What do autotrophs primarily rely on to create their own chemical energy?

Autotrophs are organisms that are capable of producing their own chemical energy from inorganic substances. The primary process they use to accomplish this is photosynthesis. In photosynthesis, autotrophs, such as plants, algae, and some bacteria, harness sunlight and convert carbon dioxide and water into glucose and oxygen. The glucose produced serves as a source of chemical energy, which can be utilized by the autotroph for growth, reproduction, and metabolic functions.

In contrast, processes like cellular respiration and fermentation are involved in breaking down organic molecules to release energy but are not mechanisms by which autotrophs generate their chemical energy. Heterotrophy refers to the mode of nutrition where organisms consume organic matter produced by other organisms, which is not applicable to autotrophs. Therefore, photosynthesis is the cornerstone of energy production for autotrophs, underlining the correctness of selecting this process as the means by which they sustain themselves.