Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

Read the following and answer any four questions from (i) to (v) given below:
Green manuring is the fanning practice where a leguminous plant which has derived enough benefits from its association with appropriate species of Rhizobium, is ploughed into the field soil and then a non-legume is sown and allowed to get benefitted from the already present nitrogen fixer. Some legumes, such as, Crotolaria juncea, Sesbania rostrata, Lencaena leucocephala, etc. are used as green manure. Rhizobia, that fix atmospheric nitrogen in the form of nitrate, live in the roots ofleguminous plants. These nutrients are used by non-leguminous plants through the practice of green manuring.

1. Green manures mainly provide nutrient enriched in:

1. Magnesium.
2. Sulphur.
3. Nitrogen.
4. Both (a) and (b).

2. Which of the following plants is used as green manure in crop fields?

1. Saccharum.
2. Dichanthium.
3. Phyllonthus.
4. Crotolaria.

3. Green manure plants belong to the Family:

1. Lamiaceae.
2. Papilionaceae.
3. Liliaceae.
4. Poaceae.

4. Due to excess use of chemical fertilisers rich in nitrate, ________ disease occurred in children.

1. Jaundice.
2. Septicemia.
3. Methemoglobinemia.
4. Botulism.

5.  A green manure is:

1. Rice.
2. Maize.
3. Sorghum.
4. Sesbania.

Explain with diagram - Hershey and Chase experiment.###On the basis of experimental proof explain the diagram that DNA is genetic material.###How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?

Read the following and answer any four questions from (i) to (v) given below:
IUCN maintains a Red Data Book or Red List which is a catalogue of taxa facing risk of extinction. The IUCN Red List (2004) documents the extinction of 784 species in the last 500 years. Some examples of recent extinctions include the dodo, quagga, thylacine and Steller's sea cow. The last twenty years alone have witnessed the disappearance of 27 species. Red List has eight categories of species.

1. Dodo, an extinct taxon, belongs to which country?

1. Mauritius
2. Africa
3. Australia
4. Russia

2. To which of the following categories of IUCN, Berberis nilghiriensis belongs?

1. Extinct.
2. Extinct in wild.
3. Endangered.
4. Critically endangered.

3. Steller's sea cow and passenger pigeon became extinct due to:

1. Alien species invasion.
2. Over-exploitation.
3. Coextinctions.
4. Intensive agriculture.

4. Bali, Javan and Caspian are:

1. Species of tiger.
2. Species of cheetah.
3. Subspecies of cheetah.
4. Subspecies of tiger.

5. Select the correct term for the following definitions (i, ii, iii, iv).

• The taxon is liable to become extinct if not allowed to realise its full biotic potential by providing protection from exotic species/ human exploitation/habitat deterioration/depletion of food.
• The taxon has been completely eliminated or died out from earth, e.g., Dodo.
• The taxon is facing a high risk of extinction in the wild in the near future due to decrease in its habitat, excessive predation or poaching.
• They are species with naturally small populations, either localised or thinly scattered, which are always at risk from pests/ pathogens/ predators/ exotic species.

	(i)	(ii)	(iii)	(iv)
(a)	Threatened	Extinct	Endangered	Rare
(b)	Endangered	Extinct	Threatened	Rare
(c)	Extinct	Rare	Threatened	Endangered
(d)	Threatened	Extinct	Rare	Endangered

Read the following and answer any four questions from S(i) to S(v) given below:

Rajat is a student of biotechnology. His professor tells him that for transformation with recombinant DNA the bacterial cells must be made capable of taking up DNA as DNA do not pass through membrane. While doing experiment in the lab, Rajat noticed that bacterial cells were not taking up the foreign DNA even after treating it with sodium ion. He asked his professor, the reason behind this. His professor explained that he should check the valency and charge of the ion that he is using for the treatment.

1. It is difficult for DNA to pass through the membrane as

1. It is a hydrophilic molecule.
2. It is a hydrophobic molecule.
3. It is a circular molecule.
4. It changes its shape when it comes in contact with host cell.

2. What type of ions are used for DNA mediated gene transfers?

1. Divalent anions.
2. Divalent cations.
3. Monovalent cations.
4. Monovalent anions.

3. rDNA stands for,

1. reduced DNA
2. red DNA
3. recombinant DNA
4. related DNA.

4. Which of the following statements with regard to DNA is correct?

1. DNA is a positively charged molecule having two polynucleotide chains.
2. Nitrogen bases of two polynucleotide chain form complementary pairs, i.e., A opposite G and T opposite C.
3. Backbone of DNA chain is built up of alternate deoxyribose sugar and phosphate group.
4. Both (a) and (c)

5. Assertion: Competent host is essential for transformation with rDNA.

Reason: Transfer of DNA in a prokaryotic cell is called transfection.

