The prokaryotic cells that built stromatolites are classified as _____.

• A. protozoa
• B. archaea
• C. fungi
• D. cyanobacteria

Answer: (D)

Verified step by step guidance

1. Understand the context of the question: Stromatolites are layered structures formed by the activity of microorganisms, primarily through the trapping, binding, and cementation of sedimentary grains. These structures are often associated with ancient prokaryotic life.
2. Recall that prokaryotic cells lack a nucleus and membrane-bound organelles. This distinguishes them from eukaryotic cells, which include organisms like fungi and protozoa.
3. Review the classification of the options provided: Protozoa and fungi are eukaryotic organisms, so they cannot be the correct answer. Archaea are prokaryotic but are not known for forming stromatolites.
4. Learn about cyanobacteria: Cyanobacteria are photosynthetic prokaryotes that played a significant role in Earth's early history. They are responsible for oxygenating the atmosphere and are known to form stromatolites through their metabolic activities.
5. Conclude that cyanobacteria are the correct classification for the prokaryotic cells that built stromatolites, based on their ability to photosynthesize and their role in forming these structures.