Heterotrophs are defined as organisms that:

Heterotrophs are indeed characterized by their reliance on other organisms for energy. This means that instead of synthesizing their own food through processes like photosynthesis (which is the case for producers or autotrophs), heterotrophs obtain their nutrients by consuming other living things, whether they be plants, animals, or decomposing matter.

This distinction is crucial because it reflects the different roles in an ecosystem. Heterotrophs play a vital part in the food web, breaking down organic material and thus recycling nutrients. Their dependence on other organisms highlights their need for an ecosystem that contains both producers and other consumers to sustain them.

In contrast, the options related to harnessing sunlight, producing one's own food, or being exclusive to plants and algae describe characteristics of autotrophs or specific groups within the broader categories of producers in ecosystems.