Final answer:
Methanogens are the group of archaea that use carbon dioxide as their terminal electron acceptor to produce methane during anaerobic respiration. They are part of the phylum Euryarchaeota and play a crucial role in the carbon cycle.
Step-by-step explanation:
The group of archaea that can use CO2 as their final electron acceptor during anaerobic respiration, producing CH4 (methane), is known as methanogens. Methanogens are interesting organisms that play a vital role in environments such as soil and the digestive tracts of ruminants like cows and sheep. As members of the phylum Euryarchaeota, methanogens are capable of reducing carbon dioxide in the presence of hydrogen, not only helping in the carbon cycle but also potentially affecting global climate due to methane being a potent greenhouse gas.
It's important to differentiate between methanogens and other types of archaea and bacteria. For instance, methanotrophs are bacteria and archaea that use methane as their carbon source, and they are different from methanogens which produce methane. Additionally, the various types of extremophiles like halophiles, thermophiles, and acidophiles have distinct characteristics and environmental niches that separate them from methanogens.