Question

What is Chemosynthesis?

Answer 1

Ecosystems rely on the ability of some organisms to transform inorganic substances into food that can be exploited (or eaten!) by other organisms. Plants synthesize food through photosynthesis, hence the bulk of life on the earth is reliant on a food chain that revolves around sunlight. In situations where there is no sunlight and hence no plants, animals rely on primary production via a process known as chemosynthesis.

Complete answer:
Plants and some microorganisms can photosynthesize wherever there is enough sunshine — on land, in shallow water, and even inside and below transparent ice. Solar energy is used by all photosynthetic organisms to convert carbon dioxide and water into sugar (food) and oxygen.
Chemosynthesis is the process of synthesis of organic compounds by bacteria or other living organisms using energy derived from reactions involving inorganic chemicals, typically in the absence of sunlight. To synthesize sugar, all chemosynthetic organisms employ energy released by chemical processes, although various species take different routes. For example, at hydrothermal vents, vent bacteria oxidize hydrogen sulfide, add carbon dioxide and oxygen, and produce sugar, sulfur, and water.
Why do microorganisms that live deep beneath the ocean's surface use chemical substances to make food instead of sunlight? Photosynthesis is how most autotrophs get their food, but it's not the only method they get it. Some bacteria employ a different technique to synthesize food, one that uses chemical energy rather than light energy. Chemosynthesis is the name for this process. The oxidation of inorganic molecules (such as hydrogen gas, hydrogen sulphide ( ${H_2}S$ ), or ammonia ( $N{H_3}$ ) or methane as a source of energy, rather than sunlight, is used to transform one or more carbon molecules (typically carbon dioxide or methane, CH4) and nutrients into organic matter in chemosynthesis. Carbohydrates are formed during the chemosynthesis of hydrogen sulphide in the presence of carbon dioxide and oxygen ( $C{H_2}O$ ) can be produced:
$C{O_2}{\text{ }} + {\text{ }}{O_2}{\text{ }} + {\text{ }}4{H_2}S{\text{ }} \to {\text{ }}C{H_2}O{\text{ }} + {\text{ }}4S{\text{ }} + {\text{ }}3{H_2}O$
Many chemosynthesis-using creatures are extremophiles, meaning they can survive in extreme conditions such as the absence of sunshine and a wide variety of water temperatures, some of which are close to boiling.

Note: -
Photosynthesis and chemosynthesis fuel all life on Earth. Our understanding of chemosynthetic societies is relatively new, having been brought to light by ocean exploration in 1977, when humans discovered a thriving society where there was no light. Chemosynthetic bacterial colonies have since been discovered in hot springs on land as well as on the bottom near hydrothermal vents, cold seeps, whale carcasses, and sunken ships.