Which of the following is NOT a group of microbes?

The correct answer is Option (3) → Insects

Microbes are organisms too small to be seen with the naked eye. NCERT lists them as protozoa, bacteria, fungi, microscopic animal and plant viruses, viroids and prions. The question asks for the group that does not belong to this list.

Option (1) Protozoans — Incorrect. Protozoa are single-celled eukaryotes such as Amoeba and Paramecium. They are microscopic, so they are counted among the microbes.

Option (2) Bacteria — Incorrect. Bacteria are microscopic prokaryotes. Many bacteria, such as Lactobacillus and Rhizobium, are the useful microbes described in this chapter.

Option (3) Insects — Correct. Insects are multicellular animals (arthropods) with jointed legs and a body that is easily seen with the naked eye. They are not microbes, although some of them, like aphids and mosquitoes, are pests controlled by biocontrol methods.

Option (4) Fungi — Incorrect. Fungi such as yeasts and moulds are microbes. Their colonies can be grown on nutritive media in a petri dish, and fungi like Penicillium and Aspergillus give us useful products.

NCERT Extract:
Microbes in Human Welfare – “… Microbes are diverse– protozoa, bacteria, fungi and microscopic animal and plant viruses, viroids and also prions that are proteinacious infectious agents. Some of the microbes are shown in Figures 8.1 and 8.2. Microbes like bacteria and many fungi can be grown on nutritive media to form colonies (Figure 8.3), that can be seen with the naked eyes. Such cultures are useful in studies on micro-organisms.”