Microorganisms Friend And Foe - Class 8 Biology - Extra Questions

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 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. Microorganisms like amoeba can live alone, while fungi and bacteria may live in colonies.

A pathogen is a biological infectious agent such as microorganisms which can cause disease.

Examples of pathogens include: bacteria, viruses, fungi etc.

Mycobacterium tuberculosis causes tuberculosis.

Streptococcus pneumoniae causes pneumonia, meningitis.

Vibrio cholerae causes cholera.

Polio, measles, diphtheria, rubella, mumps, tetanus and small pox are some of the diseases that can be prevented by vaccines.

Infectious diseases are caused by microbes, which can move from one person to another in different ways. As these diseases can be communicated from one person to another, therefore they are called communicable diseases.

Treatment of disease is with antibiotics. A typhoid vaccine can prevent about $$50$$% to $$70$$% of cases. The vaccine may be effective for up to seven years. It is recommended for those at high risk or people traveling to areas where the disease is common. Sanitation and hygiene are the critical measures that can be taken to prevent typhoid. Typhoid does not affect animals, so transmission is only from human to human.

• Antibiotics are antimicrobial drugs obtained from other organisms to combat harmful microorganisms. 

  Precautions must be taken while taking antibiotics:
  
• Antibiotics should be taken under the supervision of a well-qualified doctor.
• Course of antibiotics should be completed as prescribed by the doctor.
• Antibiotics should be taken in the right amount and at the right time. 
• Also, excessive consumption of drugs may kill the useful bacteria present in our bodies.

A) Correct option is C 

Nitrogen fixation is the process by which atmospheric inert nitrogen is converted into ammonia or nitrogen oxide. Bacteria are the component of biological nitrogen fixation; free living non-symbiotic soil bacteria carry out nitrogen fixation. It includes aerobic bacteria (Azotobacter spp), anaerobic bacteria (Clostridium spp), photosynthetic bacteria (Rhodospirillum spp), chemosynthetic bacteria (Thiobacillus spp) and blue green algae.

Microorganisms are small organisms that cannot be seen with naked eyes. Major groups of microorganisms are bacteria, viruses, fungi, protozoa, and algae. 

• Bacteria are prokaryotic, unicellular organisms while viruses are acellular. 
• Fungi are the saprophytic microbes that feed on dead organic matter. 
• Protozoans are single-celled eukaryotic mostly aquatic organisms. 
• Algae are chlorophyll-containing photosynthetic eukaryotic single to multiple celled organisms.

If a person consumes food spoiled by some microorganisms, then he suffers from food poisoning because of the release of harmful toxic substance by the microorganisms and it affects the regular metabolism.

No, microorganisms cannot be seen with the naked eye. They are microscopic in nature, hence they are called 'microorganism'. A microscope or a magnifying lens is required to observe them.

(a) Microorganisms are microscopic in size. Human eye is unable to see at such microscopic size. For observing microorganisms, microscope is used.

The living organisms around us which we cannot see with  our naked eyes  are called microorganisms or microbes. Microbes are found in almost everywhere. They can survive under 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.

Explanation:

• A vaccine is a biological preparation that provides active acquired immunity to a particular disease.
• A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened (attenuated) or killed forms of the microbe, its toxins or one of its surface proteins.
• The agent stimulates the body's immune system to recognize the agent as a threat, destroy it and keep a record of it so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters.

Antibiotics kill or stop the growth of disease-causing microorganisms. These days a number of antibiotics are being produced from bacteria and fungi. Streptomycin, tetracycline, and erythromycin are some of the commonly known antibiotics which are made from bacteria. Penicillin is obtained from fungi.

Fermentation is the anaerobic breakdown of glucose by the yeast (Saccharomyces cerevisiae). The glucose in the sugar solution is broken down to alcohol with the evolution of carbon dioxide. Fermentation is essential in many industrial purposes such as the making of alcohol, bread making etc.

Bacteria helps in fixing atmospheric nitrogen and increases the nitrogen available for the plants. Bacteria decomposes the decaying matter and increases the nutrient content. They also help in improving the texture and quality of the soil.

A vaccine is a biological solution prepared by the live but weakened or killed pathogenic microorganism. These vaccines are the antigens or the antibodies and help to generate an immune response and protect the organism on second encounter of the same agent. 

