Station 1 – Fossil Record The very first horses evolved on the North American continent over 55 million years ago. The horse fossil record is very rich in transitional species. This is a series of skulls and front leg fossils of organisms believed to be ancestors of the modern-day horse. 1. Observe the following skulls and legs of several horses.
Equus (modern horse)
Pilohippus
Merychippus
Mesohippus
Eohippus (Dawn horse)
Source: http://www.iq.poquoson.org
2. Answer these questions in your science notebook. a. Give two similarities between each of the skulls that might lead to the conclusion that these are all related species. b.What is the biggest change in skull anatomy that occurred from the dawn horse to the modern horse? c. What is the biggest change in leg anatomy that occurred from the dawn horse to the modern horse?
Station 2- Comparative Embryology Darwin noted the striking similarity among embryos of complex animals such as humans, chickens, frogs, reptiles, and fish. He wrote that these similarities are evidence for evolution. He pointed out that human embryos pass through a number of embryonic stages inherited from their ancestors because they have inherited the developmental mechanisms from a common ancestor. For example, fish, bird, rabbit, and human embryos are similar in appearance in the early stages. Later on, as the embryos grow and develop, they become less and less similar.
Source: http://www.starlarvae.org
1. Hypothesize which embryo is from each of the following organisms: human, chicken, rabbit, tortoise, salamander, or fish. 2. Fill in data in table 1 by writing the embryo letter next to the organisms.
FLIP THE PAGE
Glue or tape this page to the back of the first page of Station 3
These are older, more developed embryos from the same organisms.
1. Hypothesize which embryo is from each of the following organisms: human, chicken, rabbit, tortoise, salamander, or fish. 2. Fill in data in table 2 by writing the embryo letter next to the organisms
FLIP THE PAGE
Glue or tape this page to the back of the first page of Station 3
These are embryos at their most advanced stage, shortly before birth.
1. Describe how the embryos changed for each of these organisms from their earliest to latest stages. 2. Fill in the data in table 3 by describing the anatomical changes from early to late stages. 3. Fill in table 4 by describing the physical similarities that exist between each embryo to the others. 4. Explain how the similarities between these embryos are used as evidence of a common ancestry.
Station 3 – Comparative Anatomy Shown below are images of the skeletal structure of the front limbs of 6 animals. These homologous structures are formed in similar ways during embryonic development and share like arrangements; however they have somewhat different forms and functions. See labels and shaded areas.
1. Fill in data in Table 5 by indicating what type of movement, or function, each limb is responsible for in each animal. 2. Fill in data in Table 6 by comparing the skeletal structure of each limb to the human arm. Relate the differences you see in form to the differences in function.
Station 4 – Comparative Anatomy Some apparently unrelated animals have organs with similar functions, yet are very different in structure and form. These structures are called analogous structures. For example, the eye of a human is very similar in structure to the eye of the octopus. In fact, the octopus eye is superior to the human eye in that it does not have a "blind spot". Structurally, that is really the only difference between the eyes. However, the octopus and the human are not closely related and reside far away from each other on the tree of life 1. Compare the anatomy of the butterfly and bird wing below. 2. Answer these questions in your science notebook. a. What is the function of each of these structures? b.How are they different in form? Give specific differences.
Human Eye
Octopus Eye
Station 5 – Comparative Anatomy A structure that has little or no function in an organism, but is clearly related to a more fully developed structure in another organism, is known as a vestigial structure. These structures support the idea that species have evolved over time as a result of natural selection. For example, although snakes have no legs, there are tiny leg bones in the skeletons of some snake species. These vestigial structures show that snakes evolved from animals that had legs. 1. Compare the overall body structure of the cave fish and the minnow below. 2. Answer the following questions in your science notebook. a. What is the biggest, most obvious difference between the body structures of these two fish? b.Assume the two fish came from the same original ancestor. Why might the cave fish have evolved without eyesight? c. What kind of sensory adaptation would you hypothesize the cave fish has to allow it to navigate in a cave, including catching and eating food? d.How are vestigial structures an example of evidence of evolution? 3. Complete Table 7 in your lab.
Station 6 – Biogeography Biogeography is the study of the past and present geographical distribution of organisms. Biogeographic distributions demonstrate the fact that species that have evolved under similar conditions in different parts of the world look similar. For example, the animals in the pictures live on different continents. Since they were exposed to similar ecological conditions, they were exposed to similar pressures of natural selection. Therefore, they end up evolving certain striking features in common.
1. Carefully observe and compare the anatomy of the four organisms in the picture. 2. Answer these questions in your science notebook a. What ecological conditions caused the similarities in the body plan of these animals? b. How can two species that look very different from each other be more closely related than two other species that look similar to each other? (i.e. a dolphin and a rat are more closely related than a dolphin and a shark)
Station 7 – Observable Changes Some biologists say that evolution has happened when a trait that is caused by genetics becomes more or less common in a group of organisms. Evolution is generally a very, very, very slow process, but they are exceptions. One example occurred in populations of peppered moths in the area of Manchester, England from 1845 to 1890. Before the industrial revolution, the trunks of the trees in the forest around Manchester were light grayish-green due to the presence of lichens. Most of the peppered moths in the area were light colored with dark spots. As the industrial revolution progressed, the tree trunks became covered with soot and turned dark. Over a period of 45 years, the dark variety of the peppered moth became more common.
1. Answer these questions in your science notebook. a. What could have originally caused the existence of two forms of the same species of moth? b.Why is variation among individuals so important to the process of natural selection? What are the main sources of this variation? c. What do you think cause the rapid change in the populations of peppered moths from a light to a dark coloration? d. The British have instituted pollution controls on factories. What would happen to the moth populations if the pollution created by the Industrial Revolution were to be reversed?
Station 8 – Molecular Biology Although the biochemistry of organisms was not well known in Darwin's time, modern biochemistry indicates there is a biochemical similarity in all living things. 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. Below is a list of the amino acids in part of a cytochrome protein molecule for 9 different animals. 1. Count how many amino acids are different from the human sequence for each organism. 2. Record how many differences you found in Table 8. 42
43
44 46
47
49
50
53
54
55
56
57
58
60
61
62
63
64
65
66
100
101
102
103
104
Human
Q
A
P
Y
S
T
A
K
N
K
G
I
I
G
E
D
T
L
M
E
K
A
T
N
E
Chicken
Q
A
E
F
S
T
D
K
N
K
G
I
T
K
E
E
T
L
M
E
K
A
T
N
E
Horse
Q
A
P
F
T
T
D
K
N
K
G
I
T
G
E
D
T
L
M
E
D
A
T
S
K
Tuna
Q
A
E
Y
S
T
D
K
S
K
G
I
V
N
N
D
T
L
M
E
S
A
T
S
-
Frog
Q
A
A
F
S
T
D
K
N
K
G
I
T
G
E
D
T
L
M
E
S
A
C
S
K
Shark
Q
A
Q
F
S
T
D
K
S
K
G
I
T
Q
Q
E
T
L
R
I
K
T
A
A
S
Turtle
Q
A
E
F
S
T
E
K
N
K
G
I
T
G
E
E
T
L
M
E
D
A
T
S
K
Monkey
Q
A
P
Y
S
T
A
K
N
K
G
I
T
G
E
D
T
L
M
E
K
A
T
N
E
Rabbit
Q
A
V
F
S
T
D
K
N
K
G
I
T
G
E
D
T
L
M
E
K
A
T
N
E
