Answer:
Prokaryotes are very important ecologically because of their involvement in all of the following except STDs. (option C)
Step-by-step explanation:
Prokaryotes are the single-celled organisms, such as bacteria, and structurally do not have a nucleus that houses its genetic material. Rather, a large DNA molecule housed in an area of cytoplasm called nucleiod region made up the genetic material of a prokaryote cell.
Prokaryotes are asexual, meaning their offspring nearly always bear the same characteristics of the parent cell. They play a critical role in the recycling of nutrients by decomposing dead organisms and allowing their nutrients to be re-used. They are key for many metabolic processes.
Further explanations:
Option A. (photosynthesis)
Prokaryotes are very important in photosynthesis because, Cyanobacteria (blue-green algae, blue-greens) are prokaryotic organisms that contain a photosynthetic apparatus Some prokaryotes can perform photosynthesis. This process occurs in the chloroplast.
Option B. (nitrogen fixation)
The largest quantity of nitrogen readily available in the terrestrial ecosystem is gaseous nitrogen from the air, but this nitrogen is not usable by plants, which are primary producers. Prokaryotes perform biological nitrogen fixation to convert nitrogen gas from the atmosphere into ammonia, which can be used by eukaryotes to form important biomolecules such as amino acids and nucleic acids.
Option C. (STDs)
Sexually transmitted diseases (STDs) are infections passed from one person to another through sexual contact.
Sexually transmitted diseases (STDs) or sexually transmitted infections (STIs) caused by bacteria are generally easier to treat. Viral infections can be managed but not always cured. But some bacteria can also cause diseases. Examples of bacterial diseases include tetanus, syphilis, and food poisoning.
Option D. ( Denitrification)
Denitrification is the dissimilatory reduction of nitrate to nitrogen gas.
Nitrogen-fixing bacteria present in the soil and within the root nodules of some plants convert nitrogen gas in the atmosphere to ammonia. So, denitrifying bacteria converts nitrates back to nitrogen gas.
Option E. (Bioremediation)
Bioremediation is the use of living organisms like microbes and bacteria to remove contaminants, pollutants, and toxins from soil and water. Bioremediation can remove oil, some pesticides, fertilizers, and toxic chemicals, from the environment. Bacteria are introduced to the area of the spill where they break down the hydrocarbons of the oil into carbon dioxide; this is an example of bioremediation.