UC Riverside

The rise of oxygen in Earth's atmosphere from negligible levels on the earliest Earth to the high levels that we enjoy today is the consequence of oxygenic photosynthesis and it is the most profound impact that life has had on Earth's surface environment. Yet details of this transition remain poorly constrained. This dissertation examines the cause-and-effect relationships between Earth's biosphere, atmosphere, and climate system with a particular focus on oxygen and its many impacts. Topics include: (1) the relationship between oxygen production and oxygen accumulation on early Earth, (2) the mechanisms that regulate oxygen levels in Earth's atmosphere, (3) the role of oxygen in early animal ecosystems, and (4) the interplay between oxygen and trace greenhouse gases. Understanding the relationships between life and its environment is essential to understanding not only the requirements and emergence of complex life on Earth but on other planets as well---and for ultimately recognizing the chemical fingerprints of life in the atmospheres of other inhabited worlds.