What is the ecological association called where one species is harmed and the other is unaffected?

The ecological association where one species is harmed while the other is unaffected is known as amensalism. In this interaction, one organism suffers negative effects, often due to factors such as competition for resources or the physical presence of another species, while the other organism does not experience any benefit or harm from the interaction. An example of amensalism can be seen when a large tree shades smaller plants, preventing them from receiving adequate sunlight; the larger tree is unaffected by the presence of the smaller plants, but they are negatively impacted by the lack of light.

In contrast, mutualism involves both species benefiting from their interaction, while commensalism involves one species benefiting while the other remains unaffected. Parasitism is characterized by one organism benefiting at the expense of another, leading to harm or disease for the host. Each of these associations reflects different dynamics in ecological relationships, highlighting the complexities of interactions in natural ecosystems.