The Meaning of Life
In Search of an Answer
Theiss Research/Chamblee Charter High School
This case study takes the form of a dialogue between three students searching for a definition of life. The characters are very loosely based on Galileo’s Dialogue Concerning the Two Chief World Systems. The three students are a physics student (Dave/Salviati), a biology student (Mary/Sagredo), and a chemistry student (John/Simplicio). The case consists of two parts. The first part examines the need for a definition of life, and the two most common approaches: (1) define life by listing the properties of life as we know it (e.g., organization, metabolism, homeostasis, growth, reproduction, response to stimuli, and evolution), and (2) the Joyce definition that NASA uses, i.e., life is a self-sustained chemical system capable of undergoing Darwinian evolution. The second part of the case study discusses the approach of Schrödinger: life is defined by physical principles, specifically those of entropy and free energy. The case was designed for an introductory course on astrobiology, but it can also be used in any course that discusses thermodynamics (specifically, the second law of thermodynamics) or the definition of life (e.g., biology courses).
- Articulate the advantages and disadvantages of using conventional definitions and approaches for the definition of life.
- Compare and contrast the Clausius and the Kelvin versions of the second law of thermodynamics, and their relationship to systems outside of equilibrium, specifically living systems.
- Compare and contrast the definitions of life offered by Joyce (NASA), Schrödinger, and biology textbooks, including their relative advantages and disadvantages.
KeywordsLife; entropy; thermodynamics; extraterrestrial life; astrobiology; Schrödinger;
Educational LevelHigh school, Undergraduate lower division
Type / MethodsDirected, Discussion
Subject HeadingsAstronomy | Biology (General) | Physics | Science (General) |
Case teaching notes are password-protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, begin the process by registering.
Teaching notes are intended to help teachers select and adopt a case. They typically include a summary of the case, teaching objectives, information about the intended audience, details about how the case may be taught, and a list of references and resources.