What is a defining characteristic of microorganisms?

Microorganisms are defined by a diverse array of characteristics, and one of their most defining features is that some are beneficial while others are harmful. This dual nature means that microorganisms play various roles in different ecosystems and contexts. For example, certain bacteria are essential for processes like digestion in the human gut, while others can cause diseases.

The fact that some microorganisms are beneficial makes them essential to various industries, including healthcare, agriculture, and food production. This characteristic underlines the importance of understanding microorganisms beyond just their pathogenic potential, emphasizing their contributions to health, nutrition, and environmental processes.

The other options do not accurately reflect the nature of microorganisms. For instance, not all microorganisms are harmful; many support critical biological processes. Additionally, microorganisms are typically much smaller, not larger, than macroscopic organisms. Finally, microorganisms can reproduce, often very rapidly, which is a crucial aspect of their survival and propagation.