What is the primary type of organism that requires ingestion of food to acquire energy?

Heterotrophs are organisms that obtain their energy by consuming other organisms or organic matter, rather than producing their own food. They are dependent on other organisms for their energy and nutritional needs. This group includes animals, fungi, and many bacteria, which break down organic compounds for energy.

In contrast, autotrophs, such as plants, algae, and some bacteria, can produce their own food through processes like photosynthesis or chemosynthesis, leveraging sunlight or inorganic substances to create energy-rich compounds. Decomposers, a subset of heterotrophs, specifically break down dead organic matter and recycle nutrients back into the ecosystem, but they still require the ingestion of organic material for energy. Producers generally refer to autotrophs as they produce organic compounds that serve as food for heterotrophs.

Thus, the primary characteristic of heterotrophs is their reliance on ingestion of food, making them the correct answer to the question.