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1 Microbial Discovery Activity Earth History: Time Flies,, No Matter What the Scale Author Robin Patterson, PhD Butler County Community College Butler, PA Contributor Liliana Rodriguez, MPH, RM(AAM), M(ASCP) The University of Texas Health Science Center School of Public Health at Houston Intended Audience K X Activity Characteristics Classroom setting Uses hands-on manipulatives Requires group work Requires mathematical skills X X X X American Society for Microbiology Education Department 1752 N Street, NW Washington, DC EducationResources@asmusa.org

2 Introductiion Description In this exercise students apply their mathematical skills to relate a geological time scale to a yearly calendar to describe Earth's history in a fun and entertaining way. Abstract In this two-part activity, which uses discovery and an inquiry approach, the participants will be given cartoon drawings representing significant events in the history of the Earth and asked to place them on a timeline made of colored ribbon. Then they mathematically relate the geologic time scale to a yearly calendar. After the calculations, they return to the timeline to reassess the placement of the events. Core Themes Addressed General Science Concepts Microbial Cell Biology Microbial Genetics Microorganisms and Humans Microorganisms and the Environment Microbial Evolution and Diversity Other -Common properties of life; Cellular components X X Keywords Earth history, microbial evolution, historical events, time scales. Learning Objectives At the completion of these activities students should be able to: Identify significant events in microbial evolution Translate information from one mathematical scale to another Understand the perennial dominance of microbes, past and present Understand the order of key events in evolution relating to microbes Gain an appreciation about the place of microbes in earth's history Acknowledgements This activity was adapted from Earth History: A Microbial Story authored by Dr. Douglas Zook from Boston University. It was originally published in his 1992 book The Microcosmos Curriculum Guide to Exploring Microbial Space, from Kendall-Hunt Publishing. We thank Dr. Zook for granting permission to use parts of his exercise and the cartoon illustrations. The artist is Ann Powers, BFA from Tufts University and the School of the Museum of Fine Arts, Boston. For more information about his book see the supplementary information section of the Teacher's handout. Earth History: Time Flies, No Matter What the Scale Page 2

3 National Science Education Standards Addressed Science Content Standards Earth and Space Science Evolution of the earth system 2. Life Science Biological evolution Earth History: Time Flies, No Matter What the Scale Page 3

4 Teacher Handout Earth History: Time Flies, No Matter What the Scale Student Prior Knowledge Students need mathematical (algebraic) skills, know how to use a calculator, and have some knowledge about the geological history of Earth. Teacher Background Information This exercise provides a timeline of the evolution of life through the major events in the development of life on the planet Earth. Ten cartoon illustrations are provided, each corresponding to a major event in evolution. Students can work in groups to organize these cartoons in chronological order. You can use the Earth Time line chart below to start a discussion about major biological or geological events on Earth's history prior to the activity, or give the students an assignment to be completed before class. You can ask them to research cyanobacteria as the initial inventors of photosynthesis and the creation of stromatolites. There are several excellent resources and websites for them to review the topic, such as The Museum of Paleontology at UC at: [ and the book The Microcosmos Curriculum Guide to Exploring Microbial Space, from Kendall-Hunt Publishing. Class Time Approximately one hour class time is required but can be shortened by reducing the number of events to be studied. Teacher Preparation Time About 30 minutes to make photocopies and one set of overhead transparencies of the cartoon illustrations, and taping pieces of ribbon on the classroom walls. Earth History: Time Flies, No Matter What the Scale Page 4

5 Materials and Equipment One set per group: 1. Photocopies of student worksheets and cartoon sheets. The cartoon sheets can be reduced in size and laminated for re-use. 2. Paperclips or clothes pins 3. Five colors of ribbon or streamers, each at least 5 feet long, connected together to make one long string. Color choice is not critical. 4. Masking tape 5. Calculator 6. Correlation of events worksheet 7. Calendar template Methods 1. Photocopy the cartoon illustrations. It is useful to photocopy the illustrations on colored paper. You can either use one color for each event or you can use one color for each group. 2. You may want to make overhead transparencies to assist with class discussion of the events. 3. Before class, tape together the lengths of ribbon and extend the ribbon around the room, taping to the wall wherever necessary. 4. Distribute one set of cartoons, one correlation of events worksheet, and one calendar template per group. Safety Precautions None Assessment Have the students complete the correlation of events worksheet in small groups and report back to the larger group about their conclusions. Supplementary Information Earth Time line, worksheet, calendar, cartoon illustrations and their descriptions are listed on the following pages. The 500-page Microcosmos Curriculum Guide to Exploring Microbial Space can be purchased for $40 ($ $5 S&H). Send a check made out to Int l Symbiosis Society to: Microcosmos Project/ISS c/o Dr. Douglas Zook Boston University Two Sherborn Street Boston, MA dzook@bu.edu There is also an updated 16 image new overhead transparency set that replaces the existing one in the Earth History activity of the book for $35 (Includes shipping and handling). Earth History: Time Flies, No Matter What the Scale Page 5

