CBSE Sample Papers for Class 12 Biology Solved 2016 Set 5

Section A

1.Apple is eaten as a raw fruit all over the world. But still known to be a false fruit. State the reason behind the fact.

2.What is hnRNA?

3.Estimate the way to predict the age of any fossil or a rock.

4.In what way phenomenon of animal breeding is proved to be a successful event for livestocks these days? Explain.

5.Under what conditions would a particular stage in the process of succession returns back to an earlier stage?

Section B

7.State the criteria used for determining a biodiversity hotspot.

8.What does a mass of cells released by sponges is called? Give one example where this helps in reproduction.
Or
Diagrammatically represent the process of multiple fission in Plasmodium.

9.Indian government had established the GEAC under rules 1989 to make all decisions on its own. Expand the term GEAC and also state the objectives behind setting this committee.

10.Differentiate between the process of development of a male and female gametophyte in plants.

Section C

13.Draw a neat and a well labelled diagram of the longitudinal section of a maize grain featuring the structure of a well matured embryo.

16.Give reasons for the following statements.
(i) Neutrophils and macrophages are called soldiers and scavengers of animal body.
(ii) One should avoid driving after consuming alcohol.
(iii) Persistent use of corticosteroids is harmful for human body.
Or
(i) Mutations are said to be beneficial for plant breeding. Taking an example, justify the statement.
(ii) Discuss briefly the technology that made us self sufficient in food production.

17.Given below is a diagrammatic representation of the experimental set up being used by SL Miller for his experiment.

(i) Write the names of different gases contained and the conditions set for the reaction in the flask A.
(ii) State the type of organic molecule he collected in the water at ‘B’.
(iii) Write the conclusion he arrived at.

18.A bacterium Bacillus thuringiensis produces a toxic protein called cry protein which is proved to be lethal to certain insects but not to the bacterium itself.
(i)Why this toxin felt unable to kill bacteria?
(ii)Mention the changes that occurs in the gut of insects after consuming protein.
(iii)List any two ways by which man has exploited this protein for his benefits.

19.Study the linking of DNA fragment shown below.

(i) Name A DNA and ‘B’
(ii) Name the restriction enzyme that recognises this palindrome.
(iii) Name the enzyme that can join these two DNA fragments.

20.What will be the fate of following structures in an angiospermic plant? Ovary wall, ovule, zygote, outer integument, inner integument and primary endosperm nucleus.

22.Illustrating the design of a bioreactor, highlight the difference between a flask in your laboratory and a bioreactor which allows cells to grow in a continuous culture system?

Section D

Section E

25.(i) State some major causes for air pollution.
(ii) Mention the reason for converting the buses of Delhi to run on CNG by the end of the year 2002.
(iii) Draw the labelled diagram of electrostatic precipitator that is used to remove fine particles from a flowing gas using the force of an induced change.
Or
(i) An ecological succession is known to be a sequential, gradual and a predictable change in the species composition in over a period of time. Define the terms given in the regard of occurrence of succession in an ecology.
(a) Pioneer species (b) Sere
(c) Ecological succession (d) Climax community
(ii) State the use of biodiversity in modern agriculture.

26.0Typhoid and pneumonia are the bacterial diseases that infects human beings. Discuss the causative agent, symptom and the way in which an infection enters the human body?
Or
Antibodies are produced by B-lymphocytes in response to pathogens. Explain in detail the types and roles of antibodies.

Answers

Section A

1.Apple is eaten as a raw fruit all over the world. But still known to be a false fruit. State the reason behind the fact.
Ans. Apple is called false fruit, because in false fruits, different flower parts (except ovary) contributes in the formation of a fruit. In case of apple, thalamus contributes in fruit formation.

2.What is hnRNA?
Ans. The precursor RNA transcribed by RNA polymerase that contains both exons and introns, is called /7/7RNA (heterogenous RNA).

3.Estimate the way to predict the age of any fossil or a rock.
Ans. Age of any fossil or a rock can be calculated by the absolute dating method involving carbon (C¹⁴) dating technique. Uranium-lead technique and potassium-argon technique are also used in determining age of a fossil or a rock.

