Sample Teaching Module in
Exobiology
.
Snipped from the on-line course
Exobiology for High School Students
by Steve Brown, Science Teacher at La Jolia High School
http://ljhs.sdcs.k12.ca.us/faculty/SBrown/exobiology/contents.html
.
One Thread of BioPoint, an on-line Full-year Secondary Biology Course
(which in turn is a thread of the Science Learning Network)
[Science Learning Network:  http://www.sln.org/]
 

ABSTRACT

Exobiology is a discipline that deals with the origin, occurrence and distribution of life in the Universe. Although this subject is of widespread interest to high school science students, it is not generally dealt with comprehensively in most textbooks. In addition, teachers often have inadequate resources available to prepare classroom presentations on how life may have begun on Earth and whether these processes might take place elsewhere in the solar system and the Universe.

This module provides introductory teaching lessons for classroom coverage of Exobiology and the origin of life that is suitable for use in both general and advanced high school biology courses.
 

INTRODUCTION

Any discussion of the origin of life must first consider the definition of life. This Exobiology teaching module defines life is an autonomous replicating system that evolves by natural selection. With this definition, the origin of life is synonymous with the origin of evolution. The transition from the abiotic chemistry of the primitive Earth to the first self-replicating molecular systems capable of undergoing Darwinian evolution marked the point of the origin of life. On Earth, subsequent evolution of these self-replicating molecules then gave rise to the RNA world and ultimately the DNA/protein world that is characteristic of all modern life.

Although all the processes involved in the origin of terrestrial biochemistry are not fully understood, an essential requirement is the presence of a prebiotic soup consisting of a rich variety of organic compounds. The components of the soup may have been made directly on Earth, or supplied from space by comets, asteroids, micrometeorites or interplanetary dust particles. A large variety of organic compounds, including those which play a major role in biochemistry such as amino acids, purines, pyrimidines, etc., have been identified in one class of meteorites, the carbonaceous chondrites. Besides demonstrating that important biomolecules can be produced abiotically in extraterrestrial environments, their presence also suggests that exogenous compounds could be periodically delivered to the surface of the Earth, and other planetary bodies as well. On the surface of the modern Earth, the amount of exogenous organic compounds is minute compared to the organic compounds produced by biological processes.

Some of the steps leading to the origin of life may have also taken place on Mars. Traces of abiotic organic compounds, or biochemical evidence associated with extinct Martian biota, could be present on Mars. Organic analyses of the surface of Mars planned during the next couple of centuries will be of pivotal importance in understanding the processes involved in the origin of life on Earth and elsewhere.

The module presented here is designed to introduce students to the variety of concepts, problems and unknowns involved in the processes that yielded the first living organisms on Earth. In addition, the module challenges students to think about life in the broad context of what conditions and requirements are needed for life to originate elsewhere in the Universe. (J. Bada)


THE TEACHING MODULE

Exobiology, a discipline concerned with the origin of life, has become not only a significant component of several scientific fields, but it is also a subject of considerable popular interest. It is thus appropriate that an introduction and overview of Exobiology be included in the high school science curriculum.

 

COURSE STRATEGY

The Exobiology teaching module is designed around instructional techniques such as lectures, discussions, demonstrations, student activities and readings. Student participation in laboratory procedures is not required, but could be implemented. Lectures are supplemented with visual aides (overhead transparencies, 35mm projection slides, student handouts and narrated video tapes with accompanying study guides).

 

GENERAL GOALS AND OBJECTIVES

1) Disseminate information on Exobiology to secondary level science students.

2) Enrich and challenge advanced high school students.

3) Provide teachers of advanced high school science with up-to-date curriculum in Exobiology.

4) Enhance general community awareness and appreciation of research in Exobiology.

5) Integrate Exobiology into state and federal science curriculum guidelines.
 
 

COURSE TIME SCHEDULE AND TOPICS

Time Schedule:
 
  • Ten, 50 minute class sessions.
  • Pre-course essay to establish what Exobiology means to the uninformed student.
  • Daily homework and reading assignments.
  • Final post-course essay on the concepts of Exobiology.

    •  
    General Topics of Study:
     
  • Stars and our Solar system (cosmochemistry).
  • Exobiology as a scientific research field (central concepts).
  • The pre-Life Earth (geochemistry, prebiotic chemistry).
  • From molecules to "Life" (molecular biology).
  • The RNA world and evolution (self-replication).
  • Life beyond the Earth (What is "Life"?).

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    EXAMPLE CLASS SESSIONS
     
    Understanding our Solar system and why the Earth is unique.
     
  • Lecture, with audio and visual aides, on the formation of stars and how our Solar system may have originated.

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  • Wall-mount posters of prebiotic themes are reviewed by students for specific content. (Refer to"Posters Review" to follow)

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  • Student role-play simulation and video taping of the Solar system structure and chemistry. Groups of students act as the various planets, asteroids, etc..., which make up the Solar system. Elemental composition will be studied by groups of students. The names of the various bodies are displayed by placards. The uniqueness of the Earth is demonstrated by its living components.

    •  
  • Set-up and demonstration of a Miller-Urey spark discharge experiment. Groups of students work under teacher direction. Discussion of the model's components and analogies to primitive Earth conditions are reviewed with worksheets and handout diagrams.

    •  
  • Prebiotic molecular models are constructed by students in groups.

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  • Student oral presentations are shared with the class, and video taped for discussion.

    •  
  • Homework in preparation for the next session's theme is assigned from selected texts and scientific publications.

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    For more information on exobiology, click here.

    Click here for Steve Brown's complete course materials, including a complete set of Internet links.

     

    [By the way, we're more likely to find: microbes? intelligent forms quite unlike ourselves? organisms that use silicon like we use oxygen? Who knows?]

     


    At the time of writing (January 2001), 50 planets have been discovered outside of our solar system...