What is a saprophyte?

A saprophyte is specifically defined as an organism, such as a plant, fungus, or microorganism, that derives its nutrients from dead or decaying organic matter. These organisms play a crucial role in the ecosystem by breaking down complex organic materials, thereby recycling nutrients back into the environment, which is essential for soil health and the continuation of various biological processes.

This option highlights the ecological role of saprophytes as decomposers, which is vital for nutrient cycling. By living on organic remains, they help in decomposition, making nutrients available for other organisms, thus sustaining the ecosystem.

The other choices refer to different concepts. For instance, a microorganism that can cause disease refers to pathogens, which are organisms harmful to their hosts. A symbiotic relationship usually indicates interactions between species where one may benefit at the expense of the other or both may benefit, which is entirely different from the concept of saprophytes. A pathogen that is always harmful indicates a consistent detrimental effect, contrasting sharply with the beneficial role of saprophytes in facilitating decomposition and nutrient recycling. Thus, the focus provided in the correct answer encapsulates the essence of what saprophytes are within the broader context of ecological interactions.