Which organisms are classified as vectors?

The correct answer pertains to organisms that transmit pathogens and parasites. In the context of vector control and public health, vectors are specifically living organisms that can carry and transmit infectious pathogens or parasites to other living organisms. Common examples include mosquitoes, ticks, and fleas, which can carry diseases such as malaria, Lyme disease, and bubonic plague.

These organisms play a critical role in the life cycle of the pathogens they carry, often facilitating their spread among hosts. Therefore, understanding vectors is essential in vector control efforts as targeting these organisms helps to interrupt the transmission of diseases.

The other choices identify entities that do not function as vectors. Bacteria and viruses are pathogens themselves rather than vectors. Plants and fungi can be important in various ecological roles but do not transmit diseases in the same manner as biological vectors. Water and soil are environmental factors that can harbor pathogens but are not carriers in the biological sense; they do not inherently transmit pathogens to hosts like living vectors do.