1. Both assertion and reason are true and reason is the correct explanation of assertion.
2. Both assertion and reason are true but reason is not the correct explanation of assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Read the following and answer any four questions from (i) to (v) given below:

Alcohols are important industrial solvents. Ethanol, methanol, propanol and butanol are produced commercially by fermentation activity of some fungi, majorly yeasts. During fermentation, yeast cells convert cereal derived sugars into ethanol and CO₂ At the same time hundreds of secondary metabolites that influence the aroma and taste of alcohol are produced. Sugar concentration affects the rate of fermentation reactions. Yeast cannot grow in very strong sugar solution. In case of complex carbohydrate containing nutrient media, 1% malt or Rhizopus is used along with yeasts. Hydrolysis of starch is carried out at high temperature for 30 ruins. 'Tile crushed food mixed with hot water for obtaining malt in called mash. 'Tile nutrient medium prior to fermentation in called wort. Wort is cooled down to appropriate temperature and inoculated with strain of yeast.

1. Tile rate of alcohol production is measured on the basis of:

1. Amount of sugar present in the medium.
2. Amount of CO₂ produced per unit time.
3. Amount of yeast added in the medium.
4. All of these.

2. A number of chemicals are produced at the time of alcoholic fermentation with the change of nutrient media, pH and aeration. Select such by-product from the following.

1. Phenylethanol.
2. Amyl alcohol.
3. Glycerol.
4. All of these.

3. During alcoholic fermentation of cereals and potato, the crushed food mixed with hot water for obtaining malt is called:

1. Juice.
2. Mash.
3. Wort.
4. None of these.

4. Distilled alcohol with 95% ethanol content is called:

1. Absolute alcohol.
2. Rectified spirit.
3. Gin.
4. Brandy.

5. Assertion: Rhizopus or 1% malt is used in the nutrient medium when it contains complex carbohydrates.

Reason: Yeast does not possess sufficient diastase or amylase. 

1. Both assertion and reason are true and reason is the correct explanation of assertion.
2. Both assertion and reason are true but reason is not the correct explanation of assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Read the following text carefully and answer the questions that follow:
A healthy immune system defends the body against disease and infection. But if the immune system malfunctions, it mistakenly attacks healthy cells, tissues, and organs. Called autoimmune disease, these attacks can affect any part of the body, weakening bodily function and even turning life-threatening.

i. Why are autoimmune diseases called degenerative diseases? (1)
ii. Name the autoimmune disease of body muscles. (1)
iii. Which types of immunity is provided by T-lymphocytes? (2)
OR
Which immune cells form humoral immune system? (2)

Read the following and answer any four questions from (i) to (v) given below:

During copulation, semen is released by the penis into the vagina. 'The motile sperms swim rapidly, fuse with ovum in the ampullary region, resulting in fertilisation. Haploid nucleus of sperm fuse with that of ovum to form diploid zygote.

1. In female genital tract, sperms are made capable of fertilising the egg. This phenomenon of sperm activation is called:

1. Amphimixis.
2. Cortical reaction.
3. Capacitation.
4. Acrosomal reaction.

2. Select the correct sequence of various physical and chemical events that take place during fertilisation.

16. Fusion of cortical granules with plasma membrane of secondary oocyte.
17. Formation of fertilisation cone to receive sperm.
18. Release of sperm lysin from acrosome.
19. Mixing up of chromosomes of a sperm and an ovum.

1. R → Q → P → S
2. Q → S → R → P
3. Q → R → S → P
4. R → P → Q → S

3. Assertion: Only one sperm can fertilise an ovum.

Reason: The secretion of acrosome help the sperm to enter into cytoplasm of ovum through zona pellucida and plasma membrane.

1. Both assertion and reason are true, and reason is the correct explanation of assertion.
2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
3. Assertion is true, but reason is false.
4. Both assertion and reason are false

4. What is the significance of fertilisation?

1. It restores haploid number of chromosomes.
2. It produces offspring genetically identical to parents.
3. It initiates cleavage.
4. Both (b) and (c).

5. Site of fertilisation in humans is:

1. Endometrium of uterine cavity.
2. Ampullary isthmic junction of oviduct.
3. Cervix of uterus.
4. Infundibulum of fallopian tube.

