The episodes are produced in documentary format. Instructors may find them applicable to classroom instruction or distance learning. This resource is a question set students can complete while watching the episode. As of the time of publication, episodes stream at the Annenberg Learner website. The link in the episode title below and on the Google Doc file connect to the episode page, which includes a link to the video.
1. Many Planets, One Earth at TPT
Astronomers have discovered dozens of planets orbiting other stars, and space probes have explored many parts of our solar system, but so far scientists have only discovered one place in the universe where conditions are suitable for complex life forms: Earth. The early Earth was a much different planet than the one we know today. Ancient rocks provide evidence of the emergence of oxygen in the atmosphere and of a frozen Snowball Earth. Scientists Paul Hoffman and Andrew Knoll look at these clues to help explain the rise of complex animal life.
The atmosphere is what makes the Earth habitable. Heat-trapping gases allow ecosystems to flourish. While the NOAA Global Monitoring Project documents the fluctuations in greenhouse gases worldwide, MIT's Kerry Emanuel looks at the role of hurricanes in regulating global climate.
This is a story of a surprising aspect of El Niño and of the relatively recent discovery of Prochlorococcus. Oceans cover three-quarters of the Earth's surface, but many parts of the deep oceans have yet to be explored. Learn about the large-scale ocean circulation patterns that help to regulate temperatures and weather patterns on land, and the microscopic marine organisms that form the base of marine food webs. Ocean systems operate on a range of scales, from massive systems such as El Niño that affects weather across the globe to tiny photosynthetic organisms near the ocean surface that take in large amounts of carbon dioxide. This program looks at how ocean systems regulate themselves and thus help maintain the planet's habitability.
Why are there so many living organisms on Earth, and so many different species? How do the characteristics of the nonliving environment, such as soil quality and water salinity, help determine which organisms thrive in particular areas? These questions are central to the study of ecosystems—communities of living organisms in particular places and the chemical and physical factors that influence them. Learn how scientists study ecosystems to predict how they may change over time and respond to human impacts. Scientists from the Smithsonian Center for Tropical Research document the astounding abundance of diversity in tropical rainforests to discover why so many species coexist that are competing for the same resources. In North America, the Yellowstone Wolf Reintroduction project explores why removing just one species dramatically changed the distribution of plants and animals up and down the food web.
5. Human Population Dynamics at TPT
What factors influence human population growth trends most strongly, and how does population growth or decline impact the environment? Does urbanization threaten our quality of life or offer a pathway to better living conditions? What are the social implications of an aging world population? Discover how demographers approach these questions through the study of human population dynamics. The human population of our planet now exceeds 6.5 billion and is rising. Much of this growth is projected for the most environmentally fragile regions of the world. Will studying the history of the world's population growth help predict the Earth's "carrying capacity"?
6. Risk, Exposure, and Health at TPT
We are exposed to numerous chemicals every day from environmental sources such as air and water pollution, pesticides, cleaning products, and food additives. Some of these chemicals are threats to human health, but tracing exposures and determining what levels of risk they pose is a painstaking process. How do harmful substances enter the body, and how do they damage cells? Learn how dangers are assessed, what kind of regulations we use to reduce exposures, and how we manage associated human health risks. We all require food, air, and water to survive—which are contaminated to some extent by man-made pollutants. Two studies, one in a rural western mining town and another in a dense urban population, reveal how these exposures impact health, and what can be done to reduce the risks.
Demographers project that Earth's population will peak during the 21st century at approximately ten billion people. But the amount of new cultivable land that can be brought under production is limited. In many nations, the need to feed a growing population is spurring an intensification of agriculture—finding ways to grow higher yields of food, fuel, and fiber from a given amount of land, water, and labor. This unit describes the physical and environmental factors that limit crop growth and discusses ways of minimizing agriculture's extensive environmental impacts. Will world population outrun food resources? The "Green Revolution" of the 20th century multiplied crop yields, in part through increasing inputs of pesticides and fertilizers. How can farmers reduce their use of agricultural chemicals and still produce enough food?
