In autumn, many bald eagles from northern areas find their way to the Upper Mississippi River Valley, where stretches of the river do not freeze.

Select an animal name to see where each animal can be found within the park.

(Airs Sunday, July 18) The Andes is an extraordinary world of diverse terrain, extreme temperatures and multifarious wildlife.

The sycomore fig tree is the center of an entire ecosystem, producing several tons of fruit a year and feeding a greater variety of animals than any other kind of tree in Africa.

Located along the riverbanks of southern Kenya, the sycomore fig tree feeds more varieties of animals than any other kind of tree in Africa.

Watch the full episode of "Under Antarctic Ice" online now.

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)

Brazil nut trees are among the giants of South America's Amazon. They tower up to 200 feet high, and they provide habitat and food for numerous forest creatures.