Evolution Revised THIRD EDITION REDESIGNED FOR THE NGSS ISSUES AND LIFE SCIENCE
Evolution Revised THE LAWRENCE HALL OF SCIENCE UNIVERSITY OF CALIFORNIA, BERKELEY THIRD EDITION REDESIGNED FOR THE NGSS ISSUES AND LIFE SCIENCE
This book is part of SEPUP’s Issues and Science 17-unit multi-year course. The units are designed to allow for custom sequencing to meet local needs. For more information about these units, see the SEPUP and Lab-Aids websites listed at the bottom of this page. • Land, Water, and Human Interactions • Geological Processes • Earth’s Resources • Weather and Climate • Solar System and Beyond • Ecology • Body Systems • From Cells to Organisms • Reproduction Additional SEPUP instructional materials include: • SEPUP Modules: Grades 6–12 • Science and Sustainability: Course for Grades 9–12 • Science and Global Issues: Biology: Course for High School Biology This material is based upon work supported by the National Science Foundation under Grants 9554163 and 0099265. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. For photo and illustration credits, see page 134, which constitutes an extension of this copyright page. The preferred citation format for this book is SEPUP. (2020). Issues and Life Science: Evolution. Lawrence Hall of Science, University of California at Berkeley. Lab-Aids, Inc. Evolution - Student Book, Revised Third Edition | Redesigned for the NGSS © 2020 The Regents of the University of California ISBN: 978-1-63093-624-2 v1 SMS-EVO-3RSB Print Number: 01 Print Year: 2020 Developed by Lawrence Hall of Science University of California at Berkeley Berkeley, CA 94720-5200 website: www.sepuplhs.org Published by 17 Colt Court Ronkonkoma, NY 11779 Website: www.lab-aids.com • Evolution • Biomedical Engineering • Energy • Chemistry of Materials • Chemical Reactions • Force and Motion • Fields and Interactions • Waves
v ISSUES & LIFE SCIENCE THIRD EDITION Director: Ben W. Koo Director Emerita: Barbara Nagle Coordinator: Janet Bellantoni AUTHORS Wendy Jackson, Tiffani Quan, Barbara Nagle, Manisha Hariani OTHER CONTRIBUTORS Asher Davison, Daniel Seaver SCIENTIFIC REVIEW Dr. John Bates, Associate Curator, and Brian Tsuru, Research Assistant, Field Museum, Chicago, IL PRODUCTION Coordination, Design, Photo Research, Composition: Seventeenth Street Studios Production Coordinator for Lab-Aids: Hethyr Tregerman Editing: Kerry Ouellet and Jennifer Davis-Kay
vi FIELD TEST CENTERS The classroom is SEPUP’s laboratory for development. We are extremely appreciative of the following center directors and teachers who taught the program during the 2003–04 and 2004–05 school years. These teachers and their students contributed significantly to improving the first edition of the course. Since then, Issues and Life Science has been used in thousands of classrooms across the United States. This third edition is based on what we have learned from teachers and students in those classrooms and in the Revision Centers listed on the next page. It also includes new data and information, so the issues included in the course remain fresh and up-to-date. REGIONAL CENTER, SOUTHERN CALIFORNIA Donna Markey, Center Director Kim Blumeyer, Helen Copeland, Pat McLoughlin, Donna Markey, Philip Poniktera, Samantha Swann, Miles Vandegrift REGIONAL CENTER, IOWA Dr. Robert Yager and Jeanne Bancroft, Center Directors Rebecca Andresen, Lore Baur, Dan Dvorak, Dan Hill, Mark Kluber, Amy Lauer, Lisa Martin, Stephanie Phillips REGIONAL CENTER, WESTERN NEW YORK Dr. Robert Horvat, Center Director Kathaleen Burke, Dick Duquin, Eleanor Falsone, Lillian Gondree, Jason Mayle, James Morgan, Valerie Tundo JEFFERSON COUNTY, KENTUCKY Pamela Boykin, Center Director Charlotte Brown, Tara Endris, Sharon Kremer, Karen Niemann, Susan Stinebruner, Joan Thieman LIVERMORE, CALIFORNIA Scott Vernoy, Center Director Rick Boster, Ann Ewing, Kathy Gabel, Sharon Schmidt, Denia Segrest, Bruce Wolfe QUEENS, NEW YORK Pam Wasserman, Center Director Gina Clemente, Cheryl Dodes, Karen Horowitz, Tricia Hutter, Jean Rogers, Mark Schmucker, Christine Wilk TUCSON, ARIZONA Jonathan Becker, Center Director Peggy Herron, Debbie Hobbs, Carol Newhouse, Nancy Webster INDEPENDENT Berkeley, California: Robyn McArdle Fresno, California: Al Brofman Orinda, California: Sue Boudreau, Janine Orr, Karen Snelson Tucson, Arizona: Patricia Cadigan, Kevin Finegan
vii REVISION CENTERS Chicago, Illinois: Bejaza Duskic, Francis Panion, Robert Troher Elmhurst, Illinois: Kelly Biala
viii A Letter to Issues and Science Students As you look through this book, you may wonder, “Why does this book look different from other science textbooks I’ve seen?” The reason is simple: It is a complete science program, and only some of what you will learn can be seen by leafing through these pages! SEPUP is an active learning program. Through hands-on laboratories, investigations, readings, simulations, scientific debates, role plays, and design projects, you will develop your thinking about science and engineering and how they relate to many important issues facing our society today. In this program, you will think scientifically about natural phenomena or observable events. For example, you might investigate why most people look unique but also look more like their biological relatives than they look like most other people. Or perhaps you will model how a change in a river’s path due to natural processes, which can then change the landscape and impact human-made structures. The activities in this course provide many opportunities for you to figure out why or how something happens. Like a scientist, you’ll begin by asking questions and analyzing evidence to help you create explanations and models. Like an engineer, you will solve specific problems by designing a solution—for example, designing a model of an artificial heart valve for a person with advanced heart disease. This program will ask you to think about issues at the intersection of science and society. You may consider how to create a mechanical system to help drivers maintain a safe distance behind other cars, or debate the trade-offs of using different materials (aluminum, glass, or plastic) to make a water bottle. You’ll improve your decision-making skills by using evidence and analysis to make the best decision about what should be done for a community, such as deciding where to mine for valuable resources like copper while minimizing environmental impact. You’ll consider the influence of science, engineering, and technology on societal issues, and what role scientists, engineers, and citizens play in the decision-making process. How do we know that this is a good way for you to learn? Because most research on science education supports it. Many activities in this book were tested by hundreds of students and their teachers. Their feedback, and what we’ve learned about how people develop an understanding of science, has informed the SEPUP approach. We believe the SEPUP program will show you that learning about science and engineering is important, enjoyable, and relevant to your life. SEPUP Staff
