10 assertion and reason class 8 science chapter microorganisms friends and foe
Answers
Answer:
1. Which of the following is a disease caused by protozoans?
Tuberculosis
Polio
Malaria
Typhoid
Answer: (C) Malaria
Solution:
∙ Protozoans are eukaryotic, unicellular microorganisms. Most of them are free-living, found in soil and fresh water, while some are parasitic and cause diseases in plants and animals. Malaria is caused by the protozoan parasite, Plasmodium.
∙ Tuberculosis (TB) is caused by a type of bacterium called Mycobacterium tuberculosis.
∙ Polio is a highly contagious infectious disease caused by polio virus.
∙ Typhoid fever is an acute infectious illness associated with fever that is most often caused by the Salmonella typhi bacteria.
2. Which of the following diseases is caused by a bacteria?
Chicken pox
Tuberculosis
Dengue
Polio
Answer: (B) Tuberculosis
Solution:
∙ Tuberculosis is an air-borne disease caused by the bacterial species Mycobacterium tuberculosis.
∙ Polio, dengue and chicken pox are viral diseases caused by Picornavirus, Flavivirus and chicken pox virus respectively.
3. Some plants have nitrogen-fixing bacteria in their root nodules. What are these bacteria called?
Blue green algae
Nitrosomonas
Azotobacter
Rhizobium
Answer: (D) Rhizobium
Solution: Leguminous plants like pea have nitrogen-fixing bacteria called Rhizobium in their root nodules. Rhizobium helps in converting atmospheric nitrogen into ammonia that can be utilized by the pea plant for its nutrition. Other bacteria like Nitrosomonas and Azotobacter are free-living soil bacteria that also help in nitrogen fixation.
4. In order to take precautionary steps to control dengue, we must take measures to stop the breeding of:
Aedes mosquito
Fleas
Fire ants
Anopheles mosquito
Answer: (A) Aedes mosquito
Solution: Dengue is caused by a virus and is spread by a species of mosquito called Aedes. The spread of this disease can be prevented by using mosquito nets, repellents and by control of breeding of mosquitoes by not allowing water stagnation in our surroundings.
5. Partial sterilization of a product such as milk at a high temperature is known as:
Pasteurization
Filtration
Pickling
Refrigeration
Answer: (A) Pasteurization
Solution: Pasteurization is a process in which milk is heated to about 70oC 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 and hence is called pasteurization
Answer:
Microorganisms friend and foe :
The primary microorganisms in and on our bodies are protozoa, green growth, organisms, microbes, and infections. Most microorganisms are advantageous, for instance, there are microorganisms in our digestive organ that blend nutrients and permit them to be consumed into the circulatory system. Notwithstanding, a minuscule minority are microorganisms (illness-causing specialists). These microorganisms, frequently called microbes or bugs, are a danger to all living things.
We should investigate bacteria, and viruses.
Bacteria:
You can't get away from microscopic organisms. They are all over the place! Beneficially, they are for the most part innocuous, yet the pathogenic microbes can make you wiped out. They flourish in unhygienic circumstances and can develop rapidly by partitioning fifty, then the two parts develop and afterward partition once more, etc.
Viruses:
Viruses are microorganisms that are so essential (and small) that they are not even cells and are not named living. Infections are simply hereditary material (DNA or RNA) wrapped up inside areas of strength made of protein. They can't get by without anyone else, so they need a host that will empower them to duplicate. An infection will seize a cell in your body and change the directions of the cell so that, rather than doing what it was intended to do, the cell starts to create duplicates of the virus. Eventually, it makes so many that the cell blasts open and deliveries all the infections, which then capture many, a lot more cells. Some infections sleep (become lethargic) while they trust that the right circumstances will go along.
Infections have various shapes - poles, circles, or versatile circles. Some are even molded like a spaceship! Pathogenic infections can be exceptionally hazardous, however, there are a couple of good infections that are not destructive. Analysts and researchers are attempting to find approaches to utilizing these infections to battle bacterial contaminations.
To know more about microorganisms visit the links given below:
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