Biology: CBSE Sample Question Paper- 1 Notes | Study Sample Papers for Class 12 Medical and Non-Medical - Class 12

Class 12: Biology: CBSE Sample Question Paper- 1 Notes | Study Sample Papers for Class 12 Medical and Non-Medical - Class 12

The document Biology: CBSE Sample Question Paper- 1 Notes | Study Sample Papers for Class 12 Medical and Non-Medical - Class 12 is a part of the Class 12 Course Sample Papers for Class 12 Medical and Non-Medical.
All you need of Class 12 at this link: Class 12

Ques 1: Mention the sites where syngamy occurs in amphibians and reptiles.
Ans:
In amphibians, syngamy occurs in water outside the body of the organism (external fertilization and external development). In reptiles, it occurs inside the body of female (internal fertilization and external development).

Ques 2: State the role of microbes in sewage treatment.
Ans:
Microbes clean sewage water and make it possible for us to use this water again. They effectively use up unwanted nutrients in the system, by metabolizing the solid waste that passes through the treatment plant.

Ques 3: Mention two factors responsible for reduction in biodiversity at high altitudes!
Answer:  
(a) Drop in temperature
(b) Greater seasonal variability

Ques 4: What is plasmid?
Ans: 
Plasmid is an autonomously replicating circular extrachromosomal DNA used as cloning vector.

Ques 5: What are alleles?
Ans: 
The alternative forms of a gene are called alleles.

Ques 6: How does endosperm of angiosperms become triploid
OR
What is emasculation? Explain its importance in hybridisation.
Ans: 
Endosperm of angiosperms develops from the central cell of embryo sac where two polar nuclei fuse to form a secondary nucleus. This diploid nucleus of central cell fuses with one of the two male gametes. The two polar nuclei and one male gamete ruse to form a triploid primary endosperm nucleus (3n). Thus, the endosperm is formed from this triploid nucleus and becomes triploid.
OR
Emasculation is the practice of removal of anthers/stamens from the flower bud before the anther dehisces in a bisexual female flower.
It prevents contamination of stigmas with unwanted pollen grains that can be easily deposited on stigmas.

Ques 7: Name the pioneer and the climax species in a water body. Mention the changes observed in the biomass and the biodiversity of the successive seral communities developing in the water body.
Ans:
(i) Pioneer species in a water body are autotrophic phytoplanktons such as diatoms, unicellular or filamentous algae, flagellates and cyanobacteria. Climax species in a water body are trees.
(ii) Biomass and the biodiversity goes on increasing in the successive seral communities developing in the water body.

Ques 8: What is BOD? What does it mean if a water sample has more BOD?
Ans: 
BOD means the biochemical oxygen demand which represents the amount of dissolved oxygen that would be consumed if all the organic matter in one litre of water were oxidised by microorganisms.
More value of BOD means the water sample is polluted by organic matter.

Ques 9: Mention the effects of nicotine on human body.
Ans: 
Nicotine stimulates adrenal glands to release adrenaline and nor-adrenaline into blood circulation, both of which increase blood pressure and heart beat rate. This lead to increased risk of heart disease.

Ques 10: If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
Ans: 
Cytosine = 20%, therefore Guanine = 20%
According to Chargaffs rule, A+T=100 -(G+C) A + T = 100 - 40.
Since both adenine and thymine are in equal amounts,
Thymine = Adenine

Ques 11: Write a short note on dairy farm management.
Ans: 
Farm management includes the management of animals which provide milk and their products for human consumption. The common dairy animals are cows, buffaloes, sheep and goats. For a good dairy farm management, the animals should be of good breeds which may increase the milk yield and improve the quality of milk. The good quality breeds must be maintained, housed well and fed properly. Their area must be free from accumulation of manure and dirt. The person concerned with milking and handling of milk must follow the sanitary techniques.

Ques 12: What is the difference between homothallic and heterothallic plants?
Ans
: When both male and female reproductive structures are present on the same plant they are called bisexual or homothallic but when male and female reproductive structures are present on different plants they are called unisexual or heterothallic.

