We have provided Class 12 Biology Sample Paper as per the latest CBSE examination pattern for the current academic year. The following CBSE Sample Papers for Class 12 Biology has been prepared based on the guess papers issued recently. Students will be able to practice these papers and get good marks in upcoming Biology exams for Class 12.
CBSE Sample Papers for Class 12 Biology
|Term 2 Sample Papers|
|Class 12 Biology Sample Paper Term 2 With Solutions Set A|
Class 12 Biology Sample Paper Term 2 With Solutions Set A
1. A heavily bleeding and bruised road accident victim was brought to a nursing home. The doctor immediately gave him an injection to protect him against a deadly disease.
(i) Write what the doctor injected into the patient’s body.
(ii) How do you think this injection would protect the patient against the disease? Name the disease against which this injection was given and the kind of immunity it provides.
Answer : (i) The patient was injected with anti Tetanus serum.
(ii) If a person is infected with some deadly microbes to which quick immune response is required as in tetanus, we need to directly inject the preformed antibodies, or antitoxin (a preparation containing antibodies to the toxin).
2. Give examples to prove that microbes release gases during metabolism.
Answer : • The puffed-up dough, of dosa and idli due to the production of CO2 gas during fermentation by bacteria.
• The dough used for making bread is fermented using baker’s yeast (Saccharomyces cerevisiae).
• The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii.
Name the two different categories of microbes naturally occurring in sewage water. Explain their role in cleaning sewage water into usable water.
Answer : Use of aerobic microbes reduces the BOD (biochemical oxygen demand) of the effluent. In large tanks calledana erobic sludge digesters other kinds of anaerobic bacteria, digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide[ biogas] The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams.
3. Identify the substance depicted in the figure. What is its source and its ill effects on human body?
Answer : Morphine. Heroin, commonly called smack is chemically diacetylmorphine which is a white, odourless, bitter crystalline compound. This is obtained by acetylation of morphine (Figure), which is extracted from the latex of poppy plant Papaver somniferum. Generally taken by snorting and injection, heroin is a depressant and slows down body functions. Opioids are the drugs, which bind to specific opioid receptors present in our central nervous system and gastrointestinal tract.
4. (i) How do organic farmers control pests? Give two examples.
(ii) State the difference in their approach from that of conventional pest control methods.
Answer : (i) The organic farmer, works to create a system where pests are not eradicated, but instead are kept at manageable levels by a complex system of checks and balances within an ecosystem.
Eradication of the pests is not only possible, but also undesirable, they are part of a food chain and its predators may be desirable to us. Examples: use of Nucleopolyhedrovirus with respect to pest management, the bacteria
Bacillus thuringiensis to control butterfly caterpillars, use of the fungus Trichoderma in the treatment of plant disease and several plant pathogens.
(ii) This is a holistic approach that seeks to develop an understanding of the webs of interaction between the myriad of organisms that constitute the field fauna and flora. The ‘conventional’ farming practices which often use chemical methods to kill both useful and harmful life forms indiscriminately.
5. What are sacred groves? What is their role in conservation? Why are sacred groves highly protected?
Answer : India has also a history of religious and cultural traditions that emphasized protection of nature. In many cultures, tracts of forest were set aside, and all the trees and wildlife within were venerated and given total protection. Such sacred groves are found in Khasi and Jaintia Hills in Meghalaya, Aravalli Hills of Rajasthan, Western Ghat regions of Karnataka and Maharashtra and the Sarguja, Chanda and Bastar areas of Madhya Pradesh. In Meghalaya, the sacred groves are the last refuges for a large number of rare and threatened plants.
6. Study the graph given alongside and answer the questions that follow.
(i) Write the status of food and space in the curves (A) and (B)
(ii) In the absence of predators, which one of the two curves would appropriately depict the prey population?
(iii) Time has been shows on x-axis and there is a parallel dotted line above it. Give the significance of this dotted line.
Answer : (i) The status of food and space in curves ‘A’ is unlimited resources, while in curve ‘B’ the sources of food and space are limited.
(ii) In the absence of predators, the curve ‘B’ would appropriately depict the competition for limited food and shelter resources within the prey population. But if food and shelter is also unlimited that is there is no environmental resistance, Curve A will depict the growth curve.
