Practice question

Mutualists commonly provide three broad kinds of services: resources, protection, and transport. Resource exchange includes plant carbon traded for fungal phosphorus or fixed nitrogen supplied by microbes. Protection includes ants defending plants and cleaning symbioses that remove parasites. Transport includes pollination and seed dispersal. “Energy conversion” is not usually listed as a separate service category in this simplified functional scheme, so it is the intended exclusion; biochemical conversion is normally treated under resource provision. The wording is scientifically problematic, however, because many mutualists genuinely transform otherwise inaccessible energy or nutrients. Gut microbes ferment cellulose into short-chain fatty acids usable by animal hosts, and photosynthetic symbionts transfer fixed carbon to corals. Thus, energy conversion can be a mechanism by which a resource service is delivered. The key is defensible only as a taxonomy-of-services item, not as a literal claim that mutualisms never provide metabolic conversion. Accepted ecology groups such transformations within resource mutualism rather than recognizing “energy conversion” as an independent standard class. KEY MISMATCH: the absolute wording makes the keyed exclusion biologically false.