Exploring Evolutionary trends in the Cenozoic
This exploration of microfossils in drill core data allows students to investigate evolutionary patterns in marine microfossils, and the potential response of these biota to global change, using the CHRONOS online database. Students generate, using a tool on the website, bar graphs of occurrences of taxa belonging to four types of marine microfossils (planktic foraminifera, calcareous nannofossils, diatoms, and radiolarians) through a chosen ten million year time span of the latest Mesozoic and Early Cenozoic eras (between 70 and 30 million years ago). They examine the bar graphs to determine the ages (to the nearest half-million year) of species' first occurrences and/or last occurrences in this worldwide set of data. The students make a list of these ages that may indicate environmental changes, and then organize the gleaned data as a table in a spreadsheet. Students then use the graphing wizard to produce a bar graph depicting the number of originations and extinctions per half-million years, and interpret it. This interpretation includes a discussion of the overall pattern of rates of evolutionary change in marine microfossil species, speculation on causes of changes (both originations/first occurrences and extinctions/last occurrences of species), and observations of trends in the most active timeframes. The students will consider how life may have responded to external and internal forcing of abrupt change, and develop a fundamental understanding of the reasons for the subdivisions of geologic time (i.e., they are based on naturally-occurring events in Earth history).
Students also use a resource on the CHRONOS website to examine the morphologies of species that disappeared at a point in time when many species were terminated by a catastrophic event, and compare these morphologies to survivors and species that appeared soon after this event. They speculate about the causes for the changes.
- Students develop a fundamental understanding of the reasons for era, period, and epoch divisions of the geologic time scale.
- Students familiarize themselves with planktic foraminifer morphologies on either side of a major geologic boundary by working with real data and scanning electron photomicrographs of type specimens.
- Students use problem-solving skills as they choose a ten million year interval, gather data, make graphs, analyze trends, and interpret the significance of these trends.
- Students learn to use tools available through a large online database of drill cores and other geoscience data.
- Students will learn that the boundary between the Mesozoic and Cenozoic eras (Cretaceous-Paleogene period boundary) is characterized by sudden extinctions and originations of new species. The Paleocene-Eocene and Eocene-Oligocene epoch boundaries are less well defined by catastrophic extinctions and originations with many more species surviving through the environmental changes. The Cretaceous-Paleogene period boundary is marked by a meteorite impact, whereas the other two boundaries were associated with abrupt events in the ocean-climate system, which were less catastrophic to life on Earth.
Context for Use
Description and Teaching Materials
Directions Accessing Micro Fossil Data in Word (Microsoft Word 2.7MB Jul21 07)
Directions Accessing Micro Fossil Data in PDF (Acrobat (PDF) 66kB Jul21 07)
Directions for using the Foraminifer Atlas and Dictionary in Word (Microsoft Word 2MB Jul21 07)
Directions for using the Foraminifer Atlas and Dictionary in PDF (Acrobat (PDF) 98kB Jul21 07)
Evaluation Rubric (Microsoft Word 34kB Jun15 06)
Handout on Evolution (Acrobat (PDF) 1.5MB Jun15 06)
Biozone handout (Acrobat (PDF) 543kB Jun15 06)
Timescale handout (Acrobat (PDF) 336kB Jun15 06)
Exploring the Foraminifera Assignment in Word (Microsoft Word 5.1MB Jul21 07)
Exploring the Foraminifera Assignment in PDF (Acrobat (PDF) 332kB Jul21 07)
Teaching Notes and Tips
Determine student's prior ideas and knowledge by asking them to work in small groups and make a list of ideas of how geologists decide to divide geologic time into Eras and smaller units (Periods, Epochs). Share ideas from groups. (Possible incorrect and correct responses include: they are divided into equal-sized blocks of time; they are divided according to the organisms that lived in them ("Age of dinosaurs"); climate changes; configurations of the continents, major Earth events).
Explain to students that they will be exploring a large online database of information about microfossils preserved in deep-sea sediments that were cored from the seafloor by two major ship-based drilling programs.
Introduce students to the ships and drilling programs that produced the data in the Neptune component of the CHRONOS website. These drillships are the Glomar Challenger used during the Deep Sea Drilling Project (DSDP, 1968-1983) and the JOIDES Resolution used during the Ocean Drilling Program (ODP, 1985-2003).
