Question

question 5 of 10
starting billions of years ago, in what way did algae change the atmosphere of earth?
a. carbon dioxide was converted to oxygen.
b. oxygen was converted to ozone.
c. nitrogen was converted to oxygen.
d. methane was converted to oxygen.

Explanation:

Algae, specifically cyanobacteria, performed photosynthesis. In photosynthesis, carbon dioxide (\(CO_2\)) is used as a reactant, and oxygen (\(O_2\)) is produced as a by - product. This process changed the atmosphere by increasing the oxygen content. Option B is incorrect because ozone (\(O_3\)) formation from oxygen is a secondary process (e.g., in the stratosphere due to UV radiation) and not the direct change by algae. Nitrogen (\(N_2\)) is a very stable molecule and is not directly converted to oxygen by algae (option C is wrong). Methane (\(CH_4\)) is not a reactant in the photosynthesis of algae to produce oxygen (option D is wrong).

Answer:

A. Carbon dioxide was converted to oxygen.