ix 1 i n v e s t i g at i o n The Full Course 3 2 m o d e l i n g Hiding in the Background 7 3 r o l e p l ay A Meeting of Minds 11 4 m o d e l i n g Battling Beaks 19 5 m o d e l i n g Mutations: Good or Bad? 25 6 c o m p u t e r s i m u l at i o n Mutations and Evolution 31 7 v i e w a n d r e f l e c t Origins of Species 35 8 r e a d i n g History and Diversity of Life 39 9 l a b o r at o r y Fossil Evidence 47 10 i n v e s t i g at i o n Fossilized Footprints 53 11 i n v e s t i g at i o n Family Histories 57 12 i n v e s t i g at i o n A Whale of a Tale 63 13 i n v e s t i g at i o n Embryology 67 14 ta l k i n g i t o v e r The Sixth Extinction? 71 15 r e a d i n g Bacteria and Bugs: Evolution of Resistance 77 16 i n v e s t i g at i o n Manipulating Genes 81 17 p r o j e c t Evolution and Us 85 Unit Summary 87 Appendices 91 Glossary 125 Index 129 Credits 134 Contents Evolution Revised
Evolution
Sasha and her family decided to take a trip to the zoo to see the new bird exhibit. Her father had read online that the new exhibit had many more kinds of birds than it used to have, and Sasha was excited to see them. At the exhibit, Sasha noticed a large pink bird on the opposite side of the pond. “Let’s take this path so we can get a better look at that beautiful bird!” exclaimed Sasha. As they got closer, Sasha’s father noticed that the bill on the bird had an unusual shape. “What an interesting bill,” he said. “I’ve never seen anything like that before.” Sasha began reading the signs along the path with pictures and names of all the birds in the exhibit, and she identified the pink bird as a spoonbill. “I wonder why its bill is shaped like that?” she said. “Let’s stay and watch it for a while,” her father suggested. “Maybe we can figure it out.” • • • In this unit, you will: • Explore phenomena related to how populations of organisms change over both short and long periods of time—for example, changes in the shape and structure of birds’ beaks and bills • Look for patterns in data to develop cause-and-effect explanations for these phenomena • Use models to explore how populations of organisms change over time and how new species arise while others go extinct • Interpret many sources of evidence for the evolution of life on Earth now and in the past • Investigate the issue of how people are affected by and affect evolution
EVOLUTION 3 1 The Full Course i n v e s t i g at i o n Sasha has a serious respiratory infection. Her doctor has done tests, which show that the infection is caused by bacteria. Dr. Torres prescribes antibiotics to help fight the infection. “Sasha, I think you will start to feel better in a few days, but it’s important that you keep taking all the medicine even after you feel better. You must finish it all. Don’t stop, and don’t miss doses,” warns Dr. Torres. “Why?” Sasha asks. “I don’t keep taking other medicines after I feel better. Like, once my headache is gone, I don’t take any more headache medicine.” “There’s a real crisis developing with antibiotics,” Dr. Torres explains. “People take them when they don’t need them, or they take them for a while and then stop. This causes bacteria to evolve antibiotic resistance. Doctors and researchers are very worried about this.” “What happens when the bacteria are resistant?” asks Sasha’s mother. “The antibiotics no longer work against the resistant bacteria. Last year, our clinic had four patients with infections that we used to be able to fight easily! Three of those patients had to stay in the hospital and take antibiotics for a very long time before they got better.” Dr. Torres sighs. “The other patient didn’t make it.” “You know, I just saw a story about that on TV,” says Sasha’s mother. “I’m beginning to understand that antibiotics are different from other medicines. I’ll be sure to take all the pills!” says Sasha.1 1 NGLS4C1 Streptococcus bacteria in its natural environment, the human throat
ACTIVITY 1 THE FULL COURSE 4 EVOLUTION Antibiotics are chemical substances that help your body fight off an infection by killing harmful bacteria. A small number of bacteria in any population may not be affected by the antibiotic as quickly as the rest of the population. These bacteria, which are more resistant to the treatment, continue to grow and reproduce if doses of the antibiotic are missed. In this activity, you will use a model to explore how bacteria have changed over time to become resistant to many antibiotics. GUIDING QUESTION What happens when a person does not take antibiotics as prescribed? MATERIALS For each pair of students 1 set of 50 disks: 20 green, 15 blue, 15 orange 4 colored pencils (including green, blue, and orange) 1 number cube For each student 1 Student Sheet 1.1, “Bacteria Graphs” A Bacterial Infection Imagine that you are sick with a bacterial infection. Your doctor prescribes an antibiotic to be taken every day for eight days. Colored disks represent the harmful bacteria that are in your body: Disease-Causing Bacteria Represented by Least-resistant bacteria green disks Resistant bacteria blue disks Extremely resistant bacteria orange disks Each time you toss the number cube, it is time to take the antibiotic. The number on the number cube tells you what to do.
