Read and download free pdf of CBSE Class 12 Biology Microbes In Human Welfare Worksheet Set A. Students and teachers of Class 12 Biology can get free printable Worksheets for Class 12 Biology in PDF format prepared as per the latest syllabus and examination pattern in your schools. Standard 12 students should practice questions and answers given here for Biology in Grade 12 which will help them to improve your knowledge of all important chapters and its topics. Students should also download free pdf of Class 12 Biology Worksheets prepared by school teachers as per the latest NCERT, CBSE, KVS books and syllabus issued this academic year and solve important problems provided here with solutions on daily basis to get more score in school exams and tests
CBSE Class 12 Biology Microbes in Human Welfare (1). CBSE issues sample papers every year for students for class 12 board exams. Students should solve the CBSE issued sample papers to understand the pattern of the question paper which will come in class 12 board exams this year. The sample papers have been provided with marking scheme. It’s always recommended to practice as many CBSE sample papers as possible before the board examinations. Sample papers should be always practiced in examination condition at home or school and the student should show the answers to teachers for checking or compare with the answers provided. Students can download the sample papers in pdf format free and score better marks in examinations. Refer to other links too for latest sample papers.
1 Why does ‘Swiss cheese’ have big holes?
2 Why do we prefer to call secondary waste water treatment as biological treatment?
3 What for Nucleopolyhydro viruses are being used now a days?
4 Which species of Penicillium produces Roquefort cheese?
5 Match the following list of bacteria and their commercially important products: Bacterium Product
(i) Aspergillus niger (a) Lactic acid (ii) Acetobacter aceti (b) Butyric acid (iii) Clostridium butylicum (c) Acetic acid (iv) Lactobacillus (d) Citric acid
6 How do mycorrhizal fungi help the plants harbouring them?
7 What is the chemical nature of biogas. Name an organism which is involved in biogas production?
8 What are biofertilisers? Give two examples.
9 Explain the role of baculoviruses as biological control agents. Mention their importance in organic farming.
Ques. A prokaryotic autotrophic nitrogen fixing symbiont is found in
(a) Alnus (b) Cycas
(c) Cicer (d) Pisum.
Ques. Which one of the following helps in absorption of phosphorus from soil by plants?
(a) Glomus (b) Rhizobium
(c) Frankia (d) Anabaena
Ques. Which one of the following is not a biofertiliser?
(a) Agrobacterium (b) Rhizobium
(c) Nostoc (d) Mycorrhiza
Ques. An organism used as a biofertilizer for raising soybean crop is
(a) Azotobacter (b) Azospirillum
(c) Rhizobium (d) Nostoc.
Ques. Consider the following statements (A–D) about organic farming.
(A) Utilizes genetically modified crops like Bt cotton
(B) Uses only naturally produced inputs like compost
(C) Does not use pesticides and urea
(D) Produces vegetables rich in vitamins and minerals
Which of the above statements are correct?
(a) B, C and D (b) C and D only
(c) B and C only (d) A and B only
Ques. The common nitrogen-fixer in paddy fields is
(a) Rhizobium (b) Azospirillum
(c) Oscillatoria (d) Frankia.
Ques. Which one of the following is not used in organic farming?
(a) Glomus (b) Earthworm
(c) Oscillatoria (d) Snail
Ques. An example of endomycorrhiza is
(a) Nostoc (b) Glomus
(c) Agaricus (d) Rhizobium.
Ques. Nitrogen fixation in root nodules of Alnus is brought about by
(a) Frankia (b) Azorhizobium
(c) Bradyrhizobium (d) Clostridium.
Ques. Which one of the following pairs is not correctly matched?
(a) Streptomyces - Antibiotic
(b) Serratia - Drug addiction
(c) Spirulina - Single cell protein
(d) Rhizobium - Biofertilizer
Ques. A free living nitrogen-fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is
(a) Tolypothrix (b) Chlorella
(c) Nostoc (d) Anabaena.
Ques. Which one of the following plants are used as green manure in crop fields and in sandy soils ?
(a) Crotalaria juncea and Alhagi camelorum
(b) Calotropis procera and Phyllanthus niruri
(c) Saccharum munja and Lantana camara
(d) Dichanthium annulatum and Azolla nilotica
Ques. Which of the following is the pair of biofertilizers?
