Students often struggle with comprehending time scales longer than those dealt with on a regular basis. In this lesson, students analyze time on a millennial scale as they observe organismal responses to climate variability through the last 30,000 years. The inquiry-based lesson, designed for high school students, brings paleoecological techniques into the classroom as students investigate the impact of past changes in temperature and precipitation on vegetational taxa. Students are presented with the task of analyzing and interpreting a 30,000 year sediment record obtained from a lake in Florida (accessed from the North American Pollen Database). Each student pair is given a unique lake sediment sample, which is a microscope photograph reproduced on an 8.5 by 11 inch sheet of paper. The sample represents a snapshot from the chronological sequence of the sediment core. Using vegetation taxa information cards, students identify fossil pollen in their sample and infer conditions of temperature and precipitation from the taxa present. After comparing their results with a reconstruction of temperature and precipitation from a nearby lake, students are challenged to predict where their sample fits into the chronology of the new record. Students are then given radiocarbon dates to test their predictions. In the end, student groups combine their results to produce a 30,000 year record of climate variability for the given area, observing the natural fluctuations in climate conditions.
The lesson’s content and procedure address several National Science Education Standards. Students use evidence of organismal responses to environmental conditions (Standard C) to investigate the dynamic interaction of earth's hydrosphere, atmosphere, and biosphere (Standard D). Students also explore the nature of science through the development of explanations consistent with observational evidence and the modification of explanations as new evidence becomes available (Standard G). The lesson focuses on important skills, promoting cooperative work among students as well as enhancing the ability of students to analyze graphs critically. This activity mimics techniques used by paleoecologists to investigate past climates, and provides students with a relevant and concrete view of millennial time scales. Furthermore, the concept of climate is often taught as a set of conditions characteristic of a particular region of the globe, without reference to the past variations in those conditions. In becoming climate detectives, students are given the opportunity to explore the variability of the climate in their own home region by bringing paleoecology from the laboratory directly into the classroom.