Assertion Reason Biology Chapter 8 Microbes in Human Welfare

Questions of Assertion Reason Chapter 8 Microbes in Human Welfare biology CBSE Class 12 are very simple to understand as this chapter deals with Microbes in Human Welfare. To solve assertion reason type questions of biology, deeper understanding of concept about Microbes in Human Welfare is required. In order to help the student in solving Assertion Reason type of questions, detailed process is explained.

How to solve Assertion Reason Type Questions?
In Assertion-Reason type of question, two statements are given, first is Assertion and second is called Reason. Student must have to think critically about both the statements in Assertion Reason Questions, since it combines multiple choice questions and true/false type of questions which requires a higher level of understanding.

How many types are there of Assertion Reason Type Questions?
Assertion-Reason type of questions can be asked either with four MCQ options or with five MCQ options. First four options are same in both the cases only one more options is being provided i.e. last one. One extra option increases the difficulty level of the questions.

In assertion reason type of questions, all 4 or 5 options are same for each question, which are as:

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
(e) Both Assertion and Reason are false.

Then a question haunts in every student’s mind, which option is correct and when?
This can be understood clearly with the following table:

Assertion (A)Reason (R)MCQ Options (Fixed for all questions)
If TrueTrue(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
If TrueTrue(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
If TrueFalse(c) Assertion (A) is true but reason (R) is false.
If FalseTrue(d) Assertion (A) is false but reason (R) is true.
If FalseFalse(e) Both Assertion and Reason are false.

Now, lets practice some Assertion Reason Questions of Biology : Chapter 8 Microbes in Human Welfare.

Read instructions carefully before answering the questions.

For question given below, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

(a) Both A and R are true and R is correct explanation of the assertion.
(b) Both A and R are true but R is not the correct explanation of the assertion.
(c) A is true but R is false.
(d) A is false but R is true.

Assertion: Besides curdling of milk, LAB also improve its nutritional quality by increasing vitamin-B12.
Reason: LAB, when present in human stomach, check disease causing microbes.

Ans.1. (b)
Curd is more nutritious than milk as it contains a number of organic acids and vitamins including B12. LAB present in curd also checks growth of disease causing microbes in stomach and other parts of digestive tract.

Assertion: Streptococcus thermophilus increases nutritional value of milk.
Reason: Milk has lesser vitamin content than curd and yoghurt.

Ans.2. (a)
Microbes have been used for long time in production of dairy products like curd, yoghurt, cheese, etc. Yoghurt is produced by curdling milk with the help of Streptococcus thermophilus and Lactobacillus bulgaricus. Yoghurt has higher nutritional value than milk thus, it can be said that Streptococcus thermophilus increases nutritional value of milk.

Assertion: Vitamins B2 is found in cereals, green vegetables, brewer’s yeast, egg white, milk and liver.
Reason: It can be commercially produced by some yeasts.

Ans.3. (b)
Besides cereals, green vegetables, brewer’s yeast, egg white, vitamin B2 is also produced by intestinal bacteria. The vitamin was first obtained in 1938 using wild strain of mould Ashbhya gossypii. Vitamin B2 is essential for normal growth and reproduction in a number of laboratory animals.

Assertion: Lichen is important for chemical industries.
Reason: Litmus and Orcein are formed from lichens.

Ans.4. (a)
Litmus is an important and widely used dye in chemical laboratories as an acid-base indicator. It is obtained from Rocella montaignei. Orcein, a biological stain, is obtained from Rocella tinctoria.

Assertion: Yeasts such as Saccharomyces cerevisiae are used in baking industry.
Reason: Carbon dioxide produced during fermentation causes bread dough to rise by thermal expansion.

Ans.5. (a)
Yeast is a fermentation agent. It is a known fact that yeast raises bread dough to rise and hence, Yeast is also used to increase the volume, making the dough porous and the product soft. It is the yeast that helps the dough to rise.

Assertion: Rennet and fruit extract of Withania somnifera have antagonistic functions.
Reason: Rennet is obtained from calf’s liver and is used for curdling of milk.

