No, not all autotrophs use the sun as their primary energy source. While most autotrophs, such as plants and some algae, rely on sunlight to perform photosynthesis, there are exceptions.
Certain autotrophs, known as chemosynthetic organisms, obtain energy by oxidizing inorganic substances, such as hydrogen sulfide or ammonia. These organisms are often found in extreme environments, like deep-sea hydrothermal vents, where sunlight does not penetrate.
In summary, while sunlight is the main energy source for many autotrophs, it is not the only one. Chemosynthetic autotrophs demonstrate that life can harness energy from non-solar processes, highlighting the diversity of methods organisms use to sustain themselves.