Igcse Model Questions Vol1 2017 Biology Question 2

Three microorganisms are described as follows:\n\n- Organism X: cell wall contains peptidoglycan; membrane lipids are ester‑linked fatty acids; it metabolises glucose aerobically.\n- Organism Y: lacks a peptidoglycan cell wall; its membrane lipids are ether‑linked isoprenoids; it obtains energy by methanogenesis.\n- Organism Z: possesses a nucleus, membrane‑bound organelles and chloroplasts; it performs photosynthesis.\n\nClassify each organism into the correct domain (Bacteria, Archaea, or Eukarya). Then, considering that halophilic (high‑salt) environments favour organisms with ether‑linked membrane lipids, indicate which of the three is most likely to survive in a habitat containing \(15\%\) (w/v) NaCl.