36. Nuclear membrane is absent in
(A) Chlamydomonas
(B) Nostoc
(C) Volvox
(D) Chlorella

Nostoc lacks a nuclear membrane as the only prokaryote among the options. Chlamydomonas, Volvox, and Chlorella are eukaryotes with well-defined nuclei. This distinction arises from prokaryotic versus eukaryotic cell structure.​

Correct Answer

The correct option is (B) Nostoc. Nostoc, a cyanobacterium, is prokaryotic and features a nucleoid region without a membrane-bound nucleus. Eukaryotes like the others possess a double-layered nuclear envelope.​

Option Analysis

• (A) Chlamydomonas: This unicellular green alga is eukaryotic, containing a distinct nucleus enclosed by a nuclear membrane, along with organelles like chloroplasts.​

• (B) Nostoc: As a prokaryotic cyanobacterium (blue-green alga), Nostoc has no nuclear membrane; its genetic material lies in a nucleoid within the cytoplasm.​

• (C) Volvox: Volvox colonies consist of eukaryotic algal cells with membrane-bound nuclei, flagella, and chloroplasts.​

• (D) Chlorella: This single-celled green alga is eukaryotic, featuring a true nucleus surrounded by a nuclear membrane.​

Biological Context

Prokaryotes like Nostoc lack membrane-bound organelles, enabling simpler, faster reproduction suited to extreme environments. Eukaryotes such as Chlamydomonas, Volvox, and Chlorella evolved complex nuclei for advanced gene regulation and multicellular potential. This MCQ tests fundamental cell biology classification for exams like NEET.​