Ans.6. (d)
Rennet is obtained from calf ‘s stomach and is a commercially available form of enzyme rennin. Rennet is used from curdling of milk to initiate the process of cheese formation. The same function can be carried out with the help of fruit extract of Withania somnifera. Thus, rennet and fruit extract of Withania somnifera have similar functions and are not antagonistic.

Assertion: After 24 hours, toddy becomes unpalatable.
Reason: The fermentation of toddy is continued by naturally occurring yeasts.

Ans.7. (a)
Toddy is a traditional drink of some parts of South India which is made by fermentation of sap of palms. Toddy left for few hours undergoes fermentation with the help of naturally occurring yeast to form beverage containing about 6% alcohol. But after about 24 hours, toddy becomes unpalatable because fermentation is carried on. At this time, it can be used for production of vinegar.

Assertion: Beer and wine are called soft liquors while gin, rum, etc. are hard liquors.
Reason: Beer and wine are made without distillation.

Ans.8. (b)
Beer, wine, gin, rum, vodka, etc. are fermentation products but beer and wine are formed without distillation. However, distillation of fermented broth is carried out in case rum, gin, etc. Distillation increases the alcohol concentration of the beverage. Thus, gin with 40% alcohol, rum with 40% alcohol and brandy with 60-70% alcohol are more alcoholic than beer (3-6% alcohol) and wine (9-12% alcohol).

Assertion: Griseofulvin extracted from P. griseofulvum is used for ringworm treatment.
Reason: Trichophyton, Epidermophyton, etc. cannot grow well in presence of Penicillium griseofulvum.

Ans.9. (a)
Antibiotics are chemical substances produced by some microbes which in small concentration can kill or retard the growth of harmful microbes without adversely affecting the host. Griseofulvin is an antibiotic produced by Penicillum griseofulvum and is antifungal in nature, especially effective against ringworm. Ringworm is caused by dermatophytic fungi like Epidermophyton, Trichophyton, Microsporium, etc. which cannot grow in presence of P. griseofulvum because of the antagonistic effect of antibiotic griseofulvin secreted by it.

Assertion: Acetic acid production involves both aerobic and anaerobic processes.
Reason: Production of alcohol from glucose is an aerobic process and production of acetic acid from alcohol is an anaerobic process.

Ans.10. (c)
Assertion is true but Reason is false.

Assertion: An organ transplant patient if not provided with cyclosporin A may reject the transplanted organ.
Reason: Cyclosporin A inhibits activation of T-cells and interferes with destruction of non-self cells.

Ans.11. (a)
Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Assertion: The kneaded flour shows leavening, when yeast is added to it.
Reason: Enzymes secreted by yeast cause leavening.

Ans.12. (a)
A small quantity of yeast is added to wheat flour and is kneaded. The kneaded flour is kept at a warm temperature for few hours. It swell up. This phenomenon is called leavening. Leavening is caused by secretion of three types of enzymes by yeast. These are amylase, maltase and zymase.

Assertion: Saccharomyces species are utilized for making alcoholic beverages.
Reason: Yeast has an enzyme, zymase responsible for fermentations.

Ans.13. (a)
Sacharomyces cerevisiae produces an enzyme called zymase which can cause fermentation to produce alcohol.

Assertion: Secondary treatment of sewage is also called biological treatment while primary treatment is called physical treatment.
Reason: Primary sewage treatment depends only upon sedimentation properties of materials present in sewage and filteration.

Ans.14. (a)
Sewage treatment is divided into primary treatment and secondary treatment. Primary treatment involves filtration of the sewage and then sedimentation of the debris present on filtrate. No microbes are used. The sediment of primary treatment, called primary sludge, is treated by aerobic microbes and then by anaerobic microbes to reduce its organic components during secondary treatment. Secondary treatment involves microbes, thus it is also called biological treatment.

Assertion: Energy value of biogas is lower than that of organic matter.
Reason: Biogas minimises the chances of spread of fecal pathogens.

Ans.15. (b)
Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

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