Final answer:
Saprotrophs, such as fungi and bacteria, obtain nutrients from dead organic matter by external digestion, playing a crucial role in decomposition.
Step-by-step explanation:
Saprotrophs, such as fungi and bacteria, obtain their nutrients from dead organic matter by secreting digestive enzymes and digesting it externally. They play a crucial role in decomposition by breaking down dead organisms and organic waste, releasing simple inorganic molecules back into the environment. For example, fungi can decompose tough wood fibers that no other organisms can digest.