CBSE Sample Papers for Class 12 Biology Paper 5 are part of CBSE Sample Papers for Class 12 Biology. Here we have given CBSE Sample Papers for Class 12 Biology Paper 5.
CBSE Sample Papers for Class 12 Biology Paper 5
Board | CBSE |
Class | XII |
Subject | Biology |
Sample Paper Set | Paper 5 |
Category | CBSE Sample Papers |
Students who are going to appear for CBSE Class 12 Examinations are advised to practice the CBSE sample papers given here which is designed as per the latest Syllabus and marking scheme as prescribed by the CBSE is given here. Paper 5 of Solved CBSE Sample Paper for Class 12 Biology is given below with free PDF download solutions.
Time: 3 Hours
Maximum Marks: 100
General Instructions:
- There are total 26 questions and five sections in the question paper. All questions are compulsory.
- Section A contains question number 1 to 5, Very Short Answer Type Questions of one mark each.
- Section B contains question number 6 to 10, Short Answer Type Questions of two marks each.
- Section C contains question number 11 to 22, Short Answer Type Questions of three marks each.
- Section D contains question number 23, Value Based Question of four mark.
- Section E contains question number 24 to 26, Long Answer Type Questions of five marks each.
- There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examiner is to attempt any one of the question out of the two given in the question paper with the same question number.
- No. of printed pages are three.
SECTION-A
Question 1.
DNA as a known polymer of nucleotides being linked to each other by 3′-5′ phosphodiester bond. Suggest the modifications that would prevent polymerization of nucleotides.
Question 2.
State the property of retroviruses with an example.
Question 3.
Define reproductive health.
Question 4.
Follicular phase is considered to be the longest phase of complete menstrual cycle. Discuss the changes that takes place during this phase.
Question 5.
It is often seen that a well growing herbaceous plant dies if it is transplanted outside from its native forest. Give reason.
SECTION-B
Question 6.
Human females experience two major changes in their lifetime, i.e. menarche and menopause. State the significance behind these two events.
OR
(1) State, the principle of independent assortment.
(2) How would the following affect the phenomenon of independent assortment?
(a) Crossing Over
(b) Linkage
Question 7.
Name the organs which comprise the male reproductive system.
Question 8.
Differentiate between the two different types of interactions found among organism in a community with an example of each.
Question 9.
Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
Question 10.
Write down the preventive measures to control the spread of common cold.
SECTION-C
Question 11.
Zygote tends to pass through several developmental stages till the stage of an implantation. Discuss each stage briefly in a flowchart form.
Question 12.
(1) Draw the diagram of a bacteriophage.
(2) Expand LAB. How does it work?
Question 13.
The crop varieties in India can be made disease resistant to overcome the food crisis. Justify the statement.
Question 14.
How does the rate of decomposition of detritus is affected by the abiotic factors like availability of oxygen and chemical composition of detritus?
OR
Discuss the condition of an ecosystem in the following situations
(1) if all producers will decrease in the number.
(2) if all organisms of one trophic level will be eliminated or killed.
(3) if all top carnivores population is removed
Question 15.
Mention the source of gonadotropins in human females. Explain the changes brought about in the ovary by these hormones during menstrual cycle.
Question 16.
1. Which contraceptive pill has been developed by CDRI, Lucknow?
2. State its contraceptive action.
3. Why it has been preferred over other pills?
Question 17.
DNA replication occur in small replication fork and not in its entire length.
- Why is DNA replication continuous and discontinuous in a replication fork?
- Explain the importance of ‘origin of replication’ in a replication fork.
Question 18.
Dominance, co-dominance and incomplete dominance patterns of inheritance are different from each other. Discuss.
Question 19.
Identify the steps represented in the following process.
Question 20.
Explain the following given below.
(1) The role of Y-chromosome in human sex determination.
(2) Suppose a foetus has X and Y-chromosomes, but lacks receptors for the protein encoded by the SRY gene. Will the foetus develop as a male or as a female?
Question 21.
Out of in situ or ex situ conservation, which type of conservation measures helps the large number of species to survive? Explain in detail.
Question 22.
Agrobacterium tumefaciens is known to be the natural method of gene transfer. Justify in support of the statement.
