What do you understand by microorganisms ? Describe their different forms.

Organisms present around us which cannot be seen with naked eyes are called microorganisms. They are present in soil, water and air.

Microorganisms can be divided into five groups:

(i) Bacteria are the non-green single celled microscopic organisms. They have a rigid cell wall. It has a nuclear material. They are the simple most common form of life on earth. They have different shapes and sizes.

(ii) Algae are aquatic, photosynthetic organisms. In simple terms they are called sea weeds. They range in size, colour. Algae are of green, blue, red and blue-green colours.

(iii) Fungi are both unicellular and multicellular. Moulds, mushrooms etc. are fungi.

(iv) Protozoa are one called living things. They range from 2 to 200 microns. Amoeba, Paramecium, Euglena and Plasmodium etc. are protozoas.

(v) Viruses are the non-cellular microbes. They are smaller than bacteria and multiply only inside a living cell.