(iii) The dotted line in the above graph represents the carrying capacity (K). The carrying capacity signifies the limit of habitat, i.e. limited resources in a given habitat to support growth upto a certain level beyond which no further growth can take place.
(i) Explain giving reasons why the tourists visiting Rohtang Pass or Mansarovar are advised to resume normal active life only after a few days of reaching there.
(ii) It is impossible to find small animals in the polar regions. Give reasons.
(i) Tourists visiting to Rohtang Pass near Manali (> 3500 m) may suffer from altitude sickness. They resume normal active life only after a week because in low atmospheric pressure at high altitudes, the body does not get enough oxygen. Gradually, the body compensates low oxygen availability by increasing red blood cell production.
(b) Decreasing the binding affinity of haemoglobin.
(c) Increasing the breathing rate.
(ii) Small animals have a large surface area relative to their volume. So, they tend to lose body heat very fast during cold conditions. They need to spend more energy to generate body heat. Due to this smaller animals are rarely found in polar regions.
7. Name the following with respect to ringworm.
(i) Causative organism and the target organ
(ii) Any two symptoms
(iii) Optimal conditions for its spread and mode of transmission.
Answer : (i) Fungi belonging to the genera Microsporum, Trichophyton and Epidermophyton
(ii) Appearance of dry, scaly lesions on various parts of the body such as skin, nails and scalp are the main symptoms of the disease. These lesions are accompanied by intense itching.(iii) Heat and moisture help these fungi to grow, which makes them thrive in skin folds such as those in the groin or between the toes. Ringworms are generally acquired from soil or by using towels, clothes or even the comb of infected individuals.
Name the following with respect to common cold.
(i) Causative organism and the target organ
(ii) Any two symptoms
(iii) Mode of transmission
(i) Rhino viruses infect the nose and respiratory passage but not the lungs.
(ii) The common cold is characterized by nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness, etc., which usually last for 3-7 days.
(iii) Droplets resulting from cough or sneezes of an infected person are either inhaled directly or transmitted through contaminated objects such as pens, books, cups, doorknobs, computer keyboard or mouse, etc., and cause infection in a healthy person.
8. (i) Name the causative organisms for the following diseases.
(a) Elephantiasis (b) Ringworm (c) Amoebiasis
(ii) How can public hygiene help control such diseases?
Answer : (i) (a) Elephantiasis: Wuchereria bancrofti
(b) Ringworm: Microsporum, Trichophyton and Epidermophyton
(c) Amoebiasis: Entamoeba histolytica
(ii) Public hygiene can help to control the water and food borne diseases such as typhoid, ascariasis and amoebiasis and in certain cases air borne diseases too.
9. Describe any three potential applications of genetically modified plants.
Answer : GM plants have been useful in many ways.
Genetic modification has:
(i) Made crops more tolerant to abiotic stresses (cold, drought, salt, heat).
(ii) Reduced reliance on chemical pesticides (pest-resistant crops).
(iii) Helped to reduce post harvest losses.
(iv) Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).
(v) Enhanced nutritional value of food, e.g., vitamin ‘a’ enriched rice.
(vi) In addition to these uses, GM has been used to create tailor-made plants to supply alternative resources to industries, in the form of starches, fuels and pharmaceuticals. [any three]
10. List the different ways by which organisms cope or manage with abiotic stresses in nature. Explain any three ways.
Answer : Organisms cope up with abiotic stress by:
(i) Regulating: Some organisms maintain homeostasis by physiological and behavioural meAnswer : They are called regulators, e.g.
• In summers, when outside temperature is more, we sweat profusely that results in evaporative cooling to bring down the body temperature.
• In winters, when temperature is low, we shiver (a kind of exercise) that produces heat and raise the body temperature.
(ii) Conforming: Organisms that cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. Such animals are called conformers. For example, small animals have larger surface area relative to their volume. They lose body heat very fast in low temperature. So, they expend energy to generate body heat through metabolism for adjusting.
(iii) Migrating: The temporary movement of organisms from the stressful habitat to a more hospitable area and return when favourable conditions reappear is called migration. The long distance migration is very common in birds.
