Which term means a unicellular organism lacking a nucleus?

• A. Prokaryote
• B. Eukaryote
• C. Pathogen
• D. Nitrogen fixation

Answer: (A)

Prokaryotes are unicellular organisms that lack a membrane-bound nucleus. Their DNA sits in a region called the nucleoid rather than inside a true nucleus, giving them a simpler cellular organization compared to eukaryotes, which have a nucleus and other membrane-bound organelles. The term pathogen describes organisms that cause disease, which can be bacteria, fungi, or other types, so it’s about disease-causing ability rather than cellular structure. Nitrogen fixation is a metabolic process carried out by some microbes to convert atmospheric nitrogen into a usable form, not a description of an organism’s basic cell type. So the term that fits the description is prokaryote.