CBSE Sample Papers for Class 12 Biology Paper 1 are part of CBSE Sample Papers for Class 12 Biology. Here we have given CBSE Sample Papers for Class 12 Biology Paper 1.
CBSE Sample Papers for Class 12 Biology Paper 1
Board | CBSE |
Class | XII |
Subject | Biology |
Sample Paper Set | Paper 1 |
Category | CBSE Sample Papers |
Students who are going to appear for CBSE Class 12 Examinations are advised to practice the CBSE sample papers given here which is designed as per the latest Syllabus and marking scheme as prescribed by the CBSE is given here. Paper 1 of Solved CBSE Sample Paper for Class 12 Biology is given below with free PDF download solutions.
Time: 3 Hours
Maximum Marks: 100
General Instructions:
- There are total 26 questions and five sections in the question paper. All questions are compulsory.
- Section A contains question number 1 to 5, Very Short Answer Type Questions of one mark each.
- Section B contains question number 6 to 10, Short Answer Type Questions of two marks each.
- Section C contains question number 11 to 22, Short Answer Type Questions of three marks each.
- Section D contains question number 23, Value Based Question of four mark.
- Section E contains question number 24 to 26, Long Answer Type Questions of five marks each.
- There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examiner is to attempt any one of the question out of the two given in the question paper with the same question number.
- No. of printed pages are three.
SECTION-A
Question 1.
Apple is eaten as a raw fruit all over the world. But still known to be a false fruit. State the reason behind this fact.
Question 2.
What is hnRNA?
Question 3.
Estimate the way to predict the age of any fossil or a rock.
Question 4.
In what ways phenomenon of animal breeding is proved to be a successful event for livestock these days?
Question 5.
Under what conditions would a particular stage in the process of succession returns back to an earlier stage?
SECTION-B
Question 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.
Question 7.
State the criteria used for determining a biodiversity hotspot.
Question 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.
Question 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.
Question 10.
Differentiate between the process of development of a male and female gametophyte in plants.
SECTION-C
Question 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 off springs produced.
Question 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.
Question 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.
Question 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.
Question 15.
Some college students were caught partying with their friends at an illegal place. Police asked 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
- What are the reasons of attraction of children towards the drugs these days?
- State different modes of consumption of such drugs. ‘
- Name the organ of the body which can be affected by even little consumption of these drugs.
Question 16.
Give reasons for the following statements.
- Neutrophils and macrophages are called soldiers and scavengers of animal body.
- One should avoid driving after consuming alcohol.
- Persistent use of corticosteroids is harmful for human body.
OR
- Mutations are said to be beneficial for plant breeding. Taking an example, justify the statement.
- Discuss briefly the technology that made us self sufficient in food production.
Question 17.
What is single cell protein? What is the significance of such a protein?
Question 18.
A bacterium Bacillus thuringiensis produces a toxic protein called cry protein which is proved to be lethal to certain insects but not the bacterium itself. Explain how this happens.
Question 19.
Study the linking of DNA fragment shown below.
(1) Name ‘A’ DNA and ‘B’ DNA.
(2) Name the restriction enzyme that recognises this palindrome.
(3) Name the enzyme that can join these two DNA fragments.
Question 20.
What will be the fate of following structures in an angiospermic plant after fertilisation? Ovary wall, ovule, zygote, outer integument, inner integument and primary endosperm nucleus. 3 Q21. 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?
Question 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
Question 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.
- Give some known examples of species which have led to the recent extinction.
- List the major effects of loss of biodiversity.
- State different causes of loss of biodiversity.
SECTION-E
Question 24.
Hershey and Chase through their experimentations proved 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.
Question 25.
(1) State some major causes for air pollution.
(2) Mention the reason for converting the diesel buses of Delhi to run on CNG in the year 2002.
(3) 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
(1) An ecological succession is known to be a sequential, gradual and predictable changein the species composition in over a period of time. Define the terms given in regard of occurrence of succession in an ecology.
(a) Pioneer species
(b) Sere
(c) Ecological succession
(d) Climax community
(2) State the use of biodiversity in modem agriculture.
Question 26.
Typhoid 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
Answer 1.
Apple develops from the thalamus instead of ovary as in case of other fruits. Therefore, it is called a false fruit.
Answer 2.
