RBSE 12th Biology Board Model Paper 2022 with Answers in English 

Students must start practicing the questions from RBSE 12th Biology Model Papers Board Model Paper 2022 with Answers in English Medium provided here.

RBSE Class 12 Biology Board Model Paper 2022 with Answers in English

Section – A

Question 1.
Choose the correct answer of the following questions and write in the answer-book.
(i) Which of the following organism shows parthenogenesis ? [1]
(A) Earthworm
(B) Sponge
(C) Honeybee
(D) Ascaris.
Answer:
(C) Honeybee

(ii) How many nucleus and cells are present inatypical mature angiosperm endosperm ? [1]
(A) 7, 7
(B) 8, 8
(C) 8, 7
(D) 7, 8.
Answer:
(C) 8, 7

(iii) Which organism shows XO type of sex determination? [1]
(A) Human
(B) Drosophila
(C) Birds
(D) Grasshopper
Answer:
(D) Grasshopper

(iv) By which bond Nitrogen base is attached to pentose sugar in the molecular structure of DNA? [1]
(A) Hydrogen
(B) Glycosidic
(C) Phospho-ester
(D) Phospho-di-ester.
Answer:
(B) Glycosidic

(v) Which of the following is an example of autoimmune disease ? [1]
(A) AIDS
(B) Rheumatoid arthritis
(C) Cancer
(D) Elephantiasis.
Answer:
(B) Rheumatoid arthritis

(vi) Which disease is an example of non-contagious disease ? [1]
(A) Common cold
(B) Ringworm
(C) Cancer
(D) Typhoid.
Answer:
(C) Cancer

(vii) Which of the following variety of wheat is leaf and stripe rust resistant ? [1]
(A) Sharbati Sonar
(B) Sonalika
(C) Kalyan Sona
(D) Himgiri.
Answer:
(D) Himgiri.

(viii) Which enzyme is used to join DNA fragments ? [1]
(A) DNA ligas
(B) DNA polymerase
(C) DNA helicase
(D) Restriction endonuclease.
Answer:
(A) DNA ligas

(ix) The cry genes incorporated in Bt cotton are- [1]
(A) Cry I Ac & Cry II Ab
(B) Cry I Ac & Cry I Ab
(C) Cry II Ac & Cry I Ab
(D) Cry II Ac & Cry II Ab.
Answer:
(A) Cry I Ac & Cry II Ab

Question 2.
Fill in the blanks-
(i) The method of producing thousands of plants through tissue culture is called ……………. [1]
Answer:
Micropropogation.

(ii) The total of number of biodiversity hotspot in the world ……… [1]
Answer:
34.

(iii) …………. make up very large portion of human genome. [1]
Answer:
Repetitive sequences.

(iv) Sedimentary nutrient cycle reservoir is located in Earth’s …………… [1]
Answer:
Crust.

Question 3.
Give the answer of the following questions in one word or in one line-
(i) Define linkage. [1]
Answer:
The tendency of the genes on the same chromosome to link together is called linkage.

(ii) Write the name of a disease caused by point mutation. [1]
Answer:
Sickle cell anemia

(iii) Write the definition of immunity. [1]
Answer:
Immunity is the ability of an organism to resist the development of a disease.

(iv) Which part of the plant best suited for making virus free plants, and why? [1]
Answer:
Meristem (apical and axillary) is free of virus. So it is best suited for making virus free plants.

(v) Define gel electrophoresis. [1]
Answer:
The cutting of DNA by restriction endonucleases results in the fragments of DNA. These fragments can be separated by a technique known as gel electrophoresis.

(vi) Define transgenic animal. [1]
Answer:
Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals.

(vii) What do you understand by net primary productivity? [1]
Answer:
Net primary productivity is the remaining biomass or the energy left after utilization of producers.

(viii) Write one example of ex-situ and in-situ conservation. [1]
Answer:
Ex-situ-Botanical gardens
In-situ-National parks.