Some of the diseases transmitted by houseflies are typhoid, cholera, dysentery etc. Typhoid and cholera are both bacterial diseases caused by Salmonella typhi and Vibrio cholerae bacteria's respectively.

BCG vaccine has a protective effect against tuberculosis in children.

The three uses of antibiotics are:

• They are used to fight infections
• Certain antibiotics are used as food preservatives, especially fresh meat and fish.
• Some are used to control plant pathogens

The vaccine is a biological preparation in which weak and heat-killed forms of pathogens are used to provide active immunity (stimulate the production of antibodies in the body). These vaccines facilitate long-term protection against disease (antibodies produced in response to the weak pathogens, remain in the body for a long time).

• Microorganisms are very useful in our daily lives as they are used in:
• Food: Fermented food and beverages.
• Medicines: To produce antibiotics, vaccines, hormones etc. 
• Industry: To produce pigments, acids, enzymes, biofertilizers, biopesticides, to degrade harmful substances such as plastic.
• Biotechnology: To produce biofuels.
• Waste treatment: Treatment of domestic and industrial waste.

• In the production of antibiotics: Many microorganisms are used in the production of antibiotics such as Penicillium notatum for Penicillin, Streptomyces griesus for Streptomycin, etc.
• Saccharomyces cerevisiae is used as a nutritional supplement as it is rich in proteins and vitamins.
• Statins, which are used for lowering cholesterol, are obtained from Monascus purpeurus.
• Cyclosporin A, used as an immunosuppressive agent, is obtained from Trichoderma polysporum.
  
• Clostridia are used in cancer treatment to deliver therapeutic proteins to tumors.
• Ergot, a drug obtained from Claviceps purpurea, is used during delivery to assist childbirth.
  

Fungi used in bakeries are yeasts. These are unicellular fungi that respire anaerobically and produce a large amount of carbon dioxide. The release of carbon dioxide makes the dough rise and gives a puffed-up appearance.

TB is spread through the air from one person to another. The bacteria are put into the air when a person with TB disease of the lungs or throat coughs, sneezes, speaks, or sings. People nearby may breathe in these bacteria and become infected.

Antibiotics have greatly improved our capacity to treat deadly diseases such as:
1. Plague
2. Whooping cough (kali khansi)
3. Diphtheria (gal ghotu) and
4. Leprosy (kushtrog)

The disease-causing microorganisms are called pathogens

Pathogens are organisms that cause disease. They are taxonomically diverse and include bacteria, viruses, and unicellular and multicellular eukaryotes.

Microorganisms are not always beneficial can lead to various kinds of damage. This damage can be in terms of the health of humans and animals, crop production, etc. There are various kinds of microorganisms that are known to cause disease in humans and animals. 

Friendly Organisms- Microbes which support human life are known as friendly organisms.
Yeast- Mostly used in food industry. It helps to make bread loaf, wine, and beer.
Lactobacillus- It helps to make curd from milk.
Rhizobium- Fixes and changes atmospheric nitrogen in nitrates and nitrites for plants use. 
Harmful micro-organisms- These kinds of organism that don't help human life  but have adverse effect on them
Malarial parasite- Causes malaria by entering in host bodies.
Bacillus anthracis- Causes a highly infectious disease anthrax. 

Soil contains various kinds of microbes like bacteria, fungi, algae, protozoa, etc. All of these microorganisms play important roles like:
Certain bacteria and blue-green algae have the ability to fix atmospheric nitrogen. This, in turn, enriches the fertility of the soil. Such microorganisms are known as biological nitrogen-fixers. Example - Rhizobium is a symbiotic bacterium that lives in the root nodules of leguminous plants. Rhizobium fixes atmospheric nitrogen into nitrogenous compounds.
The bacteria and fungi present in soil decompose dead organic wastes of plants and animals and convert them into manure. The manure contributes to the humus content of the soil, thereby helping in increasing its fertility.
Not only these, microorganisms that are found in soil are also a part of many biogeochemical cycles that would not take place in their absence. 
The above points explain the fact that how important microbes are and if they are destroyed its effect can be irreversible. 

