You may have seen many kinds of animals and plants.However, there are other living organisms around us which we cannot see with naked eye.These are called microorganisms or microbes. Examples of microorganisms are viruses, bacteria and some types of fungi. Microorganisms live everywhere on earth.in this unit, we will learn about microorganisms, their advantages and disadvantages.
2.1 Microorganisms
The word "micro" means very small and "organisms" means living things. These are small organisms thats we can not See with the Naked eyes.They can be seen with only the help of microscope.
Microorganisms are classified into three main groups; virus, bacteria and fungi.
i. Virus
'Virus' means poison. Virus is a smallest infective agent. It has two parts; head and tail.
The virus can be round, stick-shaped, tadpole-like or polyhedral. Viruses in humans cause cowpox, measles, sneezing, influenza, hepatitis, polio, etc. Mosaic disease in plants is also caused by a virus.
ii. Bacteria
Bacteria they are members of a large group. Bacteria are very small living organisms with no nucleus. They are found every where. There are millions of bacteria in the air around us, in the soil,in water and in our bodies. Bacteria have number of different shapes and sizes ranging from sphere to rod and coma shaped.Bacteria are both Useful good and bad for animals. In humans, diarrhea, whooping cough, pneumonia, tetanus and food poisoning are comon diseases caused by bacteria
iii Fungi
Fungi are simple microorganisms and are made up of thread like structures called hyphae Fungi include yeast, mushrooms and moulds, etc. Therefore, they depend on other living or non living organisms for their food. They play an important role in the recycling of carbon and other elements by decomposing dead living organism. Fungi play both beneficial and harmful roles Athlete's foot, ringworm and thrush are diseases caused by fungi.Yeast feeds on sugars. It is able to respire without oxygen.
2.3 Advantages and disadvantages of microorganisms
It is a common belief that all microorganisms only cause diseases, but this is not true. A large number of microorganisms are very useful for us and our environment.
Advantages of microorganisms
Following are are some
advantages of microorganisms.
Microorganisms help in the decomposition of dead bodies and organic wastes. Therefore, they clean the environment by removing dead bodies.
Bacteria fix the atmospheric nitrogen in the soil and provide it to plants.
Some bacteria are used for making food products. Yogurt could be made with the help of bacteria.
Bacteria help in the preparation of different medicines like antibiotics.
A fungus, yeast is used for making cheese and many bakery products.
Microorganisms are important for many processes in our body.
Fungi are used in making valuable medicines including penicillin and vitamins tablets.
Some microorganisms are used for making vaccines. Vaccines are used for making strong defense system in our bodies.
Some fungi called mushrooms are used as ingredients in recipes. They add flavor to meals. Edible mushrooms are used as food.
Disadvantages of microorganisms
Following are the disadvantages of microorganisms.
Microorganisms play key role in rotting food stuffs and cause decomposition and spoilage of food. Spoiled foods have bad smell and taste and cause many diseases.
Harmful microorganisms are pathogens (germs) as they cause different diseases. Diseases caused by different microorganisms are as follows.
Viruses cause cold, flu, measles and polio. Bacteria cause diarrhea, whooping cough, typhoid and tuberculosis. Fungi cause athlete's foot, ringworm and thrush etc.
2.4 Infection
When harmful microorganisms or germs enter in human body, they attack the cells of different body parts. Hence, they reproduce and increase their numbers. The natural immune system of human body tries to control the attack of the germs.
But, sometimes the attacking germs reproduce at such a great speed that our immune system cannot compete them. As a result, the cells destroy and we become the victim of different diseases. This condition is called infection. If infection remains uncured for a long time, the condition of the patient becomes critical which may cause death. Most infections are caused by bacteria and viruses but a few are caused by fungi. Some common infectious diseases caused by microorganism are given in Table 2.1
Table 2.1: Some common infectious diseases
Viral diseases
Influenza.
Common cold
Chicken pox
Polio
Hepatitis
AIDS
Bacterial diseases
Food poisoning
Pneumonia
Typhoid
Cholera K
Tuberculosis
Fungal diseases
Athlete's foot
Ringworm
Rust
Smut