Heterogenous RNA is a precursor RNA transcribed by RNA polymerase that contains both exons and intoms.
Answer 3.
Absolute dating method involving carbon (C14) dating technique, Uranium-lead technique and potassium-argon
technique are used in determining age of a fossil or a rock.
Answer 4.
Animal breeding mainly aims at increasing the yield of animals and improving the desirable qualities of the produce.
Answer 5.
The process of succession returns back to their earlier stages either by natural or human induced disturbances like fire, deforestation, etc.
SECTION-B
Answer 6.
The evidence that birds have evolved from reptiles provided by fossil Archaeopteryx are:
(1) It has beak and wings like that of a bird,
(2) It has teeth and scales similar to a reptile.
Answer 7.
The determination of a biodiversity hotspot were used by considering
(1) Number of endemic species which are not found anywhere else.
(2) Degree of threat which is measured in terms of habitat loss.
Answer 8.
Gemmule is a reproductive structure, which on germination gives rise to a new individual, e.g. reproduction in sponges occurs by the formation of gemmule.
OR
Answer 9.
GEAC stands for Genetic Engineering Approval Committee.
Its main objectives are:
(1) To examine the validity of genetically modified organisms. .
(2) Inspection for the safety of introducing genetically modified organisms for public services.
Answer 10.
Male Gametophyte | Female Gametophyte |
(1) It develops by the process called microsporangium. | It develops by the process of megasporo- genesis. |
(2) It is known as the process of formation of microspores insporogenous tissue due to meiosis. | It is known as the process of formation of megaspores in megaspore mother cell due to meiosis. |
(3) Microspore leads to the development of a male gametophyte. | Megaspore leads to the formation of a female gametophyte. |
SECTION-C
Answer 11.
The child bom with blood group ‘O’ has homozygous recessive alleles.Both the parents are heterozygous, i.e., genotype of father is IAi and mother is IBi for giving birth to a child with blood group ‘O’.
The possible genotypes of other offsprings will be ‘AB’, and ‘B’.
Answer 12.
Two reasons for increase in population are:
(1) A rapid decline in death rate, Maternal Mortality Rate (MMR) and Infant Mortality Rate (IMR).
(2) Increase in number of people in reproducible age.
Two steps taken to check the population explosion are:
(1) Statutory raising of marriageable age of the females to 18 years and that of males to 21 years.
(2) Incentives given to the couples with small families.
Answer 13.
Answer 14.
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) as per the law of segregation which do not show any blending.
Answer 15.
(1) Reasons for attraction of children towards drugs are:
- Curiosity and need of adventure, excitement and experiment.
- To avoid unsupportive family structure.
- Social pressure
- To avoid stress, depression and frustration.
(2) 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.
(3) Brain and Nervous system of human beings are often affected by these drugs.
Answer 16.
- Neutrophils and macrophages are called soldiers and scavengers of animal body as they dispose off microbes and dead cells by feeding on them.
- One should avoid driving after consuming alcohol as its consumption causes blurred vision,slow response, impaired judgement and reduced coordination of limbs.
- Use of corticosteroids causes osteoporosis (disease of bones, in which bones become weak and more likely to break), therefore its persistent use should be avoided.
OR
- Mutations in plants through diverse means leads to desirable characters development.
Example Resistance to yellow mosaic virus in lady finger (Abeimoschus esculentus) was transferred from a wild species and resulted in a new variety of a escultentus known as Parthani Kranti. - Plant breeding technology used in the green revolution has made us self sufficient in food production, which has eventually helped in the development of high yielding and disease-resistant varieties of wheat, rice, maize, etc.
Answer 17.
Single protein is a biomass obtained from microorganisms which can be treated or processed in food industry.
Significance of single cell protein:
- Its production reduces pollution as it uses organic wastes and industrial effluents.
- It provides a protein-rich diet.
- It takes off the pressure from agriculture system by fulfilling the demand of protein for human diet.
Answer 18.
1. The Bt toxin exists as inactive protoxin, which gets converted into its active form once an insect ingest it.
2. 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 binds to the surface of the midgut epithelial cells creating pores that causes swelling and lysis of the cells and eventually causes the death of an insect.
3. This protein has benefited the humans by producing bollworms and com borer-resistant crop of cotton and com.
- As Bt cotton, Bt com, etc.