6 Earth Time Line Cartoon Era Period Years Ago Billions of Geological and Biological Events Years Ago 1. Cosmic Dust Archean 4,600,000, * Origins of earth and our solar system 2. Extended Rain 4,200,000, Changes that led to creation of oceans and other bodies of water Forecast 3. Primordial Soup Proterozoic 3,900,000, End of major impacts by other particles. Self-copying chemicals form in the hot broth of early Earth forming the bricks for life. First unicellular microorganisms 4. Oxygen Factory 2,500,000, Photosynthetic microbes (cyanobacteria) produce oxygen. Increase of O2 leads to begining of banded iron formations. 5. Eukaryotic Cell 1,400,000, First eukaryotic organisms evolve. 6.Let's Get Together 1,000,000, Begining of multicellular eukaryotes 7. Plants Race Animals Paleozoic Silurian 438,000, First plants able to colonize land 8. Eek Mammals! Mesozoic Triassic 248,000, (220MYA) First mammals appear 9.Trouble in Pangea Jurasic 225,000, Separation of a single land mass into continents 10. Homo sapiens Cenozoic Quaternary 2,000, First humans appear * If you were to count to 4.6 billion (one number per second) it would take nearly 150 years! Earth History: Time Flies, No Matter What the Scale Page 6

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17 Key to Cartoon Illustrations (from the most ancient event). 1. When Cosmic Dust Goes Unswept (4.6 billion years ago) The earth is about 4.6 billion years old. This cartoon represents the origins of the universe. It is theorized that the universe began to expand over 8 billion years ago, quickly passing from the age of energy to the age of matter. The earth itself was formed about 4.6 billion years ago. The early earth was a land of molten rock and violent volcanic activity. The earth s crust was solidifying at this time, called the Hadean eon, since no rocks have been found that exceed 4.3 billion years old. These rocks show no traces of life (or at least none that can be traced with our current level of technology) Million Years of Rain (4.2 billion years ago) As the earth was forming, gasses were released from the molten core in volcanic activity. These gasses formed a cloud around the earth and were held as an atmosphere by the earth s gravity. At first the earth was so hot that water was present only as a vapor. As the earth cooled and the crust formed the vapor condensed to liquid water and the rain began to fall. It rained such an enormous quantity over millions of years that the oceans of the world were formed. The atmospheric gasses were dissolved in this rain. 3. Primordial Soup (4 billion years ago) The atmospheric gasses that were dissolved in the rain may have reacted with one another in the presence of the enormous amount of energy present on the planet to produce small organic molecules. Neither oxidation (there was no free oxygen) nor decay (there were no bacteria) would have destroyed these molecules and they would have accumulated in the oceans for hundreds of millions of years. With the accumulation of the small organic compounds, the oceans became a thick, warm organic soup containing a variety of organic molecules. The newly-formed organic molecules likely polymerized to produce still larger molecules and eventually a protocell arose. This structure would likely have had a lipid - protein membrane that carried on anaerobic energy metabolism and was a heterotroph (an organism that took in preformed food), fermenting the food with some degree of enzymatic activity. Once these protocells were self-replicating, they became true cells and biological evolution began. 4. Oxygen Factory (2.5 billion years ago) The evolution of photosynthesizing organisms caused oxygen to enter the atmosphere. The atmosphere became oxidizing rather than reducing. Oxygen in the upper atmosphere formed ozone, which filtered UV light. The presence of oxygen also meant that most environments were unsuitable for anaerobic prokaryotes. Photosynthetic cyanobacteria and aerobic bacteria proliferated as new metabolic pathways evolved. Earth History: Time Flies, No Matter What the Scale Page 17

