Earth provides a rich environment, and many factors continually shape the planet's condition.
Mammals rise to dominance 65 million years ago; primates begin to evolve 55 million years ago.
Cataclysmic events destroy most life 250 million years ago, allowing the dinosaurs to rise to supremacy.
To survive on land, ocean creatures had to adapt to breathing air; predators; changes due to tectonic shifts.
Scientists hypothesize that changes caused by the Ice Ages allowed microbial life to evolve and become more complex.
Scientists hypothesize that all life came from microbes that established themselves four billion years ago and survived as the earth was bombarded with asteroids.
Civilizations have flourished and faded due to natural and/or man-made global changes.
Metals recovered by humans after a complex natural process deposits them in the Earth impact history.
Theories, including a massive meteorite striking the Earth, try to explain the abrupt end of the dinosaur age 65 million years ago.
Glaciers; formation of the Sahara; visuals illustrate the Laurentide ice sheet, continental drift, global air circulation.
During Earth's early evolution, sea vegetation facilitates plant growth on dry land.
The heat of the Earth's core moves continents and creates new continents.
The formation of Earth's atmosphere is linked to how life began on the planet.
Computer animation shows how the universe was formed billions of years ago.
People try to rectify damage caused by deforestation, depletion of fossil fuels and pollution of ocean and atmosphere.
Dramatic climate changes affect the planet; scientists study a potential ice age.
Land becomes fertile as an ozone layer forms; deforestation drastically alters the global climate.
Ancient sea organisms help create an atmospheric balance favorable for the development of life on land.
The release of heat from Earth's interior splits continents, creates landforms and deposits mineral lodes.
Scientists study events leading to Earth's formation and the emergence of qualities conducive to life. Host: Bill Kurtis.