Mount St. Helen
Episode: 21x01 | Airdate: Oct 8, 1980
Episodes
Cystic Fibrosis / Whooping Crane / Cold-Water Survival
Episode: 21x02 | Airdate: Oct 15, 1980
The Bare Necessity / Manatees / Ludhiana
Episode: 21x03 | Airdate: Oct 22, 1980
Tar Wars
Episode: 21x04 | Airdate: Oct 29, 1980
Alternate Car Fuel / Surface Tension / Science Fair
Episode: 21x05 | Airdate: Nov 5, 1980
Chinese Culture (1)
Episode: 21x06 | Airdate: Nov 12, 1980
Modern China (2)
Episode: 21x07 | Airdate: Nov 19, 1980
Survival Instincts of the Insect World / Sickle Cell Anemia
Episode: 21x08 | Airdate: Nov 26, 1980
Invisible Astronomy
Episode: 21x09 | Airdate: Dec 3, 1980
Prenatal Diagnosis of Spina Bifida / Amniocentesis
Episode: 21x10 | Airdate: Dec 10, 1980
One of the Family
Episode: 21x11 | Airdate: Jan 7, 1981
Structure of Birds Eggs / Newfound land Oil
Episode: 21x12 | Airdate: Jan 14, 1981
Poisoned Playgrounds / Charlie
Episode: 21x13 | Airdate: Jan 28, 1981
High Altitude Physiology / The Vision of Galileo / Dust Storms
Episode: 21x14 | Airdate: Feb 4, 1981
February 2, 1981
Episode: 21x15 | Airdate: Feb 11, 1981
Sri Lanka
Episode: 21x16 | Airdate: Feb 18, 1981
Tar Sands
Episode: 21x17 | Airdate: Mar 4, 1981
Blackfly
Episode: 21x18 | Airdate: Mar 11, 1981
Foxes Earth
Episode: 21x19 | Airdate: Mar 25, 1981
April 4, 1981
Episode: 21x20 | Airdate: Apr 1, 1981