Consumers obtain energy by eating other organisms (plants or animals), while decomposers (bacteria, fungi) break down dead organic matter and absorb nutrients, recycling materials back into the ecosystem.
Source: Our Environment, Chapter 13, Section 13.1.1
For a 1-mark question, examiners expect one clear contrasting point. State what each does: consumers feed on living organisms; decomposers break down dead/decaying matter. Mentioning examples (fungi, bacteria) is a bonus but not compulsory. Avoid writing a paragraph.