Change Over Time (Packet #1)
State Standard
: H.2L.5 - Explain how multiple lines of scientific evidence support biological evolution (change)
Examples: Fossils pg. 1-4, Biochemical pg. 5-6, Embryological and
Anatomical pg. 7-10
Response Scoring Rubric
First Name Last Name
10 Exceeds
(excellent)
Evaluate the impact of the interactions of genetic variation, reproduction and inheritance, natural selection and time on biological evolution (change)
8 Meets
(proficient)
Explain how biological evolution is the consequence of the interactions of genetic variation, reproduction and inheritance, natural selection, and time, using multiple lines of scientific evidence.
6 Nearly Meets Describe the process of biological evolution through natural selection
Score
4 Does Not Meet Recognize that species have changed over time
1 Incomplete Did not participate
Part A “The Law of Superposition”. The geologic law of superposition states that 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. That process is called “Relative Dating”. Use the diagrams below, which represent neighboring sedimentary rock formations, to answer the questions that follow.
1. Which layer is the oldest in each formation? Formation 1_______ Formation 2_______
2. How would you know if these two layers are the same age?
3. Suppose fossils from layer C’ in 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?
4. Suppose you also found that layers C and B’ shared similar fossils.
Layers B and A’ look very similar, but contains no fossils. Fill in the table on the right for the relative ages of all layers of both formations?
5. Suggest one or more geological events that might explain why
Formation 2 has fewer layers then Formation 1.
Age Form. 1
New old
Form. 2
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Part B “Radioactive Dating”: Scientists use a method called radioactive dating to help determine the ages of some rocks and fossils. Radioactive Dating makes use of the decay rates of certain radioactive elements to calculate the age of the object. Scientists use the half-life of an element to make calculations involving radioactive decay. The half-life of an element is the amount of time it takes one-half the mass of a sample radioactive element to decay and form a different element. By comparing the amount of a radioactive element in a sample to the amount of decay element in the sample, scientists can calculate the age of a rock or fossil.
1. Uranium decays to form lead. The half-life of uranium is 4.5 billion years. If a rock sample has equal amounts of lead and uranium, how old is the rock?
2. Imagine that the rock described in question #1 has 10 g of uranium. In the space labeled “ b
”, identify how much uranium and how much lead the rock will contain in 4.5 billion years.
4.5 billion years 4.5 billion years
10 g U
0 g Pb b. ______ g U
______ g Pb c. ______ g U
______ g Pb
3. In the space labeled “ c ”, identify how much uranium and how much lead the rock will contain after another 4.5 billion years.
4. Look again at the rock on the far – right. Calculate how many grams of uranium and how many grams of lead the rock will contain after another half-life.
5. The “Relative Dating” of fossils assumes that similar rock layers are similar ages. Radiometric dating assumes that there is a certain percent of radioactive isotope in the rock sample when it was formed. Do you think good science (the scientific method) should involve assumptions?
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Change Over Time (Packet #1)
State Standard
: H.2L.5 - Explain how multiple lines of scientific evidence support biological evolution (change)
Examples: Fossils pg. 1-4, Biochemical pg. 5-8, Embryological and Anatomical pg. 9-12
Response Scoring Rubric
First Name Last Name
10 Exceeds
(excellent)
Evaluate the impact of the interactions of genetic variation, reproduction and inheritance, natural selection and time on biological evolution (change)
8 Meets
(proficient)
Explain how biological evolution is the consequence of the interactions of genetic variation, reproduction and inheritance, natural selection, and time, using multiple lines of scientific evidence.
6 Nearly Meets Describe the process of biological evolution through natural selection
Score
4 Does Not Meet Recognize that species have changed over time
1 Incomplete Did not participate
Determining a Fossil’s Age
Radioactive isotopes are used to date fossils and rocks. The dating is based on knowing four things: the amount of the radioactive isotope in the rock when it formed; the element into which the isotope decays; the rate of decay; and the amounts of isotope and new element in a rock or fossil. It takes 1.3 billion years for half of the radioactive isotope K 40 in a sample of decay-change into Ar 40. This time is K 40’s half-life. When a rock such as a volcanic lava forms, it is assumed that the amount of K 40 in the rock is 100 percent and the amount of Ar 40 is 0 percent.
