The graph below depicts the percentages of oxygen and carbon dioxide in Earth’s atmosphere over time.

Identify which line best represents each gas and explain your answer.
(5 points)
Discuss the evolution of the first living cells and how it affected the amount of each of these gases present in the atmosphere.
(5 points)
If the population of cyanobacteria suddenly went extinct today, predict how that might change the values of each of the gases represented on the graph. Explain your answer.
(5 points)
15 Points Total

Graph two depicts the percentages of oxygen and carbon dioxide in Earth’s atmosphere over time.

Part 1: I couldn't identify the line because you didn't add the graph, but the line for the atmospheric oxygen should be rising, and the line for the atmospheric CO2 should have a period of decrease then probably remain stable/stagnant.

Part 2: Cells first emerged about 3.5-3.8 billion years ago. And about 3 billion years ago, photosynthesis evolved in cells as a means to create energy. This increased oxygen levels in the atmosphere while decreasing CO2 levels. Then, cellular respiration emerged due to the increase oxygen levels in the atmosphere. This increased CO2 levels once again and decreased oxygen levels. This may have led to a balance in CO2 and oxygen levels.

Part 3: We would probably see a decrease in oxygen levels and a rise in CO2 levels on the graph because cyanobacteria are prevalent photosynthetic organisms.

Explanation: