Category: Education

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OUTLINE OF PRESENTATION What are microorganisms? Types of microorganisms Where do microorganisms live? Friendly microorganisms Uses of microorganisms-: Commercial Use Medicinal Use Increasing soil fertility & cleaning the environment Harmful Microorganisms Disease causing microorganisms-: Humans Animals and Plants Food Preservation-: Food poisoning Preservation by various preservatives Nitrogen Fixation Nitrogen Cycle THE

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WHAT ARE MICROORGANINSMS? We 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, we might have observed that during the rainy season moist bread gets spoilt and its surface gets covered with greyish white patches. If we observe these patches through a magnifying glass, we will come to see black rounded structures. Do we know what these structures are and where do they come from? Let’s see.

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The Earth is full of tiny microorganisms though not all of them are considered in the category of microorganisms. These microorganisms cannot be seen with 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. Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae. Viruses are also microscopic. Some of these common microorganisms are shown below. TYPES OF MICROORGANISMS Amoeba Chlamydomonas Penicillium

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WHERE DO MICROORGANISMS LIVE? Microorganisms may be single-celled like bacteria, some algae and protozoa or multicellular such as algae and fungi. They can survive under all types of environment ranging from ice cold to hot climate. They are also found inside the bodies of animals including humans. Some microorganisms grow on other organisms while others exist freely. Microorganisms like amoeba can live alone, while fungi and bacteria may live in colonies. FRIENDLY MICROORGANISMS Microorganisms are used for various purposes. They are used in the preparation of curd, bread and cake. They 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 are broken down into harmless and usable substances by bacteria.. In agriculture they are used to increase soli fertility by fixing nitrogen.

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USES OF MICROORGANISMS Microorganisms are used for the large scale production of alcohol, wine and acetic acid. Yeast is used for commercial production of alcohol and wine. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice, crushed fruit juices, etc. The process of conversion of sugar into alcohol is known as fermentation. Louis Pasteur discovered fermentation in 1857. COMMERCIAL USE

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The source of medicines is microorganisms. These medicines kill or stop the growth of the disease-causing microorganisms. Such medicines are called antibiotics. Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made form fungi and bacteria. Antibiotics are even mixed with the feed of livestock and poultry to check microbial infection in animals. They are used to control many plant diseases. VACCINE When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader. The body also remembers how to fight the microbe if it enters again. So, if dead or weakened microbes are introduced in a healthy body, the body fights and kills them by producing suitable antibodies. The antibodies remain in the body and we are protected form the disease-causing microbes. This is how a vaccine works. Several diseases including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccine. MEDICINAL USE

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INCREASING SOIL FERTILITY & CLEANING THE ENVIRONMENT Some bacteria and blue green algae are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility. These microbes are commonly called biological nitrogen fixers. We often see large amounts of dead organic matter lying on the ground. We find that they disappear after some time . This is because the microorganisms decompose dead organic waste converting them into simple substances. These substances are again used by some plants and animals. Thus, microorganisms can be used to degrade the harmful and smelly substances and thereby cleaning the environment.

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HARMFUL MICROORGANISMS Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease causing microorganisms are called pathogens. Some microorganisms spoil food, clothing and leather.

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DISEASE CAUSING MICROORGANISMS HUMANS Pathogens enter our body through the air we breathe, the water we drink or the food we eat. They can get transmitted by direct contact with an infected person or carried through an animal. Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis. CAUTION: we should keep a handkerchief on the nose and mouth while sneezing. It is better to keep a distance from infected people. Female Anopheles mosquito carries the parasite of malaria. Female Aedes mosquito is the carrier of dengue virus.

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ANIMALS Several microorganisms not only cause diseases in humans and plants but also in other animals. For example, anthrax is a dangerous human and cattle disease caused by a bacterium. Foot and mouth disease of cattle is caused by a virus. PLANTS Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others. The diseases reduce the yield of crops. They can be controlled by the use of certain chemicals which kill the microbes.

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FOOD POISONING Food poisoning could be due to the consumption of food spoilt by some microorganisms. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death. So, it is very important that we preserve food to prevent it from being spoilt. PRESERVATION CHEMICAL METHOD Salts and edible oils are the common chemicals generally used to check the growth of microorganisms. Therefore they are called preservatives. We add salt or acid preservatives to pickles to prevent the attack of microbes. Sodium benzoate and sodium metabisulphite are common preservatives. These are also used in the jams and squashes to check their spoilage.

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COMMON SALT Common salt has been used to preserve meat and fish for ages. Meat and fish are covered with dry salt to check the growth of bacteria. Salting is also used to preserve amla, raw mangoes, tamarind ,etc. SUGAR Jams, jellies and squashes are preserved by sugar. Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food. OIL AND VINEGAR Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such an environment . Vegetables, fruits, fish and meat are often preserved by this method.

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HEAT AND COLD TREATMENTS Boiling kills many microorganisms. Similarly, we keep our food in the refrigerator. Low temperature inhibits the growth of microbes. Pasteurised milk can be consumed without boiling as it is free from harmful microbes. The milk is heated to about 70°C for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. This process was discovered by Louis Pasteur. It is called pasteurisation. STORAGE AND PACKING These days dry fruits and even vegetables are sold in sealed air tight packets to prevent the attack of microbes.

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Bacterium Rhizobium is involved in the fixation of nitrogen in leguminous plants (pulses). It lives in the root nodules of leguminous plants such as beans and peas with which it has a symbiotic relationship. Sometimes nitrogen gets fixed through the action of lightning. But, we know that the amount of nitrogen in the atmosphere remains constant. NITROGEN FIXATION

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