Describe the two mechanisms of autotrophy. Where on Earth might you expect to find one or the other of these two pathways to dominate?

Question

What will be an ideal response?

Answer 1

Autotrophs include plants, algae, and a host of microbes that can photosynthesize (e.g., cyanobacteria, purple and green sulfur bacteria) or chemosynthesize (e.g., colorless sulfur bacteria).

These autotrophic organisms produce organic matter from inorganic carbon sources, a process that requires energy (i.e., the chemical reactions do not occur spontaneously in nature). The organic material that autotrophs produce is a storehouse of energy, and will decompose abiotically (without the intervention of organisms), albeit at a slow rate, releasing that energy as heat. Heterotrophs simply accelerate these chemical reactions that would otherwise proceed at a slower pace abiotically, and in doing so, gain the energy they need to grow and reproduce.

In the case of photosynthesis, the sun provides the necessary energy. In chemosynthesis, energy-releasing inorganic chemical reactions (those that occur even without the involvement of organisms because they release energy), often involving oxygen and reduced compounds, are the primary source of energy.

Chemosynthesis is the mechanism of primary production of the midocean-ridge hydrothermal vent communities that exist at great depths in the ocean where sunlight does not penetrate.