Place in chronological order the following steps in the formation and evolution of Earth's atmosphere. a. Plant life converts carbon dioxide \(\left(\mathrm{CO}_{2}\right)\) to oxygen. b. Hydrogen and helium are lost from the atmosphere. c. Volcanoes, comets, and asteroids increase the inventory of volatile matter d. Hydrogen and helium are captured from the protoplanetary disk. e. Oxygen enables the growth of new life-forms. f. Life releases \(\mathrm{CO}_{2}\) from the subsurface into the atmosphere.

The early Earth atmosphere was vastly different from what we experience today. During its formation, Earth's atmosphere consisted mostly of hydrogen and helium, captured from the surrounding protoplanetary disk. However, due to Earth's relatively weak gravity at that time, these light elements were unable to remain and were lost into space. Volcanic eruptions, along with impacts from comets and asteroids, played a crucial role in introducing heavier and more stable gases such as nitrogen, water vapor, and carbon dioxide. This mixture laid the groundwork for the atmosphere's further evolution.

In this initial stage, the atmosphere was not yet hospitable to life as we know it. The presence of volcanic activity continuously altered the composition, contributing to the planet's gradual transformation into a more life-friendly environment.

One of the most transformative processes in Earth's atmospheric history was photosynthesis. Early plant life, primarily cyanobacteria, began converting carbon dioxide \(\text{CO}_2\) into oxygen (\(\text{O}_2\)) through photosynthesis. This not only acted as a carbon sink but also significantly enriched the atmosphere with oxygen.

Photosynthesis can be simplified in the following chemical equation:

\(\text{CO}_2 + 2\text{H}_2\text{O} + \text{light energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2\).

The increase in oxygen levels enabled the development and diversification of more complex and aerobic life forms. This pivotal change marked the Great Oxidation Event, filling the atmosphere with oxygen and allowing new ecosystems to thrive.

Volcanic activity has always influenced Earth's atmosphere. During Earth's early years, massive volcanic eruptions released substantial amounts of volatile gases into the atmosphere. This includes water vapor, carbon dioxide, sulfur dioxide, and other gases.

The volatile matter emitted from volcanoes contributed to the greenhouse effect, which helped retain heat and regulate the planet’s temperature. Moreover, water vapor from volcanic eruptions eventually condensed to form the early oceans. Over time, these contributions provided a more stable atmosphere, fostering the essential conditions for life to evolve.

The interaction between volcanic activity and atmospheric composition continues to influence Earth's climate and life cycles.

One of the significant changes in Earth's atmospheric evolution was the loss of light elements, notably hydrogen and helium. Initially, these were captured from the protoplanetary disk, but Earth's gravity was insufficient to retain them.

This loss occurred because these light elements are so small and fast-moving that they easily escaped into space, especially under the weaker gravitational pull of early Earth.

As these lighter gases dissipated, the stage was set for a different atmospheric composition, one dominated by heavier and more chemically active gases released by volcanic activity and other processes.

Biogeochemical cycles are critical in sustaining life on Earth and regulating the atmosphere. These cycles involve the movement of elements like carbon, nitrogen, and oxygen between the living (biotic) and non-living (abiotic) parts of ecosystems.

Photosynthesis and respiration are crucial parts of the carbon cycle. Photosynthesizing organisms absorb carbon dioxide from the atmosphere and convert it into organic matter, releasing oxygen in the process. Conversely, respiration by plants, animals, and microorganisms breaks down organic matter, returning carbon dioxide to the atmosphere.

The nitrogen cycle also plays an essential role, as microorganisms convert atmospheric nitrogen into forms usable by plants, which then pass through the food web. These cycles ensure the continuous exchange and replenishment of essential elements, maintaining equilibrium within Earth’s systems.