Question

how life began origins nova neil degrasse tyson hd
which of the following best describes cyanobacterias role in earths atmosphere?
they consumed oxygen and lowered its levels
they produced oxygen via photosynthesis, altering the atmosphere
they lived exclusively in deep-sea vents, isolated from atmosphere
they reduced carbon dioxide to methane

Explanation:

Cyanobacteria are photosynthetic organisms. Through photosynthesis, they take in carbon dioxide and water and produce oxygen as a by - product. This oxygen production had a major impact on Earth's atmosphere.

• Option 1: Cyanobacteria do not consume oxygen in a way that lowers its levels. They are oxygen - producers.
• Option 2: Cyanobacteria perform photosynthesis. The general equation for photosynthesis is \(6CO_2 + 6H_2O

ightarrow C_6H_{12}O_6+6O_2\). They produce oxygen which altered the atmosphere from a reducing (low - oxygen) to an oxidizing (higher - oxygen) atmosphere over time.

• Option 3: Cyanobacteria are not exclusive to deep - sea vents. They can be found in a variety of environments like oceans, lakes, and moist soils.
• Option 4: Cyanobacteria do not reduce carbon dioxide to methane. Methanogens (a type of archaea) are involved in methane production from carbon dioxide in some anaerobic environments.

Answer:

They produced oxygen via photosynthesis, altering the atmosphere.