Unit F: Evolution
The Puzzle of Life’s Diversity
1. What did Darwin’s travels reveal to him about the number and variety of living
species?
Darwin’s travels showed him that the diversity of living species was far greater than he
had previously known.
2. How did tortoises and birds differ among the islands of the Galapagos?
Each Galapagos island had its own type of tortoises and birds that were clearly different
from the tortoises and birds on other islands.
3. What is evolution? Why is evolution referred to as a theory?
Evolution, or change over time, is the process by which modern organisms have
descended from ancient ones. Evolution is referred to as a theory because it is a wellsupported explanation of phenomena that have occurred in the natural world.
4. What is a fossil?
A fossil is the preserved remains of an ancient organism.
5. Darwin found fossils of many organisms that were different from any living species.
How
would this finding have affected his understanding of life’s diversity?
It would have greatly increased his estimates of biological diversity.
Interdependence in Nature
In Chapter 5, you learned that both biotic and abiotic factors affect ecosystems. Distinguish
between these two factors, give some examples of each, and explain how they might have
affected the tortoises that Darwin observed on the Galapagos Islands.
Ideas That Shaped Darwin’s Thinking
1. What two ideas from geology were important to Darwin’s thinking?
Earth is very old, and the same processes that shaped Earth millions of years ago continue
in the present.
2. According to Lamarck, how did organisms acquire traits?
Lamarck thought that organisms acquired traits by using their bodies in new ways.
3. According to Malthus, what factors limited population growth?
War, famine and disease
4. How did Lyell’s Principles of Geology influence Darwin?
It suggested Earth was very old and continued to change, allowing time for living things
to change and for evolution to occur.
5. Imagine that you are Thomas Malthus. Write an article describing your ideas.
Explain the impact of a growing population on society and the environment.
Students’ articles will vary. However, students should include that if human population
growth continues to grow unchecked, eventually resources will become scarce.
Science as a Way of Knowing
Describe the idea and observations proposed by Lamarck regarding his theory of evolution.
Include in your description what Lamarck observed and the conclusions he made based on his
observations. In addition, include the scientific evidence that eventually proved Lamarck’s
theory incorrect.
Darwin Presents His Case
1. How is artificial selection dependent on variation in nature?
Nature provides the variation, and humans select the variations that are useful.
2. The theory of evolution by natural selection explains, in scientific terms, how living
things evolve over time. What is being selected in this process.
The traits that help an organism survive in a particular environment.
3. What types of evidence did Darwin use to support his theory of change over time?
The fossil record, geographic distribution of species, homologous structures and
similarities in embryology.
4. Use scientific evidence to evaluate Darwin’s theory of evolution by natural selection.
Scientific advances in many fields of biology, along with geology and physics, have
confirmed most of Darwin’s hypotheses. Specific examples of evidence supporting
Darwin’s theory include similarities in embryology and homologous structures.
Newspaper Article
Write a newspaper article about the meeting in which Darwin’s and Wallace’s hypotheses of
evolution were first presented. Explain the theory of evolution by natural selection for an
audience who knows nothing about the subject.
The Fossil Record
1. What can be learned from the fossil record?
The fossil record provides evidence about the history of life on Earth and how
different groups of organisms changed over time.
2. Which type of dating provides an absolute age for a given fossil? Describe how
this is done.
Radioactive dating provides an absolute age for a given fossil. Scientists calculate the
age of a sample based on the amount of remaining radioactive isotopes it contains.
3. How are eras and periods related?
Periods are subdivisions of the eras of the geologic time scale.
4. How do fossils form?
Most fossils form when dead organisms are covered with layers of sediment.
5. What geologic era is known as the Age of Mammals? When did this era begin?
The Cenozoic Era; 65 million years ago
6. Many more fossils have been found since Darwin’s day, allowing several gaps in
the fossil record to be filled. How might this information make relative dating
more accurate?
More fossils might make relative dating more accurate because the method depends
on comparison of fossils.
Constructing a Timeline
Create a timeline that shows the four main divisions in the geologic time scale and the key events
that occurred during those divisions. Then, as you read Section 17-3, add more events to your
timeline.
Earth’s Early History
1. What substances probably made up Earth’s early atmosphere?
Hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide and
water.
2. What molecules were the end products in Miller and Urey’s experiments?
Amino acids, which are the building blocks of proteins.
3. How did the addition of oxygen to Earth’s atmosphere affect life of that time?
Oxygen drove some life-forms to extinction; others became restricted to oxygen-free
habitats; still others evolved ways of using oxygen for respiration.
4. According to the endosymbiotic theory, how might chloroplasts and mitochondria
have originated?
Ancient aerobic and photosynthetic bacteria may have been engulfed by primitive
eukaryotes and evolved into mitochondria and chloroplasts.
5. You just read that life arose from nonlife billions of years ago. Could life arise from
nonlife today? Explain.
Probably not. The same conditions no longer exist on Earth. The oxygen in the
atmosphere would likely react with and destroy any new kinds of organic molecules or
they would be consumed by bacteria and molds.
Cellular Basis of Life
The endosymbiotic theory accounts for the evolution of mitochondria and chloroplasts in
eukaryotic cells. Review the description of eukaryotic cells in Chapter 7, and then describe the
structure and function of mitochondria and chloroplasts.
Evolution of Multicellular Life
1. Where did life exist during the early Paleozoic Era?
Early life existed in the sea
2. What evolutionary milestone involving animals occurred during the Devonian
Period?
During the Devonian Period, animals began to invade the land.
3. What are two key events from the Mesozoic Era?
Events include the first appearance of dinosaurs and the appearance of seed plants,
including cone-bearing and flowering types.
4. If you were a paleontologist investigating fossils from the Cenozoic Era, what fossils
might you find?
You might find fossils of flowering plants, insects, birds and mammals, including
humans.
Creative Writing
Choose one of the periods described in this section. Then, write a story about life during that
time. Include information about the life-forms, weather and other characteristics.
Patterns of Evolution
1. What is macroevolution? Describe two patterns of macroevolution?
Macroevolution is large-scale evolutionary change over long time periods. Students
should describe any two patterns.
2. What role have mass extinctions played in the history of life?
Mass extinctions periodically wiped out huge numbers of species and made way for the
rapid evolution of new species.
3. What is convergent evolution? Describe an example.
The process by which unrelated organisms, such as dolphins and sharks, come to
resemble one another.
4. How might hox genes contribute to variation?
Hox genes regulate timing of genetic control in the embryo. Even small changes in
timing can cause variation in traits.
5. Compare and contrast the hypotheses of gradualism and punctuated equilibrium.
Gradualism: evolutionary change is slow and steady. Punctuated equilibrium:
evolutionary change occurs in spurts of rapid change after long periods of little change.
Making a Table
Create a table that lists each of the six patterns of macroevolution, explains each pattern, and
gives one example for each. Add a title to your table