THE FULL COURSE ACTIVITY 1 EVOLUTION 5 PROCEDURE 1. You and your partner should begin with 20 disks: 13 green, 6 blue, and 1 orange. These disks represent the harmful bacteria living in your body before you begin to take the antibiotic. Set the extra disks aside for now.23 2. Make a data table in your science notebook similar to the following one. 4 Number of Harmful Bacteria in Your Body Toss number Least-resistant bacteria (green) Resistant bacteria (blue) Extremely resistant bacteria (orange) Total Initial 13 6 1 20 1 2 3 4 5 6 7 8 3. It is time to take your antibiotic. Toss a number cube, and follow the instructions in the following Number Cube Key. Number Cube Key YOUR TOSS WHAT HAPPENED WHAT TO DO 1, 3, 5, 6 You took the antibiotic on time, so bacteria are being killed! Remove 5 disks: Start by removing the green disks, then the blue, and then the orange. 2, 4 You forgot to take the antibiotic. Do nothing. 4. The bacteria are reproducing all the time! If one or more bacteria of a particular type are still alive in your body, add 1 disk of that color to your population. For example, if you have resistant (blue) and extremely resistant (orange) bacteria in your body, add 1 blue disk and 1 orange disk to your bacterial population. 5. Record the number of each type of bacteria in your body in the table in your science notebook. 2 NGSPDM1 3 ELRS683 4 SELTSN1
ACTIVITY 1 THE FULL COURSE 6 EVOLUTION 6. Repeat Steps 3–5 until you have completed your table. 7. Use the data in your table to graph the population for each type of bacteria and the total number of bacteria on Student Sheet 1.1, “Bacteria Graph.” Use different-colored pencils to represent each type of bacteria.5 ANALYSIS 1. Describe what happened when you or a classmate did the following: a. Remembered to take the antibiotic according to the instructions b. Missed several doses of the antibiotic6789 2. Provide an explanation for these results. 10 Hint: How do bacteria differ, and what is happening to the bacteria when they are exposed to antibiotics in their environment? 3. Explain how people are affecting populations of bacteria when they take an antibiotic. 4. Revisit the issue: What questions do you have about other ways that humans affect or are affected by other changing populations? 5. Reflection: Have you or any of your family members ever taken an antibiotic? If so, did you follow the instructions? How did this activity affect how you will take antibiotics in the future? 5 SEASOD1 6 MARP6A1 7 MASP6B5 8 NGSPAD1 9 NGCCPA1 10 NGCCCE2
EVOLUTION 7 2 Hiding in the Background m o d e l i n g I n the activity “The Full Course,” you explored how the presence of antibiotics in the environment affects the survival of bacteria, depending on their resistance to antibiotics. In this activity, you will use a model to explore how an environment that includes predators affects the survival of individuals of an imaginary species: toothpick worms. You will focus on differences in just one feature: the color of the worms. The versions of a feature, such as color, are called traits. Differences in traits are called variations. The two possible color traits in worms are green and beige.111213 GUIDING QUESTION How does the environment affect an individual’s probability of survival and successful reproduction? 11 NGLS4B1 12 NGLS4C1 13 NGLS2A2 Several examples of the camouflage phenomenon
ACTIVITY 2 HIDING IN THE BACKGROUND 8 EVOLUTION MATERIALS For each group of four students 2 paper bags 50 green toothpicks 50 beige toothpicks For each student 1 clear plastic bag 1 Student Sheet 2.1, ”Worm Population” 1 piece of graph paper PROCEDURE 1. Label one of the paper bags “Worms” and the other “Reserve Toothpicks.”1415 2. Each toothpick represents a worm. Count 25 green “worms” and 25 beige “worms,” and place them into the paper bag labeled “Worms.” This is the initial number of worms in the initial population, also called the first generation. These amounts are already marked for you in both tables on Student Sheet 2.1, “Worm Populations.” 3. Place the rest of the toothpicks into the bag labeled “Reserve Toothpicks.” 4. Shake the “Worms” bag to mix the worms. 5. As directed by your teacher, scatter the worms on the “ground.” 6. You are going to play the role of a bird predator that preys on worms. Your group must “eat” (pick up) 40 worms, so decide how many worms each member of your group will eat. You must pick up the first worms that you see, regardless of the color, and place them in the clear plastic bag, which represents the bird’s stomach. 14 NGSPDM1 15 ELRS683 The Toothpick Worm Model Imagine that you are a bird that eats small worms. In this activity, toothpicks will represent the worms that you eat. There are two traits for worm color: beige and green. The toothpick colors represent these two traits.
HIDING IN THE BACKGROUND ACTIVITY 2 EVOLUTION 9 7. Count the total numbers of green and beige worms that survived in the habitat. Record these totals in Row 2 of the table for Generation 1 on Student Sheet 2.1. 8. Each surviving adult worm is reproducing, and each of them has 4 offspring that are identical to the parent. On Student Sheet 2.1, multiply the numbers of green and beige surviving adult worms by 4. For example, if you had 7 green worms still alive, there would be a total of 28 green offspring worms (7 x 4 = 28). Record this number in Row 3. 9. Add Rows 2 and 3 to get the total number of surviving adults and offspring for green worms and beige worms. Record this number in Row 4. This number represents the number of green worms and beige worms that are present in the habitat at the start of the second generation. Copy these numbers into Row 1 of the table for Generation 2. 10. Count the number of green and beige toothpicks shown in Row 1 for Generation 2 and place them in your “Worms” bag. 11. Repeat Steps 4–10 but this time complete the table for Generation 2. 12. Repeat the steps again for Generation 3, the final generation in this simulation. 13. Create a graph showing the results from the start of Generation 1 through the end of Generation 3. 1617 ANALYSIS 1. Look at your worm population results.1819202122 a. Use a ratio to compare the number of green worms to the number of beige worms. For example, the ratio of green to beige worms in Generation 1 is 25:25, or 1:1. b. Calculate the percentage of green worms and beige worms in each generation. c. Describe how the percentage of green and beige worms changed over the three generations. d. Did any individual worm change color? Explain. e. Why do you think you observed this pattern? Provide a causeand-effect explanation for this pattern. Hint: A pattern is something that happens in a repeated and predictable way. 16 NGSPAD1 17 SEASOD1 18 NGCCPA1 19 NGSPUM1 20 SEASAD1 21 MARP6A1 22 MASP6B5
ACTIVITY 2 HIDING IN THE BACKGROUND 10 EVOLUTION 2. Imagine that you performed this simulation for another generation. What do you predict the percentage would be of green and beige worms among the worm population in their habitat? Explain your prediction.23 3. Due to a drought, grass begins to dry out and die, leaving only dead grass stalks. What is likely to happen to the percentage of green and beige worms? Explain.242526 4. Compare and contrast your findings with those from the activity “The Full Course.” How are they similar? How are they different? 5. Revisit the issue: How might people be changing the environment and therefore affecting evolution? 23 NGSPDM1 24 NGLS2A2 25 NGSPCE2 26 NGCCCE2
EVOLUTION 11 3 A Meeting of Minds r o l e p l ay I n the previous activities, you used models to explore how factors in the environment can influence the survival of organisms. In the first model, you explored how chemical substances in the environment affect bacteria. In the second model, you explored how predation affects toothpick worms. In your models, you explored what happens over a few generations. But what happens when these environmental factors continue to affect a population of organisms for many more generations? In this activity, you will compare two different explanations for how species change over time.2728 GUIDING QUESTION How does natural selection happen? 27 NGLS4B1 28 NGLS4C1 Charles Darwin (left) and Jean-Baptiste Lamarck (right)
ACTIVITY 3 A MEETING OF MINDS 12 EVOLUTION MATERIALS For each student 1 Student Sheet 3.1, “A Meeting of Minds” PROCEDURE 1. Assign a role for each person in your group. Assuming that there are four people in your group, each of you will read one role: • Charles Darwin, 19th-century scientist • Isabel Matos, science reporter for Station W-EVO • Jean-Baptiste Lamarck, 19th-century scientist • Wendy Chin, middle school student 2. Read aloud the role play on the next pages aloud. As you read, think about what each character is saying. 3. Mark whether you think scientists today would agree or disagree with the statements on Student Sheet 3.1, “A Meeting of Minds.”29 4. Discuss the statements with your group. HOW DO SPECIES CHANGE OVER TIME? 29 SELTIA1 Isabel Matos: In today’s episode of “Time Travel News,” we have brought together two of the first scientists to publish ideas on how species evolve, or change over time. Visiting us from the 19th century are Jean-Baptiste Lamarck and Charles Darwin. Monsieur Lamarck, let’s start with you. Jean-Baptiste Lamarck: I was one of the first to recognize that species change over time. In 1809, I proposed the first theory of how species change over time. Allow me to explain my theory. Let’s begin by talking about giraffes. Wendy, why do you think giraffes have such long necks?
