Cyanobacteria are important to the evolution and advancement of other life on Earth because they:

• A. were the first organisms to perform oxygenic photosynthesis, releasing O\(_2\) into the atmosphere
• B. produce glucose through chemosynthesis instead of photosynthesis
• C. were the first multicellular organisms on Earth
• D. are the only organisms capable of nitrogen fixation

Answer: (A)

Verified step by step guidance

1. Understand the role of cyanobacteria in Earth's history: Cyanobacteria are a group of photosynthetic bacteria that played a crucial role in shaping Earth's atmosphere and supporting the evolution of life.
2. Recall the process of oxygenic photosynthesis: Cyanobacteria were the first organisms to perform oxygenic photosynthesis, a process that uses sunlight, water (H\(_2\)O), and carbon dioxide (CO\(_2\)) to produce glucose (C\(_6\)H\(_{12}\)O\(_6\)) and release oxygen (O\(_2\)) as a byproduct.
3. Connect oxygenic photosynthesis to atmospheric changes: The release of O\(_2\) by cyanobacteria led to the Great Oxygenation Event, which significantly increased oxygen levels in Earth's atmosphere, enabling the evolution of aerobic organisms.
4. Eliminate incorrect options: Cyanobacteria do not produce glucose through chemosynthesis (a process that uses chemical energy instead of sunlight), were not the first multicellular organisms, and are not the only organisms capable of nitrogen fixation (other bacteria can also fix nitrogen).
5. Conclude the correct answer: The correct answer is that cyanobacteria were the first organisms to perform oxygenic photosynthesis, releasing O\(_2\) into the atmosphere, which was pivotal for the evolution of life on Earth.