4.In what way phenomenon of animal breeding is proved to be a successful event for livestocks these days? Explain.
Ans. Animal breeding acts as an important phenomenon these days because it mainly aims at increasing the yield of animals and improving the desirable qualities of the produce.

5.Under what conditions would a particular stage in the process of succession returns back to an earlier stage?
Ans. Natural or human induced disturbances like fire, deforestation, etc. are responsible for bringing the process of succession back to their earlier stages.

Section B

6.Archaeologists believe that there is some connecting link between the birds and reptiles i.e. ‘Birds have somewhere been evolved from reptiles’. Give evidences what Palaeontology provides in support of the above statement.
Ans. The fossil Archaeopteryx is a connecting link between reptiles and birds, which provides the evidence that birds have evolved from reptiles.
The evidences are
(i)It has beak and wings like that of a bird, (ii) It has teeth and scales similar to a reptile.

7.State the criteria used for determining a biodiversity hotspot.
Ans. The criteria used for determining a biodiversity hotspot are
(i)Number of endemic species which are not found anywhere else.
(ii)Degree of threat which is measured in terms of habitat loss.

8.What does a mass of cells released by sponges is called? Give one example where this helps in reproduction.
Or
Diagrammatically represent the process of multiple fission in Plasmodium.
Ans. A mass of cells enclosed within a common opaque envelope, being released by sponges is called gemmule. This is a reproductive structure, which on germination gives rise to a new individual, e.g. reproduction in sponges occurs by the formation of a gemmule.
Or
Diagrammatic representation of multiple fission in plasmodium is given below

9.Indian government had established the GEAC under rules 1989 to make all decisions on its own. Expand the term GEAC and also state the objectives behind setting this committee.
Ans. GEAC is expanded as Genetic Engineering Approval Committee
Main objectives of GEAC are
(i)To examine the validity of genetically modified organisms.
(ii)Inspection for the safety of introducing genetically modified organisms for public services.

10.Differentiate between the process of development of a male and female gametophyte in plants.
Ans. The process of development of a male and female gametophyte in plants is known as microsporogenesis and megasporogenesis respectively.

Section C

11.One of the child of a couple was born with a blood group ‘O’. If the same father having blood group A’ and mother having blood group ‘B’, were, crossed then predict out the possible genotypes of both parents and other offsprings produced.
Ans. The child with blood group ‘O’ will have homozygous recessive alleles.
In this case, both the parents should be heterozygous, i.e., the genotype of father should be l^Ai and mother should be I ^Bi for giving birth to a child with blood group ‘O’.

12.At the time of Independence, the population of India was 350 million, which exploded to over 1 billion by May 2000. List any two reasons for this rise in population and any two steps taken by the government to check this population explosion.
Ans. Two reasons for increase in population are
(i) A rapid decline in death rate, Maternal Mortality Rate (MMR) and Infant Mortality Rate (IMR).
(ii) Increase in number of people in reproducible age.
Two steps taken to check the population explosion are
(i) Statutory raising of marriageable age of the females to 18 years and that of males to 21 years.
(ii) Incentives given to the couples with small families.

13.Draw a neat and a well labelled diagram of the longitudinal section of a maize grain featuring the structure of a well matured embryo.
Ans. Longitudinal sectional view of a maize grain is given below

14.Design the cross proposed by Mendel to prove that the gametes does not show the blending of the two characters in the F₂ generation with the help of a checker box defining the law responsible for this fact.
Ans. Law of segregation states that the factors or alleles of a pair segregates from each other during gamete formation, such that a gamete receives only one of the two factors. They do not show any blending. Hence, known as the law of purity of gametes. This can be easily proved by the cross given below between a homozygous tall plant (TT) which is dominant and a hemizygous dwarf plant (tt).