A MEETING OF MINDS ACTIVITY 3 EVOLUTION 13 Wendy Chin: To reach leaves at the tops of trees, I guess. They have to be able to get food. Lamarck: Quite right. I began to wonder how giraffes’ necks became so long. My theory was that giraffes stretched their necks by reaching for leaves that were higher and higher on the trees. This made their necks longer. Then, when they had babies, their babies had longer necks too. Look—this sketch helps explain my ideas. Wendy: Shouldn’t a theory be based on evidence? Matos: Mr. Lamarck, did you ever see an adult giraffe grow its neck longer? Lamarck: Of course not. My idea was that the growth was very small, too small to measure in one generation. Charles Darwin: I’d like to explain another theory, called natural selection. Alfred Russel Wallace and I constructed this theory at about the same time. We also noticed that not all animals of the same type have the same features. Take horses, for instance. Wendy: Oh, I know what you mean! There are horses of different sizes and colors, but they are all one species and can interbreed. This is an adult giraffe. The giraffe reaches for leaves slightly out of reach. The use of the neck causes it to lengthen slightly. The offspring of the giraffe also has a longer neck. Lamarckian Evolution
ACTIVITY 3 A MEETING OF MINDS 14 EVOLUTION Darwin: Exactly—and the same is true of giraffes. Have you noticed that animals in the same species look different, or varied? This is important because in the wild, some animals in each species usually die every year. Only animals that survive can give birth to offspring. Now, what feature of a giraffe might help it survive and live to reproduce? Lamarck: Its neck, of course! As I said before, it must stretch from being used so vigorously. Giraffes can then pass on the longer necks to their children. Matos: But Mr. Lamarck, modern scientists have found no evidence for your hypothesis that parents can pass acquired traits to their offspring. Consider professional wrestlers. They build muscles by lifting weights. But their babies are no stronger than other babies. If these babies want to have muscles like their parents, they have to pump a lot of iron too! Darwin: But just like human babies, not all giraffes are the same. They have slight differences in all their characteristics, including neck length. Lamarck: So, you’re saying that any giraffe that happens to have a slightly longer neck can eat leaves that are higher in a tree than a shorternecked giraffe can and, therefore, is more likely to survive. Wendy: Right—the longer-necked giraffes are more likely to live longer because they can reach more food. If more of these giraffes live longer, they can produce more offspring! Darwin: That’s correct. Animals with certain features, such as giraffes with longer necks, are more likely to live to adulthood and have more babies. We call that process natural selection. Here’s a sketch of how it works: What differences do you observe in these giraffes of the same species?
A MEETING OF MINDS ACTIVITY 3 EVOLUTION 15 Wendy: But why will the offspring of longer-necked giraffes have longer necks, too? Matos: Well, tall parents are more likely to have tall children, aren’t they? The same is probably true of giraffes. Darwin: According to my theory, each new generation of giraffes has, on the average, slightly longer necks than the generation before.30 Lamarck: But not because they stretched their necks? Only because the longernecked giraffes were more likely to survive and reproduce? Wendy: I get it. Individual animals don’t change, but over very long periods of time, the population of an entire species does. Lamarck: But, Mr. Darwin, can your theory of natural selection explain why extinction occurs? Darwin: I believe so. Consider the mammoth, which became extinct a few thousand years ago. Why didn’t mammoths keep changing and continue to survive? Wendy: There are several theories about that. They went extinct during a time when the global climate was warmer than it had been before. The changing climate may have affected the mammoth’s food supply, and human hunters may have contributed to the extinction. 30 NGCCPA1 Giraffes with longer necks tend to reach leaves more easily. Longer-necked giraffes are more likely to eat enough to survive . . . . . . and reproduce. The offspring inherit their parents’ longer necks. Darwinian Evolution (Natural Selection)
ACTIVITY 3 A MEETING OF MINDS 16 EVOLUTION Matos: So, a species becomes extinct when it doesn’t survive an environmental change. No individuals in the population have the traits necessary to survive. Darwin: That’s all it is. The variation in the population isn’t enough to withstand environmental changes. In fact, sooner or later, most species become extinct. Wendy: Let me get this straight. As time passes, species change. The way this occurs is by natural selection—some individuals in a population happen to be better suited to the environment, and they’re more likely to survive and reproduce. Lamarck: As a result, the population as a whole over many generations comes to have the trait that increases survival, such as a giraffe’s long neck. A trait that becomes more common because it increases survival and reproduction is called an adaptation. 3132 Matos: Today, we know that we pass on characteristics like longer necks to our offspring through genes. Genes don’t change because you exercise your neck. Darwin: Tell us more about these genes. Wendy: I learned about genes in school. Genes are parts of our cells that we inherit from our parents. They determine our traits, like hair color and eye color.33 Lamarck: Fascinating. I would like to learn more about this. Darwin: Without this modern evidence, I hesitated to publish my theory for years, until Wallace sent me a brief paper containing the same ideas. Within a few years of our publications, our ideas were widely accepted. Matos: Scientists now understand that natural selection is the process that results in the survival and reproductive success of individuals who have inherited traits that are adapted to their current environment. Thank you, Mr. Lamarck and Mr. Darwin. Viewers, I hope you’ve enjoyed meeting people from our past. Join us next week for a scintillating conversation with Marie Curie, the first woman scientist to receive a Nobel Prize.34 31 NGLS4C1 32 NGCCCE2 33 NGLS3B2 34 NGLS4B1
A MEETING OF MINDS ACTIVITY 3 EVOLUTION 17 ANALYSIS 1. Compare and contrast Lamarck’s and Darwin’s theories of change over time.35 a. What are the similarities? What are the differences? b. Why do scientists find Darwin’s theory more convincing than Lamarck’s?36 2. Earthworms are beige or brown, not green.3738 a. Explain why this is, using Darwin’s theory of natural selection. b. Explain why this is, using Lamarck’s theory of change. 3. Explain whether Darwin’s theory or Lamarck’s theory is a better explanation for your results in the “Hiding in the Background” activity. Hint: Be sure to cite evidence from that activity.3940 35 ELWH689 36 NGSPEA2 37 NGSPCE2 38 ELRS682 39 NGSPCE2 40 SEASEX1
