Which subgroup includes organisms like blue-green algae?

The subgroup that includes organisms like blue-green algae is classified under prokaryotes, specifically cyanobacteria, which are sometimes referred to as blue-green algae. Blue-green algae are significant because they are capable of photosynthesis, similar to plants, and play a crucial role in aquatic ecosystems by producing oxygen and serving as a base food source.

Prokaryotes are characterized by the absence of a membrane-bound nucleus and other organelles, distinguishing them from eukaryotic organisms. While archaea is a subgroup of prokaryotes, blue-green algae fall specifically under the category of cyanobacteria, which is often grouped with bacteria. Therefore, the better classification for blue-green algae is indeed prokaryotes rather than archaebacteria or any of the other choices listed, as fungi and protozoans are eukaryotic organisms that do not include blue-green algae.