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                 Bi 12                 Ch 13 Study Guide: Evolution
In this section you were introduced to the concept of evolution. Evolution is the process by which modern
organisms have descended from ancient organisms. In other words, evolution is change over time.
The person who contributed the most to our understanding of the process of evolution is Charles Darwin. When
 Darwin was 22 years old, he set off on a 5-year voyage around the world on H.M.S. Beagle. On this voyage,
Darwin observed a multitude of living things as well as the remains of ancient organisms. His observations
inspired him to solve the riddles of life’s diversity.
Where did the different kinds of living things come from? Why have many kinds of living things vanished over
time? Why are modern organisms similar to – and different from – ancient organisms? Why are organisms so well
designed to do the things they need to do to survive? Many years after his voyage on H.M.S. Beagle, Darwin
proposed answers to these questions in his book, on the Origin of Species by Means of Natural Selection.
In On the Origin of Species, Darwin maintained that modern organisms have been produced through evolution
from ancient organisms and all species have common ancestors. Darwin also proposed a mechanism to explain
exactly how and why evolution occurs.


Matching Terms: Building Vocabulary Skills
In the space provided, write the term that best fits each definition. Some terms may be used more than once.

1.   Process that results in fitness                                       Adaptation

2.   The combination of physical traits and behaviors
         that help organisms survive and reproduce                         Fitness

3.   Process by which modern organisms have descended
        from ancient organisms                                             Evolution

4. Person who contributed the most to our understanding
       of evolution                                                        Darwin

5. Principle that species have shared ancestors                            Common Descent

6. An inherited characteristic that increases an organism’s
       fitness.                                                            Adaptation

7.   The ship on which Darwin took his famous voyage
        around the world                                                   H.M.S. Beagle

8.   Change over time                                                      Evolution

9.  Author of On the Origin of Species by Means of Natural
       Selection.                                                          Darwin
10. A characteristic that enhances an organism’s chances
               of passing on its genes                                     Adaptation
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                Bi 12              Ch 13 Study Guide: Evolution
Observing Adaptations: Using the Main Ideas
Explain how each of the following adaptations improves the organism’s fitness.

1. Because of their shape and coloring, sargassum fish resemble certain
seaweeds.
This allows the fish to blend in with its surroundings to avoid detection by
predators

2. A flower’s fragrance attracts bees.
 This increases the flower’s chances of being pollinated and thus producing
offspring (seeds).

Concept Mapping:
Consider the concepts presented in Section 13-1 and how you would organize
them into a concept map. Now look at the concept map for Chapter 13 at the
end of this package. Notice that the concept map has been started for you.
Add the key facts and concepts you fell are important for Section 13-1. When you have finished the chapter,
you will have a completed concept map.

Section 13-2: The Age of the Earth
There is an enormous amount of evidence that suggests that evolution has occurred. Much of this evidence is
found in the rocks of the Earth itself. In this section you read about the geological evidence that shows that the
Earth has been around for a very long time and has changed over time.
The ides of James Hutton and Charles Lyell were particularly important in shaping our view of the Earth. Both
men maintained that the Earth is ancient and has been shaped by the same natural geological forces that are
still at work. Lyell also argued that scientists must always explain past events in terms of events and processes
they can observe themselves.
At the same time that Hutton and Lyell were proposing their theories, other geologists- professional and
amateur – were making some startling discoveries. They found fossils in some of the rocks they were
examining and recognized the fossils for what they were: preserved remains of ancient organisms.
The approximate age of fossils can be determined through relative dating. This technique is based on the
fact that new layers of rock are deposited on top of older layers of rock. The actual age of fossils can be
determined through        radioactive dating, which is also known as absolute dating.
Information from relative and radioactive dating has been combined to produce a geologic history of the Earth.
Through radioactive dating and examination of the rates of geological processes, scientists have determined
that the Earth is about 4.5 billion years old.
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                Bi 12              Ch 13 Study Guide: Evolution
Seeing Relationships: Building Vocabulary Skills
In the space provided, describe how the paired terms are related to each other.
1. Organism, Fossil: A fossil is the preserved remains or traces of an ancient organism.
2. Calendar, geological time scale: The geologic time scale is a record of the history of the Earth that is
preserved in the Earth’s rocks. Scientists use the geologic time scale to date events and organisms, much as
you use a calendar to understand a sequence of events in your life.
3. Layer cake, relative dating:          Relative dating is a technique used to determine the age of fossils in one
layer of rock relative to that of fossils in other layers of rock. Like the layers of rock. Like the layers of a cake,
layers of rock are laid down one on top of the other.
4. Clock, radioactive decay:             The movement of a clock’s hands (or the changing of its digital
numerals) and the decay of radioactive elements occur at a steady rate. Thus they can be used to measure time
precisely.
5. Era, period:          An era is divided into periods
6. Absolute dating, half-life:           The rate of radioactive decay, which is the basis for absolute dating, is
measured in a unit called a half-life.

Recognizing Limitations: Understanding the Main Ideas
Both relative and absolute dating are used in the study of fossils. If you were a scientist, you would have to know
which method to use in a given situation. The questions below reflect some of the problems that might be
encountered in trying to date fossils.

1.  When would the layers of rocks not be a good indicator of the age of a fossil?
        When the layers had been disturbed and were no longer in their original order, they would not be an
accurate source of information for dating purposes.