EVOLUTION 19 4 Battling Beaks m o d e l i n g As you learned in the activity “A Meeting of Minds,” Darwin’s theory of natural selection explains how species change over time, or evolve. This process of change over time is called evolution. But for natural selection to lead to evolution, there must be differences among individuals within that species. In the toothpick-worms example, some were green while others were beige. In the bacteria example, some individuals were highly resistant to antibiotics, some were slightly resistant, and others were not resistant at all. In this activity, you will further explore the role that these differences play in natural selection.41424344 GUIDING QUESTION What role does genetic variation play in the process of natural selection? 41 NGLS2A2 42 NGLS4B1 43 NGLS4C1 44 NGLS3A1 What can explain the phenomenon that that are so many kinds of bird beaks and bills?
ACTIVITY 4 BATTLING BEAKS 20 EVOLUTION MATERIALS For each group of four students 4 plastic forks with 1 tine 4 plastic forks with 2 tines 4 plastic forks with 4 tines 4 plastic cups 1 number cube 1 Battling Beaks Arena 1 cup of “wild loops” For each student 1 piece of graph paper PROCEDURE 45 1. Make a data table in your science notebook to keep track of the three kinds of forkbirds: 1-tined, 2-tined, and 4-tined. Your table should have enough rows for the initial generation and 10 subsequent generations.46 2. The initial forkbird population has beaks with only 2 tines. Each person in your group should begin the activity with a 2-tined fork. Record the initial population of each type of forkbird in your data table. 3. Your teacher will tell you when feeding time begins, and then all the forkbirds can feed. 4. When feeding time ends, count the number of wild loops eaten by each forkbird. 45 NGSPDM1 46 ELRS683 The Forkbird Model In this activity, you will role-play a single species called forkbirds. Forkbirds feed by either spearing or scooping their food. During feeding time, each bird gathers “wild loops” and immediately deposits them into its “stomach” before gathering more food. Your goal is to gather enough food to survive and reproduce. This will allow you to pass your genes on to another generation. Occasionally, a forkbird offspring will have a genetic mutation that makes it look different from its parent.
BATTLING BEAKS ACTIVITY 4 EVOLUTION 21 5. Within your group, the two forkbirds that gathered the most food survive to reproduce. (If there is a tie for second place, then three forkbirds survive. The two forkbirds that tie should keep their forks and skip Step 6.) 6. Depending on whether you survived or not in Step 5, complete step a or b as follows: a. The group members whose forkbirds did not survive should set their forks aside. They now assume the role of the offspring in the next round. b. The two surviving forkbirds (or one forkbird if there was a tie for second place) should each toss the number cube to see if any mutations occur when they reproduce. A mutation is a change in a gene that may cause a change in a trait. Use the following table to determine the type of beak of the offspring of each surviving forkbird. They should hand a new fork with the correct number of tines to the group members who are now playing the role of offspring. 4748 Number Cube Key YOUR TOSS FORKBIRD OFFSPRING 1 1-tined forkbird 2 2-tined forkbird 4 4-tined forkbird 3, 5, 6 same as parent forkbird 7. Record the new population of each type of forkbird in your group in the next row in your data table. 8. Return all the wild loops to the “forest floor” (tray or bin) to simulate the growth of wild loops. 9. Repeat Steps 3–8 for nine more rounds to represent additional generations, being sure to fill in your data table after each round. 10. Share your data with the class as directed by your teacher. As a class, record the population of each type of forkbird over many generations. Record the class data in your science notebook. 47 NGLS3B2 48 NGLS3A1
ACTIVITY 4 BATTLING BEAKS 22 EVOLUTION 11. Create a graph of the class totals of each type of forkbird over many generations. Plot the data for all three types of forkbirds on a single graph. Be sure to title your graph, label your axes, and provide a key.4950 ANALYSIS 1. Look at your graph of the class results. 51 a. Describe what happened to the number of each type of forkbird over many generations.52 b. Which type of forkbird was the most successful? Explain how the class data support this conclusion.5354 2. The forkbirds that you studied are a single species. Although they look slightly different, they are part of a single interbreeding population. Now imagine that a change in the food supply occurred.55 a. As a result of heavy rains, the major source of forkbird food is now soft berries, like blueberries. After many, many generations, how many types of forkbirds do you think will be in the population? Explain your reasoning.56 b. As a result of a drought, the major source of forkbird food is now sunflower seeds. After many, many generations, how many types of forkbirds do you think will be in the population? Explain your reasoning.57 3. In this activity, mutations were introduced. Consider the effects of the mutations on your forkbirds. Classify each mutation as beneficial, neutral, or harmful. Explain your reasoning, using evidence from your investigation. 58 4. What are the strengths and weaknesses of the forkbird model for explaining evolution by natural selection?5960 5. Using the forkbird model, explain the role of mutations in changes in populations due to natural selection.6162636465666768 6. Revisit the issue: How might people be changing the kinds of resources available to organisms and therefor affecting natural selection and evolution? 49 NGSPUM1 50 NGSPAD1 51 NGCCPA1 52 MARP6A1 53 NGSPAD1 54 MASP6B5 55 NGLS2A2 56 NGCCSF1 57 NGCCCE2 58 NGLS3B2 59 NGSPDM1 60 SEASMD1 61 NGSPCE2 62 NGPEL44 63 SEASEX1 64 NGLS4B1 65 NGLS4C1 66 NGLS3B2 67 ELWH682 68 NGLS3A1
BATTLING BEAKS ACTIVITY 4 EVOLUTION 23 EXTENSION If you were to conduct the activity with a 12-sided number cube, using the rules in the following table, what do you predict would be the outcome? Hint: Think about time. Number Cube Key YOUR TOSS FORKBIRD OFFSPRING 1 1-tined forkbird 2 2-tined forkbird 4 4-tined forkbird 3, 5, 6, 7, 8, 9, 10, 11, 12 same as parent forkbird
EVOLUTION 25 5 Mutations: Good or Bad? m o d e l i n g I n the previous activities, you explored how the environment influences the selection of traits. These traits are determined by bits of inherited genetic information called genes. Humans have approximately 20,000 different genes, each one giving rise to a product whose function influences your traits. The forkbirds in the previous activity have a gene that determines the structure of the beak. As you learned, variations in traits are sometimes caused by a mutation (or a change to the sequence of a gene). If the mutation leads to an advantageous trait, the mutation can be considered beneficial. Other times, the mutation may have a negative effect or no effect at all. Sometimes, whether a mutation is beneficial, harmful, or neutral depends on the environment. You observed with the forkbirds that the best beak shape depended on the food sources in the current environment.69 In this activity, you will investigate how natural selection affects the presence of mutations in a human population. You and your classmates will model a community in a remote part of sub-Saharan Africa. As a class, you will investigate how a mutation could be beneficial, harmful, or neutral to your family and the community.70 GUIDING QUESTION How do mutations affect survival? 69 NGLS4C1 70 NGLS4B2 Are these color mutations beneficial, harmful, or neutral?
