Download 16.4 Evidence of Evolution

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16.4 Evidence of Evolution
Lesson Objectives
Explain how geologic distribution of species relates to their evolutionary history.
Explain how fossils and the fossil record document the descent of modern species from
ancient ancestors.
Describe what homologous structures and embryology suggest about the process of
evolutionary change.
Explain how molecular evidence can be used to trace the process of evolution.
Explain the results of the Grants’ investigation of adaptation in Galápagos finches.
Lesson Summary
Biogeography Biogeography is the study of where organisms live now and where they and
their ancestors lived in the past. Two biogeographical patterns are significant to Darwin’s theory:
▶ The first is a pattern in which closely related species differentiate in slightly different
climates. The Galápagos tortoises and finches follow this pattern.
▶ The second is a pattern in which very distantly related species develop similarities in
similar environments. The rheas, ostriches, and emus fall into this pattern.
The Age of Earth and Fossils
▶ Radioactive dating techniques have confirmed that Earth is ancient—approximately
4.5 billion years old.
▶ Recent fossil finds document intermediate stages in the evolution of many groups
including whales, birds, and mammals.
Comparing Anatomy and Embryology
▶ Homologous structures are shared by related species and have been inherited from
a common ancestor. Similarities and differences among homologous structures help
determine how recently two groups shared a common ancestor.
• Body parts that share a common function, but neither structure nor common ancestry,
are called analogous structures. Analogous structures do not provide any evidence for
evolutionary descent.
• Homologous structures that are greatly reduced in size or have little to no function are
called vestigial structures.
• Many homologous structures develop in the same order and in similar patterns during
the embryonic, or pre-birth, stages of related groups. These similarities provide further
evidence that the animals share common ancestors.
Genetics and Molecular Biology At the molecular level, the universal genetic code and
homologous molecules such as genes and proteins provide evidence of common descent.
Testing Natural Selection Scientists have designed experiments to test natural selection.
Observations of Galápagos finches confirm that competition and environmental change drive
natural selection.
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Biogeography
For Questions 1–3, complete each statement by writing the correct word or words.
1. Biogeographers study where organisms live now and where they and their
ancestors
lived in the past.
2. When individuals from a mainland bird population immigrate to various islands, natural
selection may result in closely related , but different, island species.
3. Distantly related organisms may be similar if they live in similar environments .
4. What explains the distribution of finch species on the Galápagos Islands?
The finch species had descended with modification from a common mainland
ancestor.
5. What explains the existence of similar but unrelated species?
Such species evolved features in common because they were exposed to similar pressures of natural selection.
The Age of Earth and Fossils
6.
The illustrations below show organisms whose fossils make up part
of the fossil record. The organisms are in order from oldest to most recent. In the boxes,
draw an animal that might have been an intermediate form between the shown organisms.
Answers will vary. Students’ drawings
may show a slightly elongated shell
and/or slightly longer tentacles.
Answers will vary. Students’ drawings
may show a somewhat more coiled shell.
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Use the illustrations of the marine organisms on the previous page to answer Questions 7–8.
7. Describe a situation in which organism 3 might have had an advantage over organism 2?
SAMPLE ANSWER:
Having a more compact body may have made it easier for the organism
to escape predators.
8. How might these fossils provide evidence for evolution?
They show similarities to one another, but they also show changes that have occurred
over time.
Comparing Anatomy and Embryology
9. Complete the table about types of anatomical structures.
Types of Anatomical Structures
Structure Type
Description
Example
Homologous
structure
Structures that are shared by related
species and that have been inherited
from a common ancestor
Mammalian leg and
amphibian leg
Analogous
structure
Body parts that share common function, but Wing of a bee and wing
not structure
of a bird
Vestigial structure
Body parts in animals that are so reduced
in size that they are just vestiges, or traces,
of homologous structures in other species
Hipbones in dolphins
For Questions 10–14, match the structure with the correct type. A structure type may be used
more than once.
