Test: Microorganisms : Friend Or Foe (Medium)

20 Questions MCQ Test Science Class 8 | Test: Microorganisms : Friend Or Foe (Medium)

This mock test of Test: Microorganisms : Friend Or Foe (Medium) for Class 8 helps you for every Class 8 entrance exam. This contains 20 Multiple Choice Questions for Class 8 Test: Microorganisms : Friend Or Foe (Medium) (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Microorganisms : Friend Or Foe (Medium) quiz give you a good mix of easy questions and tough questions. Class 8 students definitely take this Test: Microorganisms : Friend Or Foe (Medium) exercise for a better result in the exam. You can find other Test: Microorganisms : Friend Or Foe (Medium) extra questions, long questions & short questions for Class 8 on EduRev as well by searching above.

Cow dung is appropriately used as

Solution: Cow dung is available in plenty in India. It is used as manure or pattings for fuel. The cow dung solution has antifungal and insecticide properties. The application of cow dung also improves soil salinity and alkalinity. The presence of this manure helps in better nitrogen fixation through rhizobia.


Bt toxin protein crystals present bacterium Bacillus thuringiensis, do not kill the bacteria themselves because

Solution: Soil bacterium Bacillus thruingiensis (Bt) produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles), and dipterans (flies, mosquitoes). Bacillus thuringinesis forms some intracellular protein crystals. These crystals contain a toxic insecticidal protein. The Bt toxin protein exists as an inactive toxin and is converted into an active form due to the alkaline pH of the alimentary canal that solubilities the crystals. The activated toxin binds to the surface of midgut epithelial cells and creates pores which cause cell swelling and lysis and finally cause the death of the insect.


Pathogenicity of bacteria causing tuberculosis and leprosy is due to

Solution: The cell wall structure of Mycobacterium tuberculosis deserves special attention, because it is unique among prokaryotes, and it is a major determinant of virulence for the bacterium. The cell wall complex contains peptidoglycan, but otherwise, it is composed of complex lipids. Over 60% of the mycobacterial cell wall is a lipid. The lipid fraction of MTB's cell wall consists of three major components, mycolic acids, cord factor, and wax-D. Bacteria that cause tuberculosis and leprosy produce a wax (wax D), that repels ordinary laboratory stains and contributes to their pathogenicity.


Which among the following is the most reason for storing green coloured apples at low temperatures?

Solution: When green coloured apples are stored at a low temperature the cellular process in the apples also gets reduced for conserving energy due to which the rate of respiration is reduced and the aging process is slowed down.


The most quickly available source nitrogen to plants are

Solution: The chemical compound ammonium nitrate, the nitrate salt of ammonium. It is a white crystalline solid and is highly soluble in water. It is predominantly used in agriculture as a high-nitrogen fertilizer.


Which one is not correctly matched?

Solution: Smut of pearl millet is caused by Tolyposporium penicillariae, which is an important and widespread disease.

Root-knot is a major nematode disease problem in tobacco worldwide. Four species of root-knot are found on tobacco, including Meloidogyne incognita, Meloidogyne javanica, Meloidogyne Arenaria, Meloidogyne hapla.

The covered smut of barley is caused by the fungus, Ustilago hordei.


State whether the given statement is True or False: Nitrogen Fixation In Leguminous plants increases soil fertility.


Soil fertility can be improved by incorporating crops that add organic matter to the soil, which leads to improved soil structure and promotes healthy, fertile soil. This can be done by growing legumes to fix nitrogen from the air through the process of biological nitrogen fixation. When these plants decompose, they get converted to nitrogenous compounds which increase nutrient content in the soil. The given statement is True.


Additive-stabilizer used in butter is ________________.

Solution: Stabilizing agents are used for a number of functions in foods and the main function is to act as a thickening agent to gel the foods into the required consistency. Most stabilizing and thickening agents are polysaccharides (a kind of carbohydrate) examples of which are starches, gums, or proteins like gelatin.


Typhoid Is caused by


Typhoid is a bacterial disease caused by Salmonella typhi.


Salmonella bacterium causes

Solution: Salmonella infection is usually caused by eating raw or undercooked meat, poultry, eggs, or egg products. The incubation period ranges from several hours to two days. Most salmonella infections can be classified as stomach flu (gastroenteritis).


Trichoderma species are potentially useful as

Solution: Members of the Trichoderma genus are known as imperfect fungi. It is used to treat seeds and soils to eliminate the pathogens such as fungi. These species have long been recognized as biological agents to control plant diseases. The first application of these species was in the 1930s. Since then, Trichoderma species became a popular biological agent to protect crops against plant pathogens all over the world.


Name the single-celled microorganism which found in the glacier to deserts and hot spring.


Bacteria are the single-celled microorganism which found in the glacier to deserts and hot spring.


Following are a few characters of a disordering human body.

(i) Inflammation of the mucous membrane of the nasal passage

(ii) Watery Secretion By Mucous Glands

(iii) Continuous Sneezing

(iv) Eye Watering

(v) The rise in body temperature

Identify the disorder from the choices given below.

Solution: Rhinitis is a viral infection that results in the inflammation of the mucous membrane of the nose of an individual. It often causes the release of watery secretions from the mucous glands, continuous sneezing, eye-watering, and a rise in the body temperature.


Which of the following contains preservatives in it?

Solution: Processed, packaged foods like some crackers, cereals, breads, snacks, ready-to-eat meals, cheese, yogurt, deli meats, sauces and soups may contain preservatives.


Penicillin is bacteriolytic because

Solution: Penicillin is a group of antibiotics derived from Penicillium fungi. Penicillin inhibits the formation of peptidoglycan cross-links in the bacterial cell wall thereby inhibiting cell wall formation. So, the correct answer is option C.


Antibiotics are obtained from

Solution: Antibiotics are chemicals that kill or inhibit the growth of bacteria and are used to treat bacterial infections. They are produced in nature by soil bacteria and fungi.


The carnivorous fish Gambusia, introduced in the lakes, ponds, etc., control a deadly disease in India, feeds on the larvae of

Solution: Gambusia affinis, a native of coastal waters of the United States from New Jersey southwards, introduced into India about 40 years ago from Italy and Thailand.


Most common preservative?

Solution: Sodium benzoate and sodium metabisulphite are common preservatives. These are also used in the jams and squashes to check their spoilage.



Solution: Cholera is an infectious disease that causes severe watery diarrhea, which can lead to dehydration and even death if untreated. It is caused by eating food or drinking water contaminated with a bacterium called Vibrio cholerae.


Name the multicellular, heterotrophic microorganisms found in colonies.

Solution: Microorganisms may be single-celled like bacteria, some algae, and protozoa, or multicellulars 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.