of life
1 2
3 4
5 6
7
8
9
10

Ch. 15.3 WS

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