MICROORGANISMS AND ITS CLASSIFICATION

MICROORGANISMS AND ITS CLASSIFICATION

You have seen several kinds of plants and animals. However, there are other living organisms around us which we normally cannot see. These are called microorganisms or microbes. For example, you might have observed that during the rainy season moist bread gets spoilt and its surface gets covered with greyish white patches. Observe these patches through a magnifying glass. You will see tiny, black rounded structures. Do you know what these structures are and where do these come from?

Microorganisms

Activity 2.1:

*   Collect some moist soil from the field in a beaker and add water to it.

*   After the soil particles have settled down, observe a drop of water from the beaker under a microscope.

*   What do you see ?

Activity 2.2:

*   Take a few drops of water from a pond.

*   Spread on a glass slide and observe through a microscope.

Do you find tiny organisms moving around?

These observations show that water and soil are full of tiny organisms, though not all of them fall into the category of microbes. These microorganisms or microbes are so small in size that they cannot be seen with the unaided eye. Some of these, such as the fungus that grows on bread, can be seen with a magnifying glass. Others cannot be seen without the help of a microscope. That is why these are called microorganisms or microbes.

Classifications

Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae. Some of these common microorganisms are shown  in Figs. 2.1 - 2.4.

Figure 2.1: Bacteria

Figure 2.2: Algae (Chlamydomonas, Spirogyra)

Figure 2.3: Protozoa (Amoeba, Paramecium)

Figure 2.4: Fungi (Bread mould)

Figure 2.4: Fungi (Penicillium)

Figure 2.4: Fungi (spergillus)

Viruses are also microscopic but are different from other microorganisms. They, however, reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal. Some of the viruses are shown in Fig. 2.5. Common ailments like cold, influenza (flu) and most coughs are caused by viruses. Serious diseases like polio and chicken pox are also caused by viruses.

Figure 2.5: Viruses

Diseases like dysentery and malaria are caused by protozoa(protozoans) whereas typhoid and tuberculosis (TB) are bacterial diseases.

You have learnt about some of these microorganisms in Classes VI and VII.

Source: This topic is taken from NCERT TEXTBOOK

WHERE DO ORGANISMS LIVE?

WHERE DO ORGANISMS LIVE?

Microorganisms may be single-celled like bacteria, some algae and protozoa, or multicellular, such as many algae and fungi. They live in all types of environment, ranging from ice cold climate to hot springs; and deserts to marshy lands. They are also found inside the bodies of animals including humans. Some microorganisms grow on other organisms while others exist freely.

Source: This topic is taken from NCERT TEXTBOOK

MICROORGANISMS AND US

MICROORGANISMS AND US

Microorganisms play an important role in our lives. Some of them are beneficial in many ways whereas some others are harmful and cause diseases. Let us study about them in detail. Microorganisms are used for various purposes. They are used in the preparation of curd, bread and cake. Microorganisms have been used for the production of alcohol since ages.

They are also used in cleaning up of the environment. For example, the organic wastes (vegetable peels, remains of animals, faeces, etc.) are broken down into harmless and usable substances by bacteria. Recall that bacteria are also used in the preparation of medicines. In agriculture they are used to increase soil fertility by fixing nitrogen.

Source: This topic is taken from NCERT TEXTBOOK