Introduction And Microorganisms

Introduction

We see living things all around us. Animals and plants are the well-known examples of living things. However, there are some groups of living things that we cannot see with our naked eyes. These are the microorganisms. The word “microorganism” is the combination of two words, ‘micro’ means very small and ‘organism’ means living thing. In this unit, we shall discuss the microorganisms.

Microorganisms

Microorganisms are the living things that we cannot see with naked eye. They can only be seen with the help of a microscope. Microscope is a special type of instrument used for producing a much larger view of very small objects so that they can be seen clearly. Microorganisms may be single-celled or may have more than one cell. They are widely distributed in the environment and are found in the air, soil, dust, foods, etc.

Main Groups of Microorganisms - Virus, Bacteria and Fungi

Main Groups of Microorganisms

(Virus, Bacteria and Fungi)

There are many different kinds of microorganisms. They are classified on the basis of shape, structure, feeding habit, etc. Main groups of microorganisms are viruses, bacteria and fungi.

Viruses

Viruses are the smallest of all microorganisms. The word virus means poison. They are always harmful for living things as they cause diseases in humans, animals, plants and other organisms.
 

Bacteria

Bacteria are single-celled microorganisms that are present all around us. They are found in the air, water and soil. They are of different shapes. Some of them are harmful by causing different diseases such as Food Poisoning, Pneumonia, Tuberculosis, etc. However, many of them are beneficial for us.

Fungi (Moulds and Yeasts)

Fungi cannot make their own food. They absorb food from the source they are growing on. Some fungi grow and feed on dead material while others feed on living plants and animals. Most fungi are harmless but some cause diseases in plants and humans. Moulds and yeasts are common examples of microscopic fungi.

Interesting Information

There are more than 5,000 known kinds of bacteria.

A cup of yogurt has billions of bacteria.

Advantages of Microorganisms

Advantages and Disadvantages of Microorganisms

Most of the microorganisms do not cause diseases and are beneficial. Some advantages and disadvantages of microorganisms are mentioned below:

Advantages of Microorganisms

(i) Making Foods

Some microorganisms such as bacteria and yeast are used in the manufacture of different foods for example, yeast help in making of bread and cheese while bacteria help in yogurt making.

(ii) Help in digestion

Many bacteria live in human intestine and help in digestion of food.

(iii) Making medicines

Some fungi are used to obtain antibiotics. Antibiotics are the compounds that are used to kill and control the growth of bacteria which i in humans and animals.

Now-a-days, many types of antibiotics are used against the bacterial diseases. The first antibiotic called “Penicillin” was obtained from a fungus, “Penicillium”.

(iv) Microorganisms as decomposers

Some microorganisms such as bacteria and fungi break down the dead bodies into simpler substances. These simpler substances are mixed in the soil for reuse by the plants and other organisms. Such microorganisms which break down the dead bodies by natural process are called decomposers. In this way, microorganisms recycle the materials between living and non-living environment.

Disadvantages of Microorganisms

Disadvantages of microorganisms

(i) Diseases

Many of the microorganisms’ cause diseases in humans, animals and plants. Some viral diseases are common cold, influenza, measles, chicken pox, polio, hepatitis and AIDS.

Certain bacteria cause cholera, typhoid and food poisoning in humans. Some fungi also cause diseases in animals and plants. Athlete’s foot, ringworm in humans and rust, smut in wheat, corn, rice and sugarcane are fungal diseases.

(ii) Spoilage of food

Some microorganisms spoil food by growing init and make it unfit for human use. Examples are souring of milk by bacteria, the growth of mould on bread, and the rotting of fruits and vegetables by bacteria and fungi both.

Do you Know?

Microorganisms which cause diseases are called pathogens.

Activity

Place a wet slice of bread in a cabinet.

Leave it for a few days and then observe.

Record your observations and discuss them with your teacher and classmates.

Investigate

Food gets spoiled if not store properly. Investigate a few ways of storing food to keep it safe and fresh.

Infection And How do microorganisms enter human body?

Infection

The attack of disease-causing microorganisms in the body of an animal or plant is called infection. Infectious diseases quickly spread from one individual to another.
 

How do microorganisms enter human body?

Microorganisms can enter the human body by the following ways:

Through air

When a person sick with flu sneezes, germs are spread in the air. These germs can enter the lungs of another person who breathes in such an air.

Through water

Some harmful microorganisms are transferred in the human body by drinking water containing microorganisms.

Caution!

We should drink boiled water to avoid water borne diseases.

Through contaminated food

Contaminated food contains harmful microorganisms. These microorganisms enter the body of a person who eats the contaminated food.

Through animals

Animals like mosquitoes transfer the harmful microorganisms into the body of a person during blood sucking.

Through cuts on the skin

Scratches or cuts on the skin also provide entry points for germs. Bacteria causing tetanus enter the body through cuts or injuries on the skin.

Ways to avoid Infection

Ways to avoid Infection

Here are some simple ways to prevent infections:

Dirty hands are the major source of germs. Wash your hands frequently especially before eating and after using toilet.

Always eat healthy and fresh food. Wash fruits before eating them. Always cover the food.

Brush your teeth regularly after meal, before going to bed and early in the morning.

Keep your homes, schools and surroundings clean.

Take a bath at least once a day.

In case of injury or cut on the skin, clean it and cover it with a bandage and consult a doctor.

Cut your nails regularly.