A Level Biology Practice Exam

What do heterotrophic organisms primarily rely on for their nutrients?

1. Photosynthesis from light

2. Absorption of inorganic minerals

3. Ingestion of other organisms

4. Synthesis of their own food

The correct answer is: Ingestion of other organisms

Heterotrophic organisms primarily rely on the ingestion of other organisms for their nutrients. This group includes animals, fungi, and many bacteria, which cannot produce their own food like autotrophs do; instead, they must consume organic matter—this can include plants, other animals, or decomposing organic material—to acquire the energy and nutrients necessary for their growth and maintenance. Heterotrophs differ fundamentally from autotrophs that use photosynthesis to convert light energy into chemical energy, or those that absorb inorganic minerals, as they play an essential role in ecosystems by breaking down organic compounds, recycling nutrients, and contributing to food webs. By consuming other organisms, heterotrophs obtain the complex organic molecules needed for cellular processes, such as energy production and biosynthesis, demonstrating their reliance on external sources of nutrients.