Problem- How can you simulate radioactive half-life?
Objectives:
Formulate models - Simulate the Radioactive decay of K 40 into Ar 40 with pennies
Collect Data Collect data to determine the amount of K 40 present after several half-lives.
Make and Use a graph Graph your data and use its values to determine the age of rocks.
Materials-
Shoes Box (with lid)
100 Pennies
Graph Paper
Procedure
1.
Place 100 pennies in a shoe box
2.
Arrange the pennies so that their “head” sides are facing up. Each “head” represent an atom of
K 40, and each “tail” an atom of Ar 40.
3.
Record the number of “heads” and “tails” present at the start of the experiment. Use the row marked “0” in the data table.
4.
Cover the box. Then shake the box well. Let the shake represent one half-life of K 40, which is
1.3 billion years.
5.
Remove the lid and record the number of “heads” you see facing up. Remove all the “tail” pennies.
6.
To complete the first trial, repeat steps 5 and 6 four more times.
7.
Run two more trials and determine an average for the number of “heads’ present at each halflife.
8.
Draw a full-page graph. Plot your average values on the graph. Plot the number of half-lives for
K-40 on the x axis and the number of “heads” on the y axis. Connect the points with a line.
Remember, each half-life mark on the graph axis for K-40 represents 1.3 billion years.
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Data table
Number of
Shakes ( half lives)
0
Number of Heads (K 40 atoms left)
Trial 1 Trial 2 Trial 3 Totals Averages
1
2
3
4
5
Analyze and conclude
1.
Applying Concepts- What symbol represents an atom of K-40 in this experiment? ______
What symbol represented an atom of Ar-40? ____________
2.
Thinking Critically Compare the numbers of protons and neutrons of K-40 and Ar-40.
(Consult the Periodic Chart in the Appendix for help.) Can Ar-40 change back to K-40? Explain your answer, pointing out what procedural part of the experiment supports your answer.
3.
Defending Operationally Define the term half-life. What procedural part of the simulation represented a half-life period of time in the experiment?
4.
Communicating Explain how scientists use radioactive dating to approximate a fossil’s age.
5.
Making and using Graphs you are attempting to determine the age of a rock sample. Use your graph to read the rock’s age if it has: a.
70% of its original K-40 amount. b.
35% of its original K-40 amount. c.
10% of its original K-40 amount.
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Change Over Time (Packet #1)
State Standard
: H.2L.5 - Explain how multiple lines of scientific evidence support biological evolution (change)
Examples: Fossils pg. 1-4, Biochemical pg. 5-6, Embryological and Anatomical pg. 7-10
Response Scoring Rubric
First Name Last Name
10 Exceeds
(excellent)
Evaluate the impact of the interactions of genetic variation, reproduction and inheritance, natural selection and time on biological evolution (change)
8 Meets
(proficient)
Explain how biological evolution is the consequence of the interactions of genetic variation, reproduction and inheritance, natural selection, and time, using multiple lines of scientific evidence.
6 Nearly Meets Describe the process of biological evolution through natural selection
Score
4 Does Not Meet Recognize that species have changed over time
1 Incomplete Did not participate
Coacervates: Pre-cell Droplets
Introduction: One of the mysteries of life is how it began. No one will ever really know the mechanisms for how life was created. However, some scientist suggest that life arose in the oceans billions of years ago. They believe it evolved from non-living matter. They believe that the atmosphere consisted of mostly ammonia, water vapor, methane and hydrogen. Then, intense heat,
UV light and electrical storms mixed with these elements forming simple organic compounds like urea and amino acids. Under certain conditions, organic molecules can combine to form membrane-bound droplets called coacervates. These scientists believe that coacervates were the precursors of the first living cells on Earth. In this lab you will make and study coacervates in a series of four tests.