11. What is so special about tropics that might account for their greater biological diversity?
Answer : Some important hypotheses are:
(a) Speciation is generally a function of time, unlike temperate regions subjected
to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification,
(b) Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialization and lead to a greater species diversity and
(c) There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.
12. How is Gene Transfer carried out?
Answer : It is carried out by two methods, vector transfer and direct transfer.
(i) Vector Transfer: rDNA is present in the form of plasmid, virus, cosmid or artificial chromosome. It is introduced into host cell by adding it into culture of plasmid free bacteria or animal cells. The host cells are made permeable through electroporation or chemically. Once inside the host cell, the recombinant DNA begins to multiply and form the desired product.
(ii) Direct or Vectorless Transfer: The desired gene as well as recombinant DNA can be passed into plant, animal or human cells through:
(a) Microinjection: by means of micropipettes
(b) Particle or gene gun: where tungsten or gold particles coated with desired genes are bombarded into the cells with great force. Instead special sprays are also used for this.
13. Reducing environmental pollution through biotechnology
Genetic manipulation made it possible to obtain microorganisms or specific enzymes for the degradation and metabolism of toxic residual products. In the waste processing sector , this use of manipulated or selected microorganisms or theenzymes they produce is called bioremediation.
On the other hand, different industrial sectors are currently applying biotechnological techniques to replace industrial techniques which are dangerous for the environment or which pollute it. The in situ use of microorganisms or enzymes is a cleaner technique or less polluting. There is thus reduction of harmful effects of biodegradable waste, as well as its quantity, but also very often reducing water costs and energy.
(i) Cite two current applications of biotechnology which involve the use of genetic engineering for environmental conservation.
(ii) Give four examples of bioremediation techniques.
(iii) List any two advantages of using biotechnology to treat industrial organic waste like waste from potato wafers manufacturing or molasses in sugar industry by microorganism avoiding chemicals.
Answer : (i) (a) Treatment and reuse of waste products via biotechnological methods (bioremediation).
(b) Obtaining fuel by degradation of organic raw material as an alternative to petroleum by using biotechnology.
(ii) Bioremediation and cleaner technologies-
(a) methane and gas from urban solid waste
(b) digestion of plant waste via bacteria
(c) biological purifiers
(d) obtaining biomass from organic by-products
(e) digestion of oil slicks via microorganisms [any four]
(iii) (a) Cleaner environment
(b) Obtaining some useful product, for example, spirulina [for nutrition] can be cultured in these waste water or they can be used for making biogas.
Cry is a family of proteins originating from strains of the bacterium Bacillus thuringiensis. There are more than 200 different types of Bt toxins, each affecting different types of insects. The cotton plants are genetically modified by the addition of genes encoding these Cry group protein crystals. When ingested by insects, the Cry toxins are dissolved and activated by the high pH environment of the animal’s gastrointestinal system. In the midgut, the activated Cry molecules bind to cadherin-like proteins on cells comprising the brush border membrane. With the formation of Cry ion channels and the subsequent efflux of potassium ions, the affected epithelial cells lyse and die. The Bt cotton plants are genetically modified by the addition of genes encoding this endotoxin so that the insect larva on consuming cells of such a GM plant will not survive.
(i) Which vector is used to clone the cry gene?
(ii) Name any two components of host cell required by the vector DNA for cloning foreign gene in it.
(iii) Enlist any two areas where genetic modifications of plants had been useful.
Answer : (i) Ti plasmid. Ti plasmid can be used as good cloning vector after the removal of tumor causing genes. rDNA carrying Cry gene can be inserted into the bacterium by the use of Biolistic method
(ii) rDNA multiples inside the host with the help of
(a) Ori (b) DNA polymerase of the host
(iii) • Reducing use of chemical pesticides to grow a pest free crop like Bt cotton, GM tobacco to silence nematode specific genes to check spread of root knot disease caused by nematode Meloidegyne incognitia
• Nutrient rich plant product like Golden rice rich in vitamin A
• Plant products with higher shelf life e.g, flavr savr tomato
• Increased resistance to abiotic stresses in some crop plants