1900 Air Pollution

Examine this graph from FRONTLINE/NOVA: "What's Up with the Weather?" Web site to see dramatic increases in three greenhouse gases over the last two hundred years.

Advances in Neurotechnology

In this video segment from Greater Boston, learn how a man with severe motor disabilities can operate a computer and move a prosthetic hand by simply thinking the commands, thanks to the combined efforts of bioengineers and neuroscientists.

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The Advantage of Sex

Why did sex evolve? The likely answers, in this essay for the Evolution Web site by science journalist Matt Ridley, may surprise you.

Agarose Gel Demos

Watch a "how-to" video on the proper technique of preparing an agarose gel for use in gel electrophoresis in this video segment from Austin Community College. A supplementary video shows the proper technique for pouring an agarose gel.

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Agricultural Runoff and the Gulf of Mexico Dead Zone

This video segment adapted from Big River: A King Corn Companion shows how agricultural chemicals from the Midwest that travel downstream in water runoff create a vast marine "dead zone" in the Gulf of Mexico.

All in the Family

In this Evolution Web feature, test your skills at judging who's who on the tree of life while you learn about the tools and methods of cladistics.

Allopatric Speciation

These images from the Smithsonian Institution depict Nancy Knowlton's work with snapping shrimp in Panama. Knowlton found that the closing of the isthmus -- dividing the Pacific Ocean from the Caribbean -- resulted in new species of shrimp.

Alzheimer's Disease

This video segment from the Secret of Life School Video: "Genetic Medicine: Tinkering with Our Genes" explores the potential for gene therapy to cure diseases like Alzheimer's.

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Ancient Farmers of the Amazon

This video segment from Evolution: "Evolutionary Arms Race" tells the story of the leafcutter ant and the fungus it farms -- an example of mutually beneficial symbiosis.

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Animal Body Plans: Homeobox Genes

The homeobox genes that define the basic body plan of mice and fruit flies are illustrated in this graphic from The Human Evolution Coloring Book by Adrienne Zihlman. The accompanying article describes how these genes act as "molecular architects" in all animal species.

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Arctic Tundra

This video segment from Wild Europe: "Wild Arctic" explores the struggle for survival in one of Earth's most extreme environments.

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Atrazine Affects the Water Supply

In this video segment featuring live-action animation, adapted from Big River: A King Corn Companion, see how the agricultural pesticide atrazine impacts both crops and human health.

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Bioengineering Body Parts

In this video segment adapted from NOVA scienceNOW, scientists discuss their attempts to grow human body parts in a jar.

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Biological Invaders

This video segment from Evolution: "Extinction!" shows the impact of invasive species on native ecosystems.

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Biomes

This interactive resource adapted from NASA describes the different temperature, precipitation, and vegetation patterns in seven biomes: coniferous forest, temperate deciduous forest, desert, grassland, rainforest, shrubland, and tundra.

Blood Flow and Thermoregulation

In this interactive activity adapted from the University of Alberta, learn about the ways your body can regulate its temperature.

Blood Vessels Help Tumors Grow

In this video segment, adapted from NOVA, Dr. Judah Folkman uses the scientific method to discover how cancer cells induce the formation of new blood vessels, which in turn nourish those cancer cells.

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Bt Corn

This video segment from FRONTLINE/NOVA: "Harvest of Fear" looks at corn that has been genetically modified to resist one insect pest, and the multiple concerns it raises.

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Build a Family Tree

Both sexes can use this interactive feature that lets you use DNA information from the Y chromosome to complete a male family tree. From the NOVA: "Lost Tribes of Israel" Web site.

Build-a-Fish

In this interactive activity from Shedd Aquarium, build a fish and then release it into the reef to search for food and evade predators. Try different combinations and observe how each kind of fish has unique adaptations that help it survive in its habitat.