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2 The Invisible Living World:

Beyond Our Naked Eye

Intended Learning Outcomes
What is a Cell?
Varia on in Shape and Structure of Cells
What are the Levels of Organisa on in the Body of a Living Organism?
What are Microorganisms?
How are We Connected to Microbes?
Key Players in Cleaning the Environment
Microorganisms and Food
Amazing Microalgae: Tiny Helpers in Water

Stepping Stones

1. Have you ever wondered what you might see if the invisible world around
you became visible?
2. A student observes that when curd is le out for a day, it becomes sourer.
What are two possible explana ons for this observa on?

The human eye cannot see very tiny objects on its own. For many years,
Science people did not know about the small things around them because they
Bytes
were too small to notice. Then, they discovered that a curved piece of glass

Testimony could make these objects look bigger. This glass was shaped like a lentil
It would be fascina ng to seed, so it was called a lens. As time went on, people made better and
see the microorganisms,
like bacteria, fungi, stronger lenses. These led to the creation of tools like magnifying glasses
protozoa, and virus and microscopes. With microscopes, humans were finally able to see tiny
constantly interac ng living things that had been invisible before, opening up a whole new hidden
with our environment
and even inside our world. Let us now hersh how this discovery helped scientists explore living
bodies. things too small to be seen by our eyes.

All around us, there are many different kinds of living things. Some are
small, some are big, and they come in many shapes, sizes, and colours.
Every plant and animal is called an organism . Some organisms are so tiny
that it is hard to see them without help. Our eyes can only see objects
above a certain size, so we cannot clearly see very tiny things. That is why

some people use reading glasses—to help their eyes see well. In the same

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Science-8