Ques 13: Red flowered (RR) plant is crossed with white flowered (rr) plants. The offspring was pink flowered. Explain the genetic phenomenon.
Ans: 
The resultant offspring is of pink flowered plants by using red flowered (RR) with white flowered (rr) plants. It means that neither the red flower colour is dominant over the white flower colour nor the white flower is dominant over red. The heterozygous (Rr) plants were pink coloured. Hence, it indicates the phenomenon of incomplete dominance.
Biology: CBSE Sample Question Paper- 1 Notes | Study Sample Papers for Class 12 Medical and Non-Medical - Class 12

Ques 14: What is meant by semi-conservative mode of DNA replication?
Ans:
A unique property of DNA is that it governs its own synthesis. The copying process of DNA to produce additional DNA molecules is called replication. The two strands of DNA would separate and each strand acts as a template for the synthesis of new complementary strand alongside it. After the completion of replication each DNA daughter molecule would have one parental and one newly synthesized strand and the two daughter DNA molecules are identical to the parent molecule. In each daughter DNA molecule only one parent strand is conserved. This mode of replication is said to be semiconservative.

Ques 15: (i) For producing a recombinant protein (for therapeutic purpose) in large scale, which vector would you choose-a low copy number or hight copy number?
(ii) Would you like to choose an exonuclease enzyme while producing a recombinant DNA molecule?
Ans: 
(i) We choose a high-copy number, because higher the copy number, higher will be the formation of recombinant protein.
(ii) No, as exonuclease acts on the free ends of linear DNA molecule. Therefore, instead of producing DNA fragments with sticky ends, it will shorten or completely degrade the DNA fragment containing the gene of interest, and the circular plasmid (vector) will not get cut as it lacks free ends.

Ques 16: (i) What is seminal plasma? What are its components?
(ii) Where do sperms mature and become motile?
Ans: 
(i) The accessory glands of a male reproductive system secrete a fluid mixture called seminal plasma. It is rich in fructose, calcium and certian enzymes.
(ii) The sperms mature in epididymis. The mature spermatozoa from epididymis pass into the vas deferens. Here, they partly swim and are mainly moved by muscular action of the vas deferens.

Ques 17: Name three incurable sexually transmitted diseases and their causative organisms.
Ans: 


Sexually transmitted disease
Causal agent
(a)Hepatitis-B
Hepatitis-B virus
(b)
Genital herpes
Herpes simplex virus
(c)AIDS
HTV (Human immunodeficiency Virus)


Ques 18: What are the advantages of using biofertilisers in agriculture?
Ans:
Following are the advantages of using biofertilisers in agriculture:
(a) Biofertilisers do not cause any pollution.
(b) These are cheap and economical.
(c) Some of them act as biopesticides also.
(d) In ill-irrigated conditions few biofertilisers can enhance the crop yield.
(e) They improve soil structure and function.
(f) They make available vitamins and other growth promoting biochemicals.

Ques 19: (i) Name the substance used as a medium/matrix in gel electrophoresis.
(ii) Why does DNA move towards the anode in gel electrophoresis?
(iii) Name the compound used for staining the isolated DNA in the gel electrophoresis.
Ans: 
(i) Agarose.
(ii) The DNA fragments are negatively charged so they move towards the positively charged anode.
(iii) Ethidium bromide.

Ques 20: (i) What is cloning vector?
(ii) Explain any two methods of vectorless gene transfer.
Ans:
(i) Cloning vectors are carriers or vehicles of desired DNA fragments which can replicate independently to increase copies of desired genes in the host cell, e.g., plasmids, bacteriophages.
(ii) The two methods of vectorless gene transfer are:
(a) Micro-injection: The technique of introducing foreign gene in a target cell by injecting the DNA directly into the nucleus by micro-needle is called micro-injection.
(b) Electroporation: The process in which transient holes are produced in the plasma membrane of the target cell to incorporate foreign DNA.

Ques 21: (i) Give the scientific name of the soil bacterium which produces crystal (Cry) proteins.
(ii) How are these proteins useful in agriculture?
(iii) What do the differently written terms 'Cry' and ?cry ? represent respectively?
Ans: 
(i) Bacillus thuringiensis.
(ii) These Cry proteins are toxic to certain larvae of insects and thus provide resistance from them. The gene encoding Cry proteins are used in several crop plants (Bt toxin). Such a crop plant is resistant to the particular insect pest.
(iii) Cry represents crystal protein while cry refers to the gene encoding the Cry protein.

