What term describes an undesirable organism that causes harm to humans, desirable plants, and animals?

The term "pest" accurately describes an undesirable organism that can cause harm to humans, desirable plants, and animals. Pests often include insects, rodents, and other organisms that may compete with native species for resources, spread diseases, or directly damage crops and livestock. Understanding the role of pests in the ecosystem is crucial for effective pest management strategies, which aim to minimize their negative impact while protecting beneficial organisms.

In contrast, the other options represent different concepts. A weed typically refers to any unwanted plant that grows in cultivated areas, which may not necessarily harm humans or animals directly, although they can compete with crops for nutrients. Bioaccumulation refers to the accumulation of substances, such as pesticides or heavy metals, in an organism, which is more about environmental and health science than describing harmful organisms. A pathogen specifically pertains to microorganisms that can cause diseases in other organisms, which, while harmful, is a narrower category than pests as it does not encompass all organisms that can cause harm, such as herbivorous insects.