Samacheer Kalvi 8th Science Solutions Chapter 16 Pdf
Tamilnadu Board Samacheer Kalvi 8th Science Solutions Chapter 16: Tamilnadu State Board Solution Class 8 Science Chapter 16 – Microorganisms.
Samacheer Kalvi 8th Science Solutions Chapter 16: Overview
|
Board |
Samacheer Kalvi |
| Class |
8 |
|
Subject |
Science |
| Chapter |
16 |
|
Chapter Name |
Microorganisms |
Samacheer Kalvi 8th Science Solutions Chapter 16 Pdf
(I) Choose the best answer .
(1) Microorganisms are measured in micron.
a ) cm
b) mm
c) micron
d) meter
(2) Virus shows both living and nonliving characteristics .
(a) Protozoa
b) Virus
c) Bacteria
d) Fungi
(3) Bacteria is a prokaryotic microorganisms.
a) Virus
b) Algae
c) Fungi
d) Bacteria
(4) Based on shape , the bacteria are classified into four types .
a) two
b) three
c) four
d) five
(5) Common cold in human is caused by influenza.
a) plasmodium
b) influenza
c) vibrio cholera
d) aphthovirus
(II ) Fill in the blanks.
1) Penicillin is prepared from a mould called penicillium.
2) Prions are the infectious protein particles.
3) The infecting virus particle found outside the host cell is Virion .
4) Microorganism can be seen with the help of a microscope.
5 ) Bacteria, which has a flagellum at one end is classified as monotrichous .
(III ) State true or false. If false, correct the statement.
1 ) Disease causing microorganisms are called pathogens.
This statement is true .
2 ) Female anopheles mosquito is a carrier of dengue virus.
This statement is false.
Explanation:
Female anopheles mosquito is not a carrier of dengue virus but rather it is a carrier of malaria.
3 ) Chicken pox is a communicable disease.
This statement is true.
4 ) Citrus canker is transmitted by insects.
This statement is false.
Explanation :
Citrus canker is not transmitted by insects but rather it is transmitted by air and water.
5 ) Yeast is used in the large scale production of alcohol.
This statement is true.
(IV ) Match the following.
| Nitrogen fixing bacteria | Vaccine |
| Tuberculosis | Prion |
| Kuru | Lactobacillus acidophilus |
| Probiotics | Bacteria |
| Edward Jenner | Rhizobium |
Answer
| Nitrogen fixing bacteria | Rhizobium |
| Tuberculosis | Bacteria |
| Kuru | Prion |
| Probiotics | Lactobacillus acidophilus |
| Edward Jenner | Vaccine |
( V) Answer the following questions.
Mark the correct one as :
1 ) Assertion : Malaria is caused by Protozoa.
Reason : The disease is transmitted by mosquito.
Answer – a ) If both assertion and reason are true and reason is the correct explanation of assertion.
2 ) Assertion : Algae are heterotrophic.
Reason : They do not have chlorophyll.
Answer – d) If both assertion and reason are false .
Explanation :
Algae are not heterotrophic but rather, they are autotrophic. It is not correct to say that, they do not have chlorophyll but rather, all the algae contains chlorophyll.
(VI) Answer very briefly.
1 ) Write the name of any nitrogen fixing bacteria.
Ans : Rhizobium
Explanation:
Rhizobium is mainly a bacteria that are present in soil and they play an essential role in fixing nitrogen in the roots of leguminous plants.
2 ) Name the bacteria used in the production of vinegar.
Ans : Acetobacter aceti
Explanation :
Acetobacter aceti is a bacterium that plays an important role in the production of vinegar.
3 ) Write the names of any three protozoans.
The names of any three protozoans are as follows:
- Fungi
- Paramecium
- Amoeba
4 ) Who discovered penicillin?
Ans : Alexander Fleming
Explanation :
Penicillin was discovered by Alexander Fleming in the year 1928. Penicillin refers to a group of antibiotics that are mainly used for the purpose of treating bacterial infections.
5 ) Which diseases can be prevented by vaccination?
The diseases that can be prevented by vaccination are as follows:
- Mumps
- Polio
- Rubella
- Small pox
- Tuberculosis
- Tetanus
- Measles
(VII) Answer briefly .
