Gaia hypothesis
The hypothesis that organisms and their physical environment interact through feedbacks that regulate Earth’s conditions and help sustain life.
Earth system science: The study of interactions among Earth’s atmosphere, oceans, land, ice, and living systems. Gaia frames these interacting components as a coupled system with life-influenced feedbacks.
James Lovelock: A British scientist who developed the Gaia hypothesis and helped create the electron capture detector. Lovelock proposed that life could regulate planetary conditions through interacting feedbacks.
Natural selection: The process by which heritable traits affecting reproduction become more or less common across generations. Gaia’s critics asked how planetary-scale regulation could arise through selection among organisms.
Planetary habitability: The capacity of an astronomical body to support conditions suitable for life. Gaia links habitability not only to planetary conditions but also to life’s effects on them.
Biogeochemical cycle: The circulation of chemical elements through organisms and Earth’s physical environments. Element cycles connect biological activity to atmospheric, oceanic, and geological conditions.
Lynn Margulis: An American biologist who advanced the endosymbiotic theory and collaborated with James Lovelock on Gaia. Margulis emphasized how microbial activity could alter and maintain Earth’s environment.
Teleology: The explanation of phenomena by their purposes or ends. Gaia can sound purpose-driven, though its scientific versions rely on feedback rather than foresight.
Astrobiology: The interdisciplinary study of life in the universe, including its origins, evolution, and distribution. Gaia offers a framework for considering how life might alter detectable planetary environments.
Daisyworld: A simple model in which light- and dark-colored daisies alter planetary albedo and temperature. This model demonstrates how ecological feedback can regulate climate without foresight.
Planetary science: The study of planets, moons, and planetary systems, including their physical and chemical processes. Comparisons between Earth and lifeless planets helped motivate Gaia’s focus on life’s planetary effects.