A close interaction between two organisms, often mutually beneficial.
Explanation
Symbiosis (from the Greek "living together") refers to a close and long-term biological interaction between two different biological organisms. While the term encompasses various interactions including parasitism and commensalism, it is most frequently used to describe relationships where organisms live in close physical association.
Option Analysis
- A predatory relationship where one organism consumes another. is incorrect: This describes predation, an interaction where one organism (the predator) kills and consumes another (the prey).
- A close interaction between two organisms, often mutually beneficial. is correct: This accurately describes symbiosis. In many contexts, it specifically refers to mutualism, where both organisms benefit from the association. Classic examples include Rhizobium bacteria in the root nodules of legumes (nitrogen fixation) and lichens (an association between algae and fungi).
- The process of water vapour release by plants. is incorrect: The release of water vapour from the aerial parts of plants is known as transpiration.
- A saprophytic mode of nutrition involving dead matter. is incorrect: This describes saprophytic nutrition, where organisms (saprotrophs) obtain nutrients by decomposing dead and decaying organic matter.
Key Takeaway: Symbiosis is a broad category of ecological interaction involving close physical association between species. The three main types are Mutualism (both benefit), Commensalism (one benefits, the other is unaffected), and Parasitism (one benefits, the other is harmed).