The sycomore fig tree and the fig wasp share a curious and important co-dependency.

(Airs Sunday, August 30) It may be one of nature's oddest couples: a tiny wasp and a giant fig tree. The wasp and the fig depend on each other for survival.

Excerpts from NATURE examine interrelationships between sharks and other species in the marine ecology. Human impact in the ecosystem includes the shark fin industry.

This video-enhanced lesson focuses on symbiosis and ecological relationships. Using sharks and marine species as examples, students will investigate the many ways that species that live in close proximity to each other might interact in an ecosystem, and will then explore the ways that ecosystems can be thrown out of balance, often as a result of human action. (Grades 9-12)