Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
Search NOVA Teachers

Back to Teachers Home

Origins: How Life Began

Program Overview

PDF

Origins: Earth is Born Program Overview
Origins: Where are the Aliens? Program Overview
Origins: Back to the Beginning Program Overview


Man observing coral NOVA reports on the different ways scientists explain how life emerged on Earth.

The program:

  • relates the discovery of extremophiles—bacteria that thrive in harsh subterranean and deep ocean environments similar to those believed to have existed on primitive Earth.

  • describes an attempt to determine when life began on Earth by searching rock formations in Greenland for higher-than-expected ratios of carbon 12 to carbon 13 (in ratios currently only known to be created by life processes).

  • points to the comets and meteorites that struck Earth during its early history as possible sources for the carbon and other ingredients necessary for life to form.

  • reveals the discovery of amino acids (organic acids that form the proteins that are essential to life) in meteorites.

  • describes an experiment that simulated a comet's massive impact with Earth to determine whether certain amino acids could have withstood such a collision.

  • indicates experimental results that show that the amino acids not only could have survived but also may have fused into peptides (compounds formed by linking two or more amino acids).

  • speculates that life may have begun deep in Earth's crust or oceans, where it would have been protected from harsh solar radiation, the high temperatures of Earth's surface, and bombardment by meteorites.

  • uncovers bacteria living deep below Earth's surface that obtain energy from methane, ethane, and propane gases and suggests that ancient bacteria might have derived energy in the same way.

  • notes that surface bacteria that emerged following the Great Bombardment likely developed the ability to photosynthesize.

  • looks at stromatolites—both modern ones built from layers of cyanobacteria and sediment and their fossil counterparts that may have formed the same way—and reviews the role the cyanobacteria played in creating an oxygen-rich environment in which complex life could form.

Taping Rights: Can be used up to one year after the program is taped off the air.

Teacher's Guide
Origins: How Life Began
BUY THE VIDEO PROGRAM OVERVIEW VIEWING IDEAS CLASSROOM ACTIVITY RELATED NOVA RESOURCES INTERACTIVE FOR STUDENTS
   

Support provided by