What defines heterotrophs in biological terms?

Heterotrophs are defined as organisms that cannot synthesize their own food and rely on consuming other organisms or organic matter for energy and nutrients. This classification includes animals, fungi, and many bacteria that obtain their energy by breaking down organic compounds derived from other living beings. They play a critical role in ecosystems as consumers that facilitate energy transfer by feeding on plants (primary producers) or other animals.

Other options describe different biological classifications. For instance, the first choice refers to autotrophs, which can produce their own food typically through processes like photosynthesis or chemosynthesis. The third choice, relating to photosynthesis, specifically characterizes organisms like plants and some microorganisms that can convert sunlight into chemical energy. The last option describes mixotrophs, which can utilize both autotrophic and heterotrophic means for energy, but does not define heterotrophs exclusively. Thus, the essence of heterotrophs lies in their reliance on consuming existing organic sources rather than producing their own.