15.Some college students were caught partying with their friends at an illegal place. Police said victims to call their parents as the students were taking drugs and were not in the condition to go back home. Observe the condition and answer the following questions that follows.
(i) What are the reasons of attraction of children towards the drugs these days?
(ii) State different modes of consumption of such drugs.
(iii) Name the organ of the body which can be affected by even little consumption of these drugs.
Ans. (i) Reasons for attraction of children towards drugs these days are
(a) Curiosity and need of adventure, excitement and experiment.
(b) To avoid unsupportive family structure.
(c) Social pressure
(d) To avoid stress, depression and frustration.
(ii) The drugs such as cannabinoids are often mixed with tobacco and smoked. Bhang, another form of drug is even taken orally as an ingredient of a drink or food.
(iii) These drugs often affects the brain and nervous system of human beings.

16.Give reasons for the following statements.
(i) Neutrophils and macrophages are called soldiers and scavengers of animal body.
(ii) One should avoid driving after consuming alcohol.
(iii) Persistent use of corticosteroids is harmful for human body.
Or
(i) Mutations are said to be beneficial for plant breeding. Taking an example, justify the statement.
(ii) Discuss briefly the technology that made us self sufficient in food production.
Ans. (i) Neutrophils and macrophages disposes off microbes and dead cells by feeding on them. Hence, they are called soldiers and scavengers of animal body.
(ii) Consumption of alcohol causes blurred vision, slow response, impaired judgement and reduced coordination of limbs. Hence, one should avoid driving after consuming an alcohol.
(iii) Persistent use of corticosteroids is harmful because it causes osteoporosis (disease of bones, in which bones become weak and more likely to break).
Or
(i) Inducing mutations in plants through diverse means and then screening the plant materials for resistance, sometimes leads to desirable genes being identified. Plants having these desirable characters can then be either multiplied directly or can be used in breeding.
Example Resistance to yellow mosaic virus in bhindi (Abeimoschus esculentus) was transferred from a wild species and resulted in a new variety of A esculentus known as Parbhani Kranti.
(ii) Plant breeding technology used in the green revolution has made us self sufficient in food production. This has eventually helped in the development of high yielding and disease-resistant varieties of wheat, rice, maize, etc.

17.Given below is a diagrammatic representation of the experimental set up being used by SL Miller for his experiment.

(i) Write the names of different gases contained and the conditions set for the reaction in the flask A.
(ii) State the type of organic molecule he collected in the water at ‘B’.
(iii) Write the conclusion he arrived at.
Ans. (i) The different gases contained were methane (CH₄), hydrogen(H₂), ammonia(NH₃) and water vapour. Electric discharge was created at 800°C in the closed flask.
(ii)Amino acid as organic molecules were collected in the water at ‘B’.
(iii)He arrived at the conclusion that life has came from pre-existing, non-living organic
molecules and the formation of life was preceded by chemical evolution.

18.A bacterium Bacillus thuringiensis produces a toxic protein called cry protein which is proved to be lethal to certain insects but not to the bacterium itself.
(i)Why this toxin felt unable to kill bacteria?
(ii)Mention the changes that occurs in the gut of insects after consuming protein.
(iii)List any two ways by which man has exploited this protein for his benefits.
Ans. (i) The Bt toxin is present in bacteria in an inactive form known as protoxin, which gets converted into its active form after entering the gut of an insect.
(ii)After entering the body of an insect it gets converted into an active toxin due to the alkaline pH of its gut which solublises the crystals. This activated toxin then gets bind to the surface of the midgut epithelial cells creating pores that causes swelling and lysis of the cells. Finally leads to the death of the insect.
(iii)Man has exploited this protein for his benefits by

introducing these genes to crop plants such as Bt cotton, Bt corn, etc.
producing pest resistant plants etc.

19.Study the linking of DNA fragment shown below.

(i) Name A DNA and ‘B’
(ii) Name the restriction enzyme that recognises this palindrome.
(iii) Name the enzyme that can join these two DNA fragments.
Ans. (i) ‘A is vector/plasmid DNA and ‘£?’ is a foreign DNA.
(ii) Eco Rl is the restriction enzyme that recognises this palindrome.
(iii) DNA ligase helps in joining these two DNA fragments.