SECTION-D
Question 23.
Rita’s sister when gave birth to a child was advised by the Doctor to breast feed her child during the initial periods for upto 6 months. As breast feeding is beneficial for both. But, she denies to do so as she feels that her figure will be spoiled. As a biology student, how will you moralise her sister. Also give the advantages related to this.
SECTION-E
Question 24.
(1) Explain the structure of DNA.
(2) Draw the diagram of its double helical model.
OR
Draw the labelled schematic structure of a transcription unit. Explain the function of each component of the unit in the process of transcription.
Question 25.
Diagrammatically explain the experimental setup in cloning and’ expressing a human gene into a bacterium coli.
OR
Highlight five areas, where biotechnology has influenced our lives.
Question 26.
(1) Mention any two significant roles that predation plays in nature.
(2) Explain hydrarch succession.
OR
(1) Draw a pyramid of numbers’ of a situation, where a large population of insects feed upon a very big tree. The insects in turn are eaten by small birds, which in turn are fed upon by big birds.
(2) Differentiate between the pyramid of biomass of the above situation and the pyramid of numbers that you have drawn.
Answers
SECTION-A
Answer 1.
Removal or replacement the 3-OH group in deoxyribose can present the polymerization of nucleotides in a DNA
Answer 2.
Retrovirus is a virus which has RNA as its genetic material. HIV is a member of this group.
Answer 3.
Reproductive health includes avoidance of any reproduction related problems like pregnancy, delivery, STDs, abortions, contraception, menstrual problems, infertility, etc.
Answer 4.
Follicular phase of menstrual cycle lasts for the complete 14 days. During this phase, the primary follicles in the ovary grows to become a fully mature Graafian follicle and simultaneously the endometrium layer of the uterus gets regenerated through proliferation.
Answer 5.
Herbaceous plant tends to die if transplanted from its native place due to the change in its microclimate.
SECTION-B
Answer 6.
Menarche and menopause defines the reproductive cycle of adolescent female. Both terms are related to common term known as menstruation or cyclical monthly bleeding. Menarche is the name given to first menstrual period that usually occurs between the ages of 11-16 at reaching puberty. While, menopause is the name given to the point of time when the flow periods stops permanently. It usually occurs at an age of around 50 years.
OR
(1) According to the principle of independent assortment, the two factors of each character assort or separate out independently of the factors of other characters, at the time of gamete formation and get randomly rearranged in the offsprings producing both parental and new combination of characters.
(2)
(a) Crossing over influences linked genes as a result of which 50% recombination is obtained in the test cross progeny.
(b) It influences recombination which is less than 50%.
Answer 7.
Male reproductive system consists of: testes, vasa efferentia, epididymis, vas deferens, seminal vesicle, prostate gland, cowper’s gland and penis
Answer 8.
Mutualism | Commensalism |
In this relationship both the species involved are benefited. | In this relationship only one specie is benefited and the other is neither benefited nor harmed. |
Example Sea anemone and hemit crab. | Example Sucker fish and shark. |
Answer 9.
According to a recent study on fossils, a small terrestrial dinosaur with feathers covering on the limbs and body was discovered. This search established that feathers evolved earlier than wing and may be functional as thermoregulator to face adverse conditions. These newly developed feathers earlier helped in gliding and then flying.
Answer 10.
Some preventive measures to control the spread of common cold are:
- Covering the mouth and nose while sneezing.
- Not sharing utensils, towels, handkerchiefs or food, etc.
- Washing hands regularly after sneezing, coughing,-blowing nose, etc.
- Washing hands after touching surfaces like door handles, etc.
SECTION-C
Answer 11.
The mitotic division starts as the zygote which is formed by the fusion of holoid nucleus of the sperm and that of ovum moves through the isthmus of the oviduct.
↓
This is known as cleavage towards the uterus and thus forming 2, 4, 8, 16 daughters cells called blastomeres.
↓
The morula thus continues to divide and transforms into blastocyst as it moves further into the uterus.
↓
The blastomeres in the blastocyst are found arranged in an outer layer called trophoblast and to the inner group of cells attached to the trophoblast called inner cell mass.
↓
This trophoblast layer then gets attached to an endometrium and the inner cell mass differentiates to form an embryo.