18 5. Endosymbiont Recruitment (1.5-2 billion years ago) Most likely the eukaryotic cell evolved from the prokaryotic cell, acquiring its organelles gradually. The nucleus may have developed by an invagination of the plasma membrane. The mitochondria may have been free-living aerobic prokaryotes and the chloroplasts may have been free-living cyanobacteria. Life was still aquatic at this point. 6. Love at First Sight (1 billion years ago) It is not known when multicellularity began but the first multicelled creatures were likely microscopic. Sexual reproduction would have its origins here and would have been an important first step toward the development of complex macroscopic organisms. The geologic period is the Precambrian era. 7. Plants Race Animals to Land (438 million years ago) The Cambrian and Ordovician periods saw the marine algae and marine invertebrates flourish. During the Silurian period (408 to 438 million years ago) low lying primitive vascular plants appeared on land and the first jawed fishes appeared in the oceans. During the Devonian period, the first seed ferns appeared ( million years ago). 8. EEK Mammals! (248 million years ago) The first reptiles appear in the Carboniferous period million years ago (mya). During the Triassic period, the first dinosaurs and mammals appear (200 mya). Placental mammals appear during the Cretaceous period - about 100 mya. 9. Trouble in Pangea ( million years ago) The Continental Drift theory, proposed by Alfred Wegener, states that the continents are not fixed and instead, their positions have changed over time and continue to change. About 225 mya, the continents were joined to form one supercontinent called Pangea which then divided into two subcontinents. These split to form the continents of today. Continental drift explains why some coastlines are mirror images of each other (Africa and South America, for example) and why fossils of the same seed fern have been found on all southern continents. Land masses drift due to movement of slablike plates of the earth s crust that float on a hot mantle layer. These slabs are called plates and their movement is called plate tectonics. The plates move because of seafloor spreading at ocean ridges. 10. Living in Concrete Jungle Cartoon (2 million years ago) Monkey-like primates appear about 30 mya. The first hominids appear 2-6 mya and humans appear during the Pleistocene era, 2 mya. Earth History: Time Flies, No Matter What the Scale Page 18

19 Correlation of Events with Modern Calendars Worksheet. One per group Event Time frame a (years ago) Time elapsed b Units c (%) Calendar location (365 day year) a Time frame - length of time before present. BYA = billion years ago; MYA = million years ago. b Time elapsed - length of time since formation of planet. Byr = billion years; Myr = million years. c Units - 5 elapsed. Calculated by dividing Time elapsed for current stop (column 3) by estimated age of Earth (4.5 billion years). Year f - day of 365-day year. Calculated by multiplying 365 days by % of current stop. Earth History: Time Flies, No Matter What the Scale Page 19

20 Calendar Template - One Year Su M T W Th F Sa Su M T W Th F Sa Su M T W Th F Sa January February March April May June July August September October November December Earth History: Time Flies, No Matter What the Scale Page 20

21 Event Correlation of Events with Modern Calendars Answer Key Time frame a (years ago) Time elapsed b Units c (%) Calendar location (365 day year) BYA 0 0 Day 1 (Jan 1) BYA 0.3 BYR 6.7 Day 24 (Jan 24) 3 4 BYA 1.8 BYR 13.3 Day 49 (Feb 18) BYA 2.5 BYR 44.4 Day 162 (June 10) BYA 3.05 BYR 66.7 Day 243 (Aug 30) BYA 3.5 BYR 77.8 Day 284 (Oct 12) MYA MYA MYA 10 2 MYA 3,910 MYR 3,995 MYR 4,062 MYR 4,140 MYR 90.3 Day 330 (Nov 22) 94.5 Day 345 (Dec 7) 95 Day 347 (Dec 9) Day 365 (Dec 31) a Time frame - length of time before present. BYA = billion years ago; MYA = million years ago. b Time elapsed - length of time since formation of planet. Byr = billion years; Myr = million years. cunits - 5 elapsed. Calculated by dividing Time elapsed for current stop (column 3) by estimated age of Earth (4.5 billion years). Year f - day of 365-day year. Calculated by multiplying 365 days by % of current stop. Earth History: Time Flies, No Matter What the Scale Page 21