20.What will be the fate of following structures in an angiospermic plant? Ovary wall, ovule, zygote, outer integument, inner integument and primary endosperm nucleus.
Ans. Following structures of an angiospermic plant after fertilisation will result into
Ovary wall – Pericarp
Ovule – Seed
Zygote – Embryo
Outer integument – Testa
Inner integument – Tegmen
Primary endosperm nucleus – Endosperm

21.Ritesh went to his cousin’s place on hills, where he found very large plants. He got surprised because he was remembering the place to be exactly same which he had visited some years before. He asked his cousin about such a rapid change of plantation of that area. Being his cousin how will you satisfy Ritesh?
Ans. Ritesh’s cousin explained him that, such a change had occurred in that area due to a process of succession on rocks. As during early period, lichens were the pioneer species on a bare rock, which had secreted organic acids and had dissolves and corroded the rock surface.
This has produced depression and releases out minerals that were being required for the proper growth of the lichens.
The lichens hold the fine particles of the rock alongwith the sand particles that were being brought up by the wind to initiate the soil formation. This thus, paves way for the next community i.e. bryophytes following various serai communities. Finally, the forests had became the climax community which remains stable as long as the environment remains unchanged.

22.Illustrating the design of a bioreactor, highlight the difference between a flask in your laboratory and a bioreactor which allows cells to grow in a continuous culture system?
Ans.

Bioreactor differs from a laboratory flask in a way that the bioreactor refers to any manufactured or engineered device or a system that supports a biologically active environment. In this a chemical process is carried out to involve organisms or biologically active substances derived from such organisms. The process in bioreactor can be either aerobic or anaerobic in nature. While, the flask used in laboratory is for making solutions, holding, containing, collecting or sometimes measuring chemicals, samples, solutions, etc. for the chemical reactions or other process such as mixing, heating, cooling, dissolving, boiling precipitation or some analysis i.e it does not allow the growth of microbes in it.

Section D

23.Undue human activities have accelerated the rate of extinction of species from the earth. Due to which our biological wealth is declining day by day. Being a good citizen of a country like India, Ankit is concerned about the issue and its long term effects.
(i)Give some known examples of species who had led to the recent extinction.
(ii)List the major effects of loss of biodiversity.
(iii)State different causes of loss of biodiversity
Ans. (i) Some examples of recent extinction are Dodo (Mauritius) quagga (Africa), thylacine (Australia), Steller’s sea cow(hussia) and three sub-species of tiger (Bali, Javan, Caspian)
(ii)Some major effects of lost of biodiversity are

Decline in plant production
Lower resistance and resilience to environment
Perturbations such as drought and increased variability in ecosystem process such as plant productivity, water use, diseases, etc.

(iii)Different causes of loss of biodiversity are

Habitat loss and fragmentation
Over exploitation
Alien species invasions.
Co-extinctions

Section E

24.Hershey and Chase through their experimentations proves that DNA acts as the genetic material in most living things including humans, plants, bacteria, etc. Explain experimentally with the help of a diagram.
Or
Sketch out a labelled and schematic structure of a transcription unit explaining the function of each part of the unit involved in the process of transcription.
Ans. Alfred Hershey and Martha Chase experimented out to find out that DNA acts as a genetic material in many living things. They carried out some experiments with the viruses that infect bacteria and performed their experiment with E. coli and T₂ bacteriophage to predict out whether it was protein or DNA from the virus that had entered into the bacteria. For this they took two separate media for growing these bacteriophages.
(i) Out of the two, one medium contained radioactive phosphorus and the other medium contained radioactive sulphur.
(ii) The viruses grown in the presence of radioactive phosphorus (³⁵P) contained radioactive DNA (but not radioactive protein). This is because DNA contains phosphorus. In the same way viruses grown in the presence of radioactive sulphur (³⁵S) now contained radioactive protein (but not radioactive DNA). This is because DNA does not contain sulphur.
(iii) These radioactive viruses (bacteriophages) were then allowed to attach to bacteria (E.coli).
(iv) They observed that the bacteria that were infected with virus containing radioactive DNA were radioactive whereas, bacteria infected with the virus containing protein were not radioactive. This indicates that only DNA and not the protein coat entered the cell. Thus, the genetic material was DNA and not protein that passed from virus to bacteria.

