Which term describes organisms that obtain energy from chemical reactions rather than from light?

• A. Chemoautotrophs
• B. Monerans
• C. Endospore
• D. Photoautotrophs

Answer: (A)

Organisms can be categorized by how they obtain energy. Those that rely on chemical reactions to harvest energy are chemotrophs, and when they also use carbon dioxide as their carbon source to build organic matter, they are chemoautotrophs. This means they don’t depend on sunlight for energy, unlike photoautotrophs, which power their chemistry with light. Chemoautotrophs typically derive energy from oxidizing inorganic compounds such as hydrogen sulfide or ammonia, allowing life in environments without light. The other terms don’t describe this energy source: monerans is an old grouping for bacteria, endospore is a dormant cell, and photoautotrophs use light instead of chemical reactions.