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๐ฌ Think about it
A single drop of pond water can hold a whole crowd of living things, all moving and feeding — and you can't see a single one. So what are these hidden creatures? Let's find out.
What are microorganisms?
What makes a living thing a microbe?
Microorganisms
Too small to see
Too small to see
Needs a microscope
One or very few cells
Example:
Bacteria
Amoeba
Still fully alive
Grows and multiplies
Lives in water, soil, air
Example:
Fungi
Algae
- They are living things too small to see with the naked eye.
- "Micro" means very small; "organism" means a living being.
- They are also called microbes.
Where are microorganisms found?
Where do microbes live?
Microbes
Found all around us
In water
Ponds and stagnant water
Example:
Pond water
Stagnant water
In soil and air
Even in extreme places
Example:
Hot water springs
Snow cold zones
Inside living bodies
Even inside our gut
Example:
Bacteria in our intestine
- They are found almost everywhere.
- They live in water, soil, air, and food.
- Some even live inside our body, like in our gut.
What are the main types of microorganisms?
Are all microbes single-celled?
Microorganisms
Four main groups
Unicellular
Made of just one cell
Example:
Bacteria
Amoeba
Paramecium
Yeast
Multicellular
Made of many cells
Example:
Mould
Some fungi
Some algae
| Group | Example | What it looks like |
|---|---|---|
| Protozoa | Amoeba , Paramecium | Single cell, irregular or slipper-shaped |
| Algae | Chlamydomonas , Spirulina | Green because of chlorophyll |
| Fungi | Bread mould, yeast | Branched filament, no chlorophyll |
| Bacteria | Lactobacillus , Rhizobium | Spherical, comma, spiral or rod-shaped |
- They include protozoa, algae, fungi, and bacteria.
- Some are unicellular (one cell), like bacteria.
- Some are multicellular (many cells), like some fungi and algae.
๐ฌ
Activity 2.4 — Let us observe pond water/stagnant water
How do we look for life in pond water?
Collect pond or stagnant water
With the help of your teacher or an elder
↓
Place a drop on a slide
Use a dropper
↓
Cover it with a coverslip
And put the slide under the microscope
↓
Tiny moving organisms appear — ones the naked eye cannot see
In this Activity, we will put a drop of pond water under the microscope and look for living things in it.
Materials needed
Pond or stagnant water, a container, a dropper, a glass slide, a coverslip, and a microscope.
Procedure
1. With the help of your teacher or an elder, collect pond or stagnant water in a container.
2. Use a dropper to place a drop of this water on a microscope slide.
3. Put a coverslip over the drop.
4. Observe the slide under the microscope.
5. Look for the tiny organisms found in the pond or stagnant water.
2. Use a dropper to place a drop of this water on a microscope slide.
3. Put a coverslip over the drop.
4. Observe the slide under the microscope.
5. Look for the tiny organisms found in the pond or stagnant water.
Observation
You see many tiny moving organisms in the drop of water.
Explanation
Pond and stagnant water contain microbes that are too small to see with the naked eye.
Pond water is full of tiny moving organisms that the naked eye cannot see.
โ Summary
- Pond water holds microbes
- A microscope reveals them
- Microbes live in water
๐ฌ
Activity 2.5 — Let us observe soil suspension
How do we make a soil suspension?
Collect moist soil in a beaker
Use a spoon or gloves — never bare hands
↓
Add water and stir
Stir with a glass rod; the liquid looks dirty
↓
Let the mixture settle
Keep it aside for some time
↓
Take a drop from the top layer
Place it on a slide and cover it
↓
Small moving organisms appear again — even soil holds a variety of microbes
In this Activity, we will make a soil suspension and check whether soil, too, holds tiny living things.
Materials needed
Moist soil, a beaker, water, a glass rod, a spoon or gloves, a dropper, a glass slide, a coverslip, and a microscope.
Procedure
1. Collect some moist soil from a field or garden in a beaker. Do not touch it with bare hands — use a spoon or gloves.
2. Pour some water into the beaker and stir it with a glass rod. This liquid with fine soil particles is called soil suspension.
3. Keep it aside for some time and let the mixture settle.
4. Use a dropper to take a drop of water from the top layer and place it on a slide.
5. Cover it gently with a coverslip and observe under the microscope.
2. Pour some water into the beaker and stir it with a glass rod. This liquid with fine soil particles is called soil suspension.
3. Keep it aside for some time and let the mixture settle.
4. Use a dropper to take a drop of water from the top layer and place it on a slide.
5. Cover it gently with a coverslip and observe under the microscope.
Observation
You see small moving organisms similar to those in the pond water.
Explanation
Even soil suspension contains many tiny creatures that cannot be seen with the unaided eye.
Even soil holds a variety of microorganisms.
โ Summary
- Soil suspension holds microbes
- A microscope reveals them
- Microbes live in soil too
๐
Activity 2.6 — Let us study
How do we record what we found?
Perform Activities 2.4 and 2.5
Observe the pond water and the soil suspension
↓
Collect more information
From the library and from the internet
↓
Record the pond water data
Amoeba, Paramecium, algae — shape and movement
↓
Record the soil data
Bread mould, mould, algae, bacteria — shape and structure
↓
The microbes sort into four groups: protozoa, algae, fungi and bacteria
In this Activity, we will study the recorded observations of pond water and soil, and name the microbes found.
Materials needed
The prepared slides from Activity 2.4 and 2.5, a microscope, and reference pictures of microbes.
Procedure
1. Observe each slide carefully under the microscope.
2. Note the shape and colour of each organism you see.
3. Note whether it moves or stays still.
4. Compare each one with the reference pictures.
5. Record which group every microbe belongs to.
2. Note the shape and colour of each organism you see.
3. Note whether it moves or stays still.
4. Compare each one with the reference pictures.
5. Record which group every microbe belongs to.
Observation
Amoeba and Paramecium are protozoa (single-celled, moving); algae are green with chlorophyll; bread mould is a fungus with branched filaments; bacteria are spherical, comma, spiral, or rod-shaped.
Explanation
A microscope magnifies these 100–400 times, letting us see and sort the four main groups of microbes.
Pond water and soil give protozoa, algae, fungi and bacteria — four groups of microbes.
โ Summary
- Microbes differ in shape and colour
- They sort into four groups
- A microscope makes them visible
Important Points
- Microbes are unicellular or multicellular.
- The four main groups studied are protozoa, algae, fungi, and bacteria.
- A foldable paper microscope makes the microscopic world accessible cheaply.
๐ Ever heard of ...
- Viruses are microscopic and acellular (not made of cells).
- They are different from other microorganisms.
- They can multiply only after they enter a living host cell.
- They reproduce only inside that host organism, never on their own.
- They may infect plant, animal, or bacterial cells and cause disease.
โ
Test Yourself
-
What does "micro" mean?
View Answer
Very small. -
Name two unicellular microorganisms.
View Answer
Bacteria and Amoeba. -
Name the four groups of microbes.
View Answer
Protozoa, algae, fungi, and bacteria. -
How many times does a microscope magnify?
View Answer
About 100–400 times. -
Where can microbes be found?
View Answer
In water, soil, air, food, and inside living bodies.
Important Definitions
- Microorganism (microbe) — A living thing too small to be seen with the naked eye.
- Unicellular — Made of a single cell.
- Multicellular — Made of many cells.
๐ NCERT Question 5 — Identify the following microorganisms
Identify the following microorganisms:
View Answer →
