This assignment is used in both a non-majors geology class and an earth science class for education majors. The class meets twice a week for two hours each session, with one hour devoted to lecture, one hour devoted to a lab exercise.

Students must be able to relate the range of an organism to geologic time, be able to identify major groups of organisms, and know when originations and mass extinctions occur within the Phanerozoic rock record (e.g., the Cambrian Explosion, the Permian Extinction).

This activity is one of many short (1 to 2 hour lab exercises) that are paired with a complementary lecture. The lab period immediately preceding focuses on taxonomic identification of major classes and orders of organisms.

Construct and interpret range-through chart

Plot and interpret diversity curve based on range-through data

Groups of students will compare the diversity curves of different groups of organisms.

Students will be able to:

• evaluate data in the context of major events and trends throughout the history of life
• construct a diversity curve and generate hypotheses that explain their trajectories
• estimate the approximate age of an assemblage of fossils using a range through chart

Students will be able to navigate the Paleobiology Database to obtain age ranges for organisms.

Students will be able to use Microsoft Excel to generate a diversity curve.

In advance of this assignment, students will hear a lecture discussing the major events throughout the history of life, including but not limited to: the Cambrian Explosion, the Ordovician Radiation, the "Big Five" mass extinctions and they will be shown the Sepkoski Curve. Additionally students will be introduced to major groups of organisms, mostly at the class and order level.

Students will be divided into groups of 4-5 students and each are assigned a major group of marine organisms with an extensive fossil record (e.g., Bivalves, Brachiopods, Arthropods, Cnidarians). Students will compile a list of 30-40 age ranges for genera within that group by conducting searches on the Paleobiology Database.

Using these ranges, students will construct a range-through chart by hand on paper scaled to a geologic time scale, generating a visual representation of the originations, persistence and extinction of these groups.

Upon construction of the range through chart, students will tally up the number of organisms present in each time period (either originating or persisting or going extinct during that time period). Using these counts, students will make a diversity curve in Microsoft Excel that should depict a rough approximation of the paleontological record of the group.

Students will answer a series of questions related to the interpretation of the range through chart and diversity curve, and devise hypotheses that explain the shape of the trajectory of the curve.

After generating the diversity curve in separate groups, the class will reassemble and combine data for the construction of a synoptic diversity curve.


Students will examine this curve and compare it to that of the Sepkoski curve for the purposes of analysis and hypothesis formation.

Students will be evaluated based on the completion of the assignment and the sophistication of submitted answers. The development of hypotheses for explaining the shape of the diversity curves is central to this assignment.