<u>Answer</u>: Bacteria through the nucleoid (number 5).
<u>Explanation</u>:
Both paramecium and bacteria are single celled organisms. However, they differ by the fact that the first one is an eukaryote and the second one a prokaryote.
Furthermore, they differ in their capacity to mutate and adapt to environmental changes. Bacteria have a simple internal structure that lacks any organelles and are very adept at adapting to environmental changes. Besides their capacity for high mutation rates, they are also capable of picking up genetic information from their environment through a process called <em>transformation</em>.
Through transofrmation, environmental DNA enter the living bacteria through its cell membrane. Double stranded DNA will have one strand dissolved through hydrolysis, whereas the second strand may recombine with the bacterial <em>chromosome (nucleoid)</em>. Thus, this new genetic material will become incorporated into the bacterium's genome.