1 ) Write the four types of bacteria, based on their shape.
Bacteria can be categorized on the basis of the shape of their cells. They are as follows
- Bacilli is a bacteria that depicts a rod shape. Bacillus anthracis is one such example.
- Spirilla is a bacterium that portrays a spiral shape. Helicobacter pylori is one of the most relevant example.
- Cocci is a bacteria that depicts a spiral or ball shape. They can stick collectively in pair and they also possess the ability to form into a chain or they can appear in bunches.
- Vibro is a bacterium that manifests a comma shape. Vibro cholera is one of the perfect example.
2) What are antibiotics?
Antibiotics mainly refers to a substance that tends to be poisonous for other organisms and these substance are produced by living organisms. Penicillin was discovered by Alexander Fleming in the year 1928. Penicillin refers to a group of antibiotics that are mainly used for the purpose of treating bacterial infections.
3) What are pathogens ?
There are certain microorganisms that poses harmful effects to plants, animals and humans. Pathogens mainly refers to those bacteria that are responsible for causing diseases. They cause diseases by entering into the body through any kind of cuts or wounds in the skin,they can also enter through the mouth or nose. Virus causing flu are mainly transmitted through air. When a patient sneezes numerous viruses are contained in those droplets that get’s spread through the air and these viruses then enters into the body of another person when he inhales the air.
4 ) How disease causing microorganisms enter into human beings?
Pathogens mainly refers to those bacteria that are responsible for causing diseases. They cause diseases by entering into the body through any kind of cuts or wounds in the skin, they can also enter through the mouth or nose. Virus causing flu are mainly transmitted through air. When a patient sneezes numerous viruses are contained in those droplets that get’s spread through the air and these viruses then enters into the body of another person when he inhales the air.
5 ) Why microorganisms are essential for agriculture?
Natural fertilizer
As microorganisms acts upon the degradable waste ,due to this reason they are known as decomposers. During the procedure, there is a release of nitrous and other inorganic nutrients into the soil, thus enhancing the fertility of the soil. This compost is termed as natural fertilizer.
Nitrogen fixation
Rhizobium is mainly a bacteria that are present in soil and they play an essential role in fixing nitrogen in the roots of leguminous plants , which ultimately facilitates the growth of plants.
Bio – control agents
Microbes play an important role in protecting the crops from the attack of insects and pests. Some of them are as follows:
- Bacillus thuringiensis renders tremendous support in controlling insects.
- Trichoderma contributes in protecting the roots and helps to control plant pathogens.
- Baculoviruses performs an essential function by attacking the insects and other arthropods.
So, these are the several points which clearly depicts the importance of microorganisms in the field of agriculture.
(VIII) Answer in detail.
1 ) Write a short note on bacteria and its structure.
Bacteria are mainly represented as an unicellular prokaryotes and regarded as the first living organisms on the planet earth. Bacteria falls under the category of kingdom Monera. Bacteriology mainly refers to the study of bacteria. 1um to 5um represents the varying size of bacteria. Aerobic bacteria and anaerobic bacteria are mainly the two types of bacteria that are classified on the basis of respiration.
Cell structure of Bacteria
The cell wall refers to an external covering of a bacteria. Nucleoid represents the nuclear material without the presence of nuclear membrane. Plasmid is an extrachromosomal DNA that is contained in the cytoplasm. 70S ribosomes performs an essential function in carrying out the protein synthesis. There is an absence of other cell organelles. Flagella plays an important role in facilitating the movement.
Bacteria can be categorized on the basis of the shape of their cells. They are as follows :
- Bacilli is a bacteria that depicts a rod shape. Bacillus anthracis is one such example.
- Spirilla is a bacterium that portrays a spiral shape. Helicobacter pylori is one of the most relevant example.
- Cocci is a bacteria that depicts a spiral or ball shape . They can stick collectively in pair and they also possess the ability to form into a chain or they can appear in bunches.
- Vibro is a bacterium that manifests a comma shape. Vibro cholera is one of the perfect example.
2 ) How microorganisms are useful in the field of medicine ?