Ques 22: What is meant by the term 'hotspots9 in biodiversity? List two criteria used for determining a ?hot spot?. Name two hot spots of India.
Ans: 
A hot spot is an area having endangered endemic species with very high levels of species richness.
Criteria used for determining a hot spot:
(i) Number of endemic species, i.e., species which are not found anywhere else.
(ii) Degree of threat which is measured in terms of habitat loss.
Western Ghats and Eastern Himalayas are two hot spots in India.

Ques 23: What is eutrophication? Explain its consequence on the life of plants and animals in such water bodies.
OR
What is biological magnification? How does DDT as a water pollutant undergo biological magnification?
Ans: 
Eutrophication is excessive growth of algae, plants and animals in water bodies due to the nutrient enrichment, particularly with nitrogen and phosphorus.
Consequences ofeutrophication on the life of plants and animals in such water bodies are as follows:
(a) Presence of large amount of nutrient in such water bodies causes excessive growth of planktonic (freefloating) algae leading to algal bloom. Algal bloom caused deterioration of water quality and fish mortality.
Some of them are toxic to human being and animals.
(b) Growth of water hyacinth (aquatic weed) lead to an imbalance in the aquatic ecosystem.
OR
Biological magnification or biomagnification is the increase in concentration of toxic materials like heavy metals and pesticides at each trophic level of a food chain due to their accumulation.
When DDT was used to control mosquitoes in a lake of USA, 800 times more DDT was found in the phytoplanktons than in the water of the lake. Zooplanktons had about 13 times more DDT than phytoplanktons. It was also observed that the fishes population had 9-40 times more DDT than zooplanktons and fish eating birds had 25 times more DDT than fish.

Ques 24: Kavita was very happy when she gave birth to her first child. But her in-laws were unhappy and blamed on Kavita to give a female child. Kavita tried to conyince them that she had no role in the child's gender. Then Kavita's husband took up the matter and convinced the parents.
(i) What values did Kavita's husband show in the above situation? 
(ii) What governs sex determination in humans? 
(iii) Why can't Kavita be blamed for not giving birth to a male child?
Ans: 
(i) Strong and determined personality with lesponsibility towards the family and respect for elders.
(ii) Sex chromosomes. In human males it is XY and female it is XX.
Human females are homogametic i.e. produces only one type of gamete containing 22+X chromosomes only. Males are heterogametic and produce two types of gametes 22+X and 22 + Y. It is the type of male gamete which determines the sex of the foetus. If X chromosome containing sperm fuses with the egg, it produces a female child whereas if Y chromosome containing sperm fuses with the egg, it produces a male child.
Biology: CBSE Sample Question Paper- 1 Notes | Study Sample Papers for Class 12 Medical and Non-Medical - Class 12

Ques 25: Drawa labelled diagram of the sectional view of a mature pollen grain in angiosperms. Explain the functions of its different parts.
OR
(i) What is the role of cervix of the human female system in reproduction?
(ii) Distinguish between spermatogenesis and oogenesis.
Ans: 

Biology: CBSE Sample Question Paper- 1 Notes | Study Sample Papers for Class 12 Medical and Non-Medical - Class 12
Functions of the parts of Pollen grains: A mature pollen grain has two layered wall-the outer exine and the inner intine. The wall encloses a large vegetative cell containing vegetative nucleus and a lenticular generative cell.
Their functions are as follows:
Exine: The outer thick exine layer is made up of sporopollenin which is resistant to physical and biological decomposition. It provides protection during the hazardous journey of pollen from anther to the stigma. There are one or many germpores on the pollen surface which are directly or indirectly associated with its germination.
Intine: The intine is pecto-cellulosic in nature. It is associated with the formation of pollen tube.
Vegetative cell: The vegetative cell is large and contains abundant food reserve. It has a large vegetative nucleus. The function of vegetative cell is to provide the medium for the movement of male gametes in pollen tube.
Generative cell: The generative cell cytoplasm is highly reduced but it contains the usual cell organelles. It divides mitotically to produce two functional male gametes.
OR
(i) Cervix helps in regulating the passage of sperms into the uterus and forms the birth canal to facilitate parturition.
(ii)

S.No.SpermatogenesisOogenesis
(a)It is the process of formation of haploid spermatozoa from diploid male germ cells of the testes.It is the process of formation of haploid ova from the gamete mother cells (oogonia) in the ovary.
(b)It occeurs in testes.It occurs in ovaries.
(c)Spermatogoina chamges to primaryOogonia changes to primary oocyte.
(d)A primary spermatocyte divides to from two secondary spermatocytes.A primary oocyte divides to form one secondary oocyte and a polar body.
(e)
A secondary spermatocyte divides to from two spermatids.A secondary oocyte divides to from one ovum and a polar body.
(f)No polar body is formed.Polar bodies are formed.
(g) Four spermatozoa are produces.
One ovum/egg is produced.