↓
After attachment, the uterine cell divides rapidly and cover the blastocyst.
↓
As a result of which, the blastocyst becomes embedded in the endometrium undergoing in the plantation of an embryo which finally leads in a phase of pregnancy.
Answer 12.
(1)
(2) LAB stands for Lactic Acid Bacteria. This bacteria grows in milk and convert it into curd.During its growth, LAB produces acid which coagulate and digest the milk protein partially and increases the nutritional quality by increasing Vitamin Bir
Answer 13.
The conventional methods of breeding for disease resistance are hybridization and selection.
Steps
- Selection and screen germplasm for the resistance source (selecting a plant which is disease resistant).
- Hybridisation of selected parents (plants is crossed or mated with plant having disease resistance).
- Selection and evaluation of hybrids (offspring from the above cross are selected and evaluated for desirable traits).
- Testing and release of new varieties (after all the evaluation, testing is done and hybrid varieties are crossed).
Answer 14.
Rate of decomposition of detritus is affected by the abiotic factors in the respective ways.
- The rate of decomposition in the anaerobic condition decrease while increase in aerobic condition.
- Detritus rich in lignin and chitin has slower rate of decomposition, while, a detritus rich in nitrogen and water soluble substances such as sugar has a quicker rate of decomposition.
- The rate of decomposition is high in warm and moist environment. While it is slower in the low temperature.
OR
(1) If the producers eventually decreases in number due to any circumstance, the whole pyramid of energy would get affected because producers make the base of the pyramid. Also due to this, there will be more competition among the consumers for food and other resources and the consumers will eventually have to move to a new area to fulfill their needs.
(2) If all the organisms of one trophic level is killed, the number of individuals in the next trophic level will decrease due to unavailability of the food, thereby, increasing the number of individuals in the lower trophic level because no one will be present to feed upon them. This will in turn cause an imbalance in the complete ecosystem.
(3) If all the top carnivores or predators are removed, the world will have a devastating effect on the ecosystem from which it derives. Also there occurs a behavioural changes in the prey species due to which, they get degraded quickly and over run its habitat.
Answer 15.
Gonadotropins (LH and FSH) are secreted by the anterior lobe of pituitary gland,
- Gonadotropins (LH and FSH) gradually increases during the follicular phase (proliferative phase) or menstrual cycle and stimulates follicular development as well as secretion of estrogen by the growing follicles.
- LH and FSH attain a peak level in the middle of the cycle (about 14th day) and rapid secretion of LH induces rupture of Graafian follicle followed by ovulation (release of ovum).
- LH stimulates the transformation of Graafian follicle into corpus luteum.
Answer 16.
- ‘Sahcli’ has been developed by the CDRI, Lucknow.
- It is an oral pill that inhibits ovulation and fertilization.
- It has been preferred over other pills as it is non-steroidal in nature and taken once a week.
Answer 17.
The two strands of DNA cannot be separated in its entire length. The replication occurs within a small opening of the helix called as replication fork.
(1) The DNA-dependent DNA polymerase catalyses polymerization only in one direction, that is 5 ’->3 ’ which creates some additional complications at the replicating fork. Consequently, on one strand (with polarity 3’-> 5’), the replication is continuous while on the other (the tefiiplate with polarity 5’->3’), it is discontinuous. These discontinuously synthesized fragments are later joined by the enzyme DNA ligase.
(2) Origin of replication is a sequence of DNA at which replication is initiated. It is because of the requirement of one that a piece of DNA if needed to be propagated during recombinant DNA procedure requires a vector.
Answer 18.
Differences between dominance, incomplete dominance and co-dominance are given below.
Dominance | Incomplete Dominance | Co-dominance |
It is a relationship between alleles of a single gene, in which one allele masks the phenotypic expression of another allele at the same gene locus. | It is also known as (partial or mosaic) dominance where none of the two contrasting alleles or factors is dominant, e.g. incomplete dominance in four ‘o’ clock plant. | It is the phenomenon of expression of both the alleles in a heterozygous state. In this, alleles do not show dominance- recessive relationship and are able to express themselves independently e.g. ABO blood group in humans. |
Answer 19.