Earth's water resources, including rivers, lakes, oceans, and underground aquifers, are under stress in many regions. Humans need water for drinking, sanitation, agriculture, and industry; and contaminated water can spread illnesses and disease vectors, so clean water is both an environmental and a public health issue. In this unit, learn how water is distributed around the globe; how it cycles among the oceans, atmosphere, and land; and how human activities are affecting our finite supply of usable water. While essential to the lives of humans and animals, fresh water only accounts for six percent of the world's water supply. Scientists in Florida's Everglades and the water challenged Southwest consider the optimum use of existing sources of fresh water for both humans and ecosystems.
9. Biodiversity Decline at TPT
Living species on Earth may number anywhere from 5 million to 50 million or more. Although we have yet to identify and describe most of these life forms, we know that many are endangered today by development, pollution, over-harvesting, and other threats. Earth has experienced mass extinctions in the past due to natural causes, but the factors reducing biodiversity today increasingly stem from human activities. In this unit we see how scientists measure biodiversity, how it benefits our species, and what trends might cause Earth's next mass extinction. Species are being lost at a rapid rate in rainforests and coral reefs. Yet many species still have not been discovered. Tropical scientists struggle to keep ahead of the bulldozers as they work to understand this complex ecosystem. And an ocean biologist predicts the death of life and the "rise of slime" in the sea. How can we protect the biodiversity of these vulnerable ecosystems?
Global energy use increases by the day. Polluting the atmosphere with ever more carbon dioxide is not a viable solution for our future energy needs. Can new technologies such as carbon sequestration and ethanol production help provide the energy we need without pushing the concentrations of CO2 to dangerous levels? Industrialized nations rely on vast quantities of readily available energy to power their economies and produce goods and services. As populations increase in developing countries and citizens demand better standards of living, global energy consumption will continue to rise, along with demands for non-fuel mineral resources such as iron and steel. Learn about new technologies that can produce ample supplies of energy without some of the environmental costs linked to current energy resources.
11. Atmospheric Pollution at TPT
Many forms of atmospheric pollution affect human health and the environment at levels from local to global. These contaminants are emitted from diverse sources, and some of them react together to form new compounds in the air. Industrialized nations have made important progress toward controlling some pollutants in recent decades, but air quality is much worse in many developing countries, and global circulation patterns can transport some types of pollution rapidly around the world. In this unit, discover the basic chemistry of atmospheric pollution and learn which human activities have the greatest impacts on air quality. Once released, air pollutants react chemically with each other under solar radiation to become even more dangerous secondary pollutants. A company in the Northeast U.S. tracks the emission of pollutants at street level, while an international long-term study follows plumes of pollution from Mexico City across the continent and beyond
12. Earth’s Changing Climate at TPT
Earth's climate is a sensitive system that is subject to dramatic shifts over varying time scales. Today human activities are altering the climate system by increasing concentrations of heat-trapping greenhouse gases in the atmosphere, which raises global temperatures. In this unit, examine the science behind global climate change and explore its potential impacts on natural ecosystems and human societies. Tropical glaciers are the world's thermometers; their melting is a signal that human activities are warming the planet. A California project tries to predict whether natural ecosystems will be able to absorb enough additional carbon dioxide from the atmosphere in the next 50 years to mitigate the full impact of human-induced greenhouse gas emissions.
13. Looking Forward: Our Global Experiment at TPT
Emerging technologies offer potential solutions to environmental problems. Over the long-term, human ingenuity may ensure the survival not only of our own species but of the complex ecosystems that enhance the quality of human life. In this unit, examine the wide range of efforts now underway to mitigate the worst effects of man-made environmental change, looking toward those that will have a positive impact on the future of our habitable planet. Earth's essential systems are being stressed in many ways. There are many tipping points in the environment, beyond which there could be serious consequences. Will human ingenuity, resiliency, and cooperation save us from the worst outcomes of our global experiment?
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