Answer:
In the deep ocean layers where the sunlight does not reach, these organisms that are chemoautotrophic use sulfides from the hydrothermal vents to perform chemosynthesis instead of photosynthesis.
Explanation:
Chemoautotrophic organisms are the ones that are adapted to the absence of sunlight. Such organisms identify electron donors in their vicinity and derive energy from the oxidation reactions that these electron donors (mostly, inorganic compounds) undergo.
The major reason for the development of such a trait in these organisms is the depth that they live at. On deep-sea floors, there is an abundance of sulfides. Thus, the organisms living on there make use of the sulfides to fix carbon and obtain energy the required energy to sustain.
The process of chemosynthesis occurring on deep-sea floors due to the presence of carbon, sulfides, and oxygen culminates in the production of organic materials as an end result which the organisms feed on and sustain even when there is no sunlight available. These organisms majorly belong to the bacteria species called Archaea and Extremophiles.