Materials: 5 ml 1% gelatin solution (a protein N, C, O, H), 5 ml 1% gum-arabic solution (a carbohydrate C, O, H), test tube, rubber stopper, 2 droppers, pH paper and scale, test tube rack, microscope slide, coverslip, microscope, 1% HCl, graduated cylinder, safety goggles
Part A
1. Pour 5 ml of gelatin solution into the test tube. Add 5 ml gum-arabic solution to the tube. Stopper the tube securely and gently mix by slowly inverting the tube a few times
2. Remove the stopper and place a drop of the mixture on the pH paper. Use a scale to observe the pH and record the pH in the data table.
3. Hold the mixture up to the light. Is it cloudy or clear? Record appearance in the data table
4. Use a dropper to place one or two drops of the mixture onto a microscope slide. Place a coverslip on the droplets and observe them under low power. Look for coacervates, which look like membranes with bubbles clumped inside them. If there are any coacervates present, record their number, size and movement. Draw a picture in the circle labeled test 1. Clean slide and slip.
5. Clean the dropper. Begin test 2 by adding two drops of HCl to the mixture in the test tube. Be
Careful! Wash hands immediately if you come in contact with the acid.
Plug the test tube and gently mix the liquid as you did in step 2. Then repeat steps 2-5.
6. For each of the next three tests, repeat step 5 (each time adding two new drops to the mixture).
Record your data and observations. In addition, use tests 3 and 4 to complete the drawings. If at the end of test 5 the mixture is still cloudy, continue to repeat step 5 until the mixture is clear.
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Part B
When the mixture becomes clear, make a wet-mount slide as you did in Part A, step 5. This time, however, add a drop of dilute food coloring to the liquid on the slide before positioning the coverslip.
Obsererve the coacervates under low power and record your observations.
Data Record
Test pH of mixture
1 2 3 4 5
Appearance of mixture
Observations of coacervates
Test 1 Test 2 Test 3 Test 4
1. Analyze the relationship between the appearance of the mixture and the presence of coacervates
(translation: did you see them in cloudy or clear mixtures)
2. Analyze the relationship between the pH of the mixture and the formation of coacervates
(translation: at what pH did the coacervates become visible?)
3. Do coacervates have DNA? __________ Are they alive? ___________________
4. Coacervates are a mixture of carbohydrates (C,H,O) and proteins (N, C, O, H) that form what looks like a cell membrane. However, a key ingredient is missing in the membrane. What life molecule is missing?
5. Some scientists believe that cells arose from pre-cell droplets (coacervates) formed from non-living matter like nitrogen, carbon, hydrogen and oxygen. However, is there any scientific explanation for the formation of matter itself?
6. Currently, many scientists argue the life is too complex to have arisen spontaneously and violate biogensis and the cell theory. Discuss with your lab partner if you think these coacervates could become “alive”. Could they exist without the formation of matter?
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Change Over Time (Packet #1)
State Standard
: H.2L.5 - Explain how multiple lines of scientific evidence support biological evolution (change)
Examples: Fossils pg. 1-4, Biochemical pg. 5-6, Embryological and Anatomical pg. 7-10
Response Scoring Rubric
First Name Last Name
10 Exceeds
(excellent)
Evaluate the impact of the interactions of genetic variation, reproduction and inheritance, natural selection and time on biological evolution (change)
8 Meets
(proficient)
Explain how biological evolution is the consequence of the interactions of genetic variation, reproduction and inheritance, natural selection, and time, using multiple lines of scientific evidence.
6 Nearly Meets Describe the process of biological evolution through natural selection
Score
4 Does Not Meet Recognize that species have changed over time
1 Incomplete Did not participate
How Do Species Compare?
Most classification systems focus on anatomical structures to determine taxonomic levels.
