A bacterial species differs from a species of eukaryotic organisms in that a bacterial species:

• A. is always multicellular
• B. is defined primarily by genetic similarity and phenotypic characteristics rather than reproductive isolation
• C. contains membrane-bound organelles such as a nucleus
• D. can reproduce sexually through meiosis

Answer: (B)

Verified step by step guidance

1. Understand the concept of a species in both bacterial and eukaryotic contexts. In eukaryotes, species are often defined by the ability to interbreed and produce fertile offspring (reproductive isolation).
2. Recognize that bacteria reproduce asexually through binary fission, so reproductive isolation is not a defining factor for bacterial species.
3. Learn that bacterial species are primarily defined based on genetic similarity (such as DNA-DNA hybridization or 16S rRNA gene sequence similarity) and observable phenotypic characteristics (morphology, metabolism, etc.).
4. Note that bacteria are unicellular organisms and do not contain membrane-bound organelles like a nucleus, which is a key difference from eukaryotic cells.
5. Understand that bacteria do not reproduce sexually through meiosis; instead, they reproduce asexually, which further differentiates their species concept from that of eukaryotes.