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

CBSE Sample Papers for Class 12 Biology Standard Term 2 Set 2 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.
A bioreactor is important for commercial production of certain products. Explain.
Answer:
A bioreactor can provide the required optimal conditions for producing desired product. Such optimal growth conditions may be ideal temperature, pH, substrate, salts, vitamins and oxygen. Thus, a bioreactor is important for commercial production of certain products.

Question 2.
A patient showed symptoms of constipation, abdominal pain and stools with excess mucous and blood clots. Name the disease and its pathogen. Where do these pathogens live in the patient’s body? Name the mechanical carrier that transmits the parasite.
OR
“Growing spirulina on a large scale is beneficial both environmentally and nutritionally for humans.” Justify.
Answer:
According to the symptoms given, the disease that the patient is suffering from is amoebiasis. The pathogen responsible for this disease is Entamoeba histolytica. The pathogen lives in the large intestine of the human body. The pathogens are carried by houseflies from one place to another and is also directly contacted by the usage of contaminated water and food.
OR
Spirulina can easily be grown on materials like waste water from potato processing plant, straw, molasses, animal manure, sewage which helps to reduce environmental pollution. Spirulina also serves as food rich in proteins, carbohydrates, fats, vitamins and minerals.

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

Question 3.
There are certain pictures shown below. According to your sense, identify the picture which fits into the group that justifies the theme:
Theme: Awareness generation about alcoholism
Options:
CBSE Sample Papers for Class 12 Biology Term 2 Set 2 with Solutions 1
Answer:
The picture shown in option (i) is a correct answer. Picture (ii) is anti-smoking and picture (iii) is anti-drug.

Question 4.
Pollinating species of wasp shows mutualism with specific fig plants. Mention the benefits the female wasps derive from the fig trees from such an interaction.
Answer:
The female wasp lays eggs in the fruit of fig plant for dual purpose. It gets the site for laying the eggs and it nurtures the larvae by feeding them the seeds. In turn, the wasp pollinates the fig inflorescence while searching the suitable site for egg laying. In favour of pollination, the wasp gets the developed seeds to nourish its young ones. This is a co-evolution.

Question 5.
Plants that inhabit a rain forest are not found in a wetland. Explain.
Answer:
Plant inhabiting a rain forest are not adapted to survive in aquatic conditions or wetlands. Plants are conformers. They are stenothermal. They cannot maintain a constant internal environment or temperature. The osmotic concentration of their body fluids affects the kinetics of enzymes through basal metabolic activity.

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

Question 6.
Temperature is the most important abiotic factor that governs the environment. Explain.
OR
An exotic variety of Prickly pear introduced in Australia turned out to be intensive. How was it brought under control?
Answer:
Temperature governs the kinetics of the enzymes that regulate the metabolism, its related activities and other related physiological functioning of an organism. Hence, it is an important abiotic factor governing the environment.
OR
The Prickly pear was controlled by using cactus feeding predator, a moth that feed on the plant.

Section – B

Question 7.
Principle of vaccination is based on the property of “memory” of the immune system. Taking one suitable example, justify the statement.
OR
Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why?
Answer:
When a vaccine containing heat-killed or attenuated pathogen is introduced into the body to prevent chickenpox or measles, it produces antibodies against the antigen of the pathogen. This also generates B and T memory cells that recognise the pathogen quickly on subsequent exposure to produce large amount of antibodies which inactivate the pathogen causing the disease. This shows that vaccination is based on the memory of the immune system.
OR
A sample of curd can be used to study the microbes under microscope. A drop of curd contains millions of bacteria. A curd contains Lactic Acid Bacteria (LAB) called Lactobacillus. They digest and coagulate milk proteins by producing acids. Simple to study and easy to carry, a sample of curd can be preferred.

Question 8.
During a fire in an auditorium, a large number of assembled guests got burnt beyond recognition. Suggest and describe a modern technique that can help to hand over the dead bodies to their relatives.
Answer:
DNA fingerprinting is the modern technique that can help the authorities to hand over the dead bodies to their relatives. It includes series of steps which are as follows:

  • Isolation and digestion of DNA by restriction endonuclease.
  • Separation of DNA fragments by electrophoresis and transferring them to synthetic membranes such as the nitro-cellulose or nylon membrane.
  • Hybridisation using labelled probe.
  • Detection of hybridised DNA fragments by autoradiography.
  • Matching banding pattern of DNA, DNA fingerprints or autoradiograms of the guests who lost their lives during the accident and that of their relatives.