Read the following and answer any four questions from (i) to (v) given below:
Enzymes are best known for their ability to catalise biochemical reactions without undergoing any change. A large number of enzymes are being used in biotechnological industry. Most of them are obtained from microbes. Proteases degrade proteins and polypeptides. Most of the commercially applicable proteases are alkaline and are biosynthesised mainly by bacteria such as Pseudomonas, Bacillus and some fungi like, Aspergillus. These enzymes are used in clearing beer, softening of bread and meat, degumming of silk, etc. Alkaline serine proteases have the largest applications in bio-industry. Alkaline proteases have shown their capability to work under high pH, temperature and in presence of inhibitory compounds. Another important group of enzymes is amylases. Amylolytic enzymes act on starch. These are obtained from Aspergillus, Rhizopus and Bacillus sp. These are used in softening and sweetening of bread, production of alcoholic beverages from starchy materials, clearing of turbidity in juices caused by starch, etc.

1. Polypeptides are degraded by:

1. Amylases.
2. Proteases.
3. Pectinases.
4. Lipases.

2. Amylolytic enzymes are not obtained from:

1. Aspergillus.
2. Aspergillus.
3. Mucor.
4. Bacillus.

3. Clearing of turbidity in juices caused by starch is achieved by:

1. Amylases.
2. Proteases.
3. Rennet.
4. Both (a) and (b).

4. Select the incorrect option from the following.

1. Enzymes are proteinaceous substances.
2. Enzymes are substrate specific.
3. Enzymes are large sized molecules.
4. Microbial enzymes can work only in normal temperature and pH.

5. A farmer harvests corns and prepares corn starch. He wants to prepare some corn syrup from this. for the conversion he needs to use enzyme ______.

1. Amylase.
2. Glucoamylases.
3. Glucoisomerases.
4. All of these.

Read the following and answer any four questions from (i) to (v) given below:
A group of teenagers was involved in drug abuse. 'They used syringes and needles to inject drugs. 'They indulged in this habit when they became adults. Administration of drug through needles became a piece of cake for them. Raj was the most active drug abuser amongst them and used to take drugs in high profile parties. In a span of time he started losing weight and suffered persistent diarrhoea. He developed constant low grade fever and used to catch opportunistic infection. When he consulted a doctor, he got himself tested for HIV in his blood and finally diagnosed with AIDS.
Based on the above information, answer the following questions.

1. Select the incorrect statement.

1. AIDS is a disorder of cell mediated immune system of the body.
2. AIDS is caused by Human Immunodeficiency virus.
3. AIDS infections were detected in India for the first time in prostitutes of Chennai, Tamil Nadu in 1986.
4. December 10 is recalled as World AIDS Day.

2. How do you think Raj got AIDS infection?

1. Through transfusion of HIV infected blood
2. Sexual intercourse with an infected partner
3. Sharing towel with infected friend
4. Use of contaminated needles and syringes to inject drugs

3. How AIDS can be diagnosed?

1. ELISA test
2. Ames test
3. Pap's test
4. Wida! test

4. How can AIDS be prevented?

1. Blood tests of blood donor before transfusion to check for the presence of AIDS virus.
2. Use of disposable needles and syringes for injecting medicines and vaccination
3. Having protected sex by use of condoms
4. All of these

5. Select the correct statement for AIDS virus.

1. It is rhomboid in shape with a diameter of 10-15 cm.
2. Its genome consists of ds DNA.
3. It consists of reverse transcriptase enzyme.
4. Its envelope consists of lipid bilayer and three protein coats.

Read the following and answer any four questions from (i) to (v) given below:

Rohan, a 13 year old school student, has been diagnosed with AIDS. He often complains of fever, nausea, headache and lethargy. Doctor advised some drugs to prolong his life.

1. What could be the most likely mode of transmission of disease to Rohan?

1. Artificial insemination.
2. Sexual intercourse with infected partner.
3. Sexual intercourse with infected partner.
4. Use of contaminated blade.

2. Name the drug prescribed for treatment of this disease.

1. Zidovudine.
2. Taxol.
3. Vinblastine.
4. Both (a) and (c).

3. Assertion: AIDS is an incurable STD.

Reason: AIDS virus attacks helper T-lymphocytes.

1. Both assertion and reason are true, and reason is the correct explanation of assertion.
2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
3. Assertion is true, but reason is false.
4. Both assertion and reason are false.

4. AIDS cannot be diagnosed by:

1. ELISA.
2. PCR.
3. Western blotting.
4. VDRL.

5. AIDS can be transmitted by:

1. Sharing towels.
2. Kissing.
3. Sharing contaminated needles.
4. All of these.