2.3 What Are Microorganisms?

Last updated at June 7, 2026 by

Microorganisms

  • Some living things are made of one or very few cells.
  • They are too small to see with the naked eye.
  • These are called microorganisms or microbes.
  • We need a microscope or foldscope to see them.
  • They live in water, soil, air, and even inside our body.
Example 1 — In Pond Water
  • A drop of pond water is viewed under a microscope.
  • Tiny moving creatures like Amoeba appear.
  • So pond water is full of microbes.
Example 2 — In Soil
  • A drop of soil suspension is viewed too.
  • It also shows tiny moving organisms.
  • So soil is full of microbes as well.
Important Points
  • Some microbes are unicellular, like bacteria and Amoeba.
  • Some are multicellular, like some fungi and algae.
  • A microscope magnifies them about 100 to 400 times.
Definition — Microorganism
A microorganism is a tiny living being, made of one or a few cells, that cannot be seen with the naked eye.
Definition — Foldscope
A foldscope is a low-cost, foldable paper microscope that makes the microscopic world accessible to many people.
🔬 Activity 2.4 — Let Us Observe Pond Water
Materials needed
Pond or stagnant water.
A dropper, slide, coverslip, and microscope.
Procedure
Collect pond water with an elder's help.
Place a drop on a slide and add a coverslip.
View it under the microscope.
Observation
You see tiny moving organisms in the water.
Explanation
Pond water holds many microbes too small for the naked eye. So the microscope makes them visible.

→ Pond water is full of microbes.

◆ Summary
  • Take pond water.
  • View a drop under a microscope.
  • See tiny organisms.
  • Microbes live in water.
🔬 Activity 2.5 — Let Us Observe Soil Suspension
Materials needed
Moist soil and a beaker.
Water, a glass rod, dropper, slide, and microscope.
Procedure
Collect moist soil using a spoon, not bare hands.
Stir it in water to make a soil suspension and let it settle.
Take a drop from the top and place it on a slide.
Cover and view it under the microscope.
Observation
You see small moving organisms, like those in pond water.
Explanation
Soil also holds many microbes. So even soil suspension is full of tiny creatures.

→ Soil is full of microbes too.

◆ Summary
  • Stir soil in water.
  • Let it settle.
  • View a top drop.
  • See tiny organisms.
🔬 Activity 2.6 — Let Us Study
Procedure
Record the organisms seen in pond water and soil.
Use library and internet to identify them.
Group them as protozoa, algae, fungi, and bacteria.
Table 2.1 — Organisms in Pond Water
S.No. Organism Remarks
1. Amoeba (Protozoa) Single cell, moving, irregular shape
2. Paramecium (Protozoa) Single cell, moves using special structures
3. Algae Single cell, green, moves using special structures
Table 2.2 — Organisms in Soil Suspension
S.No. Organism Remarks
1. Bread mould (Fungi) Branched filament, no chlorophyll, sac-like structure
2. Mould (Fungi) Branched filament, no chlorophyll, brush-like structure
3. Algae Spherical, has chlorophyll (green)
4. Bacteria Spherical, comma, spiral, or rod-shaped, with hair-like projections
Explanation
These show a variety of microbes around us. They are grouped as protozoa, algae, fungi, and bacteria.

→ Microbes come in many types and shapes.

◆ Summary
  • Record what you see.
  • Identify each organism.
  • Group them by type.
  • Protozoa, algae, fungi, bacteria.
🏭 Ever Heard Of — Viruses
Viruses are microscopic and acellular, meaning they are not made of cells.
They multiply only when they enter a living cell. They may infect plants, animals, or bacteria, and may cause disease.
🧠 Test Yourself — Sections 2.2 and 2.3
  1. What is the order of the levels of organisation?
    View Answer Hide Answer
    Cell → tissue → organ → organ system → organism.
  2. What is a microorganism?
    View Answer Hide Answer
    A tiny living being, of one or a few cells, that cannot be seen with the naked eye.
  3. Name the four groups of microorganisms.
    View Answer Hide Answer
    Protozoa, algae, fungi, and bacteria.
  4. How are viruses different from other microbes?
    View Answer Hide Answer
    They are acellular and multiply only inside a living host cell.
  5. What is a foldscope?
    View Answer Hide Answer
    A low-cost, foldable paper microscope.
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