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

Question 9.
Bt-toxins are released as inactive crystals in the bacterial body. What happens to it in the cotton boll worm body that it kills the boll worm?
Answer:
In the cotton boll worm body, Bt-toxin is converted into an active protein due to the alkaline pH of its gut. The toxin binds to the midgut cells, create pores and causes swelling and lysis of the cells. This kills the boll worm.

Question 10.
The species diversity of plants (22 percent) is much less than that of animals (72 percent). What could be the explanation to how animals achieved greater diversification?
Answer:
About more than 70% of species recorded on the earth are animal species. Only 22% plant species exist. So analysing the data, we can understand that, there is quiet a large difference in their percentage. This is because animals have adapted themselves to ensure their survival in changing environments in comparison to plants. For example, insects and other animals have developed a complex nervous system to control and coordinate their body structure.

Question 11.
The graph given below shows the species-area relationship. Answer the following question as directed: (i) Name the naturalist who studied the kind of relationship shown in the graph. Write the observation made by him?
(ii) Write the situations as discovered by ecologists when the value of ‘Z’ (slope of line(s)) lies between
(a) 0.1 and 0.2 (b) 0.6 and 1.2
(iii) When would the slope of the line ‘b’ become steeper?
CBSE Sample Papers for Class 12 Biology Term 2 Set 2 with Solutions 2
Answer:
(i) The naturalist Alexander Von Humboldt explained about the above given graph. His observations
suggested that, the species richness increases with an increase in explored area but upto certain limit.
(ii) (a) It shows unaffected distribution in an area. It is a normal range.
(b) The value shows steeper slope of regression, that can be analysed when the species area relationship is studied on very large area say, for example, an entire continent.
(iii) The slope of the line ‘b’ becomes steeper when the species richness will be between 0.6 to 1.2.

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

Question 12.
EcoRl is used to ait a segment of foreign DNA and that of a vector DNA to form a recombinant D
Show with the help of schematic diagrams and answer the following questions.
CBSE Sample Papers for Class 12 Biology Term 2 Set 2 with Solutions 3
(i) After the entire process shown in the above diagram, what is resultant A?
(ii) EcoRl cuts the DNA between the bases. What does EcoRI stand for?
(iii) What are sticky ends?
Answer:
(i) The above diagram shows the action of restriction endonuclease and thus forms a recombinant DNA after completion of entire process.

(ii) Eco stands for Escherichia coli, R stands for the name of the strain and Roman I indicates the order in which the enzymes were isolated from the strains of the bacteria.

(iii) They are the resultant of hydrogen bonding that act as the site for attachment for the separated
DNA fragments and facilitate the action of enzyme called DNA ligase.

Section – C

Question 13.
Analyse the diagram given below and answer the questions based on it.
(i) Why is an antibody designated as H2L2?
(ii) What is humoral immune response?
(iii) Give the functions of IgA, IgM, IgE and IgG.
CBSE Sample Papers for Class 12 Biology Term 2 Set 2 with Solutions 4
OR
CBSE Sample Papers for Class 12 Biology Term 2 Set 2 with Solutions 5
Nitrogen fixation occurs in nodules on legume roots.
Which of the Nitrogen fixer is involved in symbiotic association with legumes forming root nodules
shown in the above figure?
Answer:
(i) Each antibody molecule consists of two light chains and two longer chains called heavy chains. So to represent the number of chains it is designated as H2L2.

(ii) It is the response given by the antibodies that are found in blood, such responses are called humoral immune response.

(iii) The functions are as follows:
(a) IgA: The Immunoglobulin A is a neutralising antibody that acts as the first line of defence against mucosal pathogens. It gets attached to the epithelial surfaces and prevents the invasion of pathogens. It comprises about 10 to 15 % of the total antibodies present in the body.

(b) IgM: It functions in production of B-cells. It is the first antibody to appear in response to the exposure of an antigen. It appears in the early course of infection and can reappear from time to time as per the growth of infection. It is also responsible for reactions of blood transfusion in ABO blood system.

(c) IgE: This specific antibody is found in lungs, skin and mucous membrane that travels to the cell and releases the chemicals causing allergic reactions.

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

(d) IgG: This immunoglobulin is responsible for deciding the Rh-factor of the blood. They function in protecting the body from viral and bacterial infections. It comprises about 70 to 80 % of the total antibodies present in the body.
OR
Rhizobium
The symbiotic relationship between soil bacteria, collectively known as rhizobia (which includes the genera Rhizobium, Bradyrhizobium, Mesorhizobium, and Sinorhizobium), and legume roots, generates nodules (a new differentiated organ), which fix atmospheric dinitrogen (N2) through the action of the nitrogenase enzyme.