Ques 26: In garden pea (Pisum sativum) a plant with red flowers was crossed with a plant with white flowers. Work out the possible genotypes and phenotypes of Fi and F generations. State any one of Mendel's law that could be derived from this cross.
OR
Mention any two autosomal genetic disorders with their symptoms.
Ans:

 Biology: CBSE Sample Question Paper- 1 Notes | Study Sample Papers for Class 12 Medical and Non-Medical - Class 12
Mendel's law of dominance
The hybrid is heterozygous containing both alternative alleles (R and r) but only one trait, i.e., red colour appeared and white colour trait is suppressed in generation. This explains Mendel's law of dominance.
OR
The autosomal genetic disorders are
(a) Down's Syndrome - It is caused due to an additional copy of chromosome number 21 or trisomy of chromosomes 21.
Its symptoms are:
(i) The diploid number of chromosomes in this case is 47. (45A+XX/XY)
(ii) Short statured, face rounded and flat, mouth open, tongue furrowed and saliva keeps dribbing.
(iii) Simian crease is prominent in the middle of the plam. Many loops on finger tips.
(iv) Mental and psychomotor development retarded. IQ is less than 25 (idiotic).
(b) Phenylketonuria - It is an inborn error of metabolism and is inherited as autosomal recessive trait.
The affected individual lacks an enzyme called phenylalanine hydroxylase that converts the ammo acid phenylalanine into tyrosine in liver. This phenylalanine is accumulated and converted into phenyl pyruvic acid and other derivatives in brain.
The symptoms are mental retardation, hypopigmentation of skin and eczema. The damage can be restricted if the child is fed on low-phenylalanine diet.

Ques 28: (i) How normal cells get transformed into cancerous neoplastic cells? Mention the difference between viral oncogenes and cellular oncogens.
(ii) Write a short note on detection of cancer.
OR
Biology: CBSE Sample Question Paper- 1 Notes | Study Sample Papers for Class 12 Medical and Non-Medical - Class 12
(i) The diagram given above is that of a typical biogas plant. Identify A, B and C. Explain the sequence of events occurring in it.
(ii) Name the diagram given above is that of a typical biogas plant.
Ans: 
(i) Normal cells get transformed to cancerous neoplastic cells due to the induction by physical, chemical or biological agents called carcinogens.
Viral oncogenes: These are the viral genes, which cause cancer.
Cellular oncogenes: These are the genes in normal cells, which cause a cell to become cancerous under certain conditions.
(ii) Cancer detection is considered to be the first step towards treatment. Its early detection is essential for its cure.
Biopsy - A piece of the suspected tissue cut into thin sections is stained and examined under microscope.
Computed Tomography - It uses X-ray to generate a three-dimensional image of the inside of an object.
MRI - It uses strong magnetic fields and non-ionising radiations to accurately detect pathological changes in the living tissue.
Antibodies against cancer-specific antigens are also used for the detection of certain cancers.
OR
(i) A - Sludge tank; B - Gas holder and C-Charge pit.
The biogas plant tank is fed with slurry of dung. A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity of methanogens like Methanobacterium. Methanogens grow anaerobically on cellulosic material in cowdung to produce large amount of methane, and H. The biogas plant has an outlet, which is connected to a pipe to supply biogas. The spent slurry is removed through another outlet and is used as fertiliser
(ii) Indian Agricultural Research Institute (IARI) and Khadi & Village Industries Commission (KVIC).

The document Biology: CBSE Sample Question Paper- 1 Notes | Study Sample Papers for Class 12 Medical and Non-Medical - Class 12 is a part of the Class 12 Course Sample Papers for Class 12 Medical and Non-Medical.
All you need of Class 12 at this link: Class 12

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