Today, oxygen, or O2, makes up about 21% of Earth’s atmosphere, but for most of our planet’s long history, O2 levels in the atmosphere and dissolved in the ocean were much less than they are today. In this Click and Learn, you will learn the complex biological and geological factors that have influenced the changes in O2 levels.
- Google Chrome version 9 or greater.
- Mozilla Firefox version 9 or greater.
- Apple Safari version 5 or greater.
- Microsoft Internet Explorer version 8 or greater.
- 2012 Association of Medical Illustrators Salon; Award of Excellence