Which of the following is the best evidence to support that Domain Bacteria and
Domain Archaea are closely related?
Organisms in both domains survive only in extreme temperature environments
without oxygen.
Organisms in both domains are pathogenic and all can infect humans to cause
illness.
Organisms in both domains are all single-celled, but can join together to be
multicellular in certain environmental conditions.
Organisms in both domains are all single-celled with a cell wall and lack a
nucleus.

The shared characteristic of being prokaryotic, specifically single-celled with a cell wall and lacking a nucleus, presents evidence that Domain Bacteria and Domain Archaea are closely related.

Explanation:

Organisms in both domains are all single-celled with a cell wall and lack a nucleus. This shared characteristic of being prokaryotic is a key piece of evidence that Domain Bacteria and Domain Archaea are closely related as both fall under the category of prokaryotes.

Although differences exist between Archaea and Bacteria, such as genetic and biochemical distinctions, the fundamental similarity of lacking a nucleus places them in the same category of prokaryotes, indicating a close relationship.

Furthermore, the fact that both Archaea and Bacteria include extremophiles, organisms thriving in extreme environments, suggests a shared evolutionary history and supports their close relationship.

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