E. Long Answer Type Questions 1. (a) How do microorganisms help in cleaning of environment? (b) Discuss the role of microorganisms in increasing the soil fertility. 2. Describe different methods of spreading communicable diseases. 3. What is biological nitrogen fixation? Give examples of microbes associated with this fixation. 4. What is the contribution of Louis Pasteur in the study of microorganisms ?
Answers
Answer:
1)a Microorganisms help in cleaning up the environment. They decompose dead and decaying matter from plants and animals, convert them into simpler substances which are later used up by other plants and animals. Thus, they are used to breakdown harmful substances
b)The soil is home to many animals. Microorganism like some algae , bacteria fungi are present in the soil. Bacteria and fungi present in the soil feed on dead remains of animals and plants and forms humas (which is rich in nutrients and makes the soil fertile). Thus in this way microorganisms make the soil fertile
They increase soil fertility by incorporating air, minerals and nitrogenous compounds. They contribute in increasing plant growth by providing essential elements, minerals that plants cannot utilize by their Owen. Microorganisms decompose organic matter to simpler form that can be easily uptake by plant
2.Some ways in which communicable diseases spread are by: Physical contact with an infected person, e.g. through touch (staphylococcus), sexual contact (gonorrhoea, HIV), faecal/oral transmission (hepatitis A), or droplet (influenza) Contact with a contaminated surfaces or objects (Norovirus), food (salmonella, E)
- Germs can spread from person to person through:
- the air as droplets or aerosol particles.
- faecal-oral spread.
- blood or other body fluids.
- skin or mucous membrane contact.
- sexual contact
3.
1. Nitrogen Fixation: It is the process by which nitrogen gas in the atmosphere is converted into compounds of nitrogen. It take place in three ways:
a) Biological Nitrogen Fixation: It is the conversion of atmospheric nitrogen into compound of nitrogen by the action of certain living organisms, like rhizobium bacteria which reside in the root nodules of leguminous plants.
b) Atmospheric Nitrogen Fixation: During lightning, atmospheric nitrogen combines with oxygen to form nitrogen oxides. These oxides react with rain water and are carried to the earth in the form of nitrous and citric acids. This is called atmospheric nitrogen fixation. Minerals in the soil can convert nitric acid to soluble nitrates, which can be used by plants.
c) Industrial Fixation: Fertilisers consisting of nitrogen in the form of ammonia or urea or ammonium nitrate are produce to be added to the soil. This is know as industrial fixation of nitrogen.
Examples of this type of nitrogen-fixing bacteria include species of Azotobacter, Bacillus, Clostridium, and Klebsiella. As previously noted, these organisms must find their own source of energy, typically by oxidizing organic molecules released by other organisms or from decomposition
4.During the mid- to late 19th century Pasteur demonstrated that microorganisms cause disease and discovered how to make vaccines from weakened, or attenuated, microbes. He developed the earliest vaccines against fowl cholera, anthrax, and rabies
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