Section – B

Short Answer Questions (Answer word limit 50 word)

Question 4.
Write the name of any three methods to assist infertile couples to have children. [1.5]
Answer:

• In vitro fertilization (IVF) or test tube baby programme.
• ZIFT (Zygote Intra fallopian transfer) and IUT (Infra Uterine transfer.
• Gamete Intra Fallopian transfer (GIFT)

Question 5.
Suggest three measures one has to take to prevent from contracting sexually transmitted diseases. [1.5]
Answer:

• Avoid sex with unknown/multiple partners.
• Always use condoms during coitus.
• Use sterlised needles and syringes.

Question 6.
Define somatic hybridization with examples. [1.5]
Answer:
The process of fusion of protoplast of somatic cells obtained from different varieties or species of plant on a suitable nutrient medium in vitro to develop a hybrid is known as somatic hybridization.

Pomato is a somatic hybrid produced by the fusion of tomato and potato protoplasts.

Question 7.
What do you understand by single cell protein ? Explain with example. [1.5]
Answer:
It refers to the sources of mixed proteins extracted from pure or mixed culture of organisms or cells. SCP(single cell protein) act as a supplement or alternative source of protein that is not supplied by the traditional or conventional agriculture production.

Following microbes are grown commercially as a source of SCP.

• Cynobacteria-Spirulina
• Algae-Chlorella
• Yeasts-Sachharomyces cerevisiae.

Question 8.
What is origin of replication ? [1.5]
Answer:
This is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence is also responsible for controlling the copy number of the linked DNA. So, if one wants to recover many copies of target DNA it should be cloned in a vector whose origin suport high copy number.

Question 9.
What do you understand by bioreactor? [1.5]
Answer:
Bioreactors are the large volume vessels approximately (100-1000 L) in which raw materials are biologically converted into specific products, individual enzymes etc., using microbial. plant, animal or human cells. Abiorcactor provides the optimal conditions for achieving the desired products by providing optimum growth conditions like temperature. pH. substrate. salts, vitamins and oxygen.

Question 10.
Write any three advantages of production of genetically modified crops. [1.5]
Answer:
Following are the advantages of production of genetically modified crops-

• Crop became more tolerant to abiotic stresses like cold, drought, salt and heat.
• Dependence on chemical pesticides has reduced, i.e., pestresistant crops.
• It helped to reduce post-harvest losses.
• Efficiency of mineral usage increased in plants, preventing early exhaustion of fertility of soil.
• Enhanced nutritional value of food, e.g., Vitamin-A enriched rice (Golden rice).

Question 11.
Crystal of BT toxin produced by some bacteria, why these crystal do not kill the bacteria themselves? [1.5]
Answer:
Bacteria Bacillus thuringiensis forms protein crystals (Cry) during a particular phase of their growth. These crystals contain a toxic insecticidal protein. But this toxin does not kill the Bacillus (bacterium), because Bt toxin protein exists as inactive protoxins but once an insect digests the inactive toxin, it is converted into its active form due to the alkaline pH of the gut which solubilises the crystals.

Question 12.
Define primary productivity. [1.5]
Answer:
Productivity is the rate of biomass production per unit area over a time period. It is expressed in terms of g^-2 yr^-1 or (kcal m^-2) yr^-1

Primary productivity is the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis.

Question 13.
Write differences between upright and inverted ecological pyramid. [1.5]
Answer:
Differences between upright and inverted pyramid are-

Upright pyramid	Inverted pyramid
1. In this type of pyramid the number and biomass of organisms at producer level is high, which keeps on decreasing at each trophic level.	1. In this type of pyramid the number and biomass of organisms at producer organisms at producer level is lowest and keeps on increasing at each trophic level.
2. The base bar comprises of producers in large number.	2. The base bar comprises of producers in small number.
3. Energy pyramid is always upright.	3. Pyramid of number and pyramid of biomass can be inverted.

Question 14.
Write the name of all important components of biodiversity. [1.5]
Answer:
Following are the important components of biodiversity-
(i) Genetic diversity-A single species shows diversity at the genetic level over its distributional rage. For example, the genetic variation showed by the plant Rauwolfia vomitoria growing in the different Himalayan ranges might be in terms of the potency and concentration of reserpine.

