Chapter 2 std 8 Microorganisms 1.pptx

the chapter is about microorganisms of eighth std.

1. Organisms that are so small that they can only be seen through a microscope are called microorganisms or microbes.

2. Bacteria Algae Protozoa V irus Fungi TYPES OF MICROORGANISMS

3. Bacteria are found in three different shapes: rod shaped , called bacilli Spherical , called cocci Spiral , called spirilla

4. CHARACTERISTICS OF ALGAE: Algae are eukaryotic organisms Mostly photosynthetic They are almost marine , very few are freshwater. Algae can be unicellular or multicellular. Algae reproduce either by vegetative , asexual or sexual methods.

5. Characteristics of protozoa: Protozoa are unicellular Organisms that have animal like characteristics. They are eukaryotic microorganisms. They can move from place to place. Some protozoa live in fresh or salty water while others live in soil.

6. Characteristics of fungi: Fungi are plant like organisms that do not contain chlorophyll. They may be unicellular or multicellular. They grow best in dark , warm and moist places.

7. Characteristics of viruses: Viruses can replicate only by infecting a host cell. They cannot reproduce on their own. They infect a wide variety of organisms , including both eukaryotes and prokaryotes.

8. In food and beverage industry • Lactobacillus is a bacterium that sours milk and is used to prepare curd from milk. • Fungi like mushrooms and morels are edible and are rich source of protein. • Yeast is used in preparing food items like bread and cakes. (Activity-2.3 Dough making using yeast and flour) • Yeast is also used in breweries for making alcohol, wines and acetic acid (commercial use) by the process of fermentation (conversion of sugar into alcohol). Yeast is grown on natural sugars present in grains like barley, wheat, rice, crushed fruit juices, etc. (Activity-2.4 Alcohol preparation using sugar solution and yeast) Louis Pasteur discovered fermentation in 1857 Beneficial Microorganisms

9. • Some bacteria ( Rhizobium ) and blue green algae ( Nostoc ) live in the root nodules of plants such as gram, pea (leguminous plants) etc. These bacteria absorb the nitrogen from the atmosphere and convert it into nitrate which serves as natural fertilizers for plants, hence, enhancing soil fertility. • These microbes are commonly called as biological nitrogen fixers. In agriculture

10. The alcohol as sugar has been converted into alcohol by yeast. This process of conversion of sugar into alcohol is known as FERMENTATION .

11. • The microorganisms decompose dead organic waste of plants and animals converting them into simple substances. These substances are again used by other plants and animals. • Thus, microorganisms can be used to degrade the harmful and smelly substances and thereby clean up the environment. • The plant waste can be converted into manure by the action of microbes. The nutrients released in the process can be used by the plants again. (Activity-2.5 Making manure using plant waste, fruit and vegetable peels vs. plastic waste, e-waste) In cleaning the environment

12. • 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 from the disease-causing microbes. This is how a vaccine works. • Diseases like cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination. In making medicines - vaccines

13. • Antibiotics are medicines which kill or stop the growth of the disease- causing microorganisms. • A number of antibiotics are being produced from bacteria and fungi. Ex: Streptomycin, tetracycline, erythromycin • Antibiotics are mixed with the feed of livestock and poultry to check microbial infection in animals. • They are also used to control many plant diseases. • Antibiotics are not effective against cold and flu as these are caused by viruses. Note: Antibiotics should be taken only on the advice of a qualified doctor and the prescribed course should be completed. In making medicines-antibiotics

14. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens. Harmful microorganisms In Humans • Pathogens enter our body through the air we breathe, the water we drink or food we eat. • They can also 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. Ex: common cold, chicken pox, tuberculosis.

15. SOME COMMON HUMAN DISEASES CAUSED BY MICROORGANISMS

16. [1] Anthrax Host: Humans, cattle Pathogen: bacteria (Bacillus . anthracis ) [1] Foot and mouth disease Host: cattle Pathogen: virus Foot-and-mouth disease virus (FMDV) In Animals

17. • Microorganisms cause diseases in plants like wheat, rice, potato, orange, sugarcane, apple and others. • The diseases reduce the yield of crops. • They can be controlled by the use of certain chemicals which kill the microbes. In Plants

18. • Microorganisms spoil our food. • Spoiled food emits bad smell and has a bad taste and colour change. • Spoiling of food is a chemical reaction • Food poisoning could be due to the consumption of food spoilt by some microorganisms. • Microorganisms that grow on food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death. food poisoning

19. Food preservation • Processing of food to prevent their spoilage and to retain their nutritive value for longer period is called food preservation. • Preservatives: The common chemicals generally used to prevent the growth of microorganisms. Ex: salt, sugar, edible oil, acids, etc. • Food can be preserved using many methods: 1. Chemical method Standard preservatives (recognized safe by national food agencies) Salt Sugar Oil and Vinegar 2. Heat and cold treatments Pasteurization 3. Storage and packing

20. Pasteurised milk can be consumed without boiling as it is free from harmful microbes. Milk is heated to about 70°C for 15 to 30 seconds and then suddenly chilled and stored. This process prevents the growth of microbes. Pasteurisation Discovery: Louis Pasteur - Pasteurisation .

21. • Rhizobium is involved in the fixation of nitrogen in leguminous plants. It lives in the root nodules of leguminous plants such as beans and peas, with which it has a symbiotic relationship. • Nitrogen also gets fixed through the action of lightning. • The amount of nitrogen in the atmosphere remains constant. • Our atmosphere has 78% nitrogen gas. Nitrogen Fixation

22. NITROGEN CYCLE

23. Mindmap

24. Thankyou