Answer:
b. chemoautotrophs
Step-by-step explanation:
To live, all living beings fundamentally need two requirements: energy and matter, mainly carbon. Therefore, different organisms can be classified according to two criteria: the source of energy they use and the origin of the chemical form of carbon they require as a nutrient. Depending on the carbon source they use, the following types of organisms can be distinguished: autotrophs, which use the inorganic carbon (carbon dioxide, CO2) as their carbon source; and heterotrophs, which use organic carbon as their carbon source. Depending on the energy source, the following types of organisms can be distinguished: phototrophs, which obtain energy directly from sunlight; and chemotrophs, which get energy from chemical compounds. Chemotrophs are usually subdivided into two groups depending on whether they obtain the energy of organic (chemoorgano-) or inorganic (chemoolite-) chemical reactions.
Chemotrophic or chemosynthetic organisms are those capable of using reduced inorganic compounds as substrates to obtain energy and use it in respiratory metabolism. It is a faculty known as chemosynthesis. These can be chemoautotrophs or chemoheterotrophs. Like photoautotrophs (such as algae and plants), chemoautotrophs use CO2 as the main source of carbon, but unlike them, they do not use light as a source of energy but instead obtain it by oxidation of reduced inorganic compounds, such as NH3 , NO2-, H2, reduced forms of sulfur (H2S, S, S2O3-) or Fe2 +. Its cellular carbon is derived from CO2 and is assimilated through the reactions of the Calvin cycle, analogously to plants. As a result of their distinctive ability to grow in strictly mineral media, in the absence of light, these organisms are often referred to as chemoautotrophs. On the contrary, chemoheterotrophic organisms (or simply heterotrophs), such as animals and fungi, oxidize reduced organic molecules, such as glucose (via glycolysis), triglycerides (via beta oxidation) or amino acids ( oxidative deamination route) to obtain metabolic energy (ATP) and reducing power; In addition, they are unable to use CO2 as a carbon source.