RBSE 12th Biology Model Paper Set 7 with Answers in English

Students must start practicing the questions from RBSE 12th Biology Model Papers Set 7 with Answers in English Medium provided here.

RBSE Class 12 Biology Model Paper Set 7 with Answers in English

Time : 2.45 Hours
Maximum Marks : 56

General Instruction to the Examinee:

1. Candidate must write first his/her Roll No. on the question paper compulsorily.
2. All the questions are compulsory.
3. Write the answer to each question in the given answer book only.
4. For questions having more than one part the answers to those parts are to be written together in continuity.
5. If there is any error/difference/contradiction in Hindi & English version of the question paper, the question of the Hindi version should be treated valid.

Section – A

(1 Mark)

Question 1.
Select the correct option of the following questions and write in notebook. (1 × 9 = 9)
(i) External fertilization is found in which of the following? [1]
(a) Reptiles
(b) Birds
(c) Amphibians
(d) Protozoans
Answer:
(c) Amphibians

(ii) When pollen tube enters through integument, this process is called: [1]
(a) mesogamy
(b) porogamy
(c) chalazogamy
(d) pseudogamy
Answer:
(a) mesogamy

(iii) The term crossing over was coined by: [1]
(a) Johannsen
(b) Mendel
(c) Morgan
(d) Jenssen
Answer:
(c) Morgan

(iv) Which of the following RNAs should be most abundant in animal cell? [1]
(a) tRNA
(b) mRNA
(c) mzRNA
(d) rRNA
Answer:
(d) rRNA

(v) Screening test for AIDS is- [1]
(a) Western blot
(b) ELISA
(c) PCR
(d) Southern blot
Answer:
(b) ELISA

(vi) Disease associated with secretion of toxin is- [1]
(a) TB
(b) AIDS
(c) tetanus
(d) food poisoning
Answer:
(d) food poisoning

(vii) Sonalika and Kalyan sona are varieties of: [1]
(a) wheat
(b) rice
(c) millet
(d) tobacco
Answer:
(a) wheat

(viii) Which one is known as ‘molecular scissor’ ? [1]
(a) Ligase
(b) Electrophoresis
(c) Restriction enzymes
(d) Cloning
Answer:
(c) Restriction enzymes

(ix) First transgenic crop was: [1]
(a) cotton
(b) rice
(c) tobacco
(d) pea
Answer:
(c) tobacco

Question 2.
Fill in the blanks. (1 × 4 = 4)
(i) ……………… are the birds grown for providing meat. [1]
(ii) Exotic species have a large impact, especially in ……………… ecosystem. [1]
(iii) ……………… is initiator codon. [1]
(iv) In aquatic ecosystem, the limiting factor for the productivity is ……………… [1]
Answer:
(i) Broilers
(ii) Island
(iii) AUG
(iv) presence of its alternative allele and sunlight.

Question 3.
Give the answers of the following questions in one word or one line. (1 × 8 = 8)
(i) Define recessive factor. [1]
Answer:
The factor or allele of a character fails to express its effect in the presence of its alternative allele and express itself only in the homozygous cached the recessive factor.

(ii) What are pleiotropic genes? [1]
Answer:
A single gene that governs multiple phenotypic effects is called a pleiotropic gene.

(iii) Name protozoan diseases and their causal organisms. [1]
Answer:
(i) Malaria – Plasmodium vivax
(ii) Kala-azar – Leishmania donovarti.

(iv) What is hybrid? [1]
Answer:
Offspring produced by crossing the parents with different characters is called hybrid.

(v) What is genetic engineering? [1]
Answer:
In this process several techniques done with the genetic material (DNA, RNA) to alter its original chemical structure into desired structure.

(vi) What are agrochemicals? [1]
Answer:
It includes insecticides, herbicides, fungicides and nematicides.

(vii) Why are nutrient cycles in nature called biogeochemical cycles? [1]
Answer:
Because in an ecosystem nutrients are obtained from the soil and circulate among living forms and are again returned to soil.

(viii) Where was the World summit on sustainable development held in 2002? [1]
Answer:
Johannesburg.

Section – B

(1.5 Marks)

Question 4.
Removal of gonads cannot be considered as a contraceptive option. Why? [1.5]
Answer:
Removal of gonads not only stops the production of gametes but will also stop the secretions of various important hormones which are important for body functions. This method is irreversible and therefore cannot be considered as a contraceptive method.

