Lesson 4: Life's Effect on Earth Atmosphere
Key Learning Objectives:
Explain the relationship between life and atmospheric gas by referring to specific examples of gaseous equilibria, including the continuing effects humans have on the atmosphere.
Understand how Earth’s biosignature has changed over time.
In this lesson you'll find...
Atmospheric Equilibrium and Consequences for Life
Earth's Atmosphere over Time
Atmospheric Equilibrium and Consequences for Life
Atmospheric equilibrium, or the balance of gases in Earth's atmosphere, plays a crucial role in sustaining life on our planet. This balance is essential for maintaining stable temperatures and the right mix of gases for living organisms. For instance, oxygen is abundant due to the equilibrium between processes like photosynthesis and respiration. Additionally, the greenhouse effect, which relies on the equilibrium of gases like CO2 and water vapour, helps trap enough heat to keep Earth warm. However, disturbances to this equilibrium, such as increased greenhouse gas emissions from human activities, can lead to consequences like global warming and climate change. Understanding and preserving atmospheric equilibrium are crucial for ensuring a habitable environment for diverse forms of life on Earth.
The infographic below shows that Earth’s atmosphere is 78% N2 and 21% O2. The rest of the atmosphere is made of a mix of other gases, including CO2 which is a greenhouse gas that humans have a direct impact on as well as Ozone (O3) which acts as a radiation shield that is crucial for life to exist on Earth. The equilibrium of these compounds greatly influences how life functions on Earth and the specific equilibrium we have is unique to our planet.
Class Discussion
Recall from one of the last lessons that there are different types of exoplanets; Neptune-like, Terrestrial, Super-Earth, and Hot Jupiters. Would the atmosphere on these planets be the same? If not, what would make them different? Why are all atmospheres not the same?
Earth's Atmosphere over Time
The Earth’s atmosphere has not always been the composition that it is now. Over time, different gases have dominated and equilibrated until we ended up with the mixture we have today. We continue to change the atmosphere just by being alive as well as by our CO2 emissions!
This infographic provides a historical perspective on how Earth and its atmosphere were conceptualised in 1848.
Primarily focusing on elucidating the physics governing Earth's atmosphere, it delves into the atmosphere's density variations as one ascends into the sky, highlighting the inhospitable conditions prevailing in the upper layers.
The graphic also explores additional atmospheric properties such as its refractive capabilities, impacting our perception of where things are situated in the sky.
However, this infographic is missing one very important factor: the chemistry of the atmosphere and its relationship with life on Earth.
Evidently, scientists can be more specific about the composition of our atmosphere in the modern day and can also model how it would have changed over time. Below is a comparison between Earth’s prebiotic atmosphere and our modern day atmosphere.
Class Discussion
What are the major differences and why do you think the atmosphere has changed?
Presently, the big discussion revolved around how humans make an impact on CO2. The following clip is a visual aid to show how the concentration of this greenhouse gas changes in the span of a year.
Access the below website and navigate. Learn about what each gas does in the atmosphere and adjust the mixture of each gas to show how the planet and life would be altered:
https://forces.si.edu/atmosphere/interactive/html/index.htm
Our Earth has a very delicate balance of gases in the atmosphere which have allowed life to thrive. Give an example of how a change in the concentration of a given molecule would affect life.
