CBSE Sample Papers for Class 12 Biology Term 2 Set 1 with Solutions

Students can access the CBSE Sample Papers for Class 12 Biology with Solutions and marking scheme Term 2 Set 1 will help students in understanding the difficulty level of the exam.

CBSE Sample Papers for Class 12 Biology Standard Term 2 Set 1 with Solutions

Time Allowed: 2 Hours
Maximum Marks: 40

General Instructions:

• All questions are compulsory.
• The question paper has three sections and 13 questions. All questions are compulsory.
• Section-A has 6 questions of 2 marks each; Section-B has 6 questions of 3 marks each; and Section-C has a case-based question of 5 marks.
• There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions.
• Wherever necessary, neat and properly labeled diagrams should be drawn.

Section – A

Question 1.
‘Prevention is better than cure’ is an appropriate slogan to safeguard adolescents from drug abuse. List any six steps that could be taken in this regard?
Answer:
The steps are as follows:

1. Education and awareness is the first step to avoid such things.
2. Avoiding undue peer pressure as every child has his/her own personality and stamina to cope up with the existing society.
3. There should be regular monitoring of activities of adolescents behind them.
4. Parents must channelise the capacity of an individual into various recreational acts like sports, music and other such extra curricular activities.
5. Parents should seek professional and medical help from the experts and should insist the young generation to adopt activities like Yoga.
6. Parents must be able to identify the motivations for alcohols and drug abuse in the upcoming generation and keep a check on them.

Question 2.
Trying a particular drug even once may lead to addiction and complications. How should a youth under the influence of peer pressure to try a particular drug, be explained and convinced never to try a drug.
OR
Study the figure below and Identify the nature of product produced:

Answer:
The first dose of a drug may be just an experimentation of curiosity that is hiked by the friends. Once the drug enters the body it may get assimilated into the blood and the abuser may become unable to escape from it. In young generation, due to rising competition in academics and sports, the youths are easily drawn towards drugs and alcohol. Another reason of abusing such things is the feeling of loneliness or avoidance of parents due to their busy work schedule. Unstable and unsupportive family structures and peer pressures have drawn the youths towards alcoholism and drugs. Further dependence leads the patient to ignore all social norms and evacuates him or her from the society. Regular dosage of alcohol or drugs induces the symptoms like anxiety, shakiness, nausea, sweating, and inability to concentrate and remain in the social structure.
OR
Penicillin is used as an antibiotic medicine. It was due to chemical produced by the mould and name was given penicillin after the mould Penicillium notation.

Question 3.
Analyse the below given chemical structure and answer the questions based on it:

(i) The given structure is of which chemical?
(ii) What is the common name of this chemical?
(iii) What are the physical attributes of this chemical?
(iv) This chemical is obtained from which plant?
Answer:
(i) The chemical structure is of Morphine.
(ii) Heroin or Smack.
(iii) It is crystalline in nature, bitter in taste, white in colour and is odourless.
(iv) It is obtained from Papaver somniferum, commonly called as poppy plant.

Question 4.
Most living organisms cannot survive at the temperature above 45° C. How are some microbes able to live in habitats with temperatures exceeding 100° C?
Answer:
The organisms surviving in the extreme conditions are known as extremophiles. It has been found that certain organisms have colonised even in the underwater volcanic vents and hot springs. Such organisms are known as thermophiles. They have certain thermo resistant enzymes that carry out the metabolic processes even under high temperatures.

Question 5.
Apart from being the part of the food chain, predators play other important roles. Mention any two such roles supported by the examples.
Answer:
Other such roles are:
(i) Keeping the prey population under control. For example, wilder beast, the population is kept under control by the carnivores animals.
(ii) Act as a biological control agents to control specific species. For example, moths and lady bird beetle naturally feeding on the plant prickly pear.

Question 6.
Analyse the following given pie chart and answer the questions based on it.