(ii) Species diversity-It is the diversity at the species level or the measure of the variety of species and their relative abundance with the region. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

(iii) Ecological diversity-At the ecosystem level, India shows diversity with its deserts, rainforests, mangroves, coral reefs and alpine meadows.

Question 15.
Why is bio-diversity important for functioning of eco-system? [1.5]
Answer:
All the living organisms are so closely interlinked (through food chain, food webs, material cycling, energy flow etc.) that destruction of one kind of wildlife on the earth may upset the ecological balance in nature e.g. killing of carnivores will increase the population of herbivores which will damage the vegetation and disturb the ecological balance. Species of plants and animals keep a check on their numbers through food chains, so the wildlife helps to preserve the environment as a self sustaining system. Thus, ecosystems offer support and provide services like soil fertility, plant pollinators, predators, decomposers, purification of air and water, management of floods and drought and other environmental disasters.

Bio-diversity is required for maintaining and sustainable use of goods and services from eco-systems.

Section – C

Long Answer Questions (Answer word limit 100 word)

Question 16.
Write the definition of external fertilisation. Write the two differences between gametogenesis and embryogenesis. [1 + 2 = 3]
Answer:
External fertilization-In majority of aquatic organisms, e.g., algae, fish and in amphibians, the process of fertilization takes place outside the body of organism, i.e., in water. This type of gametic fusion is called external fertilization.

To enhance the chances of fertilization, the organisms exhibiting external fertilization discharge a large number of gametes in water, e.g. Bony fishes, frogs etc. By this process, a large number of offsprings are produced with the disadvantage of them being volnerable to predator. This threatens their survival upto adulthood.

Differences between Gametogenesis and Embryogenesis:

Gametogenesis	Embryogenesis
1. It is the process of development of gametes from the meiocyctes.	1. It is process of development of gametes from the zygote.
2. It is a pre-fertilization event.	2. It is a post-fertilization event.
3. It involves meiosis.	3. It involves mitosis and cell differentiation.

Or

Write the definition of fertilization. Write the two differences between Asexual and Sexual reproduction. [1 +2 = 3]
Answer:
The process of fusion of male gamete with the female gamete is called fertilization or syngamy. It results in the formation of a diploid cell called zygote.

Differences between Asexual and Sexual Reproduction:

Asexual reproduction	Sexual reproduction
1. It is always uniparental and does not involve gamete formation.	1. It is generally biparental and always involves the formation and fusion of gametes.
2. It involves only mitotic cell division.	2. It involves meiotic division during gamete formation and mimotic division during the development of zygote.
3. It does not contribute to evolution.	3. It contributes to evolution by introducing variations in the offsprings.
4. Daughter individuals are genetically identical to parent and to each other.	4. Daughter individuals are genetically different from their parent and also from each other.
5. It causes rapid increase in population size.	5. It causes slow increase in population size.

Question 17.
Write the reason and two symptoms of Down’s syndrome chromosomal disorder. [1 + 2 = 3]
Answer:
Down’s syndrome occurs due to the presence of an additional copy of chromosome (trisomy of 21st chromosome) in humans.

Symptoms-

• Individuals are short statured with small, round head and furrowed tongue and partially open mouth.
• Palm is broad with characteristic palm crease.
• Slow mental, physical and psychomotor development.

Or

Write the reason and two symptoms of turner’s syndrome chromosomal disorder. [1 + 2 = 3]
Answer:
It is a disorder which is caused due to the absence of one of the X-chromosome, i.e. 45 with XO.
Symptoms-

• Individuals have inasculine development but feminine characters like development of breasts (gynaecomastia) etc.
• Poor beard growth and feminine pitched voice.
• Such unclear individuals are sterile.

