Beginning with examples from the polar regions, this article examines the question ������Why do we have seasons?������ Included are links to lesson plans, a list of children������s books, and suggested alignments with science, literacy, geography, and climate instruction in K-5 classrooms. The article appears in the free, online magazine Beyond Penguins and Polar Bears.

This video segment from FRONTLINE/NOVA: "Harvest of Fear" explores genetic modification of salmon and possible consequences.

This video segment adapted from NOVA reveals how junk DNA helped solve an evolutionary mystery: Why do certain species of fruit flies have wing spots while others don't?

This regular column, called Take Action, in the magazine Beyond Weather and the Water Cycle suggests actions K-5 teachers can take to incorporate the guiding principle for informed climate decisions in the classroom. The principle, which appears in the document Climate Literacy, states that humans can take actions to reduce climate change and its impacts.

The Take Action column in the free, online magazine Beyond Weather and the Water Cycle suggests actions young people (K-grade 5) can take to reduce the impacts of climate change. The magazine examines the recognized essential principles of climate literacy and the climate sciences as well as the guiding principle for informed climate decisions.

The Take Action column provides resources that help teachers engage students in activities that connect their science learning to their lives. In this article, students are introduced to household appliances and devices, called energy vampires, that continue to draw electrical current even when turned off. The article offers a few simple activities that students can take to reduce the impact of energy vampires. The Take Action column regularly appears in the free, online magazine Beyond Weather and the Water Cycle, which focuses on the essential principles of climate literacy.

The peacock provides a classic example of sexual selection, the force behind nature's extravagances. From Evolution: "Why Sex?"

Bonnie Chen builds on students' prior knowledge of mutations to lead her class through a simulation of wading birds feeding.

Marilyn Havlik leads students through a simulation of the Hardy-Weinberg Principle to develop their understanding of population genetics.

This article introduces ARKive, a digital library of photographs and videos of the world's wildlife. The library gives special priority to at-risk species. The author notes how this interactive resource can be used by K-5 teachers to support other activities connected to the theme of this issue of the free, online magazine Beyond Weather and the Water Cycle -- We Depend on Earth's Climate.

In this video adapted from KUAC-TV and the Geophysical Institute at the University of Alaska, Fairbanks, learn how tectonic plate movement is responsible for building mountains, such as the Wrangell and St. Elias Mountains.

This interactive activity produced for Teachers' Domain shows the relationship between tectonic boundaries and the locations of earthquake events and volcanoes around the world.

In this transcript of an interview filmed for Evolution: "Great Transformations," Ted Daeschler and Neil Shubin describe the discovery and significance of some of their key fossil finds.

Why do teenagers act the way they do? This video segment from FRONTLINE: Inside the Teenage Brain explores the work scientists are doing to explain some of the mysteries of teenage behavior.

Watch the ZOOM cast discover which insulator -- newspaper or aluminum foil -- is better at keeping an ice cube frozen longer.

In this video segment adapted from ZOOM, cast members show you how to make your very own electroscope. You can use it to find out if an object is electrically charged.

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 interactive activity from the NOVA Web site challenges you to think like Einstein and understand how time travel might be possible.

This illustrated essay from the NOVA Web site answers questions about irregularities in the tides.

John Noble Wilford, a New York Times science writer, outlines various hypotheses on the origin of bipedalism.