(i) What conclusion can be derived from graph 1?
(ii) What does graph 2 say?
(iii) What is the ratio of fungi to the animals?
OR
Ecology at the organisms level is essentially physiological ecology which tries to understand how different organisms are adapted to their environments in terms of not only survival but also reproduction. The rotation of our planet around the Sun and the tilt of its axis cause annual variations in the intensity and duration of temperature, resulting in distinct seasons.

Give major abiotic factors governing the ecology and explain in short about temperature as a factor.
Answer:
(i) As according to the graph, there is maximum population of plants as compared to animals that
comprise of 70 percent of the total species population.
(ii) As according to graph, in plants, the most species having its existence on earth is fungi.
(iii) The existing fungal species, their population is more than the total population of fishes, reptiles, amphibians and mammals. So, the ratio of fungi to animals will be more than 1.
OR
The balance of the ecology is due to the balance between the biotic and abiotic factors that govern the ecology. These factors are:
(i) Biotic Factors
(a) Autotrophs
(b) Heterotrophs
(c) Decomposers

(ii) Abiotic Factors
(a) Temperature
(b) Water
(c) Light
(d) Soil

Temperature is the most important abiotic factor that maintains the balance in the ecosystem and related processes. Temperature regulates the kinetics of the enzymes present in the body of an organism, thereby controlling the metabolic activities of the organism. All related physiological features are governed by the temperature. But certain organisms that tolerate the extreme temperatures have been found. These are extremophiles. The organisms that tolerate wide range of temperatures are called eurythermal and those who tolerate narrow range of temperatures are called stenothermal. They are found to be present in the underwater sea volcanic vents and hot springs as well as under freeze ice cap of polar regions respectively. Therefore the thermal variation decides the extent of a geographically habitual area.

Section – B

Question 7.
Cancer is one of the most dreaded diseases of humans. Explain ‘Contact inhibition’ and ‘Metastasis’ with respect to disease. Name the groups of genes which have been identified in the normal cells that could lead to cancer and how they do so? Name any two techniques which are useful to detect cancers of internal organs. Why are cancer patients often given alpha interferon as part of the treatment?
OR
A woman was tested positive for AIDS. Name the pathogen that infected her. How does this pathogen weaken her immune system? Explain.
Answer:
Contact inhibition refers to the phenomenon by which, the contact with other cells inhibits the uncontrolled growth of the cancerous cells. In Metastasis, the tumour cells reach the distant organs site through the blood. The group of gene are oncogenes. When activated under certain conditions there is oncogenic transformation of cells. The techniques to detect cancers are Biopsy, Radiography, CT and MRI through which the presence of cancer can be detected. The alpha interferon activates the immune system and destroys the tumours, so it is given to the cancer patients as the part of the treatment.
OR
The disease named AIDS (Acquired Immuno-Deficiency Syndrome) is caused due to the pathogen named FFuman Immuno Deficiency Virus (HIV). When HIV enters the helper T-lymphocytes, it replicates and produces progeny virus. This progeny virus is released in the blood that attacks the other T-lymphocytes. Due to lack of helper cells, the person lacks immune power and is attacked by multiple pathogens. In the last stage, the person faces multiple infections and complications that lead to death.

Question 8.
During a school trip to ‘Rohtang Pass’, one of your classmates suddenly developed ‘altitude sickness’. But, she recovered after sometime.
(i) Mention one symptom to diagnose the sickness.
(ii) What caused the sickness?
(iii) How could she recover by herself after some time ?
Answer:
(i) The symptoms may be nausea, fatigue or heart palpitation.
(ii) The sickness was caused due to low atmospheric pressure which prevails at high altitude. The body does not get enough oxygen.
(iii) The body compensates low oxygen availability by increasing RBC production, decreasing the binding affinity of haemoglobin and by increasing breathing rate.

