Bottom-dwelling organisms living in sediments are collectively called

• A. Benthos
• B. Periphyton
• C. Carrion
• D. Decomposers

Answer: (A)

Bottom-dwelling organisms living in sediments are called benthos. This term names the community that lives on, in, or right at the bottom of aquatic environments—the sediment layer and the interface just above it. Benthos includes a range of organisms, from burrowers that move through or within the sediment to those that live on the surface of the bottom.

Periphyton, by contrast, are groups of algae, microbes, and detritus attached to submerged surfaces like rocks or aquatic plants, not specifically those living embedded in sediment. Carrion refers to dead animal matter, which is not a group of bottom-dwelling organisms. Decomposers describe organisms that break down dead organic material; many are bacteria and fungi, and while some operate in sediments, the term describes a function rather than the habitat or group name for bottom-dwellers.