Question

cyanobacteria are a type of photosynthetic bacteria that first appeared on the earth around 2.75 billion years ago. which of the following best explains the role of cyanobacteria in the evolution of life on earth? cyanobacteria released ozone gas into the atmosphere, making the planet more habitable for other organisms. cyanobacteria were photosynthetic, which increased the concentration of oxygen in the atmosphere. cyanobacteria grew in large colonies, which provided a nutrient - rich food source for early eukaryotic consumers. cyanobacteria broke down molecules in the atmosphere to form the dna found in other organisms.

Explanation:

Cyanobacteria were photosynthetic organisms. Through photosynthesis, they produced oxygen as a by - product, which gradually increased the oxygen concentration in the Earth's atmosphere. This oxygen - rich atmosphere was crucial for the evolution of aerobic life forms. They did not directly release ozone, did not primarily serve as a food source to drive evolution in the way described, and did not form DNA in other organisms by breaking down atmospheric molecules.

Answer:

B. Cyanobacteria were photosynthetic, which increased the concentration of oxygen in the atmosphere.