NEET 2025 MCQ with Answer Explanation : “Biological Classification”.

31. Which of the following is a common characteristic of bacteria and blue-green algae?
    a) Both have a well-defined nucleus
    b) Both are eukaryotes
    c) Both contain 80S ribosomes
    d) Both are prokaryotic

Answer: d) Both are prokaryotic

Explanation:
Bacteria and blue-green algae (cyanobacteria) are prokaryotes, meaning they lack a true nucleus and membrane-bound organelles.

32. Which one of the following organisms is called the ‘sulfur bacterium’?
    a) Thiobacillus
    b) Clostridium
    c) Bacillus
    d) Rhizobium

Answer: a) Thiobacillus

Explanation:
Thiobacillus is known as a sulfur bacterium because it is involved in the oxidation of sulfur compounds.

33. The protein coat surrounding the viral genetic material is called:
    a) Capsule
    b) Capsid
    c) Envelope
    d) Peptidoglycan

Answer: b) Capsid

Explanation:
The capsid is the protein shell that encloses the genetic material of a virus, providing protection and aiding in its transmission.

34. Which of the following structures is absent in prokaryotic cells?
    a) Plasma membrane
    b) Cell wall
    c) Mitochondria
    d) Ribosome

Answer: c) Mitochondria

Explanation:
Prokaryotic cells lack membrane-bound organelles like mitochondria. Their energy is produced through processes in the plasma membrane.

35. Which of the following organisms is involved in the production of antibiotics?
    a) Aspergillus
    b) Penicillium
    c) Spirogyra
    d) Rhizopus

Answer: b) Penicillium

Explanation:
Penicillium is a genus of fungi used to produce the antibiotic penicillin, discovered by Alexander Fleming.

36. Which organism lacks cell walls?
    a) Fungi
    b) Mycoplasma
    c) Bacteria
    d) Algae

Answer: b) Mycoplasma

Explanation:
Mycoplasma is a genus of bacteria that lacks a cell wall, making it resistant to many antibiotics like penicillin.

37. The symbiotic association of fungi and algae is called:
    a) Mycorrhiza
    b) Lichen
    c) Root nodules
    d) Cyanobacteria

Answer: b) Lichen

Explanation:
Lichens are symbiotic associations between fungi and algae (or cyanobacteria). The fungus provides structure and protection, while the algae carry out photosynthesis.

38. Which of the following organisms causes malaria?
    a) Plasmodium
    b) Entamoeba
    c) Trypanosoma
    d) Leishmania

Answer: a) Plasmodium

Explanation:
Plasmodium, a protozoan, is the causative agent of malaria. It is transmitted to humans by Anopheles mosquitoes.

39. Which of the following organisms belong to the kingdom Monera?
    a) Amoeba
    b) Spirogyra
    c) Bacteria
    d) Paramecium

Answer: c) Bacteria

Explanation:
Bacteria are prokaryotic organisms that belong to the kingdom Monera. They lack a true nucleus and membrane-bound organelles.

40. In which of the following would you expect to find peptidoglycan?
    a) Eukaryotic cells
    b) Fungal cell walls
    c) Bacterial cell walls
    d) Viruses

Answer: c) Bacterial cell walls

Explanation:
Peptidoglycan is a key component of the bacterial cell wall, providing structural strength.