Question 18.
Write the name of water born diseases and what measures would you take to prevent it? [1 + 2 = 3]
Answer:
Typhoid is the water born disease. Causatine agent is bacterium Salmonella typhi. It enters the small intestine through contaminated water and food and migrate to other organs of the body through blood.

Prevention-

• Proper sanitation of human feces.
• Screening of water and food sources.
• TAB vaccine provides immunity for about 3 years.
• Typhoral-oral vaccine.
• Chloramphenicol is the standard drug against typhoid. Ampicillin and chloromycetin are also effective.

Or

Write the malaria pathogen and what measure would you take to prevent it? [1 + 2 = 3]
Answer:
Causative agent of malaria is Plasmodium species of protozoan. Its transmitting agent is female Anopheles mosquito that transfers the sporozoites of Plasmodium. Different species of Plasmodium (P. vivax, P. malariae and P. falciparum) are responsible for different types of malaria.

Prevention:

• Wire-gauzing of doors, windows etc. to check entry of mosquitoes.
• Use of insect-repellents to prevent mosquito-bite.
• Sleeping under mosquito-nets.
• Killing of mosquito larvae by filling small sized ditches etc. with soil; or sprinkling kerosine oil on large sized water body or introducing larvicidal fishes, birds and plants like Utriculeria.
• Killing of adult mosquitoes by spraying insecticides like D.D.T. and B.H.C.

Section – D

Essay Type Question (Answer word limit-100 word)

Question 19.
What is triple fusion ? Where and how does it takes place ? Draw a labelled diagram of a fertilized embryo sac. [1 + 1 + 2 = 4]
Answer:
The most important and unique characteristic feature of angiosperms is the participation of both male gametes in the act of fertilization. The pollen tube releases the two male gametes into the cytoplasm of one of the synergids, then the penetrated synergid starts degenerating. One male gamete fuses with the egg cell to form a diploid (2n) zygote. This process is called zyngamy or true fertilization. The diploid zygote finally develops into embryo. The second male gamete fuses with the two polar nuclei or secondary nucleus in the central cell to form the triploid primary endosperm nucleus. This process is called triple fusion as three haploid nuclei are involved in the fusion. After triple fusion, the central cell becomes the primary endosperm cell, which gives rise to the endosperm.

Or

Why is an apple called a false fruit ? Which part(s) of the flower forms the fruit ? Draw diagram of false fruit of apple. [1 + 1 + 2 = 4]
Answer:
A fruit is formed after fertilisation as a result of cell division and differentiation in the ovary, i.e. a ripened ovary forms a fruit. The wall of the ovary develops into the fruit wall called pericarp, which may be fleshy or leathery or dry.

The fruit develop from the ovary of a flower not associated with any non-carpellary part is termed as true fruit (Mango). The other floral parts degenerate and fall-off. The fruit derived from ovary along with other accessory floral parts like Thalamus is called false fruit (Apple). Apple is called a false fruit because it develops from the thalamus instead of ovary (thalamus is the enlarged structure at the base of the flower).

Question 20.
Define DNA. Write the features of the double helix structure of DNA. Draw a labelled diagram of DNA double helix. [1 + 1 + 2 = 4]
Answer:
DNA is a long polymer of dexoxyribonucleotides and it acts as a genetic material in most organisms.

Features of the Double Helix Structure of DNA:
Watson and Crick worked out the first correct double helix model of DNA, which explained most of its properties. The salient features of double helix structure of DNA are as follows-
(i) DNA is made up of two polynucleotide chains. The backbone is constituted by sugar phosphate, while the nitrogenous bases project inwards.
(ii) The two chains have anti-parallel polarity, i.e. when one chain has 3′ → 5′ polarity, the other has 5′ → 3′ polarity.
(iii) The bases in two strands are paired through hydrogen bonds (H-bonds) to form base pairs.
(a) Adenine is bonded with thymine of the opposite strand with the help of two hydrogen bonds.

