What does the term 'symbiosis' refer to?

The term 'symbiosis' refers to a close, long-term interaction between two different biological species, which can involve various forms of relationships. The most common form of symbiosis is mutualism, where both organisms benefit from the interaction, although there are other types such as commensalism, where one organism benefits while the other is neither helped nor harmed, and parasitism, where one benefits at the expense of the other.

In a mutualistic relationship, for example, bees and flowers exemplify symbiosis: bees obtain nectar (food) from the flowers, and in return, they help pollinate the flowers, aiding in their reproduction. This mutual benefit is central to the definition of symbiosis and highlights the importance of interdependent relationships in ecosystems.

Other choices refer to different ecological concepts. Competition for resources describes a struggle between organisms for available resources and does not imply mutual benefit. Predation involves one organism feeding on another, clearly detrimental to the prey. Ecological succession refers to the process of change in species composition in an ecosystem over time, which is unrelated to the concept of symbiosis itself. Thus, the focus on mutual benefit in the definition reinforces why this is the correct understanding of symbiosis.