ACTIVITY 5 MUTATIONS: GOOD OR BAD? 26 EVOLUTION MATERIALS For the class 34 hemoglobin plastic disks For each student 1 First Generation Profile Card 1 First Generation Survivor Profile Card 1 Student Sheet 5.1, “Hemoglobin Mutations and Natural Selection” 1 Student Sheet 5.2, “Hemoglobin and Red Blood Cells Storyboard” PROCEDURE Part A: Generation One—The Initial Population 1. Read the background information in the box about hemoglobin and sickle cell anemia. 717273 71 NGCCSF1 72 NGLS3A1 73 NGCCCE2 Background Information— Hemoglobin and Sickle Cell Anemia Hemoglobin is a protein inside all red blood cells. This protein gives the red blood cells their color. Hemoglobin’s function is to carry oxygen to cells throughout the body. Some people have a mutation in the hemoglobin gene that gives rise to an altered protein called hemoglobin S. Hemoglobin S has an abnormal structure that causes the mutated hemoglobin proteins to stick together in chain-like structures. These chains of hemoglobin S cause normal disc-shaped red blood cells to curve into sickle shapes, as shown below on the right, next to a normal red blood cell. These rigid sickle cells can clump together and block the normal function and flow of blood through the body.
MUTATIONS: GOOD OR BAD? ACTIVITY 5 EVOLUTION 27 As shown in the map below, the hemoglobin S mutation is most common in sub-Saharan Africa, Mediterranean countries, the Middle East, and India, although it may occur anywhere. In all of our cells, there are two copies of each gene, one from our biological mother and one from our biological father. Worldwide, the majority of people have two normal hemoglobin genes. This can be represented by the letters HH, where the uppercase H represents a normal copy of the hemoglobin gene. If a person inherits one mutated copy of the hemoglobin gene, they are referred to as a sickle cell carrier. This can be noted as Hh, where the lowercase h represents the mutated hemoglobin S gene. In these carriers, half of their hemoglobin protein structure is normal, and half is abnormal. The abnormal hemoglobin protein structures can stick together, but since the other half of their hemoglobin is normal, the chains are not long enough to cause the cells to form sickle shapes. The cell structure still allows it to function normally and carry oxygen. If a person inherits two mutated copies of the gene, they are said to have sickle cell anemia, and their genes are represented as hh. GENES RED BLOOD CELL TRAIT HH normal Hh sickle cell carrier hh sickle cell anemia LabAids SEPUP IAPS Evolution 3e Figure: Evo3e SB 5_3 MyriadPro Reg 9.5/11 0.1–0.2% 0.03–0.09% Hemoglobin S frequency Frequency of the Hemoglobin S Mutation
ACTIVITY 5 MUTATIONS: GOOD OR BAD? 28 EVOLUTION 2. Obtain a First Generation Profile Card from your teacher, and read the information on the card. Note your red blood cell trait— are you Normal, are you a Sickle Cell Carrier, or do you have Sickle Cell Anemia?—and what your blood cell structure looks like. 3. On Student Sheet 5.1, “Hemoglobin Mutations and Natural Selection,” record the numbers of individuals in your class with each trait in the “Beginning population” column in the table for Part A: The Initial Population (Class Data). 4. In the remote sub-Saharan African region where your community settled, there is no access to resources such as health care. There is also a high incidence of malaria in this region. Read the following information to learn more about malaria: Malaria is a disease caused by a parasite that infects your red blood cells. The parasite is introduced into your body when a mosquito carrying the parasite bites you. Inside your red blood cells, the parasite multiplies to further infect more red blood cells. The parasite can also travel throughout your body, since your blood is constantly flowing to all of your body parts. Over time, your red blood cells rupture, leading to blood loss and release of the parasite into your body. People who get malaria become very sick with high fevers, shaking chills, and flu-like symptoms. If not promptly treated, malaria may lead to death. The map below indicates where in the world malaria is transmitted. LabAids SEPUP IAPS Evolution 3e Figure: Evo3e SB 5_4 MyriadPro Reg 9.5/11 malaria transmission occurs throughout malaria transmission occurs in some parts Global Transmission of Malaria
MUTATIONS: GOOD OR BAD? ACTIVITY 5 EVOLUTION 29 5. Follow your teacher’s instructions to determine the number of individuals who survive the malaria outbreak in your community. • Almost all sickle cell anemic individuals do not survive to reproductive age, due to lack of diagnosis or treatment of the sickle cell disease. • Normal individuals have a 50% chance of surviving malaria. • Sickle cell carriers have an 80% chance of surviving malaria. 6. Record the number of surviving individuals in the table on your Student Sheet. Part B: The Next Generation 7. The individuals who survived malaria grew up and partnered with individuals from a neighboring community. Obtain a new First Generation Survivor Profile Card from your teacher. 