Introduce students to the four main types of marine microfossils. All are single-celled protists with mineralized hardparts: siliceous diatoms, calcareous nannofossils such as coccoliths, calcareous planktic foraminifera, and siliceous radiolarians. These organisms are planktonic and lived in or near the photic zone of the upper water column before settling to the seafloor to become part of the deep-sea sedimentary record. The diatoms and coccoliths (calcareous nannofossils) are able to photosynthesize. These protists are important primary producers at the base of oceanic food chains, being important food for many marine organisms ranging from flea-sized copepods to baleen whales.
Then show students how to access these online references at the CHRONOS web site for information about the microfossils. Directions for accessing this information are part of the activity described in part 2 below.
Part 2 of a Learning Cycle Format. Activities that help students develop explanations for the divisions of geologic time.
Show students how to create a series of bar graphs that show the occurrences of specific microfossil taxa during a selected 10 million year interval from the range of 70 to 30 million years ago (latest Cretaceous to Paleogene periods). A set of notes related to interpreting these bar graphs is available: evolution (Acrobat (PDF) 1.5MB Jun15 06)
Step-by-step instructions for retrieving data and creating graphs automatically with the built-in graphing wizard are available in these two instruction sheets: Directions Accessing Micro Fossil Data in Word (Microsoft Word 2.7MB Jul21 07) and Directions Accessing Micro Fossil Data in PDF (Acrobat (PDF) 66kB Jul21 07)
Then members from different groups should share their findings. Discuss the differences between the sharpness of the Cretaceous-Paleogene boundary and the Paleocene-Eocene and Eocene-Oligocene boundaries. Discuss other issues related to interpretation.
Final activity of this phase of the lesson. Students choose several taxa on either side of the Cretaceous-Paleogene boundary. They should retrieve photographs of the organisms from the "Mesozoic Planktonic Foraminifera Taxonomic Dictionary" and the "Atlas of Paleocene Planktonic Foraminifera". These online taxonomic dictionaries/atlases can be found on the Resources tab on the CHRONOS Portal. Use one of these step-by-step instruction sheets for retrieving information and images: Directions for using the Foraminifera atlas and dictionary in Word (Microsoft Word 2MB Jul21 07)Directions for using the Foraminifera atlas and dictionary in PDF (Acrobat (PDF) 98kB Jul21 07).
Have students choose several taxa that became extinct at the end of the Cretaceous (from the "Mesozoic Planktonic Foraminifera Taxonomic Dictionary") and several that originated at or near the boundary (from the "Atlas of Paleocene Planktonic Foraminifera") and retrieve their photographs. Determine if there are any similarities in morphology between the group of extinct organisms as compared to similarities among the modern taxa.
Part 3 of a Learning Cycle Format. Students practice the newly-learned information in a new context.
Students finally compare their findings about microfossils with a geologic timeline from 70 to 30 million years ago (70-30 Ma). This timeline shows a variety of sources of data including transgression-regressions (rise and fall of sea level), temperature changes from oxygen isotopes (warming to the right, cooling to the left), and disruptions in the carbon cycle from carbon isotopes. They discuss how geologists use multiple sources of data and information to determine the causes of change. Have students compare their results and determine if particular intervals display elevated rates of evolutionary activity (originations and extinctions of species, i.e., first occurrences and last occurrences). Compile a list of times with elevated rates of species originations and extinctions. Do these times correspond with other evidence of global change? Have students work in small groups. Finish by having a discussion with the entire class.
Students can also complete an additional assignment in which they investigate an aspect of the foraminifera. This activity will allow students to: explain the characteristics and lifestyles of foraminifera, their use in science and industry, and the methods of the scientists who study them; conduct Internet searches, retrieve images and information, reference them correctly, and format work using a table; and produce an illustrated page of information and present it to inform classmates. Step-by-step instructions for this assignment are available here: Exploring the Formainifera Assignment, directions, and rubric in Word (Microsoft Word 5.1MB Jul21 07) Exploring the foraminifera Assignment, directions, and rubric in PDF (Acrobat (PDF) 332kB Jul21 07).