(a) Azolla and BGA
(b) Nostoc and legume
(c) Rhizobium and grasses
(d) Salmonella and E.coli
Ques. Which aquatic fern is used to increase the yield in paddy crop?
(a) Azolla (b) Salvinia
(c) Marsilea (d) Isoetes
Ques. Which of the following fern is an excellent biofertilizer?
(a) Marsilea (b) Pteridium
(c) Azolla (d) Salvinia
Ques. Due to which of the following organism, yield of rice is increased?
(a) Sesbania (b) Bacillus popilliae
(c) Anabaena (d) Bacillus subtilis
Ques. Which of the following is non-symbiotic biofertilizer?
(a) Anabaena (b) Rhizobium
(c) VAM (d) Azotobacter
Ques. Farmers have reported over 50% higher yields of rice by using which of the following biofertilizer?
(b) legume-Rhizobium symbiosis
(d) Azolla pinnata
Ques. The biofertilizers are
(a) Anabaena and Azolla
(b) cow dung, manure and farmyard waste
(c) quick growing crop ploughed under soil
(d) none of these.
Ques. Which of the following species does not have the ability to fix atmospheric nitrogen?
(a) Azotobactor (b) Anabaena
(c) Nostoc (d) Spirogyra
Ques. Which one of the following statements is correct?
(a) Legumes fix nitrogen only through the specialized bacteria that live in their roots.
(b) Legumes fix nitrogen independently of the specialized bacteria that live in their roots.
(c) Legumes fix nitrogen only through specialized bacteria that live in their leaves.
(d) Legumes are incapable of fixing nitrogen.
Microbes in Human Welfare Questions and Answers
Ques. The immune system of a person is suppressed. In the ELISA test, he was found positive to a pathogen. Which cells of the body are affected by the pathogen?
Ans. Helper T lymphocytes
Ques. What would happen to immune system, if thymus gland is removed from the body of a person?
Ans. Thymus is the primary lymphoid organ. In thymus gland, immature lymphocytes differentiate into antigen-sensitive lymphocytes. If thymus gland is removed from the body of a person, his immune system becomes weak. As a result the person's body becomes prone to infectious diseases.
Ques. If a regular dose of drugs or alcohol is not provided to an addicted person, he shows some withdrawl symptoms. List any four such withdrawal symptoms.
Ans. The withdrawal symptoms are:
a. Anxiety b. Shakiness c. Nausea d. Sweating
Ques. In the metropolitan cities of India, many children are suffering from allergy/asthma. What are the main causes of this problem. Give some symptoms of allergic reactions.
Ans. Allergy is the exaggerated response of the immune system of certain antigens present in the environment. In metropolitan cities life style is responsible in lowering of immunity and sensitivity to allergens. More polluted environment increases the chances of allergy in children. Some symptoms of allergic reactions are sneezing, watery eyes, running nose and difficulty in breathing.
Ques. Life style diseases are increasing alarmingly in India. We are also dealing with large scale malnutrition in the population. Is there any method by which we can address both these problems?
Ans. The answer to address both these problems is called biofortification. This area looks at improving food quality with respect to protein, oil, vitamin, micro nutrient and mineral content. The oils need to be rich in omega 3 fatty acids which are good for heart. Similarly, proteins should have more of lysine and tryptophan (essential amino acids). Many varieties of maize, carrots and spinach have been released which fulfill the above criteria.
Biology in Human Welfare Questions and Answers
Ques. Do you think we, human beings, are able to digest the cellulose present in our foods? Why or why not ?
Ans. We lack cellulase enzyme for digestion due to nonfunctioning of appendix.
Ques. Baculoviruses are the pathogens that attack on plants and also are used for biocontrol. How both antagonistic functions are performed ?
Ans. Baculovirus like Nucleopolyhedral virus are- species specific, narrow spectrum, effective only against insects and arthropods.
Ques. Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river
water is relatively clean?
Ans. Most polluted water : 400 mg/L of secondary effluent (c). A (River water) : 08 mg/L; b (Untreated sewage water) : 20 mg/L.
Ques. The Ministry of Environment and Forests has initiated Ganga Action Plan and Yamuna Action Plan to save these major rivers. How was the target fulfilled ?
Ans. Decreasing pollution, Sewage treatment and utilization of treated water.
Ques. What are the negative impacts of biological control ?
Ans. May develop resistant insect varieties, may be lethal / harmful for human beings.
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