The Invisible Living World: Beyond Our Naked Eye Class 8 Notes Science Chapter 2 II CBSE Notes II NCERT Notes II Curiosity Class 8 II Complete notes

 

The Invisible Living World: Beyond Our Naked Eye

Microorganisms are small-sized organisms and are not visible to the unaided eye. (micro means very small; organisms mean’s living beings)

Kinds of Microorganisms:

Bacteria, fungi, protozoa and some algae are different kinds of microorganisms.

They are either unicellular or multicellular.

Viruses are also small in size, but they are different from other microorganisms since they reproduce only inside the host organism.

Levels of Organisation

Structure of cell

All living beings are made up of cells. The main parts of a cell are— cell membrane, cytoplasm, and nucleus — are the basic parts of a cell.

The outer layer is called the cell membrane. The round structure in the middle is the nucleus, which is also covered by a thin membrane. The space between the cell membrane and nucleus is filled with cytoplasm.

Cytoplasm contains other components of the cell and compounds, such as carbohydrates, proteins, fats, and mineral salts.

Plant, fungal, and bacterial cells have an extra covering, called a cell wall, around the cell membrane. Bacteria lack a well-defined nucleus.

Cells differ in shape and size. Their shape is related to the function performed by them.

Our Connection with Microbes

1. Microbes are Everywhere: They are present in extreme environments:

• Hot springs
• Ice regions
• Deep oceans

Our intestine has many bacteria that help in digestion

2. Microorganisms help’s in cleaning the environment

Microorganisms’ breakdown the complex substances of fallen leaves into simpler substances that are rich in nutrients by a process called decomposition.

Microorganisms also decompose bodies of dead animals. So, microbes help recycle the waste and return important nutrients to nature thus clean our environment.

3.Microbes as a source of biogas

Some bacteria and fungi live without oxygen and decompose plant, animal waste, and wastewater.
During this process, they produce biogas (mainly methane and carbon dioxide), which is used as a fuel for cooking, heating, electricity, and vehicles.

4.Microbes in Food

Yeast is a type of microorganism, grows well in warm conditions. It belongs to fungi.

During respiration, carbon dioxide is released by Yeast along with small amount of alcohol.

This special property of yeast is used in the process of making breads, cakes and other Bakery items. Carbon dioxide makes the dough soft and fluffy while alcohol gives the dough a slightly different smell.

Some bacteria, such as Lactobacillus, help in fermentation of batter for making idli and dosa, and dough for making bhatura.

5.Nitrogen Fixation:

• Some Microorganisms convert nitrogen into usable form for plants, by trapping nitrogen from the air.
• Example: Rhizobium bacteria
• Rhizobium, form the swollen regions called nodules and live in them,
• Nodule carrying plants helps plants grow better without chemical fertilisers.

 6.Other uses of Microorganisms

Microalgae are tiny plant-like organisms that make food using sunlight and produce a large amount of Earth’s oxygen.

They are nutritious, support aquatic life, help clean water, and are used in supplements and biofuel.

Spirulina is called a superfood because it is rich in protein (over 60%) and a good source of vitamin B12, with low fat and sugar.
It is also becoming a popular and feasible livelihood option through Spirulina farming.