8. Your profile card has an assigned letter and number (examples: A1, A2). Find your partner with the same letter on their Profile Card: A1 should partner with A2, B1 should partner with B2, etc. 9. Obtain an HH, Hh, or hh hemoglobin plastic disk from your teacher that matches your hemoglobin genes. Toss the disk (like you would toss a coin) to determine which version of your two genes you will pass on to each offspring. You will do this five times. Record the genes that each of you pass to your first five offspring in the “Your Data” table on Part B on your Student Sheet. 10. Record the number of offspring in your class with each trait in the “Beginning population” column of the “Class Data” table in Part B on your Student Sheet. 11. Follow your teacher’s instructions to determine the number of offspring who survive the malaria outbreak in your community, and record these values on your Student Sheet. 12. Make two bar graphs with your data for Generation 2: one showing the starting population, and one showing the surviving population. Alternatively, you can combine both sets of data into one bar graph. Be sure to title your graph(s), label your axes, and provide a key. 74 Hint: If you choose to make two graphs, consider making the scale of both graphs the same because you will compare them to each other. 74 NGSPUM1
ACTIVITY 5 MUTATIONS: GOOD OR BAD? 30 EVOLUTION ANALYSIS 1. Look at the numbers of individuals you recorded on Student Sheet 5.1 and the bar graph(s) you created. Compare the number of individuals with each trait in the beginning population to the surviving numbers. What patterns do you notice?757677 2. In your community, half the normal and all the sickle cell anemic individuals died. Explain how normal and sickle cell anemic offspring were born in the second generation.78 Hint: Remember that you have two copies of each gene, one from each parent. 3. Use Student Sheet 5.2, “Hemoglobin and Red Blood Cells Storyboard,” to develop a model to explain the relationship between a mutation in a gene and the structure and function of an organism. 798081 • Be sure to include the genes, the protein, the red blood cell, and the organism in all three cases—a normal individual, a carrier, and a person with sickle cell anemia. • Follow your teacher’s instructions for how to represent the genes, protein, red blood cell, and organism. 4. Hemoglobin S is caused by a single mutation in the hemoglobin gene. Explain how the environment affects whether this mutation is beneficial, harmful, or neutral for a person. Use evidence from your investigation to support your explanation. 82 5. Compare the “Frequency of Hemoglobin S Mutation” and “Global Transmission of Malaria” maps seen earlier in this activity. What is the evidence for a cause-and-effect relationship between the frequency of malaria and the frequency of the hemoglobin mutation?83 75 NGCCPA2 76 MARP6A1 77 MASP6B5 78 NGLS3A1 79 SEASMD1 80 NGSPDM1 81 NGPEL31 82 NGSPCE2 83 NGCCCE2
EVOLUTION 31 6 Mutations and Evolution c o m p u t e r s i m u l at i o n By now you know that some traits are more advantageous than others in certain environments. Variations in traits result from mutations. Over time, the frequency of variations in a population can change. This change in trait frequency resulting from natural selection is central to the process of evolution. 8485 In this activity, you will continue studying the community in sub-Saharan Africa that you began investigating in the last activity. You will use a computer simulation to predict and analyze how trait frequency changes in your population when there is a change in the environment, such as improvements in health care or decreased levels of malaria. GUIDING QUESTION Why does sickle cell trait frequency vary across the world? 84 NGLS4C1 85 NGLS4B1 Plasmodium infecting red blood cells
ACTIVITY 6 MUTATIONS AND EVOLUTION 32 EVOLUTION MATERIALS8687 For each pair of students computer with Internet access PROCEDURE Part A: Simulating More Generations 1. Visit the SEPUP Third Edition Evolution page of the SEPUP website at www.sepuplhs.org/middle/third-edition and go to the sickle cell simulation. 2. Set the variables to match your community from the previous activity.88 a. Percent chance of getting malaria: This is the percentage chance for each individual of getting malaria, or the incidence rate. The available choices are 0, 25, 50, 75, or 100%. In your community, the chance of getting malaria is 100%. b. How good is the health care: This is the level of health care and resources available. Three levels are available: no health care, OK health care, or great health care. Your community has no health care. 3. Press “Run Simulation.” The simulation will generate two graphs with your results: • Graph 1: This bar graph shows how many children survived to adulthood and reproduced in each generation. This graph is similar to the graph you produced in the “Mutations: Good or Bad?” activity. • Graph 2: This line graph shows the percentage of each trait in the population for each generation over time. 86 NGLS3A1 87 NGLS3B2 88 NGSPUM1 Sickle Cell Simulation In the “Mutations: Good or Bad?” activity, you started a community in a remote part of sub-Saharan Africa and followed the sickle cell trait through two generations. Now you will examine up to 30 generations of your community in the same environment. You will then investigate how changes in the environment are likely to affect your population. These changes could include resources that help maintain health, such as building health clinics in your region or investing in better pest control to minimize the mosquito population.