Question 5.
Amniocentesis for sex determination is banned in our country. Is this ban necessary? Comment. [1.5]
Answer:
Amniocentesis is very useful technique as it is used to determine the sex of the foetus as well as its congenital diseases. But unfortunately this useful technique is being misused to kill the normal female foetus because it helps to detect the sex of the foetus. It is called foeticide which is a crime therefore, it is necessary to legally ban the determination of sex of foetus.

Question 6.
How artificial insemination method of animal breeding are best? [1.5]
Answer:
Artificial insemination method of animal breeding is the best because it is economical and has a number of advantages :

• Upto 300 cows from distance places can be inseminated by semen of a single bull.
• It ensures progeny of good quality.
• It avoids transportation of animals.

Question 7.
What is apiculture? How is it important in our lives? [1.5]
Answer:
Mass rearing of honey bees in the artificial hives for the production of honey at commercial level is called apiculture.
Apiculture is very important in our lives because it produces products of high economic and nutritive value :

• The main product of beekeeping is honey which is highly nutritious.
• Honey is used as a part of deshi medicines.
• Honey wax is used in cosmetics and polish industry.

Question 8.
From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know? [1.5]
Answer:
DNA is made up of nucleotides on which genes are arranged in sequences in human genome 20,000 to 24000 genes can be located. By the process of gene expression these genes produce proteins and can modified into enzymes. So enzymes are gene product smaller than DNA because a single DNA gene can encodes several enzymes. Small portion of DNA transcript into m-RNA there nucleotide of m-RNA together form a single codon, these codons polymerize to form specific polypeptide chain that modified into enzyme (protein).

Question 9.
What would be the molar concentration of human DNA in a human cell? [1.5]
Answer:
Human genome has 23 pairs of chromosomes. Normal weight of a single pair of DNA = 650 daltons.
1 dalton = 1.66 × 10²⁴ g.
Human genome in total has 3.3 × 10⁹ pairs.
So, the total genome = 3.3 × 10⁹ × 650 = 2.15 × 10¹² daltons.
All can also define the concentration of DNA in human cell is 2 mg/mL of cell extract.

Question 10.
Name the soil bacterium that produces a protein/chemical that is toxic to insect pest. Show with example that these are encoded by different forms of the gene. [1.5]
Answer:
Bt cotton is genetically modified plant contain a gene ‘cry gene’ of Bacillus thuringiensis (Bt), which control lepidopteran insects by producing toxic protein, e.g., Cry IAc and Cry IIAb kill cotton bollworms. Cry genes inserted into cotton plant through DNA technology. Bacterial gene get cloned inside the cotton plant (Bt cotton plant) to produced large quantity of protoxin in plant cell. When insects feed on plant protein get activated in insect gut and kill the insects.

Question 11.
How does ‘RNA interference’ takes place in eukaryotes? Mention its importance. [1.5]
Answer:
To control the infection of Meloidbgyne incognita, a novel strategy has been used which is known as RNA interference.
It is a biological process in all eukaryotic organism, where RNA molecule silences a gene by inhibiting a gene translation due to the presence of complementary dsRNA. Which prevents translation of the mRNA by forming dsRNA.

RNAi used to produce pest resistant plants specially for nematodes or cotton root knot nematode.

Question 12.
What is energy pyramid? Illustrate with diagram. [1.5]
Answer:
Pyramid of energy : Energy pyramid is a graphical representation indicating flow of energy at each trophic level in an ecosystem. Pyramid of energy is always upright. It cannot be inverted, because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step. In the energy pyramid, each bar shows the amount of energy7 present at each trophic level in a given time or annually per unit area.

An ideal pyramid of energy. Observe that primary producers convert only 1% of the energy in the sunlight available to them into NPP

Question 13.
Differentiate between primary productivity and secondary productivity. [1.5]
Answer:
Differences between Primary and Secondary Productivity

Primary productivity	Secondary productivity
It is the amount of organic matter generated by producers per unit area over a specific span of time.	It is the rate of generating organic matter by consumers over a span of time.

Question 14.
What are sacred groves? What is their role in conservation? [1.5]
Answer:
Sacred groves are referred to the tracts of forests that are restored in the places of worship. These are found to be in Western Ghats of Karnataka, Raiasthan, Maharashtra, Madhya Pradesh and Meghalaya. These groves help in safeguarding threatened, rare and endemic species of animals and plants present in a region. The act of deforestation is sternly banned in tribal regions. Thus, sacred groves are a rich region.