Question 9.
A and B are the two different cloning vectors in two different bacterial colonies cultured in a chromogenic substrate. Bacteria with cloning vector A were colourless whereas, those with B were blue coloured. Explain giving reasons the cause of the difference in colour that appeared.
Answer:
Alternative selectable markers have been developed which differentiate recombinants from non-recombinant DNA. In this procedure a recombinant DNA is inserted within the coding sequence of an enzyme called alpha galactose. It ends up in the inactivation of an enzyme which is called as insertional inactivation. The presence of chromogenic substrate gives blue-coloured colonies if the plasmid in the bacteria does not have an insert. The presence of insert results into the insertional inactivation of the alpha galactose and the colonies may not produce any colour.

Question 10.
Some organisms suspend their metabolic activities to survive in unfavourable conditions. Explain with the help of any four examples.
Answer:
The organisms that suspend their metabolic activities to survive in unfavourable conditions, their examples are:

• Polar bear: They undergo hibernation, to escape from the unfavourable conditions. After getting favourable normal temperature, they come back and gain the exhausted energy.
• Seeds of large plant and fungal species: Seeds undergo the state of dormancy in the extreme conditions. On getting the favourable conditions, the seeds germinate and grow. In context of fungal
  species, they produce thick walled spores and with the help of them, survive in the unsuitable conditions.
• Snails: The snails enter the aestivation to escape the hot summers.
• Some species of zooplankton: Zooplanktons enter diapause.

Question 11.
Given below is a schematic representation. Analyse and answer the questions asked on the basis of it:

(i) What does the graph show about?
(ii) What is the importance of biodiversity as according to the graph?
(iii) Do you think that climate has an adverse impact on biodiversity as according to the graph?
Answer:
(i) It explains the link between the biodiversity and other components of the ecosystem.

(ii) It is important because of the following points:
(a) It regulates the climate.
(b) It controls the ecosystem functions like biogeochemical cycling of nutrients.
(c) It provides ecosystem services to the human beings.

(iii) Yes, various anthropogenic processes and some ecosystem functions induce the changes in climatic patterns. This affects the biodiversity.

Question 12.
Analyse the diagram given below and answer the questions based on it:

(i) What does the above diagram represent?
(ii) What does the insulin contain?
(iii) What is the use of C-peptide in the diabetic patients?
(iv) How is insulin formed?
Answer:
(i) It represents the maturation of pro-insulin into insulin.
(ii) Insulin contains two short polypeptide chains that is chain A and chain B that are linked together with di-sulphide bridges.
(iii) It is useful for monitoring residual beta cell function in the human body under insulin therapy.
(iv) It is formed by chemical modification and cleavage of a precursor molecule.

Section – C

Question 13.
Genetic engineering, also called recombinant DNA technology, involves the group of techniques used to cut up and join together genetic material, especially DNA from different biological species, and to introduce the resulting hybrid DNA into an organism in order to form new combinations of heritable genetic material.

With advancement in genetics, molecular biology and tissue culture, new traits have been incorporated into crop plants. Explain the main steps in breeding a new genetic variety of crop.
OR
Analyse the diagram given below and answer the questions based upon it:

(i) What does the above given diagram represent?
(ii) In the diagram, what do A and B stand for?
(iii) What does the rop code for?
(iv) Is ori important? If we want to have many copies of target DNA, what should we do?
Answer:
In the process of developing a new genetic variety of crop, following steps are involved:

• The variability is collected through germplasm collection and preservation of different wild varieties.
• Selecting the desired parents in order to identify plants with desirable combination of traits through which the pure lines are produced.
• Carrying out cross-hybridisation among selected parents. Cross-hybridising the two parents produces the hybrids.
• The suitable progeny that has desired characters and is superior over its both the parents. Such recombinants are selected and tested.
• Further, the selected recombinants are tested for commercial release as a new cultivar.

OR
(i) The above given diagram is the E. coli cloning vector pBR322 depicting the restriction sites.
(ii) A is Hind III and B shows BamHl which are the restriction sites on the vector.
(iii) Rop codes for the proteins that are involved in the replication of the plasmid.
(iv) Yes, ori is important as it is a starting site of replication. Then the target DN A should be cloned in such a vector whose origin supports high copy number.