Anatomical Structure
Structure Type
A
10. bat wing and mouse arm
A. homologous structure
A
11. reptile foot and bird foot
B. analogous structure
B
12. dolphin fin and fish tail
C. vestigial structure
C
13. eyes on a blind cave fish
B
14. snake tongue and dog nose
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Use the illustrated homologous structures to answer Questions 15–17.
Humerus
Radius/Ulna
Carpals (wrist bones)
Metacarpals/Phalanges
(finger bones)
Bat forelimb
Human forelimb
15. How are the forelimbs similar?
The forelimbs have the same kinds of bones in approximately the same positions.
16. How are the forelimbs different?
SAMPLE ANSWER:
The bat’s “finger bones” are elongated and form the structure of a
wing, while the human phalanges are shorter and form the structure for fingers.
17. How are homologous structures such as forelimbs evidence for common descent?
The bones are noticeably similar in structure and arrangement. It is, therefore,
reasonable to assume that they are descended from a common ancestral form.
18. How does the pattern of embryological development provide further evidence that
organisms have descended from a common ancestor?
The early developmental stages of many vertebrates look very similar. Therefore,
it is reasonable to assume that vertebrates are descended from a common ancestor.
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Genetics and Molecular Biology
For Questions 19–25, complete each statement by writing the correct word or words.
genetics
19. The science of
theory.
provides molecular evidence that supports evolutionary
DNA
20. All living cells use
RNA
and
to code heritable information.
21. The universal genetic code is used by almost all organisms to
22. Proteins that are
homologous
direct protein synthesis .
share extensive structural and chemical similarities.
23. Cytochrome c is a protein used for cellular respiration in almost every living cell.
24. Homologous genes called Hox genes control timing and growth in
embryos
.
25. Relatively minor changes in an organism’s genome can produce major changes in an
organism’s
structure
.
Testing Natural Selection
Write the letter of the correct answer on the line at the left.
A
26. Which of the following hypotheses did the Grants test?
A. Differences in beak size and shape produce differences in fitness.
B. For beak size and shape to evolve, the birds must leave the islands.
C. For beak size and shape to evolve, the climate must change radically.
D. Differences in beak size and shape are not determined by genetic mutations.
C
27. The data that the Grants collected proved that there is
A. no link between the environment and the shape of finch feet.
B. no link between the environment and the shape of finch beaks.
C. great variation of heritable traits among Galápagos finches.
D. very little variation of heritable traits among Galápagos finches.
A
28. The Grants conducted their experiment to test which of the following
processes?
A. Natural selection
B. Genetic mutation
C. Artificial selection
D. Sexual reproduction
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29.
Class
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The art shows how finch beaks are similar to certain kinds of hand
tools. Suppose a finch fed on insects that burrowed into small holes on tree trunks. What
type of tool do you think this finch’s beak would resemble? Explain your answer.
Ground Finches
Tree Finches
Pinaroloxias
Platyspiza
Geospiza
Certhidea
SAMPLE ANSWER:
The finch’s beak might resemble a very thin probe that can reach into a
small hole and skewer or grasp the insect.
30. Complete the concept map.
Evidence for
Evolution
i l d
includes
the
geographic
distribution of
living species
the fossil
record
similarities in
anatomical
structures and
embryological
development
the universal genetic
code and
homologous
proteins and
genes
experiments
that verify
natural
selection
occurs in
nature
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Chapter Vocabulary Review
Match the term with its definition.
Term
Definition
A
1. evolution
A. Change over time
C
2. fossil
G
3. fitness
B. Inherited characteristic that increases an
organism’s chance of survival
B
4. adaptation
D
5. natural selection
F
6. homologous structures
E
D. The process by which organisms with variations
most suited to their environment survive and
leave more offspring than others
7. vestigial structures
E. Small structures with little or no function
C. Preserved remains of an ancient organism
F. Structures that develop from the same embryonic
tissues but have different mature forms
G. Ability of an individual to survive and reproduce
in a specific environment
For Questions 8–10, write a definition for the vocabulary term.