Phylogeny is a kind of family tree for organisms. Figure 1 shows a phylogenetic tree (an organizational chart) showing the relationships of major groups of animals.
Some scientists who have studied protein sequences have used it to support the idea of a common ancestor. These scientists theorize that when two species share a similar sequence of protein chains (DNA), the species may have shared a common ancestor. The closer the sequences are to each other, the more recently the two species shared an ancestor. Numerous differences in the sequences indicate the two species are not as closely related.
For example, the amino
Fig. 1 acid sequence in the protein cytochrome c of humans exactly matches the sequence in chimpanzees. The human sequence differs only by one position when compared to that of a rhesus monkey. But for animals that are clearly not closely related, the sequence shows an even greater variance.
The amino acid sequence of humans differs from that of a chicken by 18 positions and from a turtle’s by 19 positions.
In this investigation, you will look at the amino acid sequence from a variety of organisms and discuss how closely related they are.
Part A
1. You will be using Table 1 to examine amino acid sequences from the following animals: Horses,
Donkeys, Rabbits, Snakes, Turtles, and whales.
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2. Table 1 shows only a small segment of the sequence of amino acids within the cytochrome c protein. There are 104 amino acids in this protein. The amino acids function like letters in the alphabet arranged perfectly to spell a word. If the amino acid sequence changes, the word changes or in this case the protein changes to fit the needs for the organism. Table 1 shows the sequence between positions 39 and 53.
3. Use the characteristics of the animals, such as appearance, habitat, or diet, for example, to make a prediction as to which of them are most closely related. Fill out the table 2 in the Data and observations
4. Indicate which animals you think are the least closely related.
Part B
1.Compare the amino acid sequence of the horse to the rest of the animals. How many amino acids differ between the species? Record your results in Table 2.
2.Study the relationship between the species indicated in the first column of Table 2. What species share the most similar sequence with a horse?
__________________________________________________
3. Which species have sequences that are dissimilar?_______________________________________
Table 1
Position of the Amino Acids in Cytochrome c
Position of the amino acid
Horse
Whale
Turtle
Rabbit
39 40 41 42 43 44 45 46 47 48 49 50 51 52 53
A
A
A
A
B
B
B
B
C
C
C
C
D
D
D
D
E
E
E
E
F
Y
V
Y
G
G
G
G
H
H
H
H
I
Z
Z
Z
J
J
J
J
K
K
K
K
L
L
U
L
M
M
M
M
N
N
N
N
O
O
O
O
A B C D E F G H Z J K L M N O Donkey
Snake
Position of the amino acid
A
39
B
40
C
41
D
42
E
43
V
44
G
45
H
46
Z
47
J
48
K
49
W M
50 51
N
52
O
53
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Data and Observations
1. Fill out table 2
Animal Appearance
(describe feet)
Table 2
Habitat
(biome)
Diet Number of Amino
Acid positions different from horse
Skin covering
Horse
Whale
Turtle
Rabbit
Donkey
Snake
2. In the space below, construct cladogram (a branching tree) using the information you’ve gathered.
Your cladogram should include the animals in the study and how closely related they are to the horse. horse
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Analyze and Conclude
1. Which species are closest to a horse as indicated by the particular sequences of amino acids?
2. Which species are more distantly related to a horse as indicated by the sequence of amino acids in
Table 1?
3. Based on the evidence in table 2, how would you describe species with similar amino acid sequences in terms of their shape and structure?
4. Based on table 2, make a general statement about whether any of the species other than horses are more or less similar to each other.
5. Currently, scientists are moving away from the traditional method of grouping organisms based on comparative anatomy. What methods are they using today to classify organisms (Hint: what evidence did you use biotechnology to attain?).
6. Cytochrome c is just one strand of amino acids. Your body is programmed with thousands (about
60,000) of these genes. What life molecule is the “program for life”? ____________ What is it’s code? ______-________ and ______-________
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