Assess how the Emancipation Proclamation expanded ideas of freedom and liberty, looking at the antislavery debate that led to the proclamation, the influences on Lincoln's decision, and the provisions of the document. In this interactive...

Explore the motivations for the Louisiana Purchase, as well as the terms of the purchase and its consequences. In this interactive lesson from WGBH, students develop a written argument in response to the question "Do you agree that the...

Explore why the Bill of Rights was added to the Constitution and its enduring impact on defining our rights. In this interactive lesson from WGBH, students develop a written argument in response to the question "How does the Bill of...

Learn the pros and cons of genetically modified (GM) crops, and cast your vote on whether they should be grown. From the FRONTLINE/NOVA: Harvest of Fear Web site.

In this interactive activity from NOVA, learn about the molecular structure of steroids. See the intermediate molecules that are part of the pathway for synthesizing cortisone from diosgenin.

Understand the method used to measure wavelength and how light waves are associated with colors based on wavelength.

Students are challenged to position sticks creating a path so apples land into the pond.

Learn about the achievements and national problems of the African nation of Botswana in this video segment from Wide Angle.

This 1954 statement, issued by a group of black educators, strongly endorses the Supreme Court's Brown ruling.

This sampling of newspaper editorials from the mid-1950s reflects the range of public opinion and responses to the Brown decision.

This illustrated essay from the NOVA Web site explains why the atomic structure of a diamond slows down light and produces a sparkle more brilliant than from any other colorless substance.

This illustration from Evolution by Monroe W. Strickberger shows the remarkable similarities between the bones in the forelimbs of various tetrapods, all of whose limbs serve very different functions.

This series of images shows the work of biologist Karl Niklas on the adaptations and evolution of plants. From The Evolutionary Biology of Plants.

Learn how genetic disorders are passed from parents to children as explained in this excerpt from Blazing a Genetic Trail, from the Howard Hughes Medical Institute.

This video segment adapted from NOVA chronicles the discoveries that led to a radical new theory in which living organisms, not just geological processes, play an active role in cave formation. [5:42]

This interactive resource adapted from the National Park Service presents the key concepts of cave and karst systems, including how and where they form, different types, and various cave environments.

In this interactive resource adapted from the National Park Service, learn about beaches, spits, and other sandy landforms that characterize some of America's coastal national parks.

This interactive resource adapted from the National Park Service profiles rocky coast environments and describes how various geologic features form.

This media-rich essay from NOVA Online describes the challenges of forecasting volcanic eruptions and includes information about specific cases.

Many of the interesting landmarks around the world are formed over time by natural processes familiar to us in our everyday lives. This still collage produced for Teachers' Domain features images of a variety of beautiful natural wonders.

This interactive activity adapted from A Science Odyssey Web site helps you visualize different types of plate tectonic activity and shows the impact this activity has on Earth's surface.

This interactive resource adapted from the National Park Service illustrates the difference between explosive and effusive volcanic eruptions, as well as the hazards that can result, including lahars, tsunamis, and lava flows.

This interactive resource adapted from the National Park Service illustrates the variety of landforms and features created by volcanoes. Featured are calderas, craters, fumaroles and other geothermal features, igneous rocks, lava flows,...

This illustrated timeline from the Lunar and Planetary Institute provides a journey through four-and-a-half billion years of time from the birth of our solar system to its current existence today.