8. biogeography
the study of where organisms live now and where they and their ancestors lived in the
past
9. artificial selection
the use of selective breeding to produce organisms with certain desirable traits
10. analogous structures
body parts that share common function, but not structure
11. Does the illustration below show analogous or homologous structures? Explain.
Turtle
Alligator
Bird
Mammals
Homologous structures. These limbs evolved from the front limbs of a common ancestor. If these animals had different origins, they would probably not share so many
common structures.
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“The Chapter Mystery explained how the
’i’iwi and other Hawaiian honeycreeper
species evolved adaptations suited to their
specific habitats. What happens when
species face a loss of their habitats due to
urbanization or environmental degradation?
SUCH VARIED
HONEYCREEPERS
Learning
Habitat Loss and Endangered Species
Scientists report that in the United States, habitat loss is the most widespread cause of
species endangerment, affecting approximately 85 percent of imperiled species according to
a recent estimate. Designed to combat the problem, the U.S. Endangered Species Act of 1973
is a federal law that protects threatened and endangered species. When a species is listed as
endangered, the government enforces more stringent protections on the species’ remaining
habitats, especially when those habitats are on federal lands. In addition, the Act allows the
government to purchase land containing important habitats and forbids the capture, killing,
or sale of an endangered species. In addition, people who violate the Act can be prosecuted.
Unfortunately, threats to many species continue. Experts believe that fewer than half the
species native to the United States—especially insect, plant, and fungi species—have yet been
discovered and catalogued. Therefore, it is impossible to know whether these species are
endangered. Another problem, other scientists emphasize, is that the regulations protecting
endangered species are not effective enough and are based on an underestimation of the
problem. One recent expert analysis suggests that, even within the pool of known species, the
number now threatened with extinction may actually be as much as ten times greater than the
number currently protected under the U.S. Endangered Species Act.
The table below, adapted from data compiled by the nonprofit scientific group
NatureServe, assesses the current situation for vertebrate species in the United States.
Vertebrate Species Data in the U.S.
Group: Imperiled
U.S. Vertebrates
Total Number of
Known Species
Number of Species
Imperiled or Extinct/
Possibly Extinct
Percentage of Species
Imperiled or Extinct/
Possibly Extinct
Mammals
421
29
7
Birds
783
75
10
Reptiles
295
28
9
Amphibians
258
66
26
Freshwater Fishes
798
179
22
Vertebrate Totals
2555
377
15
Continued on next page ▶
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Science and Global
Awareness
1. What is believed to be the most widespread cause of species endangerment?
Habitat loss is the most widespread cause.
2. According to the table, which group of vertebrates in the United States includes the largest
number of imperiled or extinct species?
Freshwater fish species, with 179 varieties imperiled or extinct
3. According to the table, which group of vertebrates appears to be most endangered overall?
How can you tell? Why do you think this group is most imperiled?
Amphibians are the most endangered group because they have the highest percentage
of species imperiled or extinct of any of the vertebrate groups. Students may be able
to draw a connection between the imperilment of amphibian species and the vulnerability of their wetland ecosystems.
4. What is the U.S. Endangered Species Act?
Enacted in 1973, the U.S. Endangered Species Act is a law that designates threatened
and endangered species and offers federal protection to the listed species’ habitats.
5. Some experts think that a significant number of species native to the United States have yet
to be discovered. Some experts think that the U.S. Endangered Species Act underestimates
the number of endangered species. How does the first problem lead to the second?
The U.S. Endangered Species Act cannot protect species that have yet to be identified.
Meanwhile, habitat destruction and possible extinction of species continue.
Species Presentation
The skills used in this activity include information and media literacy; critical thinking and
systems thinking; and problem identification, formulation, and solution.
Visit the Web site of the U.S. Fish and Wildlife Service to learn more about the agency’s
efforts to protect endangered species in the United States. Choose one endangered species
and investigate the threats it faces. Present the information to the class, including whether
you believe the species deserves protection under the Act and, if so, why.
Your presentation can be in the form of a video about the species or an illustrated guide.
Evaluate students’ presentations by their inclusion of the description of the species and
the threats it faces, its habitat range, what is being done to protect the species, and
their opinion. Evaluation should also depend on the appropriate use of available media.
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