Fig. Structure of a DNA : (a) Watson and Crick model of double helix and (b) Duble-stranded polynucleotide chain sequence showing hydrogen bonds
(b) Guanine is bonded with cytosine of the opposite strand with the help of three hydrogen bonds. So, a purine bonds with a pyrimidine always. Thus, maintaining a uniform distance between the two strands of the helix.
(iv) The two polypeptide chains are coiled in a right-handed fashion. Pitch of the helix is 3.4 nm or 3.4 × 10^-9. Number of base pairs in each turn is 10. Distance between a base pair in a helix is 0.34 nm.
(v) Percentage calculation of bases is done by A + T = 100 – (G + C)
(vi) The plane of one base pair stacks over the other in double helix. This provides the stability to the helical structure, in addition to H-bond.

Or

Define the packaging of DNA helix. Write the biochemical characterization of transforming principal. Draw a labelled diagram of nucleosome. [1 + 1 + 2 = 4]
Answer:
Packaging of DNA Helix The length of DNA in humans can be calculated as : Distance between two consecutive base pairs is 0.34 nm = 0.34 × 10^-9 m

Total number of base pairs in a DNA helix in a typical mammalian cell = 6.6 × 10⁹
∴ Length of this DNA double helix = 6.6 × 10⁹ × 0.34 × 10^-9 m = 2.2 m (approx.)

Thus, we see that, the length of DNA is far greater than the dimension of a typical nucleus, which is approx 10-6m in diameter. Therefore, there must be some special arrangement to accommodate such a long polymer in a cell of both prokaryotes and eukaryotes.

Transforming Principle:
Frederick Griffith carried out a series of experiments with Streptococcus pneumoniae (a bacterium that cause pneumonia). He observed that when these bacteria (Streptococcus pneumoniae) where grown on a culture plate, some of them produced smooth, shiny colonies (S-type), whereas the others produced rough colonies (R-type).

This difference in appearance of colonies (smooth/rough) is due to the presence or absence of mucus (polysaccharide) coat on S-strains, but not on R-strains.

In his experiments, he first infected two separate groups of mice. The mice that were infected with the S-strain died from pneumonia as S-strains are the virulent strains causing pneumonia.

S-strain (virulent strain) → Injected into mice → Mice died. The mice that were infected with the R-strain did not develop pneumonia and they lived.

R-strain (non-virulent strain) → Injected into mice-Mice lived. In the next set of experiments. Griffith killed the bacteria by heating them. The mice that were injected with heat-killed Strain bacteria did not die and lived.

S-strain (heat killed) → Injected into mice → Mice lived. Whereas, on injecting a mixture of heat-killed S-strain and live R-strain bacteria, the mice died Moreover, living Sbacteria was recovered from the dead mice.
S-strain (heat killed) + R-strain (live) → Injected into mice → Mice died.

From all these observations Griffith concluded that the live R-strain bacteria, had been transformed by the heat-killed S-strain bacteria, i.e. some ‘transforming principle’ had transferred from the heat-killed S-strain, which helped the R-strain bacteria to synthesise a smooth polysaccharide coat and thus, become virulent. This must be due to the transfer of the genetic material. However, he was not able to define the biochemical nature of genetic material from his experiments.

Biochemical Characterisation of Transforming Principle:
Oswald Avery, Colin MacLeod and Maclyn McCarty worked to determine the biochemical nature of ‘transforming principle’ in Griffth’s experiment in an in vitro system. Prior to this experiment, the genetic material was thought to be protein.

During this experiment purified biochemicals (i.e. proteins, DNA, RNA, etc.) from the heat-killed S-cells were taken, to observe which biochemicals could transform live R-cells into S-cells. They discovered that DNA alone from heat-killed S-type bacteria caused the transformation of non-virulent Rotype bacteria into S-type virulent bacteria.

They also discovered that protein-digesting enzymes (proteases) and RNA digesting enzymes (RNase) did not inhibit this transformation. This proved that the transforming substance was neither protein nor RNA. DNA-digesting enzyme (DNase) caused inhibition of transforination, which suggests that the DNA caused the transformation. Thus, these scientists came to the conclusion that DNA is the hereditary material. But still, not all biologists were convinced.