Also, you can&#x27;t make the same assumptions with chemotrophs as you can with phototrophs. Photosynthetic organisms use sunlight to power their chemical reactions so they can thrive anywhere there is sunshine, water and CO2. Chemotrophs can only thrive where there is a local concentration of their &quot;food&quot; (iron, in this case) compared to the average concentration.<p>Let me explain it this way. Say you have an environment rich in elemental oxygen and iron. What&#x27;s to stop the oxidation from occurring naturally before an organism can facilitate it and harness the energy? Nothing. This is why you only see chemotrophs around local high concentrations (like deep sea vents.) This means it is inherently impossible for chemotrophs to ever become widespread.