The oil poured on the pickles forms a layer of protection between air and pickle from the bacteria present in the air. This increases the shelf life of the pickle and don't let the bacteria deteriorate the quality of pickle.

Milk is pasteurised in order to kill any kind of harmful microorganism present in it and to increase its shelf life. Pasteurisation is a process in which the milk is heated to a certain temperature for a fixed period of time and then is quickly cooled. For example, it may be heated at $$80^{\circ} C$$ for 15 minutes and then immediately cooled. This helps to kill any kind of microorganism which is present in milk. 

Polio is transmitted by contaminated food and water. This disease mainly affects motor neurons within the spinal cord, brain stem, or motor cortex and causes muscle paralysis.

Pathogens are micro-organisms which cause disease.

(b) Food poisoning : Micro organism through contaminated food
Symptoms: uneasyness, vomiting.
Cause: micro organism produce a poisonous substance in contaminated food which makes the food poisonous.
Precautions: Avoid stale, improperly stored  food or food that is prepared in unhygienic conditions .
Treatment: Taking advice from a doctor and consuming medication in time. 

A refrigerator is used in almost every home because it prevents the spoilage of food. The refrigerator provides an optimum environment for the storage of vegetables, fruits, cooked and uncooked food. If an optimum temperature is not provided, it can lead to the growth of bacteria and fungi thus leading to spoilage of food. 

Nitrogen cycle helps to maintain the level of nitrogen in the atmosphere lightning nitrogen in the atmosphere combines with oxygen and forms nitric oxide. This nitric oxide combines with oxygen again to form nitrogen dioxide nitrogen dioxide in the presence of oxygen dissolves in rainwater and reaches earth as nitric acid. this nitric acid combines with compounds present in earth and changes them to nitrates. plants absorb this nitrates easily through plant products, nitrogen reacts animals also when plants and animals decay nitrogen and reaches the atmosphere this process goes on continuously. So the amount of nitrogen is kept constant.

There is a possibility of food poisoning if we eat stale food because there are chances that it can be infested by microorganisms. Bacteria and fungi can infect the foods which are stored for longer durations of time. For example, the greenish powdery substance which is seen on stale bread is an example of fungus infection. 

Vaccine acts as an antigen and stimulates the body to produce antibodies for that particular disease. A vaccine consists of a live weak form of the pathogen or a killed form or a certain chemical substance, that triggers the body to form antibodies against it.

Pulse Polio: This is a mass immunization programme to eradicate poliomyelitis from India. This programme was launched in 1995-96. This programme has been undertaken with active cooperation from government agencies, NGOs, UNICEF, and CDC.
Key Objectives of Pulse Polio:

• Not a single child should be missed.
• High level of surveillance.
•  Reporting of any new case within 14 days.

Polio booths are settled throughout the country to cover all the children below 5 years of age. Volunteers are hired to administer the polio vaccine.
OPV (Oral Polio Vaccine): OPV is an attenuated vaccine. It is produced by the passage of the virus through non-human cells at a sub-physiological temperature. This produces spontaneous mutation in the viral genome.
A single vial of OPV usually contains 10-20 doses.
On $$27^{th}$$ March 2014, WHO declared India a polio-free nation as no new case was reported in the last 3 years.

Antibiotics have created a revolution in treatment of diseases. Many infectious diseases that were incurable earlier can now be treated with antibiotics. Antibiotics have helped in saving millions of lives. 

Answer:

$$\textbf{Explanation:}$$

Communicable	Non-communicable
It is a type of disease that can be transferred from one person to another.	It is a type of disease that cannot be transmitted from one person to another.
It is mainly caused by bacteria and viruses.	It is mainly caused by allergies, malnutrition, abnormalities in cell proliferation, etc.
It is acute as it develops immediately such as AIDS, Typhoid, Malaria, etc.	It is chronic as it develops over a long period of time and lasts for long such as allergies, diabetes, heart disease, etc.

Communicable disease

• Fermentation is the chemical breakdown of a substance by bacteria, yeast or other microorganisms.
• Maida is used in making bread and other bakery products.
• The main ingredient used in making bread is Baker's yeast.
• Yeast is added for preparing the dough.
• Yeast gets activated in the presence of sugar and thus helps in fermentation.
• It contains the following enzymes:-

1) Amylase - changes a small amount of starch into maltose.