Question

While examining a rock surface, you have discovered an interesting new organism. Which of the following criteria will allow you to classify the organism as belonging to Bacteria but not Archaea or Eukarya?

1. Cell walls are made primarily of peptidoglycan.
2. It can survive at a temperature over 100 degrees C.
3. The organism does not have a nucleus
4. It is unicellular

Answer 1

The criterion that would allow classifying the organism as belonging to Bacteria but not Archaea or Eukarya is: "Cell walls are made primarily of peptidoglycan."

Step-by-step explanation:

Classifying organisms into distinct domains (Bacteria, Archaea, and Eukarya) involves various criteria. The presence of peptidoglycan in cell walls serves as a significant differentiator between Bacteria and Archaea/Eukarya. Bacteria have cell walls primarily composed of peptidoglycan, a unique characteristic not found in Archaea or Eukarya. This structural component provides rigidity to bacterial cells and protects them from environmental stressors.

While the other criteria mentioned - survival at high temperatures (>100 degrees C), lack of a nucleus, and unicellularity - can be observed in various organisms, they do not exclusively define the Bacteria domain. Some Archaea can also survive in extreme temperatures, lack a true nucleus, and can be unicellular. However, the presence of peptidoglycan in cell walls specifically aligns with the characteristics of Bacteria. This feature is used in bacterial cell wall synthesis and is distinctively absent in Archaea and Eukarya, making it a defining criterion for classifying organisms within the Bacteria domain.