2. Could you date a fossil over one million years old using carbon-14 dating? (hint: Look up the half-life of
carbon-14.) Explain your answer.         It would be impossible to date a really old fossil using carbon-14 because
it has too short a half-life. It is almost completely gone in about a half million years.

Concept Mapping
Consider the concepts presented in Section 13-2 and how you would organize them into a concept map. Now look
at the concept map for Chapter 13 at the end of this package. Notice that the concept map has been started for
you. Add the key facts and concepts you fell are important for Section 13-2. When you have finished the chapter,
you will have a completed concept map.

Section 13-3: The Fossil Record
In this section you learned about the fossil record. You read about some of the ways in which fossils are formed.
You were also introduced to some of the ways in which scientists use fossils to learn more about the history of the
plants and animals that live on Earth today and those that have lived here in the past.
Most fossils are found in sedimentary rock. These organisms or parts of organisms are often petrified, or turned
to rock. Because conditions have to be just right, not all organisms form fossils. When scientists study the fossil
record, they have to accept that there may be many gaps because organisms have vanished from the Earth without
a trace. In addition, many fossils are incomplete or poorly preserved and thus are difficult to interpret. However,
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                Bi 12              Ch 13 Study Guide: Evolution
in spite of the chancy nature of fossil formation and preservation, paleontologists have collected millions of
fossils that present a preserved collective history of the Earth’s organisms. Perhaps the most important thing that
can be learned from the fossil record is that change after change has occurred on the Earth.

Related Ideas: Building Vocabulary Skills
In the space provided, write three complete sentences about each of the following terms that will tell something
important about that word.
1. Paleontologist:       1. A paleontologist is a scientist who studies fossils. 2. Paleontologists have collected
millions of fossils that make up the fossil record. 3. Paleontologists can offer a relatively clear picture of the
evolution of many organisms. (they also recover, restore, reconstruct, and date fossils)
2. Fossil Record:        1. The fossil record represents the preserved collective history of the Earth’s
organism’s. 2. The fossil recorded has many missing pieces. 3. The fossil record tells of major changes that
have occurred in the Earth’s climate and geography.

Concept Mapping:
Consider the concepts presented in Section 13-3 and how you would organize them into a concept map. Now look
at the concept map for Chapter 13 at the end of this package. Notice that the concept map has been started for
you. Add the key facts and concepts you fell are important for Section 13-3. When you have finished the chapter,
you will have a completed concept map.

Section 13-4: Evidence from Living Organisms
In this section you learned that all living organisms carry within their body evidence that shows the ongoing
process of evolution. The history that links living organisms with their ancestors are revealed by similarities in
early development, in body structure, and in biochemistry that are shared by related organisms. The embryos
of many different animals are so similar that it is difficult to tell them apart. This indicates that similar genes are
at work. The genes that control early development are the shared heritage from a common ancestor. Homologous
structures also provide evidence of a shared evolutionary past. Homologous structures develop from the same
basic body parts. However, they appear dissimilar because they are adapted to different functions . A human’s
arm, a bird’s wing, a horse’s foreleg, and a whale’s flippers are homologous structures. In some cases, a
vestigial structure in one animal may be homologous to a functional structure in a related animal.
Similarities in the biochemical compounds in organisms are also evidence that the organisms are descended from
a common ancestor. The more closely related two types of organisms are, the more similar their important
chemical compounds.

Defining Terms: Building Vocabulary Skills
In your own words, define each of the following terms.
1. Homology: A relationship in which structures being compared correspond in form because they are
derived from a shared primitive ancestral structure.
2. Embryo:      A organism at a very early stage of development
3. Vestigial Organ:   A useless or rudimentary organ that was more fully developed or functional earlier in
the development of the species
4. Homologous Structures:     Structures that correspond in basic form because they are derived from a
common ancestral structure
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               Bi 12             Ch 13 Study Guide: Evolution
Examining Homologies: Using the Main Ideas
The accompanying illustration shows the bones in the forelimbs of some vertebrates. These limbs are drawn to
approximately the same scale. Study the illustration, then answer the question that follow.
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               Bi 12             Ch 13 Study Guide: Evolution
1. How do the phalanges (finger bones) and metacarpals (hand bones) differ in these vertebrates.        Bat:
bones support the membranous wing. Bird: bones almost vestigial and reduced in number; make up the tip of
the wing. Horse: long fused metacarpals make up lower part of leg and phalanges are fused and reduced in
number to form a hooved foot. Human: bones form hand and fingers. Seal: tips of phalanges form claws.
Sloth: bones reduced in number; phalanges form tow large curved claws.
2. How do the carpals (wrist bones) differ in the bat, human, and horse?   Bat: carpals reduced in number and
fused to form one tiny bone. Human: a number of carpals make up wrist. Horse: carpals much changed in
shape and position on leg; form a “knee”
3. How are these forelimbs similar? They have the same kinds of bones in approximately the same position
4. How are homologous structures such as forelimbs evidence for common descent?           Because the bones are
similar in structure and arrangement, it is reasonable to assume that they are derived from a common
ancestral form.
5. How are homologous structures such as forelimbs evidence for evolution?        The differences in the
structure of the limbs indicates that they have changed over time and become better adapted to the function
they perform.

Concept Mapping:
Consider the concepts presented in Section 13-4 and how you would organize them into a concept map. Now look
at the concept map for Chapter 13 at the end of this package. Notice that the concept map has been started for
you. Add the key facts and concepts you fell are important for Section 13-4. When you have finished the chapter,
you will have a completed concept map.

				
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