‘A’ Collection of germplasm
‘B’ Cross hybridisation among selected plants.
‘C’ Selection and testing of superior recombinants.
Answer 20.
(1) The Y-chromosome acts as a switch for other sex-determining genes that activate in the embryo, so that the CRY gene develops as a male and dismantles all the female embryonic structures.
(2) The foetus will develop as a female without CRY protein receptors, the signal to develop as a male will never be received.
Answer 21.
In situ conservation helps in the survival of larger number of species. It is onsite conservation where species are conserved in their natural habitat. With the entire ecosystem, which include other organisms, biotic and abiotic component of the ecosystem associated with the target species.
Answer 22.
Agrobacterium tumefaciens is a pathogen of several dicot plants which has an ability to deliver a piece of DNA known as fDNA (transform normal plant cells into a tumour and direct these tumour cells to produce the chemicals required by the pathogen). Cloning vector has been produced by tumor inducing Ti plasmid of Agrobacterium tumefaciens.It is no more pathogenic to the plants and is still able to use the mechanisms to deliver genes of or interest into a variety of plants.
SECTION-D
Answer 23.
Breast milk contains antibodies (IgA) that helps the newborns to fight against viruses, bacteriaand other foreign agents that enters the body. It also lowers the body’s risk of having asthma, any sort of allergies, etc. Also, it is wrong to think that breast feeding spoils the mother’s figure because it is not related to any type of issue. In fact women often feel relaxed while breast feeding. Also it helps women to lower the risk of many diseases.
SECTION-E
Answer 24.
(1) DNA is a long polymer of deoxyribonucleotides. Double helical structure of DNA is the most accepted model. It was given by James Wastson and Francis Crick in 1953.
Salient features of DNA are
- It is made up of two polynucletotide chains, where the backbone is constituted by , sugarphosphate and the base pairs project inside.
- The two chains have anti-parallel polarity. It means that if one chain has polarity 5’→ 3’ the other has 3’→ 5’
- Base are paired through the hydrogen bond forming base pairs.
- The two chains are coiled in a right-handed fashion. The pitch of the helix is 3.4 nm and there are 10 bp in each turn. Consequently, the distance between a bp is 0.34 nm.
- Plane of one base pair stacks over the other in double helix which provides stability to the structure
(2)
Functions of components of transcription unit are:
- Promoter (DNA sequence) – Provides binding site for the RNA polymerase.
- Structural gene – Code for enzymes/proteins and transcribe the //77RNA for the same.
- Terminator (sequence of bases) – Defines the end of transcription process.
- DNA strand with 3’ – 5’ polarity – Acts as the template for transcription of mRNA.
- DNA strand with 3’ – 5’ polarity – Coding strand; it does not code for rRNA.
Answer 25.
The multiple identical copies of specific template DNA can be produced by DNA cloning. It can be carried out by the use of a vector to carry specific foreign DNA fragment into the host cell. The mechanism of cloning and transfer of a gene for human growth hormone into E. coli is diagrammatically represented below.
OR
Biotechnology has influenced our lives in the following ways:
- It has provided us with genetically modified crops of better quality and high nutrient value.
- It has made available better and safer recombinant vaccines.
- It has also helped to develop transgenic animals that can produce human proteins.
- It has enabled gene therapy for curing various genetic diseases.
- Environment pollution has also been taken care of with the help of genetically engineered microbes.
Answer 26.
(1) Predation plays following two important roles in nature:
(a) They keep the prey populations under control.
(b) And act as conduits for energy transfer across trophic levels.
(2) Process of hydrarch succession is as follows:
(a) Submerged Stage: The pioneer species in an aquatic habitat are phytoplanktons.
(b) Floating Stage: Floating plants begin to appear with the rise in shallowness of the pond. Later on free floating plants like Lemna, Azolla, Wolfia, grow profusely to cover the water surface.
(c) Marsh-Meadow Stage: As the free water is changed to swampy land, the water plants give way to swampy plants such as sedges and rushes.
(d) Woodland (climax) Stage: With time, many smaller species of trees invade the area and climax community appears.
OR
(2) In case of pyramid of number for first two steps, number increases, but after that it starts decreasing. Whereas, in pyramid of biomass there is no clear trend.
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