MUTATIONS AND EVOLUTION ACTIVITY 6 EVOLUTION 33 4. Record your results and any additional data or observations in your science notebook. Be sure to note any questions you have that you would like to test.89 5. Answer Analysis item 1 in your science notebook. Part B: Changing Environments 6. Use the simulation to test how changing the environment affects the frequency of the sickle cell trait in your population. Change the variables to alter the percent chance of getting malaria or the quality of health care. Hint: Change one variable at a time. a. Record your variables and the results in your science notebook. b. Write down any other questions that you would like to test. c. Continue to do this until you can explain the cause-and-effect relationship between the variable and the frequency of sickle cell carriers in the population. ANALYSIS 1. Use the data you collected or observations you made about the environment to complete the following:9091 a. Use a mathematical representation, like a ratio or percent, to explain what happened to the frequency of the sickle cell trait over time when the chance of getting malaria was high and there was no health care. 9293 b. Is there a cause-and-effect relationship? If so, describe that relationship. If not, explain why not.94 2. Explain how environmental changes affect the sickle cell trait over time in your population. Use evidence, including mathematical representations, from your investigation to support your explanation.95969798 3. Explain why the frequency of sickle cell trait is so much higher in sub-Saharan Africa than in most other parts of the world. 4. What do you think would happen to the sickle cell trait in an environment with no malaria and increased resources? Explain your prediction. 5. Revisit the issue: How might people be changing the environment, and therefore how they are affected by evolution? 89 NGCCPA2 90 MARP6A1 91 MASP6B5 92 NGSPUM1 93 NGCCPA2 94 NGCCCE2 95 NGPEL46 96 NGSPCE2 97 NGCCSF1 98 SEASEX1
EVOLUTION 35 7 Origins of Species v i e w a n d r e f l e c t So far, you have seen how natural selection leads to evolutionary changes within a species over time. For example, when a food source that a bird species eats becomes scarce, any bird with a mutation (for example, a particular beak shape) that allows it to feed on a more common food source will have an advantage. These individuals are more likely to survive and pass on the trait for this different beak shape to their offspring. Over time, the percentage of the population with this different beak shape will increase. But what happens when this change occurs over hundreds or thousands of generations? GUIDING QUESTION 99 How do new species evolve? 99 NGLS4C1 A Galapagos finch Ecuador’s Galapagos Islands, 1,400 km from the coast of South America LabAids SEPUP IAPS Evolution 3e Figure: Evo3e SB 7_2 MyriadPro Reg 9.5/11 Equator Pacific Ocean Bolivia Colombia Venezuela Peru Brazil Guyana Ecuador Caribbean Sea Galapagos Islands
ACTIVITY 7 ORIGINS OF SPECIES 36 EVOLUTION MATERIALS For each student 1 Student Sheet 7.1, “Viewing Guide: Galapagos Finch Evolution” PROCEDURE 1. To prepare to watch the video on Galapagos finch evolution, read through Student Sheet 7.1, “Viewing Guide: Galapagos Finch Evolution.” 2. Watch the story of Galapagos finch evolution.100 3. Complete Student Sheet 7.1. ANALYSIS 1. Explain how environmental factors, genetic variation, and natural selection resulted in the evolution of the 13 Galapagos finch species observed today, when originally there was just one finch species on the islands.101102103104105106107108 2. Do you predict that the same 13 finch species that exist today in the Galapagos Islands will exist in 1 million years? Explain. 109110 100 ELRS689 101 NGLS4A1 102 NGLS3B2 103 NGLS4C1 104 NGCCCE2 105 NGSPCE2 106 SEASEX1 107 ELWH682 108 NGLS4B1 109 NGLS4A2 110 NGCCPA1 LabAids SEPUP IAPS Evolution 3e Figure: Evo3e SB 7_3 MyriadPro Reg 9.5/11 small ground medium ground large ground cactus large cactus sharp-beaked ground small tree large tree medium tree mangrove woodpecker vegetarian warbler mainland Evolutionary Tree for Galapagos Finches
ORIGINS OF SPECIES ACTIVITY 7 EVOLUTION 37 3. How does the “Evolutionary Tree for Galapagos Finches” figure above represent the evolution of the 13 species?111 4. What qualities do you think Peter and Rosemary Grant have that led to their becoming successful scientists?112 EXTENSION 1 Visit the SEPUP Third Edition Evolution page of the SEPUP website at www.sepuplhs.org/middle/third-edition and watch the Evolution in Action in Salamanders video. Reflect on whether you think these salamanders are becoming different species. EXTENSION 2 Visit the SEPUP Third Edition Evolution page of the SEPUP website at www.sepuplhs.org/middle/third-edition and go to the Grant Data link to examine the actual data collected by the Grants on the medium ground finch. Other than beak size, did the birds that survived the 1977 drought show any other differences from the birds that didn’t survive? If you detect any other patterns, what might be the cause of those patterns? If not, why do you think there was no relationship? 111 NGCCPA2 112 NGCCCO1
EVOLUTION 39 8 History and Diversity of Life r e a d i n g I n the previous activity, you learned how new finch species evolved over 3 million years on the Galapagos Islands. But the finches are just one small branch of the tree of life. Earth is large and over 4 billion years old! How many different species have evolved on Earth? Are they all still present today? GUIDING QUESTION How are the diverse species living today related to one another and to the species that once lived on Earth? An intriguing phenomenon is that there are 350,000 species of beetles (pictured here alongside other insects)
ACTIVITY 8 HISTORY AND DIVERSITY OF LIFE 40 EVOLUTION MATERIALS For each student 1 Student Sheet 8.1, “Vertebrate Evolutionary Tree” PROCEDURE 1. Read the following text.113114 2. Follow your teacher’s instructions for how to use the Stop to Think questions. You will need Student Sheet 8.1, “Vertebrate Evolutionary Tree,” for Stop to Think 1. Evolutionary Trees115116117118 As you learned in the activity “Origins of Species,” all Galapagos finches evolved from one ancestral species that arrived on the islands approximately 3 million years ago (abbreviated mya). An ancestral species is the most recent species from which two or more species evolved. That original Galapagos finch species evolved from a previous ancestral species that also gave rise to other bird species. If we go back far enough in time, all birds are descended from the original bird species. Scientists estimated that this original bird species evolved approximately 150 mya. The ancestor, or common relative from the past, of the first bird species was also the ancestor of reptiles like crocodiles. While the evolution of birds followed one branch of the evolutionary tree, the evolution of crocodiles followed another. Another way to say this is that both birds and crocodiles descended from the same ancestor. If we go back even further, the common ancestor of birds and crocodiles is also the common ancestor of mammals, including humans. Evidence from fossils suggests that mammals split apart from birds/ crocodiles about 200 mya. In a similar way, we can keep going back in time to find evidence of the ancestral species for all significant forks in the evolutionary tree. Amphibians, like frogs and salamanders, split apart approximately 370 mya. Fish split apart about 530 mya. Fish, amphibians, reptiles, birds, and mammals are all considered vertebrates, which means that the first vertebrate diverged from invertebrates 530 mya. And these events are actually quite recent! The evidence of the first life on Earth, bacteria, goes back to at least 4.28 billion years ago (bya). 113 ELRS687 114 SELTST1 115 NGLS4A1 116 NGLS4A2 117 NGCCPA2 118 NGCCPA1 LabAids SEPUP IAPS Evolution 3e Figure: Evo3e SB 8_2 MyriadPro Reg 9.5/11 A D B C E D is the ancestral species for B and C. B and C descended from D. E is the ancestral species of A and D. E is the common ancestor of all the other species.