Question 15.
(a) Write the full form of the following: [1.5]
(i) UNEP (ii) WWF (iii) IUCN (b) In situ conservation is done in which areas?
Answer:
(i) UNEP = United Nations Environment Programme.
(ii) WWF = World wildlife fund.
(iii) IUCN = International Union for Conservation at Nature and Natural Resources.
(b) In situ conservation can be done in following areas :

Section – C

(3 Marks)

Question 16.
Differentiate between a zoospore and a zygote. [3]
Or
What is fertilization? Mention the post fertilization events (charges) in a flower. [3]
Answer:
Differences between Zoospores and Zygote

	Zoospores	Zygote
1.	These   are endogenously, asexually produced, unicellular, naked and motile spores having one or two flagella.	Zygote is a diploid cell formed by fusion of male and female gametes.
2.	It may be haploid or diploid.	It is always diploid.
3.	Zoospores take part in dispersal.	Zygote does not          have significant role in dispersal.

Question 17.
How is sex determined in human beings? [3]
Or
Mention the contribution at T.H. Morgan in genetics. [3]
Answer:
Human beings show XY type of sex determination. In human, sex chromosomes in male are XY while those of female are XX. The male can produce gametes (sperms) containing either X or Y sex-chromosome whereas, female can produce gametes (ovum) containing only X-chromosome. When Y chromosome containing gamete of male fertilizes with either X containing gamete of female, foetus will be a male. When X chromosome containing gamete of male fertilizes with either of female gamete, foetus will be a female.

Question 18.
Under polio prevention programme, infants in India were given polio vaccines on a large scale at regular intervals to eradicate polio from the country.
(i) What is vaccine ? Explain, how does it impart immunity to the child against the disease.
(ii) With the help of one example each differentiate between active and passive immunity. [3]
Or
The following are some well-known abbreviations, which have been used in chapter.
Expand each one to its full form :
(a) MALT (b) CMI (c) AIDS (d) NACO (e) HIV. [3]
Answer:
(i) Vaccine is a preparation of inactivated or weakened pathogen of polio virus protein that is injected into a person to provide protection against disease.
During vaccination for a particular disease, an antigen or antigenic protein or weak pathogen which is in inactive form is introduced into the body to induce mild immune response. The vaccine generate antibodies that neutralises the toxin/pathogen and produce memory, B- lymphocytes (B-cells) or T-lymphocytes (T-cells) which recognise the pathogen in the subsequent encounters and produce antibodies.

(ii) Differences between Active and Passive Immunity

	Active Immunity	Passive Immunity
1.	It is slow and provides relief only after long period.	It provides immediate relief.
2.	It is long lasting.	It is short lived.
3.	It has no side effect.	It may cause reaction.
4.	It is developed by an individual’s own cells in response to an infection or a vaccine.	It is developed when ready made antibodies are inoculated from outside.

Section – D

(4 Marks)

Question 19.
(a) Draw a well labelled diagram of mature embryosac. [4]
(b) Write the main functions of the following :
(i) Egg (ii) Secondary nucleus.
Or
Define self pollination and cross pollination. Write two adaptations for cross pollination. [4]
Answer:

Fig. : Structure of Mature Embryo Sac

Functions:

• Egg : It gives rise zygote after fertilization, which in turn produces embryo.
• Secondary nucleus : It gives rise primary endosperm nucleus after fusion with male gamete which in turn develops endosperm.

Question 20.
Write down the components of nucleic acids. [4]
Or
How polynucleotide chain is formed, explain in brief. Give main points of Chargaffs rule. [4]
Answer:
Nucleic acids are polymers of nucleotides. Each nucleotide monomer consists of three different molecules.
1. Nitrogenous base.
2. Deoxyribose : Pentose Sugar.
3. Phosphoric acid : PO₄.

I. Nitrogeneous Base
Fischer (1880) first of all discovered nitrogenous bases. They are heterocyclic, nitrogen containing organic ring compounds. There are two main types of nitrogenous bases : Purines and Pyrimidines.
1. Purines : These are double-ringed compounds, in which 5C imidazole ring attached to 4′ and 5′ places of a 6C carbon pyrimidine ring. There are two types of purines found in both DNA and RNA nucleotides :
(a) Adenine : Represented by A is 6-aminopurine.
(b) Guanine : Represented by G is 2-amino, 6-oxypurine.

2. Pyrimidines : These are single-ringed bases, in which nitrogen is present at 1′ and 3′ position in 6C benzene ring. There are three pyrimidines :
(a) Cytosine : Represented by C and present in both DNA and RNA.
(b) Thymine : Represented by T and present only in DNA.
(c) Uracil : Represented by U and present only in RNA.

II. Sugar : It is a five carbon (pentose) sugar. There are two types of pentose sugars : ribose and deoxyribose. Deoxyribose sugar has one oxygen atom less at second carbon. Ribose sugar is present in RNA while deoxyribose sugar occurs in DNA.