Or
Transcription unit in a DNA molecule is comprised of three main regions (i) A promoter (ii) The structural gene (iii) A terminator
Schematic structure of a transcription unit
The promoter site is located towards 5′ end of the structural gene. The two strand of the DNA in the structural gene have opposite polarity, i.e., one strand has 3′-»5′ polarity and the other strand has 5’—>3′ polarity. The 3’—>5′ polarity strand acts as a template strand. The other with polarity 5′-»3′ acts as a coding strand.
(i) Promoter is a DNA sequence that provides binding site for RNA polymerase. It is located at 5¹– end (upstream) of structural gene.
(ii) Structural gene is a transcription unit flanked by the promoter and terminator. It produces mRNA (transcription) which in turn, synthesises polypeptide on ribosome translation.
(iii) Terminator is located at the3′- end (downstream) of the coding strand. It defines the end of transcription.

25.(i) State some major causes for air pollution.
(ii) Mention the reason for converting the buses of Delhi to run on CNG by the end of the year 2002.
(iii) Draw the labelled diagram of electrostatic precipitator that is used to remove fine particles from a flowing gas using the force of an induced change.
Or
(i) An ecological succession is known to be a sequential, gradual and a predictable change in the species composition in over a period of time. Define the terms given in the regard of occurrence of succession in an ecology.
(a) Pioneer species (b) Sere
(c) Ecological succession (d) Climax community
(ii) State the use of biodiversity in modern agriculture.
Ans. (i) Causes for Air Pollution Smoke stacks of thermal power plants. Smelters and other industries which release particulate and gaseous air pollutants together with harmless gases such as nitrogen and oxygen.
(ii) All buses were converted to run on CNG by the end of 2002 because CNG is better than diesel or petrol, in the following ways.
(a) It burns more efficiently than petrol or diesel in the automobiles and very little of it is left unburnt.
(b) It is known to be cheaper than petrol or diesel and cannot be siphoned off by thieves and adultered like petrol or diesel.
(iii) The diagram of electrostatic precipitator is given below

Or
(i) (a) Pioneer Species The species invading a bare area are called pioneer species.
(b) Sere The entire sequence of communities that successfully changes in a given area are called sere.
(c) Ecological Succession The gradual and fairly predictable change in the species composition of a given area is called ecological succession.
(d) Climax Community The composition and structure of community constantly change in response to the changing environmental conditions. These changes lead finally to a community that is near equilibrium with the environment and called as climax community.
(ii) Use of Biodiversity in Modern Agriculture
Agrochemicals cause pollution of soil and water but are too expensive for the farmers.
Genetic modification has made the crops more tolerant to abiotic stresses like cold, heat,
drought, salinity, etc. It has also reduced the dependence of crops on chemical pesticides as they are pest resistant.

26.0Typhoid and pneumonia are the bacterial diseases that infects human beings. Discuss the causative agent, symptom and the way in which an infection enters the human body?
Or
Antibodies are produced by B-lymphocytes in response to pathogens. Explain in detail the types and roles of antibodies.
Ans. Typhoid and pneumonia are bacterial diseases that infects human in one or the other way out.
(i) Typhoid It is a disease caused by the bacteria, Salmonella typhi way of entry. It enters the intestine through contaminated water and food and migrates to other organs of the body through blood.
Symptoms It includes high fever (39-40°C), weakness, stomach pain, constipation, headache and loss of appetite. Intestinal preformation and death may also occur in serious cases.
(ii) Pneumonia It is caused by bacteria retreptococcus pneumonia and haemophiles influence. It infects alveoli of lungs
Way of entry It enters the body by inhaling the droplets aerosols released by an infected person and also by sharing glasses and utensils with an infected person.
Symptoms It includes fever, chills, cough and headache. In severe cases, lips and fingernails may turn greyish to blueish.
Or
Antibody is a type of protein molecule produced by the B-lymphocytes in response to pathogens. Each antibody is produced in response to a specific pathogen. It has four peptide chains. Antibody mediated response is called as humoral immune response.
These different types of antibodies produced in body at different time and at different locations.

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