Download Station 1 - Fall River Public Schools

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Evidence of Evolution: Comparative Anatomy Lab
INTRODUCTION: Evidence has been found to indicate that living things
have changed gradually during their natural history. The study of
fossils as well as embryology, biochemistry, and comparative
anatomy provides evidence for evolution.
OBJECTIVE: In this lab activity you will learn about homologous, analogous, vestigial structures,
fossils, embryology and biochemistry and their significance in evolution theory.
Station 1: Homologous Structures
There are many examples of body structures that are formed in similar ways during
embryonic development and that share similar patterns of bone structure, even though they
take on different forms and perform somewhat different functions. These structures are
called homologous structures. Homo- means same, and -logous means information, so
homologous means “same information”. Homologous structures mean that the animals share
a relatively recent common ancestor.
1. Carefully examine the drawings of forelimb skeletons shown in Figure 1 on the next
page. Look for similarities in the bones amongst the various animals.
2. Color in the human arm first. Color the bones of the arm (the humerus, ulna, and
radius) blue. Color the bones of the hand (the carpal, metacarpals, and phalanges)
yellow.
3. Color the corresponding bones in each of the other animals the same color as the
human bones.
4. Observe each of the skeletons again, and describe the function of each limb in the
table below:
Animal
Function
human
whale
cat
bat
bird
crocodile
5. Answer the Summary Questions.
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Figure 1.
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HOMOLOGOUS STRUCTURES
1. Are the functions of the limbs of each of the animals illustrated the same or different?
2. Are the bones of the limbs arranged in a similar or in a very different way in each animal?
3. Does the similarity in bone structure suggest a common ancestry amongst these animals?
4. Offer a possible evolutionary explanation for how the skeletons can be similar but
the functions very different in each of the animals.
5.
Are the bones arranged in a similar way in each animal?
These structures are formed in similar ways during embryonic development and share like
arrangements: however, they have somewhat different forms and functions. They are called
homologous structures.
Station 2: ANALOGOUS STRUCTURES
There are also many examples of body structures in animals that are very similar in function
and superficially similar in form and but develop very different and have very different
internal structures and embryonic development. These structures are called analogous
structures. Analogous structures mean that the animals do not share a recent common
ancestor.
6. Examine the butterfly wing and the bird wing shown below.
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7. Look for any similar bone structure.
8.
What function do the butterfly and bird wings share?
9.
In what way do these structures differ?
10. Can you think of a possible reason why two unrelated species have the same way of getting
from place to place?
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11. Do birds and insects share any structural similarities that would suggest they are closely
related?
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Some apparently unrelated animals have organs with similar function, yet are very different in
structure and form. These structures are called analogous structures.
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Station 3: Vestigial Structures
There are also many examples of body structures in animals that show gradual changes over
time. In some cases, these changes have reduced or removed the function of some body parts
and organs. These reduced or lost structures are called vestigial structures. The wings of
penguins and the leg bones of snakes are examples of this phenomenon.
12. Observe the drawings of the cavefish and the minnow shown in Figure 3. The fish are
related to each other but the cave fish is blind and only has the remnants of an eye.
13. Explain why eyesight is not an important adaptation to life in a deep sea cave.
14. Does the appearance of the cavefish and the minnow suggest a common ancestry? Why?
15. Read the list of human vestigial structures shown below. Suggest a possible function for
each structure and explain why it became vestigial:
16. List another structure (not listed in this lab) that you think is vestigial and explain why.
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VESTIGIAL STRUCTURES
Structure
Probable Function
Possible raw meat digestion?
appendix
Why Vestigial?
Discovery of fire? We started
cooking meat…
coccyx (tail bone)
muscle that
move ears
muscles that
make hair stand
up
little toe
wisdom teeth
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Station 4: Embryology
Evolution occurs slowly. In most cases, it is not possible to observe evolution in progress. However,
evidence of evolution can be found by observing the early stages of development in
vertebrates. All vertebrate embryos start out similar in appearance. This similarity has led
scientists to think that these organisms have a common ancestor. The diagrams below
illustrate stages in the embryonic development of a fish, a pig, and a human.
17. How does a comparison of the embryos provide evidence of evolution?
18. Which of the organisms would be most biochemically similar to humans: fish or pig?
19. Looking at the diagram below, identify the structures that each of the embryos have in common.
You should do this by making a list.
20. Use evidence from your lists to explain which organism is the closest relative to man?
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21. Why do you think humans have gill-slits and tails when they are embryos?