- Producing pest resistant plants etc.
Answer 19.
- A is vector/plasmid DNA and B is a foreign DNA.
- EcoRI is the restriction enzyme that recognises this palindrome.
- DNA ligase helps in joining these two DNA fragments.
Answer 20.
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
Answer 21.
Ritesh’s cousin explained him that, such a change had occurred in that area due to a process of succession of rocks. As during early period, lichens were the pioneer species on a bare rock, which had secreted organic acids and had dissolved 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 along with 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.
Answer 22.
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 to get biological active substances derived from such organisms. The process in bioreactor can be either aerobic or anaerobic in nature. 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
Answer 23.
(1) Some examples of recent extinction are Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Steller’s sea cow (Russia) and three sub-species of tiger (Bali, Javan, Caspian)
(2) Some major effects of loss of biodiversity are :
- Decline in plant production Over exploitation
- Alien species invasions Co-extinctions
(3) Causes of loss of biodiversity are:
- Habitat loss and fragmentation Over-exploitation
- Alien species invasion Co-extinctions
SECTION-E
Answer 24.
Alfred Hershey and Martha Chase carried out experiment to find out that DNA acts as a genetic material in many living things. They carried this experiments with the viruses that infect bacteria and performed this 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 bacteriosphages.
(1) One medium contained radioactive phosphorus and’the other medium contained radioactive sulphur.
(2) The growth of viruses in the presence of radioactive phosphorus (35P) contained DNA (but not radioactive protein). This is because DNA contains phosphorus. In the same way viruses grown in the presence of radioactive sulphur (35S) contained radioactive protein (but not radioactive DNA). This is because DNA does not contain sulphur.
(3) These radioactive viruses (bacterio-phages) were then allowed to attach to a bacteria (E. coli).
(4) They observed that the bacteria that were infected with virus containing radioactive DNA were radioactive whereas, bacteria infected with the virus containing p
rotein 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
Function of each part of the unit involved:
(1) A Promotor: It is a DNA sequence that provides binding site for RNA polymerase. It also defines the template and coding strands.
(2) Structural gene: It produces mRNA (transcription) which in turn, synthesises polypeptide on ribosome translation.
(3) A Terminator: It defines the end of transcription.
Answer 25.
(1) Causes for Air Pollution: Smoke emanating from thermal power plants and automobiles, smelters and other industries which release particulate and gaseous air pollutants together with harmless gases such as nitrogen and oxygen.
(2) All buses were converted to run on CNG by the end of2002 in Delhi, as CNG is cleaner. It bums more efficiently than petrol or diesel in the automobiles and very little of its unbumt. It is also known to be cheaper than petrol or diesel and cannot be siphoned off by thieves and adultered like petrol or diesel.
OR
(1)
(a) Pioneer Species: The species invading a bare area.
(b) Sere: The entire sequence of communities that successfully changes in a given area.
(c) Ecological Succession: The gradual and fairly predictable change in the species composition of a given area.
(d) Climax Community: The composition and structure of community constantly change in response to the changing environment conditions. These changes lead finally to a community that is near equilibrium with the environment.
(2) 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.
Answer 26.
Diseases |
Causative Agent |
Symptoms |
Ways by which infection enters |
Typhoid |
Salmonella typhi, bacterium |
Sustained high fever (39° to 40°C), weakness, stomach pain,constipation, headache and loss of appetite |
Small Intestine through contaminated water and food. Migrates to other organs through blood. |
Pneumonia |
Streptococcuss |
Fever, chills, cough and head-ache. In severe cases, the lips and fingernails turn grey to bluish. |
Inhalation of aerosol droplets released by infected person and by sharing glasses or utensils. |
OR
The different types of antibodies produced in body at different time and at different locations are illustrated below:
Types of Antibodies | Functions |
IgG (Most prevalent) |
It protects against fungi, bacteria, toxins, etc. It can cross the placental barrier and provide immunity to the foetus. |
IgM (First antibody) |
It is responsible for blood transfusion reaction in ABO blood groups system. |
IgA (Second most prevalent) |
It is secreted through the mucous lining of the digestive tract,saliva, tears, etc. It is also found in colostrum, providing immunity to the newborn. |
IgE | It is the least common antibody involved in allergic reactions. |
IgD | Their function is not well understood till date. |
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