Antibiotics
Antibiotics mainly refers to a substance that tends to be poisonous for other organisms and these substance are produced by living organisms. Penicillin was discovered by Alexander Fleming in the year 1928. Penicillin refers to a group of antibiotics that are mainly used for the purpose of treating bacterial infections. Penicillium chrysogenumrefers to the fungi, from where the antibiotic penicillin was acquired. The antibiotic, streptomycin is acquired from streptomyces bacteria which is primarily used for the purpose of treating several bacterial infections.
Vaccines
The dead or weakend microbes plays an important part in the preparation of vaccines. Smallpox vaccine was first discovered by Edward Jenner. When a patient receives the vaccine, his or her body starts producing antibiotics, which ultimately helps to resist the germs causing diseases. These antibiotics stays within the body and acts as a protective shield against future occurrence of germs. For this reason, vaccination is known as immunization. As for example, MMR vaccine is mainly given for protecting oneself against Measles , Mumps and Rubella. In a similar manner, BCG vaccine is given for protecting oneself against Tuberculosis.
3 ) Write a short note on common human diseases caused by microorganisms.
Human diseases – Tuberculosis
Causative microorganisms-Mycobacterium tuberculosis
Mode of transmission – It is transmitted through air and mucus of a sick person who is infected with the disease.
Symptoms– Coughing in a persistent manner, blood mucus, weight loss, difficulty in breathing.
Preventive measures / Treatment – BCG vaccine is given for preventing oneself fromTuberculosis .
Human diseases – Cholera
Causative microorganisms – Vibrio cholera
Mode of transmission – The common house flies plays a crucial role in transmitting the disease . This disease is also spread through contaminated food and water.
Symptoms – Watery diarrhoea, vomiting and instant dehydration .
Preventive measures/ Treatment – Anticholera vaccine is given for preventing cholera,there should be a proper maintenance of personal hygiene.
Human diseases– Common cold
Causative microorganisms–Influenza
Mode of transmission – This disease is mainly transmitted through air.
Symptoms– Sneezing, runny nose .
Preventive measures/ Treatment – The patient should keep himself socially isolated from other persons.
Human diseases–Rabies
Causative microorganisms–Rhabdo viridae
Mode of transmission– Rabies is usually caused by an animal bite. It is the saliva of the infected animals ,which transmits the virus to the people.
Symptoms– Fever, hallucination, paralysis, difficulty to shallow .
Preventive measures/ Treatment – Anti-rabies vaccine is given for preventing rabies.
Human diseases– Amoebic dysentery
Causative microorganisms– Entamoeba histolytica .
Mode of transmission– This disease is mostly spread through food and water. Flies also performs an essential role in transmitting the disease.
Symptoms–Severe diarrhoea and blood in stool.
Preventive measures/ Treatment – There should be a proper maintenance of personal hygiene and sanitation, Metronidazole antibiotics should be directed in order to prevent this disease.
Human diseases– Malaria
Causative microorganisms– Plasmodium
Mode of transmission– This disease is mainly transmitted through the female anopheles mosquito.
Symptoms– High fever, vomiting ,nausea.
Preventive measures/ Treatment – Quinine and chloroquine should be taken, as they act as an antimalarial drugs. One should always try to use mosquito nets and mosquito repellent, which will ultimately aid in protecting oneself against mosquitoes bites.
4 ) How can we improve the beneficial bacterial count in human beings?
By adopting the following methods, we can improve the beneficial bacterial count in human beings. The methods are as follows :
- One should try to consume foods that are rich in fibre.
- One should also try to eat seasonal fruits and vegetables.
- Plant based diet should be given more preference.
- One should try to include whole grain food in their diet ,which helps in maintaining a good physical condition.
- An ample quantity of fermented food should be taken.
- A whole lot of probiotic foods should be consumed.
- One should always try to avoid foods that contains artificial sweeteners.
5 ) Write a note on probiotics.
Probiotics are live organisms , that plays an important role in keeping our body in a healthy and good condition. Probiotics are mostly found in yoghurt and other fermented milk products. Lactobacillus acidophilus and bifidobacterium bifidum are some of the relevant examples. These bacteria helps in improving our digestive health and reduces the possibility of colon cancer . It can also reduce the absorption of cholesterol and averts diarrheal diseases by strengthening the immune system.