Station 5: Fossil Record
According to the geological law of superposition, older layers of sedimentary rock lay
beneath younger layers. Scientists use this law to determine the order in which organisms
appeared and disappeared in the fossil record. The law cannot be used to determine the
absolute ages of rock layers. It can be used to determine the relative ages of rock layers by
comparing their fossil records.
22. Which layer is the oldest in each formation?
a. Are the two layers the same age?
b. How could you tell?
23. Suppose fossils from layer C’ of Formation 2 are the same as fossils from layer D in Formation 1.
What could you say about the age of fossils from Layer E?
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24. Suppose you also found that layers C and B’ shared similar fossils. Layers B and A’ look very
similar, but contain no fossils. What could you say about the relative ages of all layers of both
formations?
25. Suggest one or more geological events that might explain why Formation 2 has fewer
layers than Formation 1 and describe the scenarios you chose.
This is a series of skulls and front leg fossils of organisms believed to be ancestors of the modern-day
horse.
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26. Give two similarities between each of the skulls that might lead to the conclusion that these
are all related species.
27. What is the biggest change in skull anatomy that occurred from the dawn horse to the modern
horse?
28. What is the biggest change in leg anatomy that occurred from the dawn horse to the modern
horse?
Station 6 – Molecular Evidence
Cytochrome c is a protein found in mitochondria. It is used in the study of evolutionary relationships
because most animals have this protein. Cytochrome c is made of 104 amino acids joined
together. Amino acid sequences of certain proteins can be used to determine how closely related
different species are. If the amino acid sequences for a certain protein are very similar in two
species, one can assume that those two species had a common ancestor. All 104 amino acids in
the protein cytochrome c are identical in humans and chimpanzees.
Below is a list of the amino acids in part of a cytochrome protein molecule for 9 different animals. Any
sequences exactly the same for all animals have been skipped.
For each non-human animal, take a highlighter and mark any amino acids that are different than the
human sequence. When you finish, record how many differences you found in the table on the next
page.
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42
43
44
46
47
49
50
53
54
55
56
57
Human
Q
A
P
Y
S
T
A
K
N
K
G
I
Chicken
Q
A
E
F
S
T
D
K
N
K
G
I
Horse
Q
A
P
F
S
T
D
K
N
K
G
I
Tuna
Q
A
E
F
S
T
D
K
S
K
G
I
Frog
Q
A
A
F
S
T
D
K
N
K
G
I
Shark
Q
A
Q
F
S
T
D
K
S
K
G
I
Turtle
Q
A
E
F
S
T
E
K
N
K
G
I
Monkey
Q
A
P
Y
S
T
A
K
N
K
G
I
Rabbit
Q
A
V
F
S
T
D
K
N
K
G
I
58
60
61
62
63
64
65
66
100
101
102
103
104
Human
I
G
E
D
T
L
M
E
K
A
T
N
E
Chicken
T
G
E
D
T
L
M
E
D
A
T
S
K
Horse
T
K
E
E
T
L
M
E
K
A
T
N
E
Tuna
V
N
N
E
T
L
R
E
K
A
T
S
-
Frog
T
G
E
E
T
L
M
E
S
A
C
S
K
Shark
T
Q
Q
E
T
L
R
I
K
T
A
A
S
Turtle
T
G
E
E
T
L
M
E
D
A
T
S
K
Monkey
T
G
E
D
T
L
M
E
K
A
T
N
E
Rabbit
T
G
E
D
T
L
M
E
K
A
T
N
E
Animal
Number of Amino Acid Differences
Compared to Human Cytochrome C
Animal
Horse
Shark
Chicken
Turtle
Tuna
Monkey
Frog
Rabbit
Number of Amino Acid Differences
Compared to Human Cytochrome C
29. Based on the Cytochrome C data, which organism is most closely related to humans? Explain your
answer.
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30. Do any of the organisms have the same number of differences from human Cytochrome C? In
situations like this, how would you decide which is more closely related to humans?
Final Review…How did you do?
Evidence
Homologous
Structures
31. A modified
Analogous
Structures
Vestigial Embryological
Structures Development
Genetic
Comparisons
structure
seen among different
groups of descendants
32. .In the earliest
stages of
development, a
tail and gill slits
can be seen in
fish, birds,
rabbits, and
mammals.
33. Examples of
forelimbs of bats,
penguins, lizards,
and monkeys
34. The forelimbs of
flightless birds
35. DNA and RNA
comparisons may lead
to evolutionary trees
36. Bird and butterfly
wings have same
function but
different structures.
37. A body structure
reduced in
function but may
have been used in
an ancestor
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