22 Student Handout Earth History: Time Flies, No Matter What the Scale Introduction This exercise provides a timeline of the evolution of life through the major events in the development of life on the planet Earth. Nine cartoon illustrations are provided, each corresponding to a major event in evolution. You and the other members in your group be challenged to mathematically relate the geologic time scale of Earth's history to a yearly calendar, and to organize the cartoon in a historical sequence. Vocabulary: Cyanobacteria - Bacteria likely responsible for the creation of earth's oxygen atmosphere. They were the dominant lifeform on Earth for over 2 billion years. Today they are nearly extinct, living a precarious existence in only a few localities worldwide. Photosynthesis - The process by which plants, some bacteria, and some protistans use the energy from the sun to produce sugar, which respiration in the cells converts into ATP, the "fuel" used by all living things. The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll Stromatolites - Communities of microorganisms growing in rock-like buildups of microbial mats that form in limestone- forming environments. These communities include the oldest known fossils, dating back some 3.5 billion years ago. They are prokaryotes(primitive organisms lacking a cellular nucleus) that were abundant in warm aquatic environments and built reefs similarly to the way coral does it today. Materials check list (per group) 1. One set of cartoon illustrations 2. Paperclips or clothes pins 3. Calculator 4. Correlation of events worksheet 5. Calendar template 6. Pencil and eraser Procedure Organizing the Earth's History Time-line 1. As a group, review the cartoon illustrations and deduce the scenario. What event is being depicted in the illustration? How long ago do you think it happened? 2. Using paperclips, affix the cartoons on the ribbon where you think they might belong. One end refers to the present; the other end refers to 5 Billion Years Ago (BYA). Earth History: Time Flies, No Matter What the Scale Page 22

23 3. Return to your seat. Now you will convert the historical date assigned to great events in microbial history into a date within a more familiar time scale to aid you in viewing evolution in its proper scale. Mathematically relate a geologic time scale to a yearly calendar 1. Your team should receive instructions, a worksheet for recording your calculations, a blank calendar covering one year, and a list of events in evolution. 2. Begin by recording the names of your team members on the worksheet. 3. Your team will be assigned events from evolutionary (and geological) history. 4. Perform the calculations and record the results on the worksheet. 5. Once you complete each conversion from historical time to the appropriate time scale, mark the position of that event on the calendar. a. First, identify this "Event" on the worksheet. b. Enter the "Historical date" currently assigned to this event. c. Subtract the historical date from the age of the Earth (4.5 billion years = 4,500 million years). This "Time elapsed" value represents the length of time that passed between the formation of Earth and the occurrence of this event. d. Divide the time elapsed value by the total age of the Earth, and multiply by 100%. This "Percent elapsed" value is the proportion of Earth s history that passed before this event. e. Identify the total time on the calendar (365 days). f. Multiply the percent time elapsed by the total time on the calendar. g. Find and mark this point on the calendar. h. Repeat these steps for each of the events assigned to your team. i. When completed, review your results. j. Submit this assignment as directed by your instructor. An example: Event first cell. Historical date: 3.5 BYA Time elapsed: 4.5 BY 3.5 BY = 1.0 BY Percent elapsed: (1.0 / 4.5 ) x 100% = 22% Length of current calendar: 365 days Location on current calendar: 365 x.22 = 80.3 ANSWER: 1/3 rd through the 81 st day (March 23 rd ). 6. How did you do with the placement of the cartoons on the timeline? 7. Return to the timeline and reposition the cartoons if necessary. Earth History: Time Flies, No Matter What the Scale Page 23

24 Time Flies, No Matter What the Scale Worksheet (Scale = Year) Team Members: Correlation of Events with Modern Calendars Event Time frame a (years ago) Time elapsed b Units c (%) Calendar location (365 day year) a Time frame - length of time before present. BYA = billion years ago; MYA = million years ago. b Time elapsed - length of time since formation of planet. Byr = billion years; Myr = million years. c Units - 5 elapsed. Calculated by dividing Time elapsed for current stop (column 3) by estimated age of Earth (4.5 billion years). Year f - day of 365-day year. Calculated by multiplying 365 days by % of current stop. Earth History: Time Flies, No Matter What the Scale Page 24