How do chemoautotrophs obtain energy? By consuming organic molecules By performing photosynthesis By oxidizing inorganic molecules By decomposing dead organisms
The correct answer and explanation is:
Correct Answer: By oxidizing inorganic molecules
Explanation (300 Words)
Chemoautotrophs are a type of autotrophic organism that obtain energy through chemical reactions, specifically by oxidizing inorganic molecules, rather than relying on light energy like photoautotrophs do.
These organisms are mostly bacteria and archaea found in environments where sunlight is absent or extremely limited—such as deep ocean hydrothermal vents, underground caves, or hot springs. Instead of using photosynthesis, they use a process known as chemosynthesis.
In chemosynthesis, chemoautotrophs oxidize inorganic substances such as:
- Hydrogen sulfide (H₂S)
- Ammonia (NH₃)
- Ferrous iron (Fe²⁺)
- Hydrogen gas (H₂)
This oxidation releases energy, which the organism then uses to convert carbon dioxide (CO₂) into organic molecules like sugars, which are essential for growth and survival. Because they use CO₂ as a carbon source and inorganic chemicals for energy, they are classified as chemoautotrophs (chemo = chemical energy, auto = self, troph = feeder).
For example:
- Bacteria near hydrothermal vents oxidize hydrogen sulfide (H₂S) and use the energy to fix CO₂, forming organic compounds.
- Nitrifying bacteria in soil convert ammonia (NH₃) into nitrites and then into nitrates, gaining energy in the process.
This form of metabolism is critical for nutrient cycling in ecosystems, particularly in extreme or deep-sea environments where photosynthetic organisms cannot survive. It also plays a key role in the nitrogen cycle, contributing to soil fertility.
Incorrect Options:
- By consuming organic molecules – This describes heterotrophs, not autotrophs.
- By performing photosynthesis – This applies to photoautotrophs, like plants and cyanobacteria.
- By decomposing dead organisms – This is done by decomposers like fungi and some bacteria, which are also heterotrophs.
Thus, chemoautotrophs derive energy by oxidizing inorganic molecules and build their own food from carbon dioxide, supporting entire ecosystems in environments where sunlight does not reach.